4 719 ₽
3 999 ₽-15%
Турбовентиляторные двигатели General Electric для сверхзвуковых самолётовАльберт Гареев, Владимир Зрелов, Андрей Прокофьев
У книги пока нет отзывов — станьте первым
Как вам эта книга?
'%3e%3crect%20width='96'%20height='96'%20rx='48'%20fill='%2367BAC7'/%3e%3cpath%20fill-rule='evenodd'%20clip-rule='evenodd'%20d='M69.0248%2015.7004C77.6111%2013.268%2083.4022%2015.6371%2090.1762%2017.7073C96.9175%2019.7674%20104.874%2021.6396%20118.118%2018.5842C118.548%2018.485%20118.977%2018.7535%20119.077%2019.1838C119.176%2019.6143%20118.907%2020.0445%20118.477%2020.1438C104.877%2023.2813%2096.6236%2021.3508%2089.7084%2019.2375C82.8262%2017.1343%2077.5123%2014.9597%2069.4613%2017.2405C67.7008%2017.7392%2065.2477%2018.4875%2062.6176%2019.2414C62.976%2019.448%2063.3248%2019.667%2063.6605%2019.8996C65.7756%2021.3658%2067.4401%2023.3913%2067.9164%2026.0286C68.1039%2027.0674%2068.1767%2029.3795%2068.224%2031.5676C68.2727%2033.8167%2068.2943%2035.9795%2068.3607%2036.8596C68.3598%2036.847%2068.3619%2036.8854%2068.4086%2036.9905C68.4529%2037.0902%2068.5232%2037.2192%2068.6254%2037.3782C68.8306%2037.6971%2069.1296%2038.0851%2069.5023%2038.5305C70.2495%2039.4232%2071.2226%2040.4621%2072.1986%2041.5325C73.1591%2042.5858%2074.1238%2043.6714%2074.7953%2044.6096C75.1293%2045.0762%2075.4184%2045.5443%2075.5941%2045.9797C75.7551%2046.3788%2075.9028%2046.9503%2075.641%2047.4817C75.2684%2048.3435%2074.5979%2048.7862%2073.891%2049.008C73.2229%2049.2176%2072.4615%2049.2472%2071.8793%2049.2834C71.2272%2049.3241%2070.7843%2049.3739%2070.4818%2049.5159C70.3524%2049.5767%2070.2713%2049.6452%2070.2152%2049.7248C70.158%2049.8063%2070.0939%2049.9454%2070.0668%2050.1936C70.0446%2050.3975%2070.1472%2050.5508%2070.6976%2051.0559C70.916%2051.2562%2071.2319%2051.5437%2071.4457%2051.9006C71.687%2052.3034%2071.8043%2052.7993%2071.643%2053.3684C71.4713%2053.9734%2071.0764%2054.4236%2070.6615%2054.7473C70.4139%2054.9404%2070.142%2055.0984%2069.8734%2055.2317C70.1185%2055.3837%2070.3617%2055.5602%2070.5717%2055.7678C70.9273%2056.1196%2071.2608%2056.6284%2071.2455%2057.2805C71.2258%2058.1137%2070.7587%2058.6005%2070.3978%2058.9202C70.006%2059.2673%2069.8018%2059.4014%2069.6527%2059.6741C69.1917%2060.5178%2069.4112%2061.1655%2069.7201%2062.2034C69.8667%2062.6959%2070.0346%2063.299%2070.0111%2063.9602C69.9865%2064.6514%2069.7578%2065.3523%2069.2162%2066.0715C68.3976%2067.1584%2067.2724%2067.6058%2066.0844%2067.7268C64.9295%2067.8443%2063.6556%2067.6611%2062.4447%2067.4504C61.1939%2067.2328%2060.0036%2066.9852%2058.8637%2066.9016C57.731%2066.8186%2056.766%2066.9099%2055.9838%2067.2952C55.9439%2067.3149%2055.8348%2067.3948%2055.6771%2067.6184C55.5263%2067.8323%2055.3685%2068.1246%2055.2094%2068.4866C54.8913%2069.2103%2054.6054%2070.1256%2054.3646%2071.0442C54.1253%2071.9576%2053.9369%2072.8499%2053.808%2073.5149C53.7437%2073.8465%2053.6945%2074.1205%2053.6615%2074.3108C53.645%2074.4059%2053.6326%2074.4806%2053.6244%2074.5305C53.6203%2074.5553%2053.6166%2074.5747%2053.6146%2074.5871C53.6137%2074.593%2053.6131%2074.598%2053.6127%2074.6008C53.6124%2074.602%2053.6118%2074.6032%2053.6117%2074.6037L53.5951%2074.6848C53.5855%2074.7213%2053.5704%2074.7553%2053.556%2074.7893C53.5183%2075.083%2053.4212%2075.3743%2053.2211%2075.6213C52.935%2075.9744%2052.5401%2076.1169%2052.1722%2076.1409C51.5129%2076.1836%2050.7775%2075.8642%2050.1527%2075.4973C48.8456%2074.7295%2047.348%2073.3444%2046.4887%2072.0246C46.3823%2071.8611%2046.3399%2071.6651%2046.3676%2071.4739L46.3832%2071.3918L46.3842%2071.3889C46.3856%2071.3829%2046.3877%2071.3719%2046.391%2071.3567C46.3978%2071.3258%2046.4083%2071.2764%2046.4203%2071.2102C46.4444%2071.0773%2046.476%2070.877%2046.5004%2070.6233C46.5492%2070.1145%2046.5696%2069.3963%2046.4574%2068.5705C46.2342%2066.9282%2045.4868%2064.8615%2043.3568%2063.1311C42.5886%2062.5071%2040.7002%2061.3032%2038.1615%2059.7073C35.651%2058.1291%2032.5586%2056.1999%2029.4554%2054.1584C26.3536%2052.1179%2023.225%2049.954%2020.639%2047.9026C19.018%2046.6166%2017.5718%2045.3447%2016.4779%2044.1516C16.6211%2045.2201%2016.9334%2046.3364%2017.3763%2047.469C18.1432%2049.4295%2019.2775%2051.3854%2020.4955%2053.1438C21.7121%2054.9001%2022.9998%2056.4416%2024.059%2057.5705C24.5886%2058.135%2025.0554%2058.5904%2025.4222%2058.9153C25.606%2059.078%2025.7587%2059.2025%2025.8763%2059.2893C26.0078%2059.3862%2026.0531%2059.4044%2026.0336%2059.3967C26.2246%2059.4718%2026.5946%2059.5286%2027.141%2059.553C27.6639%2059.5763%2028.2541%2059.5678%2028.8412%2059.5588C29.4105%2059.5501%2029.9957%2059.5404%2030.4506%2059.5705C30.6743%2059.5854%2030.9142%2059.6128%2031.1234%2059.6711C31.2282%2059.7004%2031.3615%2059.7467%2031.4906%2059.8274C31.6036%2059.898%2031.7528%2060.0203%2031.8529%2060.2151L31.8929%2060.303C31.9757%2060.515%2031.9828%2060.7573%2031.892%2060.9856C31.8105%2061.1902%2031.674%2061.3238%2031.5746%2061.4026C31.3864%2061.5515%2031.1583%2061.6354%2030.9945%2061.6868C30.6414%2061.7975%2030.1713%2061.8784%2029.7211%2061.9446C29.489%2061.9787%2029.2474%2062.0108%2029.0121%2062.0422C28.7746%2062.074%2028.543%2062.1051%2028.3236%2062.137C28.1926%2062.1559%2028.0707%2062.177%2027.9584%2062.1955C28.017%2062.3032%2028.087%2062.4281%2028.1732%2062.5666C28.6331%2063.3057%2029.3829%2064.2934%2030.2474%2065.303C31.1098%2066.3099%2032.065%2067.3128%2032.9242%2068.0862C33.3543%2068.4733%2033.7494%2068.7931%2034.0883%2069.0246C34.4445%2069.268%2034.6745%2069.3685%2034.7845%2069.3928C35.6634%2069.5861%2036.9118%2069.4279%2038.1508%2069.2141C38.7323%2069.1137%2039.329%2068.999%2039.7943%2068.9358C40.0297%2068.9038%2040.2662%2068.8801%2040.4779%2068.8801C40.6333%2068.8802%2040.8861%2068.8898%2041.1273%2068.9953L41.2289%2069.0461C41.5879%2069.2508%2041.9426%2069.5388%2042.1049%2069.9602C42.2883%2070.437%2042.1523%2070.8766%2041.9467%2071.1887C41.7562%2071.4777%2041.4792%2071.7089%2041.222%2071.8889C40.9547%2072.076%2040.6489%2072.2486%2040.348%2072.4036C39.9769%2072.5946%2039.5335%2072.7978%2039.1595%2072.969C39.7311%2073.2549%2040.4652%2073.5915%2041.2592%2073.8684C42.1513%2074.1795%2043.0802%2074.4051%2043.9154%2074.4289C44.6467%2074.4498%2045.2418%2074.3148%2045.6898%2074.0129L45.8724%2073.8733L45.9574%2073.8098C46.1537%2073.6803%2046.3493%2073.6744%2046.4203%2073.675C46.5218%2073.676%2046.6044%2073.6949%2046.6478%2073.7063C46.7385%2073.7302%2046.8212%2073.7651%2046.8763%2073.7903C46.995%2073.8446%2047.1353%2073.9224%2047.2816%2074.008C47.5809%2074.1833%2047.9823%2074.439%2048.4418%2074.7463C49.3641%2075.3632%2050.5612%2076.212%2051.7357%2077.0969C52.907%2077.9794%2054.0733%2078.9113%2054.9262%2079.6926C55.3487%2080.0797%2055.7202%2080.4531%2055.9769%2080.7785C56.1029%2080.9382%2056.2284%2081.1204%2056.3129%2081.3108C56.383%2081.469%2056.5099%2081.8235%2056.3431%2082.2034C56.1764%2082.5827%2055.8594%2082.7899%2055.5805%2082.8987C55.3065%2083.0054%2055.0002%2083.047%2054.7074%2083.0598C54.1185%2083.0855%2053.3807%2083.0009%2052.5853%2082.8625C50.9826%2082.5836%2048.9405%2082.0483%2046.9574%2081.5168C44.9524%2080.9795%2043.0079%2080.4469%2041.5375%2080.1496C40.8997%2080.0207%2040.3898%2079.9469%2040.0219%2079.927C40.0754%2080%2040.1425%2080.0833%2040.2269%2080.1741C40.5861%2080.56%2041.1154%2080.9725%2041.7162%2081.4231C42.2871%2081.8513%2042.9336%2082.3218%2043.4135%2082.7727C43.6553%2083%2043.892%2083.2561%2044.0638%2083.5344C44.2341%2083.8104%2044.3865%2084.1844%2044.3295%2084.6125C44.2924%2084.8902%2044.1781%2085.2803%2043.7992%2085.5364C43.4595%2085.7658%2043.0697%2085.7711%2042.7924%2085.7483C42.2374%2085.7025%2041.3979%2085.4623%2040.2679%2085.1457C37.9273%2084.4899%2033.851%2083.3483%2026.7963%2082.0979C15.3454%2080.0683%201.03509%2080.8132%20-11.652%2086.9729C-12.0493%2087.1655%20-12.5274%2087%20-12.7203%2086.6028C-12.9131%2086.2054%20-12.7475%2085.7264%20-12.3502%2085.5334C0.702024%2079.1965%2015.3671%2078.4475%2027.0756%2080.5227C34.2006%2081.7856%2038.3315%2082.9422%2040.6996%2083.6057C41.5092%2083.8325%2042.065%2083.982%2042.4515%2084.0686C42.4116%2084.0277%2042.3665%2083.9846%2042.3178%2083.9387C41.9204%2083.5654%2041.3702%2083.1639%2040.7562%2082.7034C40.1719%2082.2651%2039.5268%2081.7709%2039.0551%2081.2639C38.6484%2080.8268%2038.1699%2080.1705%2038.266%2079.3967L38.2933%2079.2405L38.3441%2079.0744C38.4884%2078.7114%2038.7996%2078.5217%2039.0404%2078.4348C39.3037%2078.3398%2039.5981%2078.3174%2039.8607%2078.3186C40.399%2078.321%2041.0952%2078.4277%2041.8549%2078.5813C43.3874%2078.8912%2045.395%2079.4413%2047.3715%2079.9709C49.3699%2080.5065%2051.3407%2081.022%2052.8597%2081.2864C53.5145%2081.4003%2054.0489%2081.4564%2054.4476%2081.4602C54.2864%2081.2898%2054.0857%2081.0918%2053.8461%2080.8723C53.0488%2080.1419%2051.9289%2079.2462%2050.7728%2078.3752C49.6198%2077.5066%2048.4471%2076.675%2047.5521%2076.0764C47.1136%2075.7831%2046.7496%2075.5516%2046.4916%2075.3996C45.6971%2075.9011%2044.7669%2076.0532%2043.8695%2076.0276C42.8056%2075.9972%2041.7035%2075.7176%2040.7328%2075.3791C39.7556%2075.0384%2038.8716%2074.6246%2038.2357%2074.2981C37.917%2074.1344%2037.6578%2073.9909%2037.4769%2073.8879C37.3866%2073.8365%2037.3152%2073.795%2037.266%2073.7659C37.2415%2073.7513%2037.2218%2073.7398%2037.2084%2073.7317C37.2018%2073.7277%2037.1965%2073.7242%2037.1928%2073.7219C37.1909%2073.7208%2037.189%2073.7197%2037.1879%2073.719L37.1859%2073.717C37.0778%2073.6506%2036.9862%2073.5598%2036.9203%2073.4514C36.6951%2073.0804%2036.8061%2072.7091%2036.933%2072.5041C37.0395%2072.3322%2037.1847%2072.2154%2037.2728%2072.1506C37.4637%2072.0104%2037.7186%2071.8783%2037.9545%2071.7639C38.4981%2071.5002%2039.0368%2071.2786%2039.6156%2070.9807C39.886%2070.8415%2040.1204%2070.7069%2040.3041%2070.5784C40.3543%2070.5432%2040.3974%2070.511%2040.434%2070.4817C40.3322%2070.4846%2040.1923%2070.4959%2040.0092%2070.5207C39.5813%2070.5789%2039.0564%2070.681%2038.4232%2070.7903C37.2323%2070.9958%2035.6739%2071.2278%2034.4398%2070.9563C34.0217%2070.8642%2033.585%2070.6193%2033.1849%2070.3459C32.7672%2070.0605%2032.3149%2069.6906%2031.8539%2069.2756C30.9304%2068.4444%2029.9262%2067.3885%2029.0316%2066.344C28.1396%2065.3023%2027.3339%2064.2457%2026.8148%2063.4114C26.5618%2063.0047%2026.3441%2062.5997%2026.2357%2062.2522C26.1848%2062.0887%2026.1265%2061.8444%2026.1683%2061.5852C26.1912%2061.4436%2026.2488%2061.2737%2026.3744%2061.1174C26.3805%2061.1098%2026.3877%2061.1033%2026.3939%2061.0959C26.0542%2061.0558%2025.7236%2060.994%2025.4467%2060.885C25.2636%2060.8128%2025.0795%2060.6895%2024.9262%2060.5764C24.7582%2060.4525%2024.5675%2060.2958%2024.3617%2060.1135C23.9487%2059.7478%2023.4459%2059.2557%2022.892%2058.6653C21.7833%2057.4835%2020.4451%2055.8811%2019.1801%2054.0549C17.9166%2052.2309%2016.713%2050.1634%2015.8871%2048.052C15.0639%2045.9473%2014.594%2043.7429%2014.8676%2041.6692C14.9124%2041.3298%2015.1686%2041.0566%2015.5043%2040.9895C15.7978%2040.9309%2016.0957%2041.0411%2016.2806%2041.2678L16.3529%2041.3723C17.1747%2042.7895%2019.074%2044.6194%2021.6332%2046.6496C24.1643%2048.6575%2027.248%2050.7905%2030.3353%2052.8215C33.4212%2054.8516%2036.4961%2056.7705%2039.0131%2058.3528C41.5013%2059.917%2043.5013%2061.1869%2044.3656%2061.8889C46.8761%2063.9284%2047.7778%2066.4015%2048.0433%2068.3557C48.1754%2069.3278%2048.1511%2070.1724%2048.0931%2070.7766C48.0686%2071.0319%2048.0359%2071.2455%2048.0082%2071.4094C48.7489%2072.4356%2049.9418%2073.5174%2050.9633%2074.1174C51.4463%2074.4011%2051.7867%2074.5124%2051.973%2074.5373C51.974%2074.5205%2051.976%2074.5013%2051.976%2074.4797C51.976%2074.344%2052.013%2074.2178%2052.0726%2074.1057C52.0763%2074.0842%2052.0802%2074.0614%2052.0844%2074.0373C52.1189%2073.8381%2052.1702%2073.5536%2052.2367%2073.2102C52.3696%2072.5241%2052.5659%2071.5965%2052.8168%2070.6389C53.0663%2069.6868%2053.3772%2068.6789%2053.7445%2067.843C53.928%2067.4255%2054.1353%2067.0287%2054.3695%2066.6965C54.5966%2066.3746%2054.893%2066.0498%2055.2767%2065.8606C56.4301%2065.2924%2057.728%2065.2142%2058.9799%2065.3059C60.2243%2065.3971%2061.5422%2065.6685%2062.7191%2065.8733C63.936%2066.085%2065.0114%2066.2277%2065.9222%2066.135C66.7999%2066.0456%2067.4584%2065.7452%2067.9379%2065.1086C68.2938%2064.6359%2068.4002%2064.2483%2068.4125%2063.9036C68.4258%2063.529%2068.3325%2063.1488%2068.1869%2062.6594C67.9113%2061.7335%2067.4208%2060.4224%2068.2494%2058.9065C68.5723%2058.3159%2069.1045%2057.9272%2069.3363%2057.7219C69.5989%2057.4892%2069.6423%2057.3928%2069.6459%2057.2424C69.6469%2057.194%2069.6282%2057.0851%2069.4467%2056.9055C69.2643%2056.7252%2068.9885%2056.5464%2068.6625%2056.385C68.3439%2056.2273%2068.017%2056.1052%2067.766%2056.0217C67.6419%2055.9804%2067.5386%2055.9491%2067.4681%2055.9289C67.4334%2055.919%2067.4062%2055.9121%2067.389%2055.9075C67.3808%2055.9053%2067.3741%2055.9035%2067.3705%2055.9026C67.3694%2055.9023%2067.3681%2055.9017%2067.3676%2055.9016L67.2347%2055.8557C66.9386%2055.7226%2066.7471%2055.4188%2066.764%2055.0852C66.7812%2054.7516%2067.0028%2054.4687%2067.3109%2054.3664L67.4476%2054.3342H67.4496C67.4528%2054.3337%2067.4591%2054.3326%2067.4672%2054.3313C67.4835%2054.3286%2067.5095%2054.3238%2067.5433%2054.3176C67.6121%2054.3051%2067.7142%2054.2856%2067.8383%2054.2571C68.0891%2054.1994%2068.4231%2054.1084%2068.7631%2053.9768C69.1075%2053.8434%2069.4297%2053.6785%2069.6771%2053.4856C69.9242%2053.2929%2070.0544%2053.106%2070.1039%2052.9319C70.1285%2052.8449%2070.1198%2052.8016%2070.0726%2052.7229C69.9979%2052.5983%2069.8626%2052.4612%2069.6156%2052.2346C69.2352%2051.8857%2068.3505%2051.1731%2068.476%2050.0207C68.5264%2049.5582%2068.6656%2049.148%2068.9076%2048.8039C69.1508%2048.4584%2069.4667%2048.2248%2069.8012%2048.0676C70.4271%2047.7737%2071.1862%2047.7237%2071.7797%2047.6868C72.4429%2047.6455%2072.9727%2047.6192%2073.4115%2047.4817C73.7979%2047.3605%2074.0385%2047.1755%2074.183%2046.8254C74.1803%2046.797%2074.1683%2046.721%2074.1107%2046.5784C74.0051%2046.3165%2073.8006%2045.969%2073.4945%2045.5412C72.8858%2044.6908%2071.9836%2043.6706%2071.017%2042.6106C70.0659%2041.5676%2069.0509%2040.4842%2068.2748%2039.5569C67.886%2039.0924%2067.5381%2038.6451%2067.2797%2038.2434C67.0429%2037.8752%2066.7987%2037.4245%2066.765%2036.9807C66.6943%2036.0436%2066.6718%2033.7921%2066.6244%2031.6018C66.5757%2029.3504%2066.5006%2027.1959%2066.3412%2026.3127C65.9617%2024.2121%2064.6286%2022.5178%2062.7494%2021.2151C62.0123%2020.7041%2061.1983%2020.2586%2060.3402%2019.8791C58.928%2020.2654%2057.5074%2020.6362%2056.1517%2020.9495C53.8186%2021.4886%2051.6152%2021.8828%2049.9467%2021.9231C49.1212%2021.943%2048.3475%2021.8788%2047.7367%2021.6536C47.0998%2021.4185%2046.5197%2020.9502%2046.4115%2020.1467C46.2909%2019.2506%2046.6604%2018.5033%2047.2894%2017.9641C47.8867%2017.4523%2048.72%2017.118%2049.6351%2016.9114C51.4775%2016.4954%2053.9439%2016.5315%2056.4398%2017.012C57.7772%2017.2694%2059.1448%2017.6597%2060.4506%2018.1897C63.6819%2017.294%2066.8269%2016.3231%2069.0248%2015.7004ZM56.1381%2018.5832C53.7884%2018.1309%2051.5545%2018.1182%2049.9877%2018.4719C49.1987%2018.6501%2048.6496%2018.9055%2048.3304%2019.1789C48.0433%2019.4252%2047.9607%2019.6606%2047.9974%2019.9338C47.9994%2019.9513%2047.9931%2020.0428%2048.2904%2020.1526C48.6176%2020.2732%2049.1514%2020.3417%2049.9086%2020.3235C51.4058%2020.2873%2053.4766%2019.9257%2055.7914%2019.3909C56.403%2019.2495%2057.0272%2019.0959%2057.6576%2018.9358C57.1529%2018.7987%2056.6445%2018.6807%2056.1381%2018.5832Z'%20fill='white'/%3e%3c/g%3e%3cdefs%3e%3cclipPath%20id='clip0_1878_98326'%3e%3crect%20width='96'%20height='96'%20rx='48'%20fill='white'/%3e%3c/clipPath%3e%3c/defs%3e%3c/svg%3e)
Книги похожих авторов
2 713 ₽
2 299 ₽-15%
Теоретические основы лазерной обработкиАлександр Григорьянц, Александр Мисюров, Игорь Шиганов
3 185 ₽
2 699 ₽-15%
Нет в наличии
Оборудование для лазерной обработкиАлександр Григорьянц, Александр Мисюров, Игорь Шиганов
1 887 ₽
1 599 ₽-15%
Эффективность и качество сушки пиломатериалов: монографияАлександр Гороховский, Елена Шишкина
2 713 ₽
2 299 ₽-15%
Бесконтактные опоры высокоскоростных роторных систем. Эксплуатация и проектированиеАлександр Космынин, Алексей Смирнов, Владимир Щетинин
1 474 ₽
1 249 ₽-15%
Электрические машины и микромашины. ЗадачиВалерий Шишкин
2 123 ₽
1 799 ₽-15%
Электрические микромашины в вопросах и ответахВалерий Шишкин
2 005 ₽
1 699 ₽-15%
2 713 ₽
2 299 ₽-15%
3 185 ₽
2 699 ₽-15%
Контроллеры Аrduino в мобильных роботах и дронахВладимир Кангин, Егор Кангин
3 775 ₽
3 199 ₽-15%
Разработка SCADA-системВладимир Кангин, Михаил Кангин, Дмитрий Ямолдинов
Нет в наличии
Контроллеры Arduino, датчики, исполнительные устройства, средства коммуникации: Учебное пособиеВладимир Кангин, Егор Кангин
Нет в наличии
2 949 ₽
2 499 ₽-15%
Системы охлаждения камер сгорания и турбин двигателей летательных аппаратов и газотурбинных установокСергей Панченко, Сергей Толстов
2 713 ₽
2 299 ₽-15%
Защитные покрытия в авиадвигателестроенииСергей Балдаев, Татьяна Ильинкова
Только в магазинах
Родословные предания и легенды бурят.Сергей Балдаев
3 185 ₽
2 699 ₽-15%
Волновые зубчатые передачи. Схемы, расчет и конструкцииЮлия Бровкина, Алиса Пахомова, Ольга Чихаева
2 123 ₽
1 799 ₽-15%
Подшипники качения. Опоры и узлыАлександр Лукьянов, Ольга Чихаева
2 713 ₽
2 299 ₽-15%
Физико-химическая механика разрушения материалов. Охрупчивание, зарождение и развитие трещин: учебное пособиеСергей Думанский, Ольга Елагина, Ксения Наконечная