首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2461篇
  免费   28篇
  国内免费   12篇
航空   979篇
航天技术   907篇
综合类   12篇
航天   603篇
  2022年   13篇
  2021年   27篇
  2019年   24篇
  2018年   73篇
  2017年   61篇
  2016年   49篇
  2015年   20篇
  2014年   78篇
  2013年   91篇
  2012年   71篇
  2011年   137篇
  2010年   102篇
  2009年   145篇
  2008年   148篇
  2007年   77篇
  2006年   63篇
  2005年   76篇
  2004年   78篇
  2003年   81篇
  2002年   56篇
  2001年   75篇
  2000年   39篇
  1999年   47篇
  1998年   52篇
  1997年   49篇
  1996年   41篇
  1995年   56篇
  1994年   34篇
  1993年   38篇
  1992年   50篇
  1991年   13篇
  1990年   16篇
  1989年   41篇
  1988年   19篇
  1987年   16篇
  1986年   13篇
  1985年   60篇
  1984年   51篇
  1983年   41篇
  1982年   41篇
  1981年   56篇
  1980年   34篇
  1979年   16篇
  1978年   17篇
  1977年   9篇
  1976年   16篇
  1975年   15篇
  1974年   12篇
  1971年   7篇
  1969年   7篇
排序方式: 共有2501条查询结果,搜索用时 15 毫秒
831.
A technique that allows simultaneous heating of the heat-exchange surface and estimation of its local temperature from the corresponding electrical resistance of the heating element is presented. The systematic error in measurements of the local heat transfer coefficient has been analyzed. A relation that takes possible heat loss into account and minimizes the measurement errors has been obtained.  相似文献   
832.
The design schemes of cooling for the nozzle blades of high-temperature gas turbines are considered. The results of the thermal and hydraulic tests for the cooling systems of the nozzle vanes are presented. The prospective cooling system of the nozzle vanes of low and high pressure turbines is developed and presented. The test results for the vane with proposed design are presented.  相似文献   
833.
Two types of uncertainty co-exist in the theory of evidence: discord and non-specificity. From 90s, many mathematical expressions have arisen to quantify these two parts in an evidence. An important aspect of each measure presented is the verification of a coherent set of properties. About non-specificity, so far only one measure verifies an important set of those properties. Very recently, a new measure of non-specificity based on belief intervals has been presented as an alternative measure that quantifies a similar set of properties (Yang et al., 2016). It is shown that the new measure really does not verify two of those important properties. Some errors have been found in their corresponding proofs in the original publication.  相似文献   
834.
The algorithms for achieving a practical increase in the rate of data transmission on the space-craft–ground tracking station line has been considered. This increase is achieved by applying spectral-effective modulation techniques, the technology of orthogonal frequency compression of signals using millimeterrange radio waves. The advantages and disadvantages of each of three algorithms have been revealed. A significant advantage of data transmission in the millimeter range has been indicated.  相似文献   
835.
836.
The problem of lateral motion stabilization is analytically solved for the fourth-order model of aircraft motion using the method of output signal control synthesis that is based on the control object decomposition. Numerical simulation data are presented.  相似文献   
837.
838.
Heliophysics is a new research field that explores the Sun–Solar System Connection; it requires the joint exploitation of solar, heliospheric, magnetospheric and ionospheric observations.  相似文献   
839.
The super-pressure balloon (SPB) has been expected to be a flight vehicle that can provide a long flight duration to science. Since 1997, we have developed the SPB. Now we are at the phase of developing an SPB of a practical size. In 2009, we carried out a test flight of a pumpkin-shaped SPB with a 60,000 m3 volume. The undesirable result of this flight aroused us to resolve the deployment instability of the pumpkin-shaped SPB, which has been known as one of the most challenging issues confronting SPB development. To explore this deployment issue, in 2010, we carried out a series of ground tests. From results of these tests, we found that an SPB design modified from pumpkin, named “tawara”, can be a good candidate to greatly improve the deployment stability of the lobed SPB.  相似文献   
840.
We explore the capabilities of the future space science mission IXO (International X-ray Observatory) for obtaining cosmological redshifts of distant Active Galactic Nuclei (AGNs) using the X-ray data only. We first find in which regions of the X-ray luminosity (LX) versus redshift (z) plane the weak but ubiquitous Fe Kα narrow emission line can deliver an accurate redshift (δz < 5%) as a function of exposure time, using a CCD-based Wide Field Imager (IXO/WFI) as the one baselined for IXO. Down to a 2–10 keV X-ray flux of 10−14 erg cm−2 s−1 IXO/WFI exposures of 100 ks, 300 ks and 1 Ms will deliver 20%, 40% and 60% of the redshifts. This means that in a typical 18′ × 18′ IXO/WFI field of view, 4, 10 and 25 redshifts will be obtained for free from the X-ray data alone, spanning a wide range up to z ∼ 2–3 and fairly sampling the real distribution. Measuring redshifts of fainter sources will indeed need spectroscopy at other wavebands.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号