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   10571篇
  免费   807篇
  国内免费   803篇
航空   5735篇
航天技术   3479篇
综合类   577篇
航天   2390篇
  2022年   120篇
  2021年   198篇
  2020年   141篇
  2019年   121篇
  2018年   241篇
  2017年   230篇
  2016年   203篇
  2015年   213篇
  2014年   402篇
  2013年   435篇
  2012年   456篇
  2011年   593篇
  2010年   516篇
  2009年   579篇
  2008年   685篇
  2007年   418篇
  2006年   378篇
  2005年   360篇
  2004年   278篇
  2003年   324篇
  2002年   247篇
  2001年   325篇
  2000年   268篇
  1999年   318篇
  1998年   360篇
  1997年   280篇
  1996年   258篇
  1995年   279篇
  1994年   271篇
  1993年   189篇
  1992年   213篇
  1991年   140篇
  1990年   110篇
  1989年   178篇
  1988年   109篇
  1987年   99篇
  1986年   80篇
  1985年   190篇
  1984年   156篇
  1983年   145篇
  1982年   136篇
  1981年   204篇
  1980年   60篇
  1979年   60篇
  1978年   61篇
  1977年   44篇
  1976年   47篇
  1975年   55篇
  1972年   50篇
  1971年   42篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
We present results of numerical simulations of trajectories of a space probe with a flat solar sail which moves from a circular Earth orbit to near-Sun regions. We consider the upper limit of the sail temperature as the basic restriction. We also examine the planar (ecliptic) solar sail transfer with gravity-assist flybys around planets.  相似文献   
92.
The SOHO Solar EUV Monitor has been in operation since December 1995 onboard the SOHO spacecraft. This instrument is a highly stable transmission grating solar extreme ultraviolet spectrometer. It has made nearly continuous full disk solar irradiance measurements both within an 8 nm bandpass centered at 30.4 nm and throughout the 0.1 to 50 nm solar flux region since launch. The 30.4 nm flux, the 0.1 to 50 nm flux and the extracted soft X-ray (0.1 to 5 nm) flux are presented and compared with the behavior of solar proxies.  相似文献   
93.
The solar particle events (SPE) will contain a primary alpha particle component, representing a possible increase in the potential risk to astronauts during an SPE over the often studied proton component. We discuss the physical interactions of alpha particles important in describing the transport of these particles through spacecraft and body shielding. Models of light ion reactions are presented and their effects on energy and linear energy transfer (LET) spectra in shielding discussed. We present predictions of particle spectra, dose, and dose equivalent in organs of interest for SPE spectra typical of those occurring in recent solar cycles. The large events of solar cycle 19 are found to have substantial increase in biological risk from alpha particles, including a large increase in secondary neutron production from alpha particle breakup.  相似文献   
94.
95.
We consider a possibility to apply the method of analyzing the complex-shaped shells, proposed in [1], for determining the stress strain state of thin shells with a degenerating domain. The results of numerical calculations are presented.  相似文献   
96.
97.
We demonstrate that it is possible to express each component of the displacement vector for the interior point of the finite element (FE) through all components of nodal unknowns in curvilinear coordinates. The effectiveness of the valid technique of vector approximation for displacement fields has been verified on an example.  相似文献   
98.
The characteristics of the insulator wear process in the discharge chamber of a stationary plasma thruster (SPT) are analyzed. The results of studying the erosion resistance to ionic spraying of different ceramic compositions are presented. It is shown experimentally that the integral characteristics (the value of thrust and thrust efficiency) as well as the SPT lifetime can be improved in changing from the conventional hot-pressed boron silicate (BN + SiO2) ceramics to the BN + Si3N4 ceramic compositions.  相似文献   
99.
为了确定处理包头亚麻厂亚麻生产废水的设计方案,设计之前在现场进行了生产试验。在包头亚麻厂污水处理站,模拟炉渣滤床制造了3米高的炉渣滤层,滤渣从工厂锅炉房取用,将实际排放的亚麻煮漂车间、细纱车间、粗纱车间的生产废水混合后,通过炉渣滤层过滤处理,处理后出水由厂化验室和包头环保局化验。试验结果表明,处理后的排水各项指标完全达到国家排放标准。该工艺处理费用低,运行效果稳定,管理简便,具有明显的经济效益、环境效益和社会效益。  相似文献   
100.
Problems arising in introduction of gasodynamic seals in aircraft engines are considered. The operation of a face gasodynamic seal as part of a natural gas pump is analyzed and its efficiency in the presence of oil is shown.  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