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   8972篇
  免费   19篇
  国内免费   23篇
航空   4026篇
航天技术   3109篇
综合类   198篇
航天   1681篇
  2021年   85篇
  2019年   57篇
  2018年   183篇
  2017年   123篇
  2016年   123篇
  2015年   62篇
  2014年   214篇
  2013年   263篇
  2012年   260篇
  2011年   381篇
  2010年   271篇
  2009年   407篇
  2008年   459篇
  2007年   261篇
  2006年   200篇
  2005年   237篇
  2004年   231篇
  2003年   272篇
  2002年   279篇
  2001年   351篇
  2000年   155篇
  1999年   221篇
  1998年   246篇
  1997年   158篇
  1996年   241篇
  1995年   270篇
  1994年   251篇
  1993年   146篇
  1992年   193篇
  1991年   72篇
  1990年   71篇
  1989年   179篇
  1988年   79篇
  1987年   74篇
  1986年   87篇
  1985年   252篇
  1984年   208篇
  1983年   150篇
  1982年   175篇
  1981年   273篇
  1980年   68篇
  1979年   57篇
  1978年   65篇
  1977年   55篇
  1975年   64篇
  1974年   60篇
  1972年   49篇
  1971年   52篇
  1970年   49篇
  1969年   47篇
排序方式: 共有9014条查询结果,搜索用时 125 毫秒
421.
A concept of monitoring for material properties with residual life estimation of rotor blades for gas turbine engines is proposed. The structure of on-board control and conditionmonitoring system based on the intelligent pyrometer module with the algorithm for calculating the residual life of turbine rotor blades is described.  相似文献   
422.
This paper presents a composite model of a flight simulator. This simulator is intended for carrying out investigative tests of flight dynamics imitation models of a hingeless rotor helicopter. A schematic diagram, composition and operation channels of the flight simulator software are presented. A possibility of applying the control lag is estimated.  相似文献   
423.
This paper considers a beam with a technological longitudinal section on the level of the gravity center of the cross section that is loaded by a vertical concentrated force. We study the structure durability depending on the load amplitude and the initial crack length.  相似文献   
424.
Methods to control flow have been considered in order to reduce end losses in blade rows of GTE gas turbines by means of measures taken at the design stage.  相似文献   
425.
426.
427.
The role of bonding agents on the aging characteristics is one of the important research topics.Aging program of the prepared propellant samples was conducting as follows:Five samples,two free of bonding agents,and three containing an aziridine based bonding agents(MAPO,HX-752,MAT4),four samples based on different bonding and curing agents all were aged at 70 ℃.The prepared bonding agent "MAT4" gave remarkable improvements and resulted in highly stable mechanical properties comparing with HX-752 or MAPO.The selected bonding agents family inhibited the rate of decomposition of the propellants during the aging periods and supported the propellant matrix against decomposition at the elevated temperatures.   相似文献   
428.
The Plasma and Suprathermal Ion Composition (PLASTIC) investigation provides the in situ solar wind and low energy heliospheric ion measurements for the NASA Solar Terrestrial Relations Observatory Mission, which consists of two spacecraft (STEREO-A, STEREO-B). PLASTIC-A and PLASTIC-B are identical. Each PLASTIC is a time-of-flight/energy mass spectrometer designed to determine the elemental composition, ionic charge states, and bulk flow parameters of major solar wind ions in the mass range from hydrogen to iron. PLASTIC has nearly complete angular coverage in the ecliptic plane and an energy range from ~0.3 to 80 keV/e, from which the distribution functions of suprathermal ions, including those ions created in pick-up and local shock acceleration processes, are also provided.  相似文献   
429.
New Horizons: Anticipated Scientific Investigations at the Pluto System   总被引:1,自引:0,他引:1  
The New Horizons spacecraft will achieve a wide range of measurement objectives at the Pluto system, including color and panchromatic maps, 1.25–2.50 micron spectral images for studying surface compositions, and measurements of Pluto’s atmosphere (temperatures, composition, hazes, and the escape rate). Additional measurement objectives include topography, surface temperatures, and the solar wind interaction. The fulfillment of these measurement objectives will broaden our understanding of the Pluto system, such as the origin of the Pluto system, the processes operating on the surface, the volatile transport cycle, and the energetics and chemistry of the atmosphere. The mission, payload, and strawman observing sequences have been designed to achieve the NASA-specified measurement objectives and maximize the science return. The planned observations at the Pluto system will extend our knowledge of other objects formed by giant impact (such as the Earth–moon), other objects formed in the outer solar system (such as comets and other icy dwarf planets), other bodies with surfaces in vapor-pressure equilibrium (such as Triton and Mars), and other bodies with N2:CH4 atmospheres (such as Titan, Triton, and the early Earth).  相似文献   
430.
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