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   4477篇
  免费   8篇
  国内免费   6篇
航空   2090篇
航天技术   1605篇
综合类   16篇
航天   780篇
  2021年   44篇
  2019年   25篇
  2018年   104篇
  2017年   73篇
  2016年   76篇
  2015年   39篇
  2014年   130篇
  2013年   138篇
  2012年   143篇
  2011年   193篇
  2010年   127篇
  2009年   216篇
  2008年   293篇
  2007年   128篇
  2006年   107篇
  2005年   138篇
  2004年   117篇
  2003年   153篇
  2002年   89篇
  2001年   153篇
  2000年   74篇
  1999年   99篇
  1998年   120篇
  1997年   87篇
  1996年   90篇
  1995年   124篇
  1994年   121篇
  1993年   64篇
  1992年   95篇
  1991年   53篇
  1990年   36篇
  1989年   88篇
  1988年   40篇
  1987年   43篇
  1986年   37篇
  1985年   97篇
  1984年   86篇
  1983年   75篇
  1982年   86篇
  1981年   118篇
  1980年   41篇
  1979年   36篇
  1978年   32篇
  1977年   25篇
  1976年   28篇
  1975年   22篇
  1974年   22篇
  1973年   23篇
  1972年   23篇
  1971年   21篇
排序方式: 共有4491条查询结果,搜索用时 0 毫秒
511.
A statistical method for the on-board detection and compensation of adverse oscillations in pilot-aircraft systems is presented. A recursively updated linear model representing the pilot-aircraft system is used to continuously check for stability loss. The instability-related oscillations are detected early, using a statistical hypothesis test. Furthermore, a specially designed stability augmentation system assists the pilot during the instability periods. The method's effectiveness is demonstrated via data obtained from a flight simulator and a detailed simulation model.  相似文献   
512.
An exact solution of the Navier - Stokes equations is given that describes the vorticity of a viscous incompressible liquid or gas, dissipative mediums, stationary shear counter-current of continuous vortical medium in the absence of the Coriolis field.  相似文献   
513.
    
The SilEye experiment aims to study the cause and processes related to the anomalous Light Flashes (LF) perceived by astronauts in orbit and their relation with Cosmic Rays. These observations will be also useful in the study of the long duration manned space flight environment. Two PC-driven silicon detector telescopes have been built and placed aboard Space Station MIR. SilEye-1 was launched in 1995 and provided particles track and LF information; the data gathered indicate a linear dependence of FLF(Hz) ( 4 2) 10(3) 5.3 1.7 10(4) Fpart(Hz) if South Atlantic Anomaly fluxes are not included. Even though higher statistic is required, this is an indication that heavy ion interactions with the eye are the main LF cause. To improve quality and quantity of measurements, a second apparatus, SilEye-2, was placed on MIR in 1997, and started work from August 1998. This instrument provides energetic information, which allows nuclear identification in selected energy ranges; we present preliminary measurements of the radiation field inside MIR performed with SilEye-2 detector in June 1998.  相似文献   
514.
    
The scheme variants of implementing the thermal protection against heat flows being generated by the body of a high-temperature stationary gas turbine engine (GTE) are presented. The scheme of the experimental bench with a working section is given. Methodical approaches to the heat transfer calculation at different variants of forced and natural convection organization and under various operating conditions are described. The generalized results of the experiments carried out using a heat curtain being generated by porous injection are presented.  相似文献   
515.
An X, Y, Z Kalman tracking filter is described and its steady state characteristics are analytically determined when the radar sensor meaures range, bearing, and elevation (?, ?, ?) at uniform intervals of time, T seconds. The relationship between the quantities measured by the sensor (?, ?,?) and the Cartesian coordinate system (X, Y, Z) is explicitly considered.  相似文献   
516.
517.
    
The paper adduces the relators for algebraic operations on graphs using the numeric codes of the graphs. The special algebra of codes has been devised with consideration of the principles of graph transformation. This paper demonstrates the relevance of numeric coding of graphs for solving the problems of enumeration, systematization, and compact representation of the information about the structural and functional characteristics of the systems of flow distribution and conversion of rocket and space technology and for conducting the modeling transformations of given systems in the course of the structural and functional studies as well.  相似文献   
518.
  总被引:1,自引:0,他引:1  
The threshold values of the annual fluence of atomic oxygen (F AO ≈ 1020 cm?2), as well as the ratios of the energy-flux density of vacuum ultraviolet radiation of the solar spectrum to the flux density of atomic oxygen (Φ ν AO ≈ 8 × 10?15 mJ) were determined, which are characterized the influence of the synergistic effect on the mass loss of Kapton-H, PM-A, and PM-1E polyimide films, which are spacecraft materials.  相似文献   
519.
    
The use of charge-coupled devices is suggested as a means for detecting growth of micro-organism colonies. The accuracy of the method is determined by channel width and the sensitivity by the signal/noise ratio. The method was tested on a dense nutrient medium, which is to be considered more suitable to micro-organisms of the dry Martian soil than the water solution of nutrients employed in the Viking's strategy.  相似文献   
520.
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