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   9255篇
  免费   14篇
  国内免费   45篇
航空   4518篇
航天技术   3298篇
综合类   39篇
航天   1459篇
  2021年   65篇
  2019年   63篇
  2018年   147篇
  2017年   92篇
  2016年   80篇
  2014年   180篇
  2013年   245篇
  2012年   226篇
  2011年   318篇
  2010年   216篇
  2009年   357篇
  2008年   436篇
  2007年   249篇
  2006年   233篇
  2005年   260篇
  2004年   232篇
  2003年   303篇
  2002年   192篇
  2001年   300篇
  2000年   191篇
  1999年   226篇
  1998年   272篇
  1997年   201篇
  1996年   260篇
  1995年   323篇
  1994年   303篇
  1993年   166篇
  1992年   221篇
  1991年   115篇
  1990年   97篇
  1989年   228篇
  1988年   88篇
  1987年   94篇
  1986年   107篇
  1985年   292篇
  1984年   236篇
  1983年   205篇
  1982年   221篇
  1981年   268篇
  1980年   95篇
  1979年   63篇
  1978年   78篇
  1977年   71篇
  1976年   58篇
  1975年   79篇
  1974年   64篇
  1973年   61篇
  1972年   68篇
  1971年   59篇
  1970年   64篇
排序方式: 共有9314条查询结果,搜索用时 922 毫秒
721.
In the paper, processes of high-energy electron beam interaction with plasma particles in a discharge channel of a stationary plasma thruster are analyzed and the results are presented.  相似文献   
722.
The results of designing the attitude control system of the first Russian nanosatellite TNS-0 no. 1 providing orientation of its longitudinal axis along the local geomagnetic field induction vector are presented. The system consists of a permanent magnet and two sets of hysteresis rods. The magnetic and geometric parameters of the magnet and rods are calculated. The influence of the permanent magnet field on the hysteresis rods and mutual influence of the rods in the case of compact satellite packaging are analyzed. Examples of calculations of transient processes and steady-state angular satellite motion are presented.  相似文献   
723.
724.
We consider the function, the problems being solved and the construction principles for a starting system of warning the critical regimes for a single-rotor helicopter at parking, taxiing and maneuvering on the ground, takeoff and landing as well as at descending and hovering regimes. The structural-functional scheme and the algorithms of system channel warning are presented.  相似文献   
725.
The Juno Waves Investigation   总被引:1,自引:0,他引:1  
Jupiter is the source of the strongest planetary radio emissions in the solar system. Variations in these emissions are symptomatic of the dynamics of Jupiter’s magnetosphere and some have been directly associated with Jupiter’s auroras. The strongest radio emissions are associated with Io’s interaction with Jupiter’s magnetic field. In addition, plasma waves are thought to play important roles in the acceleration of energetic particles in the magnetosphere, some of which impact Jupiter’s upper atmosphere generating the auroras. Since the exploration of Jupiter’s polar magnetosphere is a major objective of the Juno mission, it is appropriate that a radio and plasma wave investigation is included in Juno’s payload. This paper describes the Waves instrument and the science it is to pursue as part of the Juno mission.  相似文献   
726.
727.
Direct measurements of the geomagnetic field have been made for more than 400 years, beginning with individual determinations of the angle between geographic and magnetic North. This was followed by the start of continuous time series of full vector measurements at geomagnetic observatories and the beginning of geomagnetic repeat stations surveys in the 19th century. In the second half of the 20th century, true global coverage with geomagnetic field measurements was accomplished by magnetometer payloads on low-Earth-orbiting satellites. This article describes the procedures and instruments for magnetic field measurements on ground and in space and covers geomagnetic observatories, repeat stations, automatic observatories, satellites and historic observations. Special emphasis is laid on the global network of geomagnetic observatories.  相似文献   
728.
In this paper, a mathematical model of labor-intensity and a method of searching for optimal control of operating conditions in machining arbitrarily configurated parts with the use of CNC machines are considered. Also given is an example of the process optimization..  相似文献   
729.
The paper presents an improved technique and the results of strength analysis for the aircraft structural elements with a structural defect like an arbitrary shape delamination.  相似文献   
730.
The 20th century temperature anomaly record is reproduced using an energy balance model, with a diffusive deep ocean. The model takes into account all the standard radiative forcings, and in addition the possibility of a non-thermal solar component. The model is parameterized and then optimized to produce the most likely values for the climate parameters and radiative forcings which reproduce the 20th century global warming. We find that the best fit is obtained with a negligible net feedback. We also show that a non-thermal solar component is necessarily present, indicating that the total solar contribution to the 20th century global warming, of ΔTsolar = 0.27 ± 0.07 °C, is much larger than can be expected from variation in the total solar irradiance alone. However, we also find that the largest contribution to the 20th century warming comes from anthropogenic sources, with ΔTman = 0.42 ± 0.11 °C.  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