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   21511篇
  免费   668篇
  国内免费   597篇
航空   11998篇
航天技术   6134篇
综合类   655篇
航天   3989篇
  2021年   287篇
  2019年   219篇
  2018年   360篇
  2017年   248篇
  2016年   271篇
  2015年   227篇
  2014年   594篇
  2013年   659篇
  2012年   606篇
  2011年   837篇
  2010年   721篇
  2009年   1059篇
  2008年   1029篇
  2007年   603篇
  2006年   570篇
  2005年   550篇
  2004年   536篇
  2003年   618篇
  2002年   610篇
  2001年   684篇
  2000年   458篇
  1999年   560篇
  1998年   516篇
  1997年   403篇
  1996年   460篇
  1995年   532篇
  1994年   505篇
  1993年   399篇
  1992年   371篇
  1991年   280篇
  1990年   267篇
  1989年   426篇
  1988年   226篇
  1987年   247篇
  1986年   250篇
  1985年   643篇
  1984年   524篇
  1983年   410篇
  1982年   491篇
  1981年   621篇
  1980年   246篇
  1979年   189篇
  1978年   189篇
  1976年   156篇
  1975年   189篇
  1974年   181篇
  1973年   161篇
  1972年   188篇
  1971年   148篇
  1969年   147篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Numerous discoveries of asteroids unknown earlier led to a multiple increase in the number of information on small bodies of the Solar System. Huge volumes of information accumulated and obtained at observations of objects approaching the Earth’s orbit require storing and prompt processing, presenting more and more possibilities for studying distributions of small bodies of the Solar System and ways of their evolution. That is why development of information systems which will contain large volumes of data on small bodies of the Solar System and facilities for processing these data is actual and promising direction of activity.  相似文献   
992.
The Relativistic Proton Spectrometer (RPS) on the Radiation Belt Storm Probes spacecraft is a particle spectrometer designed to measure the flux, angular distribution, and energy spectrum of protons from ~60 MeV to ~2000 MeV. RPS will investigate decades-old questions about the inner Van Allen belt proton environment: a nearby region of space that is relatively unexplored because of the hazards of spacecraft operation there and the difficulties in obtaining accurate proton measurements in an intense penetrating background. RPS is designed to provide the accuracy needed to answer questions about the sources and losses of the inner belt protons and to obtain the measurements required for the next-generation models of trapped protons in the magnetosphere. In addition to detailed information for individual protons, RPS features count rates at a 1-second timescale, internal radiation dosimetry, and information about electrostatic discharge events on the RBSP spacecraft that together will provide new information about space environmental hazards in the Earth’s magnetosphere.  相似文献   
993.
This paper summarizes the modeling, simulation, and testing work related to the development of technology to investigate the potential that shape memory actuation has to provide mechanically simple and affordable solutions for delivering assets to a surface and for sample capture and possible return to Earth. We investigate the structural dynamics and controllability aspects of an adaptive beam carrying an end-effector which, by changing material equilibrium phases, is able to actively decouple the end-effector dynamics from the spacecraft dynamics during the surface contact phase. Asset delivery and sample capture and return are at the heart of several emerging potential missions to small bodies, such as asteroids and comets, and to the surface of large bodies, such as Titan.  相似文献   
994.
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   
995.
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   
996.
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   
997.
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   
998.
999.
1000.
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