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   19435篇
  免费   38篇
  国内免费   125篇
航空   10276篇
航天技术   5826篇
综合类   251篇
航天   3245篇
  2021年   155篇
  2018年   278篇
  2017年   157篇
  2016年   175篇
  2014年   434篇
  2013年   515篇
  2012年   444篇
  2011年   659篇
  2010年   482篇
  2009年   837篇
  2008年   864篇
  2007年   449篇
  2006年   440篇
  2005年   439篇
  2004年   487篇
  2003年   574篇
  2002年   506篇
  2001年   631篇
  2000年   376篇
  1999年   474篇
  1998年   480篇
  1997年   350篇
  1996年   433篇
  1995年   506篇
  1994年   512篇
  1993年   367篇
  1992年   369篇
  1991年   254篇
  1990年   247篇
  1989年   439篇
  1988年   215篇
  1987年   246篇
  1986年   250篇
  1985年   644篇
  1984年   530篇
  1983年   425篇
  1982年   492篇
  1981年   624篇
  1980年   247篇
  1979年   194篇
  1978年   189篇
  1977年   146篇
  1976年   156篇
  1975年   199篇
  1974年   181篇
  1973年   161篇
  1972年   188篇
  1971年   148篇
  1970年   143篇
  1969年   147篇
排序方式: 共有10000条查询结果,搜索用时 984 毫秒
901.
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   
902.
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   
903.
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   
904.
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   
905.
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   
906.
907.
908.
909.
910.
Dynamics and de-spin control of massive target by single tethered space tug   总被引:1,自引:0,他引:1  
This paper investigates the dynamics and de-spin control of a massive target by a single tethered space tug in the post-capture phase. The dynamic model of the tethered system is derived and simplified to a dimensionless form. Further, a decoupled PD controller is proposed, and the local stability of the controller is analyzed by linearization technique. Parametric studies of the dynamics and de-spin control of a massive target are conducted to characterize the dynamic process of de-spin with the proposed control law. It is shown that the massive target can be de-span by a single and small space tug with limited thrust within finite time. The thrust tangent with the tether de-spins the target while the thrust normal to the tether prevents the tether from winding up the target. The tether length has a positive contribution to the de-spin of a target. The longer tether leads to a faster de-spin process.  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