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   5269篇
  免费   5篇
  国内免费   10篇
航空   2467篇
航天技术   1644篇
综合类   12篇
航天   1161篇
  2021年   46篇
  2019年   24篇
  2018年   191篇
  2017年   159篇
  2016年   84篇
  2015年   43篇
  2014年   91篇
  2013年   133篇
  2012年   146篇
  2011年   277篇
  2010年   225篇
  2009年   293篇
  2008年   305篇
  2007年   230篇
  2006年   91篇
  2005年   161篇
  2004年   148篇
  2003年   141篇
  2002年   97篇
  2001年   143篇
  2000年   75篇
  1999年   98篇
  1998年   128篇
  1997年   82篇
  1996年   88篇
  1995年   121篇
  1994年   145篇
  1993年   76篇
  1992年   87篇
  1991年   34篇
  1990年   44篇
  1989年   79篇
  1988年   35篇
  1987年   34篇
  1986年   39篇
  1985年   144篇
  1984年   122篇
  1983年   98篇
  1982年   84篇
  1981年   169篇
  1980年   34篇
  1979年   36篇
  1978年   41篇
  1977年   35篇
  1976年   32篇
  1975年   39篇
  1974年   34篇
  1973年   32篇
  1972年   49篇
  1970年   24篇
排序方式: 共有5284条查询结果,搜索用时 379 毫秒
231.
232.
233.
A method of determining the maximum permissible values for diagnostic signs, being an integral part of health and usage monitoring systems (HUMS) of the helicopter transmission units, has been developed based on a probabilistic approach.  相似文献   
234.
Indian Space Research Organization (ISRO) has developed an indigenous system named Indian Regional Navigation Satellite System (IRNSS) or NavIC (Navigation with Indian Constellation), that consists of 7 satellites and transmits navigation signal in L and S bands. ISRO, for validation of the system, has installed many IGS (IRNSS/GPS/SBAS) receivers scattered over the Indian region. Using preliminary data from two geographically widely separated stations over India, this paper presents the results on studies on parameters of IRNSS signal quality and discusses how these parameters may be used to study the ionospheric behavior over the Indian region. The results show the importance and advantages of using IRNSS data for such studies.  相似文献   
235.
Based on an integrated approach, we solve the optimization problem for energy content and weight-dimensional characteristics of the electric servo drive by synthesis of structure and analysis of characteristics for different power supplies. The generalized power supply model, developed for different power supply of drive control systems, is given.  相似文献   
236.
The problem and features of measuring the speed and the direction angle of the wind vector relative to the longitudinal helicopter axis during parking, starting and takeoff-landing modes by onboard means are considered. The construction principles, information processing algorithms and advantages of onboard system for measuring the wind vector parameters based on ion-beacon and aerometric measuring channels, are disclosed.  相似文献   
237.
A regional tropospheric model can be constructed using surveys from GPS ground networks. Using this model the tropospheric delays of a kinematic station within the region can be interpolated. However, such a model is generally not suitable for an airborne platform high above the ground networks. In this paper, a method of constructing a regional tropospheric model for airborne GPS applications is described. First, the kinematic station in the air is projected onto the ground. Then the tropospheric delays at projected point are interpolated from those of the ground networks. Finally, the tropospheric delays at projected point are extended upward to the airborne platform using pressure and temperature gradients and humidity exponential function. For validation of this method, the data of airborne campaign carried out by BKG in cooperation with GFZ and BGR 2008 in the northern Alps are used. The results show that GPS kinematic positioning precision in height component can be improved using this method.  相似文献   
238.
239.
A methodology of creating a loading imitation model of a single-rotor helicopter with artificial neural network algorithms is considered. Stages of creation, the structure, and an algorithm of searching for an optimal neural networks configuration of loading imitation model are presented.  相似文献   
240.
This paper presents the results of analyzing the shaping of thin-walled conical parts with the uniform thickness along generatrix.  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