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   7850篇
  免费   11篇
  国内免费   20篇
航空   3743篇
航天技术   2332篇
综合类   196篇
航天   1610篇
  2021年   64篇
  2019年   38篇
  2018年   230篇
  2017年   167篇
  2016年   154篇
  2015年   58篇
  2014年   166篇
  2013年   218篇
  2012年   222篇
  2011年   339篇
  2010年   262篇
  2009年   391篇
  2008年   378篇
  2007年   273篇
  2006年   148篇
  2005年   202篇
  2004年   183篇
  2003年   225篇
  2002年   249篇
  2001年   302篇
  2000年   124篇
  1999年   163篇
  1998年   199篇
  1997年   131篇
  1996年   169篇
  1995年   234篇
  1994年   198篇
  1993年   112篇
  1992年   155篇
  1991年   64篇
  1990年   81篇
  1989年   154篇
  1988年   64篇
  1987年   72篇
  1986年   63篇
  1985年   205篇
  1984年   162篇
  1983年   148篇
  1982年   150篇
  1981年   218篇
  1980年   78篇
  1979年   59篇
  1978年   69篇
  1977年   47篇
  1976年   51篇
  1975年   57篇
  1974年   49篇
  1972年   60篇
  1971年   56篇
  1969年   38篇
排序方式: 共有7881条查询结果,搜索用时 14 毫秒
991.
A study of the distribution of gain-to-noise-temperature (G/T) values for the Tracking and Data Relay Satellite (TDRS) satellite is described. The statistics of the G/T values are determined by a Monte Carlo simulation of the orbital geometry of the Sun and Moon, and the gain and noise temperature calculations is included. The results and their underlying assumptions are described  相似文献   
992.
Hardware-in-the-loop testing technology for automatic control, condition monitoring and diagnostics systems of gas turbine engines is described. The technology proposed makes it possible to simulate combinations and chains of unexpected and gradual failures of engines, transducers and actuators.  相似文献   
993.
Examples of application of the interference holography method for diagnostics of failure, technical condition and in nondestructive check of turbomachine parts are presented.  相似文献   
994.
The algorithmic support of a small-sized navigation system on the basis of the magnetoinertial course transmitter is considered; the support makes it possible to significantly reduce accumulating errors that are due to incomplete data on wind parameters and decrease requirements for random errors of initial data sensors.  相似文献   
995.
A set of systems for labor standard computer-aided design is described, namely, initial developments, advance and state-of-the art.  相似文献   
996.
A modification of the Zimont turbulent combustion model is presented; the modification makes it possible to describe processes in diffusion and homogeneous flame fronts as well as to take into account the influence of different factors that cause flame destabilization. The model is based on the equation for a reaction completeness extent (completeness of combustion). The model realization to simulate the premixed combustion is described and the modification of the turbulent combustion model is applied to simulate a process of flameout downstream of the flameholder.  相似文献   
997.
This article is devoted to the experimental works carried out in the R2Ch blow-down wind tunnel in the framework of the atmospheric re-entry PRE-X demonstrator program and to the fundamental studies performed on a hollow cylinder-flare relative to crucial problem of the transitional shock-wave/boundary-layer interaction.Shock-wave/boundary-layer interactions in hypersonic flows may have major consequences on thermal loads, especially if the shock is strong enough to induce separation. The heat-flux density levels in the interaction region strongly depend on the nature, laminar or turbulent of the boundary-layer. Special attention should be paid to transitional interactions, which are likely to exist at altitude where the Mach number is high and the density low.The wide Reynolds number range achievable in the R2Ch facility and reliable heat-flux measurements by infrared thermography have allowed to investigate the viscous interaction on the deflected flaps of the demonstrator model and to point out the laminar-to-turbulent boundary-layer natural and forced transition, in the light of the in-depth analysis of results obtained from the hollow cylinder-flare study.  相似文献   
998.
Some experimental data on the process of impulsive ultrasonic machining are presented. Also given are the data on variations in the impulsive vibration frequency of a workpiece and a tool.  相似文献   
999.
Tower air traffic control is currently performed using several unintegrated systems. While each of these systems supports performing an isolated task, the compilation of tools presents a number of challenges. This paper reports ways in which the Tower Control Computer Complex (TCCC) will support and enhance user management of numerous systems. Areas that will be notably improved include the consistency in the user interface of the air traffic control toolset, the task of manually integrating tools and information, toolset alert management, and toolset organization and administration  相似文献   
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