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   5497篇
  免费   25篇
  国内免费   19篇
航空   2552篇
航天技术   1689篇
综合类   11篇
航天   1289篇
  2021年   42篇
  2019年   27篇
  2018年   196篇
  2017年   165篇
  2016年   108篇
  2015年   54篇
  2014年   118篇
  2013年   137篇
  2012年   150篇
  2011年   273篇
  2010年   217篇
  2009年   305篇
  2008年   312篇
  2007年   245篇
  2006年   113篇
  2005年   172篇
  2004年   148篇
  2003年   166篇
  2002年   112篇
  2001年   182篇
  2000年   94篇
  1999年   96篇
  1998年   117篇
  1997年   84篇
  1996年   128篇
  1995年   145篇
  1994年   135篇
  1993年   69篇
  1992年   101篇
  1991年   43篇
  1990年   43篇
  1989年   101篇
  1988年   39篇
  1987年   39篇
  1986年   49篇
  1985年   139篇
  1984年   117篇
  1983年   82篇
  1982年   96篇
  1981年   148篇
  1980年   32篇
  1979年   30篇
  1978年   33篇
  1977年   36篇
  1976年   23篇
  1975年   39篇
  1974年   35篇
  1973年   28篇
  1970年   22篇
  1969年   22篇
排序方式: 共有5541条查询结果,搜索用时 140 毫秒
221.
A mathematical model of the process of bending and rolling the thin-walled components is presented taking into account the geometrical nonlinearity. Also presented is the technique for calculating the setup variables of bending equipment, which is based on reduction of the initial differential boundary-value problem to the discrete one with the use of the finite difference method.  相似文献   
222.
The experimental results obtained in experiment “STACO” made on board the Spacelab D-2 are re-visited, with image-analysis tools not then available. The configuration consisted of a liquid bridge between two solid supporting discs. An expected breakage occurred during the experiment. The recorded images are analysed and the measured behaviour compared with the results of a three dimensional model of the liquid dynamics, obtaining a much better fit than with linear models.  相似文献   
223.
The paper presents a technique of forming and evaluating the allowable clearance between a launch vehicle fairing and spacecraft.  相似文献   
224.
The results of the interplanetary scintillation observations performed in the period of the maximum of solar activity from April 2013 to April 2014 on the BSA LPI radio telescope at the frequency 111MHz are presented. Fluctuations of the radio emission flux were recorded round the clock for all sources with a scintillating flux of more than 0.2 Jy falling in a strip of sky with a width of 50° over declinations corresponding to a 96-beam directional pattern of the radio telescope. The total number of sources observed during the day reaches 5000. The processing of the observational data was carried out on the assumption that a set of scintillating sources represents a homogeneous statistical ensemble. Daily two-dimensional maps of the distribution of the level of scintillations, whose analysis shows the strong nonstationarity and large-scale irregularity of the spatial distribution of solar wind parameters, were constructed. According to maps of the distribution of the level of scintillations averaged over monthly intervals, the global structure of the distribution of the solar wind was investigated in the period of the maximum of solar activity, which was found to be on the average close to spherically symmetric. The data show that on a spherically symmetric background an east–west asymmetry is observed, which indicates the presence of a large-scale structure of a spiral type in the solar wind.  相似文献   
225.
226.
This paper deals with the technical features of designing an information-controlling system to prevent critical operating conditions of the helicopter flight, a technique for evaluating its effectiveness, analysis and synthesis of the measurement channels, forming of warning signals, and information support of the crew in abnormal situations.  相似文献   
227.
We determine the behavior of onboard gas-generator flowrate for generating the cavitation flow around a hybrid aerial underwater vehicle by using an annular wing on the underwater trajectory section.  相似文献   
228.
Junocam is a wide-angle camera designed to capture the unique polar perspective of Jupiter offered by Juno’s polar orbit. Junocam’s four-color images include the best spatial resolution ever acquired of Jupiter’s cloudtops. Junocam will look for convective clouds and lightning in thunderstorms and derive the heights of the clouds. Junocam will support Juno’s radiometer experiment by identifying any unusual atmospheric conditions such as hotspots. Junocam is on the spacecraft explicitly to reach out to the public and share the excitement of space exploration. The public is an essential part of our virtual team: amateur astronomers will supply ground-based images for use in planning, the public will weigh in on which images to acquire, and the amateur image processing community will help process the data.  相似文献   
229.
The paper discusses the applicability of cold gaseous nitrogen as a model working fluid in testing the hydrogen pump seals for power plants by three-dimensional modeling.  相似文献   
230.
This paper considers the axisymmetric transverse vibrations of aircraft nonuniform structural elements that are introduced by a thermal shock. Analytical solutions have been obtained and their numerical analysis has been performed.  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