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   4155篇
  免费   23篇
  国内免费   15篇
航空   1755篇
航天技术   1478篇
综合类   17篇
航天   943篇
  2021年   40篇
  2019年   17篇
  2018年   99篇
  2017年   71篇
  2016年   71篇
  2015年   26篇
  2014年   110篇
  2013年   115篇
  2012年   106篇
  2011年   188篇
  2010年   133篇
  2009年   205篇
  2008年   228篇
  2007年   126篇
  2006年   85篇
  2005年   120篇
  2004年   131篇
  2003年   148篇
  2002年   82篇
  2001年   138篇
  2000年   72篇
  1999年   81篇
  1998年   101篇
  1997年   73篇
  1996年   108篇
  1995年   117篇
  1994年   85篇
  1993年   64篇
  1992年   94篇
  1991年   36篇
  1990年   30篇
  1989年   79篇
  1988年   35篇
  1987年   38篇
  1986年   40篇
  1985年   138篇
  1984年   87篇
  1983年   75篇
  1982年   93篇
  1981年   130篇
  1980年   34篇
  1979年   31篇
  1978年   32篇
  1977年   37篇
  1976年   27篇
  1975年   32篇
  1974年   34篇
  1973年   19篇
  1970年   22篇
  1969年   21篇
排序方式: 共有4193条查询结果,搜索用时 15 毫秒
91.
A data fusion model consisting of several levels of parallel decision fusions is considered. Global optimization of such a model is discussed to obtain the fusion rules for overall optimal performance. The reliability analysis of the proposed model is carried out to establish its superiority over the existing parallel and serial fusion models  相似文献   
92.
基于自联想网络的发动机传感器解析余度技术   总被引:7,自引:2,他引:7       下载免费PDF全文
本文提出了一种基于自联想神经网络的传感器解析余度技术。在这种网络中,冗余传感器的信息被压缩、重组进入网络的第一部分,网络的第二部分将压缩信息恢复出来。基于数据融合原理,若一个传感器发生故障,其它传感器仍可提供足够的信息代替发生故障的传感器。理论分析和用于涡轴发动机的仿真结果表明,这种特殊结构的自联想网络具有良好的过滤噪声和故障信号的作用,特别适合于用作不易建模的复杂对象的传感器信号重构  相似文献   
93.
94.
    
A method to find and identify failures in a spacecraft’s set of sensitive elements that measure vector quantities of different nature is discussed.  相似文献   
95.
    
Evolutionary models allow an assignment of both a mass and a luminosity to a Wolf-Rayet (WR) star in a cluster, and hence allow a determination of the Bolometric Correction (B.C.). The B.C.'s derived for WN stars range from –4.0 to –6.0 with the expected trend of larger values (in absolute values) for stars with higher excitation spectra. For WC stars, there is little evidence for a similar trend; most observations presented here are consistent with B.C.=–4.5, as found by Smith and Maeder (1989). The convergence of B.C. values derived from evolutionary and atmospheric models is extremely satisfactory, giving increased confidence in both methods.  相似文献   
96.
The last decade has seen a period of rapid growth in our understanding of the processes which occur in the auroral regions. Much of our understanding is based on the copious new observations which have been made available in the auroral community. The present work is a short overview of the plasma conditions which obtain throughout much of the auroral region. It covers the diffuse and discrete auroral electron precipitation in the morning and evening oval, cusp, and polar cap. The ionospheric ion outflow throughout the high latitude regime is also described and related to the electron observations.  相似文献   
97.
    
The history and current status of heliospheric physics are outlined very briefly. It is emphasized that the existing Voyager Interstellar Mission should go a long way to answering many of the outstanding questions during the next one or two decades, especially those concerning the nature and structure of the solar wind termination shock.  相似文献   
98.
This paper reviews the progress achieved in planetary atmospheric electricity, with focus on lightning observations by present operational spacecraft, aiming to fill the hiatus from the latest review published by Desch et al. (Rep. Prog. Phys. 65:955–997, 2002). The information is organized according to solid surface bodies (Earth, Venus, Mars and Titan) and gaseous planets (Jupiter, Saturn, Uranus and Neptune), and each section presents the latest results from space-based and ground-based observations as well as laboratory experiments. Finally, we review planned future space missions to Earth and other planets that will address some of the existing gaps in our knowledge.  相似文献   
99.
    
This summary paper outlines the advantages of laser satellite communications (laser satcom) and summarizes the status of relevant programs. It concludes that laser satcom systems offer valuable performance capabilities and system advantages. It notes the urgent need for flight demonstrations to establish the viability and characterize the performance of laser satcom systems.  相似文献   
100.
This paper reports the main characteristics of the deep space transponder (DST) equipment that has been designed, developed and tested by Thales Alenia Space—Italy (TAS-I) for the European Space Agency (ESA) BepiColombo mission to Mercury.  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