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   153篇
  免费   18篇
  国内免费   26篇
航空   81篇
航天技术   16篇
综合类   10篇
航天   90篇
  2024年   8篇
  2023年   9篇
  2022年   16篇
  2021年   3篇
  2020年   6篇
  2019年   8篇
  2018年   8篇
  2017年   4篇
  2016年   6篇
  2015年   2篇
  2014年   7篇
  2013年   2篇
  2012年   7篇
  2011年   1篇
  2010年   5篇
  2009年   4篇
  2008年   6篇
  2007年   8篇
  2006年   14篇
  2005年   10篇
  2004年   5篇
  2003年   3篇
  2002年   4篇
  2001年   7篇
  2000年   2篇
  1999年   1篇
  1998年   8篇
  1997年   3篇
  1996年   2篇
  1995年   4篇
  1994年   7篇
  1993年   3篇
  1992年   3篇
  1991年   3篇
  1989年   3篇
  1988年   1篇
  1984年   1篇
  1983年   1篇
  1982年   1篇
  1975年   1篇
排序方式: 共有197条查询结果,搜索用时 0 毫秒
111.
弹载遥测系统主要用于导弹飞行试验过程中,完成导弹飞行试验数据的采编、调制、传输,与地面遥测设备配合完成试验数据远距离获取,即遥测任务。遥测数据为导弹及分系统设计验证、故障分析、试验结论评判等提供数据依据,是导弹研制过程中极其重要、必不可少的测量系统。结合导弹遥测系统技术发展趋势及笔者近年来创新性工程设计经验,详细阐述了包括弹载遥测系统架构设计、可编程式采编技术、优化供电技术及射频综合化技术等总体关键性技术,为弹载遥测系统提供总体设计新思路。  相似文献   
112.
文章介绍了CBERS-1卫星红外光谱扫描仪(IRMSS)的设计与在轨运行情况。  相似文献   
113.
炭纤维网胎表面改性   总被引:1,自引:0,他引:1  
为改善炭纤维网胎的针刺性能,采用二甲基硅油、咪唑啉、水溶性二甲基硅油等表面剂处理炭纤维网胎,按照相同针刺工艺制备试验件.扫描电镜结果表明,二甲基硅油处理后网胎纤维相互粘连,水溶性二甲基硅油处理后的网胎呈疏松状态,纤维表面光滑.3种表面剂处理的针刺试样Z向剥离强度,咪唑林达到0.144 MPa,其余两种达到0.128 MPa.相对于咪唑啉和二甲基硅油,水溶性二甲基硅油可与水以任意比例互溶,且成本低,为理想的炭纤维网胎表面处理剂.  相似文献   
114.
第二次鸦片战争期间及其以后,沙俄通过军事威胁和外交讹诈,强迫腐败无能的清政府签订了《中俄瑷珲条约》《中俄北京条约》《中俄勘分西北界约记》,割占了我国东北和西北的144万平方公里的领土;以后,又通过不平等的界约和武力侵占,三次共掠去了26万平方公里的土地,沙俄共占去了我国170万平方公里,相当于50个海南省,48个台湾省的面积。  相似文献   
115.
116.
In a 45-day experiment test subjects were exposed to bed rest with their heads down at -4 degrees C. Twice a day their muscles of the stomach, back, femur, and shin were stimulated with electric current for 25-30 min. The value of muscle tension was close to their maximum voluntary contraction. The main objective was to prevent muscle atrophy and to maintain their trophic and functional state. Physiological measurements were carried out together with morphological, cytochemical, and biometric evaluations. The tissue removed during biopsy from M. soleus 7 days before the test and on the 30th hypokinetic day was used as substrate. Electrostimulation affected favourably the tone and strength of muscles as well as their static and dynamic endurance. Morphological studies showed a positive effect of electrostimulation on the muscle tissue, preventing the development of atrophic processes. During the first post-hypokinetic day orthostatic tolerance increased.  相似文献   
117.
The NASA Astrobiology Roadmap provides guidance for research and technology development across the NASA enterprises that encompass the space, Earth, and biological sciences. The ongoing development of astrobiology roadmaps embodies the contributions of diverse scientists and technologists from government, universities, and private institutions. The Roadmap addresses three basic questions: How does life begin and evolve, does life exist elsewhere in the universe, and what is the future of life on Earth and beyond? Seven Science Goals outline the following key domains of investigation: understanding the nature and distribution of habitable environments in the universe, exploring for habitable environments and life in our own solar system, understanding the emergence of life, determining how early life on Earth interacted and evolved with its changing environment, understanding the evolutionary mechanisms and environmental limits of life, determining the principles that will shape life in the future, and recognizing signatures of life on other worlds and on early Earth. For each of these goals, Science Objectives outline more specific high-priority efforts for the next 3-5 years. These 18 objectives are being integrated with NASA strategic planning.  相似文献   
118.
Laboratory experiments that produced tholins in a simulated Titan atmosphere were conducted. We report the first systematic analyses of these compounds using Fourier-transform ion cyclotron resonance mass spectrometry. The findings suggest surprising simplicity and nonrandomness in the mass distribution and regularity in species clusters. The degree of unsaturation generally increased with increasing molecular weight in a predictable fashion, and nitrogen is proposed as the dominant carrier of unsaturation. In detected compounds with a general formula of C(x)H(y)N(z), the carbon to nitrogen ratio (x/z) varied only slightly within a narrow limit, and decreased with increasing molecular weights. These compounds are of potential prebiotic interest since they sediment to the surface of Titan, and would dissolve readily in transient aqueous pools that might be generated from time to time by impacts and volcanic  相似文献   
119.
120.
用介电常数监测酯类润滑油   总被引:2,自引:0,他引:2  
  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