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   161篇
  免费   8篇
  国内免费   10篇
航空   66篇
航天技术   18篇
综合类   8篇
航天   87篇
  2023年   1篇
  2022年   3篇
  2021年   3篇
  2020年   2篇
  2018年   2篇
  2016年   2篇
  2015年   1篇
  2014年   3篇
  2013年   3篇
  2012年   3篇
  2011年   8篇
  2010年   5篇
  2009年   1篇
  2008年   5篇
  2007年   7篇
  2006年   2篇
  2005年   12篇
  2004年   3篇
  2003年   8篇
  2002年   6篇
  2001年   3篇
  2000年   6篇
  1999年   5篇
  1998年   2篇
  1997年   4篇
  1996年   9篇
  1995年   11篇
  1994年   5篇
  1993年   3篇
  1992年   3篇
  1991年   3篇
  1990年   7篇
  1989年   4篇
  1988年   6篇
  1987年   7篇
  1986年   1篇
  1985年   3篇
  1984年   5篇
  1983年   6篇
  1982年   2篇
  1981年   2篇
  1980年   1篇
  1979年   1篇
排序方式: 共有179条查询结果,搜索用时 78 毫秒
151.
152.
爱丁堡皇家天文台的COSMOS自动测量仪是为现代化的大型施密特望远镜的天文数据测量而设计的测量系统。COSMOS的功能之一是自动地从拍摄到的大量星体图象中分离出星系图象。设在澳大利亚的英国施密特望远镜能拍到南天的23等星。COSMOS对施密特望远镜干板测量后,自动识别出星系图象,这样就能对大量可观测的宇宙天体中的星系分布情况进行研究。  相似文献   
153.
Ten healthy subjects were eccentrically rotated with constant speed on a Barany chair. Setting of a luminous line (LL) to the subjective vertical and ocular counter-roll (OCR) were evaluated. During eccentric position rotation subjects consistently reported illusory rotation and set the LL to an angle correlating to centrifugal force. At the same time an OCR of opposite direction was measured. In one patient, labyrinthectomized on the right side, only counterclockwise rotation of the luminous line was observed. Differences between "inner" and "outer" eye were evident for luminous line settings and OCR in some subjects. The results indicate that eccentric rotation is a valuable method to test for bilateral otolith asymmetries. The method can be applied to preflight tests of astronaut candidates for susceptibility to spacesickness. It is also offered for clinical evaluation of unilateral otolith impairments.  相似文献   
154.
重点介绍了当前巴西以用户为导向的中巴地球资源卫星(CBERS-1)数据在森林采伐监测、土地利用规划、影像制图和科学应用等方面的应用项目,对今后利用中巴地球资源卫星开展国家项目发表了一些看法。  相似文献   
155.
本文报导了凯夫拉-49纤维缠绕的直径为5.75英寸各种压力容器的环向纤维应力特性,在这些容器制作中,分别采用了不同的环氧树脂系统,一种松粘剂预处理的纤维/环氧系统,一种环向纤维材料上不加树脂的系统以及一种未经预处理的系统。树脂系统以三类常用的环氧树脂为代表:刚性环氧树脂、半柔性环氧树脂、及橡胶增韧的粘性环氧树脂。曾通过压力容器试验温度的变化来导致纤维/基体界面的变化。由于纤维/基体的高度偶联,引起了压力容器中纤维拉伸性能的降低,其值为凯夫拉-49浸胶纱带公称拉伸强度的51-77%。本文并提出了解释这些现象的机理。  相似文献   
156.
MW  Barclay  NK  Williams  罗先志 《空载雷达》2005,(4):25-30
海上监视对高分辨率雷达成像模式特别感兴趣。在海上监视应用中,可以使用高分辨率雷达成像模式来支持对已经用传统搜索功能和跟踪功能检测到的海面目标的分类和可能的识别。  相似文献   
157.
Tírez Lake (La Mancha, central Spain) is proposed as a terrestrial analogue of Europa's ocean. The proposal is based on the comparison of the hydrogeochemistry of Tírez Lake with the geochemical features of the alteration mineralogy of meteoritic precursors and with Galileo's Near Infrared Mapping Spectrometer data on Europa's surface. To validate the astrobiological potential of Tírez Lake as an analog of Europa, different hydrogeochemical, mineral, and microbial analyses were performed. Experimental and theoretical modeling helped to understand the crystallization pathways that may occur in Europa's crust. Calculations about the oxidation state of the hypothetical Europan ocean were estimated to support the sulfate-rich neutral liquid model as the origin of Europa's observed hydrated minerals and to facilitate their comparison with Tírez's hydrogeochemistry. Hydrogeochemical and mineralogical analyses showed that Tírez waters corresponded to Mg-Na-SO(4)-Cl brines with epsomite, hexahydrite, and halite as end members. A preliminary microbial ecology characterization identified two different microbial domains: a photosynthetically sustained community represented by planktonic/benthonic forms and microbial mat communities, and a subsurficial anaerobic realm in which chemolithotrophy predominates. Fluorescence in situ hybridization has been used to characterize the prokaryotic diversity of the system. The subsurficial community seemed to be dominated by sulfate-reducing bacteria and methanogens. Frozen Tírez brines were analyzed by Fourier-transform infrared techniques providing spectra similar to those reported previously using pure components and to the Galileo spectral data. Calorimetric measurements of Tírez brines showed pathways and phase metastability for magnesium sulfate and sodium chloride crystallization that may aid in understanding the processes involved in the formation of Europa's icy crust. The use of fluorescence hybridization techniques for microbial detection and characterization in hypersaline environments makes this methodology strongly advisable for future Europa astrobiological missions.  相似文献   
158.
The ability to voluntarily stabilize the head in space during lateral rhythmic oscillations of the trunk has been investigated during parabolic flights. Five healthy young subjects, who gave informed consent, were examined. The movements were performed with eyes open or eyes closed, either during phases of microgravity or phases of normal gravity. The main result to emerge from this study is that the head may be stabilized in space about the roll axis under microgravity conditions with, as well as without vision, despite the reduction of the vestibular afferent and the muscle proprioceptive inputs. Moreover, the absence of head stabilization about the yaw axis confirms that the degrees of freedom of the neck can be independently controlled, as it was previously shown [1]. These results seem to indicate that voluntary head stabilization does not depend crucially upon static vestibular afferents. Head stabilization in space may be in fact organized on the basis of either dynamic vestibular afferents or a postural body scheme.  相似文献   
159.
Urinary excretion of amino acids by the 9 Skylab crewmen was studied as an indicator of the metabolic effects caused by exposure to the space flight environment. Intake was consistent in quality and quantity throughout the 28, 59 and 84-day flights for each of the crewmen and complete collections were accomplished. The results indicated an increased excretion in most amino acids during the first month of flight which remained elevated in the second and third months but to a lesser extent. Additional indications of change in muscle and skeletal metabolism were observed. These results point to the desirability of obtaining additional indices of alterations in protein synthetic processes in conjunction with future space flights.  相似文献   
160.
This article is an interview with U.S. astronaut Norman Thagard. He was on the Russian Mir 18 mission. Launched to the space station from Baikonur on March 14, 1995, he returned to Earth on the Shuttle 115 days later. With the completion of that mission, Thagard holds the U.S. record for the most time spent in space. Topics of discussion during the interview include: the cultural isolation faced by an American astronaut on a Russian space facility; the physiological and psychological effects of long-duration space flight; the problems of loss of bone and the radiation environment; readaptation to gravity on Earth; and, recommendations to the designers of the Alpha station.  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