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   8386篇
  免费   318篇
  国内免费   254篇
航空   4167篇
航天技术   2773篇
综合类   218篇
航天   1800篇
  2022年   74篇
  2021年   129篇
  2020年   65篇
  2019年   92篇
  2018年   203篇
  2017年   152篇
  2016年   162篇
  2015年   120篇
  2014年   268篇
  2013年   302篇
  2012年   310篇
  2011年   441篇
  2010年   332篇
  2009年   426篇
  2008年   443篇
  2007年   306篇
  2006年   238篇
  2005年   275篇
  2004年   237篇
  2003年   248篇
  2002年   190篇
  2001年   267篇
  2000年   164篇
  1999年   221篇
  1998年   238篇
  1997年   138篇
  1996年   211篇
  1995年   240篇
  1994年   228篇
  1993年   163篇
  1992年   187篇
  1991年   89篇
  1990年   66篇
  1989年   166篇
  1988年   81篇
  1987年   63篇
  1986年   70篇
  1985年   185篇
  1984年   146篇
  1983年   111篇
  1982年   116篇
  1981年   217篇
  1980年   50篇
  1979年   45篇
  1978年   50篇
  1977年   42篇
  1975年   51篇
  1974年   39篇
  1971年   35篇
  1970年   37篇
排序方式: 共有8958条查询结果,搜索用时 15 毫秒
341.
The DB-8 detectors of the ISS radiation monitoring system (RMS) have operated almost continuously onboard the ISS service module since August 2001 till December 2014. The RMS data obtained were used for the daily monitoring of the radiation environment aboard the station. This paper considers the technique of RMS data analysis that allows one to distinguish the contributions of galactic cosmic rays and the Earth’s inner radiation belt to the daily dose based on the dosimetry data obtained as a result of the station’s passage in areas of the highest geomagnetic latitudes. The paper presents the results of an analysis of the dosimetry data based on this technique for 2005–2011, as well as a comparison with similar results the authors obtained previously using the technique based on an analysis of the dosimetry data obtained during station passages in the area of the South Atlantic Anomaly.  相似文献   
342.
An exact analytical solution of the thermoelasticity problem is presented for a multilayer shallow cylinder with physical properties of the medium that are constant in the limits of each layer. The effect of thermal shock of different intensity as well as the penetration depth of thermal disturbance on the distribution of radial and circumferential thermal stresses has been studied as applied to the one- and two-layer cylinder. It has been shown that the circumferential compressive stresses appear on the external surface of the cylinder under thermal shock while the tensile stresses appear on the internal surface.  相似文献   
343.
344.
345.
346.
为缓解SMT上线程对Cache的争用,提出了基于访问数据模式的Cache缺失预测模型ADM。使用模型对线程访存轨迹进行分析和计算,以两个线程在下一个时间片的访存地址信息作为模型的输入,预测Cache缺失情况并以此作为线程间Cache争用指标。 ADM实现了针对共享数据访问和私有数据访问两种模式的缺失计算方法,对比分析表明,ADM加入了对共享数据情况的分析过程,分别计算针对不同模式访存序列,结果更为精确,仿真试验表明,Cache缺失预测模型结果与目前同类模型的预测结果相比,误差分布在合理的范围内,当两个访存序列中有较多共享数据时,使用SMM方法计算结果将更为准确,证明了对访问模式进行划分的必要性。  相似文献   
347.
Space Science Reviews - Time measured by an ideal clock crucially depends on the gravitational potential and velocity of the clock according to general relativity. Technological advances in...  相似文献   
348.
An evident signature of a least studied quasi-90-day oscillation is found in the winds and tides in the MLT from an equatorial station, São João do Cariri (7.4°S, 36.5°W). The oscillation is found to appear mainly in certain intervals with small but appreciable seasonal (fourth harmonic of annual oscillation) contribution. The maximum amplitude of the oscillation is found to be around 10 m/s in the zonal wind. The enhancement peak of the oscillation exhibits downward movement indicating a plausible role of upward moving waves/tides in carrying its imprint from below to the MLT. Similar oscillation feature in the tropospheric zonal wind and ozone may imply its lower atmospheric origin as a component of the intraseasonal oscillation (ISO) that moves upward by modulating the tides. Subsequently, the propagating tides (mainly semidiurnal) are enhanced by the ozone in the stratosphere through absorption of solar UV radiation and finally manifest the oscillation in the MLT. Consistency of the present findings with the past investigations are observed in some aspects of the oscillation, whereas existing mismatches in others are believed to be due to geophysical variability depending on space and time among various locations on the globe.  相似文献   
349.
Plasma of the free burning electric arc between Ag–SnO2–ZnO composite electrodes as well as brass electrodes were investigated. The plasma temperature distributions were obtained by Boltzmann plot method involving Cu I, Ag I or Zn I spectral line emissions. The electron density distributions were obtained from the width and from absolute intensity of spectral lines. The laser absorption spectroscopy was used for measurement of copper atom concentration in plasma. Plasma equilibrium composition was calculated using two independent groups of experimental values (temperature and copper atom concentration, temperature and electron density). It was found that plasma of the free burning electric arc between brass electrodes is in local thermodynamical equilibrium. The experimental verification of the spectroscopic data of Zn I spectral lines was carried out.  相似文献   
350.
Indian Space Research Organization (ISRO) has developed an indigenous system named Indian Regional Navigation Satellite System (IRNSS) or NavIC (Navigation with Indian Constellation), that consists of 7 satellites and transmits navigation signal in L and S bands. ISRO, for validation of the system, has installed many IGS (IRNSS/GPS/SBAS) receivers scattered over the Indian region. Using preliminary data from two geographically widely separated stations over India, this paper presents the results on studies on parameters of IRNSS signal quality and discusses how these parameters may be used to study the ionospheric behavior over the Indian region. The results show the importance and advantages of using IRNSS data for such studies.  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