全文获取类型
收费全文 | 7920篇 |
免费 | 1141篇 |
国内免费 | 1274篇 |
专业分类
航空 | 4633篇 |
航天技术 | 2286篇 |
综合类 | 1137篇 |
航天 | 2279篇 |
出版年
2024年 | 12篇 |
2023年 | 32篇 |
2022年 | 123篇 |
2021年 | 158篇 |
2020年 | 187篇 |
2019年 | 104篇 |
2018年 | 139篇 |
2017年 | 127篇 |
2016年 | 140篇 |
2015年 | 251篇 |
2014年 | 376篇 |
2013年 | 399篇 |
2012年 | 512篇 |
2011年 | 559篇 |
2010年 | 591篇 |
2009年 | 613篇 |
2008年 | 615篇 |
2007年 | 519篇 |
2006年 | 431篇 |
2005年 | 404篇 |
2004年 | 301篇 |
2003年 | 275篇 |
2002年 | 288篇 |
2001年 | 304篇 |
2000年 | 281篇 |
1999年 | 338篇 |
1998年 | 320篇 |
1997年 | 249篇 |
1996年 | 211篇 |
1995年 | 177篇 |
1994年 | 225篇 |
1993年 | 168篇 |
1992年 | 178篇 |
1991年 | 132篇 |
1990年 | 106篇 |
1989年 | 120篇 |
1988年 | 74篇 |
1987年 | 55篇 |
1986年 | 34篇 |
1985年 | 27篇 |
1984年 | 36篇 |
1983年 | 28篇 |
1982年 | 28篇 |
1981年 | 29篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1975年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 453 毫秒
991.
This paper presents the results of medical investigations performed in the Salyut-7 8-month mission in which a professional physician took part. The paper contains anthropometric measurements, results of investigating the vestibular function, cardiovascular function at rest and in response to multi-step tests (with emphasis on echocardiographic measurements), metabolic parameters and hormonal status. It also discusses medical aspects of the extravehicular activity. The medical investigations, although some new methods were applied, provided the continuity of methodical approaches and data accumulated in previous missions. 相似文献
992.
Y Ishikawa K Kuriki 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(9):35-38
The chemistry in a supersonic plasma source flow was studied as a laboratory model for interstellar chemical evolution. It is important to match the similarity parameters for cosmic and laboratory conditions, which connect the temporal and spatial scales of the two cases. The apparatus simulated the conditions in a molecular cloud with respect to molecular-ionic reaction fraction, temperature, and non-equilibrium kinetics. The plasma flow was found to be cold enough, by the radical expansion, to produce polyatomic molecules. From the simple atomic plasma as reactant, cyanopolyyne and unsaturated hydrocarbons were synthesized in the present experiment. These molecules are also inherent in molecular clouds. The reaction mechanism is discussed. 相似文献
993.
994.
T. Natarajan Y.S. Rajan 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(11):31-34
The paper deals with the Indian experience in training the resources scientists in the fast developing field of remote sensing and the facilities available for obtaining such training in India. The necessity of imparting training to the scientists at different levels is brought out. An outline of the training curriculum of a leading institution is described in some detail. 相似文献
995.
Y. Takayama T. Takashima K. Matsuura K. Naito 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1982,2(6):165-172
For accurate measurements of sea surface temperature in the 11 μm window region, it is necessary to eliminate the effect of atmospheric absorption. A technique using observations from different angles is one of the methods of eliminating this atmospheric effect. This technique is not possible at present, using a single satellite; but using two geosynchronous satellites, it is possible to observe a common area from two different elevation angles. To correct for atmospheric effects, therefore, we compared the infrared data obtained from observations at about the same time (less than a minute apart) on the equator using the GMS-1 and GMS-2 satellites which had about 20° longitudinal separation. It was found that if the infrared spectral wavelength channel of one geosynchronous satellite is selected to be different from that of the other, it is possible to improve the two-satellite observation technique of estimating water vapor content in a tropical atmosphere. This technique corresponds to split window measurements by the AVHRR radiometer on board the NOAA-7 satellite. 相似文献
996.
997.
Y. Malméjac 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(5):61-64
This report deals with the present plans and philosophy of the European Space Agency as regards the interest and the justification for a European Experimental Research Program in Space. It offers recommendations to be considered by both the space investigators and the E.S.A. executive in order to achieve the most urgent needs. 相似文献
998.
999.
1000.
本文对J-8ACT验证机纵向数字电传操纵系统所使用的平尾助力系统的抖振原因和抑制措施进行了线性和非线性分析。证明了引起助力系统抖振的主要原因,除由流量特性决定的过大的流量系数外,对于内反馈式的助力系统来说,不可避免的安装支承间隙是一个重要因素。机械输入式液压伺服裝置的一些重要特性是由滑阀摩擦引起的。这种受机械反馈影响的特殊摩擦力,具有增加液压作动器的增益和滞后作用。由于这个特点,它能抑制/消除助力系统抖振。 相似文献