全文获取类型
收费全文 | 463篇 |
免费 | 6篇 |
国内免费 | 5篇 |
专业分类
航空 | 246篇 |
航天技术 | 130篇 |
综合类 | 7篇 |
航天 | 91篇 |
出版年
2022年 | 4篇 |
2021年 | 7篇 |
2020年 | 3篇 |
2019年 | 9篇 |
2018年 | 22篇 |
2017年 | 11篇 |
2016年 | 4篇 |
2015年 | 6篇 |
2014年 | 10篇 |
2013年 | 29篇 |
2012年 | 21篇 |
2011年 | 28篇 |
2010年 | 16篇 |
2009年 | 19篇 |
2008年 | 17篇 |
2007年 | 27篇 |
2006年 | 17篇 |
2005年 | 22篇 |
2004年 | 13篇 |
2003年 | 8篇 |
2002年 | 5篇 |
2001年 | 11篇 |
2000年 | 13篇 |
1999年 | 9篇 |
1998年 | 6篇 |
1997年 | 3篇 |
1996年 | 8篇 |
1995年 | 16篇 |
1994年 | 10篇 |
1993年 | 2篇 |
1992年 | 9篇 |
1991年 | 2篇 |
1989年 | 2篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1985年 | 16篇 |
1984年 | 12篇 |
1982年 | 6篇 |
1981年 | 18篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1975年 | 3篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1967年 | 3篇 |
1966年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有474条查询结果,搜索用时 234 毫秒
71.
As Viking Landers did not measure rock compositions, Pathfinder (PF) data are the first in this respect. This review gives no proof yet whether the PF rocks are igneous or sedimentary, but for petrogenetic reasons they could be igneous. We suggest a model in which Mars is covered by about 50% basaltic and 50% andesitic igneous rocks. The soils are a mixture of the two with addition of Mg-sulfate and -chloride plus iron compounds possibly derived from the hematite deposits. 相似文献
72.
R Facius K Scherer G Reitz H Bucker L V Nevzgodina E N Maximova 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1994,14(10):93-103
The potentially specific importance of the heavy ions of the galactic cosmic radiation for radiation protection in manned spaceflight continues to stimulate in situ, i.e., spaceflight experiments to investigate their radiobiological properties. Chromosome aberrations as an expression of a direct assault on the genome are of particular interest in view of cancerogenesis being the primary radiation risk for man in space. In such investigations the establishment of the geometrical correlation between heavy ions' trajectories and the location of radiation sensitive biological substructures is an essential task. The overall qualitative and quantitative precision achieved for the identification of particle trajectories in the order of approximately 10 micrometers as well as the contributing sources of uncertainties are discussed. We describe how this was achieved for seeds of Lactuca sativa as biological test organisms, whose location and orientation had to be derived from contact photographies displaying their outlines and those of the holder plates only. The incidence of chromosome aberrations in cells exposed during the COSMOS 1887 (Biosatellite 8) and the COSMOS 2044 (Biosatellite 9) mission was determined for seeds hit by cosmic heavy ions. In those seeds the incidence of both single and multiple chromosome aberrations was enhanced. The results of the Biosatellite 9 experiment, however, are confounded by spaceflight effects unrelated to the passage of heavy ions. 相似文献
73.
Sven Kühl Janis Pukite T. Deutschmann Ulrich Platt Thomas Wagner 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
The Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) measures scattered sun light also in limb viewing mode (i.e. tangential to Earth’s surface and its atmosphere), which allows determining vertical profiles of atmospheric trace gases. First results on the retrieval of NO2, BrO and OClO profiles from the SCIAMACHY Limb measurements are presented and compared to independent satellite and balloon borne observations. 相似文献
74.
75.
76.
Thomas H. Vonder Haar 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1982,2(6):3-10
A body of techniques that have been developed and planned for use during the Earth Radiation Budget Experiment (ERBE), the International Satellite Cloud Climatology Project (ISCCP), and related climate experiments of the 1980's are reviewed. Validation and verification methods must apply for of satellites. They include: (1) use of a normalization or intercalibration satellite, (2) special intensive observation areas located over ground-truth sites, and (3) monitoring of sun and earth by several satellites and/or several instruments at the same time. Since each climate application area has a hierarchy of user communities, validation techniques vary from very detailed methods to those that simply assure high relative accuracy in detecting space and time variations for climate studies. It is shown that climate experiments generally require more emphasis on long-term stability and internal consistency of satellite data sets than high absolute accuracy. 相似文献
77.
Jürgen Blumenberg 《Acta Astronautica》1981,8(8):839-854
In this paper it is shown how a nuclear power system with turboelectric conversion is being optimised for application in space and how data subject to the mission and technological data enter into such an analysis. Thereafter it follows a comparison with nuclear power systems with magnetofluiddynamic and thermionic converters. 相似文献
78.
G.E. Thomas 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(12):127-130
It is often observed that the stratospheric and mesospheric temperature structure undergoes transient disturbances from its averaged steady-state behavior. The causes may be traceable to gravity waves, planetary waves, solar proton and relativistic electron precipitation, etc. We examine the theoretical time behavior of the atmospheric temperature following the cessation of such heating phenomena as it relaxes toward its quiescent steady-state value. We also study the time-dependent response during a model stratospheric-warming/mesospheric-cooling event. In particular, we investigate the roles of eddy heat conduction, non-LTE cooling in the 15μm CO2 band, and an ambient vertical wind, and their relative importance as they depend upon altitude and time, in modifying temperature changes in this region. 相似文献
79.
The National Microwave Landing Systems (MLS) program is a joint DOT/DOD/NASA effort to implement a common civil/military precision landing system to replace the current Instrument Landing System (ILS). The MLS will be capable of providing precision landing guidance down to Category III minimum while allowing for complex approach paths in both the horizontal and vertical planes. The system is based on the Time Reference Scanning Beam (TRSB) technique which was selected by the International Civil Aviation Organization (ICAO) in April 1978 as the new international landing system standard. MLS is less susceptible to interference from the surrounding area and provides a greater signal coverage area than ILS. 相似文献
80.
G Horneck H Bucker K Dose K D Martens A Bieger H D Mennigmann G Reitz H Requardt P Weber 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(10):19-27
Bacterial spores are proper test organisms for studying problems of space biology and exobiology. During the Spacelab 1 mission, studies on the limiting factors for survival of Bacillus subtilis spores in free space have been performed. An exposure tray on the pallet of Spacelab 1 accomodated 316 samples of dry spores for treatment with space vacuum and/or the following selected wavelengths of solar UV: > 170 nm, 220 nm, 240nm, 260nm and 280 nm. After recovery, inactivation, mutation induction, reparability, and photochemical damages in DNA and protein have been studied. The results contribute to the understanding of the mechanisms of increased UV sensitivity of bacterial spores in vacuo and to a better assessment of the chance of survival of resistant forms in space and of interplanetary transfer of life. 相似文献