全文获取类型
收费全文 | 333篇 |
免费 | 10篇 |
国内免费 | 15篇 |
专业分类
航空 | 131篇 |
航天技术 | 34篇 |
综合类 | 8篇 |
航天 | 185篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 5篇 |
2015年 | 2篇 |
2014年 | 5篇 |
2013年 | 5篇 |
2012年 | 15篇 |
2011年 | 20篇 |
2010年 | 10篇 |
2009年 | 2篇 |
2008年 | 9篇 |
2007年 | 11篇 |
2006年 | 9篇 |
2005年 | 7篇 |
2004年 | 7篇 |
2003年 | 12篇 |
2002年 | 10篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1998年 | 16篇 |
1997年 | 5篇 |
1996年 | 10篇 |
1995年 | 21篇 |
1994年 | 17篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 11篇 |
1988年 | 15篇 |
1987年 | 10篇 |
1986年 | 2篇 |
1985年 | 13篇 |
1984年 | 11篇 |
1983年 | 18篇 |
1982年 | 15篇 |
1981年 | 9篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有358条查询结果,搜索用时 156 毫秒
11.
今年5月,《航空周刊》发布了最新的TPC榜单,全面反映了2012年航空航天和国防领域内各企业的综合表现。2012年,虽然全行业取得了创纪录的2%的营业收入和4%的利润增长,但这主要得益于不断攀升的民用市场,而国防工业则经历了相对惨淡的一年。 相似文献
12.
The need to acquire a better knowledge of the main biological problems induced by microgravity implies--in addition to human experimentation--the use of animal models, and primates seem to be particularly well adapted to this type of research. The major areas of investigation to be considered are the phospho-calcium metabolism and the metabolism of supporting tissues, the hydroelectrolytic metabolism, the cardiovascular function, awakeness, sleep-awakeness cycles, the physiology of equilibrium and the pathophysiology of space sickness. Considering this program, the Centre d'Etudes et de Recherches de Medecine Aerospatiale, under the sponsorship of the Centre National d'Etudes Spatiales, developed both a program of research on restrained primates for the French-U.S. space cooperation (Spacelab program) and for the French-Soviet space cooperation (Bio-cosmos program), and simulation of the effects of microgravity by head-down bedrest. Its major characteristics are discussed in the study. 相似文献
13.
We discuss the possibility of Earth-type planets in the planetary system of 55 Cancri, a nearby G8 V star, which is host to two, possibly three, giant planets. We argue that Earth-type planets around 55 Cancri are in principle possible. Several conditions are necessary. First, Earth-type planets must have formed despite the existence of the close-in giant planet(s). In addition, they must be orbitally stable in the region of habitability considering that the stellar habitable zone is relatively close to the star compared to the Sun because of 55 Cancri's low luminosity and may therefore be affected by the close-in giant planet(s). We estimate the likelihood of Earth-type planets around 55 Cancri based on the integrated system approach previously considered, which provides a way of assessing the long-term possibility of photosynthetic biomass production under geodynamic conditions. 相似文献
14.
ESA astronauts' ISS flight opportunities are considered as a vital source to meet the utilisation, operation and political objectives that Europe has established for participating in the International Space Station programme. Recent internal ESA assessments have demonstrated that a rate of three flights per year for European Astronauts should be maintained as a minimum objective. The current flight rate is lower than this. In order to improve this situation, in the context of the activation of the ESA ISS Commercialisation programme, ESA is developing the conditions for the establishment of commercially based human spaceflights with the financial support of both ESA and the private sector or, in the future, only the latter. ESA is working in a Partnership with the space industry to facilitate the implementation of such projects and support customers with a range of end-to-end commercial services. The opportunities and challenges of a "commercial human spaceflight", involving a member of the European Astronaut Corps, or a privately employed flight participant, are discussed here. 相似文献
15.
The availability of water-ice at the surface in the Mars polar cap and within the top meter of the high-latitude regolith raises the question of whether liquid water can exist there under some circumstances and possibly support the existence of biota. We examine the minimum temperatures at which liquid water can exist at ice grain-dust grain and ice grain-ice grain contacts, the minimum subfreezing temperatures at which terrestrial organisms can grow or multiply, and the maximum temperatures that can occur in martian high-latitude and polar regions, to see if there is overlap. Liquid water can exist at grain contacts above about -20 degrees C. Measurements of growth in organisms isolated from Siberian permafrost indicate growth at -10 degrees C and metabolism at -20 degrees C. Mars polar and high-latitude temperatures rise above -20 degrees C at obliquities greater than ~40 degrees, and under some conditions rise above 0 degrees C. Thus, the environment in the Mars polar regions has overlapped habitable conditions within relatively recent epochs, and Mars appears to be on the edge of being habitable at present. The easy accessibility of the polar surface layer relative to the deep subsurface make these viable locations to search for evidence of life. 相似文献
16.
Avdeev S Bidoli V Casolino M De Grandis E Furano G Morselli A Narici L De Pascale MP Picozza P Reali E Sparvoli R Boezio M Carlson P Bonvicini W Vacchi A Zampa N Castellini G Fuglesang C Galper A Khodarovich A Ozerov Y Popov A Vavilov N Mazzenga G Ricci M Sannita WG Spillantini P 《Acta Astronautica》2002,50(8):511-525
The phenomenon of light flashes (LF) in eyes for people in space has been investigated onboard Mir. Data on particles hitting the eye have been collected with the SilEye detectors, and correlated with human observations. It is found that a nucleus in the radiation environment of Mir has roughly a 1% probability to cause an LF, whereas the proton probability is almost three orders of magnitude less. As a function of LET, the LF probability increases above 10 keV/micrometer, reaching about 5% at around 50 keV/micrometer. 相似文献
18.
Rockwell公司为奥基丹(Ogden)空军后勤中心对选定的民兵导弹试验飞行进行了精度鉴定。其中一部份工作是对“制导-雷达”斜距比对进行回归分析。一般有六或七部雷达跟踪装有C波段相干应答机的被动段飞行器(PBV)。这些雷达中有几部还能测得距离变化率数据。最近的民兵Ⅲ试验飞行中,Rockwell可以得到联邦电子公司录取的实验性距离游标器磁带。该磁带只记录了一个站的数据,在事后鉴定中与标准的雷达磁带联合使用。本报告以实例叙述了采用游标测距数据的作用。 相似文献
19.
20.