全文获取类型
收费全文 | 5418篇 |
免费 | 9篇 |
国内免费 | 18篇 |
专业分类
航空 | 2838篇 |
航天技术 | 1920篇 |
综合类 | 23篇 |
航天 | 664篇 |
出版年
2021年 | 30篇 |
2019年 | 32篇 |
2018年 | 57篇 |
2017年 | 31篇 |
2014年 | 82篇 |
2013年 | 132篇 |
2012年 | 107篇 |
2011年 | 155篇 |
2010年 | 115篇 |
2009年 | 177篇 |
2008年 | 245篇 |
2007年 | 136篇 |
2006年 | 140篇 |
2005年 | 143篇 |
2004年 | 115篇 |
2003年 | 170篇 |
2002年 | 101篇 |
2001年 | 176篇 |
2000年 | 109篇 |
1999年 | 140篇 |
1998年 | 164篇 |
1997年 | 123篇 |
1996年 | 169篇 |
1995年 | 215篇 |
1994年 | 182篇 |
1993年 | 120篇 |
1992年 | 128篇 |
1991年 | 76篇 |
1990年 | 62篇 |
1989年 | 138篇 |
1988年 | 62篇 |
1987年 | 66篇 |
1986年 | 60篇 |
1985年 | 195篇 |
1984年 | 150篇 |
1983年 | 130篇 |
1982年 | 133篇 |
1981年 | 176篇 |
1980年 | 58篇 |
1979年 | 41篇 |
1978年 | 50篇 |
1977年 | 53篇 |
1976年 | 38篇 |
1975年 | 58篇 |
1974年 | 38篇 |
1973年 | 42篇 |
1972年 | 51篇 |
1971年 | 42篇 |
1970年 | 44篇 |
1969年 | 37篇 |
排序方式: 共有5445条查询结果,搜索用时 13 毫秒
771.
B.J. Bluth 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(7):13-22
Technology is neutral, its use is not. Its introduction and use take place in social, cultural, political and economic contexts which can be at considerable variance with those of the introducing countries, and which are not homogeneous within countries having wide variations in knowldege, background skills, and interpretations of meaning and opportunity.This paper tries to take a dispassionate look at the social and cultural factors that are involved in the introduction, use, and maintenance of space technology in the developing world. 相似文献
772.
J. Nishimura H. Hirosawa 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(11):239-249
This paper describes the systems for long duration flights developed in Japan for scientific observations. Much efforts have been expended to evolve systems for long duration flights in Japan, by controlling the balloon trajectories with a knowledge of wind pattern at high altitudes over Japan. These systems called “Cycling Balloon”, “Boomerang Balloon” and “New Boomerang Balloon” have been successfully used for the observations by keeping the balloons close to the balloon station.“Relay Balloon” is another system to extend the telemetry range by using an additional balloon as a relay station to link the telemetry from the main balloon.Some detailes of the exhaust valve, ascent meter and automatic level control devices used for the balloon control are also described in the paper. 相似文献
773.
J I Gitelson 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1992,12(5):167-192
Mars mission like the Lunar base is the first venture to maintain human life beyond earth biosphere. So far, all manned space missions including the longest ones used stocked reserves and can not be considered egress from biosphere. Conventional path proposed by technology for Martian mission LSS is to use physical-chemical approaches proved by the experience of astronautics. But the problem of man living beyond the limits of the earth biosphere can be fundamentally solved by making a closed ecosystem for him. The choice optimum for a Mars mission LSS can be substantiated by comparing the merits and demerits of physical-chemical and biological principles without ruling out possible compromise between them. The work gives comparative analysis of ecological and physical-chemical principles for LSS. Taking into consideration universal significance of ecological problems with artificial LSS as a particular case of their solution, complexity and high cost of large-scale experiments with manned LSS, it would be expedient for these works to have the status of an International Program open to be joined. A program of making artificial biospheres based on preceding experience and analysis of current situation is proposed. 相似文献
774.
The transmission of integrity information using a signal format compatible with the Global Positioning System (GPS) and relayed through a geostationary satellite repeater, which will be critical in achieving high integrity and availability of global navigation by satellite is discussed. The inclusion of navigation repeaters designed to fulfil this function, the next generation of INMARSAT spacecraft, INMARSAT-3 is examined. The global navigation satellite system (GNSS) integrity channel (GIC) will employ pseudorandom codes in the same family as, but distinct from, the codes reserved by GPS. The data format of the basic integrity channel is designed to convey user range error information for 24 to 40 satellites. A closed-loop timing compensation technique will be used at the uplinking Earth station, to make the signal's clock and carrier Doppler variations identical to those that would result from an onboard signal source. Therefore, the INMARSAT-3 satellites will increase the number of useful navigation satellites available to any user, and can also function as sources of precise timing. There is also a possibility that wide area differential corrections can be carried on the same signal 相似文献
775.
776.
S. Cazes J. Charra N. Coron B. Cougrand J.-F. Crifo J. Crovisier C. Emerich R. Gispert B. Gondet G. Guyot D. Harduin J.-M. Lamarre G. Levanti C. Maurel D. Parisot F. Rocard P. Salvetat A. Soufflot T. Encrenaz 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(9):273-276
The IKS infrared spectro-photometer will fly on board the VEGA platforms. It is designed to characterize the size, temperature and emissivity of the Comet Halley nucleus, to identify the major gaseous components of the inner coma and to detect the emission of the cometary grains. This paper presents the “calibration” experiments required to reduce the raw data: (i) absolute wavelength calibration of the filter wheels; (ii) modeling of the internal signal, as a function of the temperature of the different sub-systems; (iii) absolute and spectral responsivities of each of the spectrometric and photometric channels, as a function of the wavelength and position of the source in the field of view. Finally, we shall indicate the expected S/N ratios. 相似文献
777.
J.M. Lamarre J. Charlier 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1982,2(4):79-84
Infrared filters use a large variety of physical principles and techniques, as can be expected since they cover three decades of the IR spectrum (1 μm - 1 mm). The multilayer interference filters, derived from optical techniques, play the main role in the region 1 μm–40 μm. They have been successfully used in space applications. On the other side of the spectrum is the domain of metallic mesh filters, which is still developing. Bulk absorption, Reststrahlen bands, diffusion and gratings are also used to achieve the desired properties. A short review of this situation is given, with emphasis on the present trends and developments.Infrared and sub-millimeter filters use a large variety of physical principles and techniques that we may classify in two large families. 相似文献
778.
Pre-germinated pine seedlings and germinating oat and mung bean seeds were flown on the STS-3 Space Shuttle mission. Overall, the seedlings grew and developed well in space. Some oat and mung bean roots, however, grew upward. Lignin content was slightly lower in flight tissues and protein content was higher. 相似文献
779.
J. Blamont 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(9):193-197
Review of spectrometric and photometric measurements of recent comets from rockets and satellites. 相似文献
780.
E. Costa M. Salvati G. Agnetta R. Di Raffaele G. Gerardi B. Sacco L. Scarsi E. Massaro B. Agrinier J.C. Christi J.L. Masnou A. Bui-Van J.P. Chabaud P. Frabel P. Mandrou J. Narbonne M. Niel G. Rouaix G. Vedrenne 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(4):113-116
We present a large area, balloon borne, NaI(Tl) detector for low-energy gamma rays with temporal signature : FIGARO.The main detector is a mosaic of 12 NaI(Tl) tiles 22.5 × 15 × 5 cm, for a total geometric area of 4050 cm2.In the energy band 140 keV - 6 MeV, the expected background counting rate at float altitude is in the range of two to three thousands counts per second.For pulsar analysis the expected 3δ sensitivity for 5 hours exposition time is 2.5 10?4 ph/cm2.s.MeV (150–500 keV) 1.5 10?4 ph/cm2.s.MeV (1–6 MeV). This performance, together with the large effective area and the relatively short duration of a balloon flight, make FIGARO particularly suitable for the identification of sources by means of temporal analysis.For objectives in the Northern sky, including the Crab pulsar, a transmediterranean flight is planned for the summer of 1982 ; a Southern mission is scheduled in Brazil for the fall of 1983 (Vela, PSR 1822-09). 相似文献