全文获取类型
收费全文 | 4860篇 |
免费 | 25篇 |
国内免费 | 19篇 |
专业分类
航空 | 2150篇 |
航天技术 | 1689篇 |
综合类 | 11篇 |
航天 | 1054篇 |
出版年
2021年 | 42篇 |
2019年 | 27篇 |
2018年 | 112篇 |
2017年 | 94篇 |
2016年 | 82篇 |
2015年 | 43篇 |
2014年 | 117篇 |
2013年 | 137篇 |
2012年 | 129篇 |
2011年 | 193篇 |
2010年 | 144篇 |
2009年 | 229篇 |
2008年 | 256篇 |
2007年 | 155篇 |
2006年 | 112篇 |
2005年 | 142篇 |
2004年 | 139篇 |
2003年 | 166篇 |
2002年 | 112篇 |
2001年 | 180篇 |
2000年 | 94篇 |
1999年 | 96篇 |
1998年 | 117篇 |
1997年 | 84篇 |
1996年 | 128篇 |
1995年 | 145篇 |
1994年 | 135篇 |
1993年 | 64篇 |
1992年 | 100篇 |
1991年 | 43篇 |
1990年 | 43篇 |
1989年 | 101篇 |
1988年 | 39篇 |
1987年 | 39篇 |
1986年 | 49篇 |
1985年 | 139篇 |
1984年 | 117篇 |
1983年 | 82篇 |
1982年 | 96篇 |
1981年 | 148篇 |
1980年 | 32篇 |
1979年 | 30篇 |
1978年 | 33篇 |
1977年 | 36篇 |
1976年 | 23篇 |
1975年 | 39篇 |
1974年 | 35篇 |
1973年 | 28篇 |
1970年 | 22篇 |
1969年 | 22篇 |
排序方式: 共有4904条查询结果,搜索用时 46 毫秒
741.
During strong magnetic storms in July and November of 2004 the fluxes of trapped particles (protons and electrons of MeV energies)
in the Earth’s radiation belts have increased by orders of magnitude and then decreased remaining on an enhanced level for
several months. These enhancements allowed us to study the processes of relaxation of the radiation belts. Measurements of
energetic particles by low-altitude satellites Coronas-F and Servis-1 have shown that predictions of the theory about the rate of pitch-angle diffusion are not always correct, giving both overestimated
and underestimated values for the lifetime of energetic particles. 相似文献
742.
The observation of the galactic anticenter region by the balloon borne gamma-ray telescope Natalya-I
A.F. Iyudin V.G. Kirillov-Ugryumov Yu.D. Kotov Yu.V. Smirnov L.V. Kurnosova M.I. Fradkin S.V. Damle B.V. Sreekantan G.S. Gokhale P.K. Kunte 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(4):53-56
This paper presents the results of measurements of gamma radiation with energies above 5 MeV, from the galactic anticenter region. The balloon-borne gamma ray telescope “Natalya-I”, was launched on 6 November, 1980 from the Tata Institute of Fundamental Research's Balloon Facility (Hyderabad, India) and reached ceiling altitude of 35 km. The results on the accelerator calibration of the telescope, using a “tagged” gamma ray beam are also presented. 相似文献
743.
E V Benton 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1986,6(11):315-328
Measurements of the radiation environment aboard U.S. and Soviet manned spacecraft are reviewed and summarized. Data obtained mostly from passive and some active radiation detectors now exist for the case of low Earth-orbit missions. Major uncertainties still exist for space exposure in high altitude, high inclination, geostationary orbits, in connection with solar effects and that of shielding. Data from active detectors flown in Spacelabs 1 and 2 suggest that a variety of phenomena must be understood before the effects of long-term exposure at the space-station type of orbit and shielding can be properly assessed. 相似文献
744.
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
745.
746.
I. Kutiev P. Marinov K.B. Serafimov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(1):119-121
A set of data including over 1400 transition level (TL) encounters of the OGO-6 satellite is used to construct analytical presentations of this altitude upon dip-latitude and longitude. The formula represents the TL variation between ± 50° dip-latitude and 20 h and 04 h local time interval. The data were obtained in the high solar activity period in 1969 and 1970. 相似文献
747.
The bandwidth of adaptive arrays with tapped delay lines behind the elements is examined. Such processing offers improved bandw over that attainable with quadrature hybrid processing. The performance of a two-element array with four types of processing (equarature hybrids, single delay lines, 3-tap delay lines, and 5-tap delay lines) is compared. It is shown that with half-wavelength element spacing, a quadrature hybrid and single delay-line processor are inadequate at 10-percent bandwidth. A 3-tap processor is adeq however, up to 40-percent bandwidth. 相似文献
748.
K.Ya. Kondratyev N.I. Moskalenko 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(8):53-58
The models of chemical composition and structure of the Earth-type planetary atmospheres are offered. The optical properties of gaseous and disperse phases of the atmospheres are investigated. 相似文献
749.
James M. Russell Ellis E. Remsberg John C. Gille Larry L. Gordley 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(4):271-277
The Limb Infrared Monitor of the Stratosphere (LIMS) experiment is a limb scanning infrared sounder designed to measure vertical temperature profiles and the concentrations of key chemical compounds which are important in the stratospheric ozone-nitrogen photochemistry. This paper describes results from the O3 and HNO3 channels with emphasis on validation of the data. Similar discussions of results from the other channels are presented in two companion papers published in these proceedings. 相似文献
750.
M. Kalinkov K. Stavrev I. Kuneva 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,3(10-12)
An attempt is made to compare optical properties of Abell clusters with X-ray sources. 相似文献