全文获取类型
收费全文 | 7489篇 |
免费 | 21篇 |
国内免费 | 11篇 |
专业分类
航空 | 3374篇 |
航天技术 | 2650篇 |
综合类 | 197篇 |
航天 | 1300篇 |
出版年
2021年 | 65篇 |
2019年 | 41篇 |
2018年 | 157篇 |
2017年 | 101篇 |
2016年 | 99篇 |
2015年 | 50篇 |
2014年 | 189篇 |
2013年 | 203篇 |
2012年 | 216篇 |
2011年 | 291篇 |
2010年 | 200篇 |
2009年 | 339篇 |
2008年 | 422篇 |
2007年 | 200篇 |
2006年 | 175篇 |
2005年 | 222篇 |
2004年 | 191篇 |
2003年 | 243篇 |
2002年 | 247篇 |
2001年 | 303篇 |
2000年 | 116篇 |
1999年 | 176篇 |
1998年 | 205篇 |
1997年 | 146篇 |
1996年 | 184篇 |
1995年 | 221篇 |
1994年 | 205篇 |
1993年 | 108篇 |
1992年 | 160篇 |
1991年 | 77篇 |
1990年 | 61篇 |
1989年 | 142篇 |
1988年 | 64篇 |
1987年 | 71篇 |
1986年 | 65篇 |
1985年 | 197篇 |
1984年 | 174篇 |
1983年 | 136篇 |
1982年 | 161篇 |
1981年 | 211篇 |
1980年 | 68篇 |
1979年 | 52篇 |
1978年 | 51篇 |
1977年 | 42篇 |
1976年 | 45篇 |
1975年 | 43篇 |
1974年 | 55篇 |
1972年 | 46篇 |
1971年 | 42篇 |
1970年 | 41篇 |
排序方式: 共有7521条查询结果,搜索用时 0 毫秒
161.
G. Ohring P. Clapp T.R. Heddinghaus A.F. Krueger 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(4):305-308
Cloudiness modulates the radiation budget at the top of the Earth-atmosphere system. For radiation balance studies, for climate diagnostic studies, and for climate modeling studies, it is important to know the sensitivity of both the outgoing longwave radiation and the net (absorbed solar minus outgoing longwave) radiation of the system to changes in cloudiness on a global basis. Based on a 45 month series of NOAA satellite scanning radiometer observations, estimates of the global distribution of these sensitivity parameters are obtained. 相似文献
162.
163.
Kim N.P. Stanbery B.J. Burgess R.M. Mickelsen R.A. McClelland R.W. King B.D. Gale R.P. 《Aerospace and Electronic Systems Magazine, IEEE》1989,4(11):23-32
Mechanically stacked tandem cells consisting of GaAs thin-film upper cells and CuInSe2 thin-film lower cells have been developed to meet the increasing power needs projected for future spacecraft. The authors report the fabrication of the first highly efficient lightweight GaAs/CuInSe2 tandem cell on a 2-mil thick substrate, update recent performance improvements in thin-film GaAs/CuInSe2 tandem cells, and discuss their application to space power systems. The efficiency of 4-cm2 cells has improved to 21.6% AM0, the highest ever reported for a thin-film photovoltaic cell. Lightweight 4-cm2 tandem cells have been successfully fabricated with efficiencies as high as 20.8%. These cells weighed about 180 mg without optimized substrate trimming. Radiation and operating temperature effects on GaAs/CuInSe2 tandem cells are also discussed, and an interconnect scheme to form a voltage-matched string is described 相似文献
164.
Severns J.G. Hobbs R.M. Elliott N.P. Towsley R.H. Conway R.W. Virshup G.F. 《Aerospace and Electronic Systems Magazine, IEEE》1989,4(12):8-12
The LIPS III satellite, which was launched into a 1100-km circular orbit of 60° inclination in the spring of 1987, is discussed. LIPS III is a member of the living-plume-shield class of spacecraft, all of which were built around a simple sheet metal plume deflector. The purpose of LIPS III was to provide a testbed for space power sources. An overview of the LIPS III system is given, and the experiments submitted for it, all but one of which were photovoltaic in nature, are described 相似文献
165.
S.M.P. McKenna-Lawlor A.K. Richter 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1982,2(11):239-251
A sequence of six well defined interplanetary structures (magnetic clouds) was identified in the solar wind and magnetic field measurements of Helios-1 from 29 June-01 July, 1980. (location 0.64–0.67 AU, C. Long. ~165°, C. Lat. ~5.8°). These structures were characterized by a large northward directed solar wind flow; by well defined directional discontinuities of mainly the ‘tangential-type’ at their beginnings and ends; by some increase in proton and by very pronounced increases in alpha particle number densities - each accompanied by sudden temperature decreases (or in one case by an increase); by some times an increase in magnetic field strength and by values of Nα/Np typical of the inner solar atmosphere. These structures are suggested to have been ejections from a succession (27–29 June, 1980) of Type II producing flares in Hale Region 16923 which coronagraph and X-ray (GOES) data indicate constituted a family of transient producing events. Only two interplanetary shocks were identified in the relevant Helios-1 records. It is suggested on the basis of observations of the directionality of certain of the flare related Type II bursts that some of these shocks could have been missed by the spacecraft. This implies that, in the absence of directional information, correlation of an observed interplanetary shock wave with a solar Type II burst may not always lead to a unique result. 相似文献
166.
C.R. Philbrick M.E. Garnder P. Lämmerzhal 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(1):95-98
Measurements of the density and composition of the thermosphere between 150 and 500 km, which were obtained by the S3-1 satellite, have been compared with the Jacchia and MSIS models. The measurements of the densities of O, N2, N and Ar show some differences from the current models which should be considered during the preparation of the next CIRA model. The Ar measurements are particularly useful in examining the response of the neutral atmosphere to geomagnetic heating. These results are useful in establishing the appropriate lower boundary conditions for modeling of the thermosphere. 相似文献
167.
H. Stiller R. Knuth P. Bormann 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(7):95-101
Following a historical review of the first activities of GDR scientists in the fields of space research, especially on astronomical and geodetical satellite-observations and in atmospheric and magnetospheric research, the growing scientific and increasingly efficient technological and economic benefits of the cooperation of the Academy of sciences and other scientific and technological institutions of the GDR within the Intercosmos-programme are described. Especially, the experiences in connection with remote sensing, of the cooperation with countries as Cuba and the Peoples Republic of Vietnam and of the common USSR - GDR manned spaceflight are discussed under the viewpoint of the mutual interests of developing and developed countries in the fields of space science and technology. 相似文献
168.
K. Kecskeméty S. Pintér 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(3):101-104
Flux variations of 1 – 5 MeV protons are studied in energetic storm particle events with respect to the preshock solar wind plasma parameters and to the thickness of the collisionless interplanetary shock wave. It is found that the peak intensity in ESP events depends on pre-shock plasma density and on the thickness of the transition region. These relations predict, in agreement with recent observations, the increase of ESP events at larger heliocentric distances. 相似文献
169.
The multifunction display (MFD) developed for use as the primary cockpit display system on the US Air Force C-17A military air transport is described. The 6-in by 6-in color cathode ray tube (CRT) display features a self-contained 1750 processor and vector generator capable of processing MIL-STD-1553B aircraft data and raster video into any of 10 formats as selected by the pilot or copilot. The MFD can display stroke, raster, or hybrid formats in 16 colors. Raster images are driven by sensor inputs with an RS-170 or RS-343 interface. The CRT uses a taut mask delta gun design and provides the best available brightness and line-width performance. The display features small size, low weight, low power, standard interface, and adaptable software. Reconfigurability in the aircraft is enhanced by using four identical cockpit displays 相似文献
170.
J P Ferris H Yanagawa W J Hagan 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(9):61-68
Diiminosuccinonitrile (DISN) has been investigated as a potential prebiotic phosphorylating agent. It is formed readily by the oxidation of diaminomaleonitrile (DAMN), a tetramer of HCN. DISN effects the cyclization of 3'-adenosine monophosphate to adenosine 2',3'-cyclic phosphace in up to 40% yield. The DISN-mediated phosphorylation of uridine to uridine mono-phosphate does not proceed efficiently in aqueous solution. The reaction of DISN and BrCN with uridine-5'-phosphate and uridine results in the formation of 2,2'-anhydronucleotides and 2,2'-anhydronucleosides respectively, and other reaction products resulting from an initial reaction at the 2'- and 3'-hydroxyl groups. The clay mineral catalysis of the cyclization of adenosine-3'-phosphate was investigated using homoionic montmorillonites. 相似文献