全文获取类型
收费全文 | 499篇 |
免费 | 27篇 |
国内免费 | 45篇 |
专业分类
航空 | 291篇 |
航天技术 | 124篇 |
综合类 | 31篇 |
航天 | 125篇 |
出版年
2022年 | 2篇 |
2021年 | 7篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 34篇 |
2017年 | 22篇 |
2016年 | 4篇 |
2015年 | 11篇 |
2014年 | 16篇 |
2013年 | 30篇 |
2012年 | 23篇 |
2011年 | 25篇 |
2010年 | 27篇 |
2009年 | 42篇 |
2008年 | 23篇 |
2007年 | 26篇 |
2006年 | 21篇 |
2005年 | 25篇 |
2004年 | 22篇 |
2003年 | 15篇 |
2002年 | 10篇 |
2001年 | 15篇 |
2000年 | 14篇 |
1999年 | 14篇 |
1998年 | 11篇 |
1997年 | 15篇 |
1996年 | 16篇 |
1995年 | 10篇 |
1994年 | 14篇 |
1993年 | 10篇 |
1992年 | 7篇 |
1991年 | 1篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 9篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有571条查询结果,搜索用时 31 毫秒
171.
对远场的相速特性作了较详细的分析。文中首先从电磁场有限元出发对轴向和径向上的似稳态场相速度作了仿真研究,发现其在空间某些位置上具有稳定的相速,与波特点相似。同时分析了参数μ,σ,f对相速的影响。结果表明,其与电磁波在良导体中传播规律的定性分析相符。最后本文还对瞬态激励下的远场涡流效应作了一定分析,结果再次证明其具有似波特性。 相似文献
172.
173.
174.
175.
J. G. Trotignon J. L. Michau D. Lagoutte M. Chabassière G. Chalumeau F. Colin P. M. E. Décréau J. Geiswiller P. Gille R. Grard T. Hachemi M. Hamelin A. Eriksson H. Laakso J. P. Lebreton C. Mazelle O. Randriamboarison W. Schmidt A. Smit U. Telljohann P. Zamora 《Space Science Reviews》2007,128(1-4):713-728
The main objective of the Mutual Impedance Probe (MIP), part of the Rosetta Plasma Consortium (RPC), is to measure the electron
density and temperature of Comet 67P/Churyumov-Gerasimenko’s coma, in particular inside the contact surface. Furthermore,
MIP will determine the bulk velocity of the ionised outflowing atmosphere, define the spectral distribution of natural plasma
waves, and monitor dust and gas activities around the nucleus. The MIP instrumentation consists of an electronics board for
signal processing in the 7 kHz to 3.5 MHz range and a sensor unit of two receiving and two transmitting electrodes mounted
on a 1-m long bar. In addition, the Langmuir probe of the RPC/LAP instrument that is at about 4 m from the MIP sensor can
be used as a transmitter (in place of the MIP ones) and MIP as a receiver in order to have access to the density and temperature
of plasmas at higher Debye lengths than those for which the MIP is originally designed. 相似文献
176.
177.
Thérèse Encrenaz 《Space Science Reviews》1984,38(1-2):35-87
Our knowledge of the primordial matter from the objects of the outer solar system has made a considerable progress over the past years, in spite of the lack of any in situ measurements of these objects at the present time. The recent progress of ground-based instrumentation and the launch of the two Voyager fly-by missions have provided a huge amount of new informations about the origin and the evolution of the primitive Solar System objects.The most significant discoveries concerning the atmospheres of the Giant Planets can be summarized as follows: (1) there does not seem to be any differentiation in the internal structure of Jupiter during the planet's history; thus, the H2/He ratio measured on Jupiter seems to be representative of the H/He ratio of the Primordial Nebula; (2) there is some evidence for a helium differentiation, relative to hydrogen, in Saturn's interior; (3) there seems to be a carbon enrichment on both Jupiter and Saturn by a factor about 2; this result is consistent with a model in which the planetary core is formed first, and the atmosphere accreted by this core in a second stage; (4) the D/H ratio measured on Jupiter should be representative of the D/H value in the Primordial Nebula, 4.5 billion years ago; this value is 2 to 5 times larger than the mean value measured in the local interstellar medium now; (5) Titan's atmosphere is dominated by nitrogen and contains traces of organic and prebiotic molecules (HCN, C2N2, HC3N); the chemical composition of Titan's atmosphere could be favorable for the early stages of life development.The small bodies of the Solar System — asteroïds and comets — are still very poorly known. However they contain a key information about the physical and chemical properties of dust in the Primordial Nebula and the interstellar medium. With the launch of expected fly-by missions towards Comet Halley and, possibly, towards asteroïds, we may hope to know a new development of our understanding of these objects, comparable to the progress we have known on the Giant Planets over the past ten years. 相似文献
178.
E. Illés A. Horváth 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(8):49-52
L-grooves are the consequence of layered structure of Phobos, which are made up of parallel layers of different composition or hardness. 相似文献
179.
Pierre Léna 《Space Science Reviews》1970,11(1):131-151
Transition between high altitude manned observatories and unmanned balloon-borne or rocket-borne experiments is achieved with high flying aircrafts, at altitudes above tropopause (>12 km), which became readily available, at reasonable cost and reliability, in the past five or ten years.This paper reviews the development of scientific uses of aircrafts, especially for astronomy and geophysics, with some emphasis placed on infrared problems, closely related to the scale height of the chief infrared absorber, i.e. telluric water vapor.Absorbers distribution vs altitude and spectral characteristics are summarized (Figures 1, 2, 3).Capabilities of various available aircrafts are compared (Table I) and the various ways to consider modifications are discussed: structural modifications or design problems to fit telescopes or light collectors on board. Tables II and III list the advantages of airborne observations, compared to other spatial carriers, and also the specific problems connected with aircrafts. Adopted solutions to these problems are exposed (Figures 4, 5, 6, 7) and costs are briefly discussed.Finally, a few examples of scientific results, gathered in the few past years from aircraft, are given, both in astronomy and in geophysics. 相似文献
180.