全文获取类型
收费全文 | 6144篇 |
免费 | 20篇 |
国内免费 | 17篇 |
专业分类
航空 | 2912篇 |
航天技术 | 2190篇 |
综合类 | 23篇 |
航天 | 1056篇 |
出版年
2021年 | 58篇 |
2019年 | 32篇 |
2018年 | 125篇 |
2017年 | 83篇 |
2016年 | 86篇 |
2015年 | 45篇 |
2014年 | 166篇 |
2013年 | 167篇 |
2012年 | 176篇 |
2011年 | 255篇 |
2010年 | 169篇 |
2009年 | 278篇 |
2008年 | 347篇 |
2007年 | 164篇 |
2006年 | 139篇 |
2005年 | 172篇 |
2004年 | 156篇 |
2003年 | 210篇 |
2002年 | 117篇 |
2001年 | 191篇 |
2000年 | 102篇 |
1999年 | 136篇 |
1998年 | 171篇 |
1997年 | 119篇 |
1996年 | 142篇 |
1995年 | 188篇 |
1994年 | 170篇 |
1993年 | 105篇 |
1992年 | 147篇 |
1991年 | 75篇 |
1990年 | 55篇 |
1989年 | 130篇 |
1988年 | 59篇 |
1987年 | 62篇 |
1986年 | 56篇 |
1985年 | 164篇 |
1984年 | 128篇 |
1983年 | 116篇 |
1982年 | 135篇 |
1981年 | 177篇 |
1980年 | 59篇 |
1979年 | 61篇 |
1978年 | 55篇 |
1977年 | 45篇 |
1976年 | 47篇 |
1975年 | 41篇 |
1974年 | 41篇 |
1972年 | 35篇 |
1970年 | 36篇 |
1969年 | 34篇 |
排序方式: 共有6181条查询结果,搜索用时 156 毫秒
951.
952.
953.
Accurate solutions of minimal time Earth-Mars and Earth-Venus heliocentric trajectories are calculated with a shooting-Newton method. The flight times are less and the steering histories are diferent than those presented in [1], thus contradicting the optimality claims in [1]. 相似文献
954.
R.B. Stoltzfus S.A. Bowhill L.G. Smith 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(6):143-146
The Langmuir-probe technique for measurement of electron concentration in the mesosphere is capable of excellent altitude resolution, of order 1 m. Measurements from nine rocket flights frequently show small-scale ionization structures in the altitude region 60–90 km. These are believed to be identical with regions of strong coherent backscatter seem by VHF radars at Jicamarca, Peru and Urbana, Illinois. They are believed to represent intermittent turbulence attributable to nonlinear interaction of waves in the mesosphere. Parameters of the turbulent regions are estimated. 相似文献
955.
Charles F. Lillie Charles W. Hord Kevin Pang David L. Coffeen James E. Hansen 《Space Science Reviews》1977,21(2):159-181
The Voyager Photopolarimeter Experiment is designed to determine the physical properties of particulate matter in the atmospheres of Jupiter, Saturn, and the Rings of Saturn by measuring the intensity and linear polarization of scattered sunlight at eight wavelengths in the 2350–7500 Å region of the spectrum. The experiment will also provide information on the texture and probable composition of the surfaces of the satellites of Jupiter and Saturn and the properties of the sodium cloud around Io. During the planetary encounters a search for optical evidence of electrical discharges (lightning) and auroral activity will also be conducted. 相似文献
956.
V A Sarychev V V Sazonov A S Zlatorunsky S F Khlopina A D Egorov V I Somov 《Acta Astronautica》1980,7(6):719-730
The problem considered in this paper is the investigation of the properties of a mass-meter, i.e. the device for determining the mass of cosmonaut's body under zero-gravity conditions. The estimates of accuracy of mass measurement by this device are given, and the results of measuring the masses of cosmonauts' bodies on the Salyut 5 and 6 orbital stations are presented. 相似文献
957.
Cole S.N. Sjoberg E.S. Fanuele M.A. Rittenbach O.E. Olesch R.G. 《IEEE transactions on aerospace and electronic systems》1979,(5):594-599
The environment and radar operation simulator (EROS) is a hardware system whose function is to produce realistic synthetic radar backscatter, incorporating both target and clutter. The simulator is electrically connected to a subject radar and responds in real time to the radar's antenna scan angle by producing the correct composite video signal. 相似文献
958.
A unified approach to model-reference adaptive control systems is presented. A linearized error equation for each adaptive system is derived about some operating point and converted into the standard form for plotting root loci. The contribution made here is to convert the selection of an adaptive technique and the choosing of adaptive coefficients for some desired system performance from a "mystical art" to standard control techniquess. 相似文献
959.
Ramachandra K.V. Srinivasan V.S. 《IEEE transactions on aerospace and electronic systems》1977,(4):419-423
An X, Y, Z Kalman tracking filter is described and its steady state characteristics are analytically determined when the radar sensor meaures range, bearing, and elevation (?, ?, ?) at uniform intervals of time, T seconds. The relationship between the quantities measured by the sensor (?, ?,?) and the Cartesian coordinate system (X, Y, Z) is explicitly considered. 相似文献
960.