全文获取类型
收费全文 | 2283篇 |
免费 | 7篇 |
国内免费 | 3篇 |
专业分类
航空 | 1227篇 |
航天技术 | 833篇 |
综合类 | 13篇 |
航天 | 220篇 |
出版年
2018年 | 25篇 |
2017年 | 23篇 |
2014年 | 24篇 |
2013年 | 48篇 |
2012年 | 29篇 |
2011年 | 59篇 |
2010年 | 47篇 |
2009年 | 57篇 |
2008年 | 126篇 |
2007年 | 39篇 |
2006年 | 32篇 |
2005年 | 47篇 |
2004年 | 69篇 |
2003年 | 73篇 |
2002年 | 37篇 |
2001年 | 55篇 |
2000年 | 50篇 |
1999年 | 27篇 |
1998年 | 75篇 |
1997年 | 53篇 |
1996年 | 62篇 |
1995年 | 69篇 |
1994年 | 85篇 |
1993年 | 51篇 |
1992年 | 69篇 |
1991年 | 29篇 |
1990年 | 33篇 |
1989年 | 70篇 |
1988年 | 24篇 |
1987年 | 29篇 |
1986年 | 51篇 |
1985年 | 88篇 |
1984年 | 54篇 |
1983年 | 60篇 |
1982年 | 57篇 |
1981年 | 68篇 |
1980年 | 34篇 |
1979年 | 27篇 |
1978年 | 25篇 |
1977年 | 24篇 |
1975年 | 24篇 |
1974年 | 24篇 |
1973年 | 24篇 |
1972年 | 21篇 |
1971年 | 31篇 |
1970年 | 17篇 |
1969年 | 25篇 |
1968年 | 18篇 |
1967年 | 20篇 |
1966年 | 19篇 |
排序方式: 共有2293条查询结果,搜索用时 0 毫秒
191.
K. Frieler N. Phlippovich R. Stickler W. Bathke 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(5):117-120
Experiments of vacuum brazing under both microgravity and 1-g conditions show the effect of hydrostatic pressure on ga-filling. The absence of buoyancy forces under microgravity affects the microstructure of the solidified braze in the joint. 相似文献
192.
G.H. Schwehm R.H. Giese F. Giovane D.W. Schuerman J.L. Weinberg 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(8):121-125
The 1985 International Solar Polar Mission will provide the first opportunity to perform measurements from out of the ecliptic and from above the solar poles. Included in this mission is the Zodiacal Light/Background Starlight Experiment of the Ruhr-University Bochum, FRG (in collaboration with the State University of New York at Albany). The experiment is based on the use of a multicolor, sky-scanning photopolarimeter, which will be carried on the NASA S/C.The scientific objectives of the experiment are to investigate the intensity, polarization, and color of the diffuse sky brightness and determine the spatial distribution and physical properties of the interplanetary dust, including a possible interstellar component, as a function of S/C position in and out of the ecliptic.The instrument will allow simultaneous measurements in two separate wavelength bands. Measurements will be performed at 180, 220, 240, 280, 320, 350, 360, 440, 540, 640, 800 nm, including the state of polarization. Two different fields-of-view (1 sq deg and 5.6 sq deg) can be selected.The use of a microprocessor system in the instrument electronics will provide flexibility in measurement sequences and programs, on-board data processing and data quality control. 相似文献
193.
Many radio and sonar systems require signal outputs in complex low-pass form. To achieve this, it is possible to use uniform sampling of the bandpass signal, together with computation of the quadrature component by way of a Hilbert transform. The bandpass to low-pass translation is accomplished by undersampling. A hardware implementation is described which achieves 70 dB spurious-free dynamic range and a bandwidth of 30 kHz. 相似文献
194.
Equations are derived to predict the electrical behavior of a three-phase superconducting alternator connected to a full-wave bridge rectifier. This is accomplished by expanding a previous analysis for conventional rectified alternators and adding computational impovements. The significance of the work is that it provides a means of calculating certain critical variables such as the ac current in the superconducting field winding and the ac voltage harmonics at the rectified output. A numerical example based on a machine designed for airborne applications is included. 相似文献
195.
Organisms use gravity for spatial orientation, and differentiation into species during evolution follows geological processes which are caused by gravity. On the other hand, the task of most organismic functions which have or may have a relation to gravity is to compensate gravity. Furthermore, today it is very obvious that organisms do not disintegrate under the conditions of weightlessness, at least for the currently tested durations. These previous statements indicate a large field of still unknown regulation and adaptation mechanisms. Experiments to simulate weightlessness on the fast clinostat and with hyper-g show a highly developed ability of the genetic chain and of differentiating cells in being autonomous against mechanical stresses caused by outer accelerations. Nevertheless, different strong and slight changes of different tested end points were found. The question remains if the cells react actively or only passively. 相似文献
196.
197.
M.G. Kivelson K.W. Behannon T.E. Cravens I. de Pater T.V. Johnson D.L. Matson H. Masursky D.J. Southwood V.M. Vasyliunas 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(3):5-14
A was presented in conjunction with the Twenty-fourth Plenary Meeting of the Committee on Space Research. This paper summarizes the talks presented and places the remaining papers of this volume in context. 相似文献
198.
W.A. Gault G.G. Shepherd 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1982,2(7):111-114
A CCD imaging device has been designed which combines a spatial resolution of 0.1° with a spectral resolving power of 105, sufficient to measure Doppler shifts and line widths of individual atmospheric emission lines. It will be flown aboard Spacelab and will be used to study neutral winds and temperatures as functions of height, latitude and time of day. 相似文献
199.
Johnson S.D. Witulski A.F. Erickson R.W. 《IEEE transactions on aerospace and electronic systems》1988,24(3):263-274
Because of their tolerance of transformer nonidealities, resonant converters are considered to be well-suited to high-voltage applications. The series and parallel resonant topologies, as well as a newly discovered hybrid resonant topology are compared for high-voltage applications. Design criteria which incorporate transformer nonidealities are developed and used in the construction of high voltage prototypes for each topology. It is found that the parallel topology leads to the lowest peak switch current and the most ideal behavior 相似文献
200.
M. Grewing A. Vidal-Madjar A. Labeque C. Laurent A. Boksenberg C. Burgio S. di Serego Alighieri G.P. Whitcomb W. Burton C.I. Coleman R. Hoekstra C. Jamar J. Lequeux P. Rafanelli 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1982,2(4):147-151
Magellan is one of the future space projects being studied by the European Space Agency. The aim is to provide high resolution (λ/Δλ ≥ 2.5 × 104) spectra in the far and extreme UV (between 500 and 1550 Å) of faint galactic and extragalactic objects (V ≤ 16m). The instrument consists of a mechanical collimator, a concave holographic grating and a bidimensional photon-counting detector. A low resolution mode (λ/Δλ ≥ 103) will provide spectra of objects as faint as 18m.5. Magellan is planned as an observatory, operated in real time, and allowing interaction with the observer. 相似文献