全文获取类型
| 收费全文 | 2566篇 |
| 免费 | 3篇 |
| 国内免费 | 5篇 |
专业分类
| 航空 | 1266篇 |
| 航天技术 | 1020篇 |
| 综合类 | 5篇 |
| 航天 | 283篇 |
出版年
| 2021年 | 15篇 |
| 2019年 | 16篇 |
| 2018年 | 44篇 |
| 2017年 | 37篇 |
| 2016年 | 26篇 |
| 2015年 | 15篇 |
| 2014年 | 50篇 |
| 2013年 | 64篇 |
| 2012年 | 52篇 |
| 2011年 | 88篇 |
| 2010年 | 63篇 |
| 2009年 | 107篇 |
| 2008年 | 150篇 |
| 2007年 | 65篇 |
| 2006年 | 49篇 |
| 2005年 | 62篇 |
| 2004年 | 73篇 |
| 2003年 | 91篇 |
| 2002年 | 46篇 |
| 2001年 | 106篇 |
| 2000年 | 46篇 |
| 1999年 | 88篇 |
| 1998年 | 88篇 |
| 1997年 | 63篇 |
| 1996年 | 63篇 |
| 1995年 | 92篇 |
| 1994年 | 97篇 |
| 1993年 | 37篇 |
| 1992年 | 59篇 |
| 1991年 | 23篇 |
| 1990年 | 28篇 |
| 1989年 | 57篇 |
| 1988年 | 20篇 |
| 1987年 | 35篇 |
| 1986年 | 21篇 |
| 1985年 | 78篇 |
| 1984年 | 44篇 |
| 1983年 | 50篇 |
| 1982年 | 65篇 |
| 1981年 | 81篇 |
| 1980年 | 28篇 |
| 1979年 | 24篇 |
| 1978年 | 23篇 |
| 1977年 | 18篇 |
| 1976年 | 15篇 |
| 1975年 | 19篇 |
| 1974年 | 13篇 |
| 1972年 | 17篇 |
| 1969年 | 13篇 |
| 1966年 | 8篇 |
排序方式： 共有2574条查询结果，搜索用时 0 毫秒
991.
C. Elachi M. D. Allison L. Borgarelli P. Encrenaz E. Im M. A. Janssen W. T. K. Johnson R. L. Kirk R. D. Lorenz J. I. Lunine D. O. Muhleman S. J. Ostro G. Picardi F. Posa C. G. Rapley L. E. Roth R. Seu L. A. Soderblom S. Vetrella S. D. Wall C. A. Wood H. A. Zebker 《Space Science Reviews》2004,115(1-4):71-110
The Cassini RADAR instrument is a multimode 13.8 GHz multiple-beam sensor that can operate as a synthetic-aperture radar (SAR) imager, altimeter, scatterometer, and radiometer. The principal objective of the RADAR is to map the surface of Titan. This will be done in the imaging, scatterometer, and radiometer modes. The RADAR altimeter data will provide information on relative elevations in selected areas. Surfaces of the Saturn’s icy satellites will be explored utilizing the RADAR radiometer and scatterometer modes. Saturn’s atmosphere and rings will be probed in the radiometer mode only. The instrument is a joint development by JPL/NASA and ASI. The RADAR design features significant autonomy and data compression capabilities. It is expected that the instrument will detect surfaces with backscatter coefficient as low as −40 dB.RADAR Team LeaderThis revised version was published online in July 2005 with a corrected cover date. 相似文献
992.
E.G. Mullen M.S. Gussenhoven J.T. Bell D. Madden E. Holeman D. Delorey 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1998,21(12):1651-1660
Dosimeter data taken on the APEX (1994–1996), CRRES (1990–1991) and DMSP (1984–1987) satellites have been used to study the low altitude (down to 350 km) radiation environment. Of special concern has been the inner edge of the inner radiation belt due to its steep gradient. We have constructed dose models of the inner edge of the belt from all three spacecraft and put them into a personal computer utility, called APEXRAD, that calculates dose for user-selected orbits. The variation of dose for low altitude, circular orbits is given as a function of altitude, inclination and particle type. Dose-depth curves show that shielding greater than 1/4 in Al is largely ineffectual for low altitude orbits. The contribution of outer zone electrons to low altitude dose is shown to be important only for thin shields and to have significant variation with magnetic activity and solar cycle. 相似文献
993.
C. T. Russell B. J. Anderson W. Baumjohann K. R. Bromund D. Dearborn D. Fischer G. Le H. K. Leinweber D. Leneman W. Magnes J. D. Means M. B. Moldwin R. Nakamura D. Pierce F. Plaschke K. M. Rowe J. A. Slavin R. J. Strangeway R. Torbert C. Hagen I. Jernej A. Valavanoglou I. Richter 《Space Science Reviews》2016,199(1-4):189-256
The success of the Magnetospheric Multiscale mission depends on the accurate measurement of the magnetic field on all four spacecraft. To ensure this success, two independently designed and built fluxgate magnetometers were developed, avoiding single-point failures. The magnetometers were dubbed the digital fluxgate (DFG), which uses an ASIC implementation and was supplied by the Space Research Institute of the Austrian Academy of Sciences and the analogue magnetometer (AFG) with a more traditional circuit board design supplied by the University of California, Los Angeles. A stringent magnetic cleanliness program was executed under the supervision of the Johns Hopkins University’s Applied Physics Laboratory. To achieve mission objectives, the calibration determined on the ground will be refined in space to ensure all eight magnetometers are precisely inter-calibrated. Near real-time data plays a key role in the transmission of high-resolution observations stored on board so rapid processing of the low-resolution data is required. This article describes these instruments, the magnetic cleanliness program, and the instrument pre-launch calibrations, the planned in-flight calibration program, and the information flow that provides the data on the rapid time scale needed for mission success. 相似文献
994.
T. Yokoyama H. Nakajima K. Shibasaki V.F. Melnikov A.V. Stepanov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2003,32(12):2517-2520
We report a Nobeyama Radioheliograph (NoRH) microwave observation of a propagating feature of non thermal emission in a solar flare. The flare had a very extended source well resolved by NoRH. In the rising phase of the microwave burst, a non-thermal gyrosynchrotron source was observed by the high-rate (10 images per second) observations to propagate from one end of the loop to the other with a speed of 9 × 104 km s−1. We interpret this non-thermal propagating source is emitted from streaming electrons. 相似文献
995.
V.K. Golev I.M. Yancoulova G.T. Petrov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,3(10-12)
Based on the spectrophotometric data, by decomposition of the observed continuum, the power - law continuum characteristics of the central source are obtained. The behaviour of both electron temperature Te and density ne in the Narrow - Line Region (NLR) of NGC 7469 is discussed on the thermal and ionization equilibria calculations. Te in NLR of the Sy1 galaxies are higher than the Sy2 ones, and the possible explanation is the lack of the dense (ne 1010 cm−3) zone close to the central source in the Sy2 galaxies. 相似文献
996.
C. T. Bolton 《Space Science Reviews》1989,50(1-2):311-322
Variations in the magnetic pressure and flux blocking by starspots during the magnetic cycle of the cool semidetached component of an Algol binary may cause cyclic changes in the quadrupole moment and moment of inertia of the star which can cause alternate period changes. Since several different processes and timescales are involved, the orbital period changes may not correlate strongly with the indicators of magnetic activity. The structural changes in the semidetached component can also modulate the mass transfer rate. Sub-Keplerian velocities, supersonic turbulence, and high temperature regions in circumstellar material around the accreting star may all be a consequence of magnetic fields embedded in the flow. Models for the evolution of Algols which include the effects of angular momentum loss (AML) through a magnetized wind may have underestimated the AML rate by basing it on results from main sequence stars. Evolved stars appear to have higher AML rates, and there may be additional AML in a wind from the accretion disk. 相似文献
997.
998.
O. Moullard R.G. Marsden T.R. Sanderson C. Tranquille R.J. Forsyth B.E. Goldstein 《Space Science Reviews》2001,97(1-4):289-292
We present and compare observations of energetic protons during the two first transits of the Ulysses spacecraft from low to high latitudes in the southern heliosphere. Protons in the energy range 1.8–3.8 MeV from the COSPIN
experiment are studied for global trends and in relation to some ambient structures in the solar wind (corotating interaction
region, forward/reverse shock). The global trends show the large dependence on the heliospheric condition and solar activity,
including indications of a larger ambient particle population during the rising phase of solar activity and more efficient
solar wind particle accelerators during the declining phase. More enhancements in the proton flux intensity are time associated
with forward shocks than reverse contrary to first pass. Recurrent structures are found even during the second transit. Some
latitude dependent periodicities are observed that could relate to the differential solar rotation.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
999.
H. Nilsson E. Carlsson H. Gunell Y. Futaana S. Barabash R. Lundin A. Fedorov Y. Soobiah A. Coates M. Fränz E. Roussos 《Space Science Reviews》2006,126(1-4):355-372
Using data from the Mars Express Ion Mass Analyzer (IMA) we investigate the distribution of ion beams of planetary origin and search for an influence from Mars crustal magnetic anomalies. We have concentrated on ion beams observed inside the induced magnetosphere boundary (magnetic pile-up boundary). Some north-south asymmetry is seen in the data, but no longitudinal structure resembling that of the crustal anomalies. Comparing the occurrence rate of ion beams with magnetic field strength at 400 km altitude below the spacecraft (using statistical Mars Global Surveyor results) shows a decrease of the occurrence rate for modest (< 40 nT) magnetic fields. Higher magnetic field regions (above 40 nT at 400 km) are sampled so seldom that the statistics are poor but the data is consistent with some ion outflow events being closely associated with the stronger anomalies. This ion flow does not significantly affect the overall distribution of ion beams around Mars. 相似文献
1000.
M. A. Hapgood T. G. Dimbylow D. C. Sutcliffe P. A. Chaizy P. S. Ferron P. M. Hill X. Y. Tiratay 《Space Science Reviews》1997,79(1-2):487-525
The Joint Science Operations Centre (JSOC) has been established to provide the operational interface between the Instrument Principal Investigators (PIs) and the European Space Operations Centre (ESOC). Its key task will be to merge inputs from the Cluster instrument teams and to generate the coordinated command schedule for operation of the scientific payload. In addition, it will collect and process data needed to plan those operations and will monitor the performance of the mission and individual instruments. This paper outlines the JSOC subsystems that have been built to carry out these tasks and highlights points of scientific or technical interest within these systems. 相似文献