全文获取类型
收费全文 | 17103篇 |
免费 | 28篇 |
国内免费 | 123篇 |
专业分类
航空 | 9723篇 |
航天技术 | 4900篇 |
综合类 | 235篇 |
航天 | 2396篇 |
出版年
2021年 | 154篇 |
2018年 | 165篇 |
2016年 | 149篇 |
2014年 | 432篇 |
2013年 | 513篇 |
2012年 | 398篇 |
2011年 | 547篇 |
2010年 | 385篇 |
2009年 | 742篇 |
2008年 | 772篇 |
2007年 | 341篇 |
2006年 | 415篇 |
2005年 | 346篇 |
2004年 | 396篇 |
2003年 | 462篇 |
2002年 | 451篇 |
2001年 | 507篇 |
2000年 | 337篇 |
1999年 | 434篇 |
1998年 | 375篇 |
1997年 | 294篇 |
1996年 | 331篇 |
1995年 | 406篇 |
1994年 | 351篇 |
1993年 | 349篇 |
1992年 | 264篇 |
1991年 | 246篇 |
1990年 | 231篇 |
1989年 | 360篇 |
1988年 | 198篇 |
1987年 | 229篇 |
1986年 | 222篇 |
1985年 | 636篇 |
1984年 | 507篇 |
1983年 | 391篇 |
1982年 | 485篇 |
1981年 | 605篇 |
1980年 | 243篇 |
1979年 | 182篇 |
1978年 | 189篇 |
1977年 | 144篇 |
1976年 | 155篇 |
1975年 | 181篇 |
1974年 | 180篇 |
1973年 | 161篇 |
1972年 | 188篇 |
1971年 | 148篇 |
1970年 | 143篇 |
1969年 | 147篇 |
1967年 | 142篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
241.
242.
We present up-to-date evolutionary models of low-mass stars, from M0.6 M down to the hydrogen burning minimum mass, using recent equation of state and synthetic spectra calculations. Comparison is made with observed luminosity function for these objects. We also present implications for the dark-matter distribution in the galactic halo. 相似文献
243.
J. L. Phillips S. J. Bame S. P. Gary J. T. Gosling E. E. Scime R. J. Forsyth 《Space Science Reviews》1995,72(1-2):109-112
Ulysses plasma measurement from 1.15 to 5.31 AU and from S6.4° to S48.3° solar latitude are used to assess the trends in the solar wind thermal electron temperature and anisotropy. Improved spacecraft potential corrections and data products have been incorporated. The radial temperature gradient is steeper than in previous determinations, but flatter than adiabatic. When normalized to 1 AU, temperature decrease with increasing latitude. Little change in the average thermal anisotropy has been seen during the mission. 相似文献
244.
M. Pick A. Buttighoffer A. Kerdraon T. P. Armstrong E. C. Roelof S. Hoang L. J. Lanzerotti G. M. Simnett J. Lemen 《Space Science Reviews》1995,72(1-2):315-320
A remarkable streaming beam-like particle event of 60 keV-5 MeV ions and of 38–315 keV electrons has been reported previously. This event has been associated with the passage of a Coronal Mass Ejection (CME) over the Ulysses spacecraft on June 9–13, 1993. At this time, the spacecraft was located at 4.6 AU from the sun and at an heliolatitude of 32° south. It was proposed (Armstrong et al., 1994) that the particle injection source could have been of coronal origin. In this study, we analyse the solar activity during this period. We identify a region of solar radio noise storms in the corona and in particular, a flare on June 7 that presents all the required characteristics to produce the hot plasma beam observed in the interplanetary medium. 相似文献
245.
A. Raviart R. Ducros P. Ferrando C. Rastoin B. Heber H. Kunow R. Müller-Mellin H. Sierks G. Wibberenz C. Paizis 《Space Science Reviews》1995,72(1-2):409-414
We describe for the first time the analysis of high energy electrons (above 240 MeV) from the COSPIN/KET experiment onboard Ulysses. The electron time profiles in four energy windows are presented from Oct. 90 to the end of March 94, up to a maximum heliographic latitude of 57 °S. The recovery rates we derived for the electrons are compared to the recovery rates of positively charged particles with the same rigidity. 相似文献
246.
J. T. Gosling S. J. Bame D. J. McComas J. L. Phillips V. J. Pizzo B. E. Goldstein M. Neugebauer 《Space Science Reviews》1995,72(1-2):99-104
Ulysses plasma observations reveal that the forward shocks that commonly bound the leading edges of corotating interaction regions (CIRs) beyond 2 AU from the Sun at low heliographic latitudes nearly disappeared at a latitude of S26°. On the other hand, the reverse shocks that commonly bound the trailing edges of the CIRs were observed regularly up to S41.5°, but became weaker with increasing latitude. Only three CIR shocks have been observed poleward of S41.5°; all of these were weak reverse shocks. The above effects are a result of the forward waves propagating to lower heliographic latitudes and the reverse waves to higher latitudes with increasing heliocentric distance. These observational results are in excellent agreement with the predictions of a global model of solar wind flows that originate in a simple tilted-dipole geometry back at the Sun. 相似文献
247.
SWE,a comprehensive plasma instrument for the WIND spacecraft 总被引:1,自引:0,他引:1
K. W. Ogilvie D. J. Chornay R. J. Fritzenreiter F. Hunsaker J. Keller J. Lobell G. Miller J. D. Scudder E. C. Sittler Jr. R. B. Torbert D. Bodet G. Needell A. J. Lazarus J. T. Steinberg J. H. Tappan A. Mavretic E. Gergin 《Space Science Reviews》1995,71(1-4):55-77
The Solar Wind Experiment (SWE) on the WIND spacecraft is a comprehensive, integrated set of sensors which is designed to investigate outstanding problems in solar wind physics. It consists of two Faraday cup (FC) sensors; a vector electron and ion spectrometer (VEIS); a strahl sensor, which is especially configured to study the electron strahl close to the magnetic field direction; and an on-board calibration system. The energy/charge range of the Faraday cups is 150 V to 8 kV, and that of the VEIS is 7 V to 24.8 kV. The time resolution depends on the operational mode used, but can be of the order of a few seconds for 3-D measurements. Key parameters which broadly characterize the solar wind positive ion velocity distribution function will be made available rapidly from the GGS Central Data Handling Facility. 相似文献
248.
Timothy G. Hawarden Robert Crane Harley A. Thronson Jr. Alan J. Penny Anna H. Orlowska Thomas W. Bradshaw 《Space Science Reviews》1995,74(1-2):45-56
The designs of cold space telescopes, cryogenic and radiatively cooled, are similar in most elements and both benefit from orbits distant from the Earth. In particular such orbits allow the anti-sunward side of radiatively-cooled spacecraft to be used to provide large cooling radiators for the individual radiation shields. Designs incorporating these features have predictedT
tel near 20 K. The attainability of such temperatures is supported by limited practical experience (IRAS, COBE). Supplementary cooling systems (cryogens, mechanical coolers) can be advantageously combined with radiative cooling in hybrid designs to provide robustness against deterioration and yet lower temperatures for detectors, instruments, and even the whole telescope. The possibility of such major additional gains is illustrated by the Very Cold Telescope option under study forEdison, which should offerT
tel5 K for a little extra mechanical cooling capacity. 相似文献
249.
We review work on diffusion coefficients of energetic particles with an attempt to extract implications on their behaviour at high latitudes. In the ecliptic plane results from solar energetic particle propagation between the Sun and about 5 AU can be described by an effective radial mean free path
r
which is approximately constant as a function of distancer. When particle propagation in three dimensions in the heliosphere is considered it is not sufficient to consider
r
only. Jovian electrons can be used as probes to determine the parameters of three-dimensional diffusion. In the polar regions diffusion is dominated by its parallel component. Some predictions how should vary with latitude are discussed. For different choices of this variation we present expectations for intensity-time profiles of solar particle events during the Ulysses polar passages. 相似文献
250.
We report the discovery that for latitudes above 40°S, the observed recurring modulation of cosmic rays and anomalous nuclei occurs without the detection byUlysses of the solar wind velocity and magnetic field recurring enhancements that have, heretofore at lower latitudes, defined corotating interaction regions—i.e., the mechanism producing the recurring intensity variations >40°S appears to be located beyond the radial range ofUlysses. 相似文献