全文获取类型
收费全文 | 6952篇 |
免费 | 1006篇 |
国内免费 | 1067篇 |
专业分类
测绘学 | 232篇 |
大气科学 | 1225篇 |
地球物理 | 2528篇 |
地质学 | 2829篇 |
海洋学 | 467篇 |
天文学 | 618篇 |
综合类 | 477篇 |
自然地理 | 649篇 |
出版年
2024年 | 31篇 |
2023年 | 105篇 |
2022年 | 238篇 |
2021年 | 300篇 |
2020年 | 243篇 |
2019年 | 269篇 |
2018年 | 335篇 |
2017年 | 327篇 |
2016年 | 344篇 |
2015年 | 294篇 |
2014年 | 365篇 |
2013年 | 343篇 |
2012年 | 322篇 |
2011年 | 337篇 |
2010年 | 341篇 |
2009年 | 347篇 |
2008年 | 295篇 |
2007年 | 293篇 |
2006年 | 219篇 |
2005年 | 206篇 |
2004年 | 172篇 |
2003年 | 147篇 |
2002年 | 165篇 |
2001年 | 160篇 |
2000年 | 184篇 |
1999年 | 263篇 |
1998年 | 214篇 |
1997年 | 205篇 |
1996年 | 207篇 |
1995年 | 178篇 |
1994年 | 138篇 |
1993年 | 153篇 |
1992年 | 110篇 |
1991年 | 101篇 |
1990年 | 55篇 |
1989年 | 104篇 |
1988年 | 77篇 |
1987年 | 63篇 |
1986年 | 53篇 |
1985年 | 40篇 |
1984年 | 49篇 |
1983年 | 42篇 |
1982年 | 47篇 |
1981年 | 35篇 |
1980年 | 38篇 |
1979年 | 45篇 |
1978年 | 41篇 |
1977年 | 30篇 |
1974年 | 32篇 |
1971年 | 29篇 |
排序方式: 共有9025条查询结果,搜索用时 15 毫秒
1.
Kunde Yang Yuanliang Ma Chao Sun Miller J.H. Potty G.R. 《Oceanic Engineering, IEEE Journal of》2004,29(4):964-972
This paper discusses the results of geoacoustic inversion carried out using explosive charge data from the Asian Seas International Acoustic Experiment (ASIAEX) East China Sea (ECS) Experiment. A multifrequency incoherent matched-field inversion processor and a genetic algorithm (GA) are used for the inversion. A multistep matched field inversion approach is presented, which makes use of the varying sensitivities of wave fields at various frequencies to reduce the inversion problem into a sequence of smaller inversions with fewer unknowns to estimate at each stage. Different parameters are estimated using data at different frequencies according to their sensitivities. Inversion results for different areas in the ECS region are summarized and compared with core data. 相似文献
2.
G. Djurašević P. Rovithis H. Rovithis-Livaniou E. Fragoulopoulou 《Astrophysics and Space Science》2005,296(1-4):311-314
BV light curves of the eclipsing binary UV Leo obtained at the Kryonerion Astronomical Station of the National Observatory of
Athens, Greece, are analyzed. The analysis is based on a Roche configuration with two spots on the secondary surface. The
elements of the two components of the system are calculated and the spot characteristics are given. 相似文献
3.
F.Z. Feygin YU.P. Kurchashov V.A. Troitskaya K. Dobeš 《Planetary and Space Science》1985,33(3):271-273
A high resolution numerical sonagram of Pc-1 magnetic record has shown that single narrow lines of Pc-1 spectra produce lower frequency (“red-shifted”) satellite lines more than twice as often as their higher frequency (“violet”) counterparts. The violet satellites usually emerge only when at least two ancestor lines are present simultaneously. 相似文献
4.
Michael Boylan-Kolchin Chung-Pei Ma Eliot Quataert 《Monthly notices of the Royal Astronomical Society》2005,362(1):184-196
We carry out numerical simulations of dissipationless major mergers of elliptical galaxies using initial galaxy models that consist of a dark matter haloes and a stellar bulge with properties consistent with the observed fundamental plane. By varying the density profile of the dark matter haloes [standard Navarro, Frenk & White (NFW) profile versus adiabatically contracted NFW profile], the global stellar to dark matter mass ratio and the orbit of the merging galaxies, we are able to assess the impact of each of these factors on the structure of the merger remnant. Our results indicate that the properties of the remnant bulge depend primarily on the angular momentum and energy of the orbit; for a cosmologically motivated orbit, the effective radius and velocity dispersion of the remnant bulge remain approximately on the fundamental plane. This indicates that the observed properties of elliptical galaxies are consistent with significant growth via late dissipationless mergers. We also find that the dark matter fraction within the effective radius of our remnants increases after the merger, consistent with the hypothesis that the tilt of the fundamental plane from the virial theorem is due to a varying dark matter fraction as a function of galaxy mass. 相似文献
5.
6.
The behaviour of the flare in the period of enhancement and maximum of hard X-ray, microwave and decimetric type IV continuum is analysed. The elongation of the H ribbons and microwave source disclose that the energy release site was shifting through a system of loops with a velocity less than 200 km s-1, and that the energy was carried down the field lines with a velocity of about 1000 km s-1, implying the thermal conduction front mechanism of energy transport. Several processes of energy release are considered and it is concluded that an explanation in terms of succeeding interactions of neighbouring loops, involving fast reconnection of their poloidal components is in best agreement with the observations.Proceedings of the Second CESRA Workshop on Particle Acceleration and Trapping in Solar Flares, held at Aubigny-sur-Nère (France), 23–26 June, 1986. 相似文献
7.
Milan Burša 《Studia Geophysica et Geodaetica》1991,35(3):145-150
Summary The estimate of the tidal long-term decrease in the angular velocity of the Earth's rotation due to the Sun is given as –(0.8±0.3)×10
–22
rad s
–2. It was computed on the basis of the observed total long-term decrease in , of the observed tidal deceleration of the Moon and the observed decrease in the second-degree zonal Stokes geopotential harmonic term. Adopting the estimate given, the product of the Love number and the tidal phase lag angle due to the Sun (in degrees) comes out as 0.53±0.20.
am a z nuuu u z mu au u, az : –(0,8±0,3) 10 –22 a¶rt; –2 . ¶rt; ua n a¶rt;a u , n a¶rt;a nuu u ¶rt;z ¶rt;uu u n a¶rt;a u mz az znmuaz naama ma. u num n au, m nu¶rt;u ua a a z u ( za¶rt;a) a z nuua a (0,53±0,20).相似文献
8.
M. Burša 《Studia Geophysica et Geodaetica》1991,35(2):61-74
Summary It has been shown that dynamically, on the basis of the distribution of angular momenta, the Jovian system cannot be considered an analogue within the Solar system. The total tidal decrease in the angular momentum of Jupiter and in its angular velocity of rotation have been estimated, as well as the loss of mechanical energy due to tidal dissipation. It has been concluded that there are no dynamical contradictions with the hypothesis of the common cosmogonic origin of Jupiter and of its eight close satellites.
aam, m ¶rt;uauu, n an¶rt;u m uma ¶rt;uu, um numa umam aayu um. a a y au ma uma ¶rt;uu numa u z mu z au u—a nuuz mu, ma a nmu au yuu um u—a ¶rt;uunauu. a au, m m ¶rt;uauu azau zunm m zuu aaa numa u z uau u nmu.相似文献
9.
Jan Palouš 《Astrophysics and Space Science》1986,128(1):151-156
The relation between molecular clouds, star clusters, and the stellar component of the galactic disk is investigated. According to Elmegreen (1985) bound stellar systems, e.g., open star clusters, can be formed from molecular cloud of mass 104
M
. A close encounter with a giant molecular cloud or massive black hole disrupts such stellar systems and forms superclusters. This explains why some open star clusters are so mass-deficient. Unbound stellar systems, e.g., expanding OB associations, are formed from molecular clouds of mass 105
M
. When disruptive O-type stars appear the star formation is halted and the cloud is destroyed. An example of the relict of GMC disruption in the solar vicinity is Gould's belt. The velocity dispersion-versus-age relation is also investigated and explained as a consequence of gravitational scattering of stars on GMC, or massive black holes, or as due to recurrent transient spirals.Paper presented at a Workshop on The Role of Dust in Dense Regions of Interstellar Matter, held at Georgenthal, G.D.R., in March 1986. 相似文献
10.