全文获取类型
| 收费全文 | 26741篇 |
| 免费 | 511篇 |
| 国内免费 | 352篇 |
专业分类
| 测绘学 | 758篇 |
| 大气科学 | 1908篇 |
| 地球物理 | 5143篇 |
| 地质学 | 9286篇 |
| 海洋学 | 2377篇 |
| 天文学 | 6652篇 |
| 综合类 | 61篇 |
| 自然地理 | 1419篇 |
出版年
| 2021年 | 237篇 |
| 2020年 | 273篇 |
| 2019年 | 333篇 |
| 2018年 | 652篇 |
| 2017年 | 627篇 |
| 2016年 | 779篇 |
| 2015年 | 452篇 |
| 2014年 | 743篇 |
| 2013年 | 1373篇 |
| 2012年 | 854篇 |
| 2011年 | 1110篇 |
| 2010年 | 1028篇 |
| 2009年 | 1357篇 |
| 2008年 | 1205篇 |
| 2007年 | 1251篇 |
| 2006年 | 1206篇 |
| 2005年 | 895篇 |
| 2004年 | 911篇 |
| 2003年 | 808篇 |
| 2002年 | 770篇 |
| 2001年 | 664篇 |
| 2000年 | 674篇 |
| 1999年 | 595篇 |
| 1998年 | 588篇 |
| 1997年 | 536篇 |
| 1996年 | 406篇 |
| 1995年 | 412篇 |
| 1994年 | 421篇 |
| 1993年 | 315篇 |
| 1992年 | 321篇 |
| 1991年 | 264篇 |
| 1990年 | 312篇 |
| 1989年 | 280篇 |
| 1988年 | 255篇 |
| 1987年 | 289篇 |
| 1986年 | 243篇 |
| 1985年 | 321篇 |
| 1984年 | 345篇 |
| 1983年 | 335篇 |
| 1982年 | 318篇 |
| 1981年 | 255篇 |
| 1980年 | 272篇 |
| 1979年 | 217篇 |
| 1978年 | 209篇 |
| 1977年 | 220篇 |
| 1976年 | 180篇 |
| 1975年 | 195篇 |
| 1974年 | 181篇 |
| 1973年 | 170篇 |
| 1972年 | 117篇 |
排序方式： 共有10000条查询结果，搜索用时 218 毫秒
1.
2.
3.
The magnetic-field distribution outside a flat, infinitely conductive unbounded disk in the field of a point magnetic dipole is determined. A relationship is established between the problem of magnetic-field determination and the problem of the flow of an ideal incompressible fluid around an infinitely thin disk. 相似文献
4.
5.
6.
T.-C. Jim Yeh 《水文研究》1992,6(4):369-395
This paper presents an introductory overview of recently developed stochastic theories for tackling spatial variability problems in predicting groundwater flow and solute transport. Advantages and limitations of the theories are discussed. Lastly, strategies based on the stochastic approaches to predict solute transport in aquifers are recommended. 相似文献
7.
Mallory S. E. Roberts Crystal L. Brogan Bryan M. Gaensler Jason W. T. Hessels C.-Y. Ng Roger W. Romani 《Astrophysics and Space Science》2005,297(1-4):93-100
A remarkable number of pulsar wind nebulae (PWN) are coincident with EGRET γ-ray sources. X-ray and radio imaging studies of unidentified EGRET sources have resulted in the discovery of at least six new pulsar wind nebulae (PWN). Stationary PWN (SPWN) appear to be
associated with steady EGRET sources with hard spectra, typical for γ-ray pulsars. Their toroidal morphologies can help determine the geometry of the
pulsar which is useful for constraining models of pulsed γ-ray emission. Rapidly moving PWN (RPWN) with more cometary morphologies
seem to be associated with variable EGRET sources in regions where the ambient medium is dense compared to what is typical for the ISM. 相似文献
8.
9.
A spectacular change in the lower corona on the south-west limb has been found in solar images taken by the Yohkoh soft X-ray telescope. The event is characterized by a large topological change in magnetic field and a large intensity decrease observed after the X1. 1/1B flare on 9 November, 1991. A coronal mass ejection (CME) was observed by the Mark III K-coronameter (MK3) at the HAO/Mauna Loa Observatory. Both the MK3 (white-light) and soft X-ray observations showed that one leg of this CME was located above the flare site. An interplanetary shock associated with this event was observed by Pioneer Venus Orbiter, and, possibly, by IMP-8.Also Cooperative Institute for Research in the Environmental Sciences (CIRES), University of Colorado, Boulder, CO 80309, U.S.A. 相似文献
10.