全文获取类型
| 收费全文 | 86276篇 |
| 免费 | 1771篇 |
| 国内免费 | 836篇 |
专业分类
| 测绘学 | 2283篇 |
| 大气科学 | 6768篇 |
| 地球物理 | 17845篇 |
| 地质学 | 28889篇 |
| 海洋学 | 7898篇 |
| 天文学 | 19274篇 |
| 综合类 | 220篇 |
| 自然地理 | 5706篇 |
出版年
| 2021年 | 538篇 |
| 2020年 | 700篇 |
| 2019年 | 797篇 |
| 2018年 | 1543篇 |
| 2017年 | 1501篇 |
| 2016年 | 2057篇 |
| 2015年 | 1373篇 |
| 2014年 | 2111篇 |
| 2013年 | 4383篇 |
| 2012年 | 2200篇 |
| 2011年 | 3193篇 |
| 2010年 | 2791篇 |
| 2009年 | 3930篇 |
| 2008年 | 3550篇 |
| 2007年 | 3341篇 |
| 2006年 | 3334篇 |
| 2005年 | 2776篇 |
| 2004年 | 2833篇 |
| 2003年 | 2640篇 |
| 2002年 | 2522篇 |
| 2001年 | 2211篇 |
| 2000年 | 2206篇 |
| 1999年 | 1926篇 |
| 1998年 | 1900篇 |
| 1997年 | 1813篇 |
| 1996年 | 1547篇 |
| 1995年 | 1485篇 |
| 1994年 | 1373篇 |
| 1993年 | 1211篇 |
| 1992年 | 1163篇 |
| 1991年 | 991篇 |
| 1990年 | 1234篇 |
| 1989年 | 1050篇 |
| 1988年 | 941篇 |
| 1987年 | 1135篇 |
| 1986年 | 994篇 |
| 1985年 | 1239篇 |
| 1984年 | 1434篇 |
| 1983年 | 1372篇 |
| 1982年 | 1258篇 |
| 1981年 | 1170篇 |
| 1980年 | 1033篇 |
| 1979年 | 972篇 |
| 1978年 | 1011篇 |
| 1977年 | 952篇 |
| 1976年 | 888篇 |
| 1975年 | 846篇 |
| 1974年 | 839篇 |
| 1973年 | 838篇 |
| 1972年 | 532篇 |
排序方式： 共有10000条查询结果，搜索用时 31 毫秒
11.
Abstract— The possibility of volcanism on Mercury has been a topic of discussion since Mariner 10 returned images of half the planet's surface showing widespread plains material. These plains could be volcanic or lobate crater ejecta. An assessment of the mechanics of the ascent and eruption of magma shows that it is possible to have widespread volcanism, no volcanism on the surface whatsoever, or some range in between. It is difficult to distinguish between a lava flow and lobate crater ejecta based on morphology and morphometry. No definite volcanic features have been identified on Mercury. However, known lunar volcanic features cannot be identified in images with similar resolutions and viewing geometries as the Mariner 10 dataset. Examination of high‐resolution, low Sun angle Mariner 10 images reveals several features which are interpreted to be flow fronts; it is unclear if these are volcanic flows or ejecta flows. This analysis implies that a clear assessment of volcanism on Mercury must wait for better data. MESSENGER (MErcury: Surface, Space ENvironment, GEochemistry, Ranging) will take images with viewing geometries and resolutions appropriate for the identification of such features. 相似文献
12.
13.
14.
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
15.
16.
The Cassini spacecraft, en route to Saturn, passed close to Jupiter while the Galileo spacecraft was completing its 28th and 29th orbits of Jupiter, thus offering a unique opportunity for direct study of the solar wind-Jovian interaction. Here evidence is given of response of the Jovian magnetopause and bow shock positions to changes of the north-south component of the solar wind magnetic field, a phenomenon long known to occur in equivalent circumstances at Earth. The period analyzed starts with the passage over Cassini of an interplanetary shock far upstream of Jupiter. The shock's arrival at Galileo on the dusk-flank of the magnetosphere caused Galileo to exit into the solar wind. Using inter-spacecraft timing based on the time delay established from the shock arrival at each spacecraft, we point out that Galileo's position with respect to the Jovian bow shock appears to correlate with changes in the disturbed north-south reversing field seen behind the shock. We specifically rule out the alternative of changes in the shape of the bow shock with rotations of the interplanetary magnetic field as the cause. 相似文献
17.
18.
19.
20.