全文获取类型
| 收费全文 | 85256篇 |
| 免费 | 1375篇 |
| 国内免费 | 522篇 |
专业分类
| 测绘学 | 1755篇 |
| 大气科学 | 5610篇 |
| 地球物理 | 16241篇 |
| 地质学 | 30777篇 |
| 海洋学 | 7871篇 |
| 天文学 | 19923篇 |
| 综合类 | 218篇 |
| 自然地理 | 4758篇 |
出版年
| 2022年 | 619篇 |
| 2021年 | 1035篇 |
| 2020年 | 1114篇 |
| 2019年 | 1247篇 |
| 2018年 | 2551篇 |
| 2017年 | 2361篇 |
| 2016年 | 2719篇 |
| 2015年 | 1355篇 |
| 2014年 | 2616篇 |
| 2013年 | 4490篇 |
| 2012年 | 2864篇 |
| 2011年 | 3694篇 |
| 2010年 | 3373篇 |
| 2009年 | 4263篇 |
| 2008年 | 3717篇 |
| 2007年 | 3834篇 |
| 2006年 | 3551篇 |
| 2005年 | 2527篇 |
| 2004年 | 2456篇 |
| 2003年 | 2284篇 |
| 2002年 | 2275篇 |
| 2001年 | 1975篇 |
| 2000年 | 1960篇 |
| 1999年 | 1538篇 |
| 1998年 | 1601篇 |
| 1997年 | 1465篇 |
| 1996年 | 1240篇 |
| 1995年 | 1242篇 |
| 1994年 | 1045篇 |
| 1993年 | 1007篇 |
| 1992年 | 931篇 |
| 1991年 | 969篇 |
| 1990年 | 934篇 |
| 1989年 | 817篇 |
| 1988年 | 752篇 |
| 1987年 | 884篇 |
| 1986年 | 773篇 |
| 1985年 | 944篇 |
| 1984年 | 1071篇 |
| 1983年 | 1031篇 |
| 1982年 | 951篇 |
| 1981年 | 891篇 |
| 1980年 | 792篇 |
| 1979年 | 748篇 |
| 1978年 | 726篇 |
| 1977年 | 620篇 |
| 1976年 | 627篇 |
| 1975年 | 614篇 |
| 1974年 | 590篇 |
| 1973年 | 658篇 |
排序方式： 共有10000条查询结果，搜索用时 15 毫秒
51.
52.
Transverse secondary circulations involving surface convergence, observed in a well-mixed estuary in North Wales, are made visible by the collection of surface material along an axial line which extends continuously for many kilometres through the estuary. The circulation and axial convergence, however, are seen only during the flood phase of the tide and no similar behaviour has been observed during the ebb phase.Convergent circulations in the estuary are associated with small but steady transverse density gradients in the cross-section, produced by non-uniform advection of the longitudinal gradient through the channel. A diagnostic model, using measured mean distributions of cross-sectional density, indicates surface transverse velocities (～0.1 ms?1) similar to those observed in the estuary. The model further predicts appreciable transverse divergent currents at a fractional depth of 0.75: a prediction which has been tested in the estuary using a vertical array of accurately resolving current direction indicators. 相似文献
53.
M.S. Hanner E. Tedesco A.T. Tokunaga G.J. Veeder D.F. Lester F.C. Witteborn J.D. Bregman J. Gradie L. Lebofsky 《Icarus》1985,64(1):11-19
The dust coma of Comet P/Churyumov-Gerasimenko was monitored in the infrared (1–20 μm) from September 1982 to March 1983. Maximum dust production rate of ～2 × 105 g/sec occured in December, 1 month postperihelion. The ratio of dust/gas production was higher than that in other short-period comets. No silicate feature was visible in the 8- to 13-μm spectrum on 23 October. The mean geometric albedo of the grains was ～0.04 at 1.25 μm and ～0.05 at 2.2 μm. 相似文献
54.
Summary. A method of synthetic seismogram computation for teleseismic SV -waves is developed in order to treat quantitatively SV -waves in problems of body wave source inversion and source—receiver structure studies. The method employs WKBJ theory for a generalized ray in a vertically inhomogeneous half-space and the propagator matrix technique for waves in near-surface homogeneous layers. Wavenumber integration is done along the real axis of the wavenumber plane and anelasticity is included by using complex velocity in all regions of the earth model. The near-surface source structure is taken into account in the computation for the case of the shallow source by allowing a point source to be located in the homogeneous layers. Source and receiver area structures are also allowed to differ. A general moment tensor point source is considered. 相似文献
55.
56.
Carlos J.A.P. Martins 《Astrophysics and Space Science》2003,283(4):439-444
I briefly present the Organizing Committee's and my own motivation for organizing this workshop, and I suggest a few key questions
for which we will try to find possible answers in the coming days.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
57.
58.
59.
60.