全文获取类型
收费全文 | 99305篇 |
免费 | 1460篇 |
国内免费 | 1603篇 |
专业分类
测绘学 | 3132篇 |
大气科学 | 8052篇 |
地球物理 | 19584篇 |
地质学 | 39842篇 |
海洋学 | 7118篇 |
天文学 | 17168篇 |
综合类 | 2343篇 |
自然地理 | 5129篇 |
出版年
2021年 | 493篇 |
2020年 | 560篇 |
2019年 | 586篇 |
2018年 | 7379篇 |
2017年 | 6724篇 |
2016年 | 5020篇 |
2015年 | 1333篇 |
2014年 | 1772篇 |
2013年 | 3203篇 |
2012年 | 3384篇 |
2011年 | 6412篇 |
2010年 | 5669篇 |
2009年 | 6424篇 |
2008年 | 5327篇 |
2007年 | 6069篇 |
2006年 | 2342篇 |
2005年 | 2398篇 |
2004年 | 2388篇 |
2003年 | 2336篇 |
2002年 | 2029篇 |
2001年 | 1535篇 |
2000年 | 1550篇 |
1999年 | 1232篇 |
1998年 | 1210篇 |
1997年 | 1240篇 |
1996年 | 1080篇 |
1995年 | 1011篇 |
1994年 | 962篇 |
1993年 | 791篇 |
1992年 | 807篇 |
1991年 | 791篇 |
1990年 | 792篇 |
1989年 | 756篇 |
1988年 | 728篇 |
1987年 | 834篇 |
1986年 | 763篇 |
1985年 | 892篇 |
1984年 | 976篇 |
1983年 | 1010篇 |
1982年 | 922篇 |
1981年 | 880篇 |
1980年 | 871篇 |
1979年 | 774篇 |
1978年 | 760篇 |
1977年 | 708篇 |
1976年 | 638篇 |
1975年 | 630篇 |
1974年 | 689篇 |
1973年 | 661篇 |
1972年 | 413篇 |
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
71.
72.
A new procedure to separate the instrumental and atmospheric components of stray light is presented. It is based on the dependence of the aureole's atmospheric component on the air mass and is applied to measurements taken with the Vacuum Newton Telescope (VNT) at the Observatorio del Teide (Tenerife). The resulting instrumental part is independent of the air mass.The variation of both components with wavelength is also studied. The instrumental component shows no dependence on wavelength, in contrast to the atmospheric one which is greater in the blue than in the red.It is concluded that observations with air masses larger than two will probably be strongly affected by stray light. 相似文献
73.
74.
CHUDongsheng LIANGMeng SHIXin ZHANGLing 《中国海洋大学学报(英文版)》2004,3(1):106-110
1 Introduction Inrecentyearstherehasbeengrowingresearchin terestinthetwo dimensional (2 D )systemtheory .The 2 Dsystemsmayfindapplicationsinareassuchasmarineseismicdataprocessingandimageprocessing .Althoughmoreandmorevaluableresultshavebeengained ,mos… 相似文献
75.
76.
Two spectrophotometric scans of comet Levy (1990c) have been analysed to estimate Haser model column densities and production rates of CN andC
2 molecules. 相似文献
77.
78.
An updated Lagrangian finite-element formulation has been developed for time-dependent problems of soil consolidation involving finite deformations. Large plastic strains as well as rotations occur in such problems and nominal stress measures are introduced in the formulation to redefine stresses. This leads to corrective terms for equilibrium and yield violations in addition to geometric stiffening terms in the governing integral equations. The soil is considered to be either a linear elastic or an elastoplastic, critical-state material. Some simple numerical examples are studied to validate the formulation, followed by a detailed analysis of the problem of penetration of a pile into soil. The results of this problem are viewed with emphasis on the physical interpretation and practical significance. 相似文献
79.
80.
J.H. Krolik 《Astrophysics and Space Science》1997,248(1-2):207-215
A short survey is presented of dynamical (and thermodynamical) issues relevant to outflows in Seyfert galaxies like NGC 1068.
Numerical simulations incorporating both realistic radiative heating and cooling, and angular momentum, show that the fraction
of injected gas which escapes in a wind is very sensitive to both the injection pressure and the gas's angular momentum. Radiation
pressure acting through a variety of atomic opacity processes may also be important.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献