全文获取类型
收费全文 | 103988篇 |
免费 | 2029篇 |
国内免费 | 958篇 |
专业分类
测绘学 | 2585篇 |
大气科学 | 7383篇 |
地球物理 | 21253篇 |
地质学 | 37195篇 |
海洋学 | 8957篇 |
天文学 | 23375篇 |
综合类 | 346篇 |
自然地理 | 5881篇 |
出版年
2022年 | 584篇 |
2021年 | 1003篇 |
2020年 | 1099篇 |
2019年 | 1148篇 |
2018年 | 2677篇 |
2017年 | 2505篇 |
2016年 | 3134篇 |
2015年 | 1865篇 |
2014年 | 3095篇 |
2013年 | 5504篇 |
2012年 | 3289篇 |
2011年 | 4376篇 |
2010年 | 3835篇 |
2009年 | 5096篇 |
2008年 | 4541篇 |
2007年 | 4340篇 |
2006年 | 4075篇 |
2005年 | 3228篇 |
2004年 | 3150篇 |
2003年 | 2930篇 |
2002年 | 2734篇 |
2001年 | 2519篇 |
2000年 | 2376篇 |
1999年 | 1974篇 |
1998年 | 2082篇 |
1997年 | 1951篇 |
1996年 | 1479篇 |
1995年 | 1632篇 |
1994年 | 1403篇 |
1993年 | 1282篇 |
1992年 | 1217篇 |
1991年 | 1154篇 |
1990年 | 1281篇 |
1989年 | 1079篇 |
1988年 | 1000篇 |
1987年 | 1257篇 |
1986年 | 1028篇 |
1985年 | 1336篇 |
1984年 | 1451篇 |
1983年 | 1412篇 |
1982年 | 1282篇 |
1981年 | 1197篇 |
1980年 | 1063篇 |
1979年 | 991篇 |
1978年 | 1012篇 |
1977年 | 910篇 |
1976年 | 880篇 |
1975年 | 841篇 |
1974年 | 826篇 |
1973年 | 853篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
92.
93.
94.
Rostov State Pedagogical Institute; All-Union Scientific Research Institute Gradient. Translated from Astrofizika, Vol. 33, No. 3, pp. 379–393, November–December, 1990. 相似文献
95.
M. A. Mansour 《Astrophysics and Space Science》1990,166(2):269-275
The interaction of free convection with thermal radiation of the oscillatory flow past a vertical plate is studied. The Rosseland approximation is used to describe the radiative heat flux in the energy equation. 相似文献
96.
It is shown that the kinematical parameters associated with the congruence formed by tachyonic motion can be defined in the manner of Greenberg, but not that of Ehlers. The space-like counterpart of Raychaudhuri's equation has also been obtained. 相似文献
97.
Electron impact excitation rates for transitions in the S v ion, calculated with theR-matrix code, are used to derive the electron temperature sensitive emission line ratiosR
1 =I(854.8 Å)/I(786.9 Å),R
2 =I(852.2 Å)/I(786.9 Å),R
3 =I(849.2 Å)/I(786.9 Å), andR
4 =I(1199.1 Å)/I(786.9 Å), which are found to be significantly different from previous estimates. A comparison of the present results with observational data for a sunspot obtained with the Harvard S-055 spectrometer on boardSkylab reveals generally good agreement between theory and experiment, except in the case ofR
1, which is probably due to blending in the 854.8 Å feature. The possible effects of Lyman continuum absorption on the observed line ratios is briefly discussed. 相似文献
98.
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
99.
Transport by southeastern rivers has insignificant influence on the lead concentration of southeastern shelf waters. If the rate of mobilization and transport of lead by these rivers is representative of uncontaminated fluvial transport during the Pleistocene, only about 5% of the prehistoric output of lead to the North Atlantic can be accounted for by river input.Lead concentrations in southeastern shelf waters are similar to those of North Atlantic Water from the upper 1000 m, which is probably similar to the intrusion source water for the shelf. Atmospheric inputs to the shelf of the same magnitude as observed for the Western North Atlantic are difficult to reconcile given the residence time of shelf waters and their lead concentration unless the rate of loss of lead to shelf sediments is about the same as the atmospheric flux. 相似文献
100.
A coupled continuum‐discrete hydromechanical model was employed to analyse the liquefaction of a saturated loose deposit of cohesionless particles when subjected to a dynamic base excitation. The pore fluid flow was idealized using averaged Navier–Stokes equations and the discrete element method was employed to model the solid phase particles. A well established semi‐empirical relationship was utilized to quantify the fluid–particle interactions. The conducted simulations revealed a number of salient micro‐mechanical mechanisms and response patterns associated with the deposit liquefaction. Space and time variation of porosity was a major factor which affected the coupled response of the solid and fluid phases. Pore fluid flow was within Darcy's regime. The predicted response exhibited macroscopic patterns consistent with experimental results and case histories of the liquefaction of granular soil deposits. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献