全文获取类型
收费全文 | 9144篇 |
免费 | 1927篇 |
国内免费 | 2461篇 |
专业分类
测绘学 | 763篇 |
大气科学 | 1970篇 |
地球物理 | 2269篇 |
地质学 | 5082篇 |
海洋学 | 1216篇 |
天文学 | 248篇 |
综合类 | 836篇 |
自然地理 | 1148篇 |
出版年
2024年 | 24篇 |
2023年 | 131篇 |
2022年 | 398篇 |
2021年 | 457篇 |
2020年 | 357篇 |
2019年 | 454篇 |
2018年 | 537篇 |
2017年 | 487篇 |
2016年 | 500篇 |
2015年 | 489篇 |
2014年 | 543篇 |
2013年 | 570篇 |
2012年 | 661篇 |
2011年 | 682篇 |
2010年 | 706篇 |
2009年 | 642篇 |
2008年 | 557篇 |
2007年 | 564篇 |
2006年 | 526篇 |
2005年 | 442篇 |
2004年 | 367篇 |
2003年 | 304篇 |
2002年 | 295篇 |
2001年 | 282篇 |
2000年 | 318篇 |
1999年 | 346篇 |
1998年 | 232篇 |
1997年 | 276篇 |
1996年 | 230篇 |
1995年 | 204篇 |
1994年 | 178篇 |
1993年 | 204篇 |
1992年 | 128篇 |
1991年 | 101篇 |
1990年 | 75篇 |
1989年 | 64篇 |
1988年 | 49篇 |
1987年 | 40篇 |
1986年 | 26篇 |
1985年 | 18篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 13篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1963年 | 1篇 |
1958年 | 15篇 |
1954年 | 5篇 |
1947年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
地壳对海洋潮汐的响应 总被引:2,自引:2,他引:0
应用三维动态有限元方法研究了中国北部地区的地壳对邻近的渤海与黄海海平面变化的响应。虽然此应力场过于微弱不足以引发地震,但发现应力集中的位置及应力场变化较大的位置恰好与某些现代地震的震中一致。这一结果表明研究地壳对广泛分布的载荷的响应对研究区域地震构造是有帮助的。 相似文献
12.
The auriferous veins at Jinniushan occurs within the Jinniushan faulted zone in the Kunyushan Granite. Optical observation reveals that gold ore body formed during the main stage of hydrothermal activity. Detailed geothermometric studies of fluid inclusions from the veins show that the forming temperature ranges between 130℃ and 370℃ and the salinity is from 4.01 to 15.21 wvt percent NaCl. The ore-forming fluid is featured by low to moderate salinity, and low to moderate temperature. According to investigations of the values of vapor/liquid and temperatures of the ore-forming fluids, we propose that the boiling fluid inclusions exist in the main mineralization stages. Fluid boiling is suggested as a mechanism for the precipitation of gold from the hydrothermal fluid in the Jinniushan gold deposit. 相似文献
13.
Zhan-Le Du Hua-Ning Wang Xiang-Tao He National Astronomical Observatories Chinese Academy of Sciences Beijing Department of Astronomy Beijing Normal University Beijing 《中国天文和天体物理学报》2006,6(4):489-494
The maximum amplitudes of solar activity cycles are found to be well anti-correlated (r = -0.72) with the newly defined solar cycle lengths three cycles before (at lag -3) in 13-month running mean sunspot numbers during the past 190 years. This result could be used for predicting the maximum sunspot numbers. The amplitudes of Cycles 24 and 25 are estimated to be 149.5±27.6 and 144.3±27.6, respectively. 相似文献
14.
15.
This paper proposes a multi‐level parallelized substructuring–frontal combined algorithm for the analysis of the problem of thermo/hydraulic/mechanical behaviour of unsaturated soil. Temperature, displacement, pore water pressure and pore air pressure are treated as the primary variables in a non‐linear analysis. Details are given firstly of the substructuring–frontal combined approach. The incorporation of the algorithm in a multi‐level parallel strategy is then discussed. The parallel processing can thus be carried out at different substructural levels. The method thus developed impacts, in a positive way, on both computer storage requirement and execution time. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
16.
Pco2 of air and seawater samples from the East China Sea(ECS) were measured in situ in autumn, 1994,Ocean currents,terrestrial fluviation,biological activities,etc.,Pco2 char-acters in air and seawater were investigated,CO2 flux and its character in the East China Sea are discussed on the basis of the Pco2 profiles of air and seawater,It was clear that the nearshore was the source of CO2;and tht the oulter sea area was the sink of CO2; and that the shelf area of the EXS is a net sink for atmospheric CO2 in autumn. 相似文献
17.
本文给出1993—1994年期间,用云南天文台1米望远镜折轴摄谱仪观测获得类太阳色球活动星。εEri的5个波段高分辨、高信噪比光谱,运用两种不同方法:谱线轮廓塞曼致宽分析和多重线统计分析法成功地测定了εEri的表面磁场强度和磁场的覆盖因子,并对这两种磁场测定方法作了简单的讨论. 相似文献
18.
We have studied the optical historical light curves of two Active Galactic Nuclei (AGNs): OJ287 and 3C345. We find a linear
dependence between the magnitude and the logarithm of the length of the time the objects stay below this magnitude. The relation
may originate from a fractal structure of the light curve.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
Boli basin, between Yishu fracture belt and Dunmi fracture belt, is the biggest Mesozoic coal basin in the east of Heilongjiang Province. Now it is a fault - fold remnant basin. The basin' s shape is generally consistent with the whole distribution of the cover folds, an arc protruding southwards. The basement of the basin can be divided into three fault blocks or structural units. The formation and evoluation of the basin in Mesozoic was determined by the basement fault blocks' displacement features rusulted from by the movement of the edge faults and the main basement faults. 相似文献
20.