全文获取类型
收费全文 | 2410篇 |
免费 | 683篇 |
国内免费 | 967篇 |
专业分类
测绘学 | 324篇 |
大气科学 | 415篇 |
地球物理 | 431篇 |
地质学 | 1741篇 |
海洋学 | 523篇 |
天文学 | 26篇 |
综合类 | 235篇 |
自然地理 | 365篇 |
出版年
2024年 | 25篇 |
2023年 | 72篇 |
2022年 | 175篇 |
2021年 | 215篇 |
2020年 | 158篇 |
2019年 | 196篇 |
2018年 | 139篇 |
2017年 | 165篇 |
2016年 | 141篇 |
2015年 | 182篇 |
2014年 | 153篇 |
2013年 | 213篇 |
2012年 | 246篇 |
2011年 | 233篇 |
2010年 | 239篇 |
2009年 | 214篇 |
2008年 | 177篇 |
2007年 | 214篇 |
2006年 | 172篇 |
2005年 | 154篇 |
2004年 | 148篇 |
2003年 | 79篇 |
2002年 | 78篇 |
2001年 | 68篇 |
2000年 | 55篇 |
1999年 | 44篇 |
1998年 | 18篇 |
1997年 | 13篇 |
1996年 | 13篇 |
1995年 | 20篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有4060条查询结果,搜索用时 31 毫秒
951.
Luo Zhaohua Xiao Xuchang Cao Yongqing Mo Xuanxue Su Shangguo Deng Jinfu Zhang Wenhui 《中国科学D辑(英文版)》2001,44(1):10-17
Geodynamic properties and evolution of the lithosphere on the north margin of the Tibetan Plateau are recently hot topics to geoscientists in the world. Have the northern plates been subducting underneath the Plateau? It is still an unsolved problem. One of the keys to solving this problem is to understand the genetic processes of Cenozoic magmas on the north margin of the Tibetan Plateau. However, there is no enough evidence supporting the subduction model. In contrast, a series of evidence indicates that collision-induced huge shearing faults and large-scale crust shortening played a main role in lithosphere motion on the north margin of the Tibetan Plateau. The mantle-derived igneous rocks strictly distribute at the intersections of large strike-slip faults on the north margin of the Plateau. Generation of magmas may be related to local extensional condition induced by strike-slipping faults, which lead to lithosphere gravitational instability and collapse, as well as upwelling of the deep hot material. Heat induced by shearing and carried by upwelling hot material may cause partial melting on H2O-bearing mantle. 相似文献
952.
遥感技术在鄂尔多斯盆地东南部煤层气勘探中的应用 总被引:1,自引:0,他引:1
从鄂尔多斯盆地黄土塬区煤层气勘探的实际需要出发,通过遥感解译,利用裂缝密度统计分析方法,对研究区煤层气高渗区带进行了预测,并对区内煤层气勘探的有利区带进行了初步评价,为煤层气勘探提供了重要的参考资料. 相似文献
953.
954.
Based on the data of first motion of 11 earthquake sequences with ML ≥ 3.0 recorded by the Telemetric Seismic Network of Shanxi since the 1980s, the first motion characteristics of each earthquake sequence were studied. It is known that earthquake sequences of different types have different consistency characteristics of focal mechanism. The decrease and increase of the first motion contradictory sign ratios could be taken as an index to judge whether there would still be a larger earthquake to come after the earthquake sequence. 相似文献
955.
This paper investigates the nonlinear prediction of monthly rainfall time series which consists of phase space con-tinuation of one-dimensional sequence, followed by least-square determination of the coefficients for the terms of the time-lag differential equation model and then fitting of the prognostic expression is made to 1951-1980 monthly rainfall datasets from Changsha station Results show that the model is likely to describe the nonlinearity of the an-nual cycle of precipitation on a monthly basis and to provide a basis for flood prevention and drought combating for the wet season. 相似文献
956.
提出用自然正交函数分解的方法来开拓相空间,从而研究有限区域上大气系统的混沌性质。与利用时间滞后作漂移来开拓相空间方法相比较,前者充分保证了相空间各基矢量的正交性,弥补了后者只能对单点资料进行计算的不足。文中利用欧洲中期数值天气预报中心1980-1986年北半球亚洲地区的500hPa位势高度场逐日格点资料进行了EOF分解并计算得到了该地区大气系统的分维数为D=6.2,从而表明,为支撑该地区大气系统的混沌吸引子至少应取7维系统或以7个变量才能作出描述。 相似文献
957.
958.
从Saltzman海气随机气候模式出发,得到了海温脉动θ'的Langevin方程以及对应的Fokker-plank方程。在给定参数条件下求数值解,得到的概率密度曲线p(x,t)具有多个极大值,并在p(x,t)-p(x,t+τ)相空间中呈现Cantor集合图象,表明该随机系统在上述参数条件下出现了混沌行为。 相似文献
959.
960.
QI Pu ZHAO Yean Engineer Institute of Hydraulic Research Yellow River Conservancy Commission Engineer Institute of Hydraulic Research Yellow River Conservancy Commission 《国际泥沙研究》1993,(1)
1. INTRODUCTIONThe Yellow River is a heavily sediment--laden river. Floods at Hyperconcentrationso f sediment (hereinafter simply referred to as hyperconcentrated flood) frequently occurring in the main river and its tributaries possess different characteristics of sedimenttransport. Sometimes they cause severe deposition whereas at other times they are capable of carrying substantial amount of sediment over long distances. The study on the lawof sediment transport is of significance to … 相似文献