全文获取类型
收费全文 | 1358篇 |
免费 | 280篇 |
国内免费 | 227篇 |
专业分类
测绘学 | 35篇 |
大气科学 | 73篇 |
地球物理 | 501篇 |
地质学 | 504篇 |
海洋学 | 73篇 |
天文学 | 571篇 |
综合类 | 42篇 |
自然地理 | 66篇 |
出版年
2024年 | 4篇 |
2023年 | 9篇 |
2022年 | 23篇 |
2021年 | 22篇 |
2020年 | 30篇 |
2019年 | 36篇 |
2018年 | 34篇 |
2017年 | 51篇 |
2016年 | 33篇 |
2015年 | 37篇 |
2014年 | 47篇 |
2013年 | 54篇 |
2012年 | 62篇 |
2011年 | 47篇 |
2010年 | 64篇 |
2009年 | 113篇 |
2008年 | 107篇 |
2007年 | 119篇 |
2006年 | 122篇 |
2005年 | 95篇 |
2004年 | 117篇 |
2003年 | 87篇 |
2002年 | 88篇 |
2001年 | 75篇 |
2000年 | 75篇 |
1999年 | 61篇 |
1998年 | 53篇 |
1997年 | 29篇 |
1996年 | 37篇 |
1995年 | 29篇 |
1994年 | 26篇 |
1993年 | 13篇 |
1992年 | 18篇 |
1991年 | 15篇 |
1990年 | 12篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1983年 | 1篇 |
排序方式: 共有1865条查询结果,搜索用时 125 毫秒
91.
安徽地区地震波衰减、场地响应及震源新参数的测定 总被引:5,自引:2,他引:5
根据安徽数字地震台网7个地震台的143条波形资料,研究了安徽地区的衰减模型和各台站的场地响应。采用三段几何衰减模型拟合,得到了安徽及邻近地区的几何衰减函数,得到安徽地区非弹性衰减Q值随频率f的关系为Q(f)=235.3×f0.616;7个台站的场地响应均无明显的放大效应,这与它们均处于岩石地基相符;并在本地区地震预测研究中尝试使用新参数,进行了初步的应用。 相似文献
92.
A model is suggested to simulate the physical aspect of diagenesis in porous rocks. A bidisperse ballistic deposition model with relaxation of deposited grains is used to generate the porous structure. Sedimentation and erosion are allowed to restructure the pore space as a fluid flows through the rock. The effect of this restructuring of the pore space on permeability is studied. The Navier–Stokes equation is solved numerically by the finite difference method to determine the pressure and velocity distributions in the pore space. We find that though deposition is the dominant process in our model of diagenesis, reducing the porosity, the permeability may increase dramatically in some cases. These are when the erosion takes place at a single narrow constriction in the pore channel. 相似文献
93.
We investigate the estimation of interfacial areas, curvatures, and common curve lengths in multiphase porous medium systems. Algorithms are developed to obtain estimates of these quantities based upon a variety of potential data sources and estimation approaches. The accuracy of the derived approximations are evaluated as a function of the data type and resolution of the data. The methods advanced improve upon standard approaches now in use and show excellent accuracy at resolutions on the order of five lattice points per minimum radius of curvature of the object being resolved. Finally, we suggest a promising class of extensions that could lead to further improvements in the accuracy of such methods. 相似文献
94.
This work proposes a complete method for automatic inversion of data from hydraulic interference pumping tests based on both homogeneous and fractal dual-medium approaches. The aim is to seek a new alternative concept able to interpret field data, identify macroscopic hydraulic parameters and therefore enhance the understanding of flow in porous fractured reservoirs. Because of its much contrasted sensitivities to parameters, the dual-medium approach yields an ill-posed inverse problem that requires a specific optimization procedure including the calculation of analytical sensitivities and their possible re-scaling. Once these constraints are fulfilled, the inversion proves accurate, provides unambiguous and reliable results. In the fractal context inverting several drawdown curves from different locations at the same time reveals more accurate. Finally, hydraulic parameters drawn from inversion should be taken into account to improve in various situations the conditioning of up-scaled flow in fractured rocks. 相似文献
95.
96.
97.
98.
Sun Jinzhong College of Engineering Technology China University of Geosciences Beijing Tan Hanhua Guizhou Institute of Communication Design Guiyang Qi Shengwen Institute of Geology Chinese Academy of Sciences Beijing 《中国地质大学学报(英文版)》2001,12(2)
INTRODUCTIONBecauseofitssimpleoperationandlowcostaswellaseffec tivenessformanyprojects ,heavytampinghasbeenusedwidelyintheworld (Qianetal.,1986 ) .However,thestrongvibrationinsoilmasscausedbyheavytampingmaybeharmfultobuildings,instrumentsandevenhumanbodiesar… 相似文献
99.
100.