全文获取类型
收费全文 | 4767篇 |
免费 | 1245篇 |
国内免费 | 1905篇 |
专业分类
测绘学 | 83篇 |
大气科学 | 307篇 |
地球物理 | 949篇 |
地质学 | 4363篇 |
海洋学 | 1033篇 |
天文学 | 741篇 |
综合类 | 221篇 |
自然地理 | 220篇 |
出版年
2024年 | 30篇 |
2023年 | 94篇 |
2022年 | 161篇 |
2021年 | 148篇 |
2020年 | 206篇 |
2019年 | 228篇 |
2018年 | 218篇 |
2017年 | 201篇 |
2016年 | 242篇 |
2015年 | 272篇 |
2014年 | 334篇 |
2013年 | 353篇 |
2012年 | 332篇 |
2011年 | 361篇 |
2010年 | 307篇 |
2009年 | 411篇 |
2008年 | 356篇 |
2007年 | 406篇 |
2006年 | 444篇 |
2005年 | 346篇 |
2004年 | 333篇 |
2003年 | 329篇 |
2002年 | 239篇 |
2001年 | 242篇 |
2000年 | 236篇 |
1999年 | 186篇 |
1998年 | 177篇 |
1997年 | 132篇 |
1996年 | 115篇 |
1995年 | 100篇 |
1994年 | 101篇 |
1993年 | 61篇 |
1992年 | 45篇 |
1991年 | 38篇 |
1990年 | 37篇 |
1989年 | 20篇 |
1988年 | 21篇 |
1987年 | 12篇 |
1986年 | 11篇 |
1985年 | 7篇 |
1984年 | 12篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1954年 | 2篇 |
排序方式: 共有7917条查询结果,搜索用时 10 毫秒
1.
2.
3.
A constitutive relation is derived for describing the mechanical response of chalk. The approach is based on a phenomenological framework which employs chemo‐plasticity. The properties of the material are assumed to be affected by the physico‐chemical processes that occur through the interaction between the skeleton and the pore fluid. The underlying mechanism is discussed by invoking a micromechanical analysis. The performance of the framework is illustrated by examining the evolution of mechanical characteristics in the presence of different pore fluids. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
4.
We report three new or updated techniques for probing the parameters of active galaxies based on the masses of their central
black holes MBH). First, we derived a near-IR analog of the bulge luminosity versus MBH relationship. The low scatter makes it a promising new tool to study the black hole demographics. Next, we present relations
between MBH and the10 μm and 2-10 keV nuclear luminosity. They may help to study the MBH evolution over wide redshift ranges. Finally, we measured MBH in quasars from z ∼ 3.4 to z ∼ 0.3 to search directly for MBH growth. Surprisingly, we found no evidence for growth implying that the majority of quasar host galaxies have undergone their
last major merger at z ≥ 3.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
The lensing properties of the Plummer model with a central point mass and external shear are derived, including the image multiplicities, critical curves and caustics. This provides a simple model for a flattened galaxy with a central supermassive black hole. For the Plummer model with black hole, the maximum number of images is four, provided the black hole mass is less than an upper bound which is calculated analytically. This introduces a method to constrain black hole masses by counting images, thus applicable at cosmological distance. With shear, the maximum number of images is six and we illustrate the occurrence of an astroid caustic and two metamorphoses. 相似文献
6.
7.
8.
WANG Yachun 《东北亚地学研究》2002,(1)
The paper deals with the methods of formation pressure evaluation for a single well by using the very common ac-cepted parameters, such as drilling exponent , and flowline temperature , etc. which is part of compiling the end well report. 相似文献
9.
10.