全文获取类型
收费全文 | 8864篇 |
免费 | 404篇 |
国内免费 | 310篇 |
专业分类
化学 | 2468篇 |
晶体学 | 11篇 |
力学 | 1882篇 |
综合类 | 47篇 |
数学 | 3380篇 |
物理学 | 1790篇 |
出版年
2024年 | 9篇 |
2023年 | 116篇 |
2022年 | 154篇 |
2021年 | 151篇 |
2020年 | 243篇 |
2019年 | 187篇 |
2018年 | 162篇 |
2017年 | 218篇 |
2016年 | 251篇 |
2015年 | 245篇 |
2014年 | 434篇 |
2013年 | 805篇 |
2012年 | 331篇 |
2011年 | 537篇 |
2010年 | 464篇 |
2009年 | 582篇 |
2008年 | 541篇 |
2007年 | 552篇 |
2006年 | 433篇 |
2005年 | 360篇 |
2004年 | 370篇 |
2003年 | 306篇 |
2002年 | 265篇 |
2001年 | 206篇 |
2000年 | 180篇 |
1999年 | 164篇 |
1998年 | 149篇 |
1997年 | 153篇 |
1996年 | 114篇 |
1995年 | 126篇 |
1994年 | 121篇 |
1993年 | 81篇 |
1992年 | 95篇 |
1991年 | 95篇 |
1990年 | 75篇 |
1989年 | 56篇 |
1988年 | 35篇 |
1987年 | 40篇 |
1986年 | 16篇 |
1985年 | 42篇 |
1984年 | 34篇 |
1983年 | 25篇 |
1982年 | 16篇 |
1981年 | 14篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1973年 | 2篇 |
排序方式: 共有9578条查询结果,搜索用时 46 毫秒
1.
2.
The behavior and mechanism of background signals during depth profiling of atmospheric elements using dual-beam time-of-flight secondary ion mass spectrometry (TOF-SIMS) have been experimentally investigated for silicon wafers. The background signals of atmospheric elements were found to be inversely proportional to the sputtering rate. Most of the background signals are largely attributable to the accumulation of components through adsorption and ion bombardment in the pre-equilibrium state. On the other hand, the contribution of real-time adsorption during the instant after the last sputtering in the equilibrium state is negligible under the present experimental conditions. H2O is dominant in the background formation process of hydrogen and oxygen, which is supported by the higher adsorption coefficients. The background levels of carbon and nitrogen are lower than those of hydrogen and oxygen. Furthermore, the background signal of carbon with respect to the sputtering rate shows a different trend than the other elements. This could be attributed to accumulation in the pre-equilibrium state. These results indicate that the background levels can be lowered close to those of dynamic-SIMS by using an extremely high sputtering rate in dual-beam TOF-SIMS. 相似文献
3.
Qinhai ZHANG 《Frontiers of Mathematics in China》2022,17(1):1
We survey some unsolvable conjectures in finite p-groups and their research progress. 相似文献
4.
5.
6.
Shilin Jiang Dr. Yalan Liu Dr. Lin Wang Prof. Zhifang Chai Prof. Wei-Qun Shi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(60):e202201145
The coordination chemistry of f-block elements (lanthanide and actinide) in molten salts has become a resounding topic in view of its great importance to the research and development (R&D) of molten salt reactors and pyroprocessing. In this Review article, a general overview of the coordination chemistry of f-block elements in molten salts is provided including past achievements and recent advances. Particular emphases are placed on the oxidation state, speciation, and solution structure of f-block metal ions in molten salts, as well as their relationships with the salt composition. Furthermore, this review briefly discusses the spectroscopic and theoretical methods that complement each other in revealing the coordination properties. 相似文献
8.
We provide a theoretical study of Algebraic Geometry codes constructed from abelian surfaces defined over finite fields. We give a general bound on their minimum distance and we investigate how this estimation can be sharpened under the assumption that the abelian surface does not contain low genus curves. This approach naturally leads us to consider Weil restrictions of elliptic curves and abelian surfaces which do not admit a principal polarization. 相似文献
9.
10.