全文获取类型
收费全文 | 6736篇 |
免费 | 269篇 |
国内免费 | 35篇 |
专业分类
化学 | 4764篇 |
晶体学 | 121篇 |
力学 | 113篇 |
综合类 | 1篇 |
数学 | 802篇 |
物理学 | 1239篇 |
出版年
2023年 | 53篇 |
2022年 | 50篇 |
2021年 | 92篇 |
2020年 | 161篇 |
2019年 | 154篇 |
2018年 | 88篇 |
2017年 | 88篇 |
2016年 | 192篇 |
2015年 | 197篇 |
2014年 | 198篇 |
2013年 | 275篇 |
2012年 | 377篇 |
2011年 | 443篇 |
2010年 | 247篇 |
2009年 | 254篇 |
2008年 | 390篇 |
2007年 | 402篇 |
2006年 | 385篇 |
2005年 | 356篇 |
2004年 | 301篇 |
2003年 | 213篇 |
2002年 | 231篇 |
2001年 | 115篇 |
2000年 | 107篇 |
1999年 | 72篇 |
1998年 | 94篇 |
1997年 | 82篇 |
1996年 | 102篇 |
1995年 | 95篇 |
1994年 | 57篇 |
1993年 | 66篇 |
1992年 | 63篇 |
1991年 | 57篇 |
1990年 | 67篇 |
1989年 | 46篇 |
1988年 | 47篇 |
1987年 | 49篇 |
1986年 | 43篇 |
1985年 | 58篇 |
1984年 | 45篇 |
1983年 | 41篇 |
1982年 | 35篇 |
1981年 | 52篇 |
1980年 | 50篇 |
1979年 | 26篇 |
1978年 | 34篇 |
1977年 | 39篇 |
1976年 | 32篇 |
1973年 | 42篇 |
1971年 | 27篇 |
排序方式: 共有7040条查询结果,搜索用时 15 毫秒
1.
Laurens Kooijman Dr. Matthias Schuster Christian Baumann Simon Jurt Dr. Frank Löhr Dr. Boris Fürtig Prof. Dr. Peter Güntert Prof. Dr. Oliver Zerbe 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(47):21151-21158
To achieve efficient proton pumping in the light-driven proton pump bacteriorhodopsin (bR), the protein must be tightly coupled to the retinal to rapidly convert retinal isomerization into protein structural rearrangements. Methyl group dynamics of bR embedded in lipid nanodiscs were determined in the dark-adapted state, and were found to be mostly well ordered at the cytosolic side. Methyl groups in the M145A mutant of bR, which displays only 10 % residual proton pumping activity, are less well ordered, suggesting a link between side-chain dynamics on the cytosolic side of the bR cavity and proton pumping activity. In addition, slow conformational exchange, attributed to low frequency motions of aromatic rings, was indirectly observed for residues on the extracellular side of the bR cavity. This may be related to reorganization of the water network. These observations provide a detailed picture of previously undescribed equilibrium dynamics on different time scales for ground-state bR. 相似文献
2.
3.
4.
5.
6.
7.
Steven D. Bull Simon W. Epstein Nadeam Mujtaba Edward D. Savory Juan A. Tamayo 《Tetrahedron》2006,62(33):7911-7925
Enolates of (S)-N,N′-bis-(p-methoxybenzyl)-3-iso-propylpiperazine-2,5-dione exhibit high levels of enantiodiscrimination in alkylations with (RS)-1-aryl-1-bromoethanes and (RS)-2-bromoesters, affording substituted diketopiperazines containing two new stereogenic centres in high de. Deprotection and hydrolysis of the resultant substituted diketopiperazines provides a route to the asymmetric synthesis of homochiral methyl 2-amino-3-aryl-butanoates and 3-methyl-aspartates in high de and ee. 相似文献
8.
9.
On the average complexity of 3D-Voronoi diagrams of random points on convex polytopes 总被引:1,自引:0,他引:1
It is well known that the complexity, i.e. the number of vertices, edges and faces, of the 3-dimensional Voronoi diagram of n points can be as bad as Θ(n2). It is also known that if the points are chosen Independently Identically Distributed uniformly from a 3-dimensional region such as a cube or sphere, then the expected complexity falls to O(n). In this paper we introduce the problem of analyzing what occurs if the points are chosen from a 2-dimensional region in 3-dimensional space. As an example, we examine the situation when the points are drawn from a Poisson distribution with rate n on the surface of a convex polytope. We prove that, in this case, the expected complexity of the resulting Voronoi diagram is O(n). 相似文献
10.