全文获取类型
收费全文 | 4114篇 |
免费 | 119篇 |
国内免费 | 49篇 |
专业分类
化学 | 2105篇 |
晶体学 | 14篇 |
力学 | 97篇 |
数学 | 1059篇 |
物理学 | 1007篇 |
出版年
2022年 | 30篇 |
2021年 | 64篇 |
2020年 | 43篇 |
2019年 | 63篇 |
2018年 | 91篇 |
2017年 | 56篇 |
2016年 | 118篇 |
2015年 | 112篇 |
2014年 | 125篇 |
2013年 | 225篇 |
2012年 | 209篇 |
2011年 | 259篇 |
2010年 | 154篇 |
2009年 | 158篇 |
2008年 | 209篇 |
2007年 | 193篇 |
2006年 | 191篇 |
2005年 | 176篇 |
2004年 | 189篇 |
2003年 | 132篇 |
2002年 | 130篇 |
2001年 | 71篇 |
2000年 | 56篇 |
1999年 | 47篇 |
1998年 | 59篇 |
1997年 | 51篇 |
1996年 | 69篇 |
1995年 | 54篇 |
1994年 | 51篇 |
1993年 | 57篇 |
1992年 | 52篇 |
1991年 | 43篇 |
1990年 | 42篇 |
1989年 | 33篇 |
1988年 | 29篇 |
1987年 | 23篇 |
1986年 | 31篇 |
1985年 | 44篇 |
1984年 | 34篇 |
1982年 | 40篇 |
1981年 | 36篇 |
1979年 | 36篇 |
1978年 | 29篇 |
1977年 | 28篇 |
1976年 | 34篇 |
1975年 | 29篇 |
1974年 | 22篇 |
1973年 | 23篇 |
1971年 | 22篇 |
1970年 | 22篇 |
排序方式: 共有4282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.
In two dimensional electron systems with Coulomb or dipolar interactions, a direct transition, whether first or second order, from a liquid to a crystalline state is forbidden. As a result, between these phases there must be other (micro-emulsion) phases which can be viewed as a meso-scale mixture of the liquid and crystalline phases. We investigate the transport properties of these new electronic phases and present arguments that they are responsible for the various transport anomalies that have been seen in experiments on the strongly correlated 2DEG in high mobility semiconductor devices with low electron densities. 相似文献
3.
We predict ultraslow collapse of “tubular image states” (TIS) on material surfaces. TIS are bound Rydberg-like electronic states formed at large distances (∼30 nm) from the surfaces of suspended circularly-symmetric nanowires, such as metallic C nanotubes. The states are formed in potential wells, resulting from a combination of the TIS-electron attraction to image charges in the nanotube and its centrifugal repulsion, caused by spinning around the tube. We demonstrate that TIS can collapse on the tube surface by passing their angular momentum l to circularly polarized flexural phonons excited in the tube. Our analysis shows that for highly detached TIS with l ? 6 the relaxation lifetimes are of the order of 10 ns-1 μs, while for l < 6 these lifetimes are reduced by several orders of magnitude. 相似文献
4.
The Sample Average Approximation Method Applied to Stochastic Routing Problems: A Computational Study 总被引:1,自引:0,他引:1
Bram Verweij Shabbir Ahmed Anton J. Kleywegt George Nemhauser Alexander Shapiro 《Computational Optimization and Applications》2003,24(2-3):289-333
The sample average approximation (SAA) method is an approach for solving stochastic optimization problems by using Monte Carlo simulation. In this technique the expected objective function of the stochastic problem is approximated by a sample average estimate derived from a random sample. The resulting sample average approximating problem is then solved by deterministic optimization techniques. The process is repeated with different samples to obtain candidate solutions along with statistical estimates of their optimality gaps.We present a detailed computational study of the application of the SAA method to solve three classes of stochastic routing problems. These stochastic problems involve an extremely large number of scenarios and first-stage integer variables. For each of the three problem classes, we use decomposition and branch-and-cut to solve the approximating problem within the SAA scheme. Our computational results indicate that the proposed method is successful in solving problems with up to 21694 scenarios to within an estimated 1.0% of optimality. Furthermore, a surprising observation is that the number of optimality cuts required to solve the approximating problem to optimality does not significantly increase with the size of the sample. Therefore, the observed computation times needed to find optimal solutions to the approximating problems grow only linearly with the sample size. As a result, we are able to find provably near-optimal solutions to these difficult stochastic programs using only a moderate amount of computation time. 相似文献
5.
Set-Valued and Variational Analysis - 相似文献
6.
Boris Goldfarb 《Topology and its Applications》2004,140(2-3):267-294
New compactifications of symmetric spaces of noncompact type X are constructed using the asymptotic geometry of the Borel–Serre enlargement. The controlled K-theory associated to these compactifications is used to prove the integral Novikov conjecture for arithmetic groups. 相似文献
7.
8.
9.
Letters in Mathematical Physics - 相似文献
10.