全文获取类型
收费全文 | 5425篇 |
免费 | 236篇 |
国内免费 | 27篇 |
专业分类
化学 | 3865篇 |
晶体学 | 40篇 |
力学 | 155篇 |
综合类 | 2篇 |
数学 | 675篇 |
物理学 | 951篇 |
出版年
2023年 | 44篇 |
2022年 | 43篇 |
2021年 | 68篇 |
2020年 | 99篇 |
2019年 | 89篇 |
2018年 | 53篇 |
2017年 | 62篇 |
2016年 | 170篇 |
2015年 | 147篇 |
2014年 | 166篇 |
2013年 | 264篇 |
2012年 | 315篇 |
2011年 | 377篇 |
2010年 | 206篇 |
2009年 | 187篇 |
2008年 | 299篇 |
2007年 | 312篇 |
2006年 | 297篇 |
2005年 | 262篇 |
2004年 | 239篇 |
2003年 | 179篇 |
2002年 | 188篇 |
2001年 | 116篇 |
2000年 | 113篇 |
1999年 | 105篇 |
1998年 | 66篇 |
1997年 | 51篇 |
1996年 | 54篇 |
1995年 | 79篇 |
1994年 | 70篇 |
1993年 | 62篇 |
1992年 | 69篇 |
1991年 | 60篇 |
1990年 | 51篇 |
1989年 | 44篇 |
1988年 | 26篇 |
1987年 | 35篇 |
1985年 | 45篇 |
1984年 | 25篇 |
1983年 | 31篇 |
1982年 | 35篇 |
1981年 | 28篇 |
1980年 | 34篇 |
1979年 | 36篇 |
1978年 | 34篇 |
1977年 | 47篇 |
1976年 | 28篇 |
1975年 | 31篇 |
1974年 | 38篇 |
1973年 | 28篇 |
排序方式: 共有5688条查询结果,搜索用时 453 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.
The modification of the number field sieve which Joux and Lercier recently used to compute logarithms in a prime field of a record 120 decimal digits makes use of the notion of a virtual logarithm of a prime ideal in a number ring. We provide necessary and sufficient conditions for their method to succeed and give an explicit formula for the virtual logarithm of an ideal. 相似文献
4.
A one-dimensional bulk reaction model for the oxidation of nickeltitanium is formulated, with preferential oxidation of titaniumbeing included. The modelling is directed at the better understandingof the dominant mechanisms involved in the oxidation processand their significance for the biocompatibility of the alloy.Two different regimes for the relative diffusivities of oxygenand the metals are investigated. By assuming fast bulk reactions,different asymptotic structures emerge in different parameterregimes and the resulting models take the form of moving boundaryproblems. Different profiles of nickel concentration are obtained:in particular a nickel-rich layer (observed in practice) ispresent below the oxide/metal interface for the case when oxygenand the metals diffuse at comparable rates. 相似文献
5.
6.
Marcel Oliver 《Theoretical and Computational Fluid Dynamics》1997,9(3-4):311-324
The so-called lake equations arise as the shallow-water limit of the rigid-lid equations—three-dimensional Euler equations
with a rigid-lid upper boundary condition—in a horizontally periodic basin with bottom topography. We prove an a priori estimate in the Sobolev space H
m
for m≥ 3 which shows that a solution to the rigid-lid equations can be approximated by a solution of the lake equations for an
interval of time which can be estimated in terms of the initial deviation from a columnar configuration and the magnitude
of the initial data in H
m
, the gradient of the bottom topography in H
m+1
, and the aspect ratio of the basin. In particular, any solution to the lake equations remains close to some solution of the
rigid-lid equations for an interval of time that can be made arbitrarily large by choosing the aspect ratio of the basin small.
Received 10 October 1996 and accepted 15 May 1997 相似文献
7.
The consecutive reactions of (CH3)2Si(OC2H5)2 and CH3Si(OC2H5)3 with methoxide ions were investigated in methanol solutions. The reverse transesterification reactions with ethoxide ions could be neglected in both cases since the concentration of ethoxide in methanol solution was assumed to be low due to the fast equilibrium reaction C2H5O? + CH3OH ? C2H5OH + CH3O?. The progress of the reactions was followed by monitoring the formation of ethanol with a Fourier-transform infrared spectrometer. All rate constants were determined at 295 K. The reactions between the dialkoxydimethylsilanes and methoxide ions were assumed to consist of two consecutive steps that can be represented by the net reaction; (CH3)2Si(OC2H5)2 + 2CH3O? → (CH3)2Si(OCH3)2 + 2C2H5O?. The two consecutive rate constants were established as 1.93 ± 0.12M?1s?1 and 1.00 ± 0.12M?1s?1, respectively. The consecutive rate constants for the reactions between the trialkoxymethylsilanes and methoxide ions can be written according to the total reaction; CH3Si(OC2H5)3 + 3CH3O? → CH3Si(OCH3)3 + 3C2H5O?. The three rate constants corresponding to each consecutive step were established as 1.12 ± 0.09 M?1s?1, 0.82 ± 0.10 M?1s?1, and 0.51 ± 0.06 M?1s?1, respectively. © 1995 John Wiley & Sons, Inc. 相似文献
8.
Cheriyan and Hagerup developed a randomized algorithm to compute the maximum flow in a graph with n nodes and m edges in O(mn + n2 log2n) expected time. The randomization is used to efficiently play a certain combinatorial game that arises during the computation. We give a version of their algorithm where a general version of their game arises. Then we give a strategy for the game that yields a deterministic algorithm for computing the maximum flow in a directed graph with n nodes and m edges that runs in time O(mn(logm/n log nn)). Our algorithm gives an O(mn) deterministic algorithm for all m/n = Ω(nε) for any positive constant ε, and is currently the fastest deterministic algorithm for computing maximum flow as long as m/n = ω(log n). 相似文献
9.
10.