全文获取类型
收费全文 | 3306篇 |
免费 | 244篇 |
国内免费 | 452篇 |
专业分类
化学 | 421篇 |
晶体学 | 10篇 |
力学 | 109篇 |
综合类 | 61篇 |
数学 | 2828篇 |
物理学 | 573篇 |
出版年
2024年 | 1篇 |
2023年 | 18篇 |
2022年 | 34篇 |
2021年 | 50篇 |
2020年 | 67篇 |
2019年 | 62篇 |
2018年 | 90篇 |
2017年 | 109篇 |
2016年 | 70篇 |
2015年 | 54篇 |
2014年 | 112篇 |
2013年 | 377篇 |
2012年 | 132篇 |
2011年 | 149篇 |
2010年 | 149篇 |
2009年 | 215篇 |
2008年 | 241篇 |
2007年 | 198篇 |
2006年 | 198篇 |
2005年 | 199篇 |
2004年 | 158篇 |
2003年 | 166篇 |
2002年 | 203篇 |
2001年 | 150篇 |
2000年 | 129篇 |
1999年 | 131篇 |
1998年 | 116篇 |
1997年 | 92篇 |
1996年 | 68篇 |
1995年 | 44篇 |
1994年 | 33篇 |
1993年 | 25篇 |
1992年 | 20篇 |
1991年 | 10篇 |
1990年 | 7篇 |
1989年 | 16篇 |
1988年 | 15篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 12篇 |
1984年 | 12篇 |
1983年 | 5篇 |
1982年 | 13篇 |
1981年 | 6篇 |
1980年 | 9篇 |
1979年 | 7篇 |
1978年 | 8篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1973年 | 1篇 |
排序方式: 共有4002条查询结果,搜索用时 31 毫秒
61.
62.
63.
Timothy Buttsworth 《Mathematische Nachrichten》2019,292(4):747-759
Let G be a three‐dimensional unimodular Lie group, and let T be a left‐invariant symmetric (0,2)‐tensor field on G. We provide the necessary and sufficient conditions on T for the existence of a pair consisting of a left‐invariant Riemannian metric g and a positive constant c such that , where is the Ricci curvature of g. We also discuss the uniqueness of such pairs and show that, in most cases, there exists at most one positive constant c such that is solvable for some left‐invariant Riemannian metric g. 相似文献
64.
65.
Whether Fittsʼ law, a well-known model of human pointing movement, is a logarithmic law or a power law has remained unclear so far. In two widely cited papers, Meyer et al. have claimed that the power model they derived from their celebrated stochastic optimized-submovement theory encompasses the logarithmic model as a limiting case. We show that Meyer et al.ʼs theory implies in fact a quasi-logarithmic, rather than quasi-power model, the two models being not equivalent. 相似文献
66.
John P. Lehoczky 《The Journal of mathematical sociology》2013,37(2):139-157
A class of models called interactive Markov chains is studied in both discrete and continuous time. These models were introduced by Conlisk and serve as a rich class for sociological modeling, because they allow for interactions among individuals. In discrete time, it is proved that the Markovian processes converge to a deterministic process almost surely as the population size becomes infinite. More importantly, the normalized process is shown to be asymptotically normal with specified mean vector and covariance matrix. In continuous time, the chain is shown to converge weakly to a diffusion process with specified drift and scale terms. The distributional results will allow for the construction of a likelihood function from interactive Markov chain data, so these results will be important for questions of statistical inference. An example from manpower planning is given which indicates the use of this theory in constructing and evaluating control policies for certain social systems. 相似文献
67.
68.
Lanthanide Identity Governs Guest-Induced Dimerization in LnIII[15-MC
N(L-pheHA)-5])3+ Metallacrowns
Prof. Carmelo Sgarlata Bernadette L. Schneider Valeria Zito Dr. Rossella Migliore Prof. Matteo Tegoni Prof. Vincent L. Pecoraro Prof. Giuseppe Arena 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(70):17669-17675
Series of lanthanide-containing metallic coordination complexes are frequently presented as structurally analogous, due to the similar chemical and coordinative properties of the lanthanides. In the case of chiral (LnIII[15-MC N(L-pheHA)-5])3+ metallacrowns (MCs), which are well established supramolecular hosts, the formation of dimers templated by a dicarboxylate guest (muconate) in solution of neutral pH is herein shown to have a unique dependence on the identity of the MC's central lanthanide. Calorimetric data and nuclear magnetic resonance diffusion studies demonstrate that MCs containing larger or smaller lanthanides as the central metal only form monomeric host-guest complexes whereas analogues with intermediate lanthanides (for example, Eu, Gd, Dy) participate in formation of dimeric host-guest-host compartments. The driving force for the dimerization event across the series is thought to be a competition between formation of highly stable MCs (larger lanthanides) and optimally linked bridging guests (smaller lanthanides). 相似文献
69.
70.