全文获取类型
收费全文 | 25809篇 |
免费 | 3086篇 |
国内免费 | 3375篇 |
专业分类
化学 | 9816篇 |
晶体学 | 105篇 |
力学 | 2107篇 |
综合类 | 189篇 |
数学 | 9054篇 |
物理学 | 10999篇 |
出版年
2024年 | 83篇 |
2023年 | 278篇 |
2022年 | 642篇 |
2021年 | 702篇 |
2020年 | 858篇 |
2019年 | 802篇 |
2018年 | 784篇 |
2017年 | 848篇 |
2016年 | 996篇 |
2015年 | 880篇 |
2014年 | 1311篇 |
2013年 | 2122篇 |
2012年 | 1389篇 |
2011年 | 1640篇 |
2010年 | 1308篇 |
2009年 | 1654篇 |
2008年 | 1707篇 |
2007年 | 1776篇 |
2006年 | 1476篇 |
2005年 | 1236篇 |
2004年 | 1013篇 |
2003年 | 1019篇 |
2002年 | 942篇 |
2001年 | 750篇 |
2000年 | 760篇 |
1999年 | 638篇 |
1998年 | 581篇 |
1997年 | 438篇 |
1996年 | 303篇 |
1995年 | 293篇 |
1994年 | 247篇 |
1993年 | 247篇 |
1992年 | 232篇 |
1991年 | 187篇 |
1990年 | 201篇 |
1989年 | 192篇 |
1988年 | 167篇 |
1987年 | 169篇 |
1986年 | 146篇 |
1985年 | 148篇 |
1984年 | 145篇 |
1983年 | 86篇 |
1982年 | 121篇 |
1981年 | 110篇 |
1980年 | 98篇 |
1979年 | 102篇 |
1978年 | 78篇 |
1977年 | 76篇 |
1976年 | 70篇 |
1973年 | 61篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Nobuyuki Hanaki 《Complexity》2004,9(5):41-50
This article seeks to ascertain whether the strategy‐learning model of Hanaki, Sethi, Erev, and Peterhansl (2003) better accounts for observed behavior than do the various action‐learning models. It does so by measuring the goodness‐of‐fit of the models' predictions against published experimental results for such games as Coordination, Prisoner's Dilemma, and Chicken. The fit is measured via the mean squared deviation (MSD) between the observed behavior and the one predicted by the model. The results show that, for Chicken, the strategy‐learning model fits the observed data much better than do the action‐learning models. The best action‐learning model, on the other hand, fits the observed data well in Coordination. Overall, the strength of the strategy‐learning model is best shown in games where alternations between the two stage‐game Nash equilibria are often observed in the laboratory experiments. © 2004 Wiley Periodicals, Inc. Complexity 9: 41–50, 2004 相似文献
52.
We study the elastic responses of double-(ds) and single-stranded (ss) DNA at external force fields. A double-strand-polymer
elastic model is constructed and solved by path integral methods and Monte Carlo simulations to understand the entropic elasticity,
cooperative extensibility, and supercoiling property of dsDNA. The good agreement with experiments indicates that short-ranged
base-pair stacking interaction is crucial for the stability and the high deformability of dsDNA. Hairpin-coil transition in
ssDNA is studied with generating function method. A threshold force is needed to pull the ssDNA hairpin patterns, stabilized
by base pairing and base-pair stacking, into random coils. This phase transition is predicted to be of first order for stacking
potential higher than some critical level, in accordance with experimental observations. 相似文献
53.
Alfonso Carriazo Luis M. Ferná ndez 《Proceedings of the American Mathematical Society》2004,132(11):3327-3336
In this paper we present an interesting relationship between graph theory and differential geometry by defining submanifolds of almost Hermitian manifolds associated with certain kinds of graphs. We show some results about the possibility of a graph being associated with a submanifold and we use them to characterize CR-submanifolds by means of trees. Finally, we characterize submanifolds associated with graphs in a four-dimensional almost Hermitian manifold.
54.
55.
B. Ananthanarayan 《Pramana》2003,61(5):911-920
A review of chiral perturbation theory and recent developments on the comparison of its predictions with experiment is presented.
Some interesting topics with scope for further elaboration are touched upon. 相似文献
56.
57.
类比方法与光的本性的探索 总被引:2,自引:0,他引:2
简要回顾了人类对光的本性的探索历程,介绍了物理学家在研究过程中对类比方法的运用。 相似文献
58.
高斯光束计算平板波导自由传输区远场分布及其修正 总被引:2,自引:2,他引:0
对近轴近似条件下求解亥姆霍兹方程得到的高斯光束显式传播公式做了分析,同时,基于基尔霍夫衍射理论,在菲涅耳近似的条件下给出了相应的高斯光束在远场的传播公式,在此基础上,对近轴近似条件做出了定量分析,给出了这个近似条件引入的误差,提出了一种计算高斯光束远场分布的修正方法,并采用有限差分-光束传播方法(FD-BPM)来检验各种方法的准确性。把这种修正方法应用到平面光集成波导器件,如阵列波导光栅(AWG)、蚀刻衍射光栅(EDG)等器件的设计和模拟中,可以大大降低工作的复杂性,同时可以得到精确的结果。 相似文献
59.
In this paper, we present some counterexamples which show that there is no theory on the spectrum of homogeneous compact operators which parallels the Riesz-Schauder theory on the spectrum of linear compact operators. These counterexamples also illustrate that it is impossible to study in a unified setting the Fucik spectrum of the Laplacian: -△w = au+ - bu- inΩand u = 0 on (?)Ω, as well as the spectrum of the p-Laplacian: -div(|(?)u| p-2(?)u) = λ|u|p-2u and u = 0 on (?)Ω. 相似文献
60.
Mathematical Notes - 相似文献