全文获取类型
收费全文 | 522624篇 |
免费 | 8548篇 |
国内免费 | 1478篇 |
专业分类
化学 | 287509篇 |
晶体学 | 6880篇 |
力学 | 21061篇 |
综合类 | 15篇 |
数学 | 67973篇 |
物理学 | 149212篇 |
出版年
2021年 | 4634篇 |
2020年 | 5376篇 |
2019年 | 5654篇 |
2018年 | 7450篇 |
2017年 | 7150篇 |
2016年 | 11554篇 |
2015年 | 7993篇 |
2014年 | 10934篇 |
2013年 | 25544篇 |
2012年 | 20982篇 |
2011年 | 24803篇 |
2010年 | 16853篇 |
2009年 | 16168篇 |
2008年 | 22422篇 |
2007年 | 22164篇 |
2006年 | 20561篇 |
2005年 | 18654篇 |
2004年 | 17133篇 |
2003年 | 14899篇 |
2002年 | 14358篇 |
2001年 | 14772篇 |
2000年 | 11395篇 |
1999年 | 8948篇 |
1998年 | 7472篇 |
1997年 | 7207篇 |
1996年 | 7133篇 |
1995年 | 6270篇 |
1994年 | 6327篇 |
1993年 | 6074篇 |
1992年 | 6726篇 |
1991年 | 6683篇 |
1990年 | 6396篇 |
1989年 | 6173篇 |
1988年 | 6132篇 |
1987年 | 5968篇 |
1986年 | 5674篇 |
1985年 | 7452篇 |
1984年 | 7531篇 |
1983年 | 5965篇 |
1982年 | 6174篇 |
1981年 | 6103篇 |
1980年 | 5663篇 |
1979年 | 5976篇 |
1978年 | 6146篇 |
1977年 | 5971篇 |
1976年 | 5913篇 |
1975年 | 5434篇 |
1974年 | 5410篇 |
1973年 | 5399篇 |
1972年 | 3743篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
For vector quasivariational inequalities involving multifunctions in topological vector spaces, an existence result is obtained without a monotonicity assumption and with a convergence assumption weaker than semicontinuity. A new type of quasivariational inequality is proposed. Applications to quasicomplementarity problems and traffic network equilibria are considered. In particular, definitions of weak and strong Wardrop equilibria are introduced for the case of multivalued cost functions. 相似文献
992.
We study a combinatorially defined double complex structure on the ordered chains of any simplicial complex. Its columns are related to the cell complex Kn whose face poset is isomorphic to the subword ordering on words without repetition from an alphabet of size n. This complex is shellable and as an application we give a representation theoretic interpretation for derangement numbers and a related symmetric function considered by Désarménien and Wachs [11].
We analyze the two spectral sequences arising from the double complex in the case of the bar resolution for a group. This spectral sequence converges to the cohomology of the group and provides a method for computing group cohomology in terms of the cohomology of subgroups. Its behavior is influenced by the complex of oriented chains of the simplicial complex of finite subsets of the group, and we examine the Ext class of this complex. 相似文献
993.
We shall answer several questions concerning additive or multiplicative commutators in a division ring which are algebraic of bounded degree over its center. 相似文献
994.
Panos M. Pardalos Wanpracha Chaovalitwongse Leonidas D. Iasemidis J. Chris Sackellares Deng-Shan Shiau Paul R. Carney Oleg A. Prokopyev Vitaliy A. Yatsenko 《Mathematical Programming》2004,101(2):365-385
There is growing evidence that temporal lobe seizures are preceded by a preictal transition, characterized by a gradual dynamical change from asymptomatic interictal state to seizure. We herein report the first prospective analysis of the online automated algorithm for detecting the preictal transition in ongoing EEG signals. Such, the algorithm constitutes a seizure warning system. The algorithm estimates STLmax, a measure of the order or disorder of the signal, of EEG signals recorded from individual electrode sites. The optimization techniques were employed to select critical brain electrode sites that exhibit the preictal transition for the warning of epileptic seizures. Specifically, a quadratically constrained quadratic 0-1 programming problem is formulated to identify critical electrode sites. The automated seizure warning algorithm was tested in continuous, long-term EEG recordings obtained from 5 patients with temporal lobe epilepsy. For individual patient, we use the first half of seizures to train the parameter settings, which is evaluated by ROC (Receiver Operating Characteristic) curve analysis. With the best parameter setting, the algorithm applied to all cases predicted an average of 91.7% of seizures with an average false prediction rate of 0.196 per hour. These results indicate that it may be possible to develop automated seizure warning devices for diagnostic and therapeutic purposes.Mathematics Subject Classification (1991):20E28, 20G40, 20C20 相似文献
995.
996.
997.
Fabio A. C. C. Chalub Peter A. Markowich Benoît Perthame Christian Schmeiser 《Monatshefte für Mathematik》2004,142(1-2):123-141
Kinetic models for chemotaxis, nonlinearly coupled to a Poisson equation for the chemo-attractant density, are considered. Under suitable assumptions on the turning kernel (including models introduced by Othmer, Dunbar and Alt), convergence in the macroscopic limit to a drift-diffusion model is proven. The drift-diffusion models derived in this way include the classical Keller-Segel model. Furthermore, sufficient conditions for kinetic models are given such that finite-time-blow-up does not occur. Examples are given satisfying these conditions, whereas the macroscopic limit problem is known to exhibit finite-time-blow-up. The main analytical tools are entropy techniques for the macroscopic limit as well as results from potential theory for the control of the chemo-attractant density.Present address: Centro de Matemática e Aplicações Fundamentais, Universidade de Lisboa, Av. Prof. Gama Pinto 2, 1649-003, Lisboa, Portugal 相似文献
998.
The exponential functional of simple, symmetric random walks with negative
drift is an infinite polynomial Y = 1 + ξ1 + ξ1ξ2 + ξ1ξ2ξ3 + ⋯ of independent
and identically distributed non-negative random variables. It has moments that are
rational functions of the variables μ
k
= E(ξ
k
) < 1 with universal coefficients. It
turns out that such a coefficient is equal to the number of permutations with descent
set defined by the multiindex of the coefficient. A recursion enumerates all numbers
of permutations with given descent sets in the form of a Pascal-type triangle.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
999.
Periodica Mathematica Hungarica - In our paper we study the usage of partially defined Boolean functions (PDBFs) for generating cryptographically strong Boolean functions. A PDBF can be considered... 相似文献
1000.
A note on a generalized Douglas space 总被引:1,自引:0,他引:1
Periodica Mathematica Hungarica - 相似文献