全文获取类型
收费全文 | 4113篇 |
免费 | 350篇 |
国内免费 | 437篇 |
专业分类
化学 | 1156篇 |
晶体学 | 18篇 |
力学 | 119篇 |
综合类 | 138篇 |
数学 | 2483篇 |
物理学 | 986篇 |
出版年
2024年 | 6篇 |
2023年 | 20篇 |
2022年 | 76篇 |
2021年 | 88篇 |
2020年 | 104篇 |
2019年 | 96篇 |
2018年 | 102篇 |
2017年 | 114篇 |
2016年 | 116篇 |
2015年 | 77篇 |
2014年 | 166篇 |
2013年 | 354篇 |
2012年 | 225篇 |
2011年 | 237篇 |
2010年 | 174篇 |
2009年 | 244篇 |
2008年 | 267篇 |
2007年 | 274篇 |
2006年 | 241篇 |
2005年 | 211篇 |
2004年 | 211篇 |
2003年 | 209篇 |
2002年 | 193篇 |
2001年 | 130篇 |
2000年 | 124篇 |
1999年 | 143篇 |
1998年 | 126篇 |
1997年 | 107篇 |
1996年 | 78篇 |
1995年 | 55篇 |
1994年 | 58篇 |
1993年 | 40篇 |
1992年 | 35篇 |
1991年 | 26篇 |
1990年 | 22篇 |
1989年 | 26篇 |
1988年 | 17篇 |
1987年 | 18篇 |
1986年 | 11篇 |
1985年 | 8篇 |
1984年 | 13篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 9篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1977年 | 6篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1936年 | 2篇 |
排序方式: 共有4900条查询结果,搜索用时 0 毫秒
1.
In this paper, the authors studied certain properties of the estimate of Liang and Krishnaiah (1985, J. Multivariate Anal. 16, 162–172) for multivariate binary density. An alternative shrinkage estimate is also obtained. The above results are generalized to general orthonormal systems. 相似文献
2.
We examine two criteria for balance of a gain graph, one based on binary cycles and one on circles. The graphs for which each criterion is valid depend on the set of allowed gain groups. The binary cycle test is invalid, except for forests, if any possible gain group has an element of odd order. Assuming all groups are allowed, or all abelian groups, or merely the cyclic group of order 3, we characterize, both constructively and by forbidden minors, the graphs for which the circle test is valid. It turns out that these three classes of groups have the same set of forbidden minors. The exact reason for the importance of the ternary cyclic group is not clear. © 2005 Wiley Periodicals, Inc. J Graph Theory 相似文献
3.
Shunlong Luo 《Foundations of Physics》2002,32(11):1757-1772
We formulate an elementary statistical game which captures the essence of some fundamental quantum experiments such as photon polarization and spin measurement. We explore and compare the significance of the principle of maximum Shannon entropy and the principle of minimum Fisher information in solving such a game. The solution based on the principle of minimum Fisher information coincides with the solution based on an invariance principle, and provides an informational explanation of Malus' law for photon polarization. There is no solution based on the principle of maximum Shannon entropy. The result demonstrates the merits of Fisher information, and the demerits of Shannon entropy, in treating some fundamental quantum problems. It also provides a quantitative example in support of a general philosophy: Nature intends to hide Fisher information, while obeying some simple rules. 相似文献
4.
弱拓扑和强可容许拓扑之间的一个关系 总被引:2,自引:0,他引:2
本文对局部凸空间X及其对偶X′,建立了弱拓扑σ(X,X′)和强拓扑β(X,X′)之间的一个新关系,改进了有关(X,X′)--可容许拓扑全体上的不变性结果。 相似文献
5.
Non-isothermal short-range-order kinetics of binary alloys as influenced by solute-vacancy complexes
A model describing the roles of bound and unbound vacancies is proposed in order to predict defect decay and short-range-order
kinetics of quenched binary alloys during linear heating experiments. This is an alternative treatment of a previous approach.
The model has been applied to the differential scanning calorimetry (DSC) curves of Cu-5 at.% Zn quenched from different temperatures.
An expression to calculate the activation energy for migration of solute-vacancy complexes was also developed which make use
of DSC trace data. A value of 89.12±0.32 kJ mol-1 was obtained for the above alloy. The relative contribution of bound and unbound vacancies to partition of effective activation
energy corresponding to the ordering process as influenced by quenching temperature was also assessed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
曾六川 《高等学校计算数学学报(英文版)》2003,12(1)
The purpose of this paper is to investigate the problem of approximating fixed points of non-Lipschitizian asymptotically pseudocontractive mappings in an arbitrary real Banach space by the modified Ishikawa iterative sequences with errors. 相似文献
7.
In basin modelling the thermodynamics of a multicomponent multiphase fluid flux are computationally too expensive when derived from an equation of state and the Gibbs equality constraints. In this article we present a novel implicit molar mass formulation technique using binary mixture thermodynamics. The two proposed solution methods, with and without cross derivative terms between components, are based on a preconditioned Newton‐GMRES scheme for each time‐step with analytical computation of the derivatives. These new algorithms reduce significantly the numerical effort for the computation of the molar masses, and we illustrate the behavior of these methods with numerical computations. Copyright © 2004 John Wiley & Sons Ltd. 相似文献
8.
Fukuji Higashi Kanako Sugishita 《Journal of polymer science. Part A, Polymer chemistry》2004,42(1):44-51
A two‐stage co‐oligomerization of the oligomers initially formed from an equimolar mixture of isophthalic acid (IPA) and terephthalic acid (TPA) and 2,2‐bis(4‐hydroxyphenyl)propane (BPA, 50 mol %) with bisphenols (BPs, 20 mol %) was carried out using a tosyl chloride/dimethylformamide/pyridine condensing agent. The distributions of the resulting oligomers (nx‐mers), which were quenched with methanol, were determined by a combination of gel permeation chromatography (GPC) and NMR. These distributions (presented by molar percentage) were conveniently calculated with the equation nx (mol %) = nx (% mol by GPC) × n0 (mol % by NMR)/n0 (% mol by GPC), where nx (% mol) = nx (wt % by GPC)/its molecular weight. The results showed the distributions of the preformed IPA/TPA‐BPA oligomers to be in fairly good accord with those obtained directly from GPC and to be supported by the NMR results. The calculation was applied to the co‐oligomers prepared up to a reaction of 0.7, at which there was an increase in the number of higher oligomers indivisible by GPC and the distributions could no longer be determined by molar percentage. The calculated distributions are discussed in relation to the results of copolycondensation. The sequence distributions in the resulting co‐oligomers, which were also examined by NMR, are compared with those in the copolymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 44–51, 2004 相似文献
9.
10.
Shea-Ming Oon 《Periodica Mathematica Hungarica》2004,49(2):107-118
In this paper we study some pseudo-random properties related to the prime factors of integers. We prove some results concerning the well distribution of the greatest prime factor modulo 4, and give some computational insight on the correlations, which seem to be beyond reach of proof. 相似文献