全文获取类型
收费全文 | 34988篇 |
免费 | 3946篇 |
国内免费 | 4142篇 |
专业分类
化学 | 10858篇 |
晶体学 | 161篇 |
力学 | 3093篇 |
综合类 | 566篇 |
数学 | 14091篇 |
物理学 | 14307篇 |
出版年
2024年 | 75篇 |
2023年 | 333篇 |
2022年 | 542篇 |
2021年 | 792篇 |
2020年 | 952篇 |
2019年 | 916篇 |
2018年 | 920篇 |
2017年 | 1060篇 |
2016年 | 1259篇 |
2015年 | 1060篇 |
2014年 | 1644篇 |
2013年 | 2681篇 |
2012年 | 1798篇 |
2011年 | 2238篇 |
2010年 | 1932篇 |
2009年 | 2463篇 |
2008年 | 2480篇 |
2007年 | 2535篇 |
2006年 | 2192篇 |
2005年 | 1784篇 |
2004年 | 1491篇 |
2003年 | 1511篇 |
2002年 | 1369篇 |
2001年 | 1129篇 |
2000年 | 1077篇 |
1999年 | 958篇 |
1998年 | 856篇 |
1997年 | 653篇 |
1996年 | 481篇 |
1995年 | 425篇 |
1994年 | 355篇 |
1993年 | 333篇 |
1992年 | 311篇 |
1991年 | 246篇 |
1990年 | 246篇 |
1989年 | 230篇 |
1988年 | 192篇 |
1987年 | 179篇 |
1986年 | 130篇 |
1985年 | 159篇 |
1984年 | 144篇 |
1983年 | 65篇 |
1982年 | 129篇 |
1981年 | 103篇 |
1980年 | 87篇 |
1979年 | 121篇 |
1978年 | 86篇 |
1977年 | 92篇 |
1976年 | 76篇 |
1973年 | 55篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
介绍了13~18世纪物理学史和科技史上曾名噪一时的第一类永动机的设计方案的破灭.第一类永动机幻梦破灭的历史引起了人们的反思与启示,有力地促进了19世纪中叶能量转化和守恒定律的确立. 相似文献
84.
E. A. Bailov N. Temirgaliev 《Computational Mathematics and Mathematical Physics》2006,46(9):1515-1525
Sharp estimates (in the power scale) are obtained for the discretization error in the solutions to Poisson’s equation whose right-hand side belongs to a Korobov class. Compared to the well-known Korobov estimate, the order is almost doubled and has an ultimate value in the power scale. 相似文献
85.
It is long known that the Fokker-Planck equation with prescribed constant coefficients of diffusion and linear friction describes
the ensemble average of the stochastic evolutions in velocity space of a Brownian test particle immersed in a heat bath of
fixed temperature. Apparently, it is not so well known that the same partial differential equation, but now with constant
coefficients which are functionals of the solution itself rather than being prescribed, describes the kinetic evolution (in
the N→∞ limit) of an
isolated
N-particle system with certain stochastic interactions. Here we discuss in detail this recently discovered interpretation.
An erratum to this article can be found at 相似文献
86.
Signed graphs for portfolio analysis in risk management 总被引:1,自引:0,他引:1
Harary Frank; Lim Meng-Hiot; Wunsch Donald C. 《IMA Journal of Management Mathematics》2002,13(3):201-210
We introduce the notion of structural balance for signed graphsin the context of portfolio analysis. A portfolio of securitiescan be represented as a signed graph with the nodes denotingthe securities and the edges representing the correlation betweenthe securities. With signed graphs, the characteristics of aportfolio from a risk management perspective can be uncoveredfor analysis purposes. It is shown that a portfolio characterizedby a signed graph of positive and negative edges that is structurallybalanced is characteristically more predictable. Investors whoundertake a portfolio position with all positively correlatedsecurities do so with the intention to speculate on the upside(or downside). If the portfolio consists of negative edges andis balanced, then it is likely that the position has a hedgingdisposition within it. On the other hand, an unbalanced signedgraph is representative of an investment portfolio which ischaracteristically unpredictable. 相似文献
87.
A Modified Quasi-Newton Method for Structured Optimization with Partial Information on the Hessian 总被引:2,自引:0,他引:2
This paper develops a modified quasi-Newton method for structured unconstrained optimization with partial information on the
Hessian, based on a better approximation to the Hessian in current search direction. The new approximation is decided by both
function values and gradients at the last two iterations unlike the original one which only uses the gradients at the last
two iterations. The modified method owns local and superlinear convergence. Numerical experiments show that the proposed method
is encouraging comparing with the methods proposed in [4] for structured unconstrained optimization
Presented at the 6th International Conference on Optimization: Techniques and Applications, Ballarat, Australia, December
9–11, 2004 相似文献
88.
89.
Johan Helsing 《BIT Numerical Mathematics》2006,46(2):307-323
A sparse mesh-neighbour based approximate inverse preconditioner is proposed for a type of dense matrices whose entries come
from the evaluation of a slowly decaying free space Green’s function at randomly placed points in a unit cell. By approximating
distant potential fields originating at closely spaced sources in a certain way, the preconditioner is given properties similar
to, or better than, those of a standard least squares approximate inverse preconditioner while its setup cost is only that
of a diagonal block approximate inverse preconditioner. Numerical experiments on iterative solutions of linear systems with
up to four million unknowns illustrate how the new preconditioner drastically outperforms standard approximate inverse preconditioners
of otherwise similar construction, and especially so when the preconditioners are very sparse.
AMS subject classification (2000) 65F10, 65R20, 65F35, 78A30 相似文献
90.
D. Yafaev 《Proceedings Mathematical Sciences》2002,112(1):245-255
We find an explicit function approximating at high energies the kernel of the scattering matrix with arbitrary accuracy. Moreover,
the same function gives all diagonal singularities of the kernel of the scattering matrix in the angular variables.
This paper is dedicated to Jean-Michel Combes on the occasion of his sixtieth birthday. 相似文献