全文获取类型
收费全文 | 7993篇 |
免费 | 675篇 |
国内免费 | 581篇 |
专业分类
化学 | 1300篇 |
晶体学 | 76篇 |
力学 | 3606篇 |
综合类 | 91篇 |
数学 | 1739篇 |
物理学 | 2437篇 |
出版年
2024年 | 9篇 |
2023年 | 84篇 |
2022年 | 156篇 |
2021年 | 289篇 |
2020年 | 241篇 |
2019年 | 157篇 |
2018年 | 166篇 |
2017年 | 226篇 |
2016年 | 279篇 |
2015年 | 217篇 |
2014年 | 288篇 |
2013年 | 522篇 |
2012年 | 263篇 |
2011年 | 378篇 |
2010年 | 308篇 |
2009年 | 404篇 |
2008年 | 450篇 |
2007年 | 473篇 |
2006年 | 480篇 |
2005年 | 407篇 |
2004年 | 399篇 |
2003年 | 350篇 |
2002年 | 317篇 |
2001年 | 301篇 |
2000年 | 317篇 |
1999年 | 260篇 |
1998年 | 209篇 |
1997年 | 196篇 |
1996年 | 163篇 |
1995年 | 124篇 |
1994年 | 115篇 |
1993年 | 110篇 |
1992年 | 98篇 |
1991年 | 90篇 |
1990年 | 57篇 |
1989年 | 51篇 |
1988年 | 57篇 |
1987年 | 49篇 |
1986年 | 34篇 |
1985年 | 27篇 |
1984年 | 31篇 |
1983年 | 13篇 |
1982年 | 23篇 |
1981年 | 21篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1957年 | 3篇 |
排序方式: 共有9249条查询结果,搜索用时 203 毫秒
1.
2.
3.
4.
Nonclassical light states are important for both conceptual and practical reasons: they are basic ingredients in testing and exploring quantum foundations, and are crucial resources in quantum technologies. Various useful criteria have been developed to detect nonclassicality in the literature, and several meaningful measures of nonclassicality have been introduced and measured experimentally. In this work, by use of a non-Hermitian generalization of the Wigner-Yanase-Dyson skew information and playing with operator ordering in evaluating average photon number, we develop a novel family of criteria for detecting nonclassicality of light based on Lieb's concavity, which is a deep and powerful result concerning interaction between quantum states and observables. We elucidate the information-theoretic as well as the physical meaning of the criteria, and illustrate their effectiveness in capturing and quantifying nonclassicality of various important light states. 相似文献
5.
We give a sheaf theoretic interpretation of Potts models with external magnetic field, in terms of constructible sheaves and their Euler characteristics. We show that the polynomial countability question for the hypersurfaces defined by the vanishing of the partition function is affected by changes in the magnetic field: elementary examples suffice to see non-polynomially countable cases that become polynomially countable after a perturbation of the magnetic field. The same recursive formula for the Grothendieck classes, under edge-doubling operations, holds as in the case without magnetic field, but the closed formulae for specific examples like banana graphs differ in the presence of magnetic field. We give examples of computation of the Euler characteristic with compact support, for the set of real zeros, and find a similar exponential growth with the size of the graph. This can be viewed as a measure of topological and algorithmic complexity. We also consider the computational complexity question for evaluations of the polynomial, and show both tractable and NP-hard examples, using dynamic programming. 相似文献
6.
7.
Lu Chuanrong 《数学年刊B辑(英文版)》1997,18(1):71-78
Let $\{\xi_{\bold t}, {\bold t}
\in {\bold Z}^d\}$ be a nonuniform $\varphi$-mixing strictly stationary
real random field with
$E\xi_{\bold 0}=0, E|\xi_{\bold 0}|^{2+\delta}<\infty$ for some
$0<\delta<1$. A sufficient
condition is given for the sequence of partial sum set-indexed process
$\{Z_n(A),\ A\in \Cal A\}$ to converge to Brownian motion. By a direct
calculation, the author shows
that the result holds for a more general class of set index ${\Cal A}$, where
${\Cal A}$ is assumed only to have the metric entropy exponent $r, 0相似文献
8.
9.
10.
Within the framework of a piecewise homogeneous body model, with the use of three-dimensional geometrically nonlinear exact equations of elasticity theory, a method for determining the stress—strain state in unidirectional fibrous composites with locally curved fibers is developed for the case where the interaction between the fibers is neglected. All the investigations are carried out for an infinite elastic body containing a single locally curved fiber. Numerical results illustrating the effect of geometrical nonlinearity on the distribution of the self-balanced normal and shear stresses acting on the interface and arising as a result of local curving of the fiber are presented.__________Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 41, No. 4, pp. 433–448, July–August, 2005. 相似文献