全文获取类型
收费全文 | 24999篇 |
免费 | 600篇 |
国内免费 | 567篇 |
专业分类
化学 | 4540篇 |
晶体学 | 939篇 |
力学 | 461篇 |
综合类 | 61篇 |
数学 | 16161篇 |
物理学 | 4004篇 |
出版年
2023年 | 65篇 |
2022年 | 164篇 |
2021年 | 177篇 |
2020年 | 200篇 |
2019年 | 533篇 |
2018年 | 574篇 |
2017年 | 349篇 |
2016年 | 384篇 |
2015年 | 405篇 |
2014年 | 791篇 |
2013年 | 1676篇 |
2012年 | 786篇 |
2011年 | 2014篇 |
2010年 | 1803篇 |
2009年 | 1710篇 |
2008年 | 1816篇 |
2007年 | 1776篇 |
2006年 | 1367篇 |
2005年 | 1102篇 |
2004年 | 978篇 |
2003年 | 762篇 |
2002年 | 699篇 |
2001年 | 494篇 |
2000年 | 464篇 |
1999年 | 447篇 |
1998年 | 440篇 |
1997年 | 343篇 |
1996年 | 396篇 |
1995年 | 399篇 |
1994年 | 366篇 |
1993年 | 294篇 |
1992年 | 281篇 |
1991年 | 198篇 |
1990年 | 196篇 |
1989年 | 186篇 |
1988年 | 111篇 |
1987年 | 131篇 |
1986年 | 93篇 |
1985年 | 165篇 |
1984年 | 120篇 |
1983年 | 73篇 |
1982年 | 100篇 |
1981年 | 127篇 |
1980年 | 113篇 |
1979年 | 65篇 |
1978年 | 112篇 |
1977年 | 94篇 |
1976年 | 91篇 |
1975年 | 39篇 |
1974年 | 48篇 |
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
201.
Gerhard Ströhmer 《Journal of Mathematical Fluid Mechanics》2006,8(1):36-63
This paper is concerned with the question of linear stability of motionless, spherically symmetric equilibrium states of viscous,
barotropic, self-gravitating fluids. We prove the linear asymptotic stability of such equilibria with respect to perturbations
which leave the angular momentum, momentum, mass and the position of the center of gravity unchanged. We also give some decay
estimates for such perturbations, which we derive from resolvent estimates by means of analytic semigroup theory. 相似文献
202.
We study compact, countably compact, pseudocompact, and functionally bounded sets in extensions of topological groups. A property P is said to be a three space property if, for every topological group G and a closed invariant subgroup N of G, the fact that both groups N and G/N have P implies that G also has P. It is shown that if all compact (countably compact) subsets of the groups N and G/N are metrizable, then G has the same property. However, the result cannot be extended to pseudocompact subsets, a counterexample exists under p=c. Another example shows that extensions of groups do not preserve the classes of realcompact, Dieudonné complete and μ-spaces: one can find a pseudocompact, non-compact Abelian topological group G and an infinite, closed, realcompact subgroup N of G such that G/N is compact and all functionally bounded subsets of N are finite. Several examples given in the article destroy a number of tempting conjectures about extensions of topological groups. 相似文献
203.
S?awomir Solecki 《Topology and its Applications》2007,154(12):2462-2464
Let I0 be the σ-ideal of subsets of a Polish group generated by Borel sets which have perfectly many pairwise disjoint translates. We prove that a Fubini-type theorem holds between I0 and the σ-ideals of Haar measure zero sets and of meager sets. We use this result to give a simple proof of a generalization of a theorem of Balcerzak-Ros?anowski-Shelah stating that I0 on N2 strongly violates the countable chain condition. 相似文献
204.
The category of small covariant functors from simplicial sets to simplicial sets supports the projective model structure [B. Chorny, W.G. Dwyer, Homotopy theory of small diagrams over large categories, preprint, 2005]. In this paper we construct various localizations of the projective model structure and also give a variant for functors from simplicial sets to spectra. We apply these model categories in the study of calculus of functors, namely for a classification of polynomial and homogeneous functors. In the n-homogeneous model structure, the nth derivative is a Quillen functor to the category of spectra with Σn-action. After taking into account only finitary functors—which may be done in two different ways—the above Quillen map becomes a Quillen equivalence. This improves the classification of finitary homogeneous functors by T.G. Goodwillie [T.G. Goodwillie, Calculus. III. Taylor series, Geom. Topol. 7 (2003) 645-711 (electronic)]. 相似文献
205.
Abdelhadi Es-Sarhir 《Journal of Differential Equations》2007,233(1):87-104
This paper deals with perturbations of the Ornstein-Uhlenbeck operator on L2-spaces with respect to a Gaussian measure μ. We perturb the generator of the Ornstein-Uhlenbeck semigroup by a certain unbounded, non-linear drift, and show various properties of the perturbed semigroup such as compactness and positivity. Strong Feller property, existence and uniqueness of an invariant measure are discussed as well. 相似文献
206.
Francesc Carreras 《Discrete Applied Mathematics》2007,155(4):496-505
Different (proper as well as improper) simple games may share any nonseparating blocking family. An interesting question is whether all such proper games on one hand, and all improper ones on the other, are isomorphic. The answer is given here and the automorphisms of the blocking family help us to understand the structure and links of all such games. 相似文献
207.
We prove both geometric ergodicity and regular variation of the stationary distribution for a class of nonlinear stochastic recursions that includes nonlinear AR-ARCH models of order 1. The Lyapounov exponent for the model, the index of regular variation and the spectral measure for the regular variation all are characterized by a simple two-state Markov chain. 相似文献
208.
We continue the studies on the so–called genuine Bernstein–Durrmeyer operators U
n
by establishing a recurrence formula for the moments and by investigating the semigroup T(t) approximated by U
n
. Moreover, for sufficiently smooth functions the degree of this convergence is estimated. We also determine the eigenstructure
of U
n
, compute the moments of T(t) and establish asymptotic formulas.
Received: January 26, 2007. 相似文献
209.
210.
M.A. Batanin 《Advances in Mathematics》2007,211(2):684-725
It is well known that the forgetful functor from symmetric operads to nonsymmetric operads has a left adjoint Sym1 given by product with the symmetric group operad. It is also well known that this functor does not affect the category of algebras of the operad. From the point of view of the author's theory of higher operads, the nonsymmetric operads are 1-operads and Sym1 is the first term of the infinite series of left adjoint functors Symn, called symmetrisation functors, from n-operads to symmetric operads with the property that the category of one object, one arrow, …, one (n−1)-arrow algebras of an n-operad A is isomorphic to the category of algebras of Symn(A).In this paper we consider some geometrical and homotopical aspects of the symmetrisation of n-operads. We follow Getzler and Jones and consider their decomposition of the Fulton-Macpherson operad of compactified real configuration spaces. We construct an n-operadic counterpart of this compactification which we call the Getzler-Jones operad. We study the properties of Getzler-Jones operad and find that it is contractible and cofibrant in an appropriate model category. The symmetrisation of the Getzler-Jones operad turns out to be exactly the operad of Fulton and Macpherson. These results should be considered as an extension of Stasheff's theory of 1-fold loop spaces to n-fold loop spaces n?2. We also show that a space X with an action of a contractible n-operad has a natural structure of an algebra over an operad weakly equivalent to the little n-disks operad. A similar result holds for chain operads. These results generalise the classical Eckman-Hilton argument to arbitrary dimension.Finally, we apply the techniques to the Swiss-Cheese type operads introduced by Voronov and prove analogous results in this case. 相似文献