收费全文 | 19677篇 |
免费 | 2201篇 |
国内免费 | 2025篇 |
化学 | 2217篇 |
晶体学 | 30篇 |
力学 | 1718篇 |
综合类 | 502篇 |
数学 | 13580篇 |
物理学 | 5856篇 |
2024年 | 22篇 |
2023年 | 156篇 |
2022年 | 258篇 |
2021年 | 347篇 |
2020年 | 399篇 |
2019年 | 414篇 |
2018年 | 433篇 |
2017年 | 562篇 |
2016年 | 637篇 |
2015年 | 491篇 |
2014年 | 999篇 |
2013年 | 1264篇 |
2012年 | 1033篇 |
2011年 | 1247篇 |
2010年 | 1111篇 |
2009年 | 1369篇 |
2008年 | 1341篇 |
2007年 | 1429篇 |
2006年 | 1278篇 |
2005年 | 1217篇 |
2004年 | 998篇 |
2003年 | 909篇 |
2002年 | 762篇 |
2001年 | 707篇 |
2000年 | 651篇 |
1999年 | 559篇 |
1998年 | 505篇 |
1997年 | 477篇 |
1996年 | 346篇 |
1995年 | 283篇 |
1994年 | 236篇 |
1993年 | 179篇 |
1992年 | 152篇 |
1991年 | 125篇 |
1990年 | 136篇 |
1989年 | 91篇 |
1988年 | 85篇 |
1987年 | 75篇 |
1986年 | 67篇 |
1985年 | 81篇 |
1984年 | 66篇 |
1983年 | 46篇 |
1982年 | 63篇 |
1981年 | 59篇 |
1980年 | 38篇 |
1979年 | 34篇 |
1978年 | 30篇 |
1977年 | 26篇 |
1976年 | 30篇 |
1973年 | 21篇 |
We define a new notion of ``HP-small' set which implies that is both -porous and Haar null in the sense of Christensen. We show that the set of all continuous functions on which have finite unilateral approximate derivative at a point is HP-small, as well as its projections onto hyperplanes. As a corollary, the same is true for the set of all Besicovitch functions. Also, the set of continuous functions on which are Hölder at a point is HP-small.
Some years ago, compactly supported divergence-free wavelets were constructed which also gave rise to a stable (biorthogonal) wavelet splitting of . These bases have successfully been used both in the analysis and numerical treatment of the Stokes and Navier-Stokes equations. In this paper, we construct stable wavelet bases for the stream function spaces . Moreover, -free vector wavelets are constructed and analysed. The relationship between and are expressed in terms of these wavelets. We obtain discrete (orthogonal) Hodge decompositions.
Our construction works independently of the space dimension, but in terms of general assumptions on the underlying wavelet systems in that are used as building blocks. We give concrete examples of such bases for tensor product and certain more general domains . As an application, we obtain wavelet multilevel preconditioners in and .
In this paper we prove uniqueness of positive solutions to logistic singular problems , , 1$">, 0$"> in , where the main feature is the fact that . More importantly, we provide exact asymptotic estimates describing, in the form of a two-term expansion, the blow-up rate for the solutions near . This expansion involves both the distance function and the mean curvature of .
Let be a smooth projective curve over a field . For each closed point of let be the coordinate ring of the affine curve obtained by removing from . Serre has proved that is isomorphic to the fundamental group, , of a graph of groups , where is a tree with at most one non-terminal vertex. Moreover the subgroups of attached to the terminal vertices of are in one-one correspondence with the elements of , the ideal class group of . This extends an earlier result of Nagao for the simplest case .
Serre's proof is based on applying the theory of groups acting on trees to the quotient graph , where is the associated Bruhat-Tits building. To determine he makes extensive use of the theory of vector bundles (of rank 2) over . In this paper we determine using a more elementary approach which involves substantially less algebraic geometry.
The subgroups attached to the edges of are determined (in part) by a set of positive integers , say. In this paper we prove that is bounded, even when Cl is infinite. This leads, for example, to new free product decomposition results for certain principal congruence subgroups of , involving unipotent and elementary matrices.