全文获取类型
收费全文 | 9935篇 |
免费 | 243篇 |
国内免费 | 57篇 |
专业分类
化学 | 229篇 |
晶体学 | 6篇 |
力学 | 158篇 |
综合类 | 5篇 |
数学 | 9435篇 |
物理学 | 402篇 |
出版年
2023年 | 7篇 |
2022年 | 15篇 |
2021年 | 8篇 |
2020年 | 23篇 |
2019年 | 314篇 |
2018年 | 391篇 |
2017年 | 178篇 |
2016年 | 109篇 |
2015年 | 124篇 |
2014年 | 351篇 |
2013年 | 576篇 |
2012年 | 340篇 |
2011年 | 617篇 |
2010年 | 560篇 |
2009年 | 777篇 |
2008年 | 814篇 |
2007年 | 786篇 |
2006年 | 607篇 |
2005年 | 361篇 |
2004年 | 340篇 |
2003年 | 299篇 |
2002年 | 201篇 |
2001年 | 204篇 |
2000年 | 184篇 |
1999年 | 209篇 |
1998年 | 195篇 |
1997年 | 156篇 |
1996年 | 213篇 |
1995年 | 224篇 |
1994年 | 209篇 |
1993年 | 145篇 |
1992年 | 100篇 |
1991年 | 63篇 |
1990年 | 46篇 |
1989年 | 60篇 |
1988年 | 35篇 |
1987年 | 30篇 |
1986年 | 35篇 |
1985年 | 49篇 |
1984年 | 43篇 |
1983年 | 34篇 |
1982年 | 57篇 |
1981年 | 39篇 |
1980年 | 25篇 |
1979年 | 12篇 |
1978年 | 18篇 |
1977年 | 17篇 |
1976年 | 21篇 |
1974年 | 5篇 |
1973年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 40 毫秒
11.
Yevhen Zelenyuk 《Topology and its Applications》2006,153(14):2382-2385
We introduce the notion of a partially selective ultrafilter and prove that (a) if G is an extremally disconnected topological group and p is a converging nonprincipal ultrafilter on G containing a countable discrete subset, then p is partially selective, and (b) the existence of a nonprincipal partially selective ultrafilter on a countable set implies the existence of a P-point in ω∗. Thus it is consistent with ZFC that there is no extremally disconnected topological group containing a countable discrete nonclosed subset. 相似文献
12.
Michel Hébert 《Archive for Mathematical Logic》1991,31(2):133-143
Summary We give a syntactic characterization of (finitary) theories whose categories of models are closed under the formation of connected limits (respectively the formation of pullbacks and substructures) in the category of all structures. They are also those theories whose consistent extensions by new atomic facts admit in each component an initial structure (respectively an initial term structure), and also thoseT for whichM(T) is locally finitely multi-presentable in a canonical way. We also show that these two properties of theories are nonuniform. 相似文献
13.
Sauer, Shelah, Vapnik and Chervonenkis proved that if a set system on n vertices contains many sets, then the set system has full trace on a large set. Although the restriction on the size of the
groundset cannot be lifted, Frankl and Pach found a trace structure that is guaranteed to occur in uniform set systems even
if we do not bound the size of the groundset. In this note we shall give three sequences of structures such that every set
system consisting of sufficiently many sets contains at least one of these structures with many sets. 相似文献
14.
Satyanad Kichenassamy 《Advances in Mathematics》2004,184(2):268-288
In 1985, Fefferman and Graham have constructed a local embedding of an arbitrary real-analytic manifold, of odd dimension n, into a Ricci-flat manifold of dimension n+2 admitting a homothety. They conjectured that their result remains valid in even dimensions, if logarithms are allowed in the expansion of the metric. In this paper, we (i) prove that such expansions exist and converge and (ii) establish the degree of non-uniqueness of the solution in terms of the coefficients in the expansion. 相似文献
15.
We investigate heteroclinic orbits between equilibria and rotating waves for scalar semilinear parabolic reaction-advection-diffusion equations with periodic boundary conditions. Using zero number properties of the solutions and the phase shift equivariance of the equation, we establish a necessary and sufficient condition for the existence of a heteroclinic connection between any pair of hyperbolic equilibria or rotating waves. 相似文献
16.
Dmitri I. Panyushev 《Advances in Mathematics》2004,186(2):307-316
We study Abelian ideals of a Borel subalgebra consisting of long roots. It is shown that methods of Cellini and Papi can be extended to this situation. A uniform expression for the number of long Abelian ideals is given. We also show that there is a one-to-one correspondence between the long Abelian ideals and B-stable commutative subalgebras in the little adjoint representation of the Langlands dual Lie algebra. 相似文献
17.
Paulo D. Cordaro 《Advances in Mathematics》2004,184(1):89-118
Taking as a start point the recent article of Meziani [7], we present several results concerning the normalization of a class of complex vector fields in the plane which degenerate along a real curve. We mainly deal with operators with finite regularity and analyze both the local situation as well as the case of normalization near a circle. Some related questions (e.g., on semi-global solvability and on the normalization of a class of generalized Mizohata operators) are also discussed. 相似文献
18.
The formation of thinning filaments is commonly observed previously to the break-up of a very viscous jet. This paper shows that a fluid under capillary forces cannot break-up through the uniform collapse of a filament. 相似文献
19.
The existence of an attractor for a 2D-Navier-Stokes system with delay is proved. The theory of pullback attractors is successfully applied to obtain the results since the abstract functional framework considered turns out to be nonautonomous. However, on some occasions, the attractors may attract not only in the pullback sense but in the forward one as well. Also, this formulation allows to treat, in a unified way, terms containing various classes of delay features (constant, variable, distributed delays, etc.). As a consequence, some results for the autonomous model are deduced as particular cases of our general formulation. 相似文献
20.
In this paper, the detailed asymptotic behaviour of the solutions of a kinetic equation for quantum particles is studied. It is shown that this behaviour is sensitive not only to the total mass of the initial data but also to its precise behaviour near the origin. In some cases, solutions develop a Dirac mass at the origin for long times in a self-similar manner that is analysed in detail. 相似文献