全文获取类型
收费全文 | 22801篇 |
免费 | 1033篇 |
国内免费 | 1280篇 |
专业分类
化学 | 9488篇 |
晶体学 | 200篇 |
力学 | 398篇 |
综合类 | 63篇 |
数学 | 11253篇 |
物理学 | 3712篇 |
出版年
2024年 | 35篇 |
2023年 | 365篇 |
2022年 | 266篇 |
2021年 | 288篇 |
2020年 | 442篇 |
2019年 | 554篇 |
2018年 | 485篇 |
2017年 | 392篇 |
2016年 | 468篇 |
2015年 | 552篇 |
2014年 | 782篇 |
2013年 | 1369篇 |
2012年 | 910篇 |
2011年 | 1622篇 |
2010年 | 1250篇 |
2009年 | 1615篇 |
2008年 | 1788篇 |
2007年 | 1576篇 |
2006年 | 1224篇 |
2005年 | 935篇 |
2004年 | 858篇 |
2003年 | 782篇 |
2002年 | 1066篇 |
2001年 | 539篇 |
2000年 | 501篇 |
1999年 | 539篇 |
1998年 | 408篇 |
1997年 | 333篇 |
1996年 | 399篇 |
1995年 | 372篇 |
1994年 | 330篇 |
1993年 | 256篇 |
1992年 | 229篇 |
1991年 | 180篇 |
1990年 | 151篇 |
1989年 | 166篇 |
1988年 | 110篇 |
1987年 | 114篇 |
1986年 | 99篇 |
1985年 | 130篇 |
1984年 | 106篇 |
1983年 | 63篇 |
1982年 | 98篇 |
1981年 | 96篇 |
1980年 | 49篇 |
1979年 | 36篇 |
1978年 | 32篇 |
1977年 | 43篇 |
1976年 | 32篇 |
1971年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Kunyu Guo 《Journal of Functional Analysis》2004,213(2):380-411
This paper mainly concerns defect operators and defect functions of Hardy submodules, Bergman submodules over the unit ball, and Hardy submodules over the polydisk. The defect operator (function) carries key information about operator theory (function theory) and structure of analytic submodules. The problem when a submodule has finite defect is attacked for both Hardy submodules and Bergman submodules. Our interest will be in submodules generated by polynomials. The reason for choosing such submodules is to understand the interaction of operator theory, function theory and algebraic geometry. 相似文献
42.
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
43.
The graph-theoretic operation of rooted subtree prune and regraft is increasingly being used as a tool for understanding and modelling reticulation events in evolutionary biology. In this paper, we show that computing the rooted subtree prune and regraft distance between two rooted binary phylogenetic trees on the same label set is NP-hard. This resolves a longstanding open problem. Furthermore, we show that this distance is fixed parameter tractable when parameterised by the distance between the two trees.Received March 16, 2004 相似文献
44.
45.
46.
Franz-Viktor Kuhlmann 《Advances in Mathematics》2004,188(2):399-424
We consider the Zariski space of all places of an algebraic function field F|K of arbitrary characteristic and investigate its structure by means of its patch topology. We show that certain sets of places with nice properties (e.g., prime divisors, places of maximal rank, zero-dimensional discrete places) lie dense in this topology. Further, we give several equivalent characterizations of fields that are large, in the sense of F. Pop's Annals paper Embedding problems over large fields. We also study the question whether a field K is existentially closed in an extension field L if L admits a K-rational place. In the appendix, we prove the fact that the Zariski space with the Zariski topology is quasi-compact and that it is a spectral space. 相似文献
47.
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
48.
In this paper we relate the operators in the operator representations of a generalized Nevanlinna function N(z) and of the function −N(z)−1 under the assumption that z=∞ is the only (generalized) pole of nonpositive type. The results are applied to the Q-function for S and H and the Q-function for S and H∞, where H is a self-adjoint operator in a Pontryagin space with a cyclic element w, H∞ is the self-adjoint relation obtained from H and w via a rank one perturbation at infinite coupling, and S is the symmetric operator given by S=H∩H∞. 相似文献
49.
富勒烯 (C60 /C70 )与N ,N ,N′ ,N′ 四 (对甲苯基 ) 4,4′ 二胺 1,1′ 二苯硒醚 (TPDASe)间在激光光诱导条件下 ,发生了分子间的电子转移过程 .在可见 -近红外区 ( 60 0~ 12 0 0nm) ,观测到了TPDASe阳离子自由基、富勒烯 (C60 /C70 )激发三线态和阴离子自由基 ,在苯腈溶液中 ,观测瞬态谱测定了电子从TPDASe转移到富勒烯 (C60 /C70 )激发三线态的量子转化产率(ΦTet)和电子转移常数 (Ket) . 相似文献
50.
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