全文获取类型
收费全文 | 27144篇 |
免费 | 633篇 |
国内免费 | 695篇 |
专业分类
化学 | 5285篇 |
晶体学 | 951篇 |
力学 | 434篇 |
综合类 | 51篇 |
数学 | 17462篇 |
物理学 | 4289篇 |
出版年
2023年 | 74篇 |
2022年 | 213篇 |
2021年 | 177篇 |
2020年 | 198篇 |
2019年 | 543篇 |
2018年 | 584篇 |
2017年 | 381篇 |
2016年 | 387篇 |
2015年 | 423篇 |
2014年 | 784篇 |
2013年 | 1966篇 |
2012年 | 792篇 |
2011年 | 2038篇 |
2010年 | 1783篇 |
2009年 | 1735篇 |
2008年 | 1954篇 |
2007年 | 1948篇 |
2006年 | 1468篇 |
2005年 | 1159篇 |
2004年 | 1013篇 |
2003年 | 812篇 |
2002年 | 772篇 |
2001年 | 571篇 |
2000年 | 530篇 |
1999年 | 554篇 |
1998年 | 492篇 |
1997年 | 404篇 |
1996年 | 447篇 |
1995年 | 509篇 |
1994年 | 467篇 |
1993年 | 357篇 |
1992年 | 338篇 |
1991年 | 225篇 |
1990年 | 228篇 |
1989年 | 215篇 |
1988年 | 134篇 |
1987年 | 148篇 |
1986年 | 138篇 |
1985年 | 217篇 |
1984年 | 167篇 |
1983年 | 96篇 |
1982年 | 138篇 |
1981年 | 159篇 |
1980年 | 133篇 |
1979年 | 89篇 |
1978年 | 138篇 |
1977年 | 111篇 |
1976年 | 107篇 |
1975年 | 44篇 |
1974年 | 53篇 |
排序方式: 共有10000条查询结果,搜索用时 21 毫秒
141.
This article studies some geometrical aspects of the semidefinite linear complementarity problem (SDLCP), which can be viewed as a generalization of the well-known linear complementarity problem (LCP). SDLCP is a special case of a complementarity problem over a closed convex cone, where the cone considered is the closed convex cone of positive semidefinite matrices. It arises naturally in the unified formulation of a pair of primal-dual semidefinite programming problems. In this article, we introduce the notion of complementary cones in the semidefinite setting using the faces of the cone of positive semidefinite matrices and show that unlike complementary cones induced by an LCP, semidefinite complementary cones need not be closed. However, under R0-property of the linear transformation, closedness of all the semidefinite complementary cones induced by L is ensured. We also introduce the notion of a principal subtransformation with respect to a face of the cone of positive semidefinite matrices and show that for a self-adjoint linear transformation, strict copositivity is equivalent to strict semimonotonicity of each principal subtransformation. Besides the above, various other solution properties of SDLCP will be interpreted and studied geometrically. 相似文献
142.
D.P. Baturov 《Topology and its Applications》2007,154(2):374-383
Let M be a separable metric space consisting of more than one point. We construct perfectly normal dense subspaces Z⊂Mc2 and (under additional set-theoretic assumption) Y⊂Mc which are not collectionwise Hausdorff. 相似文献
143.
In the introduction of the Arithmetica Diophantus says that in order to solve arithmetical problems one has to “follow the way he (Diophantus) will show.” The present paper has a threefold objective. Firstly, the meaning of this sentence is discussed, the conclusion being that Diophantus had elaborated a program for handling various arithmetical problems. Secondly, it is claimed that what is analyzed in the introduction is definitions of several terms, the exhibition of their symbolism, the way one may operate with them, but, most significantly, the main stages of the program itself. And thirdly, it is argued that Diophantus' intention in the Arithmetica is to show the way the stages of his program should be practically applied in various arithmetical problems. 相似文献
144.
We define the Sheffer group of all Sheffer-type polynomials and prove the isomorphism between the Sheffer group and the Riordan group. An equivalence of the Riordan array pair and generalized Stirling number pair is also presented. Finally, we discuss a higher dimensional extension of Riordan array pairs. 相似文献
145.
In this article we investigate some integral functional inequalities of Bellman–Bihari type for piecewise-continuous functions with some fixed points of discontinuity. We also prove a new analogy and generalization of results which were obtained by Bellman and Bihari to integro-sum inequalities with delay and discontinuities that do not belong to Lipschitz’s type. 相似文献
146.
Hubert de Fraysseix 《Discrete Applied Mathematics》2007,155(9):1079-1095
Using a general resolution of barycentric systems we give a generalization of Tutte's theorem on convex drawing of planar graphs. We deduce a characterization of the edge coverings into pairwise non-crossing paths which are stretchable: such a system is stretchable if and only if each subsystem of at least two paths has at least three free vertices (vertices of the outer face of the induced subgraph which are internal to none of the paths of the subsystem). We also deduce that a contact system of pseudo-segments is stretchable if and only if it is extendible. 相似文献
147.
Sandip B. Bharate 《Tetrahedron letters》2006,47(39):7021-7024
The antimalarial robustadials A and B have been synthesized in two steps starting from commercially available phloroglucinol comprising a key biomimetic three-component reaction that involves in situ generation of an o-quinone methide via Knoevenagel condensation and subsequent Diels-Alder cycloaddition with (−)-β-pinene. 相似文献
148.
Christian Wolf 《Journal of statistical physics》2006,122(6):1111-1138
In this paper we introduce the notion of generalized physical and SRB measures. These measures naturally generalize classical
physical and SRB measures to measures which are supported on invariant sets that are not necessarily attractors. We then perform
a detailed case study of these measures for hyperbolic Hènon maps. For this class of systems we are able to develop a complete
theory about the existence, uniqueness, finiteness, and properties of these natural measures. Moreover, we derive a classification
for the existence of a measure of full dimension. We also consider general hyperbolic surface diffeomorphisms and discuss
possible extensions of, as well as the differences to, the results for Hènon maps. Finally, we study the regular dependence
of the dimension of the generalized physical/SRB measure on the diffeomorphism. For the proofs we apply various techniques
from smooth ergodic theory including the thermodynamic formalism.
2000
Mathematics Subject Classification. Primary: 37C45, 37D20, 37D35, Secondary: 37A35, 37E30 相似文献
149.
This article deals with Leibniz's reception of Descartes' “geometry.” Leibnizian mathematics was based on five fundamental notions: calculus, characteristic, art of invention, method, and freedom. On the basis of methodological considerations Leibniz criticized Descartes' restriction of geometry to objects that could be given in terms of algebraic (i.e., finite) equations: “Descartes's mind was the limit of science.” The failure of algebra to solve equations of higher degree led Leibniz to develop linear algebra, and the failure of algebra to deal with transcendental problems led him to conceive of a science of the infinite. Hence Leibniz reconstructed the mathematical corpus, created new (transcendental) notions, and redefined known notions (equality, exactness, construction), thus establishing “a veritable complement of algebra for the transcendentals”: infinite equations, i.e., infinite series, became inestimable tools of mathematical research. 相似文献
150.
In 1979, Papadimitriou and Yannakakis gave a polynomial time algorithm for the scheduling of jobs requiring unit completion times when the precedence constraints form an interval order. The authors solve here the corresponding problem, for preemptive scheduling (a job can be interrupted to work on more important tasks, and completed at a later time, subject to the usual scheduling constraints.) The m-machine preemptive scheduling problem is shown to have a polynomial algorithm, for both unit time and variable execution times as well, when the precedence constraints are given by an interval order. 相似文献