全文获取类型
收费全文 | 11547篇 |
免费 | 256篇 |
国内免费 | 278篇 |
专业分类
化学 | 1447篇 |
晶体学 | 32篇 |
力学 | 77篇 |
综合类 | 17篇 |
数学 | 9713篇 |
物理学 | 795篇 |
出版年
2023年 | 19篇 |
2022年 | 47篇 |
2021年 | 27篇 |
2020年 | 44篇 |
2019年 | 247篇 |
2018年 | 281篇 |
2017年 | 151篇 |
2016年 | 101篇 |
2015年 | 122篇 |
2014年 | 290篇 |
2013年 | 718篇 |
2012年 | 350篇 |
2011年 | 671篇 |
2010年 | 606篇 |
2009年 | 901篇 |
2008年 | 870篇 |
2007年 | 874篇 |
2006年 | 663篇 |
2005年 | 430篇 |
2004年 | 382篇 |
2003年 | 299篇 |
2002年 | 235篇 |
2001年 | 218篇 |
2000年 | 232篇 |
1999年 | 256篇 |
1998年 | 255篇 |
1997年 | 179篇 |
1996年 | 244篇 |
1995年 | 251篇 |
1994年 | 251篇 |
1993年 | 193篇 |
1992年 | 171篇 |
1991年 | 125篇 |
1990年 | 142篇 |
1989年 | 142篇 |
1988年 | 91篇 |
1987年 | 95篇 |
1986年 | 105篇 |
1985年 | 139篇 |
1984年 | 110篇 |
1983年 | 57篇 |
1982年 | 94篇 |
1981年 | 67篇 |
1980年 | 78篇 |
1979年 | 58篇 |
1978年 | 60篇 |
1977年 | 39篇 |
1976年 | 33篇 |
1975年 | 24篇 |
1973年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
Martin Skutella 《Mathematical Programming》2002,91(3):493-514
In the single source unsplittable min-cost flow problem, commodities must be routed simultaneously from a common source vertex
to certain destination vertices in a given graph with edge capacities and costs; the demand of each commodity must be routed
along a single path so that the total flow through any edge is at most its capacity. Moreover, the total cost must not exceed
a given budget. This problem has been introduced by Kleinberg [7] and generalizes several NP-complete problems from various
areas in combinatorial optimization such as packing, partitioning, scheduling, load balancing, and virtual-circuit routing.
Kolliopoulos and Stein [9] and Dinitz, Garg, and Goemans [4] developed algorithms improving the first approximation results
of Kleinberg for the problem of minimizing the violation of edge capacities and for other variants. However, known techniques
do not seem to be capable of providing solutions without also violating the cost constraint. We give the first approximation
results with hard cost constraints. Moreover, all our results dominate the best known bicriteria approximations. Finally,
we provide results on the hardness of approximation for several variants of the problem.
Received: August 23, 2000 / Accepted: April 20, 2001?Published online October 2, 2001 相似文献
92.
Summary The optimality question for blockp-cyclic SOR iterations discussed in Young and Varga is answered under natural conditions on the spectrum of the block Jacobi matrix. In particular, it is shown that repartitioning a blockp-cyclic matrix into a blockq-cyclic form,q
, results in asymptotically faster SOR convergence for the same amount of work per iteration. As a consequence block 2-cyclic SOR is optimal under these conditions.Research supported in part by the US Air Force under Grant no. AFOSR-88-0285 and the National Science Foundation under grant no. DMS-85-21154 Present address: Boeing Computer Services, P.O. Box 24346, MS 7L-21, Seattle, WA 98124-0346, USA 相似文献
93.
Piotr Niemiec 《Topology and its Applications》2006,153(18):3373-3382
Equicontinuous semigroups of transformations of a compact Hausdorff space and their sets of all invariant (Borel, regular and probabilistic) measures are studied. Conditions equivalent to the existence of at least one invariant measure are given. The (algebraic and topological) structure of the set of invariant measures is researched. 相似文献
94.
Shigeru Yamagami 《Journal of Pure and Applied Algebra》2002,167(1):83-128
A duality for orbifolds is presented as an application of group extensions in tensor categories. 相似文献
95.
Diem Ho 《Numerische Mathematik》1989,56(7):721-734
Summary The acceleration by Tchebychev iteration for solving nonsymmetric eigenvalue problems is dicussed. A simple algorithm is derived to obtain the optimal ellipse which passes through two eigenvalues in a complex plane relative to a reference complex eigenvalue. New criteria are established to identify the optimal ellipse of the eigenspectrum. The algorithm is fast, reliable and does not require a search for all possible ellipses which enclose the spectrum. The procedure is applicable to nonsymmetric linear systems as well. 相似文献
96.
In this paper, we establish some new nonlinear integral inequalities of the Gronwall–Bellman–Ou-Iang-type in two variables. These on the one hand generalizes and on the other hand furnish a handy tool for the study of qualitative as well as quantitative properties of solutions of differential equations. We illustrate this by applying our new results to certain boundary value problem. 相似文献
97.
We prove that a for a mapping f of finite distortion , the -Hausdorff measure of any point preimage is zero provided is integrable, with , and the multiplicity function of f is essentially bounded. As a consequence for we obtain that the mapping is then open and discrete.
Received: 18 June 2001 / Revised version: 31 January 2002 / Published online: 27 June 2002 相似文献
98.
Weak vector equilibrium problems with bi-variable mappings from product space of two bounded complete locally convex Hausdorff topological vector spaces to another topological vector space are studied. The existence theorems of solutions are proved by the FKKM fixed point theorem. Viscosity principle of vector equilibrium problems is dealt with. The relations between solutions of the vector equilibrium problem and those of its perturbation problem are presented. 相似文献
99.
Global Existence and Exponential Stability of Smooth Solutions to a Full Hydrodynamic Model to Semiconductors 总被引:1,自引:0,他引:1
We study a full hydrodynamic semiconductor model in multi-space dimension. The global existence of smooth solutions is established
and the exponential stability of the solutions as is investigated.
Received November 14, 2000; in revised form March 25, 2002 Published online August 5, 2002 相似文献
100.
Common fixed-point results are established for a new class of noncommuting selfmaps. We apply them to obtain several invariant approximation results which unify, extend, and complement well-known results. 相似文献