全文获取类型
收费全文 | 17465篇 |
免费 | 1235篇 |
国内免费 | 1044篇 |
专业分类
化学 | 658篇 |
晶体学 | 10篇 |
力学 | 2125篇 |
综合类 | 230篇 |
数学 | 15053篇 |
物理学 | 1668篇 |
出版年
2024年 | 37篇 |
2023年 | 170篇 |
2022年 | 229篇 |
2021年 | 260篇 |
2020年 | 413篇 |
2019年 | 428篇 |
2018年 | 478篇 |
2017年 | 492篇 |
2016年 | 485篇 |
2015年 | 346篇 |
2014年 | 719篇 |
2013年 | 1489篇 |
2012年 | 782篇 |
2011年 | 896篇 |
2010年 | 788篇 |
2009年 | 1100篇 |
2008年 | 1159篇 |
2007年 | 1190篇 |
2006年 | 1059篇 |
2005年 | 858篇 |
2004年 | 747篇 |
2003年 | 789篇 |
2002年 | 699篇 |
2001年 | 517篇 |
2000年 | 526篇 |
1999年 | 470篇 |
1998年 | 437篇 |
1997年 | 402篇 |
1996年 | 308篇 |
1995年 | 252篇 |
1994年 | 181篇 |
1993年 | 153篇 |
1992年 | 147篇 |
1991年 | 118篇 |
1990年 | 96篇 |
1989年 | 51篇 |
1988年 | 50篇 |
1987年 | 40篇 |
1986年 | 46篇 |
1985年 | 64篇 |
1984年 | 60篇 |
1983年 | 30篇 |
1982年 | 33篇 |
1981年 | 30篇 |
1980年 | 23篇 |
1979年 | 26篇 |
1978年 | 24篇 |
1977年 | 22篇 |
1976年 | 12篇 |
1974年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
An energy-dependent partitioning scheme is explored for extracting a small number of eigenvalues of a real symmetric matrix with the help of genetic algorithm. The proposed method is tested with matrices of different sizes (30 × 30 to 1000 × 1000). Comparison is made with Löwdin’s strategy for solving the problem. The relative advantages and disadvantages of the GA-based method are analyzed 相似文献
102.
V. S. Klimov 《Mathematical Notes》2007,81(1-2):61-71
We study homology characteristics of critical values and extremals of Lipschitz functionals defined on bounded closed convex subsets of a reflexive space that are invariant under deformations. Sufficient conditions for the existence of a bifurcation point of a multivalued potential operator (the switch principle for the typical number of an extremal) are established. 相似文献
103.
104.
We study a variation of the knapsack problem in which each item has a profit, a weight and a penalty; the sum of profits of the selected items minus the largest penalty associated with the selected items must be maximized. We present an ILP formulation and an exact optimization algorithm. 相似文献
105.
In the present paper, we consider the problem of the optimal reconstruction of the solution of the wave equation from the approximate values of the Fourier coefficients of the function specifying the initial form of the string. For an operator defined on the weight space of vectors from l 2, we present the solution of the more general problem of reconstruction from the approximate values of the coordinates of these vectors. 相似文献
106.
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
107.
A fully coupled formulation combining reactive transport and an existing thermo-hydro-mechanical (THM) code is presented.
Special attention has been given to phenomena likely to be encountered in clay barriers used as part of containment systems
of nuclear waste. The types of processes considered include hydrolysis, complex formation, oxidation/reduction reactions,
acid/base reactions, precipitation/dissolution of minerals and cation exchange. Both kinetically-controlled and equilibrium-controlled
reactions have been incorporated. The total analytical concentrations (including precipitated minerals) are adopted as basic
transport variables and chemical equilibrium is achieved by minimizing Gibbs Free Energy. The formulation has been incorporated
in a general purpose computer code capable of performing numerical analysis of engineering problems. A validation exercise
concerning a laboratory experiment involving the heating and hydration of an expansive compacted clay is described. 相似文献
108.
An inverse problem of the reconstruction of the right-hand side of the Euler-Darboux equation is studied. This problem is equivalent to the Volterra integral equation of the third kind with the operator of multiplication by a smooth nonincreasing function. Numerical solution of this problem is constructed using an integral representation of the solution of the inverse problem, the regularization method, and the method of quadratures. The convergence and stability of the numerical method is proved. 相似文献
109.
In this note, the authors resolve an evolutionary Wente's problem associated to heat equation, where the special integrability of det▽u for u ∈ H1(R2,R2) is used. 相似文献
110.
In this paper we derive a priori and a posteriori error estimates for cell centered finite volume approximations of nonlinear conservation laws on polygonal bounded domains. Numerical experiments show the applicability of the a posteriori result for the derivation of local adaptive solution strategies.