全文获取类型
收费全文 | 24161篇 |
免费 | 2652篇 |
国内免费 | 1167篇 |
专业分类
化学 | 6147篇 |
晶体学 | 44篇 |
力学 | 1695篇 |
综合类 | 235篇 |
数学 | 12794篇 |
物理学 | 7065篇 |
出版年
2024年 | 36篇 |
2023年 | 206篇 |
2022年 | 339篇 |
2021年 | 515篇 |
2020年 | 571篇 |
2019年 | 599篇 |
2018年 | 468篇 |
2017年 | 585篇 |
2016年 | 860篇 |
2015年 | 658篇 |
2014年 | 1102篇 |
2013年 | 1848篇 |
2012年 | 1155篇 |
2011年 | 1165篇 |
2010年 | 1077篇 |
2009年 | 1402篇 |
2008年 | 1617篇 |
2007年 | 1637篇 |
2006年 | 1414篇 |
2005年 | 1136篇 |
2004年 | 983篇 |
2003年 | 956篇 |
2002年 | 982篇 |
2001年 | 826篇 |
2000年 | 786篇 |
1999年 | 730篇 |
1998年 | 634篇 |
1997年 | 488篇 |
1996年 | 403篇 |
1995年 | 343篇 |
1994年 | 306篇 |
1993年 | 262篇 |
1992年 | 256篇 |
1991年 | 184篇 |
1990年 | 147篇 |
1989年 | 144篇 |
1988年 | 145篇 |
1987年 | 114篇 |
1986年 | 109篇 |
1985年 | 154篇 |
1984年 | 127篇 |
1983年 | 39篇 |
1982年 | 83篇 |
1981年 | 68篇 |
1980年 | 70篇 |
1979年 | 63篇 |
1978年 | 43篇 |
1977年 | 48篇 |
1976年 | 35篇 |
1973年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
141.
利用已知弹性函数级联上高非线性度多输出布尔函数的方法构造(n,m,t)弹性函数,其非线性度为2^n-1-2^n-l/2-1+2^l/2.nlmax(n-l,m,t),在相同条件下改进了Kurosawa的非线性度2^n-1-2^n-l/2-1.特别地,本文构造了两类具体的向量弹性函数,得到两个不同的非线性度.本文所得函数的非线性度在大多数情况下是比较好的. 相似文献
142.
R. Thomas conjectured, 20 years ago, that the presence of a positive circuit in the interaction graph of a dynamical system is a necessary condition for the presence of several stable states. Recently, E. Remy et al. stated and proved the conjecture for Boolean dynamical systems. Using a similar approach, we generalize the result to discrete dynamical systems, and by focusing on the asynchronous dynamics that R. Thomas used in the course of his analysis of genetic networks, we obtain a more general variant of R. Thomas’ conjecture. In this way, we get a necessary condition for genetic networks to lead to differentiation. 相似文献
143.
144.
Hadi Mohammadi Bidhandi 《Annals of Operations Research》2006,143(1):237-250
This paper develops a mathematical model for project time compression problems in CPM/PERT type networks. It is noted this
formulation of the problem will be an adequate approximation for solving the time compression problem with any continuous
and non-increasing time-cost curve. The kind of this model is Mixed Integer Linear Program (MILP) with zero-one variables,
and the Benders' decomposition procedure for analyzing this model has been developed. Then this paper proposes a new approach
based on the surrogating method for solving these problems. In addition, the required computer programs have been prepared
by the author to execute the algorithm. An illustrative example solved by the new algorithm, and two methods are compared
by several numerical examples. Computational experience with these data shows the superiority of the new approach. 相似文献
145.
The objective of this paper is to analyze under what well-known operations the class of quasipolyhedral convex functions,
which can be regarded as an extension of that of polyhedral convex functions, is closed. The operations that will be considered
are those that preserve polyhedral convexity, such that the image and the inverse image under linear transformations, right
scalar multiplication (including the case where λ=0+) and pointwise addition.
相似文献
146.
A. A. Maleev 《Computational Mathematics and Mathematical Physics》2006,46(12):2031-2039
Stationary and nonstationary Jacobi-like iterative processes for solving systems of linear algebraic equations are examined. For a system whose coefficient matrix A is an H-matrix, it is shown that the convergence rate of any Jacobi-like process is at least as high as that of the point Jacobi method as applied to a system with 〈A〉 as the coefficient matrix, where 〈A〉 is a comparison matrix of A. 相似文献
147.
148.
A direct central collision of two identical bodies of revolution is studied. A nonstationary mixed boundary-value problem with an unknown moving boundary is formulated. Its solution is represented by a series in term of Bessel functions. An infinite system of Volterra equations of the second kind for the unknown expansion coefficients is derived by satisfying the boundary conditions. The basic characteristics of the collision process are determined depending on the curvature of the frontal surface of the bodies 相似文献
149.
The motion of a particle in the field of an electromagnetic monopole (in the Coulomb–Dirac field) perturbed by an axially symmetric potential after quantum averaging is described by an integrable system. Its Hamiltonian can be written in terms of the generators of an algebra with quadratic commutation relations. We construct the irreducible representations of this algebra in terms of second-order differential operators; we also construct its hypergeometric coherent states. We use these states in the first-order approximation with respect to the perturbing field to obtain the integral representation of the eigenfunctions of the original problem in terms of solutions of the model Heun-type second-order ordinary differential equation and present the asymptotic approximation of the corresponding eigenvalues. 相似文献
150.
Jiang Wei 《Journal of Mathematical Analysis and Applications》2004,297(1):305-316
The eigenvalue and the stability of singular differential systems with delay are considered. Firstly we investigate some properties of the eigenvalue, then give the exact exponential estimation for the fundamental solution, and finally discuss the necessary and sufficient condition of uniform asymptotic stability. 相似文献