全文获取类型
收费全文 | 3556篇 |
免费 | 172篇 |
国内免费 | 286篇 |
专业分类
化学 | 61篇 |
力学 | 199篇 |
综合类 | 38篇 |
数学 | 3317篇 |
物理学 | 399篇 |
出版年
2024年 | 4篇 |
2023年 | 40篇 |
2022年 | 36篇 |
2021年 | 49篇 |
2020年 | 108篇 |
2019年 | 91篇 |
2018年 | 82篇 |
2017年 | 94篇 |
2016年 | 108篇 |
2015年 | 76篇 |
2014年 | 142篇 |
2013年 | 307篇 |
2012年 | 121篇 |
2011年 | 189篇 |
2010年 | 170篇 |
2009年 | 228篇 |
2008年 | 258篇 |
2007年 | 239篇 |
2006年 | 190篇 |
2005年 | 183篇 |
2004年 | 136篇 |
2003年 | 161篇 |
2002年 | 135篇 |
2001年 | 118篇 |
2000年 | 120篇 |
1999年 | 114篇 |
1998年 | 89篇 |
1997年 | 94篇 |
1996年 | 66篇 |
1995年 | 34篇 |
1994年 | 32篇 |
1993年 | 21篇 |
1992年 | 12篇 |
1991年 | 14篇 |
1990年 | 16篇 |
1989年 | 16篇 |
1988年 | 7篇 |
1987年 | 15篇 |
1986年 | 6篇 |
1985年 | 21篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 10篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1978年 | 11篇 |
1977年 | 6篇 |
1976年 | 3篇 |
1975年 | 3篇 |
排序方式: 共有4014条查询结果,搜索用时 46 毫秒
71.
Bidyut Guha Thakurta 《Proceedings Mathematical Sciences》1986,95(1):53-59
In this paper, Weisner’s group-theoretic method of obtaining generating functions is utilized in the study of Jacobi polynomialsP> n (a,ß)(x) by giving suitable interpretations to the index (n) and the parameter (β) to find out the elements for constructing a six-dimensional Lie algebra. 相似文献
72.
Multiple zigzag chains of length n and width m constitute an important class of regular graphene flakes of rectangular shape. The physical and chemical properties of these basic pericondensed benzenoids can be related to their various topological invariants, conveniently encoded as the coefficients of a combinatorial polynomial, usually referred to as the ZZ polynomial of multiple zigzag chains . The current study reports a novel method for determination of these ZZ polynomials based on a hypothesized extension to John–Sachs theorem, used previously to enumerate Kekulé structures of various benzenoid hydrocarbons. We show that the ZZ polynomial of the multiple zigzag chain can be conveniently expressed as a determinant of a Toeplitz (or almost Toeplitz) matrix of size consisting of simple hypergeometric polynomials. The presented analysis can be extended to generalized multiple zigzag chains , i.e., derivatives of with a single attached polyacene chain of length k. All presented formulas are accompanied by formal proofs. The developed theoretical machinery is applied for predicting aromaticity distribution patterns in large and infinite multiple zigzag chains and for computing the distribution of spin densities in biradical states of finite multiple zigzag chains . 相似文献
73.
基于Lagrange原理和假设模态法建立了旋转输液管的动力学模型.通过降阶升维的方法求解系统的特征值问题,并分析了旋转输液管自由振动特性.得到了不同端部集中质量和转速下,系统特征值随流速升高的演变轨迹.揭示了临界流速随系统参数的变化规律.研究发现,内部流体的流动对旋转输液管动力学特性存在显著影响.在某些参数组合下,系统低阶模态能够形成不同形式的内共振关系.预示了旋转输液管模型蕴含丰富的动力学现象. 相似文献
74.
An augmented Lagrange algorithm for nonlinear optimizations with second-order cone constraints is proposed based on a Löwner operator associated with a potential function for the optimization problems with inequality constraints. The favorable properties of both the Löwner operator and the corresponding augmented Lagrangian are discussed. And under some mild assumptions, the rate of convergence of the augmented Lagrange algorithm is studied in detail. 相似文献
75.
Recently, we introduced a class of generalized hypergeometric functionsI
n:(b
q)/α:(a
p) (x, w) by using a difference operator Δ
x,w
, where
. In this paper an attempt has been made to obtain some bilateral generating relations associated withI
n
ga
(x, w). Each result is followed by its applications to the classical orthogonal polynomials. 相似文献
76.
Anthony J. D'Aristotile 《Journal of Theoretical Probability》1995,8(2):321-346
LetX be the collection ofk-dimensional subspaces of ann-dimensional vector spaceV
n overGF(q). A metric may be defined onX by letting
相似文献
77.
Holger Dette 《Transactions of the American Mathematical Society》1996,348(2):691-711
A new characterization of the generalized Hermite polyno-
mials and of the orthogonal polynomials with respect to the measure is derived which is based on a ``reversing property" of the coefficients in the corresponding recurrence formulas and does not use the representation in terms of Laguerre and Jacobi polynomials. A similar characterization can be obtained for a generalization of the sieved ultraspherical polynomials of the first and second kind. These results are applied in order to determine the asymptotic limit distribution for the zeros when the degree and the parameters tend to infinity with the same order. 78.
79.
André Draux 《Numerical Algorithms》1996,11(1):143-158
From some results concerning the formal orthogonal polynomials, already proved in [5], we develop new properties of generalized adjacent polynomials which correspond to a change in the weight function. A new structure of the singular blocks is given. These results have a direct application to Lanczos methods, theG and -algorithms. 相似文献
80.
The Modified Barrier Functions (MBF) have elements of both Classical Lagrangians (CL) and Classical Barrier Functions (CBF). The MBF methods find an unconstrained minimizer of some smooth barrier function in primal space and then update the Lagrange multipliers, while the barrier parameter either remains fixed or can be updated at each step. The numerical realization of the MBF method leads to the Newton MBF method, where the primal minimizer is found by using Newton's method. This minimizer is then used to update the Lagrange multipliers. In this paper, we examine the Newton MBF method for the Quadratic Programming (QP) problem. It will be shown that under standard second-order optimality conditions, there is a ball around the primal solution and a cut cone in the dual space such that for a set of Lagrange multipliers in this cut cone, the method converges quadratically to the primal minimizer from any point in the aforementioned ball, and continues, to do so after each Lagrange multiplier update. The Lagrange multipliers remain within the cut cone and converge linearly to their optimal values. Any point in this ball will be called a hot start. Starting at such a hot start, at mostO(In In
-1) Newton steps are sufficient to perform the primal minimization which is necessary for the Lagrange multiplier update. Here, >0 is the desired accuracy. Because of the linear convergence of the Lagrange multipliers, this means that onlyO(In
-1)O(In In
-1) Newton steps are required to reach an -approximation to the solution from any hot start. In order to reach the hot start, one has to perform
Newton steps, wherem characterizes the size of the problem andC>0 is the condition number of the QP problem. This condition number will be characterized explicitly in terms of key parameters of the QP problem, which in turn depend on the input data and the size of the problem.Partially supported by NASA Grant NAG3-1397 and National Science Foundation Grant DMS-9403218. 相似文献
|