全文获取类型
收费全文 | 2822篇 |
免费 | 223篇 |
国内免费 | 214篇 |
专业分类
化学 | 467篇 |
晶体学 | 4篇 |
力学 | 76篇 |
综合类 | 34篇 |
数学 | 1994篇 |
物理学 | 684篇 |
出版年
2024年 | 8篇 |
2023年 | 29篇 |
2022年 | 57篇 |
2021年 | 73篇 |
2020年 | 67篇 |
2019年 | 63篇 |
2018年 | 67篇 |
2017年 | 72篇 |
2016年 | 82篇 |
2015年 | 51篇 |
2014年 | 106篇 |
2013年 | 178篇 |
2012年 | 113篇 |
2011年 | 141篇 |
2010年 | 117篇 |
2009年 | 180篇 |
2008年 | 203篇 |
2007年 | 198篇 |
2006年 | 181篇 |
2005年 | 180篇 |
2004年 | 137篇 |
2003年 | 122篇 |
2002年 | 117篇 |
2001年 | 86篇 |
2000年 | 92篇 |
1999年 | 89篇 |
1998年 | 59篇 |
1997年 | 63篇 |
1996年 | 48篇 |
1995年 | 35篇 |
1994年 | 37篇 |
1993年 | 18篇 |
1992年 | 19篇 |
1991年 | 16篇 |
1990年 | 10篇 |
1989年 | 11篇 |
1988年 | 18篇 |
1987年 | 18篇 |
1986年 | 14篇 |
1985年 | 10篇 |
1984年 | 14篇 |
1983年 | 8篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1974年 | 3篇 |
1973年 | 2篇 |
排序方式: 共有3259条查询结果,搜索用时 15 毫秒
91.
92.
Cell formation (CF) is the first and the most important problem in designing cellular manufacturing systems. Due to its non-polynomial nature, various heuristic and metaheuristic algorithms have been proposed to solve CF problem. Despite the popularity of heuristic algorithms, few studies have attempted to develop exact algorithms, such as branch and bound (B&B) algorithms, for this problem. We develop three types of branch and bound algorithms to deal with the cell formation problem. The first algorithm uses a binary branching scheme based on the definitions provided for the decision variables. Unlike the first algorithm, which relies on the mathematical model, the second one is designed based on the structure of the cell formation problem. The last algorithm has a similar structure to the second one, except that it has the ability to eliminate duplicated nodes in branching trees. The proposed branch and bound algorithms and a hybrid genetic algorithm are compared through some numerical examples. The results demonstrate the effectiveness of the modified problem-oriented branch and bound algorithm in solving relatively large size cell formation problems. 相似文献
93.
Di Xin ZHANG 《数学学报(英文版)》2006,22(2):339-346
So far the study of exponential bounds of an empirical process has been restricted to a bounded index class of functions. The case of an unbounded index class of functions is now studied on the basis of a new symmetrization idea and a new method of truncating the original probability space; the exponential bounds of the tail probabilities for the supremum of the empirical process over an unbounded class of functions are obtained. The exponential bounds can be used to establish laws of the logarithm for the empirical processes over unbounded classes of functions. 相似文献
94.
J. I. Abdullaev 《Theoretical and Mathematical Physics》2006,147(1):486-495
We consider the Hamiltonian of a system of two fermions on a one-dimensional integer lattice. We prove that the number of
bound states N(k) is a nondecreasing function of the total quasimomentum of the system k ∈ [0, π]. We describe the set of discontinuity points of N(k) and evaluate the jump N(k +0) − N(k) at the discontinuity points. We establish that the bound-state energy z
n
(k) increases as the total quasimomentum k ∈ [0, π] increases.
__________
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 147, No. 1, pp. 47–57, April, 2006. 相似文献
95.
We develop new algorithms for global optimization by combining well known branch and bound methods with multilevel subdivision
techniques for the computation of invariant sets of dynamical systems. The basic idea is to view iteration schemes for local
optimization problems – e.g. Newton’s method or conjugate gradient methods – as dynamical systems and to compute set coverings
of their fixed points. The combination with bounding techniques allow for the computation of coverings of the global optima
only. We show convergence of the new algorithms and present a particular implementation.
Michael Dellnitz - Research of the authors is partially supported by the Deutsche Forschungsgemeinschaft within the Sonderforschungsbereich
376 相似文献
96.
本文针对一类带有反凸约束的非线性比式和分式规划问题,提出一种求其全局最优解的单纯形分支和对偶定界算法.该算法利用Lagrange对偶理论将其中关键的定界问题转化为一系列易于求解的线性规划问题.收敛性分析和数值算例均表明提出的算法是可行的. 相似文献
97.
We introduce some ways to compute the lower and upper bounds of the Laplace eigenvalue problem.By using the special nonconforming finite elements,i.e.,enriched Crouzeix-Raviart element and extended Q1ro t,we get the lower bound of the eigenvalue.Additionally,we use conforming finite elements to do the postprocessing to get the upper bound of the eigenvalue,which only needs to solve the corresponding source problems and a small eigenvalue problem if higher order postprocessing method is implemented.Thus,we can obtain the lower and upper bounds of the eigenvalues simultaneously by solving eigenvalue problem only once.Some numerical results are also presented to demonstrate our theoretical analysis. 相似文献
98.
99.
本文对带有不定二次约束且目标函数为非凸二次函数的最优化问题提出了一类新的确定型全局优化算法,通过对目标函数和约束函数的线性下界估计,建立了原规划的松弛线性规划,通过对松弛线性规划可行域的细分以及一系列松弛线性规划的求解过程,得到原问题的全局最优解.我们从理论上证明了算法能收敛到原问题的全局最优解. 相似文献
100.