全文获取类型
收费全文 | 3250篇 |
免费 | 154篇 |
国内免费 | 108篇 |
专业分类
化学 | 163篇 |
晶体学 | 2篇 |
力学 | 116篇 |
综合类 | 23篇 |
数学 | 2949篇 |
物理学 | 259篇 |
出版年
2024年 | 11篇 |
2023年 | 52篇 |
2022年 | 58篇 |
2021年 | 79篇 |
2020年 | 66篇 |
2019年 | 79篇 |
2018年 | 69篇 |
2017年 | 58篇 |
2016年 | 58篇 |
2015年 | 62篇 |
2014年 | 164篇 |
2013年 | 267篇 |
2012年 | 135篇 |
2011年 | 188篇 |
2010年 | 195篇 |
2009年 | 269篇 |
2008年 | 242篇 |
2007年 | 239篇 |
2006年 | 146篇 |
2005年 | 137篇 |
2004年 | 116篇 |
2003年 | 103篇 |
2002年 | 105篇 |
2001年 | 76篇 |
2000年 | 67篇 |
1999年 | 66篇 |
1998年 | 75篇 |
1997年 | 50篇 |
1996年 | 46篇 |
1995年 | 35篇 |
1994年 | 44篇 |
1993年 | 28篇 |
1992年 | 17篇 |
1991年 | 22篇 |
1990年 | 14篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 9篇 |
1986年 | 10篇 |
1985年 | 10篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1982年 | 8篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
排序方式: 共有3512条查询结果,搜索用时 0 毫秒
101.
基于最优化方法求解约束非线性方程组的一个突出困难是计算 得到的仅是该优化问题的稳定点或局部极小点,而非方程组的解点.由此引出的问题是如何从一个稳定点出发得到一个相对于方程组解更好的点. 该文采用投影型算法,推广了Nazareth-Qi$^{[8,9]}$ 求解无约束非线性方程组的拉格朗日全局算法(Lagrangian Global-LG)于约束方程上; 理论上证明了从优化问题的稳定点出发,投影LG方法可寻找到一个更好的点. 数值试验证明了LG方法的有效性. 相似文献
102.
Global optimization problems involving the minimization of a product of convex functions on a convex set are addressed in
this paper. Elements of convex analysis are used to obtain a suitable representation of the convex multiplicative problem
in the outcome space, where its global solution is reduced to the solution of a sequence of quasiconcave minimizations on
polytopes. Computational experiments illustrate the performance of the global optimization algorithm proposed.
相似文献
103.
Nenad Mladenović Milan Dražić Vera Kovačevic-Vujčić Mirjana Čangalović 《European Journal of Operational Research》2008
We suggest a new heuristic for solving unconstrained continuous optimization problems. It is based on a generalized version of the variable neighborhood search metaheuristic. Different neighborhoods and distributions, induced from different metrics are ranked and used to get random points in the shaking step. We also propose VNS for solving constrained optimization problems. The constraints are handled using exterior point penalty functions within an algorithm that combines sequential and exact penalty transformations. The extensive computer analysis that includes the comparison with genetic algorithm and some other approaches on standard test functions are given. With our approach we obtain encouraging results. 相似文献
104.
Phan Van Tuoc 《Journal of Mathematical Analysis and Applications》2008,343(2):826-834
We consider a strongly coupled nonlinear parabolic system which arises in population dynamics in n-dimensional domains (n?1). We prove the global existence of classical solutions to the system for n<10. 相似文献
105.
通过构造李雅谱诺夫泛函,对具有时滞的二阶神经网络的稳定性进行分析,利用Eazumikhin定理得到了网络平衡点全局指数稳定的时滞相关与无关的充分条件,当衰减率依赖于时间时,得出了它们之间的一个线性关系,并进行了简明扼要的分析. 相似文献
106.
The problem of multidimensional scaling with city-block distances in the embedding space is reduced to a two level optimization
problem consisting of a combinatorial problem at the upper level and a quadratic programming problem at the lower level. A
hybrid method is proposed combining randomized search for the upper level problem with a standard quadratic programming algorithm
for the lower level problem. Several algorithms for the combinatorial problem have been tested and an evolutionary global
search algorithm has been proved most suitable. An experimental code of the proposed hybrid multidimensional scaling algorithm
is developed and tested using several test problems of two- and three-dimensional scaling. 相似文献
107.
本文利用 Liapunov 函数方法和论证系统正半轨线有界的 Shimanov区域方法,给出了两类非线性系统的零解为全局稳定的充分条件,并讨论了一些低阶实例,得到了较好的结果. 相似文献
108.
Xinzhu Meng Jianjun Jiao Lansun Chen 《Nonlinear Analysis: Theory, Methods & Applications》2008,68(12):3633-3645
A nonautonomous Lotka–Volterra dispersal system with continuous delays and discrete delays is considered. By using a comparison theorem and delay differential equation basic theory, we obtain sufficient conditions for the permanence of the population in every patch. By constructing a suitable Lyapunov functional, we prove that the system is globally asymptotically stable under some appropriate conditions. Using almost periodic functional hull theory, we get sufficient conditions for the existence, uniqueness and globally asymptotical stability for an almost periodic solution. This implies that the population in every patch exhibits stable almost periodic fluctuation. Furthermore, the results show that the permanence and global stability of system, and the existence and uniqueness of a positive almost periodic solution, depend on the delay; then we call it “profitless”. 相似文献
109.
In this paper, a new concept called α-inverse Lipschitz function is introduced. Based on the topological degree theory and Lyapunov functional method, we investigate global convergence for a novel class of neural networks with impulses where the neuron activations belong to the class of α-inverse Lipschitz functions. Some sufficient conditions are derived which ensure the existence, and global exponential stability of the equilibrium point of neural networks. Furthermore, we give two results which are used to check the stability of uncertain neural networks. Finally, two numerical examples are given to demonstrate the effectiveness of results obtained in this paper. 相似文献
110.
In this paper, we construct an augmented system of the standard monotone linear complementarity problem (LCP), and establish
the relations between the augmented system and the LCP. We present a smoothing-type algorithm for solving the augmented system.
The algorithm is shown to be globally convergent without assuming any prior knowledge of feasibility/infeasibility of the
problem. In particular, if the LCP has a solution, then the algorithm either generates a maximal complementary solution of
the LCP or detects correctly solvability of the LCP, and in the latter case, an existing smoothing-type algorithm can be directly
applied to solve the LCP without any additional assumption and it generates a maximal complementary solution of the LCP; and
that if the LCP is infeasible, then the algorithm detect correctly infeasibility of the LCP. To the best of our knowledge,
such properties have not appeared in the existing literature for smoothing-type algorithms.
This work was partially supported by the National Natural Science Foundation of China (Grant No. 10571134), the Natural Science
Foundation of Tianjin (Grant No. 07JCYBJC05200), and the Scientific Research Foundation for the Returned Overseas Chinese
Scholars, State Education Ministry. 相似文献