全文获取类型
收费全文 | 9304篇 |
免费 | 895篇 |
国内免费 | 750篇 |
专业分类
化学 | 424篇 |
晶体学 | 5篇 |
力学 | 548篇 |
综合类 | 228篇 |
数学 | 9169篇 |
物理学 | 575篇 |
出版年
2024年 | 14篇 |
2023年 | 91篇 |
2022年 | 76篇 |
2021年 | 158篇 |
2020年 | 234篇 |
2019年 | 252篇 |
2018年 | 258篇 |
2017年 | 326篇 |
2016年 | 315篇 |
2015年 | 207篇 |
2014年 | 367篇 |
2013年 | 767篇 |
2012年 | 405篇 |
2011年 | 490篇 |
2010年 | 396篇 |
2009年 | 520篇 |
2008年 | 513篇 |
2007年 | 599篇 |
2006年 | 527篇 |
2005年 | 466篇 |
2004年 | 374篇 |
2003年 | 389篇 |
2002年 | 413篇 |
2001年 | 379篇 |
2000年 | 352篇 |
1999年 | 303篇 |
1998年 | 271篇 |
1997年 | 260篇 |
1996年 | 187篇 |
1995年 | 156篇 |
1994年 | 133篇 |
1993年 | 97篇 |
1992年 | 85篇 |
1991年 | 75篇 |
1990年 | 68篇 |
1989年 | 36篇 |
1988年 | 35篇 |
1987年 | 33篇 |
1986年 | 26篇 |
1985年 | 38篇 |
1984年 | 40篇 |
1983年 | 20篇 |
1982年 | 36篇 |
1981年 | 28篇 |
1980年 | 31篇 |
1979年 | 26篇 |
1978年 | 23篇 |
1977年 | 21篇 |
1976年 | 12篇 |
1973年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
82.
The theory of monotone semiflows has been widely applied to functional differential equations (FDEs). The studies on the theory and applications of monotone semiflows for FDEs are very important and interesting. A brief des-cription of our recent works are as follows.By using general monotone semiflow theory, several results of positively invariant sets, monotone solutions and contracting rectangles of retarded functional differential equations(RFDEs) with infinite delay are gained under the assumption of quasimonotonicity; sufficient conditions for the existence, un-iqueness and global attractivity of periodic solutions are also established by combining the theory of monotone semiflows for neutral functional differential equations(NFDEs) and Krasnoselskii's fixed point theorem. 相似文献
83.
This paper develops a theory for the global solution of nonconvex optimization problems with parameter-embedded linear dynamic systems. A quite general problem formulation is introduced and a solution is shown to exists. A convexity theory for integrals is then developed to construct convex relaxations for utilization in a branch-and-bound framework to calculate a global minimum. Interval analysis is employed to generate bounds on the state variables implied by the bounds on the embedded parameters. These bounds, along with basic integration theory, are used to prove convergence of the branch-and-bound algorithm to the global minimum of the optimization problem. The implementation of the algorithm is then considered and several numerical case studies are examined thoroughly 相似文献
84.
This paper presents a new generic Evolutionary Algorithm (EA) for retarding the unwanted effects of premature convergence. This is accomplished by a combination of interacting generic methods. These generalizations of a Genetic Algorithm (GA) are inspired by population genetics and take advantage of the interactions between genetic drift and migration. In this regard a new selection scheme is introduced, which is designed to directedly control genetic drift within the population by advantageous self-adaptive selection pressure steering. Additionally this new selection model enables a quite intuitive heuristics to detect premature convergence. Based upon this newly postulated basic principle the new selection mechanism is combined with the already proposed Segregative Genetic Algorithm (SEGA), an advanced Genetic Algorithm (GA) that introduces parallelism mainly to improve global solution quality. As a whole, a new generic evolutionary algorithm (SASEGASA) is introduced. The performance of the algorithm is evaluated on a set of characteristic benchmark problems. Computational results show that the new method is capable of producing highest quality solutions without any problem-specific additions. 相似文献
85.
Using the iterative scheme we prove the local existence and uniqueness of solutions of the spherically symmetric Einstein-Vlasov-Maxwell system with small initial data. We prove a continuation criterion to global in-time solutions. 相似文献
86.
具有种内互惠作用的Lotka-Volterra互惠共存模型 总被引:1,自引:0,他引:1
对具有种内互惠作用的Lotka-Volterra互惠共存模型进行了完整的全局分析,得到了一些新的结果。 相似文献
87.
设{Xni:1≤i≤n,n≥1}为行间独立的B值r.v.阵列,g(z)是指数为1/p的正则变化函数,r>0,{ani 1≤t≤n,n≥1}为实数阵列,本文得到了使(?)成立的条件,推广并改进了Stout及Sung等的著名结论. 相似文献
88.
L.G. Casado I. García T. Csendes V.G. Ruíz 《Journal of Optimization Theory and Applications》2003,118(1):27-43
Based on the investigation carried out in Ref. 1, this paper incorporates new studies about the properties of inclusion functions on subintervals while a branch-and-bound algorithm is solving global optimization problems. It is found that the relative place of the global minimum value within the inclusion function value of the objective function at the current interval indicates mostly whether the given interval is close to a minimizer point. This information is used in a heuristic interval rejection rule that can save a considerable amount of computation. Illustrative examples are discussed and an extended numerical study shows the advantages of the new approach. 相似文献
89.
Arnold Neumaier 《Journal of Global Optimization》2003,25(2):175-181
A family of multivariate rational functions is constructed. It has strong local minimizers with prescribed function values at prescribed positions. While there might be additional local minima, such minima cannot be global. A second family of multivariate rational functions is given, having prescribed global minimizers and prescribed interpolating data. 相似文献
90.
加速牛顿迭代收敛的新方法 总被引:2,自引:0,他引:2
提出了加速牛顿迭代收敛的新思想,构造出一类加权牛顿迭代格式,通过选取最优加权因子,使得该格式具有高阶收敛性和较小的渐近误差常数。 相似文献