全文获取类型
收费全文 | 6540篇 |
免费 | 545篇 |
国内免费 | 496篇 |
专业分类
化学 | 285篇 |
晶体学 | 1篇 |
力学 | 267篇 |
综合类 | 180篇 |
数学 | 6327篇 |
物理学 | 521篇 |
出版年
2024年 | 6篇 |
2023年 | 40篇 |
2022年 | 90篇 |
2021年 | 136篇 |
2020年 | 104篇 |
2019年 | 122篇 |
2018年 | 114篇 |
2017年 | 198篇 |
2016年 | 245篇 |
2015年 | 160篇 |
2014年 | 339篇 |
2013年 | 379篇 |
2012年 | 318篇 |
2011年 | 292篇 |
2010年 | 271篇 |
2009年 | 396篇 |
2008年 | 411篇 |
2007年 | 405篇 |
2006年 | 384篇 |
2005年 | 362篇 |
2004年 | 291篇 |
2003年 | 296篇 |
2002年 | 266篇 |
2001年 | 227篇 |
2000年 | 246篇 |
1999年 | 189篇 |
1998年 | 212篇 |
1997年 | 178篇 |
1996年 | 126篇 |
1995年 | 91篇 |
1994年 | 79篇 |
1993年 | 71篇 |
1992年 | 68篇 |
1991年 | 48篇 |
1990年 | 43篇 |
1989年 | 35篇 |
1988年 | 37篇 |
1987年 | 16篇 |
1986年 | 15篇 |
1985年 | 54篇 |
1984年 | 37篇 |
1983年 | 16篇 |
1982年 | 29篇 |
1981年 | 31篇 |
1980年 | 30篇 |
1979年 | 23篇 |
1978年 | 19篇 |
1977年 | 13篇 |
1976年 | 7篇 |
1974年 | 6篇 |
排序方式: 共有7581条查询结果,搜索用时 125 毫秒
81.
82.
刘国志 《数学的实践与认识》2006,36(12):1-5
提出一个新的具有积压定单的关于模糊订购量的模糊存储模型.在模糊函数原理下,给出了模糊总存储成本.为了寻找最优解,把最优模糊存储模型转化为双目标最优化模型,利用L ingo8.0求解不等式约束问题,我们发现最优解都是确定的实数.此外,当模糊订购量和模糊总需求都是三角形(或权重均为1/2梯形)模糊数时,我们提出模型的最优解与经典的具有积压定单存储模型具有相同的结果. 相似文献
83.
84.
为改进Fuzzy HX环的结果,使之包含Fuzzy商环,提出了弱Fuzzy HX环的概念,研究了它的性质与结构,并重新讨论了拟Fuzzy商环,证明了在正则条件下拟Fuzzy商环与弱Fuzzy HX环的统一性:同时也得到了一致弱Fuzzy HX环与普通Fuzzy商环的关系。 相似文献
85.
Pure adaptive search constructs a sequence of points uniformly distributed within a corresponding sequence of nested regions of the feasible space. At any stage, the next point in the sequence is chosen uniformly distributed over the region of feasible space containing all points that are equal or superior in value to the previous points in the sequence. We show that for convex programs the number of iterations required to achieve a given accuracy of solution increases at most linearly in the dimension of the problem. This compares to exponential growth in iterations required for pure random search. 相似文献
86.
E. Alper Yildirim Xiaofei Fan-Orzechowski 《Computational Optimization and Applications》2006,33(2-3):229-247
We study the maximum stable set problem. For a given graph, we establish several transformations among feasible solutions
of different formulations of Lovász's theta function. We propose reductions from feasible solutions corresponding to a graph
to those corresponding to its induced subgraphs. We develop an efficient, polynomial-time algorithm to extract a maximum stable
set in a perfect graph using the theta function. Our algorithm iteratively transforms an approximate solution of the semidefinite
formulation of the theta function into an approximate solution of another formulation, which is then used to identify a vertex
that belongs to a maximum stable set. The subgraph induced by that vertex and its neighbors is removed and the same procedure
is repeated on successively smaller graphs. We establish that solving the theta problem up to an adaptively chosen, fairly
rough accuracy suffices in order for the algorithm to work properly. Furthermore, our algorithm successfully employs a warm-start
strategy to recompute the theta function on smaller subgraphs. Computational results demonstrate that our algorithm can efficiently
extract maximum stable sets in comparable time it takes to solve the theta problem on the original graph to optimality.
This work was supported in part by NSF through CAREER Grant DMI-0237415. Part of this work was performed while the first author
was at the Department of Applied Mathematics and Statisticsat Stony Brook University, Stony Brook, NY, USA. 相似文献
87.
M. W. Warner 《Fuzzy Sets and Systems》1989,30(3):321-327
An amended proof of a theorem of Franklin's on sequentiality and sequential compactness is presented, and a corresponding fuzzy version formulated using the theory of quasi-coincidence. 相似文献
88.
In this paper we define two classes of quasiconformal mappings,and study their covering properties by methods of module.We obtain some new results.In the meantime,we give new methods to prove Koebe 1/2 covering theorem on convex conformal mappings. 相似文献
89.
C. Zălinescu 《Mathematical Methods of Operations Research》1991,35(4):291-298
In this paper there is stated a result on sets in ordered linear spaces which can be used to show that some properties of the sets are inherited by their convex hulls under suitable conditions. As applications one gives a characterization of weakly efficient points and a duality result for nonconvex vector optimization problems. 相似文献
90.