首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1434篇
  免费   20篇
  国内免费   40篇
化学   32篇
力学   33篇
综合类   3篇
数学   1355篇
物理学   71篇
  2023年   13篇
  2022年   19篇
  2021年   23篇
  2020年   20篇
  2019年   17篇
  2018年   23篇
  2017年   12篇
  2016年   12篇
  2015年   15篇
  2014年   44篇
  2013年   110篇
  2012年   105篇
  2011年   51篇
  2010年   40篇
  2009年   88篇
  2008年   98篇
  2007年   65篇
  2006年   59篇
  2005年   54篇
  2004年   44篇
  2003年   26篇
  2002年   43篇
  2001年   31篇
  2000年   31篇
  1999年   30篇
  1998年   29篇
  1997年   25篇
  1996年   30篇
  1995年   25篇
  1994年   23篇
  1993年   11篇
  1992年   14篇
  1991年   6篇
  1990年   6篇
  1989年   4篇
  1988年   3篇
  1987年   5篇
  1986年   23篇
  1985年   28篇
  1984年   27篇
  1983年   19篇
  1982年   28篇
  1981年   16篇
  1980年   31篇
  1979年   24篇
  1978年   32篇
  1977年   5篇
  1972年   2篇
  1969年   2篇
  1967年   1篇
排序方式: 共有1494条查询结果,搜索用时 18 毫秒
941.
ABSTRACT

We give the explicit classifications of orbits in the Jordan algebra 𝔍 over the group E 6(?26) and the Freudenthal, R -vector space 𝔓 over the group E 7(?25).

Communicated by E. Zelmanov  相似文献   
942.
943.
944.
Optimization of probabilistic multiple response surfaces   总被引:1,自引:0,他引:1  
Response surface methodology (RSM) is a statistical-mathematical method used for analyzing and optimizing the experiments. In analysis process, experts usually face several input variables having effect on several outputs called response variables. Simultaneous optimization of the correlated response variables has become more important in complex systems. In this paper multi-response surfaces and their related stochastic nature have been modeled and optimized by Goal Programming (GP) in which the weights of response variables have been obtained through a Group Decision Making (GDM) process. Because of existing uncertainty in the stochastic model, some stochastic optimization methods have been applied to find robust optimum results. At the end, the proposed method is described numerically and analytically.  相似文献   
945.
In this paper we apply stochastic dual dynamic programming decomposition to a nonconvex multistage stochastic hydrothermal model where the nonlinear water head effects on production and the nonlinear dependence between the reservoir head and the reservoir volume are modeled. The nonconvex constraints that represent the production function of a hydro plant are approximated by McCormick envelopes. These constraints are split into smaller regions and the McCormick envelopes are used for each region. We use binary variables for this disjunctive programming approach and solve the problem with a decomposition method. We resort to a variant of the L-shaped method for solving the MIP subproblem with binary variables at any stage inside the stochastic dual dynamic programming algorithm. A realistic large-scale case study is presented.  相似文献   
946.
We consider the problem of fitting a continuous piecewise linear function to a finite set of data points, modeled as a mathematical program with convex objective. We review some fitting problems that can be modeled as convex programs, and then introduce mixed-binary generalizations that allow variability in the regions defining the best-fit function’s domain. We also study the additional constraints required to impose convexity on the best-fit function.  相似文献   
947.
This paper proposes a column generation approach based on the Lagrangean relaxation with clusters to solve the unconstrained binary quadratic programming problem that consists of maximizing a quadratic objective function by the choice of suitable values for binary decision variables. The proposed method treats a mixed binary linear model for the quadratic problem with constraints represented by a graph. This graph is partitioned in clusters of vertices forming sub-problems whose solutions use the dual variables obtained by a coordinator problem. The column generation process presents alternative ways to find upper and lower bounds for the quadratic problem. Computational experiments were performed using hard instances and the proposed method was compared against other methods presenting improved results for most of these instances.  相似文献   
948.
Probabilistically constrained quadratic programming (PCQP) problems arise naturally from many real-world applications and have posed a great challenge in front of the optimization society for years due to the nonconvex and discrete nature of its feasible set. We consider in this paper a special case of PCQP where the random vector has a finite discrete distribution. We first derive second-order cone programming (SOCP) relaxation and semidefinite programming (SDP) relaxation for the problem via a new Lagrangian decomposition scheme. We then give a mixed integer quadratic programming (MIQP) reformulation of the PCQP and show that the continuous relaxation of the MIQP is exactly the SOCP relaxation. This new MIQP reformulation is more efficient than the standard MIQP reformulation in the sense that its continuous relaxation is tighter than or at least as tight as that of the standard MIQP. We report preliminary computational results to demonstrate the tightness of the new convex relaxations and the effectiveness of the new MIQP reformulation.  相似文献   
949.
Container vessel stowage planning is a hard combinatorial optimization problem with both high economic and environmental impact. We have developed an approach that often is able to generate near-optimal plans for large container vessels within a few minutes. It decomposes the problem into a master planning phase that distributes the containers to bay sections and a slot planning phase that assigns containers of each bay section to slots. In this paper, we focus on the slot planning phase of this approach and present a Constraint Programming and Integer Programming model for stowing a set of containers in a single bay section. This so-called slot planning problem is NP-hard and often involves stowing several hundred containers. Using state-of-the-art constraint solvers and modeling techniques, however, we were able to solve 90% of 236 real instances from our industrial collaborator to optimality within 1 second. Thus, somewhat to our surprise, it is possible to solve most of these problems optimally within the time required for practical application.  相似文献   
950.
In this paper, the wrap-around L2L2-discrepancy (WD) of asymmetrical design is represented as a quadratic form, thus the problem of constructing a uniform design becomes a quadratic integer programming problem. By the theory of optimization, some theoretic properties are obtained. Algorithms for constructing uniform designs are then studied. When the number of runs nn is smaller than the number of all level-combinations mm, the construction problem can be transferred to a zero–one quadratic integer programming problem, and an efficient algorithm based on the simulated annealing is proposed. When n≥mnm, another algorithm is proposed. Empirical study shows that when nn is large, the proposed algorithms can generate designs with lower WD compared to many existing methods. Moreover, these algorithms are suitable for constructing both symmetrical and asymmetrical designs.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号