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   558篇
  免费   48篇
  国内免费   14篇
化学   19篇
力学   17篇
综合类   11篇
数学   509篇
物理学   64篇
  2023年   10篇
  2022年   3篇
  2021年   8篇
  2020年   13篇
  2019年   10篇
  2018年   11篇
  2017年   14篇
  2016年   12篇
  2015年   12篇
  2014年   25篇
  2013年   62篇
  2012年   23篇
  2011年   30篇
  2010年   26篇
  2009年   32篇
  2008年   26篇
  2007年   45篇
  2006年   33篇
  2005年   37篇
  2004年   36篇
  2003年   24篇
  2002年   11篇
  2001年   9篇
  2000年   17篇
  1999年   18篇
  1998年   6篇
  1997年   6篇
  1996年   9篇
  1995年   10篇
  1994年   3篇
  1993年   5篇
  1992年   3篇
  1991年   3篇
  1990年   1篇
  1989年   7篇
  1988年   8篇
  1986年   3篇
  1985年   2篇
  1984年   2篇
  1983年   1篇
  1978年   1篇
  1977年   2篇
  1975年   1篇
排序方式: 共有620条查询结果,搜索用时 390 毫秒
41.
本文提出一种估计与调控飞行员宏观数量的方法.文章给出了当航空兵的兵力规模保持稳定、只考虑飞行员年龄分布的情况下,战斗部队飞行员和航校教员总数量与每年的补充量、淘汰率、服役年限之间的函数关系;给出了当航空兵的兵力规模需要变更时,尽快达到变更目标的数学规划模型,模型考虑了每年的补充量、淘汰率、服役年限以及航校学制、规模和效率之间的关系.  相似文献   
42.
This paper addresses two important issues that may affect the operations efficiency in the recycling industry. First, the industry contains many small-scale and inefficient recycling firms, especially in developing countries. Second, the output from recycling a waste product often yields multiple recycled products that cannot all be sold efficiently by a single firm. To address these two issues, this paper examines how different firms can cooperate in their recycling and pricing decisions using cooperative game theory. Recycling operations under both joint and individual productions with different cost structures are considered. Decisions include the quantity of waste product to recycle and the price at which to sell each recycled product on each firm’s market. These decisions can be made jointly by multiple cooperating firms to maximize total profit. We design allocation schemes for maximized total profit to encourage cooperation among all firms. Managerial insights are provided from both environmental and economic perspectives.  相似文献   
43.
The traditional hypothesis of “rationality” is far from perfect. Models of fairness solely based on consequence cannot explain why the same consequence of an action is perceived and reciprocated differently. A reciprocity model which accounts for both consequence and its underlying intention is presented in this paper to illustrate the effect of intention in a traditional dyadic channel where one supplier plays a Stackelberg-like game with one retailer. This research aims to investigate how reciprocity may affect the members’ decisions and the channel’s coordination. In this study, two scenarios are discussed: (1) the retailer has a preference for reciprocity while the supplier does not and (2) both the retailer and the supplier have a preference for reciprocity. Results for acrimonious supply chain (γμ>1γμ>1) and harmonious supply chain (γμ?1γμ?1) are analyzed. Furthermore, we derive equilibria under the two scenarios and prove the existence and the uniqueness of the equilibria. The results show that intention plays an important role in decision making of the supply chain and will significantly change the equilibria. Moreover, an acrimonious supply chain can be coordinated with a simple wholesale-price contract under certain conditions, which can never happen in a traditional channel. A harmonious supply chain, however, cannot be coordinated in any way.  相似文献   
44.
引入了集列的极限运算与二元集运算之间的共轭可交换性的概念,讨论了常见的和重要的集列的极限运算与集代数运算之间所具有的共轭可交换性质,在一般的情形下证明了共轭可交换性是集类的极限运算生成类对集代数运算具有封闭性的一个充分条件,使得集合形式的单调类定理的理论得到了统一的解释,并且证明更简单,思路更清晰,最后还给出了一个新的集合形式的单调类定理.  相似文献   
45.
1IntroductionAsurfaceisacompactclosed2-manifold.Theorielltable(non-orielltable)surfaceofgenuskisthespherewitllkhandles(crosscaPs)denotedbySk(Nk).AmapMollSk(Nk)meansthatitsunderlyinggraphnlaybedrownou(embeddedin)itsuchthatllthpairofedgesintersectataninnerpoilltalldeachfaceishomeomorphictothedisc.Amapisrootedifanedgewithadirectiollalongtheedge,alldasideoftl1eedgeisdistinguisl1ed.Tworootedmapsareconsideredtobethesal11eifthereisanisomorphismpreserviIlgtl1erooting.ArootedEuleriall1llapissuchaon…  相似文献   
46.
We introduce a new concept of generalized Knaster–Kuratowski–Mazurkiewicz (KKM) family of sets and related to this we obtain fixed point theorems and sections results in homotopically trivial spaces.  相似文献   
47.
A novel class of non-classical fullerenes, having pentagon–heptagon pairs, as in azulene, is modeled. The various coverings, sometimes alternating azulenic and benzenic units, are designed by some new sequences of map operations or generalized operations. The hypothetical azulenic fullerenes are characterized by PM3 semiempirical data and POAV1 strain energy SE. Their aromaticity is discussed in the light of several criteria. The HOMA index of aromaticity enabled evaluation of global and local aromaticity of the designed fullerenes.  相似文献   
48.
产销平衡运输问题的表上作业法解法的一个注记   总被引:1,自引:0,他引:1  
本文给出了用表上作业法求解产销平衡运输问题当出现退化时在相应空格填“O”的更为明确的规则,利用该规则可以避免可能存在的多余计算。本文还给出了用改进后的表上作业法求解指派问题的方法和步骤,该方法与求解指派问题的常用方法“匈牙利法”相比,具有手工计算更为简便的优点。  相似文献   
49.
本文针对评审工作中打分专家对各指标熟悉度不同的实际问题,提出一种基于区间评分的评价算法。因该算法通过专家给出评分区间长度反映出专家对各评审指标的熟悉度,为此定义区间的加法、减法、数乘运算及区间值的概念,这样可解决区间无法直接排序的问题。最后给出了该算法的具体步骤和实际算例。  相似文献   
50.
The efficiency of hierarchical matrices is based on the approximate evaluation of usual matrix operations. The introduced approximation error may, however, lead to a loss of important matrix properties. In this article we present a technique which preserves the positive definiteness of a matrix independently of the approximation quality. The importance of this technique is illustrated by an elliptic mixed boundary value problem with tiny Dirichlet part. Copyright © 2007 John Wiley & Sons, Ltd.  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