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   2446篇
  免费   288篇
  国内免费   19篇
化学   234篇
力学   33篇
综合类   117篇
数学   2023篇
物理学   346篇
  2023年   13篇
  2022年   54篇
  2021年   63篇
  2020年   56篇
  2019年   60篇
  2018年   50篇
  2017年   95篇
  2016年   110篇
  2015年   110篇
  2014年   203篇
  2013年   200篇
  2012年   138篇
  2011年   174篇
  2010年   146篇
  2009年   179篇
  2008年   177篇
  2007年   211篇
  2006年   125篇
  2005年   94篇
  2004年   96篇
  2003年   67篇
  2002年   49篇
  2001年   40篇
  2000年   37篇
  1999年   28篇
  1998年   22篇
  1997年   19篇
  1996年   20篇
  1995年   10篇
  1994年   19篇
  1993年   10篇
  1992年   15篇
  1991年   8篇
  1990年   8篇
  1989年   2篇
  1988年   17篇
  1987年   3篇
  1986年   5篇
  1985年   7篇
  1984年   1篇
  1983年   2篇
  1982年   3篇
  1981年   3篇
  1980年   1篇
  1979年   2篇
  1977年   1篇
排序方式: 共有2753条查询结果,搜索用时 15 毫秒
991.
虚拟企业收益分配问题博弈研究   总被引:43,自引:0,他引:43  
收益分配是虚拟企业的一个敏感而关键的问题,制订合理的收益分配方案对虚拟企业无疑是重要的。本分析了虚拟企业收益分配过程应考虑的因素,在此基础上应用博弈论建立了虚拟企业收益分配的博弈模型,并进行了相关分析,所得出的结论可用于虚拟企业的收益分配策略的制订,最后,论证了在虚拟企业中进行合作机制设计和应用的必要性。  相似文献   
992.
指出城市道路交通拥堵的原因 .确立城市交通中诸关键因素之间相互关系的数学模型  相似文献   
993.
In this paper, we derive an optimal ordering policy for an unreliable newsboy who can place two sequential orders before the start of a single selling season by using a demand forecast update. Supply yield is modeled using a uniform distribution considering both the minimum order guarantee and the maximum yield. Our results indicate that a firm should focus on increasing the minimum order guarantee from a first stage supplier to reduce its total supply chain cost.  相似文献   
994.
In recent work, the authors set classical turnpike theory in the context of the economics of forestry, as developed by Mitra and Wan, and presented two far-reaching results. In this paper, we present a conceptual generalization that takes this theory and configures it around a set in the space of forest configurations rather than around the golden-rule forest configuration. Our set-valued analysis hinges on periodicity and yields the earlier results as corollaries under a non-interiority condition on the felicity function that shrinks the set to the point. The question that we pose, and answer, has obvious relevance to more general contexts and, in particular, to turnpike theory as developed by Samuelson, Gale, McKenzie, and their followers.  相似文献   
995.
闫栋  董明  Abdelaziz Bouras  于随然 《中国物理 B》2011,20(4):40205-040205
In a scale-free network,only a minority of nodes are connected very often,while the majority of nodes are connected rarely. However,what is the ratio of minority nodes to majority nodes resulting from the Matthew effect In this paper,based on a simple preferential random model,the poor-rich demarcation points are found to vary in a limited range,and form a poor-rich demarcation interval that approximates to k/m ∈ [3,4]. As a result,the (cumulative) degree distribution of a scale-free network can be divided into three intervals: the poor interval,the demarcation interval and the rich interval. The inequality of the degree distribution in each interval is measured. Finally,the Matthew effect is applied to the ABC analysis of project management.  相似文献   
996.
In Ref. 1, the author considered the following large-scale forest management problem. There is a system consisting of several factories which all use, as raw material, wood obtained from a large forest region. This forest is divided into a large number of subforests, each of which is felled after it has reached a given age, after which a new forest is immediately planted. The instants in time at which each subforest is felled are assumed to form a stationary point process. In Ref. 1, it was demonstrated how the parameters of the system must be chosen in order to achieve a flow of raw material such that the probability that a shortage will occur is less than a preset value. In the present paper, we consider the problem of maximizing the yield of a single subforest.  相似文献   
997.
Crime is an economically relevant activity. It may represent a mechanism of wealth distribution but also a social and economic burden because of the interference with regular legal activities and the cost of the law enforcement system. Sometimes it may be less costly for the society to allow for some level of criminality. However, a drawback of such a policy is that it may lead to a high increase of criminal activity, that may become hard to reduce later on. Here we investigate the level of law enforcement required to keep crime within acceptable limits. A sharp phase transition is observed as a function of the probability of punishment. We also analyze other consequences of criminality as the growth of the economy, the inequality in the wealth distribution (the Gini coefficient) and other relevant quantities under different scenarios of criminal activity and probabilities of apprehension.  相似文献   
998.
In the Minority, Majority and Dollar Games (MG, MAJG, $G) agents compete for rewards, acting in accord with the previously best-performing of their strategies. Different aspects/kinds of real-world markets are modelled by these games. In the MG, agents compete for scarce resources; in the MAJG agents imitate the group to exploit a trend; in the $G agents attempt to predict and benefit both from trends and changes in the direction of a market. It has been previously shown that in the MG for a reasonable number of preliminary time steps preceding equilibrium (Time Horizon MG, THMG), agents’ attempt to optimize their gains by active strategy selection is “illusory”: the hypothetical gains of their strategies is greater on average than agents’ actual average gains. Furthermore, if a small proportion of agents deliberately choose and act in accord with their seemingly worst performing strategy, these outperform all other agents on average, and even attain mean positive gain, otherwise rare for agents in the MG. This latter phenomenon raises the question as to how well the optimization procedure works in the THMAJG and TH$G. We demonstrate that the illusion of control is absent in THMAJG and TH$G. This provides further clarification of the kinds of situations subject to genuine control, and those not, in set-ups a priori defined to emphasize the importance of optimization.  相似文献   
999.
Industrial risks increate with technological progress. The study of potential risks is routine in the pharmaceutical–chemical industry. Here, like in other industrial activities, a risk coefficient is introduced that varies within space time limits.A control system of environmental safety and health monitoring processes should be based on the data obtained from Hazard and Operability Studies (HAZOP).The space variable influences the chemical risk coefficient that applies to the whole the production cycle (including waste recycling). For the sake of prevention, many enterprises have adopted the integrated management system, which is now moving to an additional required feature: environment and health protection and safety assurance inside and outside the industrial area (in compliance with UNI, ISO 14000 and OHSAS 18001standards).Our goal is to examine the technological–scientific–environmental changes in the pharmaceutical–chemical sector in order to asses the new extent of chemical regarding management systems.This will entail a cultural change that will call for the necessary economic strategies for industries to implement the appropriate environmental–technological programs.  相似文献   
1000.
网上技术市场正逐步发展成为技术交易的主要形式.本文以中国浙江网上技术市场为例,从其定位和动力模式两方面探讨了网上技术市场的发展模式,以及从信息资源管理、技术交易管理和市场运作三方面探讨了网上技术市场的运行管理机制.  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