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   2532篇
  免费   98篇
  国内免费   42篇
管理学   489篇
民族学   6篇
人才学   1篇
人口学   20篇
丛书文集   202篇
理论方法论   36篇
综合类   1610篇
社会学   30篇
统计学   278篇
  2024年   10篇
  2023年   22篇
  2022年   40篇
  2021年   33篇
  2020年   45篇
  2019年   45篇
  2018年   44篇
  2017年   61篇
  2016年   51篇
  2015年   96篇
  2014年   119篇
  2013年   185篇
  2012年   177篇
  2011年   160篇
  2010年   140篇
  2009年   163篇
  2008年   142篇
  2007年   147篇
  2006年   157篇
  2005年   155篇
  2004年   144篇
  2003年   131篇
  2002年   109篇
  2001年   83篇
  2000年   58篇
  1999年   38篇
  1998年   18篇
  1997年   22篇
  1996年   15篇
  1995年   13篇
  1994年   10篇
  1993年   4篇
  1992年   11篇
  1991年   7篇
  1990年   5篇
  1989年   4篇
  1988年   2篇
  1987年   3篇
  1986年   1篇
  1983年   1篇
  1981年   1篇
排序方式: 共有2672条查询结果,搜索用时 557 毫秒
1.
针对"互联网+大数据"优化电商配送服务质量问题,明确不同收货方的质量需求稳定性,引导电商根据收货方不同质量敏感性提供相对精准服务,提升配送服务质量。模拟投票结果的形成过程聚类得到收货方对服务质量偏好的记忆性特征:(1)"无记忆"型收货方;(2)"记忆"型收货方;(3)"不确定"型收货方;(4)收货方总体。进一步推导不同规划类型求解空间,设计得到"无记忆"型收货方动态规划精确求解方法,及其他三种类型近似求解粒子群算法。研究过程中,配送资源质量感知度被嵌入到模型约束;"无记忆"型收货方的质量需求规划问题转化为零库存策略最优解问题,进而证明存在精确解;"记忆"型收货方呈现出对质量感知的累积;"不确定"型收货方模型通过赋值即可得总体收货方表达式。结果表明:数据驱动研究框架借助大数据资源,使得电商更易通过收货方的质量偏好设计更加匹配的配送方案;不确定服务需求得到有效满足,投入成本的利用率更高;通过特征分类的方式,尽可能地抽取能够精确最优化的部分,缩小NP范围,提高整体求解的精确度。  相似文献   
2.
Managing risk in infrastructure systems implies dealing with interdependent physical networks and their relationships with the natural and societal contexts. Computational tools are often used to support operational decisions aimed at improving resilience, whereas economics‐related tools tend to be used to address broader societal and policy issues in infrastructure management. We propose an optimization‐based framework for infrastructure resilience analysis that incorporates organizational and socioeconomic aspects into operational problems, allowing to understand relationships between decisions at the policy level (e.g., regulation) and the technical level (e.g., optimal infrastructure restoration). We focus on three issues that arise when integrating such levels. First, optimal restoration strategies driven by financial and operational factors evolve differently compared to those driven by socioeconomic and humanitarian factors. Second, regulatory aspects have a significant impact on recovery dynamics (e.g., effective recovery is most challenging in societies with weak institutions and regulation, where individual interests may compromise societal well‐being). And third, the decision space (i.e., available actions) in postdisaster phases is strongly determined by predisaster decisions (e.g., resource allocation). The proposed optimization framework addresses these issues by using: (1) parametric analyses to test the influence of operational and socioeconomic factors on optimization outcomes, (2) regulatory constraints to model and assess the cost and benefit (for a variety of actors) of enforcing specific policy‐related conditions for the recovery process, and (3) sensitivity analyses to capture the effect of predisaster decisions on recovery. We illustrate our methodology with an example regarding the recovery of interdependent water, power, and gas networks in Shelby County, TN (USA), with exposure to natural hazards.  相似文献   
3.
Abstract

Resource scheduling for emergency relief operations is complex as it has many constraints. However, an effective allocation and sequencing of resources are crucial for the minimization of the completion times in emergency relief operations. Despite the importance of such decisions, only a few mathematical models of emergency relief operations have been studied. This article presents a bi-objective mixed integer programming (MIP) that helps to minimize both the total weighted time of completion of the demand points and the makespan of the total emergency relief operation. A two-phase method is developed to solve the bi-objective MIP problem. Additionally, a case study of hospital network in the Melbourne metropolitan area is used to evaluate the model. The results indicate that the model can successfully support the decisions required in the optimal resource scheduling of emergency relief operations.  相似文献   
4.
反梯度推进:西部产业升级的一种思路   总被引:1,自引:0,他引:1  
反梯度推进理论的核心内容强调 :落后地区要根据自己的实际情况 ,直接引进世界最先进的技术 ,发展自己的高新技术 ,带动传统产业实现超越发展。近几年 ,我国提出的西部大开发战略 ,其实质就是要解决中国区域经济的均衡协调发展问题 ,实现区域经济的跨越式发展。而实现结构优化和产业升级则是根本出路。在这方面 ,反梯度推进理论为我国西部大开发过程中的产业升级提供了非常重要的启示。  相似文献   
5.
因所有制关系是生产关系的总和,所有制必须实现在社会生产再生产的过程之中,因此,我们必须从四大层次实现公有制与市场经济的有效结合。一是所有制结构层次。保持公有制主体地位是保证社会主义市场经济体制有效运作的基础,要大力发展多种所有制经济。二是公有制实现形式层次。更新公有制的微观实现形式,更新公有制的宏观实现形式。三是企业制度层次。建立国有资产出资人制度,合理配置股权,强化所有者约束功能,加强治理结构中的权利组织建设,建立权责分明的组织体系。四是社会剩余产品分配层次。按劳分配与按生产要素分配相结合是通过三个层次实现的:微观经济领域的运行层次,微观经济领域中的所有制结构层次,宏观经济运行层次。  相似文献   
6.
近代中国整合中西文化冲突的价值选择模式及现代启示   总被引:1,自引:0,他引:1  
中国近代文化变迁的过程 ,在一定意义上表现为中西文化的冲突与整合的过程。为整合中西文化冲突 ,近代中国先后采取了文化传统主义、文化折中主义、文化虚无主义与文化综合创新等价值选择模式。近代文化整合的经验教训启示我们 ,在新时期文化建设问题上 ,必须正确处理文化的一元与多元、整体性与可分性、时代性与民族性的关系 ,坚持走综合创新之路  相似文献   
7.
While much used in practice, latent variable models raise challenging estimation problems due to the intractability of their likelihood. Monte Carlo maximum likelihood (MCML), as proposed by Geyer & Thompson (1992 ), is a simulation-based approach to maximum likelihood approximation applicable to general latent variable models. MCML can be described as an importance sampling method in which the likelihood ratio is approximated by Monte Carlo averages of importance ratios simulated from the complete data model corresponding to an arbitrary value of the unknown parameter. This paper studies the asymptotic (in the number of observations) performance of the MCML method in the case of latent variable models with independent observations. This is in contrast with previous works on the same topic which only considered conditional convergence to the maximum likelihood estimator, for a fixed set of observations. A first important result is that when is fixed, the MCML method can only be consistent if the number of simulations grows exponentially fast with the number of observations. If on the other hand, is obtained from a consistent sequence of estimates of the unknown parameter, then the requirements on the number of simulations are shown to be much weaker.  相似文献   
8.
本文给出一类非均匀弦的横向振动的最佳控制,推广了P C Park的结果。这一结果同样适用于同类型振动问题。  相似文献   
9.
所有权是民法 (外 )物权的核心 ,而所用权则是经济法 (内 )物权的核心。创设所用权具有重大的理论意义和实践意义 ,因为这是在财富创造的竞争中赋予人们一种新的权利并使之得到法制的保障 ,这有利于我们坚持“发展才是硬道理”的原则 ,从而把我国的经济建设搞得更好  相似文献   
10.
A test of congruence among distance matrices is described. It tests the hypothesis that several matrices, containing different types of variables about the same objects, are congruent with one another, so they can be used jointly in statistical analysis. Raw data tables are turned into similarity or distance matrices prior to testing; they can then be compared to data that naturally come in the form of distance matrices. The proposed test can be seen as a generalization of the Mantel test of matrix correspondence to any number of distance matrices. This paper shows that the new test has the correct rate of Type I error and good power. Power increases as the number of objects and the number of congruent data matrices increase; power is higher when the total number of matrices in the study is smaller. To illustrate the method, the proposed test is used to test the hypothesis that matrices representing different types of organoleptic variables (colour, nose, body, palate and finish) in single‐malt Scotch whiskies are congruent.  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