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   3720篇
  免费   932篇
  国内免费   1篇
管理学   1103篇
民族学   5篇
人口学   46篇
丛书文集   2篇
理论方法论   818篇
综合类   17篇
社会学   1637篇
统计学   1025篇
  2021年   93篇
  2020年   161篇
  2019年   336篇
  2018年   202篇
  2017年   354篇
  2016年   348篇
  2015年   337篇
  2014年   359篇
  2013年   565篇
  2012年   360篇
  2011年   252篇
  2010年   254篇
  2009年   148篇
  2008年   183篇
  2007年   96篇
  2006年   102篇
  2005年   92篇
  2004年   107篇
  2003年   72篇
  2002年   77篇
  2001年   82篇
  2000年   68篇
  1999年   2篇
  1997年   1篇
  1991年   1篇
  1980年   1篇
排序方式: 共有4653条查询结果,搜索用时 281 毫秒
931.
Temporary price reductions (sales) are common for many goods and naturally result in large increases in the quantity sold. Demand estimation based on temporary price reductions may mismeasure the long‐run responsiveness to prices. In this paper we quantify the extent of the problem and assess its economic implications. We structurally estimate a dynamic model of consumer choice using two years of scanner data on the purchasing behavior of a panel of households. The results suggest that static demand estimates, which neglect dynamics, (i) overestimate own‐price elasticities by 30 percent, (ii) underestimate cross‐price elasticities by up to a factor of 5, and (iii) overestimate the substitution to the no‐purchase or outside option by over 200 percent. This suggests that policy analysis based on static elasticity estimates will underestimate price–cost margins and underpredict the effects of mergers.  相似文献   
932.
Manufacturers often face a choice of whether to recover the value in their end‐of‐life products through remanufacturing. In many cases, firms choose not to remanufacture, as they are (rightly) concerned that the remanufactured product will cannibalize sales of the higher‐margin new product. However, such a strategy may backfire for manufacturers operating in industries where their end‐of‐life products (cell phones, tires, computers, automotive parts, etc.) are attractive to third‐party remanufacturers, who may seriously cannibalize sales of the original manufacturer. In this paper, we develop models to support a manufacturer's recovery strategy in the face of a competitive threat on the remanufactured product market. We first analyze the competition between new and remanufactured products produced by a monopolist manufacturer and identify conditions under which the firm would choose not to remanufacture its products. We then characterize the potential profit loss due to external remanufacturing competition and analyze two entry‐deterrent strategies: remanufacturing and preemptive collection. We find that a firm may choose to remanufacture or preemptively collect its used products to deter entry, even when the firm would not have chosen to do so under a pure monopoly environment. Finally, we discuss conditions under which each strategy is more beneficial.  相似文献   
933.
Companies are increasingly realizing the need to coordinate their manufacturing and remanufacturing operations. This can be a challenge due to the inherent variability in the condition and amount of returns, which has a direct impact on remanufacturing costs and leadtimes. In this paper, we develop a modeling framework to compare two alternative strategies that use either manufacturing or remanufacturing as the primary means of satisfying customer demand. Of course, in the event that the demand cannot be met by the prioritized process, the secondary process is used as a contingency. In our basic model, the priority decisions are made at the component level in replenishing the serviceable inventory, while the disposal and new component ordering decisions are made independently. The second model represents the coordination of remanufacturable and new component inventory control decisions. Using simulation‐based optimization on a large number of experiments, we observe that when prioritization is in the upstream echelon and there is no coordination in managing component stocks, there exists a critical return ratio, below which it is beneficial to give priority to manufacturing and above which it is beneficial to give priority to remanufacturing. We also see that coordinated control of the component inventories considerably reduces the importance of prioritization. These observations remain valid when congestion in the shop floor is also taken into account. We also study the benefits of state‐dependent dispatching policies in a realistic case.  相似文献   
934.
RFID (Radio‐Frequency Identification) technology has shown itself to be a promising technology to track movements of goods in a supply chain. As such, it can give unprecedented visibility to the supply chain. Such visibility can save labor cost, improve supply chain coordination, reduce inventory and increase product availability. Industry reports and white papers are now filled with estimates and proclamations of the benefits and quantified values of RFID. Early adopters are now rallying more and more followers. However, most such claims are educated guesses at best and are not substantiated, that is, they are not based on detailed, model‐based analysis. This paper argues that there is a huge credibility gap of the value of RFID, and that a void exists in showing how the proclaimed values are arrived at, and how those values can be realized. The paper shows that this credibility gap must be filled with solid model analysis, and therefore presents a great opportunity for the Production and Operations Management (POM) research community. The paper reviews some of the ongoing research efforts that attempt to close the credibility gap, and suggests additional directions for further strengthening the POM's contribution to help industry realize the full potentials of RFID.  相似文献   
935.
Analyzing the proliferation of item‐level RFID, recent studies have identified the cost sharing of the technology as a gating issue. Various qualitative studies have predicted that conflict will arise, in particular in decentralized supply chains, from the fact that the benefits and the costs resulting from item‐level RFID are not symmetrically distributed among supply chain partners. To contribute to a better understanding of this situation, we consider a supply chain with one manufacturer and one retailer. Within the context of this retail supply chain, we present analytic models of the benefits of item‐level RFID to both supply chain partners. We examine both the case of a dominant manufacturer as well as the case of a dominant retailer, and we analyze the results of an introduction of item‐level RFID to such a supply chain depending on these market power characteristics. Under each scenario, we show how the cost of item‐level RFID should be allocated among supply chain partners such that supply chain profit is optimized.  相似文献   
936.
Multiple-arm dose-response superiority trials are widely studied for continuous and binary endpoints, while non-inferiority designs have been studied recently in two-arm trials. In this paper, a unified asymptotic formulation of a sample size calculation for k-arm (k>0) trials with different endpoints (continuous, binary and survival endpoints) is derived for both superiority and non-inferiority designs. The proposed method covers the sample size calculation for single-arm and k-arm (k> or =2) designs with survival endpoints, which has not been covered in the statistic literature. A simple, closed form for power and sample size calculations is derived from a contrast test. Application examples are provided. The effect of the contrasts on the power is discussed, and a SAS program for sample size calculation is provided and ready to use.  相似文献   
937.
938.
This study prospectively examines the association between discord with in‐laws and the long‐term relationship success of husbands and wives who had been married for an average of almost 2 decades. We hypothesized that the quality of spouses' relationships with their parents‐in‐law would predict spouses' marital success. In addition, this study underscores the causal role of in‐laws by examining the influence of marital success on relationships with in‐laws. For wives, discord with mothers‐ and fathers‐in‐law predicted own perceptions of marital success at a later time period. Results were slightly different for husbands' discord with fathers‐in‐law. The reverse (marital success predicting less discord with in‐laws) was only true for husbands. The study also explored the influence of spouses' discord with in‐laws on partners' perceptions of marital success. These are among the first prospective, longitudinal findings demonstrating that, even in long‐term marriages, conflicts in extended family relations will erode marital stability, satisfaction, and commitment over time.  相似文献   
939.
Although previous research has noted that children of divorce tend to fare less well than peers raised in families with two biological parents, much less is known about how parents' marital disruption affects children as a continuous process in its different phases. Based on two waves of a large, nationally representative panel, this study demonstrates that even before the disruption, both male and female adolescents from families that subsequently dissolve exhibit more academic, psychological, and behavioral problems than peers whose parents remain married. Families on the verge of breakup are also characterized by less intimate parent‐parent and parent‐child relationships, less parental commitment to children's education, and fewer economic and human resources. These differences in family environment account for most well‐being deficits among adolescents in predisrupted families. Furthermore, the deterioration in different domains of the family environment appears to be associated with maladjustment in different aspects of children's lives. The postdisruption effects on adolescents can either be totally or largely predicted by predisruption factors and by changes in family circumstances during the period coinciding with the disruption. Finally, the analyses indicate that female adolescents are as likely to be affected by the parental divorce process as male adolescents.  相似文献   
940.
COVID‐19 has challenged social workers to engage with health pandemics and provide essential services in conditions of uncertainty and high risk. They have safeguarded children, older adults and diverse adults in ‘at risk’ groups under tough conditions mediated by digital technologies, adhered to government injunctions, maintained social and physical distancing under lockdown and worked from home remotely. Social workers and social care workers have risen to the challenges, providing services with inadequate personal protective equipment and limited supervision and support. This article highlights the degraded physical environments, socio‐economic and political contexts that intensify precariousness and constraints that neoliberalism imposed on professional capacity before and during this health pandemic. It provides guidelines to protect practitioners and service users. It concludes that practitioners ought to understand zoonotic diseases, environmental concerns, acquire disaster expertise and training, widen their practice portfolio and value their contributions to this pandemic. Key Practitioner Message: ? Develop technological skills and innovate to support stressed individuals, safeguard children, adolescents and elders and deal with poverty and unemployment; ? Use digital technologies involving peers to explore tricky situations, examine ethical dilemmas through scenario building exercises, and tips for self‐care; ? Contribute to environmental protections that prevent the spread of zoonotic diseases like COVID‐19; ? Seek supervision and support for disaster‐based training from your line manager.  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