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   18686篇
  免费   448篇
管理学   2522篇
民族学   75篇
人口学   1643篇
丛书文集   86篇
教育普及   3篇
理论方法论   1574篇
综合类   206篇
社会学   9228篇
统计学   3797篇
  2021年   99篇
  2020年   245篇
  2019年   352篇
  2018年   440篇
  2017年   590篇
  2016年   419篇
  2015年   314篇
  2014年   434篇
  2013年   3520篇
  2012年   540篇
  2011年   538篇
  2010年   395篇
  2009年   360篇
  2008年   367篇
  2007年   399篇
  2006年   399篇
  2005年   373篇
  2004年   320篇
  2003年   300篇
  2002年   325篇
  2001年   454篇
  2000年   420篇
  1999年   422篇
  1998年   288篇
  1997年   270篇
  1996年   323篇
  1995年   305篇
  1994年   317篇
  1993年   313篇
  1992年   356篇
  1991年   328篇
  1990年   345篇
  1989年   311篇
  1988年   288篇
  1987年   255篇
  1986年   249篇
  1985年   269篇
  1984年   277篇
  1983年   240篇
  1982年   216篇
  1981年   182篇
  1980年   191篇
  1979年   200篇
  1978年   179篇
  1977年   156篇
  1976年   143篇
  1975年   148篇
  1974年   110篇
  1973年   107篇
  1971年   93篇
排序方式: 共有10000条查询结果,搜索用时 468 毫秒
751.
This paper is about satisficing behaviour. Rather tautologically, this is when decision-makers are satisfied with achieving some objective, rather than in obtaining the best outcome. The term was coined by Simon (Q J Econ 69:99–118, 1955), and has stimulated many discussions and theories. Prominent amongst these theories are models of incomplete preferences, models of behaviour under ambiguity, theories of rational inattention, and search theories. Most of these, however, seem to lack an answer to at least one of two key questions: when should the decision-maker (DM) satisfice; and how should the DM satisfice. In a sense, search models answer the latter question (in that the theory tells the DM when to stop searching), but not the former; moreover, usually the question as to whether any search at all is justified is left to a footnote. A recent paper by Manski (Theory Decis. doi: 10.1007/s11238-017-9592-1, 2017) fills the gaps in the literature and answers the questions: when and how to satisfice? He achieves this by setting the decision problem in an ambiguous situation (so that probabilities do not exist, and many preference functionals can therefore not be applied) and by using the Minimax Regret criterion as the preference functional. The results are simple and intuitive. This paper reports on an experimental test of his theory. The results show that some of his propositions (those relating to the ‘how’) appear to be empirically valid while others (those relating to the ‘when’) are less so.  相似文献   
752.
We implement a risky choice experiment based on one-dimensional choice variables and risk neutrality induced via binary lottery incentives. Each participant confronts many parameter constellations with varying optimal payoffs. We assess (sub)optimality, as well as (non)optimal satisficing by eliciting aspirations in addition to choices. Treatments differ in the probability that a binary random event, which are payoff—but not optimal choice—relevant is experimentally induced and whether participants choose portfolios directly or via satisficing, i.e., by forming aspirations and checking for satisficing before making their choice. By incentivizing aspiration formation, we can test satisficing, and in cases of satisficing, determine whether it is optimal.  相似文献   
753.
754.
755.
In this paper, we assume that the duration of a process has two different intrinsic components or phases which are independent. The first is the time it takes for a trade to be initiated in the market (for example, the time during which agents obtain knowledge about the market in which they are operating and accumulate information, which is coherent with Brownian motion) and the second is the subsequent time required for the trade to develop into a complete duration. Of course, if the first time is zero then the trade is initiated immediately and no initial knowledge is required. If we assume a specific compound Bernoulli distribution for the first time and an inverse Gaussian distribution for the second, the resulting convolution model has a mixture of an inverse Gaussian distribution with its reciprocal, which allows us to specify and test the unobserved heterogeneity in the autoregressive conditional duration (ACD) model.

Our proposals make it possible not only to capture various density shapes of the durations but also easily to accommodate the behaviour of the tail of the distribution and the non monotonic hazard function. The proposed model is easy to fit and characterizes the behaviour of the conditional durations reasonably well in terms of statistical criteria based on point and density forecasts.  相似文献   

756.
In clinical trials, missing data commonly arise through nonadherence to the randomized treatment or to study procedure. For trials in which recurrent event endpoints are of interests, conventional analyses using the proportional intensity model or the count model assume that the data are missing at random, which cannot be tested using the observed data alone. Thus, sensitivity analyses are recommended. We implement the control‐based multiple imputation as sensitivity analyses for the recurrent event data. We model the recurrent event using a piecewise exponential proportional intensity model with frailty and sample the parameters from the posterior distribution. We impute the number of events after dropped out and correct the variance estimation using a bootstrap procedure. We apply the method to an application of sitagliptin study.  相似文献   
757.
Optimum experimental design theory has recently been extended for parameter estimation in copula models. The use of these models allows one to gain in flexibility by considering the model parameter set split into marginal and dependence parameters. However, this separation also leads to the natural issue of estimating only a subset of all model parameters. In this work, we treat this problem with the application of the \(D_s\)-optimality to copula models. First, we provide an extension of the corresponding equivalence theory. Then, we analyze a wide range of flexible copula models to highlight the usefulness of \(D_s\)-optimality in many possible scenarios. Finally, we discuss how the usage of the introduced design criterion also relates to the more general issue of copula selection and optimal design for model discrimination.  相似文献   
758.
759.
760.
Who Is to Blame?     
We present the results of a content analysis of communications related to the act of terrorism at Domodedovo airport. They show that mass media plays a significant role as a source of factual, undigested information. The theoretical value of the results is that they show a significant number of cases where an actor is accused with no reference to his actions or nonactions. The range of types of complicity in terrorist activity was substantial.  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