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241.
Qualitative studies of alcohol's ritual influences indicate that college undergraduates who drink heavily tend to view alcohol use as integral to the student role and feel entitled to drink irresponsibly. Our analyses, based on a standardized measure of these beliefs administered to approximately 300 students, confirmed these findings. Among our sample, beliefs about alcohol and the college experience had an effect on levels of alcohol consumption similar in magnitude to that of other variables commonly associated with a risk for heavy drinking. Moreover, the alcohol beliefs index moderated the effects of three risk factors--gender, high school drinking, and friends' use of alcohol--on respondents' drinking behaviors. These findings are discussed within the context of the anthropological literature on liminality and rites of passage and with regard to strategies for intervention that address the structural roots of the widespread abuse of alcohol on college campuses.  相似文献   
242.
The Lomax (Pareto II) distribution has found wide application in a variety of fields. We analyze the second-order bias of the maximum likelihood estimators of its parameters for finite sample sizes, and show that this bias is positive. We derive an analytic bias correction which reduces the percentage bias of these estimators by one or two orders of magnitude, while simultaneously reducing relative mean squared error. Our simulations show that this performance is very similar to that of a parametric bootstrap correction based on a linear bias function. Three examples with actual data illustrate the application of our bias correction.  相似文献   
243.
An empirical Bayes problem has an unknown prior to be estimated from data. The predictive recursion (PR) algorithm provides fast nonparametric estimation of mixing distributions and is ideally suited for empirical Bayes applications. This article presents a general notion of empirical Bayes asymptotic optimality, and it is shown that PR-based procedures satisfy this property under certain conditions. As an application, the problem of in-season prediction of baseball batting averages is considered. There the PR-based empirical Bayes rule performs well in terms of prediction error and ability to capture the distribution of the latent features.  相似文献   
244.
ABSTRACT

We derive an analytic expression for the bias of the maximum likelihood estimator of the parameter in a doubly-truncated Poisson distribution, which proves highly effective as a means of bias correction. For smaller sample sizes, our method outperforms the alternative of bias correction via the parametric bootstrap. Bias is of little concern in the positive Poisson distribution, the most common form of truncation in the applied literature. Bias appears to be the most severe in the doubly-truncated Poisson distribution, when the mean of the distribution is close to the right (upper) truncation.  相似文献   
245.
Estimation of finite mixture models when the mixing distribution support is unknown is an important problem. This article gives a new approach based on a marginal likelihood for the unknown support. Motivated by a Bayesian Dirichlet prior model, a computationally efficient stochastic approximation version of the marginal likelihood is proposed and large-sample theory is presented. By restricting the support to a finite grid, a simulated annealing method is employed to maximize the marginal likelihood and estimate the support. Real and simulated data examples show that this novel stochastic approximation and simulated annealing procedure compares favorably with existing methods.  相似文献   
246.
The 40th Anniversary of the Society for Risk Analysis presents an apt time to step back and review the field of risk communication. In this review, we first evaluate recent debates over the field's current state and future directions. Our takeaway is that efforts to settle on a single, generic version of what constitutes risk communication will be less productive than an open-minded exploration of the multiple forms that comprise today's vibrant interdisciplinary field. We then review a selection of prominent cognitive, cultural, and social risk communication scholarship appearing in the published literature since 2010. Studies on trust in risk communication messengers continued to figure prominently, while new research directions emerged on the opportunities and critical challenges of enhancing transparency and using social media. Research on message attributes explored how conceptual insights particularly relating to framing, affective and emotional responses, and uncertainty might be operationalized to improve message effectiveness. Studies consistently demonstrated the importance of evaluation and how varying single attributes alone is unlikely to achieve desired results. Research on risk communication audiences advanced on risk perception and multiway engagement with notable interest in personal factors such as gender, race, age, and political orientation. We conclude by arguing that the field's interdisciplinary tradition should be further nurtured to drive the next evolutionary phase of risk communication research.  相似文献   
247.
Abstract

Virtual reality (VR) has emerged as a promising technological intervention for anxiety disorders. However, there are no existing standards and best practices to evaluate the effectiveness of environments to achieve their intervention goals. The purpose of this study was to develop a VR intervention for student veterans with social anxiety disorder and test feasibility utilizing a three-stage development model. The development of a therapeutic VR environment may benefit from an interdisciplinary collaboration of researchers from various fields of study. Utilizing three stages of prototyping with two virtual reality platforms, fully immersive video (n?=?6) and three-dimensional (3-D) immersive virtual reality (n?=?8), the research team designed an intervention for student veterans with social anxiety disorder, testing bio-reactivity of participants. Results of prototyping include user feedback validating increased stress levels and increased bio-reactivity specifically in galvanic skin response and heart rate elevation. Implications include the use of 360° video for prototyping 3-D virtual reality interventions.  相似文献   
248.
In school choice systems, families choose among publicly funded schools, and schools compete for students and resources. Using neoinstitutionalist and relational inequality theories, our article reinterprets recent critical sociological and education research to show how such markets involve actors' enacting myths; these beliefs and their associated practices normalized white, privileged consumption as a basis for revamping public education as market exchanges between schools and families. Proponents argue that choice empowers individuals, focuses organizations on improving quality, and benefits society more broadly by reducing inequality and segregation. We argue that such school choice myths' excessive emphases on individual decision‐making and provider performance obscure the actual impacts of school choice systems upon people, organizations, and society. First, rather than enlarging alternatives that families can easily research, select, and (if needed) exit, school choice systems often simulate options, especially for disadvantaged populations. Second, rather than focusing schools' efforts on performance, innovation, and accountability, they can encourage organizational decoupling, homogeneity, and deception. Third, rather than reducing societal harms, they can deepen inequalities and alienation. Future research should examine both how markets are animated by bounded relationality—routines that enable them to form, maintain, and complete exchanges with organizations—and how activism can challenge marketization.  相似文献   
249.
Urban Ecosystems - Urban insect communities are structured by hierarchical filters including regional processes, human facilitation, and species interactions. We sought to inform future urban...  相似文献   
250.
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