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   47638篇
  免费   1098篇
  国内免费   1篇
管理学   6606篇
民族学   279篇
人才学   8篇
人口学   5728篇
丛书文集   196篇
教育普及   3篇
理论方法论   4141篇
现状及发展   2篇
综合类   790篇
社会学   22898篇
统计学   8086篇
  2023年   196篇
  2021年   212篇
  2020年   583篇
  2019年   896篇
  2018年   2392篇
  2017年   2772篇
  2016年   1890篇
  2015年   795篇
  2014年   965篇
  2013年   6325篇
  2012年   1617篇
  2011年   2273篇
  2010年   1879篇
  2009年   1572篇
  2008年   1719篇
  2007年   1928篇
  2006年   967篇
  2005年   1123篇
  2004年   1126篇
  2003年   980篇
  2002年   924篇
  2001年   989篇
  2000年   915篇
  1999年   836篇
  1998年   632篇
  1997年   602篇
  1996年   613篇
  1995年   560篇
  1994年   537篇
  1993年   546篇
  1992年   622篇
  1991年   594篇
  1990年   529篇
  1989年   546篇
  1988年   542篇
  1987年   469篇
  1986年   455篇
  1985年   503篇
  1984年   515篇
  1983年   481篇
  1982年   393篇
  1981年   344篇
  1980年   343篇
  1979年   365篇
  1978年   318篇
  1977年   291篇
  1976年   256篇
  1975年   269篇
  1974年   212篇
  1973年   186篇
排序方式: 共有10000条查询结果,搜索用时 554 毫秒
21.
In studies with recurrent event endpoints, misspecified assumptions of event rates or dispersion can lead to underpowered trials or overexposure of patients. Specification of overdispersion is often a particular problem as it is usually not reported in clinical trial publications. Changing event rates over the years have been described for some diseases, adding to the uncertainty in planning. To mitigate the risks of inadequate sample sizes, internal pilot study designs have been proposed with a preference for blinded sample size reestimation procedures, as they generally do not affect the type I error rate and maintain trial integrity. Blinded sample size reestimation procedures are available for trials with recurrent events as endpoints. However, the variance in the reestimated sample size can be considerable in particular with early sample size reviews. Motivated by a randomized controlled trial in paediatric multiple sclerosis, a rare neurological condition in children, we apply the concept of blinded continuous monitoring of information, which is known to reduce the variance in the resulting sample size. Assuming negative binomial distributions for the counts of recurrent relapses, we derive information criteria and propose blinded continuous monitoring procedures. The operating characteristics of these are assessed in Monte Carlo trial simulations demonstrating favourable properties with regard to type I error rate, power, and stopping time, ie, sample size.  相似文献   
22.

Sense of community (SOC) is associated with the quality of community life and the building of social capital. While its linkage to informal social behavior, such as neighboring, is inherent in discussions regarding theory, empirical evidence remains scarce. Moreover, the degree to which neighboring behavior influences SOC over time is largely unknown. Using a latent transition analysis, the effect of neighboring on SOC was investigated over a 5-year span from 2006 to 2011 among a sample of adults (n?=?165) in Arizona. Initially, a latent class analysis identified two SOC subgroups: Low SOC and High SOC. The likelihood of shifts in SOC class membership over 5 years was generally stable, with most individuals staying in the same group (82.3% Low SOC; 92.4% High SOC). Neighboring behavior and socio-demographic covariates impacted the likelihood that individuals changed classes, with 25.3% of Low SOC individuals transitioning to High SOC in 2011 and 55.4% of High SOC individuals moving to Low SOC in 2011. Specifically, having an income greater than $60,000 and visiting with neighbors lessened the likelihood of being in the Low SOC class in 2006; and length of residence and exchanging favors with neighbors lessened the likelihood of being in the Low SOC class in 2011. These findings have implications for both community design and community development practice. Design and development interventions that promote greater social interaction may help build and sustain SOC over time.

  相似文献   
23.
Social media is pervasive in the lives of young people, and this paper critically analyses how politically engaged young people integrate social media use into their existing organisations and political communications. This qualitative research project studied how young people from a broad range of existing political and civic groups use social media for sharing information, mobilisation and, increasingly, as a means to redefine political action and political spaces. Twelve in-person focus groups were conducted in Australia, the USA and the UK with matched affinity groups based on university campuses. The groups were of four types: party political group, issue-based group, identity-based group and social group. Our focus group findings suggest that this in-depth approach to understanding young people's political engagement reveals important group-based differences emerging in young people's citizenship norms: between the dutiful allegiance to formal politics and a more personalised, self-actualising preference for online, discursive forms of political engagement and organising. The ways in which political information is broadcast, shared and talked about on social media by engaged young people demonstrate the importance of communicative forms of action for the future of political engagement and connective action.  相似文献   
24.
Urban Ecosystems - The development of urban areas imposes challenges that wildlife must adapt to in order to persist in these new habitats. One of the greatest changes brought by urbanization has...  相似文献   
25.
ABSTRACT

The cost and time of pharmaceutical drug development continue to grow at rates that many say are unsustainable. These trends have enormous impact on what treatments get to patients, when they get them and how they are used. The statistical framework for supporting decisions in regulated clinical development of new medicines has followed a traditional path of frequentist methodology. Trials using hypothesis tests of “no treatment effect” are done routinely, and the p-value < 0.05 is often the determinant of what constitutes a “successful” trial. Many drugs fail in clinical development, adding to the cost of new medicines, and some evidence points blame at the deficiencies of the frequentist paradigm. An unknown number effective medicines may have been abandoned because trials were declared “unsuccessful” due to a p-value exceeding 0.05. Recently, the Bayesian paradigm has shown utility in the clinical drug development process for its probability-based inference. We argue for a Bayesian approach that employs data from other trials as a “prior” for Phase 3 trials so that synthesized evidence across trials can be utilized to compute probability statements that are valuable for understanding the magnitude of treatment effect. Such a Bayesian paradigm provides a promising framework for improving statistical inference and regulatory decision making.  相似文献   
26.
27.
28.
This article analyzes the development prospects and problems for the Eurasian Economic Union (EAEU). It examines issues of integration within the EAEU, as well as interactions with other countries, both CIS (Commonwealth of Independent States) and non-CIS. The main problem of integration within the EAEU is the dominance of redistributive motives over productive ones. This article assesses the extent of Russian oil and gas transfers to EAEU partners and the impact of tax maneuvers on their size. It shows that the creation of mechanisms for redistributing profits within the EAEU will allow a positive economic effect to materialize from free trade agreements with non-CIS countries. The article assesses the risks for the EAEU related to Russia’s introduction of a unilateral ban on food imports from countries on the sanctions list and to the possible establishment of tariffs on trade with Ukraine.  相似文献   
29.
The longstanding focus of elite athletes on top sports entails disadvantages hampering their later entry to the world of work. In order to successfully contribute their outstanding personality traits to a later job, athletes are thus particularly required to care for their employability. Contributing to this, the author carried out a competency balancing with top athletes. This coaching method significantly decreased the athletes’ need for self-information. Evaluation further showed indications of increased clarity and certainty of occupational goals as well as work satisfaction.  相似文献   
30.
Understanding the risk of biological invasions associated with particular transport pathways and source regions is critical for implementing effective biosecurity management. This may require both a model for physical connectedness between regions, and a measure of environmental similarity, so as to quantify the potential for a species to be transported from a given region and to survive at a destination region. We present an analysis of integrated biosecurity risk into Australia, based on flights and shipping data from each global geopolitical region, and an adaptation of the “range bagging” method to determine environmental matching between regions. Here, we describe global patterns of environmental matching and highlight those regions with many physical connections. We classify patterns of global invasion risk (high to low) into Australian states and territories. We validate our analysis by comparison with global presence data for 844 phytophagous insect pest species, and produce a list of high‐risk species not previously known to be present in Australia. We determined that, of the insect pest species used for validation, the species most likely to be present in Australia were those also present in geopolitical regions with high transport connectivity to Australia, and those regions that were geographically close, and had similar environments.  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