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   20408篇
  免费   626篇
管理学   2439篇
民族学   123篇
人才学   8篇
人口学   1947篇
丛书文集   119篇
教育普及   2篇
理论方法论   1988篇
现状及发展   1篇
综合类   256篇
社会学   10285篇
统计学   3866篇
  2023年   116篇
  2022年   89篇
  2021年   128篇
  2020年   359篇
  2019年   549篇
  2018年   551篇
  2017年   760篇
  2016年   565篇
  2015年   428篇
  2014年   507篇
  2013年   3420篇
  2012年   759篇
  2011年   678篇
  2010年   542篇
  2009年   503篇
  2008年   553篇
  2007年   561篇
  2006年   520篇
  2005年   467篇
  2004年   474篇
  2003年   432篇
  2002年   425篇
  2001年   488篇
  2000年   408篇
  1999年   400篇
  1998年   334篇
  1997年   301篇
  1996年   315篇
  1995年   290篇
  1994年   288篇
  1993年   270篇
  1992年   319篇
  1991年   301篇
  1990年   272篇
  1989年   273篇
  1988年   256篇
  1987年   231篇
  1986年   230篇
  1985年   261篇
  1984年   244篇
  1983年   246篇
  1982年   187篇
  1981年   161篇
  1980年   177篇
  1979年   179篇
  1978年   151篇
  1977年   146篇
  1976年   128篇
  1975年   121篇
  1974年   101篇
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
861.
ABSTRACT

This article identifies trends in the adoption and implementation of quotas for corporate boards, an underresearched topic in political science. Corporate quotas—like legislative quotas—constitute the “fast track” to gender equality but appear more commonly in advanced democracies. These corporate quotas fall into three categories: laws covering all companies; laws covering state-owned companies only; and nonbinding (voluntary) measures in corporate governance codes. Despite on-paper differences, these corporate quotas are largely toothless. First generation corporate quotas, like first generation legislative quotas, operate symbolically. By raising the specter of stringent legislation in the long run, corporate quotas induce firms into voluntary compliance in the short run.  相似文献   
862.

Background

Previous physical activity (PA) tracking studies have examined the stability of overall PA and/or PA types, but few have investigated how specific types of sport/exercise track over the life course. The aim of this study was to determine how specific sports/exercises in midlife track and predict future sport/exercise and PA in men transitioning to old age.

Methods

Seven thousand seven hundred thirty-five men (aged 40–59?years) recruited in 1978–80 were followed up after 12, 16 and 20?years. At each wave men self-reported participation in sport/exercise. Frequent sport/exercise participants (>?1/month) reported the types of sport/exercise they engaged in. Men also reported total PA, health status, lifestyle behaviours and socio-demographic characteristics. Stability of each sport/exercise was assessed using kappa statistics and intraclass correlation coefficients. Logistic regression estimated the odds of participating in sport/exercise and being active at 20-year follow up according to specific types of sport/exercise in midlife.

Results

Three thousand three hundred eighty-four men with complete data at all waves were included in analyses. Tracking of specific sports/exercises ranged from fair to substantial, with golf being the most common and most stable. Bowls was the most frequently adopted. Odds of participating in sport/exercise and being active in old age varied according to sport/exercise types in midlife. Golf and bowls in midlife were the strongest predictors of sport/exercise participation in old age. Golf, cricket and running/jogging in midlife were among the strongest predictors of being active in old age. Compared to participating in just one sport/exercise in midlife, sampling multiple sports/exercises was more strongly associated with sport/exercise participation and being active in old age.

Conclusion

The stability of sport/exercise participation from midlife to old age varies by type. Specific sports/exercises in midlife may be more likely to predict future PA than others. However, participating in a range of sports/exercises may be optimal for preserving PA into old age.
  相似文献   
863.

Background

The increasing prevalence of obesity in sub-Saharan African women is not well understood, and black South African women in the region are particularly vulnerable. This study aimed to examine whether the relationship of socioeconomic status (SES) with changes in body mass index (BMI) and waist circumference (WC) is mediated by physical activity in ageing African women.

Methods

In a longitudinal analysis of the 518 caregivers associated with the Birth to Twenty Plus study, the role of SES associated with 10-year changes in BMI and WC was tested using structural equation modelling (SEM). The degree of mediation of moderate-vigorous physical activity (MVPA) and sitting time in this association was also assessed.

Results

The prevalence of obesity increased significantly from baseline to follow-up (p?<?0.0001). In the SEM models, baseline SES had a direct positive effect on changes in BMI (β, 95% CI, 0.02 (0.005 to 0.04), and a direct negative effect on changes in MVPA (β, 95% CI, ??3.81 (??6.92 to ??0.70). Baseline MVPA had a direct negative effect (β, 95% CI, ??0.002 (??0.003 to ??0.0003) and indirect positive effect via change in MVPA (β, 95% CI, 0.01 (0.0001 to 0.001) on change in WC.

Conclusions

Our study demonstrates the role and interaction of sociodemographic and behavioural predictors of obesity, and suggests a multifaceted approach to management of the crisis in communities of ageing urban African women.
  相似文献   
864.
The recent wave of Jews emigrating from countries of the former Soviet Union to Israel has created structural conditions for immigrant entrepreneurship. The large size of the migrant population and its spatial concentration create a demand for services and products that can be provided by immigrants. This paper investigates the factors associated with intentions to open a small business in a sample of Jewish immigrants from the countries of the former Soviet Union. It was found that intentions to open a small business are related to previous business experience, education, income, and length of residence in the country. Immigrants become interested in entrepreneurship after learning that their prospects of finding a job in their profession are meager and explain their motivation to open a small business as being to increase their income. The findings seem to support the disadvantage theory that conceptualizes entrepreneurship as an adaptive mechanism to structural barriers in the primary labor market that create an occupational closure for immigrants possessing low and middle levels of education and income.  相似文献   
865.
866.
867.
In this paper we provide three nonparametric tests of independence between continuous random variables based on the Bernstein copula distribution function and the Bernstein copula density function. The first test is constructed based on a Cramér-von Mises divergence-type functional based on the empirical Bernstein copula process. The two other tests are based on the Bernstein copula density and use Cramér-von Mises and Kullback–Leibler divergence-type functionals, respectively. Furthermore, we study the asymptotic null distribution of each of these test statistics. Finally, we consider a Monte Carlo experiment to investigate the performance of our tests. In particular we examine their size and power which we compare with those of the classical nonparametric tests that are based on the empirical distribution function.  相似文献   
868.
Generalised estimating equations (GEE) for regression problems with vector‐valued responses are examined. When the response vectors are of mixed type (e.g. continuous–binary response pairs), the GEE approach is a semiparametric alternative to full‐likelihood copula methods, and is closely related to Prentice & Zhao's mean‐covariance estimation equations approach. When the response vectors are of the same type (e.g. measurements on left and right eyes), the GEE approach can be viewed as a ‘plug‐in’ to existing methods, such as the vglm function from the state‐of‐the‐art VGAM package in R. In either scenario, the GEE approach offers asymptotically correct inferences on model parameters regardless of whether the working variance–covariance model is correctly or incorrectly specified. The finite‐sample performance of the method is assessed using simulation studies based on a burn injury dataset and a sorbinil eye trial dataset. The method is applied to data analysis examples using the same two datasets, as well as to a trivariate binary dataset on three plant species in the Hunua ranges of Auckland.  相似文献   
869.
Fractional factorial (FF) designs are no doubt the most widely used designs in experimental investigations due to their efficient use of experimental runs. One price we pay for using FF designs is, clearly, our inability to obtain estimates of some important effects (main effects or second order interactions) that are separate from estimates of other effects (usually higher order interactions). When the estimate of an effect also includes the influence of one or more other effects the effects are said to be aliased. Folding over an FF design is a method for breaking the links between aliased effects in a design. The question is, how do we define the foldover structure for asymmetric FF designs, whether regular or nonregular? How do we choose the optimal foldover plan? How do we use optimal foldover plans to construct combined designs which have better capability of estimating lower order effects? The main objective of the present paper is to provide answers to these questions. Using the new results in this paper as benchmarks, we can implement a powerful and efficient algorithm for finding optimal foldover plans which can be used to break links between aliased effects.  相似文献   
870.
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