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   3000篇
  免费   114篇
  国内免费   1篇
管理学   419篇
民族学   9篇
人口学   262篇
丛书文集   18篇
理论方法论   345篇
综合类   36篇
社会学   1240篇
统计学   786篇
  2023年   20篇
  2021年   19篇
  2020年   55篇
  2019年   79篇
  2018年   108篇
  2017年   120篇
  2016年   70篇
  2015年   80篇
  2014年   96篇
  2013年   607篇
  2012年   122篇
  2011年   103篇
  2010年   79篇
  2009年   64篇
  2008年   82篇
  2007年   79篇
  2006年   63篇
  2005年   59篇
  2004年   47篇
  2003年   30篇
  2002年   51篇
  2001年   61篇
  2000年   56篇
  1999年   47篇
  1998年   40篇
  1997年   41篇
  1996年   32篇
  1995年   33篇
  1994年   41篇
  1993年   36篇
  1992年   47篇
  1991年   48篇
  1990年   35篇
  1989年   34篇
  1988年   43篇
  1987年   19篇
  1986年   26篇
  1985年   38篇
  1984年   31篇
  1983年   41篇
  1982年   27篇
  1981年   23篇
  1980年   22篇
  1979年   23篇
  1978年   40篇
  1977年   20篇
  1976年   26篇
  1975年   25篇
  1974年   15篇
  1972年   14篇
排序方式: 共有3115条查询结果,搜索用时 203 毫秒
851.
852.
In this essay, I examine the problem of excessive and racially disproportionate school discipline. I begin by considering how each of the four most popular Democratic candidates in the presidential primary race as of January 2020 addresses this issue. Excessive and racially disproportionate school discipline harms students, schools, and communities, and it deepens existing racial inequalities. Each candidate promises some remedy, and all represent a step in the right direction. However, all of their proposals are shallow. To fruitfully address these issues, policymakers must consider the cultural embeddedness of school discipline, how it is implemented within complex school bureaucracies, and the underlying racial inequality that shapes school discipline. Policymakers must also draw attention to the fact that schools are, overall, safe and do not require the massive investments in security personnel and technology that draw funds away from more effective supports for students.  相似文献   
853.
Covariate adjusted regression (CAR) is a recently proposed adjustment method for regression analysis where both the response and predictors are not directly observed [?entürk, D., Müller, H.G., 2005. Covariate adjusted regression. Biometrika 92, 75–89]. The available data have been distorted by unknown functions of an observable confounding covariate. CAR provides consistent estimators for the coefficients of the regression between the variables of interest, adjusted for the confounder. We develop a broader class of partial covariate adjusted regression (PCAR) models to accommodate both distorted and undistorted (adjusted/unadjusted) predictors. The PCAR model allows for unadjusted predictors, such as age, gender and demographic variables, which are common in the analysis of biomedical and epidemiological data. The available estimation and inference procedures for CAR are shown to be invalid for the proposed PCAR model. We propose new estimators and develop new inference tools for the more general PCAR setting. In particular, we establish the asymptotic normality of the proposed estimators and propose consistent estimators of their asymptotic variances. Finite sample properties of the proposed estimators are investigated using simulation studies and the method is also illustrated with a Pima Indians diabetes data set.  相似文献   
854.
We propose an estimation method that incorporates the correlation/covariance structure between repeated measurements in covariate-adjusted regression models for distorted longitudinal data. In this distorted data setting, neither the longitudinal response nor (possibly time-varying) predictors are directly observable. The unobserved response and predictors are assumed to be distorted/contaminated by unknown functions of a common observable confounder. The proposed estimation methodology adjusts for the distortion effects both in estimation of the covariance structure and in the regression parameters using generalized least squares. The finite-sample performance of the proposed estimators is studied numerically by means of simulations. The consistency and convergence rates of the proposed estimators are also established. The proposed method is illustrated with an application to data from a longitudinal study of cognitive and social development in children.  相似文献   
855.
A major issue when proposing a new prognostic index is its generalisibility to daily clinical practice. Validation is therefore required. Most validation techniques assess whether “on average” the results obtained by the prognostic index in classifying patients in a new sample of patients are similar to the results obtained in the construction set. We introduce a new important aspect of the generalisibility of a prognostic index: the heterogeneity of the prognostic index risk group hazard ratios over different centers. If substantial variability between centers exists, the prognostic index may have no discriminatory capability in some of the centers. To model such heterogeneity, we use a frailty model including a random center effect and a random prognostic index by center interaction. Statistical inference is based on a Bayesian approach using a Laplacian approximation for the marginal posterior distribution of the variances of the random effects. We investigate different ways to summarize the information available from this marginal posterior distribution. Our approach is applied to a real bladder cancer database for which we demonstrate how to investigate and interpret heterogeneity in prognostic index effect over centers.  相似文献   
856.
In this paper, we study, by a Monte Carlo simulation, the effect of the order p of “Zhurbenko-Kolmogorov” taper on the asymptotic properties of semiparametric estimators. We show that p  =  [d + 1/2] + 1 gives the smallest variances and mean squared errors. These properties depend also on the truncation parameter m. Moreover, we study the impact of the short-memory components on the bias and variances of these estimators. We finally carry out an empirical application by using four monthly seasonally adjusted logarithm Consumer Price Index series.   相似文献   
857.
The perceived usefulness of information is an important construct for the design of management information systems. Yet an examination of existing measures of perceived usefulness shows that the instruments developed have not been validated nor has their reliability been verified. In this paper a new instrument for measuring two dimensions of perceived usefulness is developed. The results of an empirical study designed to test the reliability and construct validity of this instrument in a capital-budgeting setting are presented.  相似文献   
858.
A central principle in urban ecological theory implies that in urbanized landscapes anthropogenic drivers will dominate natural drivers in the control of soil organic carbon storage (SOC). To assess the effect of urban land-use change on the storage of SOC, we compared SOC stocks of turf grass and native cover types of two metropolitan areas (Baltimore, MD, and Denver, CO) representing climatologically distinct regions in the United States. We hypothesized that introducing turf grass and management will lead to higher SOC densities in the arid Denver area and lower densities in the mesic Baltimore area relative to native cover types. Moreover, differences between turf grass soils will be less than differences between the native soils of each metropolitan region. Within Baltimore, turf grass had almost a 2-fold higher SOC density at 0- to 1-m and 0- to 20-cm depths than in rural forest soils, whereas there were no differences with soils of urban forest remnants. Moreover, urban forest remnants had more than 70% higher SOC densities than rural forest soils. Within Denver, turf grass (>25 years of age) had more than 2-fold higher SOC densities than in shortgrass steppe soils, while having similar densities to Baltimore turf grass soils. By contrast, the native soils of Baltimore were almost 2-fold higher than the native steppe grass soils of Denver using SOC densities of remnant forests as representative of native soils in the Baltimore region. These results supported our hypothesis that turf grass systems will be similar in SOC densities across regional variations in climate, parent material, and topography. These similarities are apparently due to greater management efforts in the Denver region to offset the constraint of climate, i.e., anthropogenic factors (management supplements) overwhelmed native environmental factors that control SOC storage.  相似文献   
859.
Many public transit agencies consider increasing fares when faced with budget shortfalls. This paper analyzes the Alameda–Contra Costa (AC) Transit District's five alternative fare proposals introduced for public discussion in March 2005. The proposals combined fare hikes, base fare reductions, eliminations of free transfers, and discontinuation of periodic passes. Using the agency's 2002 on-board survey data, the study assessed the impacts of individual fare proposals on different subsets of riders and evaluated if they were equitable; and estimated potential fare revenues, using alternative price elasticities to estimate changes in ridership due to changes in price. The analysis revealed that proposals that increased the cost of transfers or eliminated unlimited-use passes produced dramatically unequal impacts on certain riders. Proposals for flat fares per ride were found to be least equitable, even when the base fare was lowered, because lower income riders, youth, and minorities made more trips and transferred more frequently than their more affluent counterparts. Proposals that maintained existing pass instruments and allowed transfers for small fees were the most favorable. The paper demonstrates the utility of on-board surveys and details an approach that could be widely used for evaluation of equity in public transit and other areas.  相似文献   
860.
This article investigates the foundations of cooperative identity and how it is constructed by the organization. More specifically, our research focuses on a financial cooperative in the simultaneously emerging and consolidating cultural sector. The originality of this article lies in the methodology used – textual analysis. We use the Economies of Worth model developed by Boltanski and Thévenot (2006 Boltanski , L. and Thévenot , L. , 2006 . On justification: economies of worth . Studies in Cultural Sociology Series Princeton : Princeton University Press . [Google Scholar]), which accounts for a plurality of legitimate forms of evaluation used in the processes of critique and justification.  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