全文获取类型
收费全文 | 8637篇 |
免费 | 185篇 |
专业分类
管理学 | 1295篇 |
民族学 | 42篇 |
人口学 | 847篇 |
丛书文集 | 26篇 |
理论方法论 | 656篇 |
综合类 | 116篇 |
社会学 | 3710篇 |
统计学 | 2130篇 |
出版年
2023年 | 56篇 |
2020年 | 142篇 |
2019年 | 183篇 |
2018年 | 258篇 |
2017年 | 342篇 |
2016年 | 234篇 |
2015年 | 161篇 |
2014年 | 230篇 |
2013年 | 1452篇 |
2012年 | 288篇 |
2011年 | 263篇 |
2010年 | 211篇 |
2009年 | 193篇 |
2008年 | 176篇 |
2007年 | 199篇 |
2006年 | 181篇 |
2005年 | 175篇 |
2004年 | 154篇 |
2003年 | 150篇 |
2002年 | 156篇 |
2001年 | 205篇 |
2000年 | 203篇 |
1999年 | 180篇 |
1998年 | 135篇 |
1997年 | 132篇 |
1996年 | 129篇 |
1995年 | 109篇 |
1994年 | 106篇 |
1993年 | 101篇 |
1992年 | 141篇 |
1991年 | 121篇 |
1990年 | 120篇 |
1989年 | 118篇 |
1988年 | 100篇 |
1987年 | 90篇 |
1986年 | 95篇 |
1985年 | 110篇 |
1984年 | 114篇 |
1983年 | 125篇 |
1982年 | 102篇 |
1981年 | 90篇 |
1980年 | 88篇 |
1979年 | 94篇 |
1978年 | 91篇 |
1977年 | 80篇 |
1976年 | 67篇 |
1975年 | 67篇 |
1974年 | 58篇 |
1973年 | 58篇 |
1971年 | 50篇 |
排序方式: 共有8822条查询结果,搜索用时 0 毫秒
21.
Craig H. Mallinckrodt John G. Watkin Geert Molenberghs Raymond J. Carroll 《Pharmaceutical statistics》2004,3(3):161-169
Missing data, and the bias they can cause, are an almost ever‐present concern in clinical trials. The last observation carried forward (LOCF) approach has been frequently utilized to handle missing data in clinical trials, and is often specified in conjunction with analysis of variance (LOCF ANOVA) for the primary analysis. Considerable advances in statistical methodology, and in our ability to implement these methods, have been made in recent years. Likelihood‐based, mixed‐effects model approaches implemented under the missing at random (MAR) framework are now easy to implement, and are commonly used to analyse clinical trial data. Furthermore, such approaches are more robust to the biases from missing data, and provide better control of Type I and Type II errors than LOCF ANOVA. Empirical research and analytic proof have demonstrated that the behaviour of LOCF is uncertain, and in many situations it has not been conservative. Using LOCF as a composite measure of safety, tolerability and efficacy can lead to erroneous conclusions regarding the effectiveness of a drug. This approach also violates the fundamental basis of statistics as it involves testing an outcome that is not a physical parameter of the population, but rather a quantity that can be influenced by investigator behaviour, trial design, etc. Practice should shift away from using LOCF ANOVA as the primary analysis and focus on likelihood‐based, mixed‐effects model approaches developed under the MAR framework, with missing not at random methods used to assess robustness of the primary analysis. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
22.
Bias Correction in the Dynamic Panel Data Model with a Nonscalar Disturbance Covariance Matrix 总被引:1,自引:0,他引:1
Maurice J. G. Bun 《Econometric Reviews》2003,22(1):29-58
Approximation formulae are developed for the bias of ordinary and generalized Least Squares Dummy Variable (LSDV) estimators in dynamic panel data models. Results from Kiviet [Kiviet, J. F. (1995), on bias, inconsistency, and efficiency of various estimators in dynamic panel data models, J. Econometrics68:53-78; Kiviet, J. F. (1999), Expectations of expansions for estimators in a dynamic panel data model: some results for weakly exogenous regressors, In: Hsiao, C., Lahiri, K., Lee, L-F., Pesaran, M. H., eds., Analysis of Panels and Limited Dependent Variables, Cambridge: Cambridge University Press, pp. 199-225] are extended to higher-order dynamic panel data models with general covariance structure. The focus is on estimation of both short- and long-run coefficients. The results show that proper modelling of the disturbance covariance structure is indispensable. The bias approximations are used to construct bias corrected estimators which are then applied to quarterly data from 14 European Union countries. Money demand functions for M1, M2 and M3 are estimated for the EU area as a whole for the period 1991: I-1995: IV. Significant spillovers between countries are found reflecting the dependence of domestic money demand on foreign developments. The empirical results show that in general plausible long-run effects are obtained by the bias corrected estimators. Moreover, finite sample bias, although of moderate magnitude, is present underlining the importance of more refined estimation techniques. Also the efficiency gains by exploiting the heteroscedasticity and cross-correlation patterns between countries are sometimes considerable. 相似文献
23.
24.
25.
In our zeal to deal with alcohol and drug abuse, we may have a distorted picture of what the majority of college students actually think about alcohol and drug use. Students in this study done at a public university located in the Deep South report being generally intolerant of substance abuse. 相似文献
26.
27.
Anthony G. Pakes Ravindra Khattree 《Australian & New Zealand Journal of Statistics》1992,34(2):307-322
A positive random variable X with a finite mean has an induced length-biased law represented by Y, and Y is stochastically larger than X. An independent uniform random contraction of Y, UY, has the same law as X if and only if the latter is exponential. This property is extended to non-uniform contractions and a more general notion of length-biasing. The distributional equality of X and W leads to a functional equation for the moment function of X, which has either Infinitely many solutions or none. When U is constant, X can have a log-normal law, but it can also have laws with the same moment sequence as this log-nod law. The case where U has a certain beta, or generalized beta, law give t3 characterizations of generalized gamma laws, or to products of independent copies of them. This occurs even when these laws are not determined by their moment sequences. 相似文献
28.
Suzanne T. Ortega David R. Johnson Peter G. Beeson Betty J. Craft 《Rural sociology》1994,59(4):598-619
Abstract This paper examines rural/urban differences and trends in mental health during the farm crisis of the 1980s in a large panel sample from a midwestern state. A community research perspective, which attributes differences to life styles, culture, and community context, is contrasted with an economic stress perspective, which focuses on individual differences in economic circumstances as determinants of rural-urban differences in mental health. Survey samples from 1981, 1986, and 1989 are used to examine differences among seven categories of community type. Multiple regression analysis of the trend and panel data provide support for both the individual economic distress and community context models. 相似文献
29.
The problem of estimating the value of an x variable for a given proportion of an observed value of the y variable is consdered for a non-linear model. Asymptotic confidence limits are obtained and an application of the method is illustrated witreal data. 相似文献
30.
The present studies examined children's and adults' preferences for gender- or age-based categorization using similarity and inductive inference tasks. Four-year-olds, 6-year-olds, and adults looked at pictures of people and decided which of two was more like a target (similarity condition) or which shared a novel age- or gender-related property with the target (inference condition). Age or gender-based matches were possible. The results are consistent with previous findings that gender-based classification decreases with age. However, they also demonstrate that children use gender more for judging similarity than for making inferences about novel properties. Distinct patterns emerge from the two tasks: 6-year-olds and adults in both conditions categorize more by age than gender; 4-year-olds categorize by gender more than age in the similarity task, but by age more in the induction task. Only adults differentiated by property in the inference condition. These findings suggest that the salience of gender categories cannot entirely be attributed to their inductive potential. Gender has a salience beyond what would be predicted by its power for directing novel generalizations. 相似文献