全文获取类型
收费全文 | 4030篇 |
免费 | 475篇 |
国内免费 | 172篇 |
专业分类
4677篇 |
出版年
2024年 | 25篇 |
2023年 | 117篇 |
2022年 | 75篇 |
2021年 | 135篇 |
2020年 | 221篇 |
2019年 | 232篇 |
2018年 | 184篇 |
2017年 | 212篇 |
2016年 | 230篇 |
2015年 | 161篇 |
2014年 | 171篇 |
2013年 | 501篇 |
2012年 | 122篇 |
2011年 | 156篇 |
2010年 | 101篇 |
2009年 | 160篇 |
2008年 | 161篇 |
2007年 | 158篇 |
2006年 | 148篇 |
2005年 | 144篇 |
2004年 | 105篇 |
2003年 | 102篇 |
2002年 | 103篇 |
2001年 | 99篇 |
2000年 | 79篇 |
1999年 | 86篇 |
1998年 | 61篇 |
1997年 | 48篇 |
1996年 | 51篇 |
1995年 | 49篇 |
1994年 | 44篇 |
1993年 | 51篇 |
1992年 | 39篇 |
1991年 | 39篇 |
1990年 | 42篇 |
1989年 | 23篇 |
1988年 | 27篇 |
1987年 | 23篇 |
1986年 | 20篇 |
1985年 | 19篇 |
1984年 | 14篇 |
1983年 | 10篇 |
1982年 | 17篇 |
1981年 | 11篇 |
1980年 | 16篇 |
1979年 | 16篇 |
1978年 | 28篇 |
1977年 | 19篇 |
1976年 | 17篇 |
1975年 | 3篇 |
排序方式: 共有4677条查询结果,搜索用时 15 毫秒
101.
A community education program, to develop a variety of performance competencies in large numbers of neighborhood residents, requires a technology for preparing learning units administerable by community members themselves. The effects of a writing manual, designed to teach nonprofessionals to prepare such instructional packages, were analyzed in two experiments. Experiment I employed a multiple-baseline design across three university student trainees. The results showed that appropriate program writing increased by 75% after completion of the manual. The results of Experiment II, with two low-income neighborhood residents serving as trainees, showed that packages produced by trained writers resulted in a greater increase in skill activities than sets of training stimuli produced by untrained writers. 相似文献
102.
Time-series analysis in operant research 总被引:1,自引:0,他引:1
A time-series method is presented, nontechnically, for analysis of data generated in individual-subject operant studies, and is recommended as a supplement to visual analysis of behavior change in reversal or multiple-baseline experiments. The method can be used to identify three kinds of statistically significant behavior change: (a) changes in score levels from one experimental phase to another, (b) reliable upward or downward trends in scores, and (c) changes in trends between phases. The detection of, and reliance on, serial dependency (autocorrelation among temporally adjacent scores) in individual-subject behavioral scores is emphasized. Examples of published data from the operant literature are used to illustrate the time-series method. 相似文献
103.
Tucker has outlined an application of principal components analysis to a set of learning curves, for the purpose of identifying meaningful dimensions of individual differences in learning tasks. Since the principal components are defined in terms of a statistical criterion (maximum variance accounted for) rather than a substantive one, it is typically desirable to rotate the components to a more interpretable orientation. Simple structure is not a particularly appealing consideration for such a rotation; it is more reasonable to believe that any meaningful factor should form a (locally) smooth curve when the component loadings are plotted against trial number. Accordingly, this paper develops a procedure for transforming an arbitrary set of component reference curves to a new set which are mutually orthogonal and, subject to orthogonality, are as smooth as possible in a well defined (least squares) sense. Potential applications to learning data, electrophysiological responses, and growth data are indicated.Portions of this research were supported by the National Research Council of Canada, Grant A8615 to the second author. We thank Jagdeth Sheth for supplying his raw data. 相似文献
104.
Anders Christoffersson 《Psychometrika》1977,42(3):433-438
A two-step weighted least squares estimator for multiple factor analysis of dichotomized variables is discussed. The estimator is based on the first and second order joint probabilities. Asymptotic standard errors and a model test are obtained by applying the Jackknife procedure. 相似文献
105.
Latent roots of random data correlation matrices with squared multiple correlations on the diagonal: A monte carlo study 总被引:1,自引:0,他引:1
In order to make the parallel analysis criterion for determining the number of factors easy to use, regression equations for predicting the logarithms of the latent roots of random correlation matrices, with squared multiple correlations on the diagonal, are presented. The correlation matrices were derived from distributions of normally distributed random numbers. The independent variables are log (N–1) and log {[n(n–1)/2]–[(i–1)n]}, whereN is the number of observations;n, the number of variables; andi, the ordinal position of the eigenvalue. The results were excellent, with multiple correlation coefficients ranging from .9948 to .9992.This research was supported by the Office of Naval Research under Contract N00014-67-A-0305-0012, Lloyd G. Humphreys, principal investigator, and by the Department of Computer Science of which Richard G. Montanelli, Jr., is a member. 相似文献
106.
107.
Dr. Stanley A. Mulaik 《Psychometrika》1976,41(2):249-262
Guttman's index of indeterminacy (22 – 1) measures the potential amount of uncertainty in picking the right alternative interpretation for a factor. When alternative solutions for a factor are equally likely to be correct, then the squared multiple correlation 2 for predicting the factor from the observed variables is the average correlation
AB
between independently selected alternative solutionsA andB, while var (
AB
)=(1 – 2)2/s, wheres is the dimensionality of the space in which unpredicted components of alternative solutions are to be found. When alternative solutions for the factor are not equally likely to be chosen, 2 is the lower bound for E(
AB
); however, E(
AB
) need not be a modal value in the distribution of
AB
. Guttman's index and E(
AB
) measure different aspects of the same indeterminacy problem. 相似文献
108.
In the last few years, a number of asymptotic results for the distribution of unrotated and rotated factor loadings have been given. This paper investigates the validity of some of these results based on simulation techniques. In particular, it looks at principal component extraction and quartimax rotation on a problem with 13 variables. The indication is that the asymptotic results are quite good. 相似文献
109.
A highly popular method for examining the stability of a data clustering is to split the data into two parts, cluster the observations in Part A, assign the objects in Part B to their nearest centroid in Part A, and then independently cluster the Part B objects. One then examines how close the two partitions are (say, by the Rand measure). Another proposal is to split the data into k parts, and see how their centroids cluster. By means of synthetic data analyses, we demonstrate that these approaches fail to identify the appropriate number of clusters, particularly as sample size becomes large and the variables exhibit higher correlations.The authors express their thanks to the Sol C. Snider Entrepreneurial Center, Wharton School, for support of this project. 相似文献
110.