全文获取类型
收费全文 | 18233篇 |
免费 | 1573篇 |
国内免费 | 1037篇 |
专业分类
20843篇 |
出版年
2024年 | 42篇 |
2023年 | 299篇 |
2022年 | 251篇 |
2021年 | 301篇 |
2020年 | 633篇 |
2019年 | 725篇 |
2018年 | 672篇 |
2017年 | 763篇 |
2016年 | 771篇 |
2015年 | 495篇 |
2014年 | 671篇 |
2013年 | 2100篇 |
2012年 | 399篇 |
2011年 | 483篇 |
2010年 | 392篇 |
2009年 | 594篇 |
2008年 | 792篇 |
2007年 | 836篇 |
2006年 | 791篇 |
2005年 | 669篇 |
2004年 | 574篇 |
2003年 | 494篇 |
2002年 | 464篇 |
2001年 | 291篇 |
2000年 | 268篇 |
1999年 | 228篇 |
1998年 | 183篇 |
1997年 | 155篇 |
1996年 | 124篇 |
1995年 | 119篇 |
1994年 | 111篇 |
1993年 | 86篇 |
1992年 | 67篇 |
1991年 | 47篇 |
1990年 | 48篇 |
1988年 | 40篇 |
1987年 | 26篇 |
1985年 | 372篇 |
1984年 | 416篇 |
1983年 | 344篇 |
1982年 | 449篇 |
1981年 | 441篇 |
1980年 | 443篇 |
1979年 | 394篇 |
1978年 | 444篇 |
1977年 | 350篇 |
1976年 | 353篇 |
1975年 | 272篇 |
1974年 | 278篇 |
1973年 | 236篇 |
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
861.
862.
Verbal rehearsal and selective attention in children with learning disabilities: A developmental lag
Sara G Tarver Daniel P Hallahan James M Kauffman Donald W Ball 《Journal of experimental child psychology》1976,22(3):375-385
To investigate the development of verbal rehearsal strategies and selective attention in learning disabled children, Hagen's Central-Incidental task was administered to younger learning disabled (M CA = 8.68 years) and normal (M CA = 8.62 years) boys in Experiment 1 and to intermediate (M CA = 10.18 years) and older (M CA = 13.48 years) learning disabled boys in Experiment 2. Also, in Experiment 2, an experimentally induced verbal rehearsal condition was included to determine its effects on serial recall and selective attention performance. In Experiment 1, the serial postion curve of the normals revealed both a primacy and a recency effect, whereas that of the learning disabled revealed a recency effect only. In Experiment 2, both the intermediate and the older learning disabled exhibited both primacy and recency effects under both standard and rehearsal conditions. A developmental analysis of central recall for the three learning disabled groups revealed constant age-related increases in overall central recall and in primacy recall. That the normals recalled more central, but not more incidental, information than the learning disabled in Experiment 1 suggests that the learning disabled are deficient in selective attention. Correlational findings suggest that the selective attention of the learning disabled improves with age. The results were interpreted as support for the hypothesis of a developmental lag in the learning disabled population. 相似文献
863.
M Beth Casey 《Journal of experimental child psychology》1976,22(3):468-477
Methods of increasing learning efficiency through a blocking technique were examined in young children. An experimental group of children was trained on an initial task with one relevant dimension, followed by redundancy training in which an incidental dimension also became relevant. A control group given only redundancy training was compared to this group to test how much the experimental subjects blocked or screened out the incidental dimension. In order to increase blocking, three methods were used: a preset transfer problem, an overtraining on the initial task, and a delay following training. The most important finding was increased blocking through the Preset Condition. Overtraining and Delay Conditions had no effect. In addition, more slow learners on the initial task learned about the incidental dimension than fast or intermediate learners. Also, fewer subjects given form on the initial task learned about the incidental dimension than those given color. The Combined Blocking, Delay, and Overtraining group showed partial blocking, while the Preset group demonstrated complete blocking. No developmental differences occurred. The results were interpreted using a modification of Trabasso and Bower's attention model (Attention in learning: Theory and research. New York: Wiley, 1968). 相似文献
864.
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
865.
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
866.
Robert S. Schulman 《Psychometrika》1976,41(3):329-340
Based on the test theory model for ordinal measurements proposed by Schulman and Haden, the present paper considers correlations between tests, attenuation, regressions involving true and observed scores, and prediction of test reliability.The population correlation between tests is shown to be related to the expected sample correlation for samples of sizen
1 andn
2. Errors of estimation, measurement and prediction are found to be similar to their counterparts in interval test theory, while attenuation is identical to its counterpart. The bias in estimating population reliability from sample data is compared for Kendall's tau and Spearman's rho.The author wishes to thank the referees for their helpful comments on an earlier draft of this paper, and in particular, for the suggested alternative methods of establishing some of the presented results. 相似文献
867.
The present study examined whether or not certain anorexic agents produced flavor aversions. Rats showed comparable anorexia when injected with lithium chloride, ammonium sulfate, arginine·HCl, and d-glucose. Only lithium chloride produced a flavor aversion to either a novel liquid or food. Only arginine was found to interfere with the formation or recall of an association. The effects of the other chemicals were discussed in terms of the relationship between anorexia and induced sickness. 相似文献
868.
Four hamsters received brief electric shocks contingent upon running in a wheel. The fixed interval between shocks was varied systematically from 0 to 60 sec. Time spent running was directly related to the length of the fixed interval, while running speed remained roughly constant. Running depended on the fixed interval between shocks in the same way as bar-pressing maintained by food reinforcement, despite the fact that running was not established with nor maintained by explicit reinforcement. 相似文献
869.
Two levels of confinement duration (5 or 60 sec) in either startbox or goalbox were factorially combined with presence or absence of shock during extinction of a runway escape response in a self-punitive paradigm under a spaced-trials procedure. All groups were equated for amount and temporal spacing of handling before and after each trial. Shocked rats were more resistant to extinction than nonshocked rats only when startbox confinement was short. When startbox confinement was long, shock facilitated extinction. Long goalbox confinement enhanced running speed for shocked rats, but only in the presence of shock. It was suggested that duration of startbox confinement affects strength of conditioned fear, with long confinement leading to its extinction. 相似文献
870.
Franklin Goodkin 《Learning and motivation》1976,7(3):382-393
Previous research has shown that preexposure to inescapable shock interferes with subsequent acquisition of escape responding, while pretraining with escapable shock facilitates subsequent acquisition of a different escape response. It has also been demonstrated that interference and facilitation persist when the aversive event is changed between the two phases of training. The present experiment extended these findings, showing generalized learning from an appetitive to an aversive situation. Six groups of rats received the following treatment in the presence of discriminative stimuli: One group was trained to nose press for food, a second to chain pull for food, and a third to chain pull to escape or avoid shock. Two groups received either signalled free food or inescapable shock, and a naive control group received no pretreatment. All groups were then tested in a nose-press escape-avoidance situation. The three groups with prior response training acquired responding most rapidly, and at the same rate. The naive controls acquired responding slowly, and the two groups with response-independent histories did not acquire responding during the 5 days of training. It was concluded that rats learn the relationship between responding and environmental events and that such learning strongly influences subsequent learning. 相似文献