全文获取类型
收费全文 | 62956篇 |
免费 | 2526篇 |
国内免费 | 32篇 |
出版年
2020年 | 699篇 |
2019年 | 880篇 |
2018年 | 1252篇 |
2017年 | 1273篇 |
2016年 | 1343篇 |
2015年 | 917篇 |
2014年 | 1136篇 |
2013年 | 5784篇 |
2012年 | 2018篇 |
2011年 | 2210篇 |
2010年 | 1308篇 |
2009年 | 1338篇 |
2008年 | 2028篇 |
2007年 | 1977篇 |
2006年 | 1777篇 |
2005年 | 1642篇 |
2004年 | 1612篇 |
2003年 | 1494篇 |
2002年 | 1562篇 |
2001年 | 1938篇 |
2000年 | 1802篇 |
1999年 | 1435篇 |
1998年 | 848篇 |
1997年 | 760篇 |
1996年 | 658篇 |
1995年 | 673篇 |
1994年 | 641篇 |
1993年 | 672篇 |
1992年 | 1153篇 |
1991年 | 1076篇 |
1990年 | 1066篇 |
1989年 | 962篇 |
1988年 | 914篇 |
1987年 | 916篇 |
1986年 | 904篇 |
1985年 | 986篇 |
1984年 | 837篇 |
1983年 | 745篇 |
1982年 | 639篇 |
1981年 | 579篇 |
1979年 | 763篇 |
1978年 | 642篇 |
1977年 | 553篇 |
1976年 | 586篇 |
1975年 | 713篇 |
1974年 | 757篇 |
1973年 | 689篇 |
1972年 | 608篇 |
1968年 | 598篇 |
1967年 | 581篇 |
排序方式: 共有10000条查询结果,搜索用时 453 毫秒
881.
A within-subjects comparison was made of pigeons' performance on two temporal discrimination procedures that were signaled by differently colored keylight samples. During stimulus trials, a peck on the key displaying a slanted line was reinforced following short keylight samples, and a peck on the key displaying a horizontal line was reinforced following long keylight samples, regardless of the location of the stimuli on those two choice keys. During position trials, a peck on the left key was reinforced following short keylight samples and a peck on the right key was reinforced following long keylight samples, regardless of which line stimulus appeared on the correct key. Thus, on stimulus trials, the correct choice key could not be discriminated prior to the presentation of the test stimuli, whereas on position trials, the correct choice key could be discriminated during the presentation of the sample stimulus. During Phase 1, with a 0-s delay between sample and choice stimuli, discrimination learning was faster on position trials than on stimulus trials for all 4 birds. During Phase 2, 0-, 0.5-, and 1.0-s delays produced differential loss of stimulus control under the two tasks for 2 birds. Response patterns during the delay intervals provided some evidence for differential mediation of the two delayed discriminations. These between-task differences suggest that the same processes may not mediate performance in each. 相似文献
882.
883.
884.
885.
886.
887.
888.
889.
890.
Two hundred and sixty three young adult college students responded to openended questions assessing their specific intentions, motives, and plans for having children. The most commonly stated motives for childbearing reflected a strong interest in establishing an identity and social network. Financial, marital, and emotional stability were identified as important factors influencing the timing of parenthood. Several significant sex differences were found for both motives and the timing of parenthood. These findings are discussed in terms of changing social norms regarding parenthood and changing sex role expectations.Portions of this research were presented at the Eastern Regional Psychological Association Convention in New York, April 1986. This research was funded by a grant from Trenton State College, Committee for Faculty and Institutional Research and Sabbatical Leave. 相似文献