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   76227篇
  免费   2336篇
  国内免费   32篇
  78595篇
  2020年   695篇
  2019年   838篇
  2018年   4330篇
  2017年   3663篇
  2016年   3297篇
  2015年   1052篇
  2014年   1143篇
  2013年   5115篇
  2012年   2403篇
  2011年   4236篇
  2010年   3543篇
  2009年   2574篇
  2008年   3389篇
  2007年   3772篇
  2006年   1646篇
  2005年   1707篇
  2004年   1624篇
  2003年   1439篇
  2002年   1441篇
  2001年   1879篇
  2000年   1757篇
  1999年   1376篇
  1998年   764篇
  1997年   674篇
  1996年   600篇
  1995年   580篇
  1994年   558篇
  1993年   583篇
  1992年   1081篇
  1991年   1019篇
  1990年   1000篇
  1989年   884篇
  1988年   852篇
  1987年   850篇
  1986年   855篇
  1985年   913篇
  1984年   719篇
  1983年   635篇
  1982年   520篇
  1979年   703篇
  1978年   539篇
  1976年   499篇
  1975年   633篇
  1974年   671篇
  1973年   628篇
  1972年   560篇
  1971年   503篇
  1968年   573篇
  1967年   561篇
  1966年   508篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
The vocationally-indecisive individual presents a major counselling problem. The theory and research behind career indecision is discussed and a counselling approach based on identity formation is outlined. Four identity statuses — Identity Achievements, Foreclosures, Identity Diffusions, and Moratoriums — are described and counselling approaches for each are explored.  相似文献   
172.
We explored what kind of information is acquired when amnesic patients are able to exhibit significant retention on tests of cued recall and recognition memory. Amnesic patients and control subjects attempted to learn sets of sentences. Memory for the last word in each sentence was tested after 1 hr in the case of the amnesic patients, or after 1 to 2 weeks in the case of (delayed) control subjects. Amnesic patients and (delayed) control subjects performed at similar levels on tests of cued recall and recognition memory. Amnesic patients were just as confident of their correct answers as were control subjects. However, amnesic patients were no more disadvantaged than control subjects when they were cued indirectly by presenting paraphrases of the original sentences. These findings demonstrate that the residual knowledge retained by amnesic patients can be as flexible, as accessible to indirect cues, and as available to awareness as the knowledge retained by (delayed) control subjects.  相似文献   
173.
Correlates of responses to two potential hazards   总被引:2,自引:0,他引:2  
  相似文献   
174.
175.
Three severely mentally retarded adolescents were studied under discrete-trial procedures in which a choice was arranged between edible reinforcers that differed in magnitude and, in some conditions, delay. In the absence of delays the larger reinforcer was consistently chosen. Under conditions in which the smaller reinforcer was not delayed, increasing the delay to delivery of the larger reinforcer decreased the percentage of trials in which that reinforcer was chosen. All subjects directed the majority of choice responses to the smaller reinforcer when the larger reinforcer was sufficiently delayed, although the value at which this occurred differed across subjects. Under conditions in which the larger reinforcer initially was sufficiently delayed to result in preference for the smaller one, progressively increasing in 5-s increments the delay to both reinforcers increased percentage of trials with the larger reinforcer chosen. At sufficiently long delays, 2 of the subjects consistently chose the larger, but more delayed, reinforcer, and the 3rd subject chose that reinforcer on half of the trials. These results are consistent with the findings of prior studies in which adult humans responded to terminate noise and pigeons responded to produce food.  相似文献   
176.
In two experiments, key-peck responding of pigeons was compared under variable-interval schedules that arranged immediate reinforcement and ones that arranged unsignaled delays of reinforcement. Responses during the nominal unsignaled delay periods had no effect on the reinforcer presentations. In Experiment 1, the unsignaled delays were studied using variable-interval schedules as baselines. Relative to the immediate reinforcement condition, 0.5-s unsignaled delays decreased the duration of the reinforced interresponse times and increased the overall frequency of short (<0.5-s) interresponse times. Longer, 5.0-s unsignaled delays increased the duration of the reinforced interresponse times and decreased the overall frequency of the short interresponse times. In Experiment 2, similar effects to those of Experiment 1 were obtained when the 0.5-s unsignaled delays were imposed upon a baseline schedule that explicitly arranged reinforcement of short interresponse times and therefore already generated a large number of short interresponse times. The results support earlier suggestions that the unsignaled 0.5-s delays change the functional response unit from a single key peck to a multiple key-peck unit. These findings are discussed in terms of the mechanisms by which contingencies control response structure in the absence of specific structural requirements.  相似文献   
177.
Effects of alternative reinforcement sources: A reevaluation   总被引:3,自引:3,他引:0       下载免费PDF全文
The effects of two alternative sources of food delivery on the key-peck responding of pigeons were examined. Pecking was maintained by a variable-interval 3-min schedule. In the presence of this schedule in different conditions, either a variable-time 3-min schedule delivering food independently of responding or an equivalent schedule that required a minimum 2-s pause between a key peck and food delivery (a differential-reinforcement-of-other-behavior schedule) was added. The differential-reinforcement-of-other-behavior schedule reduced response rates more than did the variable-time schedule in most instances. The delay between a key peck and the next reinforcer consistently was longer under the differential-reinforcement-of-other-behavior schedule than under the variable-time schedule. Response rates and median delay between responses and reinforcers were negatively correlated. These results contradict earlier conclusions about the behavioral effects of alternative reinforcement. They suggest that an interpretation in terms of response–reinforcer contiguity is consistent with the data.  相似文献   
178.
179.
180.
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