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   40166篇
  免费   1638篇
  国内免费   23篇
  2020年   407篇
  2019年   455篇
  2018年   664篇
  2017年   699篇
  2016年   709篇
  2015年   532篇
  2014年   632篇
  2013年   3027篇
  2012年   1121篇
  2011年   1238篇
  2010年   783篇
  2009年   720篇
  2008年   1050篇
  2007年   979篇
  2006年   901篇
  2005年   777篇
  2004年   766篇
  2003年   757篇
  2002年   783篇
  2001年   1276篇
  2000年   1261篇
  1999年   917篇
  1998年   425篇
  1997年   430篇
  1996年   397篇
  1992年   800篇
  1991年   748篇
  1990年   755篇
  1989年   719篇
  1988年   710篇
  1987年   653篇
  1986年   718篇
  1985年   697篇
  1984年   581篇
  1983年   516篇
  1981年   378篇
  1979年   574篇
  1978年   471篇
  1977年   396篇
  1976年   403篇
  1975年   508篇
  1974年   643篇
  1973年   638篇
  1972年   528篇
  1971年   522篇
  1970年   469篇
  1969年   534篇
  1968年   620篇
  1967年   546篇
  1966年   573篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
972.
Squirrel monkeys, initially trained under a schedule of electric shock postponement and then under fixed-interval schedules of electric shock presentation, were studied under multiple fixed-interval fixed-ratio and under fixed-ratio schedules of shock presentation. Under the fixed-interval (10-min) component of the multiple schedule, a pause was followed by a gradual increase in responding to a rate maintained until shock presentation; under the fixed-ratio (3-, 10-, or 30-response) component of the multiple schedule, a brief pause was typically followed by a relatively high and uniform rate of responding until shock was presented. When the 60-sec timeout periods, which usually followed shock presentation, were eliminated from the multiple schedule for one monkey, responding was only transiently affected. In the one monkey studied, responding was maintained under a fixed-ratio schedule alone (with timeout periods), but rates of responding were lower than under the fixed-ratio component of the multiple schedule. Characteristic patterns of responding, similar to those engendered under schedules of food presentation or shock termination, can be maintained under fixed-ratio schedules of shock presentation; further, patterns of responding can be controlled by discriminative stimuli in multiple schedules.  相似文献   
973.
Two-key concurrent responding was maintained for three pigeons by a single variable-interval 1-minute schedule of reinforcement in conjunction with a random number generator that assigned feeder operations between keys with equal probability. The duration of blackouts was varied between keys when each response initiated a blackout, and grain arranged by the variable-interval schedule was automatically presented after a blackout (Exp. I). In Exp. II every key peck, except for those that produced grain, initiated a blackout, and grain was dependent upon a response following a blackout. For each pigeon in Exp. I and for one pigeon in Exp. II, the relative frequency of responding on a key approximated, i.e., matched, the relative reciprocal of the duration of the blackout interval on that key. In a third experiment, blackouts scheduled on a variable-interval were of equal duration on the two keys. For one key, grain automatically followed each blackout; for the other key, grain was dependent upon a response and never followed a blackout. The relative frequency of responding on the former key, i.e., the delay key, better approximated the negative exponential function obtained by Chung (1965) than the matching function predicted by Chung and Herrnstein (1967).  相似文献   
974.
Some punishing effects of response-force   总被引:1,自引:1,他引:0       下载免费PDF全文
The present experiment explored the punishing effect of different response-force requirements by means of a two-operant design analogous to a two-component chain schedule. The first component of the chain required a lever pull through 0.25 in. (0.64 cm) at 1 lb (4.45 N) of force. The second component required a lever pull through an additional 0.75 in. (1.90 cm) with the force varied between sessions from 1 lb to 50 lb (4.45 N to 223 N). Completion of the second component of the chain was reinforced after variable intervals averaging 1 min. The average rate of first-component response decreased as the force requirement for second-component responses was increased. This rate reduction did not appear to be due to increased response duration, “fatigue”, or differing rates of reinforcement. If the force requirement for the second-component response is viewed as a consequence for the first-component response, then the results of the experiment show that a high force requirement is a punisher.  相似文献   
975.
Food-deprived pigeons responded under a 10-min fixed-interval schedule of food presentation. During even-numbered minutes of the schedule, the discriminative stimuli were the same as those present when food was delivered. During odd-numbered minutes there was either a change in keylight color or a change in overhead illumination, either for the entire duration of the odd-numbered minutes, or for 3-sec after each response. Responding during even-numbered minutes showed the usual pattern of positive acceleration; responding during odd-numbered minutes was similarly graded, but rates were much lower. The response-rate-increasing effects of amobarbital were inversely related to control rates of responding for both even- and odd-numbered minutes. However, when the stimulus change during odd-numbered minutes was either keylight color or a change from a darkened to a brightly illuminated chamber, increases in responding were considerably less than predicted on the basis of the effects on responding during even-numbered minutes. When the stimulus change was from a darkened to a dimly illuminated chamber, control rates of responding changed little, but increases in responding during odd-numbered minutes after amobarbital were considerably greater, and of the approximate order expected on the basis of control rate.  相似文献   
976.
977.
978.
979.
980.
The impact of professional negotiations on the current educational scene is examined and related to clarification of the school counselor role. Role confusion continues in the school situation, and negotiations may well be the way to bring about a change in the status quo. Negotiations for counselors are explored from the standpoints of dimensions of negotiations, implementation of negotiations, and attitude of professional associations. Conclusions are that negotiations have significant implications for counselor role delineation.  相似文献   
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