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   29863篇
  免费   1227篇
  国内免费   17篇
  2020年   338篇
  2019年   479篇
  2018年   619篇
  2017年   590篇
  2016年   650篇
  2015年   439篇
  2014年   613篇
  2013年   2824篇
  2012年   1054篇
  2011年   1133篇
  2010年   671篇
  2009年   721篇
  2008年   981篇
  2007年   997篇
  2006年   989篇
  2005年   846篇
  2004年   836篇
  2003年   831篇
  2002年   813篇
  2001年   705篇
  2000年   734篇
  1999年   561篇
  1998年   399篇
  1997年   362篇
  1996年   363篇
  1995年   332篇
  1994年   301篇
  1993年   291篇
  1992年   422篇
  1991年   432篇
  1990年   433篇
  1989年   394篇
  1988年   359篇
  1987年   357篇
  1986年   370篇
  1985年   424篇
  1984年   351篇
  1983年   345篇
  1982年   283篇
  1981年   289篇
  1980年   277篇
  1979年   361篇
  1978年   333篇
  1977年   259篇
  1975年   312篇
  1974年   346篇
  1973年   350篇
  1972年   282篇
  1968年   276篇
  1967年   268篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
The significance of a helicopter patrol procedure directed toward prevention of home burglaries was evaluated from experimental and cost-benefit perspectives. The helicopter patrolled one city zone from 9 a.m. to 5 p.m. for two 12-day periods. Each 12-day period was separated by a baseline period in which only normal patrol-car levels were maintained. Significantly reduced burglary levels during the intervention periods, compared to baseline periods, documented the experimental significance of the helicopter procedure. The cash costs of implementing the patrol procedure were compared to two estimates of the resulting cash benefits. This latter cost-benefit analysis was supplemented by a discussion of the intangible costs and benefits of the helicopter procedure. Taken together, these analyses documented that the marginal costs of the helicopter intervention were exceeded by all estimates of benefits.  相似文献   
992.
The current studies were designed to investigate the influence of variations in type of school setting on the development of role-taking skills and ethnic identity. We were interested in groups of school children in grades 1 to 5 inclusive from three different types of language programs: (1) instruction in the native language (English in this case); (2) total instruction in a second language (French); and (3) partial instruction in a second language (French). All children were native-English speaking, and came from perdominantly middle class families with monolingual English-speaking parents. The children from each program were equated at each grade level on age, and verbal and non-verbal I.Q. It was expected that (1) children in the second language programs would develop identity with their native language reference group later and less consistently than children in the native language programs; because (2) the second language children would identify more with the second language ethnic group; (3) the second language children would be able to understand at an earlier grade level than the native language group the principle of reciprocity in role-taking; and (4) these difference would be more pronounced for the totally than for the partially immersed second language children. The children were required to rate a number of ethnic dolls on a 20 point rating scale according to (1) how much each would be desired as a personal friend, (2) how much each would be desired as a friend for a member of another specific ethnic group, and (3) how similar each doll was to the child. The results indicated general support for hypotheses (1), (2) and (4), particularly among the primary school samples (1, 2), but a lack of support for hypothesis (3). These results demonstrate the influence of socio-cultural factors on the development of ethnic identity and ethnic role-taking skills.  相似文献   
993.
Four normal and four deviant children aged four-to-six years were taught to judge the quality of their academic work in a preschool classroom, and to prompt or cue their teachers to comment about the quality of that work. When these skills did not generalize spontaneously to other teachers in concurrent natural situations, generalized responding was taught by the experimenter, in multiple-baseline design across subjects. This generalization programming enabled the children to contact a sometimes dormant, but readily available natural community of teacher praise and reinforcement, i.e., to recruit an increase in cued praise and schedules of praise for their good work. These behaviors may be important to young children who find themselves bereft of attention in classrooms.  相似文献   
994.
The presence of a functional relationship between the ingestion of artificial food colors and an increase in the frequency and/or duration of selected behaviors that are representative of the hyperactive behavior syndrome was experimentally investigated. Two eight-year-old females, who had been on the Feingold K-P diet for a minimum of 11 months, were the subjects studied. The experimental design was a variation of the BAB design, with double-blind conditions. This design allowed an experimental analysis of the placebo phases as well as challenge phases. Data were obtained by trained observers on Out of Seat, On Task, and Physically Aggressive behaviors, as they occurred in the subjects' regular class setting. Results indicated (a) the existence of a functional relationship between the ingestion of artificial food colors and an increase in both the duration and frequency of hyperactive children.  相似文献   
995.
An experiment was conducted to test the proposition that rewards undermine or enhance intrinsic interest in a task to the extent that individuals interpret their behavior as being motivated by the reward. It was predicted that when subjects were denied the opportunity to develop and confirm this attribution, rewards would not produce an undermining effect, but rather would enhance dispositions and behavior. Subjects were recruited to evaluate a new sugar-free soft drink. Two levels of incentives (reward-no reward), two levels of examination (opportunity-no opportunity), and three levels of outcome (good-neutral-poor) were employed. The results support the prediction that an incentive's effect depends on the examination opportunity. In the examination condition, rewarded subjects attributed their behavior more to external factors than did unrewarded subjects, but gave more negative product evaluations only after tasting it. In the no examination condition, there were no differences in the attributions made by rewarded and unrewarded subjects, and rewarded subjects were more positively disposed toward the product both before and after tasting it. These results are explained as a consequence of two properties of rewards, enhancement through reinforcement and undermining through discounting, and of hypothesis-testing processes.  相似文献   
996.
Temporal control of behavior: schedule interactions   总被引:1,自引:1,他引:0       下载免费PDF全文
In Experiment I the response that terminated the postreinforcement pauses occurring under a fixed-interval 60-second schedule was reinforced, if the pause duration exceeded 30 seconds. The percentage of such pauses, rather than increasing, decreased. There were complex effects on the discriminative control of the pause by the reinforcer terminating the previous fixed interval, depending on whether the fixed interval and the added reinforcer were the same or different. In Experiments II(a) and II(b), each reinforcement initiated an alternative fixed-interval interresponse-time-greater-than-t-sec schedule, the schedule values being systematically varied. When the response following a pause exceeding a given duration was reinforced, fewer such pauses occurred than when they were not reinforced, i.e., on the comparable simple fixed-interval schedule. There was no systematic relationship between mean interrinforcement interval and duration of the postreinforcement pause. The pause duration initiated by reinforcement was directly related to the dependency controlling the shortest pause at that time, regardless of changes in mean interreinforcement interval.  相似文献   
997.
Following initial histories under a schedule of electric shock postponement, lever pressing in squirrel monkeys was maintained under fixed-interval and fixed-time schedules of electric shock presentation. No difference in either rate or pattern of responding was obtained when these schedules were presented as components of a multiple schedule. When they were presented singly for long periods of time, the fixed-interval schedule consistently maintained a higher response rate than the fixed-time schedule. The pattern of responding under both schedules was similar, typically consisting of a pause at the beginning of each interval followed by either a steady or a positively accelerating rate of responding. The results suggest that the response-shock dependency is of critical importance in the maintenance of high rates of responding under schedules of electric shock presentation, and support the general view that such responding may be conceptualized as operant behavior under control of many of the same variables that control responding under comparable schedules of food or water reinforcement.  相似文献   
998.
999.
1000.
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