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   46614篇
  免费   1917篇
  国内免费   18篇
  2020年   538篇
  2019年   664篇
  2018年   936篇
  2017年   982篇
  2016年   1008篇
  2015年   700篇
  2014年   854篇
  2013年   3597篇
  2012年   1527篇
  2011年   1549篇
  2010年   991篇
  2009年   921篇
  2008年   1380篇
  2007年   1361篇
  2006年   1212篇
  2005年   1068篇
  2004年   1000篇
  2003年   941篇
  2002年   974篇
  2001年   1494篇
  2000年   1424篇
  1999年   1071篇
  1998年   465篇
  1997年   443篇
  1996年   423篇
  1995年   432篇
  1992年   903篇
  1991年   831篇
  1990年   871篇
  1989年   773篇
  1988年   808篇
  1987年   747篇
  1986年   752篇
  1985年   691篇
  1984年   643篇
  1983年   577篇
  1982年   450篇
  1979年   693篇
  1978年   477篇
  1977年   428篇
  1975年   573篇
  1974年   629篇
  1973年   678篇
  1972年   528篇
  1971年   511篇
  1970年   455篇
  1969年   518篇
  1968年   620篇
  1967年   543篇
  1966年   477篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
931.
Inquiries into the longevity of illness-induced aversions (TAs) in animals are relevant to consummatory-aversion (CA) treatments of human alcoholism. The range of nausea reactions that accompanied the relapses of some alcoholics who had acquired alcohol aversions during covertsensitization (verbal aversion) alcoholism treatment has implicated CA forgetting as one probable contributor to recidivism. CA forgetting is operationalized as aversion diminution during postconditioning periods in which Ss abstain from contact with the target substance. TAs of varying strengths were induced in groups of Sprague-Dawley rats that received low, medium or high doses of the illness-inducing drug cyclophosphamide following saccharin-solution ingestion. TA retention was assessed following saccharin-free intervals of 2–40 days. Each Ss' retention interval was followed by 30 days of two-bottle preference testing, thereby additionally permitting an assessment of TA extinction following differing degrees of TA forgetting. Low-dose Ss displayed moderate strength TAs that were forgotten within 20 days and that had little resistance to extinction when testing began shortly after conditioning. Medium-dose Ss displayed stronger TAs having greater resistance to both forgetting and extinction. Unlike these low- and medium-dose TAs, high-dose TAs were impervious to aversion degradation as a result of forgetting. This finding is interpreted as supporting the attempted induction of intense nausea during covert-sensitization and chemical aversion (emetic therapy) alcoholism treatment. Other related conditioning procedures that may contribute to effective treatment are also discussed.  相似文献   
932.
In this paper we discuss a method for assessing agreement among raters who are scoring the number of times, a specified event occurs. In such cases, it seems reasonable to define agreement in terms of raters' behaviours in correctly identifying responses which have in fact occurred, and in their falsely counting responses which have not. We exploit the discrete nature of the response variable, and examine a class of models for mean response assuming an underlying Poisson distribution. Test statistics are given for deciding on the applicability of the models, and whether there is agreement with respect to correctly detecting responses, as well as with falsely scoring responses.  相似文献   
933.
The five stages of family development and their phase-specific tasks as delineated by Michael A. Solomon in an article that appeared in this journal (1973) are given dramatic representation by Virginia Woolf in her novel To the Lighthouse (1927). The novel begins with the Ramsay family system arrested at the third stage of development; and it is only after the death of Mrs. Ramsay that the remaining family members begin to attend to the phase-specific tasks of stages four and five, and family development commences.  相似文献   
934.
935.
A sentence often contains two components: a topic, which refers to a nonlinguistic object whose existence is presupposed; and a comment, which asserts some thought about this object. In addition, a sentence will often repeat (or refer back to) information that was expressed earlier in a text or conversation. The purpose of this article is to propose a single theoretical framework to describe the mechanisms that relate a sentence to its nonlinguistic environment as well as those that relate a sentence to its linguistic context. The theory developed in this article suggests that sentences can strongly influence the representation of visible nonlinguistic events and that this representation is sensitive to the distinction between presupposed and asserted information. To evaluate this theory, a sentence-picture verification priming task was developed. In this task, subjects were presented with pairs of sentence-picture displays, and were asked to verify whether or not the sentence in each display correctly applied to an accompanying picture. The relationship between pairs of sentence-picture displays was varied systematically. Across five experiments, three hypotheses were supported: (a) The processes which evaluate presupposed information and the processes which evaluate asserted information are differentially affected by nonlinguistic factors, (b) only those aspects of the picture which are referred to by the sentence are encoded for future use, and (c) coherence between successive sentences is in part a function of the referential continuity of the presupposed information.  相似文献   
936.
The relationship between reinforcer amount and daytime smoking reduction in smokers offered money for reduced afternoon breath carbon monoxide (CO) levels was examined. Twenty-three hired regular smokers with average baseline CO levels of about 30 ppm were exposed in random order to five sliding scale payment schedules that changed daily or weekly. Money was available for afternoon CO readings between 0 and 21 ppm with pay amount inversely related to the absolute CO reading obtained. Maximum pay amount for readings below 7 ppm varied among $0, $1.50, $3, $6, and $12 per day. Contingent reinforcement promoted CO and daytime cigarette reduction within individuals with the amount of behavior change related to the amount of payment available. Average CO levels decreased from 30 to 15 ppm as a function of pay amount whereas self-reported daytime cigarettes decreased from 12 to 5 per day. Average minutes of cigarette abstinence prior to the afternoon study contact increased from 62 to 319 minutes as a function of pay amount, whereas the percentage of available money earned increased from 22% to 48%. Nontargeted evening cigarette use also decreased during periods of daytime smoking reduction. The orderly effects of this contingent reinforcement intervention on daytime smoking of regular smoker volunteers suggest that this is a sensitive model for continued evaluation of factors that influence smoking reduction and cessation.  相似文献   
937.
The effects of a graduated prompting treatment procedure were analyzed in three phases of an experiment on the training and generalization of reaching-grasp responding in 2- to 4-year-old blind, severely or profoundly retarded children. In Phase 1, we used a multiple-baseline across-subjects design to investigate the effectiveness of the treatment on midline reach-grasp responding. In Phase 2, we used a reversal design to investigate the effects of repeated implementations and withdrawals of the treatment. In both phases, generalization to right and left positions was measured. In Phase 3, in a multiple-baseline across-responses design, the treatment was implemented in right and left positions. Also in Phase 3, shift of stimulus control from toy-sound to verbal instructions was measured. The results showed that (a) the graduated prompting procedure was effective in training reach-grasp responding in all three children; (b) for one child, the effects were durable over repeated applications of the treatment procedure, but were not maintained during withdrawals; (c) for another child, the treatment procedure was effective in teaching reach-grasp responding in all three positions; and (d) for the same child, training of reach-grasp responding generalized to toys presented without sound, given only the verbal instruction.  相似文献   
938.
939.
940.
We examined the effect of reducing the interval between a patient's call for an appointment and the appointment itself. In Experiment 1, patients calling a family planning unit of a public health department were assigned appointments within either 1 or 3 weeks of their call. Data on patient “shows” and “no-shows” were recorded weekly for 6 weeks. Show rates for those in the 1-week appointment group were significantly higher than those in the 3-week group. In Experiment 2, patients were assigned to appointment dates either the next operating clinic day (next-day group) or 2 weeks from the call date (2-week group). Show rates for those in the next-day group were significantly better than show rates for patients in the 2-week group. Clinic productivity, time spent with patients, and consumer satisfaction were also assessed. Implications for appointment scheduling are discussed.  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