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   76192篇
  免费   2473篇
  国内免费   21篇
  2020年   784篇
  2019年   875篇
  2018年   4310篇
  2017年   3749篇
  2016年   3261篇
  2015年   1103篇
  2014年   1199篇
  2013年   5216篇
  2012年   2607篇
  2011年   4188篇
  2010年   3515篇
  2009年   2574篇
  2008年   3326篇
  2007年   3672篇
  2006年   1611篇
  2005年   1479篇
  2004年   1470篇
  2003年   1369篇
  2002年   1250篇
  2001年   1960篇
  2000年   1865篇
  1999年   1369篇
  1998年   648篇
  1997年   555篇
  1996年   619篇
  1995年   557篇
  1994年   549篇
  1993年   535篇
  1992年   1111篇
  1991年   1030篇
  1990年   1007篇
  1989年   968篇
  1988年   943篇
  1987年   872篇
  1986年   864篇
  1985年   915篇
  1984年   731篇
  1983年   630篇
  1979年   763篇
  1978年   563篇
  1975年   603篇
  1974年   681篇
  1973年   703篇
  1972年   609篇
  1971年   566篇
  1970年   485篇
  1969年   482篇
  1968年   616篇
  1967年   534篇
  1966年   511篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
This article deals with appropriate communication and interpersonal skills that nurses may use in order to support patients who are experiencing self-concept changes related to their health problems. Three areas of patient need related to self-concept are explored. The stages of adaptation to loss and the crucial task of grief work are reviewed, and nursing interventions designed to strengthen the self-concept and support patients as they adapt to loss are suggested. Sensitive communication, although a low-visibility nursing skill, is cited as critical in assisting the patient to achieve an optimum level of wellness.  相似文献   
942.
Six pigeons were trained in a discrete-trials signal-detection procedure to discriminate between a fixed-duration stimulus (5 s or 20 s) and a set of variable durations ranging from 2.5 s to 57.5 s in steps of 5 s. For each fixed-duration stimulus, the ratio of reinforcer frequencies contingent upon reporting the fixed versus the variable stimulus was systematically manipulated. Detection performance was well controlled by both the stimulus value and the reinforcer ratio. Both the discriminability between the fixed duration and the set of variable durations, and the discriminability between the fixed duration and each of the variable durations, were independent of the reinforcer-frequency ratio when discriminability was measured as log d. The sensitivity of response bias to reinforcement-ratio changes was independent of the value of the fixed duration, but was not independent of the discriminability of the variable durations from the fixed durations. Under current models, discriminability measures in complex temporal discrimination may be independent of biasing manipulations, but bias measures are not independent of stimulus values.  相似文献   
943.
Pigeons' choices between alternatives that provided different percentages of reinforcement in mixed schedules were studied using the concurrent-chains procedure. In Experiment 1, the alternatives were terminal-link schedules that were equal in delay and magnitude of reinforcement, but that provided different percentages of reinforcement, with one schedule providing, reinforcement twice as reliably as the other. All pigeons preferred the more reliable schedule, and their level of preference was not systematically affected by variation in the absolute percentage values, or in the magnitude of reinforcement. In Experiment 2, preference for a schedule providing 100% reinforcement over one providing 33% reinforcement increased systematically with increases in the duration of the terminal links. In contrast, preference decreased systematically with increases in the duration of the initial links. Experiment 3 examined choice with equal percentages of reinforcement but unequal delays to reinforcement. Preference for the shorter delay to reinforcement was not systematically affected by variation in the absolute percentage of reinforcement. The overall pattern of results supported predictions based on an extension of the delay-reduction hypothesis to choice procedures involving mixed schedules of percentage reinforcement.  相似文献   
944.
The goals and ends of contemporary medicine are often unclear. An explicit inquiry into the religious dimensions of healing offers an important perspective from which to evaluate the potential capabilities of the medical profession. This paper describes a course in which medical students joined divinity students to explore areas of mutual intellectual, professional, and personal interest. Students and faculty examined in depth three broad areas in which medicine and religion share common ground: concepts of health and illness from the religious perspective, approaches to the understanding of suffering and meaning, and the shared professional stresses of physician and clergy.This paper comes from the Department of Medicine, Beth Israel Hospital, and the Division on Aging and the Program for the Analysis of Clinical Strategies, Harvard Medical School, and the West Roxbury-Brockton Veterans Administration Geriatric Research, Education and Clinical Center, Boston.  相似文献   
945.
946.
Variable-interval schedules of timeout from avoidance   总被引:2,自引:2,他引:0       下载免费PDF全文
Rats were trained on concurrent schedules in which pressing one lever postponed shock and pressing the other occasionally produced a 2-min timeout during which the shock-postponement schedule was suspended and its correlated stimuli were removed. Throughout, the shock-postponement schedule maintained proficient levels of avoidance. Nevertheless, in Experiment 1 responding on the timeout lever was established rapidly, was maintained at stable levels on variable-interval schedules, was extinguished by withholding timeout, was reestablished when timeout was reintroduced, and was brought under discriminative control with a multiple variable-interval extinction schedule of timeout. These results are in contrast with Verhave's (1962) conclusion that timeout is an ineffective reinforcer when presented to rats on intermittent schedules. In Experiment 2 the consequence of responding on the timeout lever was altered so that the shock-postponement schedule remained in effect even though the stimulus conditions associated with timeout were produced for 2 min. Responding extinguished, indicating that suspension of the shock-postponement schedule, not stimulus change, was the source of reinforcement. By establishing the reinforcing efficacy of timeout with standard variable-interval schedules, these experiments illustrate a procedure for studying negative reinforcement in the same way as positive reinforcement.  相似文献   
947.
We develop a simple model of switching between the initial links of a concurrent-chain procedure. Behavior is determined by four parameters μ1, μ2, q1, and q2. The first two are the basic rates of switching from Schedule 1 and Schedule 2, respectively. The second two are the probabilities of leaving Schedule 1 and Schedule 2 after the corresponding terminal link has been completed. We show that for fixed values of these four parameters, the relative allocation on the initial links may change as a result of changes in initial-link schedules. The effect can be quite large if the switching rates are low. An implication is that relative allocation is not necessarily a good measure of behavior.  相似文献   
948.
Pigeons' responses were reinforced on a variant of a mixed variable-interval extinction schedule of reinforcement in which the transition to the higher reinforcement rate was signaled by a trace stimulus projected on the response key prior to the onset of the component correlated with food delivery. In the first of two experiments, the duration of the trace stimulus preceding the component correlated with food delivery was varied from 1.5 to 50.0 s and in the second experiment, the reinforcement frequency in the same component was varied from 10 to 60 reinforcers per hour. Pigeons pecked at the trace stimulus preceding the onset of the component correlated with food delivery even though responding was not reinforced in its presence and only one of the changes in reinforcement rate (i.e., from extinction to reinforcement) was signaled. The rate of pecking during the trace stimulus was a function of its duration but not of the reinforcement frequency in the following component. Higher rates generally occurred at the shorter trace-stimulus durations. Component responding following the offset of the trace stimulus was under discriminative control of the trace stimulus whether or not responding occurred in the presence of the trace stimulus.  相似文献   
949.
Little is known about the personal life of John B. Watson, and this interview aims at capturing the personality of the founder of American behaviorism through the eyes of his son, James B. Watson. Today, psychologists and other social scientists increasingly realize that there is an intimate link between the biography of a psychologist and the kind of psychology he or she founds. Thus biographical information about a founding psychologist can help researchers make explicit this essential link.  相似文献   
950.
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