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   3224篇
  免费   370篇
  国内免费   233篇
  2024年   16篇
  2023年   136篇
  2022年   68篇
  2021年   95篇
  2020年   192篇
  2019年   200篇
  2018年   218篇
  2017年   215篇
  2016年   220篇
  2015年   120篇
  2014年   119篇
  2013年   682篇
  2012年   85篇
  2011年   72篇
  2010年   64篇
  2009年   94篇
  2008年   129篇
  2007年   146篇
  2006年   145篇
  2005年   125篇
  2004年   101篇
  2003年   83篇
  2002年   82篇
  2001年   70篇
  2000年   63篇
  1999年   48篇
  1998年   29篇
  1997年   48篇
  1996年   37篇
  1995年   21篇
  1994年   27篇
  1993年   14篇
  1992年   12篇
  1991年   8篇
  1990年   3篇
  1989年   3篇
  1988年   5篇
  1987年   4篇
  1986年   4篇
  1985年   5篇
  1984年   3篇
  1983年   2篇
  1982年   1篇
  1981年   1篇
  1979年   2篇
  1978年   4篇
  1977年   3篇
  1976年   2篇
  1975年   1篇
排序方式: 共有3827条查询结果,搜索用时 15 毫秒
1.
2.
3.
A caseload analysis was undertaken to investigate those clients seen by five community mental health centre teams within one healthcare district. The 985 clients are described in terms of demographic and clinical features and questions relating to service provision are discussed.  相似文献   
4.
Evidence increasingly links a high-fat, low-fiber diet to coronary heart disease and certain site cancers, indicating a need for large-scale dietary change. Studies showing the effectiveness of particular procedures in specific settings are important at this point. The present study, using an A-B-A-B design and sales data from computerized cash registers, replicated and extended previous work by showing that inexpensive prompts (i.e., signs and fliers) in a national fast-food restaurant could increase the sales of salads, a low-fat, high-fiber menu selection. Suggestions also are made pertinent to more widespread use of the procedures.  相似文献   
5.
6.
Genetic issues are demanding more attention in the area of public health. Adoption agencies and policymakers are beginning to address these issues where they relate to the adoption process and to the many families involved in adoption in this country. Genetic counselors need to play an active role as both educators of and consultants for adoption professionals and the families with whom they work. To facilitate a partnership between genetics and adoption we have developed a workshop intended to educate adoption professionals about the lifelong implications of genetic conditions on the adoption triad.  相似文献   
7.
The challenge of excellence in community health services has been taken up by medical educators in Colombia. Confronted with a nation where the primary indicators of disease mortality and morbidity (cardiovascular disease and infant mortality) were characteristic of First and Third World patterns, respectively, the Ministry of Health and La Asociacion Colombiana de Facultades de Medicina (ASCOFAME), representatives of institutions of medical education, have collaborated to conduct a needs assessment of the country's health needs and devised an implementation plan designed to better address the needs of the majority of that nation's people.As a model, the Colombian reorganization of medical education is an example which could be emulated by the U.S. where policy makers are struggling with troublesome questions of cost, equity and quality.  相似文献   
8.
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   
9.
The matching law applies to wagtails' foraging in the wild   总被引:2,自引:2,他引:0       下载免费PDF全文
Field data concerning the time budgets and foraging success of pied wagtails (Motacilla alba yarrelli, Gould) are reanalyzed. It is found that the data are well described by the generalized matching law, with a marked bias towards spending time on the territory. In this case matching is not the result of maximizing reward rate, but it remains possible that it results from an allocation of time that maximizes survival.  相似文献   
10.
It has been suggested that the failure to maximize reinforcement on concurrent variable-interval, variable-ratio schedules may be misleading. Inasmuch as response costs are not directly measured, it is possible that subjects are optimally balancing the benefits of reinforcement against the costs of responding. To evaluate this hypothesis, pigeons were tested in a procedure in which interval and ratio schedules had equal response costs. On a concurrent variable time (VT), variable ratio-time (VRT) schedule, the VT schedule runs throughout the session and the VRT schedule is controlled by responses to a changeover key that switches from one schedule to the other. Reinforcement is presented independent of response. This schedule retains the essential features of concurrent VI VR, but eliminates differential response costs for the two alternatives. It therefore also eliminates at least one significant ambiguity about the reinforcement maximizing performance. Pigeons did not maximize rate of reinforcement on this procedure. Instead, their times spent on the alternative schedules matched the relative rates of reinforcement, even when schedule parameters were such that matching earned the lowest possible overall rate of reinforcement. It was further shown that the observed matching was not a procedural artifact arising from the constraints built into the schedule.  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