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   173877篇
  免费   7776篇
  国内免费   155篇
  2021年   1494篇
  2020年   2776篇
  2019年   3434篇
  2018年   3497篇
  2017年   3974篇
  2016年   4600篇
  2015年   3919篇
  2014年   4797篇
  2013年   23437篇
  2012年   4480篇
  2011年   3645篇
  2010年   3897篇
  2009年   4755篇
  2008年   3895篇
  2007年   3372篇
  2006年   4004篇
  2005年   3965篇
  2004年   3456篇
  2003年   3118篇
  2002年   2910篇
  2001年   3506篇
  2000年   3368篇
  1999年   3275篇
  1998年   2844篇
  1997年   2664篇
  1996年   2569篇
  1995年   2413篇
  1994年   2382篇
  1993年   2339篇
  1992年   2702篇
  1991年   2549篇
  1990年   2393篇
  1989年   2295篇
  1988年   2264篇
  1987年   2279篇
  1986年   2246篇
  1985年   2484篇
  1984年   2548篇
  1983年   2307篇
  1982年   2381篇
  1981年   2350篇
  1980年   2180篇
  1979年   2202篇
  1978年   2195篇
  1977年   2170篇
  1976年   1944篇
  1975年   2018篇
  1974年   2068篇
  1973年   1950篇
  1972年   1545篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
182.
183.
184.
OBJECTIVE: This report reviews the evidence that informs the role of health and mental health care providers in addressing youth smoking cessation. DESIGN: Qualitative literature review. RESULTS: Physicians do not consistently screen adolescents for tobacco use and fail to provide recommended cessation advice. Challenges to addressing smoking cessation include the need for procedures to ensure confidentiality and the existence of competing demands to provide other services. Few published studies have specifically addressed the effectiveness of clinical interventions. Interventions that require return visits or follow-up phone contacts are technically difficult to implement in this population. Successful interventions may require resources not available in nonresearch settings. Most studies have used brief clinical intervention as a control condition, making it impossible to evaluate its effectiveness. CONCLUSION: There is little evidence that supports current clinical smoking cessation guidelines for adolescents. More research is needed to develop inexpensive, efficient clinical interventions that can provide youths access to smoking cessation help. Future challenges include reorganizing clinical systems to offer greater counseling by support staff or in electronic formats and to provide effective booster messages and follow-up care in a population that is difficult to track.  相似文献   
185.
186.
By roughly 6 years of age, children acquire the stereotype that men are more competent than women in science, technology, engineering, and mathematics (STEM), potentially leading to greater trust in scientific information provided by men. This study tested whether 3- to 8-year-old children differentially endorsed conflicting information about science and toys presented by male and female informants depicted as a ‘man’ and ‘woman’ (Exp1) or ‘scientists’ (Exp2). Children were expected to endorse toy testimony from gender-matched informants; thus, the key question concerned endorsement of science testimony. In Exp1 (N = 149), boys and girls showed a same-gender informant preference for toy testimony; however, girls endorsed the male informant's testimony more for science than for toys – but only when tested by a male experimenter. In Exp2 (N = 264), boys and girls showed a same-gender preference, irrespective of content. Findings suggest that STEM-related gender stereotypes might lead girls to trust scientific information presented by men over women in certain contexts.  相似文献   
187.
An electronic apparatus using infrared beams for monitoring the movements of individual bees under dark conditions is described. The searching behavior of workers in an arena was monitored over 2-h periods. Mean ambulatory velocity for one bee over a distance of 100 mm was 45.6±1.51 mm/sec (n=45). Thigmokinesis and temporal activity patterns are illustrated.  相似文献   
188.
189.
190.
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