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   56790篇
  免费   1489篇
  国内免费   18篇
  58297篇
  2020年   420篇
  2019年   521篇
  2018年   3993篇
  2017年   3366篇
  2016年   2892篇
  2015年   759篇
  2014年   696篇
  2013年   3166篇
  2012年   1659篇
  2011年   3513篇
  2010年   3158篇
  2009年   2217篇
  2008年   2690篇
  2007年   3111篇
  2006年   1013篇
  2005年   1081篇
  2004年   989篇
  2003年   969篇
  2002年   851篇
  2001年   1336篇
  2000年   1332篇
  1999年   963篇
  1998年   490篇
  1997年   402篇
  1996年   378篇
  1995年   373篇
  1994年   390篇
  1993年   349篇
  1992年   800篇
  1991年   742篇
  1990年   722篇
  1989年   648篇
  1988年   619篇
  1987年   627篇
  1986年   580篇
  1985年   656篇
  1984年   520篇
  1983年   423篇
  1982年   339篇
  1979年   510篇
  1978年   398篇
  1977年   368篇
  1976年   343篇
  1975年   440篇
  1974年   438篇
  1973年   501篇
  1972年   397篇
  1968年   400篇
  1967年   350篇
  1966年   393篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
22.
23.
24.
25.
26.
Although perceived health risk plays a prominent role in theories of health behavior, its empirical role in risk taking is less clear. In Study 1 (N = 129), 2 measures of drivers' risk-taking behavior were found to be unrelated to self-estimates of accident concern but to be related to self-ratings of driving skill and the perceived thrill of driving. In Study 2 (N = 405), out of a wide range of potential influences, accident concern had the weakest relationship with risk taking. The authors concluded that although health risk is a key feature in many theories of health behavior and a central focus for researchers and policy makers, it may not be such a prominent factor for those actually taking the risk.  相似文献   
27.
28.
29.
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   
30.
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   
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