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   48585篇
  免费   2047篇
  国内免费   32篇
  2020年   562篇
  2019年   685篇
  2018年   991篇
  2017年   1056篇
  2016年   1013篇
  2015年   763篇
  2014年   883篇
  2013年   3958篇
  2012年   1491篇
  2011年   1662篇
  2010年   1043篇
  2009年   1007篇
  2008年   1402篇
  2007年   1331篇
  2006年   1193篇
  2005年   996篇
  2004年   951篇
  2003年   980篇
  2002年   924篇
  2001年   1764篇
  2000年   1744篇
  1999年   1220篇
  1998年   545篇
  1997年   472篇
  1996年   436篇
  1993年   422篇
  1992年   1017篇
  1991年   971篇
  1990年   949篇
  1989年   899篇
  1988年   844篇
  1987年   815篇
  1986年   804篇
  1985年   857篇
  1984年   682篇
  1983年   556篇
  1979年   633篇
  1978年   488篇
  1977年   451篇
  1976年   422篇
  1975年   582篇
  1974年   639篇
  1973年   649篇
  1972年   573篇
  1971年   476篇
  1970年   449篇
  1969年   507篇
  1968年   568篇
  1967年   482篇
  1966年   559篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
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   
44.
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   
45.
46.
47.
This essay will focus on the Buddhist metaphysics of experience which is generally glossed over due to the excessive concern for the ultimate goal in Buddhism, nirvīna , and in consequence of which the emphasis has been on the practice of; meditative discipline in aspiration for that goal. Yet neither nirvana nor meditative discipline can be understood properly without examining the full dimension of our ordinary experience. Such an examination should reveal to us the unique ways in which the Buddhist refers to the bounded and unbounded conditions of existence. All this is novel insofar as metaphysics goes and indeed it would have to be a unique form of metaphysics in order to accommodate the dual aspect of existence. The key to this metaphysics lodges in the Buddhist concept of experiential process,1 technically known as pratītyasamutpāda which is variously translated as relational origination, interrelational origination or dependent origination. It refers to the Buddhist concept of causality but, as we shall see, it is a unique concept with more than the usual Western connotation.  相似文献   
48.
OBJECTIVE: To examine dysregulation in biological measures associated with histories of abuse in women and whether women with premenstrual dysphoric disorder (PMDD) differ in their dysregulation. DESIGN: Twenty-five women meeting prospective criteria for PMDD and 42 non-PMDD controls underwent structured interview to determine abuse histories and lifetime Axis I diagnoses, excluding those with current Axis I disorders or using medications. MAJOR OUTCOME MEASURES: Plasma cortisol and norepinephrine (NE), heart rate (HR), blood pressure (BP), and vascular resistance index (VRI) were assessed at rest and in response to mental stress. RESULTS: A greater proportion of PMDD women had prior abuse compared with non-PMDD women. Regardless of PMDD status, all abused women had lower plasma NE and higher HRs and tended to have lower plasma cortisol at rest and during stress. Abused women also reported more severe daily emotional and physical symptoms. Greater VRI and BP at rest and during stress were seen only in PMDD women with abuse. CONCLUSION: There is persistent dysregulation in stress-responsive systems in all abused women that cannot be accounted for by current psychiatric illness or medications, and PMDD women may be differentially more vulnerable to the impact of abuse on measures reflecting alpha-adrenergic receptor function.  相似文献   
49.
Four experiments were conducted to determine whether echoic memory plays a role in differences between good and poor readers. The first two experiments used a suffix procedure in which the subject is read a list of digits with either a tone control or the word go appended to the list. For lists that exceeded the length of the subjects memory span by one digit (i.e., that avoided ceiling effects), the poor readers showed a larger decrement in the suffix condition than did the good readers. The third experiment was directed at the question of whether the duration of echoic memory is different for good and poor readers. Children shadowed words presented to one ear at a rate determined to give 75-85% shadowing accuracy. The items presented to the nonattended ear were words and an occasional digit. At various intervals after the presentation of the digit, a light signaled that the subject was to cease shadowing and attempt to recall any digit that had occurred in the nonattended ear recently. Whereas good and poor readers recalled the digit equally if tested immediately after presentation, the poor readers showed a faster decline in recall of the digit as retention interval increased. A fourth experiment was conducted to determine whether the differences in echoic memory were specific to speech stimuli or occurred at a more basic level of aural persistence. Bursts of white noise were separated by 9-400 ms of silence and the subject was to say whether there were one or two sounds presented. There were no differences in detectability functions for good and poor readers.  相似文献   
50.
Pregnancy reflects a common experience for women in today's workforce, yet recent data suggest that some women scale back or leave the workforce following childbirth. Considering these effects on women's careers, researchers have sought to understand the underlying dynamics of these decisions. Here, we explore a paradoxical reason for weakened postpartum career attitudes: help that women receive during pregnancy. We integrate stereotype threat and benevolent sexism theories to explain how the effects of help on postpartum intentions to quit may be transmitted through reductions in work self-efficacy. In doing so, we consider the role of perceived impact—or the extent to which help interferes with versus enables women's perceived ability to continue performing their work role. Results of a weekly diary study of 105 pregnant employees suggest that work-interfering help led to decreased self-efficacy for work during the following week. Furthermore, there was an indirect effect of average help received at work during pregnancy on postpartum intentions to quit the workforce through reductions in work self-efficacy that was stronger insofar as help was work-interfering versus work-enabling. Taken together, our results highlight unintended negative consequences that occur when others provide ineffective support to women at work during pregnancy.  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