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   223785篇
  免费   14993篇
  国内免费   45篇
  2021年   1741篇
  2018年   3128篇
  2017年   3030篇
  2016年   3681篇
  2015年   3218篇
  2014年   4456篇
  2013年   6350篇
  2012年   7566篇
  2011年   8084篇
  2010年   5734篇
  2009年   4891篇
  2008年   7203篇
  2007年   7489篇
  2006年   7192篇
  2005年   6715篇
  2004年   6868篇
  2003年   6582篇
  2002年   6533篇
  2001年   9284篇
  2000年   8964篇
  1999年   6989篇
  1998年   2125篇
  1997年   1888篇
  1996年   1753篇
  1992年   5466篇
  1991年   5682篇
  1990年   5651篇
  1989年   5626篇
  1988年   5209篇
  1987年   4863篇
  1986年   4443篇
  1985年   4680篇
  1984年   3699篇
  1983年   3027篇
  1982年   2018篇
  1981年   1721篇
  1980年   1725篇
  1979年   3343篇
  1978年   2578篇
  1977年   2377篇
  1976年   2328篇
  1975年   2830篇
  1974年   3120篇
  1973年   3085篇
  1972年   2747篇
  1971年   2606篇
  1970年   2217篇
  1969年   2159篇
  1968年   2034篇
  1967年   1797篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Biophysics - The biophysical aspects of the effects of ultrasound on biological tissues are considered. A mathematical model that describes the effects of the primary interaction of mechanical...  相似文献   
993.
This study seeks to explore whether neuroticism, agreeableness, and conscientiousness moderate the influence of relationship conflict experienced in groups on changes in group members'' evaluative cognitions related to teamwork quality (teamwork-related mental models). Data from 216 students, nested in 48 groups were analyzed using a multilevel modeling approach. Our results show that the experience of relationship conflict leads to a negative shift from the pre-task to the post-task teamwork-related mental models. Moreover, the results indicate that conscientiousness buffered the negative association between relationship conflict and the change in teamwork-related mental models. Our results did not support the hypothesized moderating effect of agreeableness and show that the detrimental effect of relationship conflict on the shift in teamwork-related mental models is accentuated for group members scoring low rather than high on neuroticism. These findings open new research venues for exploring the association between personality, coping styles and change in teamwork-related mental models.  相似文献   
994.
995.
996.
997.
998.
999.
1000.
Begging behaviour is an important element in the parent-offspring conflict; it has been studied in many avian species. However, the majority of the studies have been entirely based on the call counts, and they agreed that vocal activity was a good indicator of chick’s nutritional need and/or condition. Fewer researches were dedicated to the temporal-frequency variables of the begging calls themselves and they showed contrary results. Here begging behaviour in three burrow nested, uniparous species of auks (Alcidae) was studied. These objects provide an opportunity to study the signalling value of begging calls in the absence of important confounding factors such as nestling competition and predation pressure. I recorded calls of individual chicks in two conditions: during natural feeding and after experimental four-hour food deprivation. I found that almost all measured acoustic variables contain information about the chick’s state in all studied species. The hungry chicks produced calls higher in fundamental frequency and power variables and at higher calling rate compared to naturally feeding chicks. The effect of food deprivation on most acoustic variables exceeded both the effects of individuality and species. In all studied species, the frequency variables were stronger affected by hunger than the calling rate and call durations. I suppose that such strong change of acoustic variables after food deprivation can be explained by absence of vocal individual identification in these birds. As parents do not need to check individuality of the chick in the burrow, which they find visually during the day time, the chicks could use all of the acoustic variables to communicate about their nutritional needs.  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