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   227449篇
  免费   15274篇
  国内免费   53篇
  2021年   1828篇
  2018年   3192篇
  2017年   3072篇
  2016年   3764篇
  2015年   3358篇
  2014年   4636篇
  2013年   6551篇
  2012年   7852篇
  2011年   8340篇
  2010年   5868篇
  2009年   5027篇
  2008年   7403篇
  2007年   7668篇
  2006年   7338篇
  2005年   6850篇
  2004年   6991篇
  2003年   6697篇
  2002年   6654篇
  2001年   9385篇
  2000年   9013篇
  1999年   7081篇
  1998年   2155篇
  1997年   1977篇
  1996年   1843篇
  1992年   5516篇
  1991年   5718篇
  1990年   5688篇
  1989年   5652篇
  1988年   5253篇
  1987年   4896篇
  1986年   4475篇
  1985年   4702篇
  1984年   3711篇
  1983年   3039篇
  1982年   2025篇
  1981年   1732篇
  1980年   1741篇
  1979年   3365篇
  1978年   2591篇
  1977年   2389篇
  1976年   2345篇
  1975年   2841篇
  1974年   3136篇
  1973年   3094篇
  1972年   2760篇
  1971年   2610篇
  1970年   2220篇
  1969年   2166篇
  1968年   2038篇
  1967年   1800篇
排序方式: 共有10000条查询结果,搜索用时 62 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