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   686篇
  免费   1篇
  国内免费   1篇
电工技术   1篇
化学工业   15篇
建筑科学   1篇
矿业工程   22篇
能源动力   2篇
轻工业   19篇
水利工程   2篇
无线电   3篇
一般工业技术   14篇
冶金工业   589篇
原子能技术   9篇
自动化技术   11篇
  2023年   1篇
  2022年   3篇
  2021年   4篇
  2020年   2篇
  2019年   1篇
  2017年   4篇
  2016年   1篇
  2014年   4篇
  2013年   27篇
  2012年   7篇
  2011年   5篇
  2010年   4篇
  2009年   5篇
  2008年   2篇
  2007年   7篇
  2006年   3篇
  2004年   3篇
  2003年   2篇
  2002年   2篇
  2000年   1篇
  1999年   8篇
  1998年   174篇
  1997年   95篇
  1996年   63篇
  1995年   41篇
  1994年   27篇
  1993年   26篇
  1992年   8篇
  1991年   3篇
  1990年   3篇
  1989年   4篇
  1988年   8篇
  1987年   1篇
  1986年   3篇
  1985年   3篇
  1983年   3篇
  1982年   4篇
  1981年   4篇
  1980年   13篇
  1978年   3篇
  1977年   28篇
  1976年   72篇
  1975年   2篇
  1970年   2篇
  1963年   1篇
  1955年   1篇
排序方式: 共有688条查询结果,搜索用时 0 毫秒
31.
32.
33.
A pericentric inversion of an X chromosome [46,X,inv(X)(p11q28] with no detectable deletions was ascertained by amniocentesis for prenatal diagnosis in a 42-year-old woman. No defintive counsel could be offered as such an inversion had not been previously reported. At 1 year, the infant appears normal. These data and the review of other recently published karyotypes suggest an absence of a somatic position effect in the human X chromosome and possible biases of ascertainment or possible alternative karyotypic interpretations of some previously reported inv(X) cases.  相似文献   
34.
The first step in a video indexing process is the segmentation of videos into meaningful parts called shots. In this paper we present a formal model of the video shot segmentation process. Starting from a mathematical characterization of the most common transition effects, a video segmentation algorithm capable to detect both abrupt and gradual transitions is proposed. The proposed algorithm is based on the computation of an arbitrary similarity measure between consecutive frames of a video. The algorithm has been tested adopting a similarity metric based on the Animate Vision theory and results have been reported.  相似文献   
35.
36.
37.
38.
T cell cytokines play an important role in mediating airway inflammation in asthma. The predominance of a Th2 cytokine profile, particularly interleukin (IL)-4 and IL-5, is associated with the pathogenesis and course of asthma. The aim of this study was to test the hypothesis that a stressful life event alters the pattern of cytokine release in asthmatic individuals. Thirteen healthy controls and 21 asthmatic adolescents gave blood samples three times over a semester: midsemester, during the week of final examinations, and 2-3 weeks after examinations. Interferon-gamma (IFN-gamma), IL-2, IL-4, and IL-5 were measured from supernatants of cells stimulated with PHA/PMA for 24 h. Cells from asthmatic subjects released significantly more IL-5 during the examination and postexamination periods, whereas cells from healthy controls released significantly more IL-2 during the midsemester and examination periods, thereby indicating a bias for a Th2-like pattern in asthmatics and a Th1-like pattern in healthy controls. IL-4 and IL-5 production showed a marked decrease during and after examinations in healthy controls, whereas this decline was absent in asthmatics. The ratios of IFN-gamma:IL-4 and IFN-gamma:IL-5 also revealed significant changes in the profile of cytokine release across the semester. These results indicate differential cytokine responses in asthmatics that may become pronounced during periods of cellular activation.  相似文献   
39.
40.
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