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   4697篇
  免费   8篇
电工技术   12篇
化学工业   143篇
金属工艺   16篇
机械仪表   20篇
建筑科学   17篇
矿业工程   1篇
能源动力   9篇
轻工业   36篇
无线电   22篇
一般工业技术   73篇
冶金工业   4314篇
原子能技术   7篇
自动化技术   35篇
  2021年   3篇
  2020年   5篇
  2019年   5篇
  2018年   7篇
  2017年   7篇
  2016年   6篇
  2015年   7篇
  2014年   10篇
  2013年   21篇
  2012年   20篇
  2011年   22篇
  2010年   14篇
  2009年   10篇
  2008年   27篇
  2007年   20篇
  2006年   18篇
  2005年   16篇
  2004年   15篇
  2003年   13篇
  2002年   10篇
  2001年   9篇
  2000年   10篇
  1999年   142篇
  1998年   1337篇
  1997年   736篇
  1996年   482篇
  1995年   284篇
  1994年   215篇
  1993年   274篇
  1992年   48篇
  1991年   53篇
  1990年   48篇
  1989年   76篇
  1988年   65篇
  1987年   75篇
  1986年   50篇
  1985年   52篇
  1984年   7篇
  1983年   17篇
  1982年   23篇
  1981年   34篇
  1980年   33篇
  1979年   4篇
  1978年   13篇
  1977年   118篇
  1976年   219篇
  1975年   9篇
  1974年   2篇
  1969年   2篇
  1964年   2篇
排序方式: 共有4705条查询结果,搜索用时 15 毫秒
51.
52.
The presence of gas in bowel could lead to higher than expected doses being given in the radiotherapy of abdominal and pelvic tumors. Radiation detectors were placed in the uterus and vagina of ten patients with caricnoma of cervix, and the actual dose compared with that expected when anterior fields of treatment were employed. Elvations greater than 10% were obtained in six, and severe postradiation morbidity subsequently occured in two of the three showing the highest readings.  相似文献   
53.
54.
The study of the morphology of eggs, larvae, pupae and adults of Aedes excrucians from Germany, Italy and France has led the authors to rise again the binomen Aedes surcoufi (Theobald, 1912) to particularize the european populations. At the same time, the characteristics of the different species of the Aedes excrucians complex are discussed.  相似文献   
55.
56.
The cost of managing 114 adult haemophiliacs in the west of Scotland was assessed for the period 1 March 1971 to 28 February 1974. Altogether 23 of them (20%) accounted for 80% of the resources used. The cost of hospital treatment of these patients during the period was compared with the predicted cost of home treatment, given the availability of freeze-dried factor VIII concentrate in sufficient amounts. We calculate that adequate on-demand home treatment would cost only 16% more than the present treatment, which is substantially less efficient.  相似文献   
57.
58.
59.
The detection of a single-nucleotide mismatch in unlabeled duplex DNA by electrochemical methods is presented. Impedance spectroscopy is used to characterize a perfect duplex monolayer and three DNA monolayers differing in the position of the mismatch. The monolayers were studied as B-DNA (normal duplex DNA) and after conversion to M-DNA (a metalated duplex). Modeling of the impedance data to an equivalent circuit provides parameters that are useful in discriminating the four monolayer configurations. The resistance to charge transfer, R(CT), was lower for all duplexes after conversion to M-DNA. Contrary to expectations, R(CT) was also found to decrease for duplexes containing a mismatch. However, R(CT) was found to be diagnostic for mismatch detection. In particular, the difference in R(CT) between B- and M-DNA (deltaR(CT)) decreased from 190(22) omega.cm(2) for a perfectly matched duplex to 95(20), 30(20), and 85(20) omega.cm(2) for a mismatch at the top (distal), middle, and bottom (proximal) positions of the monolayer with respect to the gold surface. Further, a method to form loosely packed single-stranded (ss)-DNA monolayers by duplex dehybridization that is able to rehybridize to target strands is presented. Rehybridization efficiencies were in the range of 40-70%. Under incomplete hybridization conditions, the R(CT) was the same for matched and mismatched duplexes under B-DNA conditions. However, deltaR(CT) between B- and M-DNA, under incomplete hybridization, still provided a distinction. The deltaR(CT) for a perfect duplex was 76(12) omega.cm(2), whereas a mismatch in the middle of the sequence yielded a deltaR(CT) value of 30(15) omega.cm(2). The detection limit was measured and the impedance methodology reliably detected single DNA base pair mismatches at concentrations as low as 100 pM.  相似文献   
60.
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