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   452625篇
  免费   5453篇
  国内免费   1329篇
电工技术   8811篇
综合类   663篇
化学工业   68939篇
金属工艺   16905篇
机械仪表   12858篇
建筑科学   11566篇
矿业工程   1677篇
能源动力   12372篇
轻工业   43313篇
水利工程   3968篇
石油天然气   6261篇
武器工业   10篇
无线电   55084篇
一般工业技术   85180篇
冶金工业   84479篇
原子能技术   8939篇
自动化技术   38382篇
  2021年   3316篇
  2019年   3132篇
  2018年   5272篇
  2017年   5132篇
  2016年   5342篇
  2015年   3854篇
  2014年   6607篇
  2013年   20676篇
  2012年   11006篇
  2011年   15236篇
  2010年   12032篇
  2009年   13959篇
  2008年   14318篇
  2007年   14257篇
  2006年   12568篇
  2005年   11621篇
  2004年   11318篇
  2003年   10807篇
  2002年   10635篇
  2001年   10749篇
  2000年   10270篇
  1999年   10743篇
  1998年   26066篇
  1997年   18775篇
  1996年   14685篇
  1995年   11309篇
  1994年   10103篇
  1993年   9776篇
  1992年   7319篇
  1991年   7069篇
  1990年   6870篇
  1989年   6742篇
  1988年   6575篇
  1987年   5625篇
  1986年   5675篇
  1985年   6661篇
  1984年   6064篇
  1983年   5602篇
  1982年   5115篇
  1981年   5330篇
  1980年   4917篇
  1979年   4895篇
  1978年   4672篇
  1977年   5556篇
  1976年   7100篇
  1975年   4032篇
  1974年   3932篇
  1973年   3998篇
  1972年   3327篇
  1971年   3014篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
A generalized response function is presented that can describe several of the practically important transient-response features of MOS systems. It allows for deviations from strict logarithmic time dependencies yet is mathematically tractable in performing linear response analysis. Fits of the generic response function to experimental data are discussed, including the short-term recovery due to hole transport, the long-term recovery due to trapped hole annealing, and the long-term, time-dependent buildup of interface traps. Analytic results for the convolution integral of linear response theory are derived for a square irradiation pulse, and some simple applications are discussed  相似文献   
993.
The Cones synthesis system for automatic generation of VLSI implementations is discussed. Named for the cones in sequential logic, Cones takes behavioral models written in C and produces gate-level implementations in technologies such as standard cells and programmable logic arrays or programmable logic devices. The overall design is produced faster, more efficiently, and with fewer errors. Designers are free to concentrate on functions, instead of on the details of the implementation technology  相似文献   
994.
Kent  R. 《Manufacturing Engineer》2003,82(3):36-37
The telecommunications equipment market is a rapidly changing place. Niche companies are becoming more and more important. Time to market matters more than ever and return on investment is essential. Partnerships are therefore essential. The article examines why this is happening now, and why not earlier.  相似文献   
995.
BACKGROUND: This study is part of the European Community Respiratory Health Survey (ECRHS), which uses a common methodology in different areas throughout the world. This paper describes the prevalences of reported asthma, asthma-like symptoms and nasal allergies, their relationships to age group and sex, and the relationships of asthma-like symptoms to current asthma, in the general population aged 20-44 years of three French urban areas. METHODS: The study population of 2804 subjects in Grenoble, 3774 in Montpellier and 3152 in Paris (18th district), randomly selected from electoral rolls, answered a postal questionnaire (stage I of ECRHS). The response rates were 77.8%, 68.6% and 74.4%, respectively. RESULTS: The prevalences were approximately 14% for wheezing, 16% for chest tightness and 4.5% for nocturnal shortness of breath in the three areas. Asthma attacks in the last 12 months were reported by 2.7% of subjects in Grenoble, 3.5% of subjects in Montpellier and 4.0% of subjects in Paris (P = 0.02). For nasal allergies, the prevalences were 28.0%, 34.3% and 30.8%, respectively (P < 0.001). Asthma was inversely correlated to age (higher prevalence in the youngest) but was not related to sex. Neither age distribution nor sex ratio explained the differences between areas. Among the asthma-like symptoms, wheezing and nocturnal shortness of breath correlated strongly with asthma, chest tightness correlated moderately and nocturnal coughing correlated poorly. CONCLUSION: The prevalences observed were higher than expected from previous comparable French studies in young adults. These results are consistent with the hypothesis of a recent increase of asthma and allergies.  相似文献   
996.
Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 12, pp. 16–20, December, 1992.  相似文献   
997.
998.
999.
1000.
All-Union Scientific-Research Institute of Pipes (VNITI). Il'ich Zhdanov Metallurgical Combine. Translated from Metallurg, No. 9, pp. 39–40, September, 1988.  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