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   749833篇
  免费   8459篇
  国内免费   1682篇
电工技术   13672篇
综合类   602篇
化学工业   118264篇
金属工艺   30625篇
机械仪表   23444篇
建筑科学   17501篇
矿业工程   5253篇
能源动力   19176篇
轻工业   62471篇
水利工程   8738篇
石油天然气   18164篇
武器工业   48篇
无线电   80492篇
一般工业技术   151111篇
冶金工业   130730篇
原子能技术   18233篇
自动化技术   61450篇
  2021年   6701篇
  2019年   6361篇
  2018年   11155篇
  2017年   11258篇
  2016年   11904篇
  2015年   7539篇
  2014年   12702篇
  2013年   34141篇
  2012年   19772篇
  2011年   26671篇
  2010年   21568篇
  2009年   24063篇
  2008年   24543篇
  2007年   24161篇
  2006年   21044篇
  2005年   19296篇
  2004年   18285篇
  2003年   17842篇
  2002年   17447篇
  2001年   16977篇
  2000年   16229篇
  1999年   16108篇
  1998年   37781篇
  1997年   27596篇
  1996年   21481篇
  1995年   16494篇
  1994年   14922篇
  1993年   14554篇
  1992年   11246篇
  1991年   10974篇
  1990年   10781篇
  1989年   10580篇
  1988年   10167篇
  1987年   9071篇
  1986年   8852篇
  1985年   10135篇
  1984年   9356篇
  1983年   8899篇
  1982年   8031篇
  1981年   8278篇
  1980年   7866篇
  1979年   7926篇
  1978年   7818篇
  1977年   8867篇
  1976年   11251篇
  1975年   7082篇
  1974年   6790篇
  1973年   6879篇
  1972年   5903篇
  1971年   5525篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
991.
Ways in which spreadsheet programs can be used to introduce practical considerations in introductory electrical engineering courses are discussed. Examples are presented which show that spreadsheets can be used to predict and/or minimize the errors due to loading, the availability of only standard resistor values, and resistor tolerances. The circuits considered in these examples were selected to be as simple as possible. These examples could be used in the first semester of sophomore credits. They illustrate trade-offs, performance criteria, and nonunique solutions, and are intended to illustrate the power of spreadsheet programs. In the first example, a macro is used to implement a simple iterative optimization procedure. In the second example, minimization is done by exhaustive search using the table lookup capabilities of the spreadsheet. In the final example, the spreadsheet's random number generator is used to perform a Monte Carlo analysis  相似文献   
992.
993.
994.
995.
996.
233 undergraduates (162 women and 71 men) completed a demographics questionnaire and measures of career-decision-making (CDM) self-efficacy (K. M. Taylor and N. E. Betz, 1983), CDM attitudes (J. O. Crites, 1978), and CDM skills (D. E. Super et al, 1981). Results revealed that CDM self-efficacy was moderately and positively related to CDM attitudes and age of participants (p?  相似文献   
997.
BACKGROUND: In the outpatient use of tuberculin skin testing (purified protein derivative [PPD]), it is at times inconvenient to have a patient revisit for interpretation. Therefore, we assessed patients' ability to self-interpret these test results. METHODS: In keeping with prior custom, patients were seen by an experienced nurse, who performed skin testing with PPD intermediate strength as well as mumps and Candida anergy control tests in some cases, and explained the procedure. The patients were asked to return 48 to 72 h later, at which time one of the researchers recorded their test interpretations before they were again evaluated by the nurse. RESULTS: Sixty-eight patients were studied, of whom 59 returned at appropriate interval. Eighteen patients had a positive PPD test reaction of 10 to 20 mm induration, which only one patient correctly identified as a positive test result. However, positive anergy control tests were correctly interpreted in 10 of 27 cases. CONCLUSION: The small number of positive PPD test result recognition by these patients may be partially attributed to their lack of education, as well as foreign birth and denial of illness. PPD results should be checked by an experienced professional.  相似文献   
998.
999.
As the number of fuzzy logic applications increases, demand for faster architectures will grow. Our design for a VLSI fuzzy processor uses fuzzy inference techniques that optimize processing time. Preprocessing that reduces the number of rules to be processed, parallel computation of active rule degrees of activation, and scalability are major features of this architecture. The journal issue contains a concise summary of this article. The complete article is linked to Micro's home page on the World Wide Web (http://www.computer.org/pubs/micro/micro.htm)  相似文献   
1000.
Grace  D. Burr  A.G. Tozer  T.C. 《Electronics letters》1996,32(21):1956-1957
The performance of two distributed channel assignment algorithms which use coexistence etiquettes for point to point links are considered by the authors. It has been found that selecting channels prior to transmission at the transmitter as opposed to the receiver, supports greater offered traffic with the additional advantage of a less complex protocol  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