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   781491篇
  免费   8848篇
  国内免费   1578篇
电工技术   14751篇
综合类   974篇
化学工业   121940篇
金属工艺   30286篇
机械仪表   24299篇
建筑科学   18465篇
矿业工程   4900篇
能源动力   20242篇
轻工业   66593篇
水利工程   8682篇
石油天然气   16699篇
武器工业   43篇
无线电   87201篇
一般工业技术   154811篇
冶金工业   138372篇
原子能技术   17888篇
自动化技术   65771篇
  2021年   6899篇
  2019年   6622篇
  2018年   11400篇
  2017年   11455篇
  2016年   11957篇
  2015年   7695篇
  2014年   12981篇
  2013年   36007篇
  2012年   20373篇
  2011年   27595篇
  2010年   22047篇
  2009年   24663篇
  2008年   25259篇
  2007年   25103篇
  2006年   21819篇
  2005年   19943篇
  2004年   19231篇
  2003年   18752篇
  2002年   18131篇
  2001年   17903篇
  2000年   17176篇
  1999年   17280篇
  1998年   40523篇
  1997年   29346篇
  1996年   22927篇
  1995年   17641篇
  1994年   16032篇
  1993年   15676篇
  1992年   12114篇
  1991年   11591篇
  1990年   11499篇
  1989年   11236篇
  1988年   10837篇
  1987年   9571篇
  1986年   9469篇
  1985年   10892篇
  1984年   9841篇
  1983年   9354篇
  1982年   8435篇
  1981年   8686篇
  1980年   8187篇
  1979年   8270篇
  1978年   8043篇
  1977年   9069篇
  1976年   11507篇
  1975年   7165篇
  1974年   6846篇
  1973年   6988篇
  1972年   5930篇
  1971年   5471篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
A novel hierarchical intelligent controller configuration is proposed using an artificial neural network as a control-mode classifier in the supervisory level and a set of pre-designed controllers in the lower level. Controller outputs are modified nonlinearly by the classifying signals in a structure resembling one artificial neuron with adaptively changed weights. The lower-level local controllers are implemented using neural networks. An illustrative example of this approach is based on the transient stabilization of a single-machine infinite-bus system studied in Flexible AC Transmission Systems (FACTS) research.  相似文献   
993.
994.
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   
995.
The management of pain in patients with burn wounds is complex and problematic. Burn-wound pain is severe, inconsistent and underestimated. Patients experience severe pain, especially during procedures, until wound healing has occurred. A multi-modality approach is needed for effective management of pain, which requires an understanding of the mechanisms of pain. Altered pharmacokinetics and pharmacodynamics in burn-wound patients makes drug actions unpredictable. Opioids alone are seldom sufficient for pain control. The multi-modality approach includes the use of opioids and non-steroidal anti-inflammatory, anxiolytic and alternative drugs. Ketamine has been found to be a useful agent for analgesia in burn-wound patients; a dose of 10 mg/kg qid per os was found to be an effective adjunct to pain therapy.  相似文献   
996.
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   
997.
This review shows that quantitative measurements of fundus reflectance can be described by models that explicitly incorporate anatomical and physical properties of the fundus tissue. Newer techniques examine the fundus in ways fundamentally different from conventional optics, and must be included in this approach of measurement and modeling. The importance of the “inner surface reflector” (ISR) for tomographic imaging warrants more study of its optical properties, particularly its directional reflectance. For example, because the surface of a glaucomatous optic disc can slope steeply into the cup, the directional reflectance of the ISR may affect its apparent topography and thus the reproducibility of measurements of cup size  相似文献   
998.
999.
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   
1000.
One or more layers of textiles can provide a thermal resistance between the human body and its environment, and so help maintain the body in a thermally comfortable state. The effect of wind on and its penetration through such thermal cladding is examined experimentally.  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