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   338343篇
  免费   29685篇
  国内免费   14194篇
电工技术   21124篇
技术理论   10篇
综合类   22003篇
化学工业   48002篇
金属工艺   19864篇
机械仪表   20050篇
建筑科学   23057篇
矿业工程   8168篇
能源动力   9119篇
轻工业   23581篇
水利工程   7295篇
石油天然气   12484篇
武器工业   2664篇
无线电   41592篇
一般工业技术   44034篇
冶金工业   13806篇
原子能技术   3425篇
自动化技术   61944篇
  2024年   3771篇
  2023年   4921篇
  2022年   8368篇
  2021年   11436篇
  2020年   8558篇
  2019年   6511篇
  2018年   21019篇
  2017年   21349篇
  2016年   17107篇
  2015年   11528篇
  2014年   14143篇
  2013年   16989篇
  2012年   21961篇
  2011年   29255篇
  2010年   26326篇
  2009年   22742篇
  2008年   23730篇
  2007年   23898篇
  2006年   15237篇
  2005年   13161篇
  2004年   9370篇
  2003年   8069篇
  2002年   7309篇
  2001年   6017篇
  2000年   5187篇
  1999年   4444篇
  1998年   3421篇
  1997年   2877篇
  1996年   2636篇
  1995年   2194篇
  1994年   1756篇
  1993年   1283篇
  1992年   1024篇
  1991年   784篇
  1990年   620篇
  1989年   504篇
  1988年   405篇
  1987年   282篇
  1986年   245篇
  1985年   180篇
  1984年   136篇
  1983年   100篇
  1982年   102篇
  1981年   100篇
  1980年   93篇
  1979年   59篇
  1976年   64篇
  1968年   57篇
  1955年   63篇
  1954年   68篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
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   
52.
53.
54.
Several distributed power control algorithms that can achieve carrier-to-interference ratio (CIR) balancing with probability one have been proposed previously for cellular mobile systems. In these algorithms, only local information is used to adjust transmitting power. However, a normalization procedure is required in each iteration to determine transmitting power and, thus, these algorithms are not fully distributed. In this paper, we present a distributed power control algorithm which does not need the normalization procedure. We show that the proposed algorithm can achieve CIR balancing with probability one. Moreover, numerical results reveal our proposed scheme performs better than the algorithm presented in Grandhi et al. [1994]. The excellent performance and the fully distributed property make our proposed algorithm a good choice for cellular mobile systems  相似文献   
55.
Lin  H. Chang  K.-H. 《Electronics letters》2002,38(13):625-626
Novel high voltage pumping circuits for low supply voltages are proposed. Utilising a small pumping circuit and the new substrate-connected techniques can enhance charge transfer efficiency and eliminate the body effect at low supply voltages. Furthermore, a diode-connected transistor technique can improve the reverse charge sharing phenomenon when the output has a load current. With this technique high boosted voltages can be obtained at low supply voltages  相似文献   
56.
57.
58.
特征X射线能谱法测定Fe^+注入小麦种子的深度   总被引:5,自引:2,他引:3  
颉红梅  卫增泉 《核技术》1997,20(2):105-108
用110keV Fe^+离子束垂直注入小麦种胚后,在扫描电子显微镜上沿种子纵沟剖面,在不同深度上测量Fe元素被激发出的特征X射线强度分布,结果表明分布呈指数衰减,与晶体中的热扩散分布相类似,并对此进行了讨论。  相似文献   
59.
60.
Phase-change read-and-write memory (PRAM) is a promising memory that can solve the problems of conventional memory—scalability, read/write speed, and reliability. We will review the opportunities and technical challenges of PRAM. The most important challenge of PRAM is the reduction of the writing current. Various approaches to reduce the writing current will be reviewed and the prospects of PRAM are discussed.  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