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   5210篇
  免费   536篇
  国内免费   288篇
电工技术   427篇
综合类   480篇
化学工业   469篇
金属工艺   322篇
机械仪表   284篇
建筑科学   282篇
矿业工程   243篇
能源动力   174篇
轻工业   451篇
水利工程   155篇
石油天然气   135篇
武器工业   103篇
无线电   481篇
一般工业技术   381篇
冶金工业   1010篇
原子能技术   65篇
自动化技术   572篇
  2024年   35篇
  2023年   91篇
  2022年   194篇
  2021年   276篇
  2020年   167篇
  2019年   110篇
  2018年   140篇
  2017年   153篇
  2016年   121篇
  2015年   178篇
  2014年   229篇
  2013年   303篇
  2012年   356篇
  2011年   408篇
  2010年   356篇
  2009年   357篇
  2008年   331篇
  2007年   324篇
  2006年   291篇
  2005年   204篇
  2004年   165篇
  2003年   96篇
  2002年   97篇
  2001年   67篇
  2000年   57篇
  1999年   40篇
  1998年   241篇
  1997年   134篇
  1996年   91篇
  1995年   56篇
  1994年   47篇
  1993年   54篇
  1992年   14篇
  1991年   11篇
  1990年   13篇
  1989年   13篇
  1988年   16篇
  1987年   11篇
  1986年   16篇
  1985年   12篇
  1983年   3篇
  1982年   9篇
  1981年   13篇
  1980年   12篇
  1978年   4篇
  1977年   31篇
  1976年   68篇
  1975年   6篇
  1972年   2篇
  1955年   3篇
排序方式: 共有6034条查询结果,搜索用时 46 毫秒
21.
This paper presents a mathematical model that is capable of calculating the ampacity of a wide variety of power cable designs consisting of an arbitrary number of layers on a cable reel. The model considers round cables with copper conductors. The validity and accuracy of the ampacity model were verified by comparing the predicted temperature distribution within the reel with measured temperatures collected during an extensive testing program conducted at the US Bureau of Mines (USBM). The mathematical model predicted a temperature distribution within the cable layers that was very close to the measured variation in temperature. The value of the program is illustrated by calculating ampacities for several copper conductor sizes  相似文献   
22.
电容位移法精确测量磁性薄膜的磁致伸缩系数   总被引:8,自引:1,他引:7  
万红  邱佚  谢海涛  斯永敏  扬德明 《功能材料》2002,33(3):262-263,266
介绍了一种精确测量磁性薄膜磁致伸缩系数方法-电容位移法,并自行研制组装了一套测量装置,通过误差分析,仪器的精确标定,对稀土-铁超磁致伸缩薄膜的磁致伸缩系数进行了测量,获得满意的结果。  相似文献   
23.
CI-994 (acetyldinaline) is an orally active anticancer drug currently in Phase 1 clinical trials. To assess its preclinical toxicity, CI-994 was administered orally as suspensions to Wistar rats (10/sex/dose) and in capsules to beagle dogs (3/sex/dose) once daily for two weeks. Doses were 1.5, 5, and 15 mg/kg for rats (9, 30, and 90 mg/m2, respectively), and 0.5, 2, and 5 mg/kg for dogs (10, 40, and 100 mg/m2, respectively). Systemic exposure was dose-proportional based on toxicokinetic analysis in dogs. Severe clinical signs and mortality occurred at the highest dose in both species beginning on Day 10. Neutropenia, lymphocytopenia, thrombocytopenia, lymphoid depletion, bone marrow hypocellularity, and testicular degeneration were observed in both species, primarily at the mid- and high-doses. Despite continued treatment, neutrophil counts in dogs returned to control levels in Week 2. Other microscopic findings in rats included splenic hematopoietic depletion at all doses and epithelial cell necrosis in various tissues at 15 mg/kg. Additional bone marrow changes in dogs involved myeloid and megakaryocyte hyperplasia at 2 mg/kg and abnormal myeloid and megakaryocyte maturation at 2 and 5 mg/kg. Except for the testicular effects in both species, all changes were reversible within a 4-week (rat) or 9-week (dog) recovery period. The results of these studies show that target organ effects of CI-994 principally involve tissues with rapidly dividing cell populations and that bone marrow suppression is the dose-limiting toxicity. CI-994 also seems to interfere with the release and/or maturation of cells in the bone marrow.  相似文献   
24.
25.
26.
27.
斯厚达 《微特电机》2003,31(6):42-44
介绍摩托车起动电机的安装设计原则和方法,安装误差的形成与计算,以及达到安装设计要求的工艺保证措施,同时还分析了在检测和加工中所存在的一些做法。  相似文献   
28.
29.
The final stage in the production of a radiotherapy treatment plan must always be an independent check that the linear accelerator settings given on the plan do in fact deliver the required dose distribution. A tool is described that enables rapid checking of diaphragm settings in relation to the patient.  相似文献   
30.
Activation of auditory cortex during silent lipreading   总被引:1,自引:0,他引:1  
Watching a speaker's lips during face-to-face conversation (lipreading) markedly improves speech perception, particularly in noisy conditions. With functional magnetic resonance imaging it was found that these linguistic visual cues are sufficient to activate auditory cortex in normal hearing individuals in the absence of auditory speech sounds. Two further experiments suggest that these auditory cortical areas are not engaged when an individual is viewing nonlinguistic facial movements but appear to be activated by silent meaningless speechlike movements (pseudospeech). This supports psycholinguistic evidence that seen speech influences the perception of heard speech at a prelexical stage.  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