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   203778篇
  免费   19748篇
  国内免费   7464篇
电工技术   16317篇
技术理论   12篇
综合类   15803篇
化学工业   27608篇
金属工艺   12130篇
机械仪表   13539篇
建筑科学   16545篇
矿业工程   6742篇
能源动力   6375篇
轻工业   14923篇
水利工程   4771篇
石油天然气   10181篇
武器工业   2149篇
无线电   24326篇
一般工业技术   20812篇
冶金工业   7878篇
原子能技术   2512篇
自动化技术   28367篇
  2025年   962篇
  2024年   4575篇
  2023年   4422篇
  2022年   6685篇
  2021年   8939篇
  2020年   7361篇
  2019年   5892篇
  2018年   5854篇
  2017年   6801篇
  2016年   6124篇
  2015年   8687篇
  2014年   10850篇
  2013年   12641篇
  2012年   14587篇
  2011年   15162篇
  2010年   14041篇
  2009年   13173篇
  2008年   13036篇
  2007年   12323篇
  2006年   11307篇
  2005年   9029篇
  2004年   6182篇
  2003年   5264篇
  2002年   5013篇
  2001年   4433篇
  2000年   3602篇
  1999年   3099篇
  1998年   2051篇
  1997年   1697篇
  1996年   1567篇
  1995年   1355篇
  1994年   1088篇
  1993年   669篇
  1992年   558篇
  1991年   425篇
  1990年   336篇
  1989年   283篇
  1988年   200篇
  1987年   131篇
  1986年   124篇
  1985年   54篇
  1984年   49篇
  1983年   32篇
  1982年   52篇
  1981年   48篇
  1980年   45篇
  1979年   28篇
  1978年   11篇
  1953年   10篇
  1951年   17篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
SrMgxTi1 - xO3 nanocrystals (x = 0.1–0.6) were synthesized by the stearic acid gel method. Powder samples were characterized by X-ray diffraction and X-ray photoelectron (XP) spectroscopy. The results showed that the lattice parameter a and the O 1s XP spectrum changed not only with the Mg content x but also with the grain size d of the samples. The conductivity of a thick film specimen fabricated on an aluminium oxide wafer was investigated in a nitrogen—oxygen atmosphere.  相似文献   
4.
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   
5.
The temperature dependence characteristics of hydrogenated amorphous silicon thin-film transistors were investigated. The results indicate that as the temperature was increased, the threshold voltage and the field-effect mobility were first increased, and then decreased, which may be controlled by different mechanisms at low and high temperatures. In addition, if the temperature was higher than 420 K, the Fermi level was promoted to the degenerate-like states, the current channel always existed due to the temperature effect, and the threshold voltage became negative.  相似文献   
6.
研究了Al2O3-TiB2陶瓷刀具材料在1000℃下的氧化行为,用XRD、SEM分析了氧化后的相组成及显微结构。结果表明:Al2O3-TiB2陶瓷材料在1000℃空气中氧化增重符合抛物线规律;随TiB2含量的增加,该材料的抗氧化能力下降。  相似文献   
7.
Conventional drying, dehumidification drying, and combined conventional-dehumidification drying of wood were experimentally studied in this article. The results showed that the energy consumption in the dehumidification drying is the least but its drying time is the longest. The energy consumption in the combined drying is more than that in the dehumidification drying but less than that in the conventional drying, and the drying time is half of that in the dehumidification drying. The advantages of the combined conventional and dehumidification drying are discussed from the experiments results.  相似文献   
8.
通过科研成果转化的气体灭火系统目前己成为我所科技产业中的主导产品。其控制装置是其中关键配套设备。本文就其开发设计中的设计思想、技术原理、技术设计特色等作一阐述  相似文献   
9.
Li  Hongjian  Wei  Yaojun  Xiong  Yu  Ma  Enjie  Tian  Wenhong 《The Journal of supercomputing》2021,77(10):11575-11596
The Journal of Supercomputing - With the fast growth of big data applications, it has brought about a huge increase in the energy consumption for big data processing in Cloud data centers. In this...  相似文献   
10.
Neural Computing and Applications - Image classification method is currently the more popular image technology, but it still has certain problems in practice. In order to improve the image...  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