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   1642篇
  免费   16篇
  国内免费   2篇
电工技术   11篇
化学工业   164篇
金属工艺   9篇
机械仪表   16篇
建筑科学   58篇
矿业工程   1篇
能源动力   19篇
轻工业   104篇
水利工程   5篇
无线电   43篇
一般工业技术   124篇
冶金工业   1043篇
自动化技术   63篇
  2023年   13篇
  2022年   15篇
  2021年   21篇
  2020年   11篇
  2019年   12篇
  2018年   21篇
  2017年   19篇
  2016年   20篇
  2015年   8篇
  2014年   24篇
  2013年   28篇
  2012年   27篇
  2011年   45篇
  2010年   22篇
  2009年   21篇
  2008年   39篇
  2007年   44篇
  2006年   42篇
  2005年   34篇
  2004年   19篇
  2003年   21篇
  2002年   15篇
  2001年   7篇
  2000年   9篇
  1999年   24篇
  1998年   319篇
  1997年   206篇
  1996年   121篇
  1995年   74篇
  1994年   65篇
  1993年   56篇
  1992年   13篇
  1991年   23篇
  1990年   11篇
  1989年   10篇
  1988年   24篇
  1987年   18篇
  1986年   15篇
  1985年   9篇
  1983年   6篇
  1982年   7篇
  1981年   9篇
  1980年   8篇
  1978年   7篇
  1977年   29篇
  1976年   59篇
  1973年   3篇
  1970年   1篇
  1969年   1篇
  1954年   1篇
排序方式: 共有1660条查询结果,搜索用时 46 毫秒
1.
Wireless Personal Communications - This paper summarizes the ongoing research initiatives based on the advanced multiple access techniques towards the fifth generation (5G) wireless communication...  相似文献   
2.
3.
ESR spin trapping was used to investigate the reaction of rabbit cytochrome P450 (P450) 1A2 with cumene hydroperoxide. Cumene hydroperoxide-derived peroxyl, alkoxyl, and carbon-centered radicals were formed and trapped during the reaction. The relative contributions of each radical adduct to the composite ESR spectrum were influenced by the concentration of the spin trap. Computer simulation of the experimental data obtained at various 5,5-dimethyl-1-pyrroline N-oxide (DMPO) concentrations was used to quantitate the contributions of each radical adduct to the composite ESR spectrum. The alkoxyl radical was the initial radical produced during the reaction. Experiments with 2-methyl-2-nitrosopropane identified the carbon-centered adducts as those of the methyl radical, hydroxymethyl radical, and a secondary carbon-centered radical. The reaction did not require NADPH-cytochrome P450 reductase or NADPH. It is concluded that the reaction involves the initial homolytic scission of the peroxide O-O bond to produce the cumoxyl radical. Methyl radicals were produced from the beta-scission of the cumoxyl radical. The peroxyl adduct was not observed in the absence of molecular oxygen. We conclude that the DMPO peroxyl radical adduct detected in the presence of oxygen was due to the methylperoxyl radical formed by the reaction of the methyl radical with oxygen. At a higher P450 concentration, a protein-derived radical adduct was also detected.  相似文献   
4.
5.
6.
OBJECTIVE: To describe the health status of a population over 60 years and to study their relationship with several socio-demographic variables. DESIGN: A cross-sectional study, population based. SETTINGS: A community. PARTICIPANTS: A randomized sample of 1,103 non institutionalized people over 60 years living in the city of Cordoba (Spain). MEASUREMENTS AND MAIN RESULTS: By mean of a personal interview at home we used the OARS-MFAQ-VE questionnaire. Low self-rated health was associated with the age, to be female sex, a low cultural background, and a low income. Only 5.2% of the study people do not suffered any illness and 56% state that their health problems are major problems for doing their current activities. 4.9% declared to have some degree of physical incapacity. 3.7% of elderly population has an important cognitive deficit. CONCLUSIONS: The majority of elderly people has good health. Age is related with a poor health. Women have more health problems than men.  相似文献   
7.
8.
9.
10.
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