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   1102篇
  免费   11篇
电工技术   16篇
综合类   1篇
化学工业   83篇
金属工艺   10篇
机械仪表   7篇
建筑科学   27篇
矿业工程   5篇
能源动力   11篇
轻工业   33篇
水利工程   6篇
无线电   19篇
一般工业技术   79篇
冶金工业   766篇
原子能技术   11篇
自动化技术   39篇
  2021年   6篇
  2020年   3篇
  2019年   6篇
  2018年   5篇
  2017年   5篇
  2016年   4篇
  2015年   5篇
  2014年   6篇
  2013年   23篇
  2012年   14篇
  2011年   18篇
  2010年   10篇
  2009年   14篇
  2008年   13篇
  2007年   21篇
  2006年   21篇
  2005年   13篇
  2004年   12篇
  2003年   8篇
  2002年   8篇
  2001年   13篇
  2000年   14篇
  1999年   29篇
  1998年   228篇
  1997年   123篇
  1996年   93篇
  1995年   56篇
  1994年   35篇
  1993年   65篇
  1992年   18篇
  1991年   15篇
  1990年   12篇
  1989年   14篇
  1988年   10篇
  1987年   10篇
  1986年   9篇
  1985年   13篇
  1984年   11篇
  1983年   4篇
  1982年   6篇
  1981年   7篇
  1980年   10篇
  1979年   4篇
  1978年   6篇
  1977年   27篇
  1976年   44篇
  1975年   5篇
  1972年   3篇
  1969年   2篇
  1966年   3篇
排序方式: 共有1113条查询结果,搜索用时 468 毫秒
1.
The current research work presents a facile and cost–effective co-precipitation method to prepare doped (Co & Fe) CuO and undoped CuO nanostructures without usage of any type of surfactant or capping agents. The structural analysis reveals monoclinic crystal structure of synthesized pure CuO and doped-CuO nanostructures. The effect of different morphologies on the performance of supercapacitors has been found in CV (cyclic voltammetry) and GCD (galvanic charge discharge) investigations. The specific capacitances have been obtained 156 (±5) Fg?1, 168(±5) Fg?1 and 186 (±5) Fg?1 for CuO, Co-doped CuO and Fe-doped CuO electrodes, respectively at scan rate of 5 mVs?1, while it is found to be 114 (±5) Fg?1, 136 (±5) Fg?1 and 170 (±5) Fg?1 for CuO, Co–CuO and Fe–CuO, respectively at 0.5 Ag-1 as calculated from the GCD. The super capacitive performance of the Fe–CuO nanorods is mainly attributed to the synergism that evolves between CuO and Fe metal ion. The Fe-doped CuO with its nanorods like morphology provides superior specific capacitance value and excellent cyclic stability among all studied nanostructured electrodes. Consequently, it motivates to the use of Fe-doped CuO nanostructures as electrode material in the next generation energy storage devices.  相似文献   
2.
3.
Immunisation practices were examined at 6 hospitals in the western Cape during the latter half of 1992 to determine whether these practices had improved subsequent to the February 1991 resolution of the Health Matters Committee (HMC) on immunisation in hospitals, and since a similar study was undertaken in 1990. Exit interviews were conducted with the escorts of all children aged 3-59 months who attended the study hospitals on the days designated for the study. In the second study, 88 of the 311 children studied (28.3%) were in need of immunisation on arrival, but only 12 of the 88 (13.6%) were immunised during the hospital visit. There was no evidence of an increase in requests to see children's Road-to-Health cards (37.1% compared with 35.2% previously). The incidence of missed opportunities for measles immunisation in children aged 6-59 months remained unacceptably high (51.4% compared with 63.7% previously, when a strict definition was used; and 15.7% compared with 18.1% previously, when a lenient definition was used). Health authorities at all levels need to take urgent action to address the problem of missed opportunities for immunisation at hospitals.  相似文献   
4.
5.
6.
7.
Mobile gene elements associated with integrons, including as gene cassettes, have been proposed to play an important role in bacterial evolution by providing an extensive genetic resource. This study hypothesized that critical genes for enzymes involved in EBPR systems, including those involved in polyphosphate, PHA and glycogen synthesis, may be present in mobile gene cassettes. Although no such genes were identified in any of the functional and deteriorated enhanced biological phosphorus removal (EBPR) laboratory-scale SBR systems examined here, many of the open reading frames (ORFs) remained unidentified because of the incompleteness of publicly available databases. An ORF of unknown function (SBR6-2) was encountered in deteriorated EBPR system with an unexpectedly high frequency, comprising 35% of the gene cassette-associated sequences for that system.  相似文献   
8.
Ion exchanged CoNaY was sulfided at 473 and 673 K and subsequently heated in He at 673 and 773 K. The resulting samples were characterized by means of overall sulfur analysis, temperature programmed Ar treatment and Fourier transform infrared spectroscopy. It was shown that during He flushing at sufficiently high temperature a protolysis reaction occurs resulting in the decomposition of Co sulfide into Co2+ ions and H2S.  相似文献   
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