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   325797篇
  免费   4909篇
  国内免费   858篇
电工技术   5637篇
综合类   225篇
化学工业   53878篇
金属工艺   12791篇
机械仪表   9378篇
建筑科学   8583篇
矿业工程   2251篇
能源动力   7567篇
轻工业   29345篇
水利工程   3489篇
石油天然气   7342篇
武器工业   16篇
无线电   33889篇
一般工业技术   64461篇
冶金工业   57250篇
原子能技术   7876篇
自动化技术   27586篇
  2021年   2779篇
  2019年   2525篇
  2018年   4582篇
  2017年   4488篇
  2016年   4949篇
  2015年   3300篇
  2014年   5421篇
  2013年   14768篇
  2012年   8397篇
  2011年   11158篇
  2010年   9120篇
  2009年   10166篇
  2008年   10685篇
  2007年   10501篇
  2006年   9238篇
  2005年   8525篇
  2004年   7810篇
  2003年   7553篇
  2002年   7597篇
  2001年   7220篇
  2000年   6778篇
  1999年   6815篇
  1998年   15270篇
  1997年   11572篇
  1996年   9124篇
  1995年   7061篇
  1994年   6443篇
  1993年   6273篇
  1992年   4958篇
  1991年   4763篇
  1990年   4719篇
  1989年   4708篇
  1988年   4607篇
  1987年   4038篇
  1986年   3962篇
  1985年   4679篇
  1984年   4494篇
  1983年   4062篇
  1982年   3841篇
  1981年   3924篇
  1980年   3764篇
  1979年   3754篇
  1978年   3779篇
  1977年   4184篇
  1976年   5280篇
  1975年   3450篇
  1974年   3242篇
  1973年   3281篇
  1972年   2824篇
  1971年   2594篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
33.
Theoretical Foundations of Chemical Engineering - New research results, as well as those published earlier by the authors, on the synthesis of azo compounds based on nitroanilines obtained by the...  相似文献   
34.
A hybrid sorbent material for removal of hydrogen sulfide from air was developed. The material is based on activated carbon and iron compounds obtained from waste iron(II) sulfate(VI) heptahydrate. The iron salt is deposited on the carbonaceous support and subjected to oxidation (Fe2+ to Fe3+) using atmospheric oxygen under alkaline conditions. An effect of H2O2 addition to the process on the composition of the resultant material was also examined. X-ray diffraction (XRD) analyses confirmed easy conversion of waste FeSO4·7H2O to iron oxides Fe3O4 and FeOOH. The activated carbon supporting iron oxides revealed a higher efficiency in H2S elimination from air compared to the commercial activated carbon, without any modification.  相似文献   
35.
Seed processing technologies are essential for seed safety and functionality through protection of physicochemical quality, pathogen inactivation, aflatoxin detoxification and alleviation of mutagenicity. Design of a pilot-scale unit of pulsed electric fields (PEF) to treat sesame seeds with respect to quality parameters, Aspergillus parasiticus inactivation and aflatoxin reduction as well as alleviation of aflatoxin mutagenicity were prompted in this study. PEF energy ranged from 0.97 to 17.28 J achieved maximum reductions of peroxide value and acidity number of 67.4 and 85.7%, respectively, and did not change color L*, a*, b* and hue values. A 60% reduction of A. parasiticus counts occurred at the maximum PEF energy. Aflatoxins G1, G2, B1, and B2 contents decreased by 94.7, 92.7, 86.9, and 98.7%, respectively. Except for the samples treated by 2.16 J with 100 μg/plate and by 6.80 J with 10 μg/plate, PEF treatment provided elimination of aflatoxin mutagenity. It is concluded that PEF treatment can be used to treat sesame seeds with preservation of physicochemical properties, inactivation of A. parasiticus and decomposition of aflatoxins with reduced mutagenicity.  相似文献   
36.
Theoretical Foundations of Chemical Engineering - The extraction of nitric and oxalic acids by neutral compounds TBP, DBBP, and TBPO have been studied. The optimal conditions of their separation...  相似文献   
37.
Neural Computing and Applications - This study presents the design of a tenth-order multiple feedback Chebyshev low-pass filter (MF-C-LPF). Component selection and gain calculation of filters are...  相似文献   
38.
This paper presents the results of ongoing research carried out by the author exploring methods to provide a more robust estimate of rock mass properties specifically for use in tunnel design. Data from various large-scale rock mass failures are introduced, including coal pillars. The damage-initiation,spalling-limit approach is compared to the coal pillar database. New comparisons of estimating the geological strength index(GSI) and relationships to estimate the Hoeke Brown failure criterion parameters, mb, s and a, are presented.  相似文献   
39.
40.
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