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   648739篇
  免费   7325篇
  国内免费   2122篇
电工技术   12001篇
综合类   587篇
化学工业   98123篇
金属工艺   27914篇
机械仪表   21040篇
建筑科学   14167篇
矿业工程   4432篇
能源动力   16829篇
轻工业   50228篇
水利工程   7510篇
石油天然气   15510篇
武器工业   54篇
无线电   72730篇
一般工业技术   133818篇
冶金工业   115926篇
原子能技术   15715篇
自动化技术   51602篇
  2021年   6007篇
  2020年   4438篇
  2019年   5782篇
  2018年   10055篇
  2017年   10245篇
  2016年   10750篇
  2015年   6773篇
  2014年   11442篇
  2013年   29859篇
  2012年   17766篇
  2011年   24126篇
  2010年   19438篇
  2009年   21813篇
  2008年   22151篇
  2007年   22018篇
  2006年   19221篇
  2005年   17366篇
  2004年   16508篇
  2003年   16099篇
  2002年   15364篇
  2001年   15162篇
  2000年   14485篇
  1999年   14511篇
  1998年   35052篇
  1997年   24929篇
  1996年   19441篇
  1995年   14536篇
  1994年   13129篇
  1993年   12789篇
  1992年   9619篇
  1991年   9387篇
  1990年   9236篇
  1989年   8828篇
  1988年   8436篇
  1987年   7438篇
  1986年   7270篇
  1985年   8135篇
  1984年   7354篇
  1983年   7017篇
  1982年   6363篇
  1981年   6468篇
  1980年   6088篇
  1979年   6130篇
  1978年   6004篇
  1977年   6632篇
  1976年   8518篇
  1975年   5351篇
  1974年   5148篇
  1973年   5202篇
  1972年   4451篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
991.
We have assessed the antimicrobial, vapor-phase activity of the following natural essential oils (EOs) when used in paraffin-based “active coatings” for paper packaging materials intended to come into contact with foods: clove (Sygzium aromaticum), cinnamon (Cinnamomum zeylanicum), and oregano (Origanum vulgare) EOs, and cinnamaldehyde-enriched cinnamon EO. To our knowledge, this is the first time that such an approach has been presented for consideration by the scientific community.  相似文献   
992.
993.
Analytical ultracentrifugation is commonly used for the determination of molecular weights (sedimentation equilibrium) and sedimentation coefficients (sedimentation rate) of biological macromolecules in solution. A Turbo Pascal program for the analysis of sedimentation equilibrium centrifugation data produced by absorbance optical systems is described. The user may enter data from a scan of absorbance versus distance from the centre of rotation, via a graphics tablet (or ASCII file). This is subsequently manipulated to yield an apparent weight average molecular weight for the given sample. Plots of ln (absorbance) versus (radius2) may also be produced. The method described uses readily available computational equipment requiring only a graphics tablet in addition to an IBM PC compatible computer. This technique and the software developed have been used to investigate the molecular weight range of two International Humic Substances Society (IHSS) reference samples from the Suwannee River.  相似文献   
994.
995.
The conclusions are put forward that are adopted by a discussion group preparing the framework for a limitation policy of the radon problem in Belgium. Existing and future situations are treated in a coherent policy that is adequate for practical implementation. An action level is defined, together with a hierachy of levels for new constructions. The decision logic for the acceptance of building materials is explained.  相似文献   
996.
On the basis of a numerical solution of the Stefan problem, the dynamics of nanosecond laser annealing of silicon is investigated.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 48, No. 2, pp. 306–312, February, 1985.  相似文献   
997.
998.
999.
We analyze the wear resistance of plasma coatings for a constant work of friction. The dependences of the wear resistance of the coatings are obtained for a broad range of loading conditions. It is shown that the minimum sensitivity to loading conditions is exhibited by the molybdenum coatings. It is also established that the wear resistance of the coatings decreases as the amplitude of displacements increases and the cyclic frequency of the tests decreases due to the intensification of fatigue processes on the surfaces. The comparative characteristics of coatings are presented. __________ Translated from Problemy Prochnosti, No. 5, pp. 94–100, September–October, 2007.  相似文献   
1000.
An innovative technology for industrial wastewater treatment has been developed. The main focus of the new system is a transformation of persistent organic compounds (biorecalcitrant COD) into a biodegradable fraction, followed by high efficient biological elimination using specialised bacteria's. To fulfill these targets the Aqua-Biomant process integrates two treatment steps: an aerated biological upflow filter and a electrochemical oxidation technique using boron doped-diamond electrodes. The advantages of the process are high efficient COD removal with reduced energy consumption combined with low total residence time.  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