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   567010篇
  免费   6235篇
  国内免费   1004篇
电工技术   10510篇
综合类   467篇
化学工业   90099篇
金属工艺   23339篇
机械仪表   18500篇
建筑科学   12541篇
矿业工程   4312篇
能源动力   14432篇
轻工业   45765篇
水利工程   6943篇
石油天然气   14961篇
武器工业   39篇
无线电   60286篇
一般工业技术   116253篇
冶金工业   95646篇
原子能技术   14684篇
自动化技术   45472篇
  2021年   5487篇
  2019年   5268篇
  2018年   9208篇
  2017年   9413篇
  2016年   9836篇
  2015年   6028篇
  2014年   10246篇
  2013年   26105篇
  2012年   15776篇
  2011年   21096篇
  2010年   16975篇
  2009年   18826篇
  2008年   19073篇
  2007年   18776篇
  2006年   16295篇
  2005年   14747篇
  2004年   14012篇
  2003年   13692篇
  2002年   13252篇
  2001年   12854篇
  2000年   12335篇
  1999年   12017篇
  1998年   27666篇
  1997年   20054篇
  1996年   15636篇
  1995年   12008篇
  1994年   10872篇
  1993年   10617篇
  1992年   8336篇
  1991年   8106篇
  1990年   7991篇
  1989年   7763篇
  1988年   7479篇
  1987年   6749篇
  1986年   6537篇
  1985年   7393篇
  1984年   6703篇
  1983年   6440篇
  1982年   5779篇
  1981年   5900篇
  1980年   5638篇
  1979年   5736篇
  1978年   5665篇
  1977年   6182篇
  1976年   7688篇
  1975年   5109篇
  1974年   4905篇
  1973年   4985篇
  1972年   4282篇
  1971年   4044篇
排序方式: 共有10000条查询结果,搜索用时 0 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