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   444589篇
  免费   6725篇
  国内免费   2343篇
电工技术   9044篇
技术理论   5篇
综合类   1289篇
化学工业   66965篇
金属工艺   17464篇
机械仪表   12578篇
建筑科学   10398篇
矿业工程   2308篇
能源动力   9970篇
轻工业   39689篇
水利工程   4469篇
石油天然气   8274篇
武器工业   252篇
无线电   52056篇
一般工业技术   82991篇
冶金工业   91470篇
原子能技术   8605篇
自动化技术   35830篇
  2021年   3846篇
  2020年   2792篇
  2019年   3556篇
  2018年   5681篇
  2017年   5616篇
  2016年   5983篇
  2015年   4481篇
  2014年   7229篇
  2013年   19257篇
  2012年   12127篇
  2011年   15962篇
  2010年   12845篇
  2009年   14147篇
  2008年   15143篇
  2007年   15256篇
  2006年   13588篇
  2005年   12178篇
  2004年   11405篇
  2003年   10840篇
  2002年   10607篇
  2001年   10990篇
  2000年   10235篇
  1999年   10806篇
  1998年   28013篇
  1997年   19432篇
  1996年   14821篇
  1995年   10920篇
  1994年   9718篇
  1993年   9654篇
  1992年   6932篇
  1991年   6588篇
  1990年   6586篇
  1989年   6407篇
  1988年   5977篇
  1987年   5008篇
  1986年   5109篇
  1985年   5719篇
  1984年   5334篇
  1983年   4851篇
  1982年   4384篇
  1981年   4720篇
  1980年   4214篇
  1979年   4245篇
  1978年   4140篇
  1977年   4674篇
  1976年   6193篇
  1975年   3654篇
  1974年   3472篇
  1973年   3426篇
  1972年   2941篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Quahabi  A. Lacoume  J.L. 《Electronics letters》1991,27(16):1430-1432
The aim of this letter is to derive the spectral density of decimated processes, and to establish their model when they are generated from ARMA processes. The optimal conditions of decimation are also discussed.<>  相似文献   
992.
Progress in modelling air flow patterns in timber kilns using Computational Fluid Dynamics is reviewed in this work. These simulations are intended to predict the distribution of the flow in the fillet spaces between boards in a hydraulic model of a timber kiln. Here, the flow regime between the boards is transitional between laminar and turbulent flow, with Reynolds numbers of the order of 5000. Running the simulation as a transient calculation has shown few problems with convergence issues, reaching a mass residual of 0.2% of the total inflow after 40-100 iterations per time step for time steps of 0.01 s. Grid sensitivity studies have shown that non-uniform grids are necessary because of the sudden changes in flow cross section, and the flow simulations are insensitive to grid refinement for non-uniform grids with more than 300,000 cells. The best agreement between the experimentally-measured flow distributions between fillet spaces and those predicted by the simulation have been achieved for (effective) bulk viscosities between the laminar viscosity for water and ten times that value. This change in viscosity is not very large (less than an order of magnitude), given that effective turbulent viscosities are typically several orders of magnitude greater than laminar ones. This result is consistent with the transitional flows here.  相似文献   
993.
Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 3, pp. 34–35, March, 1992.  相似文献   
994.
995.
996.
997.
Mendeleev All-Union Metrology Research Institute. Translated from Atomnaya Énergiya, Vol. 73, No. 5, pp. 393–397, November 1992.  相似文献   
998.
999.
1000.
The filtration method for the evaluation of the RBC deformability has been further refined to simulate the deformations encountered in the recticuloendothelial system (in particular the spleen), a recognized site of aged and sickled cells removal. The core of the developed measuring system is a very thin (0.4 micron thick) filter that consists of single micropore (diameters down to 1 micron) on a Si3N4 film which has been constructed using silicon microfabrication techniques. Individual RBC's deformability is quantified measuring the cell pore passage time. From one blood sample 200 passage times are analyzed by a computer, displaying mean and median values as deformability indexes, and class and cumulative histograms for studying the passage times distribution. In this paper the effectiveness of the developed system as a routine clinical evaluation tool is demonstrated by studying several factors that are known to affect the RBC deformability, such as temperature, addition of diamide and glutaraldehyde, and blood storage conditions. In addition, it is experimentally demonstrated that the human RBC can traverse a pore with a diameter as small as 1 micron when the pore length is very short, thus broadening the experimental conditions under which the RBC deformability (fluidity) can be studied.  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