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   7217篇
  免费   108篇
  国内免费   17篇
电工技术   370篇
综合类   5篇
化学工业   1327篇
金属工艺   229篇
机械仪表   154篇
建筑科学   106篇
能源动力   211篇
轻工业   515篇
水利工程   33篇
石油天然气   6篇
无线电   668篇
一般工业技术   1245篇
冶金工业   1812篇
原子能技术   146篇
自动化技术   515篇
  2023年   28篇
  2022年   69篇
  2021年   113篇
  2020年   60篇
  2019年   56篇
  2018年   93篇
  2017年   88篇
  2016年   90篇
  2015年   81篇
  2014年   120篇
  2013年   258篇
  2012年   236篇
  2011年   306篇
  2010年   201篇
  2009年   248篇
  2008年   264篇
  2007年   252篇
  2006年   235篇
  2005年   219篇
  2004年   207篇
  2003年   192篇
  2002年   194篇
  2001年   170篇
  2000年   140篇
  1999年   180篇
  1998年   679篇
  1997年   422篇
  1996年   310篇
  1995年   224篇
  1994年   213篇
  1993年   176篇
  1992年   99篇
  1991年   98篇
  1990年   92篇
  1989年   84篇
  1988年   77篇
  1987年   63篇
  1986年   72篇
  1985年   87篇
  1984年   57篇
  1983年   64篇
  1982年   47篇
  1981年   53篇
  1980年   53篇
  1979年   34篇
  1978年   24篇
  1977年   59篇
  1976年   57篇
  1975年   31篇
  1973年   24篇
排序方式: 共有7342条查询结果,搜索用时 15 毫秒
11.
The complexity of many chemical and refining reaction systems and the thus-derived tedious and time-consuming process of building the associated kinetic models have been major obstacles in the use of fundamental kinetics in the solution of chemical engineering problems. This review summarizes work aimed at removing theses obstacles. Our recent work that has led to the enhancement of the Kinetic Modeler's Toolbox (KMT) and the development of the Kinetic Model Editor (KME) presents an end-to-end solution to the kinetic modeling process, including automated feedstock modeling, reaction network construction, kinetic rate estimation, model programming, process system configurations, model customizations, compilations, model execution and results analysis.  相似文献   
12.
The authors present a real-time database system capable of collecting and delivering a large amount of information accurately at a high speed and by a simple method. This system has a microprocessor unit (MPU) for each private communication line around the main memory and coordinates the independent parallel operation for a number of these MPUs with the main memory access operation, using a fixed cyclic scan method and having all the MPUs perform multi-operation. Many advantages can be expected when this method is adopted, especially for the monitoring and control of power systems. Degradation of the system can be avoided during an information rush due to accidents, and it can be easily extended when adding to or expanding the power facilities in the future. Excellent daily maintainability can be assured, and a low overall cost can be expected  相似文献   
13.
The demand for energy in Japan is expected to increase steadily into the future, and it seems that the importance of nuclear power generation will be heightened more when the situation of our country which is not rich in energy resources is taken into account.

Furthermore, when we consider the present situation that the light water reactors have become common, recent outlook for the supply and demand for uranium resources, trends in the development of the fast breeder reactor technology, etc., the light water reactors are expected to remain dominant in the nuclear power generation of our country until at least the second half of the 21st century.

Based on such a background five PWR utilities in Japan (Hokkaido, Kansai, Shikoku, Kyushu, and the Japan Atomic Power), and Mitsubishi Heavy Industries, Ltd. have jointly started researching the Next Generation PWR which is expected to be the leading nuclear power plant taking place of APWR.  相似文献   

14.
Using a Debye function analysis, the presence of icosahedral and face centered cuboctahedral gold in a 1 1 ratio has been found in freshly prepared Au/Mg(OH)2 catalyst. The results support earlier studies which suggest the icosahedral form to be more stable at small nanometer sizes. Interactions between the gold and the Mg(OH)2 support appear to be weak, with the gold rapidly coagulating over a period of three months. Re-analysis of the aged sample shows the gold to be mainly in the form of truncated decahedra.  相似文献   
15.
利用高速气流冲击法进行粉体/粉体系表面改性技术,是迄今为止各种粉体材料开发中最为引人注目的技术之一。HYBRIDIZATION(下称HYB)系统是利用高速气流冲击法对微粉体进行干式/机械化处理,是使材料复合化的最实用的装置,可对各类有机物、无机物、金属等进行广泛组合,通用性很强,适用于许多行业领域。从本文所述的系统构成、型式,有关的典型球形化处理的运转特性,利用复合化高温粉体测定被处理粉体表面温度,利用颜料改变色调等的处理特点及该系统的适用性等(一部分是从已发表的学术论文及专利上摘录的),可以说明HYB系统的概况。  相似文献   
16.
17.
A new technique combining a thermal-image furnace and a twin roller is described for quenching the melt to form glass. The technique was applied to the simple system Li2O-SiO2, since its fundamental parameters in the estimation of critical cooling rate are available. Glass flakes were obtained in the composition Li4SiO4, for which a very large critical cooling rate (∼109 K·s−1) was needed for glass formation.  相似文献   
18.
Polytetramethylene glycol (molecular weight range 1000–8000) was prepared by the polymerization of tetrahydrofuran (THF) using a binary catalyst system of fuming sulfuric acid and perchloric acid. When 28% fuming sulfuric acid alone was used as the catalyst, the average molecular weight of polymer was low, the maximum value being 1000–1100. By the combination of fuming sulfuric acid with a small amount of perchloric acid, the average molecular weight of the polymer was increased to about 8000. Furthermore, the molecular weight was readily controlled in the range of 1000 to 8000 by varying the amount of the binary catalyst.  相似文献   
19.
The minimum sequence lengths (nc) of vinyl acetate (VAc) units necessary to form a colored iodine complex were determined to be 4 and 17 for radically polymerized VAc/vinyl propionate (VPr) and VAc/isopropenyl acetate (IPAc) copolymers, respectively. The iodine affinities (I/VAc) of VAc/VPr copolymers (SP-series) obtained by propionylation of partially saponified polyvinyl acetate (PVAc) were remarkably affected by the saponification conditions. An increase of the water content in acetone/water mixture as saponification solvent brought about a decrease of the iodine affinities of the SP-series. The dependence of the iodine affinity on the saponification of monomer units in the SP-series was compared with that in the radically polymerized VAc/VPr copolymers by taking the sequence probability as the measure of monomer unit distribution. The results strongly supported an occurence of the slide fastener reaction at high degrees of saponification, which was well-known in the saponification of PVAc. Furthermore, it was found that the saponification mode of PVAc at low degrees of saponification was influenced uniquely by the water content in saponification solvents and the saponification temperature.  相似文献   
20.
Temperature dependence of KIC values for Si3N4 bodies sintered at high pressures without additives was studied from room temperature to 1400°C. Little change in KK was found in this range.  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