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   287609篇
  免费   3065篇
  国内免费   817篇
电工技术   5030篇
综合类   162篇
化学工业   45409篇
金属工艺   11896篇
机械仪表   8606篇
建筑科学   6846篇
矿业工程   1835篇
能源动力   6734篇
轻工业   25905篇
水利工程   3190篇
石油天然气   7087篇
武器工业   16篇
无线电   31448篇
一般工业技术   56934篇
冶金工业   51374篇
原子能技术   7532篇
自动化技术   21487篇
  2021年   2099篇
  2018年   3672篇
  2017年   3623篇
  2016年   3903篇
  2015年   2465篇
  2014年   4231篇
  2013年   12020篇
  2012年   6830篇
  2011年   9215篇
  2010年   7567篇
  2009年   8642篇
  2008年   8929篇
  2007年   8813篇
  2006年   7827篇
  2005年   7309篇
  2004年   6800篇
  2003年   6553篇
  2002年   6627篇
  2001年   6497篇
  2000年   6176篇
  1999年   6231篇
  1998年   14756篇
  1997年   11031篇
  1996年   8567篇
  1995年   6523篇
  1994年   5915篇
  1993年   5788篇
  1992年   4479篇
  1991年   4441篇
  1990年   4284篇
  1989年   4301篇
  1988年   4255篇
  1987年   3598篇
  1986年   3595篇
  1985年   4161篇
  1984年   3965篇
  1983年   3620篇
  1982年   3422篇
  1981年   3558篇
  1980年   3422篇
  1979年   3365篇
  1978年   3445篇
  1977年   3923篇
  1976年   5037篇
  1975年   3158篇
  1974年   3007篇
  1973年   3024篇
  1972年   2651篇
  1971年   2473篇
  1970年   2104篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
A model of contact thermolysis was constructed based on a combined set of equations for heat transfer from a magmatic intrusion to a coal bed and the kinetics of thermal coal conversion. This model was illustrated by the generation of petroleum hydrocarbons deep in the earth by the thermolysis of the sapropelic matter of boghead.  相似文献   
132.
The contribution of an oil phase to the agglomeration mechanisms of food powders was evaluated. Maltodextrin (DE 10), palm oil stearin and two palm oil oleins (up to 25% dry mass) were used as food models. Granulation runs were carried out in a pilot plant steam jet agglomerator. The powders containing oleins were more cohesive than those with stearin and the presence of oil changed the agglomeration mechanisms. The size increase mechanism of pure maltodextrin powder was controlled by surface plasticization and agglomerates with suitable instant properties were obtained. Small amount of oil degenerated drastically the rate of dispersion in water of the powders and their agglomerates but the average size and the mechanical resistance of the agglomerates increased when the oil content of the powders increased. SEM micrographs of agglomerates indicated that higher lipid content in the powders produced compact granules, favoring sinkability but hindering their disintegration. Agglomeration enhanced considerably the flowability of the particles containing oil. The dispersion behavior of the powders with higher lipid content could be correlated with the Hausner Number. A pre-agglomeration step favored the blend of the more cohesive powders producing larger and more resistant agglomerates.  相似文献   
133.
The possibility of processing fluorine-containing wastes of fluorite ore, which include fluorite, calcite, quartz, and anorthite, has been investigated. A manufacturing flow chart of the complex processing of the ore waste materials with the production of sodium fluoride, alumina, soda ash, and raw materials suitable for the production of Portland cement and wollastonite is suggested.  相似文献   
134.
Characteristic mineral assemblage and special features of the composition of Au and Ag sulfides of gold-silver deposits have been established. The forms of the occurrence of Au and Ag in the minerals of the early and last stages have been analyzed. The conditions for the formation of uytenbogaardtite and petrovskaite in supergene and low-temperature hydrothermal processes have been considered. A thermodynamic model explaining their genesis in the oxidation zones is presented.  相似文献   
135.
The results of theoretical and experimental studies for the kinetics of separating dichlorosilane from a mixture of volatile chlorosilanes and ultrapurifying the dichlorosilane concentrate by batch distillation are reported. A mathematical model of the process is proposed. It is shown that the model and computational algorithm adequately describe both processes. The obtained experimental and theoretical data made it possible to design a concentration and ultrapurification process with a maximal productivity at a specified product purity.  相似文献   
136.

Background  

Bioelectrical Impedance (BIA) derived phase angle is increasingly being used as an objective indicator of nutritional status in advanced cancer. Subjective Global Assessment (SGA) is a subjective method of nutritional status. The objective of this study was to investigate the association between BIA derived phase angle and SGA in advanced colorectal cancer.  相似文献   
137.
138.
Some 100 years before Albert Munsell developed his color order system, French silk merchant and inventor of a technology for producing works of art in silk velours, Gaspard Grégoire, introduced a color order system based on the color attributes hue, (relative) chroma, and lightness. Conceived in the mid‐1780s, an atlas with 1350 samples was produced before 1813 and found use in French Royal manufacturing operations and educational institutions. It was followed a few years later by one with 343 samples. Grégoire's work was subsequently overshadowed by Michel‐Eugene Chevreul's more complicated and less intuitive hemispherical system of 1839. © 2007 Wiley Periodicals, Inc. Col Res Appl, 33, 5–9, 2008  相似文献   
139.
140.
The maximum-likelihood technique is applied to determine the coordinates of moving targets in a three-dimensional bistatic forward-scattering radar. The potential accuracy of the coordinates’ determination is estimated. Simulation results are presented.  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