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   2587篇
  免费   121篇
  国内免费   205篇
电工技术   18篇
综合类   95篇
化学工业   850篇
金属工艺   45篇
机械仪表   63篇
建筑科学   29篇
矿业工程   144篇
能源动力   23篇
轻工业   736篇
水利工程   3篇
石油天然气   45篇
武器工业   4篇
无线电   76篇
一般工业技术   58篇
冶金工业   151篇
原子能技术   165篇
自动化技术   408篇
  2024年   7篇
  2023年   14篇
  2022年   24篇
  2021年   38篇
  2020年   47篇
  2019年   51篇
  2018年   44篇
  2017年   58篇
  2016年   55篇
  2015年   61篇
  2014年   107篇
  2013年   186篇
  2012年   151篇
  2011年   154篇
  2010年   151篇
  2009年   122篇
  2008年   130篇
  2007年   164篇
  2006年   183篇
  2005年   100篇
  2004年   119篇
  2003年   130篇
  2002年   135篇
  2001年   93篇
  2000年   61篇
  1999年   77篇
  1998年   60篇
  1997年   54篇
  1996年   59篇
  1995年   42篇
  1994年   27篇
  1993年   34篇
  1992年   37篇
  1991年   27篇
  1990年   14篇
  1989年   19篇
  1988年   17篇
  1987年   18篇
  1986年   17篇
  1985年   8篇
  1984年   8篇
  1983年   5篇
  1982年   5篇
排序方式: 共有2913条查询结果,搜索用时 15 毫秒
11.
新疆茶藨中紫红色素的萃取工艺及稳定性研究   总被引:4,自引:1,他引:3  
本文介绍了新疆野生植物茶子果实中,紫红色素提取及定性检验和色素的提取工艺。  相似文献   
12.
《Chemical engineering science》2002,57(18):3831-3838
A semi-batch extraction process of anthocyanins was studied in a packed bed. Methanol was used as solvent and the raw material studied consisted of skins of the tempranillo grape, which was obtained from the pomace from red wine vinification. The results show large diffusional effects due to strong control from the mass transfer. The best results were obtained using a high temperature and a high flow rate. A penetration model is proposed in terms of a bed of spherical particles. The model provides a value for the diffusion coefficient of the solute within the solid matrix. It can be seen that the adjustment of the model is satisfactory and that it is able to predict, to a reasonable extent, the yield of the extraction process.  相似文献   
13.
A continuous process for the extraction of sunflower oil using supercritical CO2, featuring multiple extractors, one oil separator and three cascaded CO2 recovery vessels operating at different pressures, was devised and studied. For every single equipment of the plant making up the process a mathematical model was built. Experimental tests—consisting in measurements of oil solubility in supercritical CO2—were carried out in a laboratory-scale apparatus to characterise the behaviour of sunflower oil in the separation from the supercritical fluid. The mathematical model of the whole process was coded in the commercial gPROMS process modelling environment where both its simulation and optimisation—this latter assuming the overall oil production cost as the objective function—were carried out. The process- and economics-related results are discussed and compared with those obtained with traditional and cold-pressing extraction.  相似文献   
14.
In a previous study a solvent mixture of heptane containing 40 mass % heptanol was selected as an alternative in the industrial extraction of caprolactam to replace benzene, toluene, or chlorinated hydrocarbons. This work reports the equilibrium distribution ratio of caprolactam and four model impurities of organic nature, namely, cyclohexanone, aniline, n‐methylcaprolactam, and cyclohexane‐carboxamide, comparing the mixed solvents with toluene as a reference. The resulting phase equilibria were interpreted using the equilibrium stage model. Based on these calculations it was found that, compared to toluene, the co‐extracted fraction of cyclohexanone and aniline was higher, that of n‐methylcaprolactam was comparable, and that of cyclohexane‐carboxamide was lower using the mixed solvent. Overall, the mixed solvent reduced the fraction of co‐extracted impurities by almost 10 %.  相似文献   
15.
间苯二酚溶剂萃取液液相平衡研究   总被引:4,自引:0,他引:4  
测定了“醋酸正丁酯-间苯二酚(溶质)-盐水(含0.2质量分率NaCl)”三元系在24℃、101.33kPa下的液液相平衡数据并给出了三角相图,用Hand公式对相平衡数据进行了关联,获得了可供工业连续萃取过程设计使用的关联式。本研究将醋酸正丁酯和正丁醇作为溶剂萃取间苯二酚进行了对比,并指出:醋酸正丁酯优于正丁醇。  相似文献   
16.
An integrated process based on simultaneous solid-liquid extraction and liquid membrane separation is proposed for recovery and isolation of valuable species from botanicals. This integration provides complete exhausting of the solid material even in the case of very low solubility of the specified solute in the extracting solvent. Selectivity of the liquid membrane ensures a preferential transport of the desired solute from the native extract into the strip solution, while the other co-extracted species remain predominantly in the native extract.  相似文献   
17.
Four monoalkyl esters of isoalkylphosphonic acids have been studied for the chromatographic separation ofrare earths (RE).The relationship between distribution ratios and acid concentration of the eluants forsamarium and ytterbium has been explored.The characteristics of these extractants loaded onto macroreticularpoly (methyl methacrylate) resin beads for the separation of lanthanum,cerium,praseodymium and neodymiumhave been compared.Among the extractants studied,mono(1-methylheptyl) ester of isooctylphosphonic acidwas found to be the best for RE separation.The acidity for separation is lower than any known P-containingextractants for the same purpose.For instance,with 1.73 mol·L~(-1) nitric acid as eluent,thulium,ytterbium andlutetium can be separated quantitatively.The extractant-loaded resins possess high column efficiency with goodkinetic characteristics.The extraction mechanism was also explored.  相似文献   
18.
豆粕中大豆异黄酮提取工艺的优化   总被引:7,自引:1,他引:6  
采用乙醇回流浸提和HCl水解两步法,从大豆豆粕中提取大豆异黄酮类化合物,以染料木素为标准物,在紫外区对异黄酮含量进行测定。通过正交试验确定最佳提取工艺。本实验平均回收率为95.7%。  相似文献   
19.
应稀土化学发展的需要,我们组建了稀土萃取信息系统。其中包括:数据的来源和数据类型;数据的组织;检索功能;数据间的关联;最优化设计以及萃取剂结构与其物理性质和结构与萃取性能的相关分析研究。  相似文献   
20.
磷酸异戊酯萃取U,Np,Pu性能的研究   总被引:1,自引:0,他引:1  
测定磷酸异戊酯(TiAP)对U(Ⅵ)、Np(Ⅳ)、Np(Ⅴ)、Np(Ⅵ)、Pu(Ⅳ)和Pu(Ⅲ)的萃取性能及对Th(代替Pu)的萃取容量。研究了二乙三胺五乙酸(DTPA)络合剂对上述核素形成配合物的条件。结果表明,在用TBP和TiAP作萃取剂时,可用DTPA络合Np(Ⅵ)、Pu(Ⅲ).从而改善乏燃料后处理中U产品对Np、Pu和Pu产品对Np的去污。  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