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   188篇
  免费   17篇
  国内免费   6篇
电工技术   2篇
综合类   12篇
化学工业   129篇
金属工艺   2篇
机械仪表   2篇
建筑科学   3篇
矿业工程   3篇
能源动力   2篇
轻工业   9篇
石油天然气   27篇
武器工业   1篇
无线电   1篇
一般工业技术   15篇
冶金工业   1篇
自动化技术   2篇
  2023年   2篇
  2022年   6篇
  2021年   7篇
  2020年   5篇
  2019年   5篇
  2018年   5篇
  2017年   4篇
  2016年   4篇
  2015年   7篇
  2014年   10篇
  2013年   11篇
  2012年   10篇
  2011年   17篇
  2010年   12篇
  2009年   8篇
  2008年   7篇
  2007年   11篇
  2006年   6篇
  2005年   13篇
  2004年   6篇
  2003年   10篇
  2002年   4篇
  2001年   5篇
  2000年   2篇
  1999年   4篇
  1998年   5篇
  1997年   3篇
  1996年   9篇
  1995年   2篇
  1994年   3篇
  1993年   3篇
  1992年   1篇
  1991年   2篇
  1990年   2篇
排序方式: 共有211条查询结果,搜索用时 15 毫秒
1.
The main goal of this work is to evaluate the extraction of sunflower oil from enzyme-treated collets using ethanol and isopropanol (IPA) as solvents. The sunflower collets are pretreated with the multienzyme complex Viscozyme L prior to solvent extraction by the Soxhlet method. The influence of the moisture content of the collets, pretreatment, processing time, and solvent type on the amount of total extracted material and the oil extraction efficiency is studied. Some quality parameters such as phospholipid content of the oil and chlorogenic acid content of the residual meal are also analyzed. At low moisture content (7%) the solvents exhibit similar oil extraction ability (98–99%), but with increasing moisture the extraction efficiency of ethanol decreases to about 85%, while no significant differences are observed for IPA. The enzymatic treatment increases the extraction efficiency for all times, especially for ethanol. It is observed that IPA is more efficient in the extraction compared to ethanol, and the amount of nonlipid material is reduced by ≈70%. In addition, the oil extracted with IPA have lower phospholipid content and the residual meal presents a higher chlorogenic acid content. Practical Applications:This work would contribute toward the use of green solvents in the extraction of sunflower oil from collets. Ethanol and isopropanol, used as solvents, present attractive advantages, including low toxicity, good operational security, as well as being obtained from a renewable source. The obtained data provide up-to-date information on the use of these alcohols in the extraction of sunflower oil from collets and the influence of operating conditions, such as moisture content, enzymatic pretreatment of the collets, and the extraction time. Information about oil and meal quality is also reported.  相似文献   
2.
Ethanol vapor deactivation of gossypol in cottonseed meal   总被引:3,自引:0,他引:3  
Most cottonseed cultivars contain gossypol, a polyphenolic antinutritional compound. “Free” gossypol is a physiologically active form of gossypol, which is toxic to young- and nonruminant animals. To utilize solvent-extracted cottonseed meal as a general feed, gossypol must be either removed or deactivated to a minimum level specified for each class of animal. Normally, deactivation is carried out prior to oil extraction; however, the desired level of deactivation is not always attained. A new supplemental method of deactivation has been found by using either ethanol or isopropanol vapors on solventextracted meal. In a bench-top set-up, ethanol vapor reduced free gossypol from 0.115 to 0.053%, and a further reduction to 0.026% has been observed with the addition of ferrous sulfate. The supplemental deactivation method can, in most cases, reduce free gossypol to significantly safer levels for feeding, thus increasing utility, and possibly demand, for cottonseed meal as a general animal feed protein source. Presented in part at the AOCS Annual Meeting, Atlanta, GA, May 8–12, 1994.  相似文献   
3.
Utilization of lipids containing eicosapentaenoic acid (EPA) produced by microorganisms requires processes for their efficient recovery from microbial cells. Recovery of EPA from mycelia of the fungusPythium irregulare by solvent extraction with hexane-isopropanol (HIP) in a pilot-plant colloid mill was investigated. Extraction efficiencies of 96% for lipid and EPA were achieved with a 3∶2 (vol/vol) HIP mixture by milling wet, filtered mycelia for 5 min at a solvent/dry solids ratio of 100 L/kg. The process yielded a crude extract that contained up to 96% lipid and an EPA content as high as 24% (with no selectivity for EPA).  相似文献   
4.
A series of NbO x /ZrO2 catalysts containing up to 2.67wt Nb (ca. 80 nominal surface coverage) was prepared by incipient wetness impregnation from niobium oxalate and oxalic acid solution. The structure of the catalysts was monitored by X-ray diffraction and Raman spectroscopy. The results indicated the presence of a surface Nb phase. No evidence for the formation of crystalline Nb2O5 species was found. The development of the acidity as a function of Nb loading was monitored by adsorption of a basic probe molecule followed by infrared spectroscopy. The results indicated the appearance of Brnsted acid sites for a threshold of Nb loading. The abundance of Brnsted acid sites correlated well with the isopropanol dehydration activity. The overall behavior was very similar to that reported earlier for the WO x /ZrO2 system.  相似文献   
5.
Diffuse reflectance Fourier transform infrared spectroscopy was used to study the mode of adsorption of phosphatidylcholine (PC) in hexane onto silicic acid (SA). PC adsorption was mainly through the charged phosphate group with minimal binding through the ester carbonyl. When the SA surface with adsorbed PC is washed with hexane, containing a small concentration of isopropanol, the desorbed PC is recovered without structural change, i.e., there is no evidence of PC hydrolysis in the adsorption process. Adsorbent misture probably promotes PC adsorption due to the increased availability of surface water hydroxyl groups for interaction with the PC phosphate groups. Isopropanol promoted PC binding by destabilizing PC reverse miscelles in solution, thus promoting its adsorption.  相似文献   
6.
The series of compounds La2–xSrxNiO4±y (0.0 x 1.0) crystallising in tetragonal K2NiF4 structure were prepared and catalytic activity have been investigated using isopropanol decomposition as model reaction. All the catalyst compositions catalyse only the dehydrogenation of isopropanol reaction. The composition La1.5Sr0.5NiO4 showed high activity compared to other compositions in the series. The composition is unique not only in catalytic property but also in other physical properties like structural characteristics, electrical resistivity and metal to semiconductor transition.  相似文献   
7.
异丙醇-异丙醚形成二元共沸物,一般精馏方法很难分离.利用化工过程软件Aspen Plus,在异丙醇和异丙醚产物的摩尔分数达到0.999的条件下,以乙二醇为溶剂的萃取精馏流程和热集成变压精馏流程对异丙醇-异丙醚混合物分离进行模拟.以全年总费用最低为目标,确定萃取精馏流程两塔的理论板数、进料位置和溶剂进料位置以及热集成变压精馏流程的高压塔操作压力,两塔的理论板数,进料位置,得到两种流程的最优操作条件.从模拟结果可知,对于异丙醇-异丙醚混合物的分离,热集成变压精馏所需的全年总费用更低,比萃取精馏的全年总费用降低了10.86%.对于该混合物,热集成变压精馏流程要优于萃取精馏流程.  相似文献   
8.
用循环伏安和积分电量法来研究甲醇和异丙醇在Pt和Pd电极上电化学氧化活性。异丙醇在Pt和Pd电极上起峰电位和峰电位比甲醇的相应值负,这个结果说明在低电位异丙醇比甲醇更容易电化学氧化。虽然异丙醇在Pt电极上低电位时容易电化学氧化,但高电位氧化能力比不上甲醇。在Pd电极上无论低电位还是高电位异丙醇氧化能力都比甲醇好。甲醇氧化活性在Pt电极上比在Pd电极上的好,异丙醇氧化活性在Pd电极上比在Pt电极上有更优秀的表现。  相似文献   
9.
异丙醇是一种应用广泛的有机溶剂和化工原料,介绍了合成异丙醇生产技术路线,综合比较了丙酮加氢路线和丙烯水合路线的经济性,并分析了异丙醇的应用前景.丙酮加氢制异丙醇路线更具有经济性,异丙醇应用领域需进一步拓展.  相似文献   
10.
Porous thin‐sheet cobalt–copper–manganese mixed oxides modified microfibrous‐structured ZSM‐5 coating/PSSF catalysts were developed by the papermaking/sintering process, secondary growth process, and incipient wetness impregnating method. Paper‐like sintered stainless steel fibers (PSSF) support with sinter‐locked three‐dimensional networks was built by the papermaking/sintering process, and ZSM‐5 coatings were fabricated on the surface of stainless steel fibers by the secondary growth process. Catalytic combustion performances of isopropanol at different concentrations over the microfibrous‐structured Co–Cu–Mn (1:1:1)/ZSM‐5 coating/PSSF catalysts were measured to obtain kinetics data. The catalytic combustion kinetics was investigated using power–rate law model and Mars–Van Krevelen model. It was found that the Mars–Van Krevelen model provided fairly good fits to the kinetic data. The catalytic combustion reaction occurred by interaction between isopropanol molecule and oxygen‐rich centers of modified microfibrous‐structured ZSM‐5 coating/PSSF catalyst. The reaction activation energies for the reduction and oxidation steps are 60.3 and 57.19 kJ/mol, respectively. © 2014 American Institute of Chemical Engineers AIChE J, 61: 620–630, 2015  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