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   179篇
  免费   6篇
  国内免费   4篇
电工技术   2篇
化学工业   43篇
金属工艺   1篇
机械仪表   6篇
建筑科学   1篇
能源动力   28篇
轻工业   15篇
水利工程   2篇
石油天然气   2篇
无线电   17篇
一般工业技术   31篇
冶金工业   3篇
原子能技术   2篇
自动化技术   36篇
  2024年   2篇
  2023年   7篇
  2022年   12篇
  2021年   18篇
  2020年   10篇
  2019年   10篇
  2018年   23篇
  2017年   9篇
  2016年   9篇
  2015年   4篇
  2014年   8篇
  2013年   15篇
  2012年   11篇
  2011年   6篇
  2010年   7篇
  2009年   6篇
  2008年   10篇
  2007年   7篇
  2006年   9篇
  2005年   2篇
  2003年   1篇
  2001年   1篇
  1996年   1篇
  1959年   1篇
排序方式: 共有189条查询结果,搜索用时 15 毫秒
61.
Wireless Personal Communications - Recently, the Internet of Things (IoT) had emerged very rapidly and became the most important technology in today’s era. In an IoT-based environment, every...  相似文献   
62.
The challenges of an aging population require the adoption of in-home and medical technologies to complement the traditional caregiver model. Adoption of such technologies is, however, impinged by privacy concerns. This study investigates a four-dimensional framework that explains the trade-offs between functionality and privacy as constructed by older adults. The four dimensions constitute perceived utility, data granularity, data recipient, and activity sensitivity. We conducted a survey-based study to empirically examine the applicability and robustness of this framework. Our results have implications for the adoption of a wide range of privacy-enhancing technologies. By focusing on the intersection of an under-studied group (nontechnical older adults) and sensitive data (medical and at home), this work has the potential to enable privacy enhancing technologies (PETs) that might be widely adopted.  相似文献   
63.
One of the current challenges for application of PEM fuel cell is to find corrosion resistant, electrically conductive, light weight, cost competitive bipolar plate material. Low temperature carburization (LTC) of stainless steels is a novel, patented process by Swagelok Company. This paper addresses the corrosion resistance characteristics of LTC SS 316 for polymer electrolyte membrane fuel cell (PEMFC) bipolar plate applications. Corrosion properties of this material were studied using potentiodynamic and potentiostatic tests in simulated (1 M H2SO4 + 2 ppm HF, 0.5 M H2SO4, pH: 4.0, and 5% HCl + 5% Na2SO4) PEMFC conditions. LTC SS 316 showed excellent corrosion resistance in these conditions compared to SS 316. The mechanism of anodic dissolution and general corrosion of LTC SS 316 was observed to be similar to SS 316 however the extent of LTC SS 316 corrosion was less. LTC SS 316 showed corrosion currents well below 16 μA cm−2 in anodic and cathodic atmospheres under potentiostatic conditions. The potentiostatic current rapidly falls to ∼4.0 and ∼1.5 μA cm−2 under anodic and cathodic conditions, respectively. LTC SS 316 was observed to form a thinner oxide layer as compared to SS 316 after 24 h of potentiostatic testing. Moreover LTC SS 316 lowered the interfacial contact resistance by approximately 24% as compared to SS 316 after corrosion testing. Hence this study clearly states the performance advantage of using LTC SS 316 as bipolar plate material as compared to conventional materials.  相似文献   
64.
During the last couple of years, in the field of Natural Language Processing, UNL (i.e., Universal Networking Language) immense research activities have been witnessed. This paper illustrates UNLization of Punjabi Natural Language for UC-A1, UGO-A1, and AESOP-A1 with IAN (i.e., Interactive Analyzer) tool using X-Bar approach. This paper also discusses the UNLization process in depth, step-by-step with the help of tree diagrams and tables.  相似文献   
65.
The present study reports thermal and electrical properties of Zinc oxide (ZnO) nanoparticles prepared using co-precipitation route. Sudden dip in reaction temperature observed during the synthesis process created defects in the crystal lattice of ZnO which leads to reduction in crystallite size from 33?nm to 28?nm with increase in reaction temperature. This is confirmed by the X-ray diffraction studies. Thermal analysis of the samples shows better thermal stability for smaller nanoparticles. Temperature-dependent current-voltage characteristics of the ZnO samples show reduction in the conductivity and increase in dielectric constant with respect to rise in reaction temperature. Increase in dielectric constant with decrease in size of nanoparticles may be useful in the field of nanoelectronics like memory-storage devices, etc.  相似文献   
66.
67.
To prepare super water absorbent hydrogels of wood cellulose fibers, poly (methyl acrylate) (PMA) was copolymerized onto softwood sulfite pulp fibers using free radical initiator followed by alkaline hydrolysis. Ceric ammonium nitrate (CAN) was used as the free radical initiator. Effects of various parameters such as fiber concentration, monomer/pulp (M/pulp) ratio, CAN concentration, and reaction time on the grafting yield and on other grafting parameters were investigated. The graft conversion was the same from low to medium fiber concentration. The amount of initiator required was found to be independent of fiber concentration to achieve maximum grafting yield. Different fiber fractions (classified based on their length) have no effect on the grafting yield. The evidence of graft copolymerization was determined by using ATR‐IR spectroscopy. The X‐ray diffraction (XRD) analysis shows that grafting takes place both in amorphous and crystalline regions of cellulose fibers and the decrease in crystallinity of the grafted fibers with an increase in grafting yield was confirmed. The surface morphology of the PMA‐g‐cellulose was characterized by scanning electron microscopy (SEM). The water retention value of the hydrolyzed grafted pulp was determined based on a centrifugation technique. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007  相似文献   
68.
The kinetics of epoxidation of jatropha oil by peroxyacetic/peroxyformic acid, formed in situ by the reaction of aqueous hydrogen peroxide and acetic/formic acid, in the presence of an acidic ion exchange resin as catalyst in or without toluene, was studied. The presence of an inert solvent in the reaction mixture appeared to stabilise the epoxidation product and minimise the side reaction such as the opening of the oxirane ring. The effect of several reaction parameters such as stirring speed, hydrogen peroxide-to-ethylenic unsaturation molar ratio, acetic/formic acid-to-ethylenic unsaturation molar ratio, temperature, and catalyst loading on the epoxidation rate as well as on the oxirane ring stability and iodine value of the epoxidised jatropha oil were examined. The multiphase process consists of a consecutive reaction, acidic ion exchange resin catalysed peroxyacid formation followed by epoxidation. The catalytic reaction of peroxyacetic/peroxyformic acid formation was found to be characterised by adsorption of only acetic (or formic) acid and peroxyacetic/peroxyformic acid on the active catalyst sites, and the irreversible surface reaction was the overall rate determining step. The proposed kinetic model takes into consideration two side reactions, namely, epoxy ring opening involving the formation of hydroxy acetate and hydroxyl groups and the reaction of the peroxyacid and epoxy group. The kinetic and adsorption constants of the rate equations were estimated by the best fit using nonlinear regression method. Good agreement between experimental and predicted data validated the proposed kinetic model. From the estimated kinetic constants, the apparent activation energy for epoxidation reaction was found to be 53.6 kJ/mol. This value compares well with those reported by other investigators for the same reaction over similar catalysts.  相似文献   
69.
Epoxidation of karanja (Pongamia glabra) oil by H2O2   总被引:1,自引:0,他引:1  
Epoxidation of karanja oil (KO), a nondrying vegetable oil, was carried out with peroxyacetic acid that was generated in situ from aqueous hydrogen peroxide and glacial acetic acid. KO contained 61.65% oleic acid and 18.52% linoleic acid, respectively, and had an iodine value of 89 g/100 g. Unsaturated bonds in the oil were converted to oxirane by epoxidation. Almost complete epoxidation of ethylenic unsaturation was achieved. For example, the iodine value of the oil could be reduced from 89 to 19 by epoxidation at 30°C. The effects of temperature, hydrogen peroxide-to-ethylenic unsaturation ratio, acetic acid-to-ethylenic unsaturation ratio, and stirring speed on the epoxidation rate and on oxirane ring stability were studied. The rate constant and activation energy for epoxidation of KO were 10−6 L·mol−1·s−1 and 14.9 kcal·mol−1, respectively. Enthalpy, entropy, and free energy of activation were 14.2 kcal·mol−1, −51.2 cal·mol−1·K−1, and 31.1 kcal·mol−1, respectively. The present study revealed that epoxides can be developed from locally available natural renewable resources such as KO.  相似文献   
70.
Web archiving is the process of collecting portions of the Web to ensure that the information is preserved for future exploitation. However, despite the in  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