全文获取类型
收费全文 | 2176篇 |
免费 | 190篇 |
国内免费 | 55篇 |
专业分类
电工技术 | 19篇 |
综合类 | 84篇 |
化学工业 | 942篇 |
金属工艺 | 11篇 |
机械仪表 | 34篇 |
建筑科学 | 69篇 |
矿业工程 | 45篇 |
能源动力 | 45篇 |
轻工业 | 509篇 |
水利工程 | 24篇 |
石油天然气 | 413篇 |
武器工业 | 3篇 |
无线电 | 28篇 |
一般工业技术 | 135篇 |
冶金工业 | 36篇 |
原子能技术 | 5篇 |
自动化技术 | 19篇 |
出版年
2024年 | 5篇 |
2023年 | 21篇 |
2022年 | 34篇 |
2021年 | 82篇 |
2020年 | 62篇 |
2019年 | 65篇 |
2018年 | 57篇 |
2017年 | 57篇 |
2016年 | 72篇 |
2015年 | 82篇 |
2014年 | 117篇 |
2013年 | 232篇 |
2012年 | 175篇 |
2011年 | 182篇 |
2010年 | 122篇 |
2009年 | 97篇 |
2008年 | 113篇 |
2007年 | 123篇 |
2006年 | 88篇 |
2005年 | 85篇 |
2004年 | 83篇 |
2003年 | 54篇 |
2002年 | 61篇 |
2001年 | 57篇 |
2000年 | 56篇 |
1999年 | 25篇 |
1998年 | 32篇 |
1997年 | 34篇 |
1996年 | 20篇 |
1995年 | 33篇 |
1994年 | 18篇 |
1993年 | 14篇 |
1992年 | 15篇 |
1991年 | 12篇 |
1990年 | 8篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
排序方式: 共有2421条查询结果,搜索用时 15 毫秒
1.
2.
The separation of azeotropes has substantial energy and investment costs, and the available methods require high capital costs for reconstruction of process plants. As an alternative, a semicontinuous configuration that utilizes an existing plant with minor modifications has been explored. In this paper, a semicontinuous, heterogeneous azeotropic distillation process is proposed and acetic acid dehydration process is used as a case study. To carry out the simulation work, Aspen HYSYS® simulation software is used along with MATLAB® and an interface program to handle the mode-transition of the semicontinuous process. Sensitivity analyses on operating parameters are performed to identify the process limits. Comparisons are made to conventional heterogeneous azeotropic distillation, and dividing-wall distillation column on the annual cost. The results proved that the semicontinuous system is the best setup in terms of total annual costs and energy requirements. 相似文献
3.
4.
5.
Leying Qing Jiabo Tao Hongping Yu Peng Jiang Chongzhi Qiao Shuangliang Zhao Honglai Liu 《American Institute of Chemical Engineers》2020,66(6):e16938
Although ion dehydration in confined water is ubiquitous in many important processes concerning ion adsorption, transport and separation, and so forth, few theoretical models have been developed to unravel the mechanism of dehydration in confined space. Herein, a molecular model is proposed by weighing the molecular orientation of surrounding water within the first hydration shell, and then this model is applied to predict the hydration numbers and hydrated radii of simple ions with the help of molecular density functional theory. The predictions are rationalized not only with parallel simulations but also with relevant experimental measurements. We find that the ion hydration in confined water is depressed owing to the confinement, and thus the multilayer hydration shell is disturbed, which results in the decline of hydration number and hydrated radius, favoring the ion dehydration. This work provides an insightful route toward the quantitative understanding and prediction of ion dehydration in confined water. 相似文献
6.
H.U. Hambali A.A. Jalil S. Triwahyono S.F. Jamian N.A.A. Fatah A.A. Abdulrasheed T.J. Siang 《International Journal of Hydrogen Energy》2021,46(48):24652-24665
A unique mesostructured fibrous silica@ZSM-5 (HSi@ZSM-5) catalyst was synthesized via microemulsion ZSM-5 zeolite seed assisted synthesis method and successfully applied in enhanced propylene formation in methanol to olefin (MTO) process. Characterization of the catalysts were carried out by FESEM, TEM, XRD, TGA, N2 adsorption-desorption, NH3 and KBr probed FTIR. Catalytic performance of as-synthesized catalyst was examined using a micro-pulse reactor and compared with the commercial HZSM-5. The reaction mechanism was elucidated by in-situ methanol FTIR spectroscopy. It was found that HSi@ZSM-5 produced higher propylene selectivity (56%) and was stable for long time on stream (80 h), nearly three-fold higher than that of commercial HZSM-5. In addition, HSi@ZSM-5 displayed higher rate of methanol dehydration, surface methoxy species generation and olefin methylation, indicating that alkene catalytic cycle is the dominant reaction mechanism. The higher selectivity towards propylene was correlated to the existence of moderate acidity which impeded the formation of paraffins and polymethylbenzene intermediates. These observations are further supported by KBr probed FTIR findings which revealed negligible paraffinic carbon species on HSi@ZSM-5. Thus, the unique fibrous silica@ZSM-5 retarded coke deposition due to suppression of undesired side reactions thereby signifying intensified propylene formation, which is highly desirable in commercial MTO processes. 相似文献
7.
大幅减少炼油生化剩余污泥对降低企业污泥处理和处置费用、保护生态环境意义重大。考察了炼油生化剩余污泥催化深度减量SMR技术工业化的处理效果,运行结果表明:对含水率98.3%的炼油生化剩余污泥,经过SMR污泥减量装置的处理,污泥脱水性能得到显著改善,脱水残渣平均含水率57.1%、污泥量减少99.4%、挥发性悬浮物平均去除率78.3%、消解液BOD5/COD比为0.31,达到了污泥深度减量化的目的。 相似文献
8.
Eduardo J. Cavanagh Mariano J. Savelski C. Stewart Slater 《Chemical Engineering Research and Design》2014
The environmental impact reduction and operating costs savings associated with the purification and recovery of solvent waste in the manufacture of active pharmaceutical ingredients (API's) were investigated. A software toolbox has been developed that combines Aspen Plus® process simulation with SimaPro® and Ecosolvent life cycle assessment (LCA) databases. A LCA approach was used in order to consider the environmental impact beyond pharmaceutical production plant boundaries. The feasibility of a relatively small flexible equipment-skid capable of recovering multiple solvent waste streams was evaluated. Distillation and pervaporation were considered to separate binary waste solvent mixtures. Optimum distillation reflux ratio and feed stage were determined to maximize the environmental impact reductions and operating cost savings. The optimum reflux ratio was significantly higher than 1.2 times the minimum reflux ratio suggested by traditional heuristics. The emissions and cost reductions obtained were as much as 49% and 56% higher, respectively, as compared to using the conventional optimum reflux ratio. A comprehensive cash flow analysis showed that the recovery of low volume solvent waste streams is economically feasible, despite traditional thinking. Three case studies from Pfizer are presented to show how our software tool can aid in green engineering decision making. 相似文献
9.
《Journal of Industrial and Engineering Chemistry》2014,20(2):668-673
The precipitation method was used to modify HZSM-5 by coating it with aluminophosphate at P/Al molar ratios of 0.3, 0.8, 1.2 and 1.5. These catalysts were characterized by XRD, NH3-TPD, BET, FT-IR, ICP-TEOS and SEM and evaluated as catalysts for the methanol dehydration reaction. The ZALPO0.8 catalyst achieved 86% conversion which was the highest conversion till 315 °C. It was found that primary benefits of AlPO modification were that it tended to retard the activity of the highly active acid sites which promote dimethyl ether decomposition and led to decrease in the apparent activation energy. 相似文献
10.