全文获取类型
收费全文 | 5759篇 |
免费 | 572篇 |
国内免费 | 216篇 |
专业分类
电工技术 | 28篇 |
综合类 | 370篇 |
化学工业 | 3159篇 |
金属工艺 | 73篇 |
机械仪表 | 57篇 |
建筑科学 | 35篇 |
矿业工程 | 62篇 |
能源动力 | 179篇 |
轻工业 | 658篇 |
水利工程 | 3篇 |
石油天然气 | 1142篇 |
武器工业 | 2篇 |
无线电 | 29篇 |
一般工业技术 | 167篇 |
冶金工业 | 172篇 |
原子能技术 | 57篇 |
自动化技术 | 354篇 |
出版年
2024年 | 14篇 |
2023年 | 63篇 |
2022年 | 156篇 |
2021年 | 149篇 |
2020年 | 138篇 |
2019年 | 125篇 |
2018年 | 118篇 |
2017年 | 119篇 |
2016年 | 147篇 |
2015年 | 196篇 |
2014年 | 373篇 |
2013年 | 376篇 |
2012年 | 470篇 |
2011年 | 442篇 |
2010年 | 326篇 |
2009年 | 271篇 |
2008年 | 240篇 |
2007年 | 325篇 |
2006年 | 320篇 |
2005年 | 299篇 |
2004年 | 309篇 |
2003年 | 275篇 |
2002年 | 223篇 |
2001年 | 193篇 |
2000年 | 177篇 |
1999年 | 135篇 |
1998年 | 116篇 |
1997年 | 82篇 |
1996年 | 70篇 |
1995年 | 73篇 |
1994年 | 48篇 |
1993年 | 38篇 |
1992年 | 32篇 |
1991年 | 29篇 |
1990年 | 18篇 |
1989年 | 18篇 |
1988年 | 10篇 |
1987年 | 9篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1982年 | 6篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1951年 | 5篇 |
排序方式: 共有6547条查询结果,搜索用时 15 毫秒
11.
甲基丙烯酸乙酯合成工艺研究 总被引:1,自引:1,他引:0
以大孔强酸性离子交换树脂为催化剂,甲基丙烯酸(MAA)与乙醇直接酯化合成甲基丙烯酸乙酯(EMA)。在MAA与乙醇摩尔比为1:3、反应温度89~93℃、空速0.3h~(-1)的条件下,MAA转化率不低于98%,EMA的选择性不低于99%。 相似文献
12.
13.
14.
SIMULATION STUDIES OF THE REMOVAL OF WATER FROM ETHANOL BY A CATALYTIC DISTILLATION PROCESS 总被引:1,自引:0,他引:1
Christina B. Dirk-Faitakis Karl T. Chuang 《Chemical Engineering Communications》2005,192(11):1541-1557
A new approach based on catalytic distillation (CD) technology was proposed to remove water from ethanol. Isobutylene was introduced to react with water in the CD column. The commercial software simulation tool Aspen Plus was used to investigate the effects of key design factors such as operating pressure and temperature, reactant ratios, reflux and distillate to feed ratios, number of separation and reaction stages, and feed and reaction zone location. It was found that the CD technology offers potential advantages of reduced energy consumption and reduced capital cost over traditional approaches for the removal of water from ethanol. 相似文献
15.
Miriam A Martinello Mauro Villegas Maria del C Pramparo 《Journal of the science of food and agriculture》2007,87(8):1559-1563
A process of physical refining wheat germ oil using the technique of molecular distillation (MD) is presented in this work. Wheat germ oil was obtained from the germ by solvent extraction using hexane and also by cold pressing. The oil extracted with hexane was degummed and bleached before deacidification in order to modify the parameters of phosphorus and color. The goal in carrying out the stage of physical refining by MD was to preserve the maximum amount of original antioxidative potential obtained from extraction of the crude oil. The effect of evaporation temperature of one‐stage MD on the efficiency of free fatty acid elimination was studied. The antioxidant portion was followed by means of analytic determination of tocopherols by high‐performance liquid chromatography. Tocopherol retention up to 98% was achieved in the oil extracted by pressing, and yields of up to 96% were achieved in the oil extracted with hexane. Copyright © 2007 Society of Chemical Industry 相似文献
16.
This study demonstrates that state observers can be developed and applied to infer the composition profiles of reactive distillation columns from noise-contaminated temperature measurements. The design and implementation of a Kalman filter (KF) and a Luenberger observer (LO) are carried out, and their performances are quantitatively assessed. The reliability, accuracy, and robustness of the two designs method are examined and compared quantitatively. The design and implementation of a Luenberger observer are simpler and easier to carry out than those of a Kalman filter. On the other hand, a Kalman filter is found to be more robust to a noisy measurements, erroneous initial estimates, and model uncertainties. A Luenberger observer could be used for composition estimation of reactive distillation when an ideal model of the system can reasonably approximate the real system; otherwise, a Kalman filter is recommended to be applied in more practical situations. 相似文献
17.
18.
梁昔明 《中南工业大学学报(英文版)》2005,12(1):93-96
An active set truncated-Newton algorithm (ASTNA) is proposed to solve the large-scale bound constrained sub-problems. The global convergence of the algorithm is obtained and two groups of numerical experiments are made for the various large-scale problems of varying size. The comparison results between ASTNA and the subspace limited memory quasi-Newton algorithm and between the modified augmented Lagrange multiplier methods combined with ASTNA and the modified barrier function method show the stability and effectiveness of ASTNA for simultaneous optimization of distillation column. 相似文献
19.
介绍抚顺石油化工公司石油一厂东蒸馏装置的改造情况,通过技术改造,使减压蒸馏塔由生产燃料型改造成生产石蜡-润滑油型,满足了该厂对石蜡和润滑油料的质量要求。 相似文献
20.
哈尔滨炼油厂MTBE装置试生产 总被引:4,自引:0,他引:4
介绍了哈尔滨炼油厂MTBE装置的工艺路线、新技术的应用及特点;催化剂的装填及应用情况;总结了生产过程中遇到的一系列问题及解决办法;探索了平稳生产的新徐径,以保证装置安全、平稳、长周期运行;同时对反应器操作温度、催化蒸馏塔操作压力、原料中醇烯比等因素对异丁烯转化率及MTBE产品的影响做了简单的总结。 相似文献