全文获取类型
收费全文 | 720篇 |
免费 | 107篇 |
国内免费 | 33篇 |
专业分类
综合类 | 28篇 |
化学工业 | 582篇 |
机械仪表 | 1篇 |
能源动力 | 5篇 |
轻工业 | 26篇 |
石油天然气 | 43篇 |
武器工业 | 1篇 |
无线电 | 4篇 |
一般工业技术 | 167篇 |
自动化技术 | 3篇 |
出版年
2024年 | 2篇 |
2023年 | 5篇 |
2022年 | 14篇 |
2021年 | 16篇 |
2020年 | 17篇 |
2019年 | 15篇 |
2018年 | 13篇 |
2017年 | 17篇 |
2016年 | 29篇 |
2015年 | 18篇 |
2014年 | 26篇 |
2013年 | 35篇 |
2012年 | 76篇 |
2011年 | 55篇 |
2010年 | 37篇 |
2009年 | 41篇 |
2008年 | 26篇 |
2007年 | 47篇 |
2006年 | 36篇 |
2005年 | 25篇 |
2004年 | 36篇 |
2003年 | 40篇 |
2002年 | 31篇 |
2001年 | 37篇 |
2000年 | 36篇 |
1999年 | 31篇 |
1998年 | 30篇 |
1997年 | 22篇 |
1996年 | 15篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 11篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1988年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有860条查询结果,搜索用时 109 毫秒
61.
62.
63.
《分离科学与技术》2012,47(1):35-41
Abstract A more precise criterion for the formation of a steady-state sorption front is the convergence of the integrals which characterize the quantity of a sorbate in the leading edge of the front and the unused capacity of a sorbent behind the front. Existence of an asymptotic solution of the equation of sorption dynamics is not sufficient for convergence of these integrals, if the line passing through the points of the equilibrium isotherm, which correspond to the initial concentratons in the solution … and in the sorbent, is tangent to the isotherm at one of these points. 相似文献
64.
Toru Ikegami Tomotake Morita Shunichi Nakayama Hideyuki Negishi Dai Kitamoto Keiji Sakaki Yasunori Oumi Tsuneji Sano Kenji Haraya Hiroshi Yanagishita 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2009,84(8):1172-1177
BACKGROUND: Pervaporation employing ethanol‐permselective silicalite membranes as an alternative to distillation is a promising approach for refining low‐concentration bioethanol solutions. However, to make the separation process practicable, it is extremely important to avoid the problems caused by the adsorption of succinate on the membrane during the separation process. In this work, the pervaporation of an ethanol fermentation broth without succinate was investigated, as well as the influence of several fermentation broth nutrient components. RESULTS: Candida krusei IA‐1 produces an extremely low level of succinate. The decrease in permeate ethanol concentration through a silicone rubber‐coated silicalite membrane during the separation of low‐succinate C. krusei IA‐1 fermentation broth was significantly improved when compared with that obtained using Saccharomyces cerevisiae broth. By treating the fermentation broth with activated carbon, bioethanol was concentrated as efficiently as with binary mixtures of ethanol/water. The total flux was improved upto 56% of that obtained from the separation of binary mixtures, compared with 43% before the addition of activated carbon. Nutrients such as peptone, yeast extract and corn steep liquor had a negative effect on pervaporation, but this response was distinct from that caused by succinate. CONCLUSION: For consistent separation of bioethanol from C. krusei IA‐1 fermentation broth by pervaporation, it is useful to treat the low nutrient broth with activated carbon. To further improve pervaporation performance, it will be necessary to suppress the accumulation of glycerol. Copyright © 2009 Society of Chemical Industry 相似文献
65.
Research on the effect of various chemical groups on the pervaporation performance of membranes was very important for understanding the separation phenomenon. In this article, a polystyrene membrane with ? CF3 groups on its surface was prepared by casting normal polystyrene (PS‐H) solution with small‐molecular‐weight α,ω‐fluoroalkyl‐terminated polystyrene (S‐PS‐(CF3)2) on a glass plate. The amount of ? CF3 groups on the surface was adjusted by changing S‐PS‐(CF3)2 content, which was documented by X‐ray photoelectron spectroscopy analysis, surface energy, and contact angle measurements. The effect of S‐PS‐(CF3)2 content on separation performance of S‐PS‐(CF3)2/PS‐H blend membranes for ethanol/water mixture was investigated. The results showed that water concentration in the permeate decreased with increasing S‐PS‐(CF3)2 content; however, the permeation rate did not change until the S‐PS‐(CF3)2 content was increased to 1 wt %. The reason for this was attributed to the fact that a small amount of S‐PS‐(CF3)2 enables a simple surface modification of the membrane keeping its inner structure relatively unchanged. This was confirmed by swelling degree measurements and other experiments. Comparison with our previous work showed that the ? CF3 groups on the surface lowers the water permselectivity of the polystyrene membranes, whereas the ? COOH groups enhance the water permselectivity. However, neither hydrophobic ? CF3 nor hydrophilic groups on the membrane surface appeared to have any influence on flux. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
66.
67.
采用紫外光接枝填充聚合技术,以非对称聚丙烯腈(PAN)超滤膜为底膜,聚乙二醇甲醚甲基丙烯酸酯(MePEO300MA)为大分子单体,制备了芳烃优先透过的渗透汽化复合膜。考察了单体浓度和紫外光照射反应时间对复合膜甲苯/正庚烷渗透汽化分离性能的影响,并对复合膜降低石脑油芳烃含量,优化乙烯裂解原料进行了初步探索。研究结果表明,复合膜对甲苯质量分数为20%的甲苯/正庚烷混合物(80℃)的分离系数达到5.6,渗透通量为2.47 kg/(m2.h);当切割比为20%时,石脑油的芳烃质量分数由7.52%降至4.11%,降低了45%,初步说明渗透汽化复合膜在降低石脑油的芳烃含量,优化乙烯裂解原料方面的应用前景。 相似文献
68.
《分离科学与技术》2012,47(17):2531-2539
ZIF-8-filled polydimethylsiloxane (PDMS) membranes, PDMS/ZIF-8, were prepared by a two-step polymerization process and were used to recover n-butanol from an aqueous solution by pervaporation (PV). Compared with pure PDMS membrane, PDMS/ZIF-8 membranes demonstrated an obviously higher n-butanol permselectivity. As an increase of ZIF-8 content, n-butanol/water selectivity increased initially and then decreased, while the n-butanol and water permeability decreased monotonously. PDMS/ZIF-8 membrane containing 2 wt% ZIF-8, that is, PDMS/ZIF-8-2 showed the highest selectivity. On the other hand, selectivity and permeability for n-butanol and water of PDMS/ZIF-8-2 membrane decreased with the increase of operating temperature. The selectivity and permeability for n-butanol reached 7.1 and 3.28 × 105 barrer, respectively, at 30°C when the feed concentration of n-butanol was 0.96 wt%. 相似文献
69.
《分离科学与技术》2012,47(10):1354-1362
Pervaporative separation of acetone from water at a concentration range of 0–100 wt% were studied using sodium alginate (NaAlg)/Poly vinyl pyrrolidone (PVP) membranes. Membranes were prepared in different ratios (w/w) (100/0, 95/5, 90/10, 85/15, 80/20, 75/25) of NaAlg/PVP by crosslinking with CaCl2. Experimental studies were carried out to investigate the effects of the operating temperature, feed composition, and membrane thickness on the pervaporation performance. The optimum operating temperature, membrane thickness, NaAlg/PVP ratio, and feed composition were determined as 40°C, 70 µm, 75/25 (w/w), and 20 wt% acetone, respectively. The effect of PVP content in the membranes was investigated on pervaporation performance. The permeation rate was increased with increasing the PVP content; however, there was no appreciable change about the separation factor. The permeation rate and separation factor values were found to be in the range of 0.304–1.023 kg/m2 h and 16–57, respectively. In addition, the sorption-diffusion properties of the alginate membranes were investigated at the operating temperature and the feed composition. It was found that the sorption selectivity was the dominant factor for the separation of acetone/water mixtures. 相似文献
70.
Paper membranes made from vulcanized cellulose were used for the pervaporation (PV) of aqueous solutions containing methanol, ethanol, and isopropanol. It was noted that the vulcanized cellulose paper membranes (VCPM) could effectively separate alcohol and water from the mixture solutions. To observe the effect of the separation of alcohol aqueous mixtures, the permeation behavior of water and alcohol was examined by means of the separation factor and the permeation flux. The values of the permeation flux in the ethanol/water mixtures were found to vary from 6.2 kg/m2h to 2.1 kg/m2h, as the concentration of ethanol increased from 8 to 87 wt %, and the separation factor (α) changed from α = 2.6 to 6.6, respectively. This showed that the VCPM enhanced the separation of water and alcohol. The highest value observed for the permeation flux was 11 kg/m2h at 87 wt % of methanol concentration and the separation factor at this condition was 4.1. It was shown also that an efficient separation was obtained in the isopropanol/water mixture with a separation factor of 16.6. The contact angles of alcohol/water droplets on the VCPM were measured as well as the wettability of the membrane. There was a tendency of decrease for the contact angle, as the alcohol concentration decreased. This suggested that the solvent wettability decreased in high alcohol concentrations. It was concluded that a high permeabilitty of water through the VCPM resulted in the separation of alcohols and water in the PV process. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献