全文获取类型
收费全文 | 315篇 |
免费 | 82篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 1篇 |
综合类 | 17篇 |
化学工业 | 184篇 |
机械仪表 | 3篇 |
建筑科学 | 10篇 |
矿业工程 | 2篇 |
能源动力 | 57篇 |
轻工业 | 113篇 |
水利工程 | 5篇 |
石油天然气 | 11篇 |
无线电 | 1篇 |
一般工业技术 | 5篇 |
自动化技术 | 1篇 |
出版年
2024年 | 4篇 |
2023年 | 15篇 |
2022年 | 14篇 |
2021年 | 20篇 |
2020年 | 31篇 |
2019年 | 44篇 |
2018年 | 32篇 |
2017年 | 21篇 |
2016年 | 24篇 |
2015年 | 23篇 |
2014年 | 23篇 |
2013年 | 29篇 |
2012年 | 23篇 |
2011年 | 25篇 |
2010年 | 17篇 |
2009年 | 11篇 |
2008年 | 4篇 |
2007年 | 7篇 |
2006年 | 7篇 |
2005年 | 2篇 |
2004年 | 5篇 |
2003年 | 7篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1985年 | 1篇 |
排序方式: 共有410条查询结果,搜索用时 579 毫秒
1.
1 INTRODUCTION Porphyridium cruentum is a kind of unicellular microalgae, which can live widely in freshwater, marine, brackish, and soil environment[1]. Great attention has been paid to its potential economic value such as the high content of essential high unsaturated fatty acids, especially arachidonic acid (AA) and eicosapentaenoic acid (EPA) (ca 50% in the total fatty acids), ploysaccharides, and synthetic pigments, especially phycoerythrin (PE)[2,3]. During cultivation, the cells… 相似文献
2.
A. Robles Medina A. Giménez Giménez F. García Camacho J. A. Sánchez Pérez E. Molina Grima A. Contreras Gómez 《Journal of the American Oil Chemists' Society》1995,72(5):575-583
n-3 Polyunsaturated fatty acids (n-3 PUFA) from the marine microalgaIsochrysis galbana were concentrated and purified by a two-step process—formation of urea inclusion compounds followed by preparative high-performance
liquid chromatography. These methods had been developed previously with fatty acids from cod liver oil. By the urea inclusion
compounds method, a mixture that contained 94% (w/w) stearidonic (SA), eicosapentaenoic (EPA), plus docosahexaenoic (DHA)
acids (4:1 urea/fatty acid ratio and 4°C crystallization final temperature) was obtained from cod liver oil fatty acids. Further
purification of SA, EPA, and DHA was achieved with reverse-phase C18 columns. These isolations were scaled up to a semi-preparative column. A PUFA concentrate was isolated fromI. galbana with methanol/water (80:20, w/w) or ethanol/water (70:30, w/w). With methanol/water, a 96% EPA fraction with 100% yield was
obtained, as well as a 94% pure DHA fraction with a 94% yield. With ethanol/water as the mobile phase, EPA and DHA fractions
obtained were 92% pure with yields of 84 and 88%, respectively. 相似文献
3.
M. Cartens E. Molina Grima A. Robles Medina A. Giménez Giménez J. Ibáñez González 《Journal of the American Oil Chemists' Society》1996,73(8):1025-1031
Eicosapentaenoic acid (EPA, 20∶5n-3) was obtained from the marine microalgaePhaeodactylum tricornutum by a three-step process: fatty acid extraction by direct saponification of biomass, polyunsaturated fatty acid (PUFA) concentration
by formation of urea inclusion compounds, and EPA isolation by semipreparative high-performance liquid chromatography (HPLC).
Alternatively, EPA was obtained by a similar two-step process without the PUFA concentration step by the urea method. Direct
saponification of biomass was carried out with two solvents that contained KOH for lipid saponification. An increase in yield
was obtained because the problems associated with emulsion formation were avoided by separating the biomass from the soap
solution before adding hexane for extraction of insaponifiables. The most efficient solvent, ethanol (96%) at 60°C for 1 h,
extracted 98.3% of EPA. PUFA were concentrated by the urea method with a urea/fatty acid ratio of 4∶1 at a crystallization
temperature of 28°C and by using methanol and ethanol as urea solvents. An EPA concentration ratio of 1.73 (55.2∶31.9) and
a recover yield of 78.6% were obtained with methanol as the urea solvent. This PUFA concentrate was used to obtain 93.4% pure
EPA by semipreparative HPLC with a reverse-phase, C18, 10 mm i.d.×25-cm column and methanol/water (1% acetic acid), 80∶20 w/w, as the mobile phase. Eighty-five percent of EPA
loaded was recovered, and 65.7% of EPA present inP. tricornutum biomass was recovered in highly pure form by this three-step downstream process. Alternatively, 93.6% pure EPA was isolated
from the fatty acid extract (without the PUFA concentration step) with 100% EPA recovery yield. This two-step process increases
the overall EPA yield to 98.3%, but it is only possible to obtain 20% as much EPA as that obtained by three-step downstream
processing. 相似文献
4.
利用诱变育种技术对用来固定CO2的微藻进行育种,获得耐受高CO2浓度、可高效固定CO2的斜生栅藻突变株WUST—04,其最适宜生长的CO2浓度由诱变前的5%提高到诱变后的15%。在5L的光生物反应器中初步研究了该微藻的固碳工艺。结果表明,在适宜的CO2浓度下,微藻的CO2固定效率提高了17.5%,最大CO2固定效率达1.846g/d·L。 相似文献
5.
基于微藻培养的沼液处理相关耦合技术是近些年沼液资源化处理利用领域的研究热点。本文综述了沼液处理与CO2固定耦合技术、沼液处理与高值生物质生产耦合技术、沼液处理与生态农业耦合技术等耦合技术的研究发展现状与优缺点,并指出了各耦合技术发展的关键问题,如沼液处理与CO2固定耦合技术中高CO2耐受性藻株选育与固碳影响机理研究问题、沼液处理与高值生物质生产耦合技术中低成本、低能耗高值生物质生产技术开发问题、沼液处理与生态农业耦合技术系统性评价体系缺乏问题等。最后,为促进耦合技术突破现有瓶颈,从微藻选育、微藻培养、沼液处理与沼气工程综合经济性4个角度提出相关的建议。 相似文献
6.
介绍了有效核转化微藻的方法和策略,以及微藻中密码子使用存在偏爱性,指出微藻作为绿色细胞已用来生产具有特殊价值的代谢物和外源蛋白质,转基因微藻在生物工程上已得到应用。 相似文献
7.
Giuseppe Olivieri Piero Salatino Antonio Marzocchella 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2014,89(2):178-195
Over the past ten years a great deal of literature has focused on the biotechnological potential of microalgal commercial applications, mainly in the field of biofuel production. However, the biofuel production is not yet competitive, mainly due to the incidence of the photobioreactor technology on the process cost. Besides, major advances in classic photobioreactor design, several novel configurations have been proposed in the last 20 years to improve their performance expressed in terms of light absorption, biomass productivity, light to biomass yield and photosynthetic efficiency. This review aims at analyzing and classifying the most recent advances and the several novel approaches to the design, development, control and modeling of photobioreactors. The diverse approaches are grouped considering irradiance strategies, multiphase hydrodynamics, mass transfer mechanisms, modeling approaches and control strategies. Some innovative applications of the photobioreactor technology are also reported. © 2013 Society of Chemical Industry 相似文献
8.
9.
Mariam Alhattab 《分离科学与技术》2017,52(12):2002-2016
Microalgae biomass has great potential for being used as feedstock for the sustainable production of biodiesel, as it is able to produce 7–31 times more oil than the top terrestrial crop. It is a green alternative to the currently utilized energy sources as it can reduce CO, CO2 and hydrocarbon emissions. However, downstream processing costs for the dilute biomass are a major challenge. Foam flotation has been recently investigated for the recovery of microalgae cells from dilute liquid suspensions. A number of variables on the effectiveness of foam flotation for microalgae have been investigated, which include surfactant type and concentration, cell concentration, pH, hydrophobicity, time, growth stage, flow rate, ionic strength, alkalinity, temperature, bubble size, and column size. It appears to be a promising method for the recovery of algae for biofuel production, as a result of the high removal recoveries, good enrichment ratios, ability to process large volumes of biomass, and its ease of operation. However, literature on this subject is scarce, and there are research gaps that should be investigated including characterization of microalgae cells and impact on foam separation and the effect of surfactant as a treatment prior to lipid extraction. 相似文献
10.