全文获取类型
收费全文 | 885篇 |
免费 | 60篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 3篇 |
综合类 | 2篇 |
化学工业 | 325篇 |
金属工艺 | 8篇 |
机械仪表 | 41篇 |
建筑科学 | 46篇 |
矿业工程 | 1篇 |
能源动力 | 16篇 |
轻工业 | 185篇 |
水利工程 | 9篇 |
石油天然气 | 8篇 |
无线电 | 22篇 |
一般工业技术 | 136篇 |
冶金工业 | 83篇 |
原子能技术 | 4篇 |
自动化技术 | 57篇 |
出版年
2024年 | 3篇 |
2023年 | 6篇 |
2022年 | 29篇 |
2021年 | 34篇 |
2020年 | 30篇 |
2019年 | 36篇 |
2018年 | 34篇 |
2017年 | 33篇 |
2016年 | 37篇 |
2015年 | 19篇 |
2014年 | 39篇 |
2013年 | 56篇 |
2012年 | 72篇 |
2011年 | 67篇 |
2010年 | 59篇 |
2009年 | 41篇 |
2008年 | 55篇 |
2007年 | 39篇 |
2006年 | 33篇 |
2005年 | 31篇 |
2004年 | 25篇 |
2003年 | 21篇 |
2002年 | 19篇 |
2001年 | 11篇 |
2000年 | 8篇 |
1999年 | 6篇 |
1998年 | 11篇 |
1997年 | 13篇 |
1996年 | 10篇 |
1995年 | 12篇 |
1994年 | 8篇 |
1993年 | 10篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1989年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1969年 | 1篇 |
1968年 | 2篇 |
排序方式: 共有946条查询结果,搜索用时 11 毫秒
31.
Roseli de Souza Santos da Costa Flavia da Silva Santos Daniela de Barros Mucci Tânia Vignuda de Souza Fátima Lucia de Carvalho Sardinha Célia Regina Moutinho de Miranda Chaves Maria das Graças Tavares do Carmo 《Lipids》2016,51(12):1363-1373
The purpose of this study was to investigate the trans fatty acids (TFA) content and distribution in colostrum, mature milk, and diet of adolescent mothers, after TFA declaration in food labels became mandatory in Brazil. Participants were healthy adolescents (n 54, 15–19 years, 1–90 days postpartum) practicing exclusive breastfeeding. Milk samples were collected 3 days after delivery (colostrum) and in the third month postpartum (mature milk) by hand expression. The fatty acid composition of the milk samples was determined by gas chromatography. TFA intake corresponded to 1.23 % of total energy value. Total 18:2 TFA accounted for less than 0.5 % of the energy intake. The amount of total 18:1 TFA (mean ± SEM) was 1.9 % ± 0.14 in colostrum and 1.5 % ± 0.2 in mature milk. The total content of n‐3 PUFA was inversely correlated with the total content of 18:1 TFA in colostrum. Both in colostrum and in mature milk, vaccenic acid (11t‐18:1) was found to be the most abundant 18:1 trans isomer, followed by elaidic acid (9t‐18:1), whereas rumenic acid (9c,11t‐18:2 CLA) was the predominant 18:2 trans isomer. In conclusion, the levels of TFA of industrial sources found in the mother's diet and breast milk (colostrum and mature milk) showed a decrease in relation to those observed in studies conducted prior to the TFA labeling resolution in Brazil. However, the current low intake levels of n‐3 LCPUFA and DHA content in the milk of lactating adolescents may be insufficient for supporting adequate neurological development of the infants. 相似文献
32.
33.
A method for solvent screening and searching for additives in the field of physical absorption processes is presented. A model based on the concept of virtual components and on the concept of a simplified abstract flow sheet is created. An estimation procedure for thermodynamically consistent property sets for the virtual component is developed. The model is implemented into MATLAB®. Its application is demonstrated in two studies including a study for a solvent additive. Potential candidates can be characterized and ranges for properties of the solvent or additive are found by means of the model. Conclusions obtained from the model support the screening process by a reduction of the number of further investigated components. 相似文献
34.
Silvia G. Schrank Wilhelm Gebhardt Humberto J. José Regina F. P. M. Moreira 《臭氧:科学与工程》2017,39(3):159-187
Ozone is an unstable and highly reactive gas applied in drinking water or wastewater treatment to oxidize and/or mineralize pollutants. Its application in wastewater treatment leads to a destruction of persistent pollutants combined with an improvement of biodegradability. The oxidation of organic and inorganic compounds in tannery wastewater at different pHs applying O3 was studied. Results after O3-treatment were determined by conventional wastewater parameters, e.g., total organic carbon (TOC), biochemical oxygen demand after 5 days (BOD5), and chemical oxygen demand (COD), as well as by substance-specific mass spectrometric analytical techniques, i.e., gas chromatography—mass spectrometry (GC/MS) and liquid chromatography—mass and tandem mass spectrometry (LC/MS and—MSn). In parallel, variations in the toxicity of the tannery wastewater against water organisms before and after O3-treatment were determined by means of biotoxicity testing, i.e., Daphnia magna Straus and Vibrio fischeri bioassays. 相似文献
35.
Ruigrok VJ van Duijn E Barendregt A Dyer K Tainer JA Stoltenburg R Strehlitz B Levisson M Smidt H van der Oost J 《Chembiochem : a European journal of chemical biology》2012,13(6):829-836
Aptamers are oligonucleotide ligands that are selected for high-affinity binding to molecular targets. Only limited knowledge relating to relations between structural and kinetic properties that define aptamer-target interactions is available. To this end, streptavidin-binding aptamers were isolated and characterised by distinct analytical techniques. Binding kinetics of five broadly similar aptamers were determined by surface plasmon resonance (SPR); affinities ranged from 35-375 nM with large differences in association and dissociation rates. Native mass spectrometry showed that streptavidin can accommodate up to two aptamer units. In a 3D model of one aptamer, conserved regions are exposed, strongly suggesting that they directly interact with the biotin-binding pockets of streptavidin. Mutational studies confirmed both conserved regions to be crucial for binding. An important result is the observation that the most abundant aptamer in our selections is not the tightest binder, emphasising the importance of having insight into the kinetics of complex formation. To find the tightest binder it might be better to perform fewer selection rounds and to focus on post-selection characterisation, through the use of complementary approaches as described in this study. 相似文献
36.
Anna Wonaschuetz Theresa Haller Eva Sommer Lorenz Witek Hinrich Grothe Regina Hitzenberger 《Aerosol science and technology》2019,53(1):21-28
Steam collection devices collecting aerosol particles into liquid samples are frequently used to analyze water-soluble particulate material. The fate of water-insoluble components is often neglected. In this work, we show that fresh soot particles can be suspended into pure water using a steam collection device, the particle-into-liquid sampler (PILS, Weber et?al. 2001). The overall collection efficiency of freshly generated soot particles was found to be on the order of 20%. This shows that, depending on the analytic technique employed, the presence of insoluble, and/or hydrophobic particles in liquid samples from steam collection cannot be neglected.
Copyright © 2018 The Author(s). Published with license by Taylor & Francis Group, LLC 相似文献
37.
Selected conducting polymers (polyaniline and poly-N-methylaniline), and copolymers of aniline with o-, m-, and p-phenylenediamines, as well as with metanilic acid, have been electropolymerized at a gold electrode, and studied with Raman spectroscopy (532 nm excitation) in a pH-neutral solution. Characteristic Raman features have been obtained and analysed for (co)polymers within electrode potential range of ?0.4 to 0.2 V vs. Ag/AgCl. Changes in Raman spectra depending on electrode potential have been analysed and assigned to different redox forms of (co)polymers. It has been shown that both oxidised and reduced forms of (co)polymers can exist, depending on electrode potential, even in a pH-neutral solution, where most of the polymers studied show no clearly defined electrochemical redox processes. 相似文献
38.
Chunyang Wang Marci Sherrard Sudhakar Pagadala Regina Wixon Roy A. Scott 《Journal of the American Oil Chemists' Society》2000,77(5):483-487
This study reports the isoflavone contents of 210 soybean cultivars grown in South Dakota and explores possible relations
between isoflavone contents and agronomic characteristics. Total isoflavone contents (normalized) ranged from 1161 to 2743
μg/g. A number of agronomic characteristics were documented for each variety including maturity group, hilum color, disease
resistance, seed weight, yield, maturity (in days), and plant height. Varieties in maturity group I had significantly higher
total isoflavones when compared to maturity group 0. Hilum color was related to differences in genistin, daidzein, and genistein
content. No differences in isoflavone content were observed based on disease resistance profiles. Genistein content was found
to be negatively correlated with yield, days of maturity, and plant height. Weak but significant correlations also existed
between these agronomic characteristics and other isoflavones. 相似文献
39.
Michele Espinosa da Cunha Laiza Canielas Krause Maria Silvana Aranda Moraes Candice Schmitt Faccini Rosângela Assis Jacques Suelen Rodrigues Almeida Maria Regina Alves Rodrigues Elina Bastos Caramão 《Fuel Processing Technology》2009
In the present work, the process of biodiesel production in a pilot plant has been studied using beef tallow as raw materials with methanol and potassium hydroxide as catalyst. The biodiesel quality is regulated by Brazilian specifications (Resolution 42) by the National Agency of Petroleum (ANP). The alkaline transesterification of animal fat with methanol produces a biodiesel with high quality and also with a good conversion rate. The process is possible but the economical viability must be improved by recovering methanol and glycerin. The obtained results have been used for industrial scale up of the process. 相似文献
40.
Débora Ravelli Carla Romero Matsuoka Regina Célia Della Modesta Thais Maria Ferreira de Souza Vieira Marisa Aparecida Bismara Regitano-d’Arce 《Journal of the American Oil Chemists' Society》2010,87(5):515-520
Measurements of degradation in frying oils are mainly based on physico-chemical properties. Total polar compounds (TPC) and
free fatty acids (FFA) content in frying oils are used as a guide for discarding used oils. The purpose of this study was
to evaluate the efficacy of a sensory method in detecting degradation in soybean oils used in potato chips deep frying. The
sensory evaluation of oil samples was determined by a trained panel; after rigorous selection and training steps. Free fatty
acid, TPC and Rancimat induction period (IP) were quantified in the same samples. The proposed sensory method was sensitive
to small differences in rancidity. The selected and trained sensory panel discarded oil samples with 0.175% FFA as oleic acid,
18.92% TPC, and 0.20 h IP. According to the results achieved in this research sensorial trained panel response is sensitive
and accurate in refusing deteriorated frying oils. Besides this, soybean oil can be used for deep frying procedures and safely
discarded according to the panel response, although presenting up to 7% linolenic acid. 相似文献