全文获取类型
收费全文 | 560篇 |
免费 | 34篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 199篇 |
金属工艺 | 11篇 |
机械仪表 | 12篇 |
建筑科学 | 31篇 |
能源动力 | 13篇 |
轻工业 | 99篇 |
水利工程 | 7篇 |
石油天然气 | 2篇 |
无线电 | 29篇 |
一般工业技术 | 92篇 |
冶金工业 | 35篇 |
原子能技术 | 2篇 |
自动化技术 | 61篇 |
出版年
2024年 | 3篇 |
2023年 | 5篇 |
2022年 | 38篇 |
2021年 | 57篇 |
2020年 | 21篇 |
2019年 | 23篇 |
2018年 | 23篇 |
2017年 | 27篇 |
2016年 | 25篇 |
2015年 | 10篇 |
2014年 | 28篇 |
2013年 | 46篇 |
2012年 | 38篇 |
2011年 | 43篇 |
2010年 | 29篇 |
2009年 | 26篇 |
2008年 | 21篇 |
2007年 | 22篇 |
2006年 | 12篇 |
2005年 | 7篇 |
2004年 | 19篇 |
2003年 | 7篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1998年 | 10篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有594条查询结果,搜索用时 15 毫秒
581.
In vitro cultivated Atlantic salmon (Salmo salar L.), hepatocytes were incubated without or with a mixture of sesamin and episesamin in order to test for possible effects
on lipid metabolism. Sesamin/episesamin exposure (0.05 mM, final concentration) led to increased elongation and desaturation
of 14C 18:3n-3 to docosahexaenoic acid (14C 22:6n-3, DHA, P < 0.01) and down regulated gene expression of Δ6 and Δ5 desaturases compared to control treatment. Sesamin/episesamin further
increased the hepatocytes capacity for fatty acid β-oxidation of 14C 18:3n-3 (P < 0.01) to the 14C acid soluble products, acetate, malate and oxaloacetate, in agreement with an increased gene expression of carnitine palmitoyltransferase
I. Also the gene expression of cluster of differentiation 36 was upregulated and the expression of scavenger receptor type
B, peroxisome proliferator-activated receptors α and γ were downregulated. The amount of triacylglycerols secreted by the
cells tended to be lower in the sesamin/episesamin incubated hepatocytes than the control cells. This study shows that sesamin
has favourable effects on lipid metabolism leading to increased level of DHA, which may be of interest for aquaculture use. 相似文献
582.
The recent boom in oil prices has attracted many investors to oil companies in search of both returns and diversification benefits. This analysis of the risk factors of investing in the oil and gas industry in 34 countries finds evidence that oil price is a globally priced factor for the oil industry. The oil and gas sector in developed countries responds more strongly to oil price changes than in emerging markets. Oil and gas industry returns also respond asymmetrically to changes in oil prices; oil price rises have a greater impact than oil price drops. There is no parallel to the asymmetry of oil price changes in other industries related to commodities. If there is any asymmetry, it is in the opposite direction from oil. Negative commodity price changes have a greater impact than positive ones. The results seem to indicate that the oil and gas industry is distinguished by a pass-through effect. 相似文献
583.
Membrane modification by concentration polarization (CP)-enhanced radical graft polymerization using a dilute aqueous solution of appropriate monomer was examined as a method for increasing rejection of boric acid by reverse osmosis (RO) membranes. On the basis of suggested physicochemical rationales a number of monomers were examined in order to determine those with the lowest affinity toward boric acid as compared to water. The improvement in the modified membrane performance was mainly attributed to sealing less selective areas ("defects") inherently present in the original low pressure RO (LPRO) membranes. However, the effect clearly differed for different monomers. Among the examined monomers glycidyl methacrylate (GMA) exhibited the lowest affinity and the largest improvement in removal of boric acid along with a moderate loss of permeability and slightly improved NaCl rejection. Modification of LPRO membrane thus resulted in a membrane with a permeability in the brackish water RO (BWRO) range but with removal of boric acid and salt superior to those reported for most commercial BWRO membranes. 相似文献
584.
585.
In this study, new test systems and express method were developed for the rapid detection of synthetic food dyes in drinks including alcoholic drinks, fruit juices, soft drinks and other non-alcoholic drinks. The detection is based on selective adsorption of synthetic food dyes from a drink by the specific adsorbent contained in the developed test system. The method allows screening of samples for synthetic food dyes in the presence of natural colors by differential spectrophotometry following adsorption. The said adsorbent provides adsorption of synthetic food dyes and substantially does not interact with natural dyes of drinks. Therefore, when a drink contains synthetic dyes, the color of the sample changes, whereas the color of a drink having only natural dyes stays substantially the same. This test can be used as a first step analysis for screening. So, only in a case when the test showed the presence of synthetic dyes in a drink, further laborious identification and quantitative determination of the revealed dyes could be performed. The use of such an approach reduces the time and costs required to perform the analysis. 相似文献
586.
Zhiyuan Hu G. Dan Pantoş Navaratnarajah Kuganathan Rory L. Arrowsmith Robert M. J. Jacobs Gabriele Kociok‐Köhn Justin O'Byrne Kerstin Jurkschat Pierre Burgos Rex M. Tyrrell Stan W. Botchway Jeremy K. M. Sanders Sofia I. Pascu 《Advanced functional materials》2012,22(3):503-518
A new synthetic route to functionalized single walled carbon nanotubes (SWNTs) via supramolecular interactions using a specifically designed naphthalenediimide (NDI) nanoreceptor is demonstrated. The tendency of the NDI to spontaneously form composites with carbon nanomaterials leads to fluorescent amino acid tagged SWNTs, which are dispersible in widely accessible organic solvents (CHCl3, DMSO) as well as in biocompatible cell medium (EMEM, Eagle's modified essential medium). The X‐ray crystal structure of the first iodine‐tagged and amino acid‐functionalized NDI molecule, designed especially to facilitate the high resolution transmission electron microscopy (HR TEM) imaging whilst retaining its ability to self‐assemble into a nanodimensional receptor in weakly polar solvents, is also described. A new hybrid material, NDI@SWNT, was prepared and characterized as dispersed in organic solvents and aqueous media and in the solid state by HR TEM, tapping mode atomic force microscopy (TM AFM), scanning electron microscopy (SEM), circular dichroism, Raman and fluorescence spectroscopies (steady‐state single and two‐photon techniques). Combined microscopy techniques, density functional theory (DFT) calculations using the Spanish Initiative for Electronic Simulations with Thousands of Atoms (SIESTA) program and spectroscopic measurements in solution indicate that amino acid‐functionalized NDI interacts strongly with SWNTs and forms a donor‐acceptor complex. Density functional theory (DFT) calculations predicted the geometry and the binding energies of an NDI molecule loaded onto a SWNT strand and the possibility of charge transfer interactions within the hybrid. The NDI@SWNT composite translocates into cells (e.g. FEK‐4, HeLa, MCF‐7) as an intact object and localizes in the cells' cytoplasm and partially in the nucleus. The NDI coating enhances the biocompatibility of SWNTs and mediates its intracellular localization as shown by confocal fluorescence imaging and fluorescence lifetime imaging (FLIM) techniques. The excited state fluorescence lifetime of the probes in cells versus solution phase indicates that the probes remain unaffected by the change in their chemical environment within the experimental timescale (2 h). 相似文献
587.
Comparative analysis of the fatty acid and sterol profiles of widely consumed Mediterranean crustacean species 总被引:1,自引:0,他引:1
Comparative analysis of FA, NL and sterol profiles in the Nephropsnorvegicus (langoustine), Palinurusvulgaris (lobster) and Penaeuskerathurus (shrimp) muscle and cephalothorax showed that C16:0, C16:1ω-7, C18:0, C18:1ω-9, C20:4ω-6, EPA and DHA were found to be their major FA. Highest EPA occurred in langoustine muscle TL, DHA in both shrimp tissues TL while C20:4ω-6 in lobster muscle and cephalothorax TL. Muscle and cephalothorax NL consisted mainly of sterols (42.5–54.4% and 13.7–43.1%) and triacylglycerols (35.4–45.8% and 44.6–59.4%). Cholesterol was the major sterol (70.90–98.58% and 97.10–98.31% of total sterols in muscle and cephalothorax respectively) followed by avenasterol (0.18–20.32% and 0.07–0.70%) and β-sitosterol (0.29–7.30% and 0.23–0.75%). Lower concentrations of brassicasterol, stigmasterol, Δ7-stigmasterol, campesterol and campestanol were also found. The examined crustaceans muscle (edible part) was found to be a good ω-3 PUFA source for the consumers, while the cephalothorax (which is usually discarded) could be used effectively as a source for ω-3 PUFA production. 相似文献
588.
Food safety knowledge, attitudes, and behaviors among Puerto Rican caretakers living in Hartford, Connecticut 总被引:2,自引:0,他引:2
Bermúdez-Millán A Pérez-Escamilla R Damio G González A Segura-Pérez S 《Journal of food protection》2004,67(3):512-516
Household food safety education is needed to minimize the risk of exposure to foodborne pathogens. The Latino population in the United States is growing at a fast rate and has become the largest minority group in this country. However, little research has been done to identify the food safety behavioral risks faced by Puerto Ricans. Ten in-depth household observations and a quantitative survey on food safety knowledge, attitudes, and behaviors (n = 100) were conducted to understand food-handling techniques among Puerto Rican caretakers of young children. This was followed by two focus groups (n = 12) to further characterize food safety knowledge, attitudes, and behaviors and the proper media channels for the delivery of food safety education. Even though 97% of survey participants reported washing their hands with soap and water before preparing foods, only 1 of the 10 participants in the household observations actually did it. About 60% of the household participants washed the cutting boards with soap and water compared with 89% of survey participants who claimed to do it. In the survey, 5% reported to know the meaning of cross-contamination, and 71% (n = 80) to use the same cutting board for meats and vegetables. Overall, 96% of survey participants did not use a thermometer to check if meats were cooked properly and only 10% defrosted their meats in the refrigerator. Statistically significant relationships (P < 0.05) were found between speaking English and knowing the meaning of cross-contamination and how to use a meat thermometer. Employed individuals and those with higher education were also more likely to be familiar with the term pasteurization. These results fully justify the delivery of culturally appropriate food safety education in this community. 相似文献
589.
Ana Sofia Ferreira Catarina Macedo Ana Margarida Silva Cristina Delerue-Matos Paulo Costa Francisca Rodrigues 《International journal of molecular sciences》2022,23(8)
Cancer, a major world public health problem, is associated with chemotherapy treatments whose administration leads to secondary concerns, such as oral mucositis (OM). The OM disorder is characterized by the presence of ulcers in the oral mucosa that cause pain, bleeding, and difficulty in ingesting fluids and solids, or speaking. Bioactive compounds from natural sources have arisen as an effective approach for OM. This review aims to summarize the new potential application of different natural products in the prevention and treatment of OM in comparison to conventional ones, also providing a deep insight into the most recent clinical studies. Natural products, such as Aloe vera, Glycyrrhiza glabra, Camellia sinensis, Calendula officinalis, or honeybee crops, constitute examples of sources of bioactive compounds with pharmacological interest due to their well-reported activities (e.g., antimicrobial, antiviral, anti-inflammatory, analgesic, or wound healing). These activities are associated with the bioactive compounds present in their matrix (such as flavonoids), which are associated with in vivo biological activities and minimal or absent toxicity. Finally, encapsulation has arisen as a future opportunity to preserve the chemical stability and the drug bioa vailability of bioactive compounds and, most importantly, to improve the buccal retention period and the therapeutic effects. 相似文献
590.
Maria Tsivilika Dimitrios Kavvadas Sofia Karachrysafi Katerina Kotzampassi Vasilis Grosomanidis Eleni Doumaki Soultana Meditskou Antonia Sioga Theodora Papamitsou 《International journal of molecular sciences》2022,23(11)
Background: This study aims to investigate the probable lesions and injuries induced in the renal tissue after a cardiac arrest. The renal ischemia–reperfusion model in cardiac arrest describes the effects of ischemia in the kidneys, alongside a whole-body ischemia–reperfusion injury. This protocol excludes ischemic conditions caused by surgical vascular manipulation, venous injury or venous congestion. Methods: For the experimental study, 24 swine were subjected to cardiac arrest. Seven minutes later, the cardiopulmonary resuscitation technique was performed for 5 min. Afterwards, advanced life support was provided. The resuscitated swine consisted one group and the non-resuscitated the other. Tissue samples were obtained from both groups for light and electron microscopy evaluation. Results: Tissue lesions were observed in the tubules, parallel to destruction of the microvilli, reduction in the basal membrane invaginations, enlarged mitochondria, cellular vacuolization, cellular apoptosis and disorganization. In addition, fusion of the podocytes, destruction of the Bowman’s capsule parietal epithelium and abnormal peripheral urinary space was observed. The damage appeared more extensive in the non-resuscitated swine group. Conclusions: Acute kidney injury is not the leading cause of death after cardiac arrest. However, evidence suggests that the kidney damage after a cardiac arrest should be highly considered in the prognosis of the patients’ health outcome. 相似文献