全文获取类型
收费全文 | 3454篇 |
免费 | 357篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 8篇 |
综合类 | 21篇 |
化学工业 | 253篇 |
金属工艺 | 12篇 |
机械仪表 | 17篇 |
建筑科学 | 9篇 |
矿业工程 | 13篇 |
能源动力 | 126篇 |
轻工业 | 2891篇 |
水利工程 | 32篇 |
石油天然气 | 238篇 |
无线电 | 22篇 |
一般工业技术 | 92篇 |
冶金工业 | 6篇 |
原子能技术 | 2篇 |
自动化技术 | 73篇 |
出版年
2024年 | 29篇 |
2023年 | 258篇 |
2022年 | 288篇 |
2021年 | 284篇 |
2020年 | 265篇 |
2019年 | 224篇 |
2018年 | 231篇 |
2017年 | 217篇 |
2016年 | 206篇 |
2015年 | 216篇 |
2014年 | 246篇 |
2013年 | 185篇 |
2012年 | 207篇 |
2011年 | 158篇 |
2010年 | 117篇 |
2009年 | 89篇 |
2008年 | 31篇 |
2007年 | 115篇 |
2006年 | 85篇 |
2005年 | 70篇 |
2004年 | 27篇 |
2003年 | 41篇 |
2002年 | 41篇 |
2001年 | 58篇 |
2000年 | 22篇 |
1999年 | 20篇 |
1998年 | 18篇 |
1997年 | 6篇 |
1996年 | 14篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1982年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有3815条查询结果,搜索用时 109 毫秒
41.
Performing catalysts have been synthetized through incipient wet impregnation and tested for cis,cis-muconic acid hydrogenation to adipic acid. The activity of Pt-based catalysts has been compared with an Ni-based catalyst at a gentle condition. A supported 14.2 wt% Ni on γ-alumina converted 100% of muconic acid, yielding 99.4 mol% of adipic acid. 相似文献
42.
The efficient utilization of lignocellulosic biomass and the reduction of production cost are mandatory to attain a cost-effective lignocellulose-to-ethanol process. The selection of suitable pretreatment that allows an effective fractionation of biomass and the use of pretreated material at high-solid loadings on saccharification and fermentation (SSF) processes are considered promising strategies for that purpose. Eucalyptus globulus wood was fractionated by organosolv process at 200 °C for 69 min using 56% of glycerol-water. A 99% of cellulose remained in pretreated biomass and 65% of lignin was solubilized. Precipitated lignin was characterized for chemical composition and thermal behavior, showing similar features to commercial lignin. In order to produce lignocellulosic ethanol at high-gravity, a full factory design was carried to assess the liquid to solid ratio (3–9 g/g) and enzyme to solid ratio (8–16 FPU/g) on SSF of delignified Eucalyptus. High ethanol concentration (94 g/L) corresponding to 77% of conversion at 16FPU/g and LSR = 3 g/g using an industrial and thermotolerant Saccharomyces cerevisiae strain was successfully produced from pretreated biomass. Process integration of a suitable pretreatment, which allows for whole biomass valorization, with intensified saccharification-fermentation stages was shown to be feasible strategy for the co-production of high ethanol titers, oligosaccharides and lignin paving the way for cost-effective Eucalyptus biorefinery. 相似文献
43.
A silver nanoparticle composite based on modified polyallylamine has been synthesized by a simple chemical route and its catalytic activity has been tested for alkyne–azide cycloaddition reaction. This silver nanocomposite shows an excellent catalytic activity at 80 °C for the synthesis of 1,4-disubstituted 1,2,3-triazole by alkyne–azide cycloaddition. The solid silver nanocomposite catalyst was characterized by transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffractometry and thermogravimetric analysis. The developed catalyst is stable in air, easy to prepare and can be recovered easily and reused ten times without a significant decrease in activity. 相似文献
44.
45.
Rice straw is a promising renewable energy source because it is abundantly available in Asia. This study conducted a case study of logistics cost analysis for rice straw pellets by considering all stages in the supply chain to define the main factors affecting the selling price of rice straw pellets: collection (job-commission or employment of part-time workers), transportation, storage (vinyl greenhouses or storage buildings with larger capacity), pelletizing, and delivery to users with biomass boilers. The selling price was found to be strongly dependent on the production capacity because the investment cost for the pellet production facility had a significant effect of economies of scale. A production capacity of larger than 1500 t y−1 is required for rice straw pellets to compete with wood pellets and fossil fuels in the studied Japanese context if the subsidy rate for the investment is 50%, part-time workers conduct the collection, and rice straw is stored in the storage buildings. Our sensitivity analysis also showed an economically feasible spatial scale: for example, rice straw should be collected within a 20 km radius and the users should be within a 38 km radius when the production capacity is 1500 t y−1. In addition, other critical factors related to the collection of rice straw from the paddy fields and transportation of rice straw rolls to storage were identified as planning factors to further reduce the total logistics cost of rice straw pellets. 相似文献
46.
The aim of this study was to investigate the antioxidant, anti-ACE and antibacterial activities of smooth hound viscera hydrolysates (SHVHs). Viscera, as by-product, were hydrolyzed with crude alkaline protease extract from the same species, three commercial proteases and a combination endogenous and exogenous preparations. Hydrolysates showed different degrees of hydrolysis and the digestion with endogenous enzymes in combination with commercial proteases was found to enhance protein hydrolysis. The resulting SHVHs had high protein content (70.89%–89.06%) and they were mainly constituted by Gly, Glu and Gln, while Tau was the major free amino acid. In addition, they contained high amounts of UMP, Uridine, GMP and Guanosine, while undigested proteins were mainly rich in IMP and Xanthine. Furthermore, SHVHs showed different molecular mass distribution and RP-HPLC profiles proving their molecular mass and hydrophilic/hydrophobic peptide heterogeneity. All the SHVHs exhibited antioxidant activity, in terms of radical-scavenging activity, reducing power, metal chelating activity, β-carotene protection, lipid peroxidation inhibition and DNA breakage assay, and it was found that a medium degree of hydrolysis was appropriate to obtain hydrolysates with good antioxidant capacity. In addition, the SHVHs antioxidant activity was improved after simulated gastrointestinal digestion. Besides their antibacterial effect against several Gram-positive and Gram-negative bacteria, all the hydrolysates showed varying degrees of ACE inhibitory activities and the highest one was achieved by the Purafect hydrolysate (IC50 = 75 μg/mL). The overall data suggested that the SHVHs could be used as potential source of natural antioxidant, antimicrobial and anti-ACE peptides to formulate functional foods. 相似文献
47.
48.
《International Dairy Journal》2014,36(2):145-152
The acquisition of amino acids by Lactobacillus delbrueckii subsp. bulgaricus 2038 (Lb. bulgaricus 2038) when grown in the presence of bovine casein, the major protein in bovine milk, was investigated by examining the expression of genes related to proteolysis and amino acid biosynthesis. To support the growth on bovine casein, Lb. bulgaricus 2038 has to synthesise five kinds of amino acids de novo, as proteolysis from casein does not provide these. The incomplete hydrolysis in combination with amino acids biosynthesis may explain the slow growth of Lb. bulgaricus 2038 in a casein environment. Meanwhile, it was determined that Lb. bulgaricus 2038 uses different intracellular peptidases when grown in casein or whey medium, and initially yields the important amino acid glutamate from the C-terminal or N-terminal end of peptides imported into the cell. 相似文献
49.
An interposed “phage filtration” process step is proposed prior to subsequent processing of cheese whey to whey products to reduce fermentation risks due to phage contamination. At laboratory scale, the characteristics of three single tube ceramic membranes on the filtration performance in terms of phage retention, protein transmission and filtrate flux were analysed. From these tested membranes, a 0.1 μm microfiltration membrane was found to be suitable for significant phage reduction (3.4 log units) in cheese whey, simultaneously allowing total protein transmission of 56.2%. The experiments within the designed feasibility study conducted with a pilot plant microfiltration system provided a higher phage retention (4.1 log units) and a significantly increased transmission of major whey proteins (up to 84%) in comparison with the laboratory plant. The results shown in this study can easily be adapted by the dairy industry for better phage control and enhanced process safety. 相似文献
50.
《Food Control》2014
In the present study, 78 lactic acid bacteria (LAB) strains were screened for the antagonistic activity against Campylobacter jejuni and 15 LAB strains with high bactericidal capacity were selected for further study through the analysis of the inhibition zone of LAB spent culture supernatant on the growth of C. jejuni. Among these strains, four isolates, Lactobacillus plantarum N8, N9, ZL5 and Lactobacillus casei ZL4 exhibited high adhesion ability to HT-29 cells. All the cell free supernatant (CFS) of these four strains contained high concentration of organic acid and their inhibition effects against C. jejuni were pH sensitive. Furthermore, these four strains could strongly antagonize the adhesion and invasion of C. jejuni to HT-29 cells and showed good tolerance to artificial gastric and small intestinal juices. This study suggests that Lactobacillus strains N8, N9, ZL4 and ZL5 could be used as potential probiotics in food applications against C. jejuni infection. 相似文献