全文获取类型
收费全文 | 2378篇 |
免费 | 24篇 |
国内免费 | 16篇 |
专业分类
电工技术 | 21篇 |
综合类 | 10篇 |
化学工业 | 170篇 |
金属工艺 | 22篇 |
机械仪表 | 25篇 |
建筑科学 | 61篇 |
矿业工程 | 4篇 |
能源动力 | 16篇 |
轻工业 | 126篇 |
水利工程 | 7篇 |
石油天然气 | 6篇 |
武器工业 | 1篇 |
无线电 | 61篇 |
一般工业技术 | 98篇 |
冶金工业 | 1680篇 |
原子能技术 | 13篇 |
自动化技术 | 97篇 |
出版年
2021年 | 11篇 |
2019年 | 10篇 |
2018年 | 8篇 |
2017年 | 10篇 |
2016年 | 8篇 |
2015年 | 15篇 |
2014年 | 21篇 |
2013年 | 41篇 |
2012年 | 26篇 |
2011年 | 21篇 |
2010年 | 34篇 |
2009年 | 35篇 |
2008年 | 24篇 |
2007年 | 36篇 |
2006年 | 19篇 |
2005年 | 57篇 |
2004年 | 15篇 |
2003年 | 24篇 |
2002年 | 21篇 |
2001年 | 19篇 |
2000年 | 17篇 |
1999年 | 62篇 |
1998年 | 485篇 |
1997年 | 293篇 |
1996年 | 198篇 |
1995年 | 104篇 |
1994年 | 99篇 |
1993年 | 100篇 |
1992年 | 17篇 |
1991年 | 27篇 |
1990年 | 20篇 |
1989年 | 28篇 |
1988年 | 34篇 |
1987年 | 30篇 |
1986年 | 23篇 |
1985年 | 32篇 |
1984年 | 16篇 |
1983年 | 24篇 |
1982年 | 21篇 |
1981年 | 16篇 |
1980年 | 25篇 |
1979年 | 12篇 |
1978年 | 13篇 |
1977年 | 56篇 |
1976年 | 121篇 |
1975年 | 22篇 |
1974年 | 9篇 |
1973年 | 9篇 |
1971年 | 6篇 |
1970年 | 5篇 |
排序方式: 共有2418条查询结果,搜索用时 15 毫秒
81.
82.
The influence of toughener and clay concentration on the morphology and mechanical properties of three-phase, rubber-modified epoxy nanocomposites was studied. Nanocomposite samples were prepared by adding octadecyl ammonium ion exchanged clay to a dispersion of pre-formed acrylic rubber particles in liquid epoxy, so as to minimize alteration to the rubber morphology in the final cured specimen. The state of clay platelet exfoliation and rubber dispersion in the cured nanocomposites was studied using transmission electron microscopy. The amounts of clay platelet separation and dispersion of clay aggregates in the epoxy matrix were found to be sensitive to clay and toughener concentration, and clay platelets preferentially adsorb to the rubber particles. Tensile modulus and strength increase and ductility decreases with increasing organoclay content, while rubber has the opposite effects on the properties of epoxy resin. When both additives are present in epoxy resin, a favorable combination is produced: ductility is enhanced without compromising modulus and strength. Modulus and strength are improved by nano and micro dispersion of nanoclay in the epoxy matrix, whereas elongation and toughness are improved by clay adsorption to the rubber particle surface, which promotes cavitation. The glass transition temperature of epoxy resin remains relatively unchanged with clay addition. 相似文献
83.
The activity and mechanism of uranium oxide catalysts for the oxidative destruction of volatile organic compounds 总被引:8,自引:0,他引:8
Stuart H. Taylor Catherine S. Heneghan Graham J. Hutchings Ian D. Hudson 《Catalysis Today》2000,59(3-4):249-259
Uranium oxide based catalysts have been investigated for the oxidative destruction of volatile organic compounds (VOCs) to carbon oxides and water. The catalysts have been tested for the destruction of a range of organic compounds at space velocities up to 70 000 h−1. Destruction efficiencies greater than 99% can be achieved over the appropriate uranium based catalyst in the temperature range 300–450°C. Volatile organic compounds investigated include benzene, butylacetate, cyclohexanone, toluene, methanol, acetylene, butane, chlorobutane and chlorobenzene. The catalysts are thermally stable, destroy low concentrations and mixtures of VOCs and lifetime studies indicate that deactivation during oxidation of chlorinated VOCs did not occur. A temporal analysis of products (TAPs) reactor is used to investigate the mechanism of oxidation of VOCs by uranium oxide catalysts. Studies indicated that VOCs were oxidised directly to carbon oxides on the catalyst surface. A combination of TAP pulse experiments with oxygen present and absent in the gas phase has indicated that the lattice oxygen from the catalyst is responsible for the total oxidation activity. This has been confirmed by studies using isotopically labelled oxygen which indicates that the catalyst operates by a redox mechanism. 相似文献
84.
85.
环氧丙烯酸树脂的合成及其改性 总被引:2,自引:0,他引:2
采用丙烯酸(AA)对环氧树脂(EP)进行光活性改性制备环氧丙烯酸树脂(EA),通过单因素试验法优选出制备EA的最佳反应条件。结果表明:制备EA的最佳反应条件是以N′N-二甲基苯胺为催化剂,w(催化剂)=2.5%(相对于反应物总质量而言);以对苯二酚为阻聚剂,w(阻聚剂)=0.1%(相对于反应物总质量而言);反应温度为90℃,反应时间为2.0~3.5h。当w(引发剂)=1.0%时,EA的固化性能较好。采用多元醇先对EP进行改性,然后再进行光活性改性,可明显降低产物的黏度。 相似文献
86.
N. Ni D. Hudson J. Wei P. Wang S. Lozano-Perez G.D.W. Smith J.M. Sykes S.S. Yardley K.L. Moore S. Lyon R. Cottis M. Preuss C.R.M. Grovenor 《Acta Materialia》2012,60(20):7132-7149
Aqueous corrosion and hydrogenation have become major limiting factors to the use of zirconium alloys as fuel cladding and assembly components in water-cooled nuclear reactors. The metal–oxide interface has been a particular focus of previous research, but there is still no clear understanding of what is present at the interface at different stages of the complex oxidation process. We report here a systematic investigation using state-of-the-art instrumentation on the interfaces in several zirconium alloys corroded for different times. We have shown that thin intermediate oxide layers with compositions close to ZrO can be observed in almost all the pre-transition samples studied, and that this layer thickens during the pre-transition stage. Just before the kinetic transition, a large variation in the suboxide width was detected, suggesting that the kinetic transition is an extremely local process. After transition the suboxide was generally absent. In the suboxide locations different structures, including an unidentified phase, were found. The oxygen-saturated (~30 at.% O) metal regions found beneath the oxide are thickest in the (late) pre-transition samples and significantly thinner in the post-transition samples. We suggest that the suboxide cannot by itself act as a protective layer and conclude that it is the development of interlinked porosity down to the metal–oxide interface that is the reason for the transition in oxidation kinetics. 相似文献
87.
Matthew Cooke Mike Iosia Thomas Buford Brian Shelmadine Geoffrey Hudson Chad Kerksick Christopher Rasmussen Mike Greenwood Brian Leutholtz Darryn Willoughby Richard Kreider 《Journal of the International Society of Sports Nutrition》2008,5(1):1-14
Background
To determine whether acute (single dose) and/or chronic (14-days) supplementation of CoQ10 will improve anaerobic and/or aerobic exercise performance by increasing plasma and muscle CoQ10 concentrations within trained and untrained individuals.Methods
Twenty-two aerobically trained and nineteen untrained male and female subjects (26.1 ± 7.6 yrs, 172 ± 8.7 cm, 73.5 ± 17 kg, and 21.2 ± 7.0%) were randomized to ingest in a double-blind manner either 100 mg of a dextrose placebo (CON) or a fast-melt CoQ10 supplement (CoQ10) twice a day for 14-days. On the first day of supplementation, subjects donated fasting blood samples and a muscle biopsy. Subjects were then given 200 mg of the placebo or the CoQ10 supplement. Sixty minutes following supplement ingestion, subjects completed an isokinetic knee extension endurance test, a 30-second wingate anaerobic capacity test, and a maximal cardiopulmonary graded exercise test interspersed with 30-minutes of recovery. Additional blood samples were taken immediately following each exercise test and a second muscle biopsy sample was taken following the final exercise test. Subjects consumed twice daily (morning and night), 100 mg of either supplement for a period of 14-days, and then returned to the lab to complete the same battery of tests. Data was analyzed using repeated measures ANOVA with an alpha of 0.05.Results
Plasma CoQ10 levels were significantly increased following 2 weeks of CoQ10 supplementation (p < 0.001); while a trend for higher muscle CoQ10 levels was observed after acute CoQ10 ingestion (p = 0.098). A trend for lower serum superoxide dismutase (SOD) was observed following acute supplementation with CoQ10 (p = 0.06), whereas serum malondialdehyde (MDA) tended to be significantly higher (p < 0.05). Following acute ingestion of CoQ10, plasma CoQ10 levels were significantly correlated to muscle CoQ10 levels; maximal oxygen consumption; and treadmill time to exhaustion. A trend for increased time to exhaustion was observed following 2 weeks of CoQ10 supplementation (p = 0.06).Conclusion
Acute supplementation with CoQ10 resulted in higher muscle CoQ10 concentration, lower serum SOD oxidative stress, and higher MDA levels during and following exercise. Chronic CoQ10 supplementation increased plasma CoQ10 concentrations and tended to increase time to exhaustion. Results indicate that acute and chronic supplementation of CoQ10 may affect acute and/or chronic responses to various types of exercise. 相似文献88.
89.
Dr. Anders Højgaard Hansen Henriette B. Christensen Dr. Sunil K. Pandey Dr. Eugenia Sergeev Alice Valentini Julia Dunlop Domonkos Dedeo Simone Fratta Dr. Brian D. Hudson Prof. Graeme Milligan Prof. Trond Ulven Prof. Elisabeth Rexen Ulven 《ChemMedChem》2021,16(21):3326-3341
Free fatty acid receptor 2 (FFA2) is a sensor for short-chain fatty acids that has been identified as an interesting potential drug target for treatment of metabolic and inflammatory diseases. Although several ligand series are known for the receptor, there is still a need for improved compounds. One of the most potent and frequently used antagonists is the amide-substituted phenylbutanoic acid known as CATPB ( 1 ). We here report the structure-activity relationship exploration of this compound, leading to the identification of homologues with increased potency. The preferred compound 37 (TUG-1958) was found, besides improved potency, to have high solubility and favorable pharmacokinetic properties. 相似文献
90.
Erik L. Gaskin Militza Carrero-Colón Karen A. Hudson 《Journal of the American Oil Chemists' Society》2021,98(2):221-226
Stearic acid is one of five major fatty acids found in soybean oil. It is a fully saturated lipid and is known for neutral or positive effects on LDL cholesterol when consumed by humans. Unfortunately, stearic acid only accounts for about 4% of the total seed oil produced in commodity soybean. Previous work has shown that stearic acid can reach levels as high as 28% of the total oil fraction when the SACPD-C gene, encoding the delta-9-stearoyl-acyl carrier protein desaturase responsible for most of the stearic acid variation in soybean seed, is ablated in combination with other loci. In order to increase stearic acid content and create soybeans with improved utility based on fatty acid composition, we combined mutations in SACPD-C with other mutations in the fatty acid biosynthetic pathway. Soybean plants carrying mutant alleles of both SACPD-C and FAD2-1A produce seed with stearic acid levels from 14% to 21%, and with elevated levels of oleic acid. Soybeans carrying mutations in both SACPD-C and FAD3A or FAD3C have both statistically significantly elevated levels of stearic acid (from 15–21%) and statistically reduced linolenic acid levels. Neither mutant combination appears to affect other agronomic properties such as plant morphology or seed protein levels making this a potentially viable trait. 相似文献