全文获取类型
收费全文 | 633篇 |
免费 | 63篇 |
专业分类
电工技术 | 4篇 |
化学工业 | 186篇 |
金属工艺 | 19篇 |
机械仪表 | 44篇 |
建筑科学 | 17篇 |
矿业工程 | 1篇 |
能源动力 | 19篇 |
轻工业 | 129篇 |
水利工程 | 10篇 |
石油天然气 | 5篇 |
无线电 | 33篇 |
一般工业技术 | 110篇 |
冶金工业 | 14篇 |
原子能技术 | 4篇 |
自动化技术 | 101篇 |
出版年
2024年 | 2篇 |
2023年 | 12篇 |
2022年 | 28篇 |
2021年 | 45篇 |
2020年 | 41篇 |
2019年 | 41篇 |
2018年 | 66篇 |
2017年 | 40篇 |
2016年 | 44篇 |
2015年 | 28篇 |
2014年 | 35篇 |
2013年 | 65篇 |
2012年 | 46篇 |
2011年 | 58篇 |
2010年 | 21篇 |
2009年 | 23篇 |
2008年 | 24篇 |
2007年 | 15篇 |
2006年 | 11篇 |
2005年 | 5篇 |
2004年 | 9篇 |
2003年 | 7篇 |
2002年 | 4篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1985年 | 1篇 |
排序方式: 共有696条查询结果,搜索用时 15 毫秒
121.
Developing Smart Grids Based on GPRS and ZigBee Technologies Using Queueing Modeling–Based Optimization Algorithm
下载免费PDF全文
![点击此处可从《ETRI Journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Gustavo Batista de Castro Souza Flávio Henrique Teles Vieira Cláudio Ribeiro Lima Getúlio Antero de Júnior Deus Marcelo Stehling de Castro Sérgio Granato de Araujo Thiago Lara Vasques 《ETRI Journal》2016,38(1):41-51
Smart metering systems have become widespread around the world. RF mesh communication systems have contributed to the creation of smarter and more reliable power systems. This paper presents an algorithm for positioning GPRS concentrators to attain delay constraints for a ZigBee‐based mesh network. The proposed algorithm determines the number and placement of concentrators using integer linear programming and a queueing model for the given mesh network. The solutions given by the proposed algorithm are validated by verifying the communication network performance through simulations. 相似文献
122.
Andrey Chaves Jusciane da Costa e Silva José Alexander de King Freire Marcos Henrique Degani Valder Nogueira Freire Gil de Aquino Farias 《Journal of Materials Science》2007,42(7):2314-2317
The exciton properties of Si/Si 1-x Ge x cylindrical quantum wires (QWRs) are calculated using the variational method and taking into account the existence of an interface layer between the materials. We consider two possibilities for the conduction band lineup, type-I and type-II. Our numerical results show that an interfacial fluctuation of 15Å in a Si 0.85 Ge 0.15 (Si0.70Ge0.30) type-I (type-II) wire of 50Å wire radius leads to an exciton energy blue shift of the order of 10 (10) meV. 相似文献
123.
Christian Limberg Joaquim Henrique Teles 《Advanced Synthesis \u0026amp; Catalysis》2001,343(5):447-449
A solution of RuCl3 in concentrated hydrochloric acid is capable of chlorinating aromatic compounds catalytically, if O2is present as the oxidizing agent (brominations can be achieved in hydrobromic acid). When olefins are chosen as substrates, two Cl atoms are added to the double bond in an anti fashion, while hydrochlorination products are formed simultaneously. According to the products observed in both types of reactions for various substrates in this 3‐phase system, the halogenations proceed via electrophilic pathways. 相似文献
124.
Mnica Carcuchinski Haag Joo Henrique Zimnoch dos Santos Jairton Dupont Argimiro Resende Secchi 《应用聚合物科学杂志》1998,70(6):1173-1189
The development of a simplified kinetic model describing some effects observed in catalyzed olefin terpolymerization is presented. Based on the method of moments, the model describes the influence of Al/V ratio and diene concentration on reaction yield and on polymer characteristics such as molecular weight, ethylene incorporation, and polydispersity. In order to verify the model validity, the terpolymerization reactions were performed using VOCl3–Al2Et3Cl3 systems and 2-ethylidenebi-cyclo[2.2.1]hept-5-ene (ENB) as diene. The results of dynamic simulation fit well the experimental data for Al/V up to 15, but the model fails under high diene concentration, where branching reactions, neglected by reason of simplification, become significant. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 1173–1189, 1998 相似文献
125.
Gilberto V Kozloski Joo BT Rocha Henrique M
N Ribeiro Filho Juliano Perottoni 《Journal of the science of food and agriculture》1999,79(8):1112-1116
Enzymatic methods (amyloglucosidase) and methods based on acid solutions (0.1, 0.2 and 0.3 M H2SO4 for 1, 2 and 3 h at 100 °C) for the hydrolysis of non‐structural carbohydrates from different feed samples were compared. The monomeric units resulting from the enzymatic and acid hydrolysis were determined by the glucose oxidase and reducing sugar methods. There was a significant effect of acid concentration and of time of hydrolysis on the glucose and reducing sugar values in the hydrolysate. Glucose values were similar for both the amyloglucosidase method and the most intense conditions of hydrolysis (0.3 M for 3 h) for some samples. Under these conditions, however, the reducing sugar values were higher. No acid hydrolysis method was found to estimate correctly the total non‐structural carbohydrates, but α‐linked glucose polymers in biological samples may be determined by sample hydrolysis with a 0.3 M H2SO4 solution for 3 h at 100 °C since the glucose in the hydrolysate is determined by the glucose oxidase method and the sucrose content of the sample is negligible. © 1999 Society of Chemical Industry 相似文献
126.
Chiara Micheletti Pedro Henrique Silva Gomes-Ferreira Travis Casagrande Paulo Noronha Lisboa-Filho Roberta Okamoto Kathryn Grandfield 《Journal of the Royal Society Interface》2021,18(182)
The success of biomaterials for bone regeneration relies on many factors, among which osseointegration plays a key role. Biogran (BG) is a bioactive glass commonly employed as a bone graft in dental procedures. Despite its use in clinical practice, the capability of BG to promote osseointegration has never been resolved at the nanoscale. In this paper, we present the workflow for characterizing the interface between newly formed bone and BG in a preclinical rat model. Areas of bone–BG contact were first identified by backscattered electron imaging in a scanning electron microscope. A focused ion beam in situ lift-out protocol was employed to prepare ultrathin samples for transmission electron microscopy analysis. The bone–BG gradual interface, i.e. the biointerphase, was visualized at the nanoscale with unprecedented resolution thanks to scanning transmission electron microscopy. Finally, we present a method to view the bone–BG interface in three dimensions using electron tomography. 相似文献
127.
Meso-tetrapyridylporphyrins peripherally coordinated to four ruthenium complexes, such as [Ru(bpy)2Cl] and [Ru(5-ClPhen)2Cl] (bpy = 2,2'-bipyridine; Phen = 1,10-phenanthroline), provide a versatile class of molecular materials in which the complexes act as co-factors, inducing electronic effects and acting as electron-transfer relays and electron pools or sinks, depending upon their oxidation state. These cationic porphyrins can be assembled into thin films by conventional methods, or into organized layer-by-layer structures by combining with negatively charged tetrasulfonated porphyrins or phthalocyanines. Their electrocatalytic and photoelectrochemical properties have been successfully exploited in chemical sensors. Their usefulness in molecular logic gates are being demonstrated by using modified transparent conducting electrodes in miniaturized flow injection cells. In such designs, the chemical, electrochemical, and light inputs can be readily combined to perform the basic logic functions, such as AND, OR, and NOT, for molecular computing. 相似文献
128.
Marco Aurélio Bazelatto Zanoni Henrique Massard Márcio Ferreira Martins 《Combustion and Flame》2012,159(10):3224-3234
Enhanced technologies from oil recovery to unconventional fuels - oil shale, oil sands and extra-heavy oil – have in common complex chemical reactions processes. This paper is about the formulation and optimization of the chemical mechanism especially in oil shale and semi-coke combustion. The Levenberg–Marquardt algorithm was used to minimize the error between estimated values and the thermogravimetric data for combustion mechanisms of 4-steps and 3-steps proposed for the oil shale and its semi-coke respectively. The kinetic parameters such as reaction order, pre-exponential factor, activation energy and stoichiometric coefficients that affect drying, pyrolysis, oxidation and decarbonation reactions were estimated with success. The values of activation energies were 54–67 kJ mol?1 for oil shale drying, 62–65 kJ mol?1 for pyrolysis reaction, up to 100 kJ mol?1 for Fixed Carbon (FC) oxidation reaction, and 162–418 kJ mol?1 for decarbonation reaction. Regarding to the semi-coke combustion, the activation energies were 33 kJ mol?1 for drying reaction, 211 kJ mol?1 for oxidation reaction and 291 kJ mol?1 for decarbonation reaction. The chemical reactions suggest reaction order superior to one, except to the decarbonation reaction at 3 K min?1. Considering the estimated parameters, as well as a heating rate at 3 K min?1, an oil shale containing about 20 wt.% of organic matter and 34.6 wt.% of CaCO3, the species mass fractions formed during combustion process were 3.4 wt.% of FC, 10.6 wt.% of Oil, 3.3 wt.% of HC and 1.8 wt.% of CO. The fraction of CO2 formed accounts a total of 21.6 wt.%. For a semi-coke containing 3.4 wt.% of FC and 40.6 wt.% of CaCO3, its combustion formed 2.1 wt.% of CO. The CO2 fraction from oxidation and decarbonation reactions accounts 10.2 wt.%, considering that the stoichiometric mass coefficient γ = 0.75 in decarbonation reaction. 相似文献
129.
Marcelo Rodrigues da SilvaMarcelo Silva Ferreira Luiz Henrique Dall'Antonia 《Thin solid films》2012,520(20):6424-6428
The present paper describes the utilization of polypyrrole and the composite of polypyrrole doped with nickel hydroxide modified electrodes toward the catalytic oxidation of ascorbate. Films were potentiostatically deposited onto a glassy carbon surface and Fluor-doped tin oxide glass for different times. The physical characterization was performed using the low angle X-ray diffraction technique. Furthermore, the films were electrochemically characterized using cyclic voltammetry. The X-ray diffraction results show the existence of different polymorphic phases of nickel hydroxide in the polymer matrix, and the β-Ni(OH)2 phase appears to be dominant. The cyclic voltammetry profile in KOH solution shows the presence of two redox peaks that are related to the NiII/NiIII and NiIII/NiII couples, at approximately 0.5 and 0.35 V, respectively. The reversible electro-oxidation of ascorbate was observed on the surface of the polypyrrole and composite films. The analytical curves obtained using voltammetric techniques show a linear relationship between the faradaic current and the increase of the ascorbic acid concentration. The sensitivity of these films, which is obtained from the slope of the analytical curves, shows that the composite film is more electroactive than the polypyrrole film: 133.4 mA L mol− 1 cm− 2 and 83.8 mA L mol− 1 cm− 2, respectively. The rate constants of the catalytic ascorbate electro-oxidation were also reported, where the mean values were found to be 217.74 M− 1 s− 1 and 54.37 M− 1 s− 1, for the composite and polypyrrole films, respectively. The low cost of polypyrrole doped with Ni(OH)2 composite electrodes presents a more selective and high sensitivity to determine ascorbic acid concentration. 相似文献
130.
Antunes AM Alencar MS da Silva CH Nunes J Mendes FM 《Recent patents on nanotechnology》2012,6(1):29-43
The aim of the article is to present a method for identifying trends in patent applications for nanotechnology applied to the health sector around the world, based on the International Patent Classification. This classification divides the sector into: dental care, drugs, diagnostic kits, and medical apparatus & medical care. The Derwent database was mined for patent documents using nanotechnology terms associated with the IPC subclasses from the health subsectors. The number of patents was found to be rising, led by the United States, particularly universities and R centers. In the dental care subsector, nanotechnology was found to be used in composite material for manufacturing dental appliances. In drugs, the focus is on the use of nanoparticulate compositions comprising agents that are useful for a variety of diseases. In diagnostic kits, nanostructures have been patented that are capable of detecting target analytes. Meanwhile, in medical apparatus & medical care, patent applications have been made for nanocapsules and/or nanocomposite materials inserted in devices and guide catheters. A study was also made of patents in Brazil, where the same assignees and the same country (United States) as in the survey of global patents were found to be the leading patent applicants / holders. 相似文献