全文获取类型
收费全文 | 765篇 |
免费 | 21篇 |
专业分类
电工技术 | 14篇 |
综合类 | 1篇 |
化学工业 | 153篇 |
金属工艺 | 22篇 |
机械仪表 | 25篇 |
建筑科学 | 45篇 |
矿业工程 | 6篇 |
能源动力 | 32篇 |
轻工业 | 84篇 |
水利工程 | 8篇 |
无线电 | 88篇 |
一般工业技术 | 117篇 |
冶金工业 | 117篇 |
原子能技术 | 9篇 |
自动化技术 | 65篇 |
出版年
2022年 | 10篇 |
2021年 | 12篇 |
2020年 | 5篇 |
2019年 | 12篇 |
2018年 | 10篇 |
2017年 | 8篇 |
2016年 | 18篇 |
2015年 | 12篇 |
2014年 | 21篇 |
2013年 | 41篇 |
2012年 | 23篇 |
2011年 | 37篇 |
2010年 | 36篇 |
2009年 | 29篇 |
2008年 | 28篇 |
2007年 | 22篇 |
2006年 | 37篇 |
2005年 | 29篇 |
2004年 | 26篇 |
2003年 | 27篇 |
2002年 | 16篇 |
2001年 | 28篇 |
2000年 | 18篇 |
1999年 | 16篇 |
1998年 | 23篇 |
1997年 | 24篇 |
1996年 | 11篇 |
1995年 | 12篇 |
1994年 | 18篇 |
1993年 | 9篇 |
1992年 | 5篇 |
1991年 | 12篇 |
1990年 | 10篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 9篇 |
1985年 | 6篇 |
1984年 | 11篇 |
1983年 | 4篇 |
1982年 | 10篇 |
1981年 | 10篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1978年 | 9篇 |
1977年 | 5篇 |
1976年 | 8篇 |
1972年 | 5篇 |
1971年 | 6篇 |
1966年 | 3篇 |
排序方式: 共有786条查询结果,搜索用时 31 毫秒
31.
32.
The comparison of starch granule deformation and extent of starch gelatinization in a few common Indian unleavened flat breads (Chapati, Parontha and Poorie) was made. The starch granule swelling was evaluated by scanning electron as well as polarized light microscopy. The peak viscosity in Haake rotary viscosimeter and hydration capacity were used for comparing the extent of starch gelatinization in crust and crumb of these baked products. Although a few of the starch granules on the outside of crust, maintained a weak outline those in the crumb area gave only a matrix of gelatinized starch. The extent of starch gelatinization was reflected by the related increase in hydration capacity of these products. However, the peak viscosity values were found to be inversely related to the extent of starch gelatinization. As compared to crumb, a higher extent of browning was observed in the crust. Water absorption, type of cereal, mode and efficiency of heat transfer were found to control the extent of starch gelatinization in these baked products. 相似文献
33.
CeO2 samples doped with 10, 1.0, and 0.1 mol% Y2 O3 and undoped CeO2 samples of high purity were studied by impedance spectroscopy at temperatures <800°C and under various oxygen partial pressures. According to microstructural investigations by SEM and analytical STEM (equipped with EDXS), the grain boundaries were free of any second phase, providing direct grain-to-grain contacts. An amorphous siliceous phase was detected at only a few triple junctions, if at all; as a result, its contribution to the grain-boundary resistance was negligible. Nevertheless, the specific grain-boundary conductivities were still 2–7 orders of magnitude lower than the bulk conductivities, depending on dopant concentration, temperature, and oxygen partial pressure. The charge carrier transport across the grain boundaries occurred only through the grain-to-grain contacts, whose properties were then determined by the space-charge layer. The space-charge potential in acceptor-doped CeO2 was positive, causing the simultaneous depletion of oxygen vacancies and accumulation of electrons in the space-charge layer. The very low grain-boundary conductivities can be accounted for by the oxygen-vacancy depletion; the accumulation of electrons became evident in weakly doped and undoped CeO2 at high temperatures and under low oxygen partial pressures. 相似文献
34.
Stefan Schulz Wittko Francke Wilfried A. König Volker Schurig Kenji Mori Rolf Kittmann Dietrich Schneider 《Journal of chemical ecology》1990,16(12):3511-3521
(R)-6-Ethyl-2-methyl-2,3-dihydro-4H-pyran-4-one, (1R,3S,5R)-3-ethyl-1,8-dimethyl-2,9-dioxabicyclo[3.3. 1]non-7-ene, and (1R,3S,5R)-3-ethyl-1,8-dimethyl-2,9-dioxabicyclo[3.3.1]non-7-en-6-one represent the main components in the male pheromone of the swift moth,Hepialus hecta. The amounts of the three components were 40, 5, and 5 g per male, respectively. Structure elucidation of the compounds was based on spectroscopic data as compared to synthetic reference samples. The absolute configurations were determined by gas chromatography on chiral stationary phases; optically active samples served as reference compounds. Electrophysiological and behavioral experiments with natural material and synthetic samples clearly showed the three heterocyclic compounds to act as pheromones. (E, E)--Farnesene represents the main component of the scent secretion of maleHepialus humuli. 相似文献
35.
Günter Scharf 《Holz als Roh- und Werkstoff》1972,30(2):45-51
Zusammenfassung Die Frage des Sp?netransportes bei der Herstellung von Holzspanplatten geh?rt zu den wichtigen technischen und wirtschaftlichen
Fragen in der Spanplattenindustrie. Unter den verschiedenen F?rdersystemen gilt der Kettenf?rderer als raumsparendes und leistungsstarkes
Transportmittel. In der vorliegenden Arbeit werden die Einsatzm?glichkeiten des Kettenf?rderers innerhalb der Spanplattenproduktion
dargestellt. Für die Bemessung von Kettenf?rderern werden Angaben über den Platzbedarf in Abh?ngigkeit von F?rdervolumen gemacht.
Es werden ferner die rechnerischen M?glichkeiten zur Bestimmung der Antriebsleistung dargestellt und in vier Nomogrammen werden
Mittel an die Hand gegeben, um die Antriebsleistung von Kettenf?rderern auf graphischem Wege rasch bestimmen zu k?nnen.
Chain conveyors in particle board manufacture, their use and construction
Summary In the particle board industry, chip feeding represents one of the most important technical and economic problems during the production of particle board. Among the various conveying systems the chain conveyor is considered as a space-saving and efficient means of transportation. The operational possibilities of chain conveyors in particle board industry are discussed in this paper. For the dimensioning of chain conveyors, data on the required space in relation to the bulk to be conveyed are given. Mathematical methods for the determination of the feeding power are further depicted; by means of four nomographs it is demonstrated how the feeding power of chain conveyors may be determined graphically.相似文献
36.
37.
Tushar Borkar John Sosa Jun Yeon Hwang Thomas W. Scharf Jaimie Tiley Hamish Fraser Rajarshi Banerjee 《JOM Journal of the Minerals, Metals and Materials Society》2014,66(6):935-942
A new class of Ni-Ti-C-based metal-matrix composites has been developed using the laser-engineered net shaping? process. These composites consist of an in situ formed and homogeneously distributed titanium carbide (TiC) phase reinforcing the nickel matrix. Additionally, by tailoring the Ti/C ratio in these composites, an additional graphitic phase can also be engineered into the microstructure. Serial-sectioning, followed by three-dimensional reconstruction of the microstructure in these composites, reveals homogeneously distributed primary and eutectic titanium carbide precipitates as well as a graphitic phase encompassing the primary carbides within the nickel matrix. The morphology and spatial distribution of these phases in three dimensions reveals that the eutectic carbides form a network linked by primary carbides or graphitic nodules at the nodes, which suggests interesting insights into the sequence of phase evolution. These three-phase Ni-TiC-C composites exhibit excellent tribological properties, in terms of an extremely low coefficient of friction while maintaining a relatively high hardness. 相似文献
38.
R. Peters J. Pasel R.C. Samsun F. Scharf A. Tschauder M. Müller A. Müller M. Beer D. Stolten 《International Journal of Hydrogen Energy》2017,42(27):16946-16960
The reforming of diesel and diesel-like fuels plays a central role in the development of fuel cell systems for on-board power supplies. The vaporization of the fuel via a spray formation and the subsequent mixture with water vapor and air determine the quality of the reforming process, as is shown in this paper. By using a high quality nozzle residual hydrocarbons were below 25 ppmV during the reforming of standard diesel. Through the use of a fuel injector in pulsed operation, the load range was able to be increased from 1:1.67 to 1:6. Spray pattern analyses were conducted using a high-speed camera. The formation of the spray pattern lasted 1.5–2 ms. The testing of a fast-closing magnetic valve manufactured by GSR Ventiltechnik was carried out on the autothermal reformer (ATR) type AH2. It exist not any direct influence of the pulsed operation on hydrogen production. 相似文献
39.
Kiesel Andrea; Kunde Wilfried; Pohl Carsten; Berner Michael P.; Hoffmann Joachim 《Canadian Metallurgical Quarterly》2009,35(1):292
Expertise in a certain stimulus domain enhances perceptual capabilities. In the present article, the authors investigate whether expertise improves perceptual processing to an extent that allows complex visual stimuli to bias behavior unconsciously. Expert chess players judged whether a target chess configuration entailed a checking configuration. These displays were preceded by masked prime configurations that either represented a checking or a nonchecking configuration. Chess experts, but not novice chess players, revealed a subliminal response priming effect, that is, faster responding when prime and target displays were congruent (both checking or both nonchecking) rather than incongruent. Priming generalized to displays that were not used as targets, ruling out simple repetition priming effects. Thus, chess experts were able to judge unconsciously presented chess configurations as checking or nonchecking. A 2nd experiment demonstrated that experts' priming does not occur for simpler but uncommon chess configurations. The authors conclude that long-term practice prompts the acquisition of visual memories of chess configurations with integrated form-location conjunctions. These perceptual chunks enable complex visual processing outside of conscious awareness. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
40.
Mauricio Solano-Peralta Magda Moner-Girona Wilfried G.J.H.M. van Sark Xavier Vallv 《Renewable & Sustainable Energy Reviews》2009,13(9):2279-2294
The interest and actions towards introducing renewables for off-grid regions has increased due to their ostensible cost-effectiveness, eco-friendliness and quality services provided. Nevertheless, in many isolated areas diesel generators appear as a common option, confirming that there is a need for financial support mechanisms that aid the introduction of renewables due to their higher initial investment costs.This paper proposes a so-called ‘tropicalisation’ of the Feed-in Tariff scheme to promote the introduction of hybrid systems in isolated communities based on the idea of awarding for each kWh produced by renewable energies a premium value during a guaranteed period of time. The proposed Renewable Energy Premium Tariff (RPT) scheme is an alternative mechanism to the usual initial investment donation for off-grid energy development projects by recognising the production of renewable electricity and opting for a long-term sustainability of the projects. Ecuador presents ideal conditions to study the introduction of such a ‘tropicalised’ scheme since a Feed-in Law including off-grid projects was established in 2002 and since there are governmental and local efforts for the introduction of renewable hybrids in isolated regions.Modelling of the introduction of photovoltaics (PVs) into diesel systems for several mini-grids located in isolated regions of Ecuador has been performed, and included a detailed financial analysis for optimisation of RPT values and a comparison with existing stand-alone diesel systems. The results show the cost-effectiveness of PV/diesel hybrids over diesel gensets, taking into account present and future diesel prices. To obtain long-term sustainability of the project, the RPT values are set at 0.70–1.20$ kWh covering the operability of the whole system for 20 years, where the renewable fraction should have the largest share in the hybrid system. The proposed mechanism is expected to aid the introduction of renewable technologies to bring solutions and sustainable energy options to final users of off-grid isolated regions. 相似文献