全文获取类型
收费全文 | 1473篇 |
免费 | 73篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 19篇 |
综合类 | 6篇 |
化学工业 | 274篇 |
金属工艺 | 26篇 |
机械仪表 | 20篇 |
建筑科学 | 97篇 |
矿业工程 | 1篇 |
能源动力 | 74篇 |
轻工业 | 223篇 |
水利工程 | 12篇 |
石油天然气 | 4篇 |
无线电 | 68篇 |
一般工业技术 | 207篇 |
冶金工业 | 246篇 |
原子能技术 | 12篇 |
自动化技术 | 264篇 |
出版年
2023年 | 9篇 |
2022年 | 14篇 |
2021年 | 24篇 |
2020年 | 21篇 |
2019年 | 29篇 |
2018年 | 40篇 |
2017年 | 39篇 |
2016年 | 36篇 |
2015年 | 28篇 |
2014年 | 47篇 |
2013年 | 92篇 |
2012年 | 77篇 |
2011年 | 91篇 |
2010年 | 68篇 |
2009年 | 72篇 |
2008年 | 91篇 |
2007年 | 99篇 |
2006年 | 77篇 |
2005年 | 56篇 |
2004年 | 55篇 |
2003年 | 48篇 |
2002年 | 41篇 |
2001年 | 27篇 |
2000年 | 21篇 |
1999年 | 21篇 |
1998年 | 14篇 |
1997年 | 13篇 |
1996年 | 18篇 |
1995年 | 16篇 |
1994年 | 26篇 |
1993年 | 20篇 |
1992年 | 23篇 |
1991年 | 10篇 |
1990年 | 11篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 16篇 |
1986年 | 15篇 |
1985年 | 21篇 |
1984年 | 12篇 |
1983年 | 19篇 |
1982年 | 10篇 |
1981年 | 16篇 |
1980年 | 13篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1975年 | 9篇 |
1974年 | 4篇 |
排序方式: 共有1553条查询结果,搜索用时 15 毫秒
91.
92.
A number of computational models have been developed over the last 2 decades that are remarkably successful at explaining the process of translating print into sound. Nevertheless, 2 of the most successful computational accounts on the table fail to simulate the results from factorial experiments reported in this article in which university students read aloud letter strings that varied in terms of spelling–sound regularity and lexicality (regular words vs. exception words vs. nonwords) and stimulus quality (bright vs. dim). Skilled readers yielded additive effects of regularity and stimulus quality and additive effects of lexicality and stimulus quality on both RT and errors when nonwords were mixed with words. When only words appeared in the list, there was an interaction in which exception words were less affected by low stimulus quality than regular words were; no existing account anticipates or explains these results. We advance a hypothesis that assumes a novel module that accommodates these data and provide an existence proof in the form of a simulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
93.
Christopher J. Shepherd Gareth J. Appleby-Thomas James M. Wilgeroth Paul J. Hazell Derek F. Allsop 《International Journal of Impact Engineering》2011,38(12):981-988
The effects of projectile penetration into soft tissue are often studied using the tissue simulant ballistic soap. Consequently, a full understanding of the high strain-rate response of ballistic soap is desirable. Using the plate-impact technique, key shock parameters have been measured for impacts in the range 81–968 m/s, allowing derivation of the Hugoniot equation-of-state for soap in the US–uP and σX–uP planes. A polynomial Hugoniot relationship was found in the US–uP plane, with the general form US = 1.96 + 2.41uP − 0.72uP2 (ρ0 = 1.107 g/cc). Further, embedded lateral manganin stress gauges were employed to interrogate the evolution of lateral stress within the soap. A gradient in lateral stress, whose magnitude increased incrementally with impact stress, was apparent behind the shock for σX >1 GPa. It is proposed that at higher values of σX, increased compression of hydrocarbon chains acts to increase the materials resistance to shear, a phenomenon consistent with steric hindrance. 相似文献
94.
Julie Brown Derek Wainohu Basuki Suratno Lynne E. Bilston 《Accident; analysis and prevention》2010,42(1):112-121
Accessory child safety harnesses are available in some countries as alternative restraints for young children or as an accessory restraint used with booster seats. Their use, in Australia at least, is becoming more common. There have been concerns that the risk of misuse of these restraints outweighs any potential benefit this system might have over a retractable lap-shoulder belt system used with a booster seat. However to date there is no evidence to confirm or deny this. This study used laboratory simulated frontal crash tests to examine the performance of accessory child safety harness systems compared to the lap-shoulder belt when used alone and when used with two common designs of Australian booster seat. The performance of the child safety harness system when misused was also investigated. The results demonstrate that the correctly used child safety harness system performed no better than the lap-shoulder system, and in fact allows for a greater risk of submarining. Furthermore, one common form of child safety harness misuse, where the harness is over-tightened causing the lap belt to be positioned high over the abdomen, allowed extremely undesirable dummy motion. This involved gross submarining and direct contact between the harness system and the dummy's neck. These findings suggest that the risks associated with accessory child safety harness systems most likely outweigh any potential benefits, in frontal impacts at least. 相似文献
95.
T. Derek J. Clements‐Croome 《Building Research & Information》2013,41(2):86-96
The paper brings together many current themes of interest and stimulates the reader to be aware that in creative work there has to be something beyond technical competence; there has to be a committed energy, desire and love in the work being created. The author confirms that buildings modify climate; they influence behaviour and culture; they affect the distribution of resources and the ecological pattern of our planet, whilst human aspirations can only be met when climate, buildings and people are in balance. 相似文献
96.
Kenjiro Iida Mark R. Stolzenburg Peter H. McMurry James N. Smith Frederick R. Quant Derek R. Oberreit 《Aerosol science and technology》2013,47(10):862-871
An ultrafine, water-based condensation particle counter (U-WCPC, TSI Model 3786) has been compared to a butanol-based ultrafine counter (U-BCPC, TSI Model 3025) for measurement of atmospheric and freeway-tunnel aerosols. The U-WCPC utilizes a warm, wet-walled growth tube to activate and grow particles through water condensation in a laminar-flow. It has an aerosol sampling rate of 0.3 L/min, and a nominal detection limit near 3 nm. Several field comparisons were made to the butanol-based instrument with the same nominal detection limit. For measurements of size-selected aerosols with diameters of 5 nm and larger the two instruments generally agreed, with a mean response within 5%. At 3 nm particle size differences were observed, and these differences varied with the data set. Measurements of ambient aerosol in Boulder, Colorado showed higher counting efficiency at 3 nm with the U-BCPC, while in a California freeway tunnel the opposite trend was observed, with higher counting efficiencies at 3 nm observed by the U-WCPC. For direct measurement of atmospheric aerosols, the two types of instruments yielded equivalent concentrations, independent of particle number concentration. 相似文献
97.
Yasemin Vural Derek B. Ingham Mohamed Pourkashanian 《International Journal of Hydrogen Energy》2009,34(22):9181-9187
In this study, the performance (current–voltage curve) prediction of a Proton Exchange Membrane Fuel Cell (PEMFC) is performed for different operational conditions using an Adaptive Neuro-Fuzzy Inference System (ANFIS). First, ANFIS is trained with a set of input and output data. The trained model is then tested with an independent set of experimental data. The trained and tested model is then used to predict the performance curve of the PEMFC under various operational conditions. The model shows very good agreement with the experimental data and this indicates that ANFIS is capable of predicting fuel cell performance (in terms of cell voltage) with a high accuracy in an easy, rapid and cost effective way for the case presented. Finally, the capabilities and the limitations of the model for the application in fuel cells have been discussed. 相似文献
98.
A 7.5-250-hp range of variable-frequency ac motor drives has been under development at the Westinghouse R & D Center since early in 1981. Design and performance details for prototype equipment rated for 10, 20, and 50 hp will be discussed. The drive system comprises a three-phase thyristor controlled ac/dc converter in conjunction with a dc/ac adjustable-frequency inverter using gate turn-off thyristors (GTO's). The output of the inverter is a six-step voltage wave in the range of 6-120 Hz, suitable for driving three-phase ac induction or synchronous motors. Details of the inverter design, including means to protect the gate turn-off thyristors from output line-to-line or line-to-ground short circuits, will be given special attention. 相似文献
99.
The physiology of flatfish chromatophores 总被引:3,自引:0,他引:3
Burton D 《Microscopy research and technique》2002,58(6):481-487
Most flatfish, of the order Pleuronectiformes, possess a white lower side, and a brown or grey upper side. This upper side can display integumentary patterning with dark areas and colored or white spots. Chromatophores in flatfish are dermal and epidermal melanophores, as well as dermal xanthophores, erythrophores, iridophores, and leucophores, combinations of which contribute to the color and patterning. Cellular studies demonstrate pattern-related differences in numerical distribution between the types of chromatophores, and in their size, both of which will enhance contrast between areas of the pattern. As well as these morphological characteristics, there are also clear physiological differences, with melanophores from various areas of the patterns demonstrating differential responsiveness to background and to stress/excitement stimuli. Regulation of flatfish melanophore responses is predominantly neural, through the sympathetic nervous system; the pituitary hormones in these fish function in maintaining final equilibria in physiological adaptations to backgrounds. Melanophores from main components of patterns also respond differently in vitro to electrical stimulation, to pituitary hormones, and to sympathomimetic drugs and their antagonists. Sensitivity characteristics with alpha- and beta-adrenergic pharmacological reagents in vitro indicate the existence of a pattern-related balance in alpha- and beta-adrenoceptor mediation in melanophore regulation. The patterning mechanism is complex, with both morphological and physiological differences at the chromatophore level, as well as involvement of central processing and control, which remains to be analysed. 相似文献
100.
In this work, the fluid flow and mass transfer due to the presence of an electric field in a rectangular channel is examined. We consider a mixture of water or another neutral solvent and a salt compound, such as sodium chloride, for which the ionic species are entirely dissociated. Results are produced for the case in which the channel height is much greater than the electric double layer (EDL) (microchannel) and for the case in which the channel height is of the order of the width of the EDL (nanochannel). Both symmetric and nonsymmetric velocity, potential, and mole fraction distributions are considered, unlike previous work on this problem. At small electrolyte concentrations, the Debeye-Huckel picture of the electric double layer is recovered; at larger concentrations, the Gouy-Chapman picture of the electric double emerges naturally. The numerical results presented here agree with analytical solutions of a singular perturbation analysis, which is valid as the channel height increases. In the symmetric case for the electroosmotic flow so induced, the velocity field and the potential are similar. In the asymmetric case corresponding to different wall potentials, the velocity and potential can be vastly different. The fluid is assumed to behave as a continuum, and the volume flow rate is observed to vary linearly with channel height for electrically driven flow, in contrast to pressure-driven flow, which varies as height cubed. This means that very large pressure drops are required to drive flows in small channels. However, useful volume flow rates may be obtained at a very low driving voltage. 相似文献