全文获取类型
收费全文 | 752篇 |
免费 | 50篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 14篇 |
综合类 | 4篇 |
化学工业 | 194篇 |
金属工艺 | 9篇 |
机械仪表 | 12篇 |
建筑科学 | 40篇 |
矿业工程 | 2篇 |
能源动力 | 21篇 |
轻工业 | 53篇 |
水利工程 | 9篇 |
石油天然气 | 8篇 |
无线电 | 68篇 |
一般工业技术 | 182篇 |
冶金工业 | 93篇 |
原子能技术 | 7篇 |
自动化技术 | 91篇 |
出版年
2024年 | 3篇 |
2023年 | 12篇 |
2022年 | 22篇 |
2021年 | 36篇 |
2020年 | 28篇 |
2019年 | 24篇 |
2018年 | 23篇 |
2017年 | 20篇 |
2016年 | 20篇 |
2015年 | 26篇 |
2014年 | 23篇 |
2013年 | 48篇 |
2012年 | 44篇 |
2011年 | 60篇 |
2010年 | 58篇 |
2009年 | 27篇 |
2008年 | 41篇 |
2007年 | 37篇 |
2006年 | 37篇 |
2005年 | 27篇 |
2004年 | 20篇 |
2003年 | 18篇 |
2002年 | 5篇 |
2001年 | 4篇 |
2000年 | 8篇 |
1999年 | 7篇 |
1998年 | 9篇 |
1997年 | 10篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 7篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 10篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 5篇 |
1986年 | 10篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 9篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1946年 | 1篇 |
排序方式: 共有807条查询结果,搜索用时 15 毫秒
1.
Robert Groth Luke T. Cravigan Sadegh Niazi Zoran Ristovski Graham R. Johnson 《Journal of the Royal Society Interface》2021,18(178)
The airborne dynamics of respiratory droplets, and the transmission routes of pathogens embedded within them, are governed primarily by the diameter of the particles. These particles are composed of the fluid which lines the respiratory tract, and is primarily mucins and salts, which will interact with the atmosphere and evaporate to reach an equilibrium diameter. Measuring organic volume fraction (OVF) of cough aerosol has proved challenging due to large variability and low material volume produced after coughing. Here, the diametric hygroscopic growth factors (GF) of the cough aerosol produced by healthy participants were measured in situ using a rotating aerosol suspension chamber and a humidification tandem differential mobility analyser. Using hygroscopicity models, it was estimated that the average OVF in the evaporated cough aerosol was 0.88 ± 0.07 and the average GF at 90% relative humidity (RH) was 1.31 ± 0.03. To reach equilibrium in dry air the droplets will reduce in diameter by a factor of approximately 2.8 with an evaporation factor of 0.36 ± 0.05. Hysteresis was observed in cough aerosol at RH = ∼35% and RH = ∼65% for efflorescence and deliquescence, respectively, and may depend on the OVF. The same behaviour and GF were observed in nebulized bovine bronchoalveolar lavage fluid. 相似文献
2.
Yan T Wong Norbert Dommel Philip Preston Luke E Hallum Torsten Lehmann Nigel H Lovell Gregg J Suaning 《IEEE transactions on neural systems and rehabilitation engineering》2007,15(3):425-434
A neurostimulator application-specific integrated circuit (ASIC) with scalable circuitry that can stimulate 14 channels, has been developed for an epi-retinal vision prosthesis. This ASIC was designed to allow seven identical units to be connected to control up to 98 channels, with the ability to stimulate 14 electrodes simultaneously. The neurostimulator forms part of a vision prosthesis, designed to restore vision to patients who have lost their sight due to retinal diseases such as retinitis pigmentosa and macular degeneration. For charge balance, the neurostimulator was designed to stimulate with current sources and sinks operating together, and with the ability to drive a hexagonal mosaic of electrodes to reduce the electrical crosstalk that occurs when multiple bipolar stimulation sites are active simultaneously. A hexagonal mosaic of electrodes surrounds each stimulation site and has been shown to effectively isolate each site, increasing the ability to inject localized independent charge into multiple regions simultaneously. 相似文献
3.
Luke Yu 《Industry Applications, IEEE Transactions on》1995,31(2):379-383
The lattice diagram has been widely recognized and adopted to analyze the voltage surges produced at a particular location in an electrical system. These transient surges are caused by traveling waves induced by lightning strokes or switching operations. A lattice diagram can be used effectively, but the required computations are tedious. A simplified approach based on mathematical derivation is presented. The method will permit a quick evaluation of both initial and crest surge magnitudes as well as a wave shape that are all based on a given incoming surge and the surge impedances of the electrical elements involved. Sample calculations from the lattice diagram and the proposed quick evaluation are compared 相似文献
4.
Luke O'Connor 《Journal of Cryptology》1994,7(3):133-151
We analyze a very general class of algorithms for constructingm-bit invertible S-boxes called bit-by-bit methods. The method builds an S-box one entry at a time, and has been proposed by
Adams and Tavares [2] and Forre [11] to construct S-boxes that satisfy certain cryptographic properties such as nonlinearity
and the strict avalanche criterion. We prove, both theoretically and empirically, that the bit-by-bit method is infeasible
form>6.
The author is currently employed by the Distributed System Technology Center (DSTC), Brisbane, Australia. Correspondence should
be sent to ISRC, QUT Gardens Point, 2 George Street, GPO Box 2434, Brisbane, Queensland 4001, Australia. 相似文献
5.
6.
A series of novel pi (π) conjugated polymers, originating from the archetypical Polyphenylene vinylene, in which the phenyl units are successively replaced by the larger naphthyl and anthryl acene units, were previously found to have a well-defined relationship between their relative fluorescence yields and their vibrational characteristics, as determined by Raman spectroscopy. In this study the Strickler-Berg equation is used to probe the influence of continual substitution of higher order acene units into the conjugated backbone in terms of the variation of the radiative and non-radiative rates. The deconvolution of the radiative and non-radiative rates enables the correlation of the reduction of the Raman intensity and concomitant increase in the fluorescence yield with the reduction of the non-radiative rate. This confirms that the reduction of the non-radiative rate is the dominant process introduced by the vibrational confinement originating from systematic substitution of higher order acene units into the polymer backbone. 相似文献
7.
8.
The communication infrastructure of a mobile computing environment can be based on the structure of a cellular/microcellular telephone system or a PCS network. In such a system, the occurrence of handoffs cannot be avoided and when handoffs occur, wireless links held by mobile computers crossing cell boundaries may be forced to terminate. The probability that a handoff access request will result in forced termination has a significant effect on the performance of a mobile computing environment, as does the probability that an initial access request will be blocked. Although some research has been done on initial and handoff accesses in cellular/microcellular telephone systems and PCS networks, the analytical models used in this research are not appropriate for mobile computing, since unlike a telephone, a mobile computer may use several channels at once. In this paper, we develop an analytical model to study initial and handoff accesses in a mobile computing environment. The model is based on a multi-dimensional continuous time Markov chain. The accuracy of the model is verified by comparison with simulation results. We then use the model to find a practical approach to balancing the initial access blocking probability and avarage forced termination probability of a connection in a mobile computing network.This research was supported by the National Science Council, ROC, under grant NSC 85-2213-E-009-063. 相似文献
9.
Kvin Nay William J. Smiles Jacqueline Kaiser Luke M. McAloon Kim Loh Sandra Galic Jonathan S. Oakhill Andrew L. Gundlach John W. Scott 《International journal of molecular sciences》2021,22(8)
As life expectancy has increased, particularly in developed countries, due to medical advances and increased prosperity, age-related neurological diseases and mental health disorders have become more prevalent health issues, reducing the well-being and quality of life of sufferers and their families. In recent decades, due to reduced work-related levels of physical activity, and key research insights, prescribing adequate exercise has become an innovative strategy to prevent or delay the onset of these pathologies and has been demonstrated to have therapeutic benefits when used as a sole or combination treatment. Recent evidence suggests that the beneficial effects of exercise on the brain are related to several underlying mechanisms related to muscle–brain, liver–brain and gut–brain crosstalk. Therefore, this review aims to summarize the most relevant current knowledge of the impact of exercise on mood disorders and neurodegenerative diseases, and to highlight the established and potential underlying mechanisms involved in exercise–brain communication and their benefits for physiology and brain function. 相似文献
10.
A theoretical DFT study was employed to confirm the Kolbe-Schmitt reaction mechanism and investigate solvent effects on this reaction. The use of a solvent in the Kolbe-Schmitt reaction is desirable to facilitate a homogeneous reaction mixture and potentially improve the reaction rate. The candidate solvents were designed using computer aided molecular design (CAMD) and tested using DFT solvation calculations. The results from the quantum mechanical calculations were then used to determine the rate constants for each elementary step, the overall reaction yields and the corresponding residence time. The methodology was tested on the reaction without solvent, with solvents reported in the literature, and with the designed solvents. The study revealed that in the presence of solvents with high dielectric constant the reaction becomes reversible, leading to low product yields. 相似文献