全文获取类型
收费全文 | 254篇 |
免费 | 9篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 89篇 |
机械仪表 | 5篇 |
建筑科学 | 8篇 |
矿业工程 | 1篇 |
能源动力 | 12篇 |
轻工业 | 41篇 |
水利工程 | 2篇 |
石油天然气 | 3篇 |
无线电 | 8篇 |
一般工业技术 | 44篇 |
冶金工业 | 8篇 |
原子能技术 | 1篇 |
自动化技术 | 39篇 |
出版年
2023年 | 3篇 |
2022年 | 27篇 |
2021年 | 21篇 |
2020年 | 8篇 |
2019年 | 10篇 |
2018年 | 7篇 |
2017年 | 7篇 |
2016年 | 8篇 |
2015年 | 6篇 |
2014年 | 14篇 |
2013年 | 12篇 |
2012年 | 18篇 |
2011年 | 28篇 |
2010年 | 22篇 |
2009年 | 13篇 |
2008年 | 13篇 |
2007年 | 6篇 |
2006年 | 10篇 |
2005年 | 9篇 |
2004年 | 2篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1989年 | 1篇 |
排序方式: 共有263条查询结果,搜索用时 0 毫秒
21.
22.
Katerina Raleva Dragica Vasileska Stephen M. Goodnick Tomislav Dzekov 《Journal of Computational Electronics》2008,7(3):226-230
For the purpose of investigating the role of self-heating effects on the electrical characteristics of nano-scale devices,
we implemented a two-dimensional Monte Carlo device simulator that self-consistently includes the solution of the energy balance
equations for both, acoustic and optical phonons. We find less degradation in the current in smaller device structures because
of the more pronounced velocity overshoot. 相似文献
23.
Viktor Dan’ko Katerina Michailovska Ivan Indutnyi Petro Shepeliavyi 《Nanoscale research letters》2014,9(1):165
We investigated plasmon-assisted enhancement of emission from silicon nanoparticles (ncs-Si) embedded into porous SiO
x
matrix in the 500- to 820-nm wavelength range. In the presence in the near-surface region of gold nanoisland film, ncs-Si exhibited up to twofold luminescence enhancement at emission frequencies that correspond to the plasmon resonance frequency of Au nanoparticles. Enhancement of the photoluminescence (PL) intensity was attributed to coupling with the localized surface plasmons (LSPs) excited in Au nanoparticles and to increase in the radiative decay rate of ncs-Si. It has been shown that spontaneous emission decay rate of ncs-Si modified by thin Au film over the wide emission spectral range was accelerated. The emission decay rate distribution was determined by fitting the experimental decay curves to the stretched exponential model. The observed increase of the PL decay rate distribution width for the Au-coated nc-Si-SiO
x
sample in comparison with the uncoated one was explained by fluctuations in the surface-plasmon excitation rate.
PACS
78. 67. Bf; 78.55.-m 相似文献24.
We report on experimental results of the thermal conductivity k of
highly porous Si in the temperature range 4.2 to 20 K, obtained using the
direct current (dc) method combined with thermal finite element simulations. The
reported results are the first in the literature for this temperature range. It
was found that porous Si thermal conductivity at these temperatures shows a
plateau-like temperature dependence similar to that obtained in glasses, with a
constant k value as low as 0.04 W/m.K. This behavior is attributed
to the presence of a majority of non-propagating vibrational modes, resulting
from the nanoscale fractal structure of the material. By examining the fractal
geometry of porous Si and its fractal dimensionality, which was smaller than two
for the specific porous Si material used, we propose that a band of fractons
(the localized vibrational excitations of a fractal lattice) is responsible for
the observed plateau. The above results complement previous results by the
authors in the temperature range 20 to 350 K. In this temperature range, a
monotonic increase of k with temperature is observed, fitted with
simplified classical models. The extremely low thermal conductivity of porous
Si, especially at cryogenic temperatures, makes this material an excellent
substrate for Si-integrated microcooling devices (micro-coldplate).
PACS
61.43.-j; 63.22.-m; 65.8.-g 相似文献25.
Being aware of negative health effects of radon exposure, many countries aim for the reduction of the radon exposure of their population. The Czech radon programme was commenced >20 y ago. Since then experts have gathered a lot of knowledge, necessary legislation has been enacted, tens of thousands of inhabitants have been offered free measurement and subsidy for the mitigation. Despite the effort, the effectiveness of the radon programme seems to be poor. Newly built houses still exhibit elevated radon concentrations and the number of houses mitigated is very low. Is it possible to enhance the effectivity of radon programme while keeping it on a voluntary basis? One possible way is to employ health marketing that draws together traditional marketing theories and science-based strategies to prevention. The potential of using marketing principles in communication and delivery of radon information will be discussed. 相似文献
26.
The mechanical and morphological degradation that human dentin undergoes after prolonged exposure in cola drinks was examined using nanoindentation and AFM. The elastic modulus of the dentin prior cola exposure was 18.28 ± 1.7 GPa, while after exposure it had decreased to 4.25 ± 1.4 GPa on the surface that was in direct contact with the drink, and to 13.38 ± 2.9 GPa on the surface that was in indirect contact with the drink. AFM documented the corrosion effects of the cola through topography images and histograms of the RMS roughness. 相似文献
27.
Klánová J Diamond M Jones K Lammel G Lohmann R Pirrone N Scheringer M Balducci C Bidleman T Bláha K Bláha L Booij K Bouwman H Breivik K Eckhardt S Fiedler H Garrigues P Harner T Holoubek I Hung H MacLeod M Magulova K Mosca S Pistocchi A Simonich S Smedes F Stephanou E Sweetman A Sebková K Venier M Vighi M Vrana B Wania F Weber R Weiss P 《Environmental science & technology》2011,45(18):7617-7619
28.
29.
Combination of analyte protectants to overcome matrix effects in routine GC analysis of pesticide residues in food matrixes 总被引:3,自引:0,他引:3
Analyte protectants were previously defined as compounds that strongly interact with active sites in the gas chromatographic (GC) system, thus decreasing degradation, adsorption, or both of coinjected analytes. In this study, we evaluated various combinations of promising analyte protectants for the volatility range of GC-amenable pesticides using GC/quadrupole mass spectrometry (MS) and 1-microL hot splitless injection for sample introduction. A mixture of ethylglycerol, gulonolactone, and sorbitol (at 10, 1, and 1 mg/mL, respectively, in the injected samples) was found to be the most effective in minimizing losses of susceptible analytes and significantly improving their peak shapes (due to reduction of peak tailing). When added to final sample extracts and matrix-free calibration standards alike, these analyte protectants induced a similar response enhancement in both instances, resulting in effective equalization of the matrix-induced response enhancement effect even after a large number of fruit and vegetable extract injections. As compared to matrix-matched standardization, the analyte protectant approach offers a more convenient solution to the problems associated with calibration in routine GC/MS analysis of pesticide residues and possibly other susceptible analyte types in diverse samples. Moreover, the use of analyte protectants also substantially reduced another adverse matrix-related effect caused by gradual build-up of nonvolatile matrix components in the GC system, thus improving ruggedness and, consequently, reducing need for frequent maintenance. 相似文献
30.
Complex chemical processes called nonenzymatic glycation and glycoxidation are one of the interesting examples of potentially harmful interaction between nutrition and disease. This review summarizes factors influencing the extent of glycoxidation in health and disease and especially focuses on the role of genetic variability in "glycoxidation-related genes" in a disease and diet-related pathogenesis. Possible interaction between genetic variability in relevant loci and dietary advanced glycation end products (AGEs) is considered. As AGEs possess a wide range of chemical and biological effects, the interindividual functional variability in systems dealing with glycoxidation could have a significant nutrigenomic and nutrigenetic consequences. 相似文献