全文获取类型
收费全文 | 598篇 |
免费 | 47篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 8篇 |
化学工业 | 144篇 |
金属工艺 | 31篇 |
机械仪表 | 31篇 |
建筑科学 | 19篇 |
矿业工程 | 3篇 |
能源动力 | 19篇 |
轻工业 | 122篇 |
水利工程 | 1篇 |
石油天然气 | 3篇 |
无线电 | 23篇 |
一般工业技术 | 136篇 |
冶金工业 | 6篇 |
原子能技术 | 5篇 |
自动化技术 | 98篇 |
出版年
2023年 | 4篇 |
2022年 | 4篇 |
2021年 | 17篇 |
2020年 | 14篇 |
2019年 | 15篇 |
2018年 | 26篇 |
2017年 | 13篇 |
2016年 | 25篇 |
2015年 | 26篇 |
2014年 | 43篇 |
2013年 | 109篇 |
2012年 | 37篇 |
2011年 | 28篇 |
2010年 | 53篇 |
2009年 | 43篇 |
2008年 | 34篇 |
2007年 | 17篇 |
2006年 | 8篇 |
2005年 | 4篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 5篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 7篇 |
1997年 | 5篇 |
1996年 | 9篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 5篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 8篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1970年 | 2篇 |
1962年 | 2篇 |
1961年 | 3篇 |
1957年 | 2篇 |
排序方式: 共有649条查询结果,搜索用时 15 毫秒
131.
132.
We present first principles calculations of the electronic structure, enthalpies of formation and electric field gradients in C15 HfV2Hx (x = 1, 2, 3, 4). In C15 Laves phases, hydrogen can occupy three possible interstitial positions: 96g, 32e, and 8b. To determine which one of these interstitials is the most favorable for storing hydrogen, enthalpies of formation were calculated for every site, with different concentrations of hydrogen. In order to investigate the change in electronic structure before and after hydrogenation, we calculated the electric field gradients induced by hydrogen on the vanadium, and compared them with the existing nuclear magnetic resonance measurements. This comparison enabled us to study the distribution of hydrogen atoms in the crystal lattice, as well as the occupation of possible interstitials. 相似文献
133.
The heat distribution during thermal modification of beech (Fagus sylvatica L.) and spruce (Picea abies L. Karst) wood with dimensions of 80 × 80 × 200 mm3 has been investigated. Heat distribution was continuously measured by thermocouples in longitudinal and transverse directions. Significant temperature gradients occur in the initial phase of the process as well as during the modification phase (set temperature 200 °C for 3 h), where ongoing chemical reactions in wood were taking place. Thus, the temperature in the investigated positions increased to 240 °C (beech) and 215 °C (spruce). The mentioned properties should be taken into account when optimizing the heat treatment process (quality control, energy savings, etc.). 相似文献
134.
PETR VIŠČOR A. DELONG M. DRŠTIČKA K. HLADIL V. KOLAŘÍK F. OLSEN 《International Journal of Electronics》2013,100(5):869-872
A new analysis of the electrical response of a macroscopic solid state system to an arbitrary electrical voltage input is presented. The results indicate that with a small, sinusoidal voltage input within the classical frequency range (ω < 1010Hz), the electrical response in spatially homogeneous systems mirrors first of all the static, spatial distribution of the mobile charge carrier density through the local electrical conductivity relaxation time. This enables any system, inclusive interface and electrical contact regions to be modelled by a simple, passive R, C electrical network, where each of the network elements has a very direct physical meaning. Ultra pure, single crystal silicon, pure polycrystalline silicon and Al-Al2O3-Au metal-insulator-metal (MIM) structure are used as illustrative examples. 相似文献
135.
Eliška Leitmannová Jan Svoboda Jan Sedláček Jiří Vohlídal Petr Kačer Libor Červený 《Applied Catalysis A: General》2010,372(1):34-39
Hydrogenation of phenylacetylene (PA) and 3-phenylpropyne (PP) was carried out using [Rh(diene)Cl]2 complexes (diene is hexadiene (HD), cycloocta-1,5-diene (COD), norborna-2,5-diene (NBD)) in their immobilized forms and compared with hydrogenation in homogeneous arrangement. Immobilization brings significant increase of the catalytic activity and product selectivity in the step-wise hydrogenation to corresponding vinyl-resp. allyl-benzenes. Diene-ligand effect was apparent in PA hydrogenation; the product selectivity decreased in order Rh(HD) > Rh(NBD) > Rh(COD) and catalytic activity decreased in order Rh(HD) > Rh(COD) > Rh(NBD). 相似文献
136.
Willi Pabst Eva Gregorová Martin Černý 《Journal of the European Ceramic Society》2013,33(15-16):3085-3093
The elastic moduli (Young's moduli) of alumina and zirconia ceramics with porosities ranging from almost dense (2–3%) to highly porous (46–52%), the latter prepared with starch as a pore-forming agent, have been measured via impulse excitation and four-point bending tests from room temperature up to more than 1200 °C. It is shown that, independent of the temperature and the material, the porosity dependence of the Young's modulus is well predicted by our exponential relation and that, irrespective of porosity, the temperature dependence follows a master curve that is characteristic of the material (for alumina exhibiting a decrease with a gradually growing tangent slope and for zirconia exhibiting a steep decrease with an inflection point at moderately elevated temperatures below 400 °C). Differences between isothermal (static) and adiabatic (dynamic) values are negligible as long as the materials are purely elastic (i.e. at temperatures below approximately 1000 °C). 相似文献
137.
Ivan Holoubek Josef Čáslavsky Pavel Kořínek Klára Štaffová Jiří Kohoutek AleŠ Hrdlička 《Polycyclic Aromatic Compounds》2013,33(1-4):159-167
Abstract Concentrations of polyaromatic hydrocarbons (PAHs), chlorinated pesticides, polychlorinated biphenyls, dibenzo-p-dioxins and dibenzo-p-furans (PCDDs/Fs) in ambient air in Ko?etice, a background locality in the South Bohemia, have been estimated in the period from July to December 1994. The 24-hours samples have been taken by the means of a high-volume sampler. Sample analysis involved Soxhlet extraction of polyurethane foam, extract preconcentration and chromatographic clean-up procedure followed by HPLC determination of PAHs with fluorescence detection, GC/ECD determination of chlorinated pollutants, and GC/MS determination of PCDDs/Fs. The results of this first detailed study undertaken in Czech Republic are compared with the data obtained by similar projects in industrial and/or urban areas in the Czech Republic and in rural or urban areas in other European countries. 相似文献
138.
Petr Čermák Miroslav Trcala 《International Journal of Heat and Mass Transfer》2012,55(25-26):7709-7717
The paper presents an experimental measurement of diffusion coefficients of wood and theoretical analysis (stochastic analysis) based on influence of uncertainty in these coefficients on moisture field during wood drying simulations. Experimental measurement was used to verify of analytic equations for calculation of diffusion coefficients, which were implemented in the numerical simulations. Histograms show on normal distribution, but stochastic analysis was used for uniform distribution as well. Mean value of diffusion coefficient in tangential direction was calculated as 1.016·10?10 m2 s?1 and standard deviation as 0.153·10?10 m2 s?1. Stochastic analysis is based on the Monte Carlo method. The analysis proves that final moisture field has a same probability distribution as the diffusion coefficient (normal or uniform distribution) and also depicts a character of course and distribution of uncertainty in lumber during drying. 相似文献
139.
An innovative interior thermal insulation system on the basis of hydrophilic mineral wool which can serve as an alternative solution to the commonly used systems with water vapor barrier is presented in the paper. At first, the process of materials design is described. Then, the hygrothermal performance of the designed insulation system is tested in the difference climate conditions that correspond to the winter climate in Middle Europe. In the experiment, the profiles of temperature, relative humidity and liquid moisture content are monitored. Measured temperature profiles demonstrate the proper thermal insulation function of the system. The hygric function can also be considered very good as no water condensation during the whole testing period of five months appears in the insulation layer. Therefore, the basic requirements for the successful application of the system in building practice are met. 相似文献
140.
R. Blaauwgeers M. Blazkova M. Človečko V. B. Eltsov R. de Graaf J. Hosio M. Krusius D. Schmoranzer W. Schoepe L. Skrbek P. Skyba R. E. Solntsev D. E. Zmeev 《Journal of Low Temperature Physics》2007,146(5-6):537-562
Commercial quartz oscillators of the tuning-fork type with a resonant frequency of ∼ 32 kHz have been investigated in helium
liquids. The oscillators are found to have at best Q values in the range 105–106, when measured in vacuum below 1.5 K. However, the variability is large and for very low temperature operation the sensor
has to be preselected. We explore their properties in the regime of linear viscous hydrodynamic response in normal and superfluid
3He and 4He, by comparing measurements to the hydrodynamic model of the sensor.
Dedicated to former JLTP editor Frank Pobell. 相似文献