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161.
The negative effect of fluoride ions on titanium has been known in dentistry for a long time. The presented work was aimed
at the interaction between titanium and model saliva following a short-term exposure of a specimen to a model medical preparation
rich in fluoride ions. The experimental work was carried out using titanium grade 2 in a physiological solution (pH non-adjusted,
5.8, 4.2; 5000 ppm F−) and in model saliva. Electrochemical measurement techniques were supplemented with XPS analysis. The presence of fluoride
ions resulted in partial degradation of the passive layer even in a slightly acidic environment. The decrease of pH to the
value of 4.2 and the presence of 5000 ppm F− caused titanium activation followed by a slow repassivation in model saliva. Formation of low soluble compound rich in fluorine
explains experimental data. Short medical treatment can result in relatively long period of increased titanium corrosion. 相似文献
162.
近年来,贴合纺织品面料在功能性纺织品面料中的销售增长非常迅速。为了充分发挥贴合面料的功能性,贴合用的粘合剂以及贴合工艺都是非常关键的。新材料的不断推出、创新性的设计以及对功能性越来越极端的要求,都对粘合剂和贴合工艺提出了越来越高的挑战。位于德国Detmold(德特莫尔德市)的德国Jowat(胶王股份公司)正以最先进的技术和最适合的粘合剂来迎接这一挑战。 相似文献
163.
164.
Chemical Synthesis,Sintering and Piezoelectric Properties of Ba0.85Ca0.15 Zr0.1Ti0.9O3 Lead‐Free Ceramics 下载免费PDF全文
Klara Castkova Karel Maca Jaroslav Cihlar Hana Hughes Ales Matousek Pavel Tofel Yang Bai Tim W. Button 《Journal of the American Ceramic Society》2015,98(8):2373-2380
The preparation of Ba0.85Ca0.15 Zr0.1Ti0.9O3 (BCZT) powders by wet chemical methods has been investigated, and the powders used to explore relationships between the microstructure and piezoelectric properties (d33 coefficient) of sintered BCZT ceramics. Sol–gel synthesis has been shown to be a successful method for the preparation of BCZT nanopowders with a pure tetragonal perovskite phase structure, specific surface area up to 21.8 m2/g and a mean particle size of 48 nm. These powders were suitable for the fabrication of dense BCZT ceramics with fine‐grain microstructures. The ceramics with the highest density of 95% theoretical density (TD) and grain size of 1.3 μm were prepared by uniaxial pressing followed by a two‐step sintering approach which contributed to the refinement of the BCTZ microstructure. A decrease in the grain size to 0.8–0.9 μm was achieved when samples were prepared using cold isostatic pressing. Using various sintering schedules, BCZT ceramics with broad range of grain sizes (0.8–60.5 μm) were prepared. The highest d33 = 410.8 ± 13.2 pC/N was exhibited by ceramics prepared from sol–gel powder sintered at 1425°C, with the relative density of 89.6%TD and grain size of 36 μm. 相似文献
165.
Cross-linked poly(ethylene vinyl acetate) (EVA)/low density polyethylene (LDPE)/metal hydroxides composites for wire and cable applications 总被引:1,自引:0,他引:1
Mohammed A. Bahattab Jaroslav Mosnáček Ahmed A. Basfar Tariq M. Shukri 《Polymer Bulletin》2010,64(6):569-580
Formulations of chemically cross-linked poly(ethylene vinyl acetate) (EVA) and low density polyethylene (LDPE) blends containing
metal hydroxides flame retardants such as aluminum hydroxide (ATH) and magnesium hydroxide (MH) were prepared. Comparison
of both type of metal hydroxides in respect of their influence on flammability as well as mechanical, thermal, and electrical
properties of EVA/LDPE composites is presented. Most of the investigated properties are better for composites containing MH
in comparison with composites containing ATH. Influence of various EVA/LDPE ratios on investigated properties is presented
as well. Importance of improving compatibility using compatibilizers to improve some of the investigated properties is described.
Polyethylene grafted with maleic anhydride (PEgMA) was found to be better compatibilizer for ATH than vinyl silanes. 相似文献
166.
Jaroslav Hlinka Charilaos Alexakis Jonathan G. Hardman Quazi Siddiqui Dorothee P. Auer 《Magma (New York, N.Y.)》2010,23(5-6):367-374
Object
Increases in low-frequency fluctuations (LFF, 0.01–0.1 Hz) of BOLD fMRI signal were observed during sedation and sleep. We tested the hypothesis that sedation-induced LFF increases may be mediated by increased head motion likely associated with these brain states.Materials and Methods
Twenty healthy volunteers were scanned in resting-state baseline and (15 thereof) in midazolam sedation condition. After standard preprocessing, LFF power was computed from average time series from 14 ROIs representing 5 functional networks (visual, motor, auditory, default mode, dorsal attentional). We assessed the effects of sedation on LFF and indirect effects of head motion (mean relative displacement) using mediation analysis.Results
Sedation increased LFF power with the indirect effect of motion on sedation-induced LFF significant for all networks. Global mean corrected data showed similar but weaker results: significant total effect for auditory, motor and visual; significant mediation for auditory and motor networks. Motion was strongly correlated with LFF even at baseline. Reported results were significant at p < 0.05.Conclusion
The study confirms that conscious sedation induces LFF increase, but demonstrates that this effect is mediated by increased head motion. Hence, caution in design and interpretation is recommended for studies comparing subjects or conditions differently predisposing to head motion. 相似文献167.
Zuzana Morávková Miroslava Trchová Milena Exnerová Jaroslav Stejskal 《Thin solid films》2012,520(19):6088-6094
Polyaniline films on silicon and ceramic supports were prepared in situ during the oxidative polymerization of aniline. The films were heated up to 500 °C in an inert nitrogen atmosphere. The changes in molecular structure during the carbonization have been studied by infrared spectroscopy and Raman scattering using 514, 633 and 785 nm laser excitation lines. The transformation from polyaniline salt to the base form has been detected above 100 °C. The conversion to nitrogen-containing carbon-like material followed above 200 °C. The molecular structure of the films produced during heating to 500 °C contains crosslinked phenazine-like and oxidized quinonoid units. The aniline oligomers deposited on the support in the early stages of aniline oxidation are stable during heating as it has been observed by resonance Raman scattering using 785 nm laser excitation line. The water contact angles changed after carbonization, and the films became more hydrophilic as carbonization progressed. 相似文献
168.
Kristýna Hanušová Monika ŠťastnáLenka Votavová Kamila KlaudisováJaroslav Dobiáš Michal VoldřichMiroslav Marek 《Journal of food engineering》2010
Polyethylene films coated by commercially available polyvinyldichloride (PVdC) as well as nitrocellulose (NC) lacquer with addition of natamycin preparation Delvocid® (16.7% w/w of natamycin in lacquer) were studied at 6 and 23 °C to determine the preservative migration into distilled water. The films released natamycin at maximal level 2.34 ± 0.32 mg/dm2. The diffusion coefficient of 0.79 × 10−10 ± 0.29 × 10−10 cm2/s and 1.03 × 10−10 ± 0.17 × 10−10 cm2/s was determined for natamycin transport in PVdC lacquer layer at 6 and 23 °C, respectively. For nitrocellulose lacquer the diffusion coefficient of 0.89 × 10−10 ± 0.16 × 10−10 cm2/s was found at 23 °C. The coextruded polyamide/polyethylene film coated with the PVdC lacquer containing both nisin (16.7% w/w of preparation Nisaplin®) and natamycin (see above) provided inhibitory effect against selected indicator microorganisms (Penicillium expansum, Fusarium culmorum, Lactobacillus helveticus, Listeria ivanovií). This film was unsuitable for the packaging of the surface ripened cheese Olomoucké tvar??ky. On the other hand, it was able to prevent the growth of spoilage microorganisms on the surface of the packaged soft cheese Bla?ácké zlato. 相似文献
169.
Knudsen-cell mass spectrometric measurements have been carried out in the liquid phase of the Co-Cu system in the concentration range 25.0 to 85.9 at. % Cu in the temperature range 1347 to 1587 °C. The molar excess Gibbs energy, enthalpy and entropy of mixing, as well as the thermodynamic activities of components in the liquid Co-Cu system were determined using the composition and temperature dependence of the ratio of intensities of 59Co and 63Cu ions. The results show that a subregular solution model would fit measured data well (2-parameter thermodynamically adapted power (TAP) series: C n H in J·mol−1; C 1 H =35,961, C 2 H =−5573.2; C n S in J·mol−1·K−1; C 1 S =5.54, C 2 S =−3.35). A special experiment verified solid-liquid phase equilibrium at 1327 °C and the phase diagram was calculated. 相似文献
170.
Meinam Annebushan Singh Sanjib Kr Rajbongshi Deba Kumar Sarma Ondrej Hanzel Jaroslav Sedláček Pavol Šajgalík 《Materials and Manufacturing Processes》2019,34(5):567-579
Machining of ceramic materials has been a major challenge owing to high hardness and brittleness. The reinforcement of a conducting filler allows permissible machining in electrical discharge machining (EDM) process. The current effort analyses the impact of multi-walled carbon nanotubes (MWCNT) of concentrations of 2.5 and 5 vol. %, as conducting filler towards machinability of alumina composites in µ-EDM process. The influence of tool materials and its rotation are closely analyzed. A successful machining process is observed in both the two composites, with a higher material removal rate (MRR) in 5 vol. % MWCNTs. When the tool starts to rotate at 750 rpm, an increment of around 60–65% is observed in MRR for both the two composites. Similarly, the surface roughness (Ra) decreases by a factor of 20?25%. The brass tool is observed to yield better machining capabilities due to the frequent initiation of sparks. A highly porous machined surface is observed in both the two composites. This scenario depicts the spalling effect as more dominant than melting-evaporation effect. The extent of porous recast layer on the drilled edges is found to reduce with increasing the speed of tool rotation. 相似文献