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251.
Silicon/silicon carbide (Si/SiC) core–shell nanowires grown on quartz substrates by hot-wire chemical vapor deposition were studied. Nickel was used as a catalyst to induce the growth of these core–shell nanowires followed by the vapor–solid–solid growth mechanism. The nanowires were grown by varying substrate-to-filament distance; ds-f from 1.9 to 3.1 cm with an interval of 0.4 cm. Lower ds-f produced a high density of straight core–shell nanowires. A highly crystalline single crystal Si core of the nanowires was produced at lower ds-f as well. Presence of Si and SiC nano-crystallites embedded within an amorphous matrix in the shell of the nanowires exhibited a high intensity of photoluminescence emission spectra from 600 to 1000 nm. The effects of the ds-f on the structural and optical properties of the nanowires are discussed. 相似文献
252.
The use of design-build delivery methods and building information modeling (BIM) tools in the construction industry has been growing rapidly in recent years due to the increasing demand for more efficient construction project management. The successful implementation of these?tools by engineering firms on projects, however, is still not being achieved consistently. This paper shares the experiences of the implementation of an in-house BIM tool by a large engineering, procurement, and construction firm that has an extensive reputation for design-build projects. A new workflow was proposed that takes full advantage of the BIM tool to both enhance the construction management performance and to minimize the impact on the firm’s existing workflow. The development of a new workflow was conducted by interviewing key personnel in various departments of the firm and by carefully examining probable impacts of the BIM tool’s introduction into the firm’s business processes. 相似文献
253.
Chong Cheong Yew Fatimah Abu Bakar Russly Abdul Rahman Jamilah Bakar Muhammad Zukhrufuz Zaman Selvi Velu Maryam Shariat 《Packaging Technology and Science》2014,27(3):249-254
The profile of major biogenic amines was investigated in Indian mackerel packed in modified atmosphere for up to 12 days at 5 ± 1°C. Beheaded and gutted Indian mackerel was packed under different carbon dioxide compositions to study the effects on biogenic amines formation. The treatments were control air (C), vacuum packaging (VP), 30% CO2/65% N2/5% O2 (M30C), 60% CO2/35% N2/5% O2 (M60C), 80% CO2/15% N2/5% O2 (M80C) and 100% CO2 (M100C). Each amine responded differently to different CO2 levels. After 12 days of storage, concentrations of histamine were reduced by 6.4%, 8.5%, 70.3%, 78.8% and 90.2% in fish packed under VP, M30C, M60C, M80C and M100C, respectively as compared with control air. Changes in putrescine and cadaverine showed a similar pattern. Gas mix of M30C and VP stimulated the formation of tyramine reaching 203 and 172 ppm, respectively. Higher composition of CO2 had a significant inhibitory effect on tyramine concentration (p < 0.05). There were parallel increases of putrescine and spermidine in C, VP and M30C. No significant effect of CO2 was observed on spermine (p > 0.05). After 9 days of storage, more than 300 ppm of histamine was detected in mackerel packed in VP and M30C; therefore, these atmospheres pose a histamine intoxication risk. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
254.
Monoclinic tungsten oxide (WO3) nanorods were grown using the hydrothermal method on a seeded W foil. The seed layer was formed by thermal oxidation of W foil at 400°C for 30 min. Cetyltrimethylammonium bromide (CTAB) or hexamethylamine (HMT) was used in the reactive hydrothermal bath, along with sodium tungstate dihydrate (Na2WO4.2H2O) and hydrochloric acid (HCl). The concentration of CTAB was varied from 0.01 M to 0.07 M and the concentration of HMT was varied from 0.01 M and 0.05 M. The result showed that CTAB-assisted hydrothermal reaction produced WO3 nanorods with 4–7 nm diameter, and provided that CTAB concentration was less than 0.07 M. WO3 nanorods could not be obtained when CTAB concentration was 0.07 M. Columnar structured WO3 was produced with the presence of HMT in the hydrothermal bath. This was due to decomposition of HMT to form hydroxyl ions (OH?) that inhibited the growth of nanorods. Cyclic voltammetry (CV) analysis showed better electrochromic property of WO3 nanorods compared to columnar structured WO3. 相似文献
255.
Ca2Ce2Ti5O16 dielectric ceramics prepared by conventional solid-state ceramic route was investigated. Phase composition and microwave dielectric properties were measured using XRD and Vector network analyzer, respectively. XRD analysis of the calcined and sintered samples revealed the formation of CeO2 and another unidentified phase (that vanished at ? 1400 °C) as secondary phases along with the parent Ca2Ce2Ti5O16 phase. The amount of the parent Ca2Ce2Ti5O16 phase increased with increasing sintering temperature from 1350 °C to 1450 °C accompanied by a decrease in the apparent density. The density decreased but ? r and Q u f o increased with sintering temperature. An ? r ~ 81.5, Q u f o ~ 5915 GHz and τ f ~ 219 GHz were achieved for the sample sintered at 1450 °C. 相似文献
256.
H. D. Chalak Anupam Chakrabarti Abdul Hamid Sheikh Mohd. Ashraf Iqbal 《先进材料力学与结构力学》2015,22(11):897-907
C0 finite element model based on higher order zig-zag plate theory is used to study the stability analysis of laminated sandwich plates. The in-plane displacement field is obtained by superposing a global cubically varying displacement field on a zig-zag linearly varying displacement field with different slope in each layer. The transverse displacement assumes to have a quadratic variation within the core and constant in the faces. The conditions regarding transverse shear stress at layer interfaces and top and bottom are satisfied. Numerical examples covering different features of laminated sandwich plates are presented to illustrate the accuracy of the model. 相似文献
257.
258.
Khairayu Badron Ahmad Fadzil Ismail Md Rafiqul Islam Khaizuran Abdullah Jafri Din Abdul Rahman Tharek 《International Journal of Satellite Communications and Networking》2015,33(1):57-67
Radio wave propagation plays a very important part in the design and eventually dictates performance of space communication systems. Over time, the requirements of satellite communication have grown extensively where higher capacity communications systems are needed. Escalating demands of microwave and millimetre wave communications are causing frequency spectrum congestion. Hence, existing and future satellite system operators are planning to employ frequency bands well above 10 GHz. The challenge in operating at such high frequencies for communication purposes is that there exists stronger electromagnetic interaction between the radio signals and atmospheric hydrometeors. Such instances will degrade the performance of such high frequency satellite communication systems. The development of a revised model for a better‐improved rain fade prediction of signal propagations in tropical region is considered very important. Researchers and engineers can employ the model to accurately plan the future high frequencies satellite services. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
259.
Ahmed Y. Musa Abu Bakar Mohamad Abdul Amir H. Kadhum Yousef Bashir A. Tabal 《Journal of Materials Engineering and Performance》2011,20(3):394-398
The corrosion inhibition of Al-Alloy (Al2024) in 0.5 M nitric acid solution at 30 °C was achieved using 4-4-dimethyloxazolidine-2-thione
(DMT) as a corrosion inhibitor. The electrochemical performance of the DMT was studied by electrochemical impedance spectroscopy
(EIS), potentiodynamic polarization measurements, and scanning electron microscopic study (SEM). The results indicated that
DMT acts as an inhibitor for Al2024 in 0.5 M nitric acid. Polarization curves indicated that DMT was a mixed-type inhibitor.
Inhibition efficiencies were observed to be increased with an increase in DMT concentration and attains approximately to 93.4%
at 2 mM of DMT in 0.5 M nitric acid. The adsorption of DMT model on Al2024 surface obeyed in accordance with Langmuir adsorption
isotherm model. The value of the free energy of adsorption ΔG
ads indicated that the adsorption of DMT molecule was a spontaneous process and was typical of physical and chemical adsorption. 相似文献
260.
A methodology for systematic geometric error compensation in five-axis machine tools 总被引:8,自引:8,他引:0
Abdul Wahid Khan Wuyi Chen 《The International Journal of Advanced Manufacturing Technology》2011,53(5-8):615-628
To enhance the accuracy, an efficient methodology was developed and described for systematic geometric error correction and their compensation in five-axis machine tools. The methodology is capable of compensating the overall effect of all position-dependent and position-independent errors which contribute to volumetric workspace. It was implemented on a five-axis grinding machine for error compensation and for the check of its effectiveness. Error compensation algorithm was designed, and a routine was written in Matlab software. The developed technique and software are based on an error table which interprets the function of axis through cubic spline technique and synthesis modeling of a machine tool. Recursive compensation methodology was used to remove the machine errors from the actual tool path and inverse technique was implemented to find the corrected positions of prismatic and rotary joints. Moreover, it can convert the corrected tool paths into practical compensated NC codes. The generated, corrected and modified NC codes directly fed to the controller of a five-axis machine tool. Validation of the technique was preceded by repeated experimentation of measurement and through machining of typical standard workpieces with some additional specific features. Experimental results exhibit effective compensation and remarkable improvement in the parametric and volumetric-workspace accuracy of the five-axis machine tool. 相似文献