全文获取类型
收费全文 | 646篇 |
免费 | 49篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 11篇 |
化学工业 | 128篇 |
金属工艺 | 13篇 |
机械仪表 | 19篇 |
建筑科学 | 11篇 |
能源动力 | 81篇 |
轻工业 | 165篇 |
水利工程 | 3篇 |
石油天然气 | 4篇 |
无线电 | 45篇 |
一般工业技术 | 86篇 |
冶金工业 | 11篇 |
原子能技术 | 5篇 |
自动化技术 | 115篇 |
出版年
2024年 | 2篇 |
2023年 | 20篇 |
2022年 | 29篇 |
2021年 | 55篇 |
2020年 | 27篇 |
2019年 | 36篇 |
2018年 | 35篇 |
2017年 | 48篇 |
2016年 | 32篇 |
2015年 | 20篇 |
2014年 | 26篇 |
2013年 | 68篇 |
2012年 | 43篇 |
2011年 | 50篇 |
2010年 | 31篇 |
2009年 | 49篇 |
2008年 | 42篇 |
2007年 | 21篇 |
2006年 | 22篇 |
2005年 | 6篇 |
2004年 | 8篇 |
2003年 | 6篇 |
2002年 | 5篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1995年 | 1篇 |
排序方式: 共有697条查询结果,搜索用时 203 毫秒
71.
72.
Design, synthesis and electropolymerization of a new hybrid material based on terthienyl system bearing BODIPY appendage are reported. This electrochemically polymerized unique combination readily gives an electrochromic polymer with a narrow optical band gap (1.71 eV). The electrochrome exhibits purple color when neutralized and sky blue color when oxidized in a monomer-free electrolyte solution containing 0.1 M tetrabutylammonium tetrafluoroborate dissolved in acetonitrile. Spectroscopic and electrochemical features of the electroactive polymer electrochrome indicate that it is a promising candidate for electrochromic device and display applications. 相似文献
73.
Fatih Çalışkan Zafer Tatlı Annäik Genson Stuart Hampshire 《Journal of the European Ceramic Society》2012,32(7):1337-1342
SiAlONs are silicon aluminium oxynitride ceramic materials with a range of technically important applications, from cutting tools to specialised refractories and the properties of SiAlONs can be tailored for specific purposes. In this study, different β-SiAlON compositions were prepared using fluoride (MgF2 as fluorine source plus Y2O3) and oxide (MgO plus Y2O3). These compositions were pressureless sintered under nitrogen atmosphere in the range of 1450–1750 °C for 0.5–2.5 h for comparison of densification behaviour and mechanical properties. Densities of samples were measured and analyses of result products were carried out using SEM and XRD. The F-doped sintered β-SiAlON ceramics showed better densities and less pore micrographs especially at lower temperatures compared with the fluorine free samples. Full densifications were achieved for β-SiAlON ceramics with fluoride addition at 1700 °C for 60 min. Consequently, fluorine addition to additive system has a good effect on mechanical properties and densification behaviour. 相似文献
74.
In this study, we proposed to investigate how the effect of electron-donating methyl ( CH3) group at p-position of amin ( NH2) group in aminophenol (AP) compound affected thermal stability, optical, electrochemical properties, and conductivity measurement. For this reason, we choice 2-AP and 2-amino-4-methylphenol compounds and synthesized phenolic monomers by condensation reactions 4-fluorobenzaldehyde with aromatic amino phenols. Then, these monomers were converted to their polyphenol derivatives by oxidative polycondensation reactions in an aqueous alkaline medium. Structural characterizations were carried out by FTIR, NMR, and size exclusion chromatography. Cyclic voltammetry was used to determine the electrochemical oxidation-reduction characteristics. Optical properties were investigated by UV–vis and fluorescence analyses. Solid state electrical conductivities were measured on polymer films by four-point probe technique using an electrometer. Thermal data of monomer/polymer and polymers were obtained by TG-DTA and DSC techniques, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
75.
76.
Ibrahim Sevim Fatih Hayat Yakup Kaya Nizamettin Kahraman Sadettin Şahin 《The International Journal of Advanced Manufacturing Technology》2013,66(9-12):1825-1834
In this article, Metal Inert Gas (MIG) weldability of commercially received and aged samples of 6061-T6 and 7075-T651 aluminum alloys was investigated. The welding joints were prepared in ten different combinations. Microstructure, microhardness, EDX, energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analyses were used in order to evaluate the effect of aged heat treatment on the performance of welded joints. In addition, the mechanical properties of welding joints were characterized using the tensile and microhardness tests. In conclusion, it was shown that prewelding aging heat treatment improves the mechanical properties of welding joints. 相似文献
77.
78.
Since the adoption and implementation of new technologies has an important influence on the structure and performance of the economy in both developed and developing countries, many research papers are devoted to the technology–economy nexus. Motivated by the fact that the impact of technical progress on the demand for different production factors may vary depending on the bias of the technological change, in this paper, by estimating a translog cost-share system and using state-space modeling technique, we investigate to what extent the direction of technical change is biased toward energy and away from other factors. By applying this methodology to the French economy for the period 1978–2006 the obtained results suggest that: first, technical change has a non-neutral impact on factor demands; second, capital-saving technical progress is present in the majority of the sectors studied; third, energy demand has increased in all sectors but electricity and gas. These findings may have important policy implications for environmental and energy issues in France. 相似文献
79.
Pınar Şen Fatih Dumludağ Bekir Salih Ali Rıza Özkaya Özer Bekaroğlu 《Synthetic Metals》2011,161(13-14):1245-1254
The new s-triazine-bridged trinuclear Zn(II) and Cu(II) phthalocyanines have been synthesized from the reaction of corresponding anhydrous metal salts, Zn(OAc)2 and CuCl with 4,5-bis(hexylthio)-phthalonitrile and 2,4,6-tris(2-thiophthalonitrile)-s-triazine. The tris phthalonitrile derivative of s-triazine was prepared from the reaction of 4-nitrophthalonitrile and thiocyanuric acid in dry dimethylformamide as solvent using K2CO3 as the base. The same route was applied to prepare the trinuclear Lu(III) phthalocyanine analogue. The conversion of tris phthalonitrile into its isoindoline derivative was accomplished by bubbling ammonia gas through a solution in methanol in the presence of sodium methoxide. The cyclization of two different isoindoline derivatives and 4,5-bis(hexylhthio)-1,2-diiminoisoindoline, with lutetium (III) acetate in dimethylformamide gave trinuclear Lu(III) phthalocyanine. The reaction of this complex with octakis-hexylthio phthalocyanine led to the isolation of tris double-decker Lu(III) phthalocyanine. The structures of the target compounds were confirmed by elemental analysis, UV–vis, IR and MALDI-TOF mass spectroscopies. The d.c. and a.c. conductivities of the phthalocyanine compounds were measured as a function of temperature. The small value of pre-exponential factor suggested the conduction by localized states in the band tails and by localized states near the Fermi level. The temperature dependence of the frequency exponent showed that the conduction in these compounds is due to hopping of charge carriers. The tris double-decker phthalocyanine complex showed well-defined electrochromic behaviour with green-blue and blue-purple colour transitions. 相似文献
80.
A processable rainbow mimic fluorescent polymer (PSNSF) based on 1-(9H-fluoren-2-yl)-2,5-di(thiophen-2-yl)-1H-pyrrole (SNSF) was synthesized via electrochemical polymerization in a mixture of ethanol and CH2Cl2 solution containing 0.1 M LiClO4. Characterization was carried out using cyclic voltammetry, UV-vis and FT-IR spectroscopic techniques. Also, an electrochromic device based on PSNSF was studied, which exhibits high coloration efficiency (CE), high redox stability (retaining 98.6% of its optical activity after 4000th switch) and very low response time (less than 0.5 s). 相似文献