全文获取类型
收费全文 | 15635篇 |
免费 | 1180篇 |
国内免费 | 523篇 |
专业分类
电工技术 | 269篇 |
综合类 | 661篇 |
化学工业 | 6196篇 |
金属工艺 | 1366篇 |
机械仪表 | 373篇 |
建筑科学 | 472篇 |
矿业工程 | 319篇 |
能源动力 | 1125篇 |
轻工业 | 1266篇 |
水利工程 | 29篇 |
石油天然气 | 951篇 |
武器工业 | 33篇 |
无线电 | 410篇 |
一般工业技术 | 2757篇 |
冶金工业 | 700篇 |
原子能技术 | 266篇 |
自动化技术 | 145篇 |
出版年
2024年 | 19篇 |
2023年 | 205篇 |
2022年 | 338篇 |
2021年 | 489篇 |
2020年 | 488篇 |
2019年 | 401篇 |
2018年 | 374篇 |
2017年 | 447篇 |
2016年 | 393篇 |
2015年 | 444篇 |
2014年 | 832篇 |
2013年 | 1033篇 |
2012年 | 968篇 |
2011年 | 1366篇 |
2010年 | 1004篇 |
2009年 | 1042篇 |
2008年 | 832篇 |
2007年 | 1047篇 |
2006年 | 958篇 |
2005年 | 737篇 |
2004年 | 679篇 |
2003年 | 612篇 |
2002年 | 440篇 |
2001年 | 353篇 |
2000年 | 292篇 |
1999年 | 258篇 |
1998年 | 235篇 |
1997年 | 167篇 |
1996年 | 160篇 |
1995年 | 146篇 |
1994年 | 110篇 |
1993年 | 86篇 |
1992年 | 63篇 |
1991年 | 55篇 |
1990年 | 49篇 |
1989年 | 36篇 |
1988年 | 24篇 |
1987年 | 24篇 |
1986年 | 20篇 |
1985年 | 19篇 |
1984年 | 18篇 |
1983年 | 15篇 |
1982年 | 11篇 |
1981年 | 14篇 |
1980年 | 10篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1959年 | 4篇 |
1951年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(95):40407-40414
The present work addresses the potentialities of Pt–Ru nanoparticles deposited on a graphene oxide (RGO) and TiO2 composite support towards electrochemical oxidation of ethanol in acidic media relevant for fuel cell applications. To immobilize platinum–ruthenium bimetallic nanoparticles on to an RGO-TiO2 nanohybrid support a simple solution-phase chemical reduction method is utilized. An examination using electron microscopy and energy dispersive X-ray spectroscopy (EDS) indicated that Pt–Ru particles of 4–8 nm in diameter are dispersed on RGO-TiO2 composite support. The corresponding Pt–Ru/RGO-TiO2 nanocomposite electrocatalyst was studied for the electrochemical oxidation of ethanol in acidic media. Compared to the commercial Pt–Ru/C and Pt/C catalysts, Pt–Ru/RGO-TiO2 nanocomposite yields higher mass-specific activity of about 1.4 and 3.2 times, respectively towards ethanol oxidation reaction (EOR). The synergistic boosting provided by RGO-TiO2 composite support and Pt–Ru ensemble together contributed to the observed higher EOR activity and stability to Pt–Ru/RGO-TiO2 nanocomposite compared with other in-house synthesized Pt–Ru/RGO, Pt/RGO and commercial Pt–Ru/C and Pt/C electrocatalysts. Further optimization of RGO-TiO2 composite support provides opportunity to deposit many other types of metallic nanoparticles onto it for fuel cell electrocatalysis applications. 相似文献
2.
《Advanced Powder Technology》2022,33(2):103404
Here we report the synthesis of 1D TiO2 sub 10 nm nanowires through one pot hydrothermal method in an alkaline NaOH medium at 95 °C for 36 h. Further, these TiO2 nanowires were embellished with silver (Ag) using polyvinylpyrrolidone (PVP) and ethylene glycol (EG) based solvothermal route at 160 °C for 4 h. With Ag decoration the photocatalytic activity was enhanced and the complete photooxidation of Methylene Blue (MB) was achieved in 35 min under optimized conditions. Super- and ultra-hydrophobic coating on cotton fabric exhibited a consistent antibacterial activity with enhanced UV-blocking property. Enhanced multifunctional properties observed were primarily attributed to the formation of Ag decorated 1D sub 10 nm TiO2 nanowires heterojunctions achieved using facile chemical route. Hence, such multiple functionalities make the 1D sub 10 nm TiO2 nanowires good candidate for industrial and domestic wastewater treatment. 相似文献
3.
《Ceramics International》2022,48(5):6322-6337
To optimize the corrosion, bioactivity, and biocompatibility behaviors of plasma electrolytic oxidation (PEO) coatings on titanium substrates, the effects of five process variables including frequency, current density, duty cycle, treatment time, and electrolyte Ca/P ratio were evaluated. In our systematic study, a Taguchi design of experimental based on an L16 orthogonal array was used. For this, the coatings characteristics such as the surface roughness, wettability, rutile to anatase and Ca/P ratios, and corrosion polarization resistance were investigated. After determining the optimum process variables for each response, the apatite forming ability in SBF (bioactivity behavior) and MG63 cell attachment and flattening (biocompatibility behavior) for two groups of coatings were examined. The first group was optimized based on the maximum corrosion polarization resistance and the variables were set as the frequency of 2000 Hz, the current density of 5 A/dm2, the duty cycle of 30%, the treatment time of 5 min, and the Ca/P ratio of 0.65 at. % in the electrolyte. For the second group, the maximum surface roughness, greatest Ca/P ratio, and highest wettability as well as the minimum rutile to anatase ratio in coatings, could be obtained when the variables were set as the frequency of 10 Hz, the current density of 12.5 A/dm2, the duty cycle of 50%, the treatment time of 12.5 min, and the Ca/P ratio of 1.70 at. % in the electrolyte. The results showed that while both groups of coatings indicated a significant apatite forming ability and can serve as bioactive coatings, a proper attachment and flattening of cells and consequently, the favorable biocompatibility properties were seen only in the first group. 相似文献
4.
Lindsey Yue Alicia Bayon Wojciech Lipiński 《American Institute of Chemical Engineers》2021,67(8):e17267
The effects of particle size and carbon dioxide concentration on chemical conversion in engineered spherical particles undergoing calcium oxide looping are investigated. Particles are thermochemically cycled in a furnace under different carbon dioxide concentrations. Changes in composition due to chemical reactions are measured using thermogravimetric analysis. Gas composition at the furnace exit is evaluated with mass spectroscopy. A numerical model of thermal transport phenomena developed previously is adapted to match the physical system investigated in the present study. The model is used to elucidate effects of reacting medium characteristics on particle temperature and reaction extent. Experimental and numerical results show that (1) an increase in particle size results in a decrease in carbonation extent, and (2) the carbonation step consists of fast and slow reaction regimes. The reaction rates in the fast and slow carbonation regimes increase with increasing carbon dioxide concentration. The effect of carbon dioxide concentration and the distinction between the fast and slow regimes become more pronounced with increasing particle size. 相似文献
5.
《Ceramics International》2022,48(16):22906-22916
Solid-state reaction of α-Ti(HPO4)2·H2O (α-TiP) and acetates of Co, Ni, or Cu at 500 °C and 800 °C produce a number of different metal titanium phosphate (MTiP) inorganic pigments with different colors and shades. At a given metal to α-TiP ratio and calcination temperature, the reaction produces several types of pigments such as phosphates M0.5TiO(PO4), M0.5Ti2(PO4)3, M2P2O7, and M3(PO4)3 (M = Co, Ni, and Cu) with a unique color. α-TiP, an iron free base material was prepared by digestion of high-grade natural ilmenite beach sand (FeTiO3) with 85 wt% H3PO4 at 120 °C. TGA, XRD, SEM/EDX, Diffuse reflectance UV–vis, and Raman spectroscopy techniques were used for characterization. Synthesized MTiP pigments after enameling at a single fire glazing at 1100 °C for 45 min exhibit vivid colors, ranging from purple, yellow, and green with different shades. 相似文献
6.
7.
Ashkan Farazin Saeid Sahmani Maryam Soleimani Amin Kolooshani Saeed Saber-Samandari Amirsalar Khandan 《Ceramics International》2021,47(13):18339-18350
Porous bony scaffolds are utilized to manage the growth and migration of cells from adjacent tissues to a defective position. In the current investigation, the effect of titanium oxide (TiO2) nanoparticles on mechanical and physical properties of porous bony implants made of polymeric polycaprolactone (PCL) is studied. The bio-nanocomposite scaffolds are prepared with composition of nanocrystalline hydroxyapatite (HA) and TiO2 powder using the freeze-drying technique for different weight fractions of TiO2 (0 wt%, 5 wt%, 10 wt%, and 15 wt%). In order to identify the microstructure and morphology of the fabricated porous bio-nanocomposites, the X-ray diffraction (XRD), atomic force microscope (AFM) and scanning electron microscopy (SEM) are employed. Also, the biocompatibility and biodegradability of the manufactured scaffolds are examined by placing them in a simulated body fluid (SBF) for 21 days, their weight and pH changes are measured. The rate of degradation of the PCL-HA scaffold can be controlled by varying the percentage of its constituent components. Due to an increasing growth and activity of bone cells and the apatite formation on the free surface of the fabricated bio-nanocomposite implants as well as their reasonable mechanical properties, they have the potential to be used as a bone substitute. Additionally, with the aid of the experimentally extracted mechanical properties of the scaffolds, the vibrational characteristics of a beam-type implant made of the proposed porous bio-nanocomposites are explored. The results obtained from SEM image indicate that the scaffolds produced by the employed method have high total porosity (70%–85%) and effective porosity. The pore size is obtained between 60 and 200 μm, which is desirable for the growth and propagation of bone cells. Also, it is revealed that the addition of TiO2 nanoparticles leads to reduce the rate of dissolution of the fabricated bio-nanocomposite scaffolds. 相似文献
8.
The micro-arc oxidation (MAO) coatings were prepared in four different electrolyte systems, including mixed acid, phosphate, phosphate-aluminate and phosphate-silicate electrolytes. The friction and wear properties of MAO coatings in ambient air, seawater and four groups of saline solutions related to seawater were investigated. The results showed that the addition of silicate to phosphate could increase the density of the coating. The phosphate-aluminate ceramic layer exhibited the lowest wear rate in various environments. Additionally, the friction coefficient and wear rate of MAO coating in seawater were lower than those in ambient air, which was due to the boundary lubrication effect of seawater. Meanwhile, the presence of divalent metal salts in seawater made its lubricity better than other salt solutions. 相似文献
9.
Andrew N. Kuhn Haidong Zhao Uzoma O. Nwabara Xiaofei Lu Mingyan Liu Yung-Tin Pan Wenjin Zhu Paul J. A. Kenis Hong Yang 《Advanced functional materials》2021,31(26):2101668
Copper catalysts are widely studied for the electroreduction of carbon dioxide (CO2) to value-added hydrocarbon products. Controlling the surface composition of copper nanomaterials may provide the electronic and structural properties necessary for carbon-carbon coupling, thus increasing the Faradaic efficiency (FE) towards ethylene and other multi-carbon (C2+) products. Synthesis and catalytic study of silver-coated copper nanoparticles (Cu@Ag NPs) for the reduction of CO2 are presented. Bimetallic CuAg NPs are typically difficult to produce due to the bulk immiscibility between these two metals. Slow injection of the silver precursor, concentrations of organic capping agents, and gas environment proved critical to control the size and metal distribution of the Cu@Ag NPs. The optimized Cu@Ag electrocatalyst exhibited a very low onset cell potential of −2.25 V for ethylene formation, reaching a FE towards C2+ products (FEC2+) of 43% at −2.50 V, which is 1.0 V lower than a reference Cu catalyst to reach a similar FEC2+. The high ethylene formation at low potentials is attributed to enhanced C C coupling on the Ag enriched shell of the Cu@Ag electrocatalysts. This study offers a new catalyst design towards increasing the efficiency for the electroreduction of CO2 to value-added chemicals. 相似文献
10.
《Ceramics International》2022,48(13):18925-18932
The dielectric properties of a novel polymer dielectric material were investigated. The conductive phase of RuO2 was synthesized for deposition on the surface of a nanosized BaTiO3 (nBT). The RuO2@nBT hybrid particles were incorporated into a poly (vinylidene fluoride) (PVDF) as a three-phase composite (RuO2@nBT/PVDF). The obtained dielectric constant (ε′) was significantly high (3837.16) for the composite with a volume fraction of = 0.50. The large interfacial polarization between the RuO2?nBT and RuO2?PVDF interfaces considerably increased the value of ε′. Therefore, interfacial polarization is a critical factor in improving the dielectric properties. The dielectric behavior of the RuO2@nBT/PVDF composites can be described using the effective medium percolation theory model, which indicates the significant contributions of the conductive RuO2 phase and high-permittivity nBT phase. 相似文献