全文获取类型
收费全文 | 28120篇 |
免费 | 2289篇 |
国内免费 | 1274篇 |
专业分类
电工技术 | 857篇 |
综合类 | 896篇 |
化学工业 | 10259篇 |
金属工艺 | 2059篇 |
机械仪表 | 329篇 |
建筑科学 | 331篇 |
矿业工程 | 835篇 |
能源动力 | 3811篇 |
轻工业 | 683篇 |
水利工程 | 33篇 |
石油天然气 | 723篇 |
武器工业 | 36篇 |
无线电 | 2235篇 |
一般工业技术 | 5885篇 |
冶金工业 | 1958篇 |
原子能技术 | 337篇 |
自动化技术 | 416篇 |
出版年
2024年 | 80篇 |
2023年 | 628篇 |
2022年 | 890篇 |
2021年 | 1227篇 |
2020年 | 1110篇 |
2019年 | 1102篇 |
2018年 | 1029篇 |
2017年 | 1063篇 |
2016年 | 939篇 |
2015年 | 923篇 |
2014年 | 1439篇 |
2013年 | 1600篇 |
2012年 | 1745篇 |
2011年 | 2367篇 |
2010年 | 1779篇 |
2009年 | 1704篇 |
2008年 | 1467篇 |
2007年 | 1611篇 |
2006年 | 1364篇 |
2005年 | 1096篇 |
2004年 | 955篇 |
2003年 | 883篇 |
2002年 | 749篇 |
2001年 | 611篇 |
2000年 | 619篇 |
1999年 | 450篇 |
1998年 | 381篇 |
1997年 | 296篇 |
1996年 | 281篇 |
1995年 | 204篇 |
1994年 | 190篇 |
1993年 | 141篇 |
1992年 | 159篇 |
1991年 | 123篇 |
1990年 | 113篇 |
1989年 | 90篇 |
1988年 | 57篇 |
1987年 | 38篇 |
1986年 | 16篇 |
1985年 | 33篇 |
1984年 | 24篇 |
1983年 | 16篇 |
1982年 | 25篇 |
1981年 | 17篇 |
1980年 | 12篇 |
1979年 | 9篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1959年 | 5篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
992.
Kate Ryan Sabine M. Neumayer Harsha Vardhan R. Maraka Nicolae-Viorel Buchete Andrei L. Kholkin James H. Rice 《Science and Technology of Advanced Materials》2013,14(1):172-179
AbstractNanocomposites of diphenylalanine (FF) and carbon based materials provide an opportunity to overcome drawbacks associated with using FF micro- and nanostructures in nanobiotechnology applications, in particular their poor structural stability in liquid solutions. In this study, FF/graphene oxide (GO) composites were found to self-assemble into layered micro- and nanostructures, which exhibited improved thermal and aqueous stability. Dependent on the FF/GO ratio, the solubility of these structures was reduced to 35.65% after 30 min as compared to 92.4% for pure FF samples. Such functional nanocomposites may extend the use of FF structures to e.g. biosensing, electrochemical, electromechanical or electronic applications. 相似文献
993.
《Chemical Engineering Communications》2012,199(2):263-277
AbstractIn this work, the degradation of terephthalic acid (TA) by vanadium oxide (VxOy) supported on zinc oxide (ZnO) was evaluated in a photocatalytic ozonation treatment based on two UV-A LEDs distributions. TEM analysis and specific surface area measurement suggest that VxOy is not supported on ZnO, while the EDXRF and XPS analysis indicated the presence of VxOy. The XPS analysis on VxOy/ZnO catalyst showed non-significant surface change between fresh and used catalyst. However, ozone decomposition showed a higher reaction rate constant for catalytic (230%) and photocatalytic ozonation (310%) in comparison with single ozone treatment. Photocatalytic ozonation with central and external irradiation arrays was evaluated in TA elimination by a kinetic study. The irradiation arrays had not statistical differences in the TA decomposition or oxalic acid formation. These results suggest that the construction of central bodies inside the reactor could be not necessary for photocatalytic processes. 相似文献
994.
This paper presents experimental and numerical studies on the fuel reforming process on an Ni/YSZ catalyst. Nickel is widely known as a catalyst material for Solid Oxide Fuel Cells. Because of its prices and catalytic properties, Ni is used in both electrodes and internal reforming reactors. To optimize the reforming reactors, detailed data about the entire reforming process is required. In the present paper kinetics of methane/steam reforming on the Ni/YSZ catalyst was experimentally investigated. Measurements including different thermal boundary conditions, the fuel flow rate and the steam-to-methane ratios were performed. The reforming rate equation derived from experimental data was used in the numerical model to predict synthetic gas composition at the outlet of the reformer. 相似文献
995.
996.
Over the past three decades, transparent high electron mobility molecular materials have attracted intensive research efforts for organic light-emitting diodes as electron-transport layer for the sake of low working voltage, high power efficiency and operational stability. However, developing high-performing electron-transport materials presents a demanding challenge owing to difficulties in synthesis, purification and/or processing. In this contribution, we show that n-doping a simple and facilely available phenanthroline derivative, namely 3-(6-diphenylphosphinylnaphth-2-yl)-1,10-phenanthroline Phen-NaDPO with a high Tg of 116 °C, is capable of greatly increasing the electron conductivity up to 3.3 × 10−4 S m−1. The characterization of the blue sky fluorescent and green phosphorescent OLEDs involving this doped electron-transport layer Phen-NaDPO:50% wt Cs2CO3 revealed comparable performances to the analogue BPhen (Tg ≈ 66 °C) OLEDs. For instance, the resulting sky blue fluorescent OLEDs provided ca. 15 cd/A, 13 lm/W @1000 cd m−2 & t95 ≈ 167 h @1000 cd m−2. The present finding shows that the doped Phen-NaDPO may be a robust electron-transport material for optoelectronics. 相似文献
997.
《Journal of the European Ceramic Society》2017,37(16):5315-5320
Films of copper and cobalt-iron oxalates were prepared from suspensions of powders in ethane-1,2-diol deposited on glass or polycarbonate substrates. Two-dimensional structures of oxides, resolved on the scale of less than ten micrometers, were formed by laser insolation of these films, using a photolithography machine. The nature of the constitutive phases of the oxides formed tends to show that the laser heating makes it possible to reach locally, temperatures higher than 1000 °C. The oxides formed are thus sintered. The residual oxalate can be removed by washing or dissolving, leaving the oxide structure on its substrate. In spite of a perfectible sintering, the formed structures could interest different technological applications (electronic or magnetic devices, gas sensors, photovoltaic systems…) requiring the shaping of simple or mixed oxides on a scale close to the micrometer. The process of selective laser decomposition of oxalates, could subsequently be suitable for additive manufacturing of 3D parts. 相似文献
998.
Heterostructured dysprosium vanadate – ZnO for photo-electrocatalytic and self-cleaning applications
In this article, we report fabrication of 5 wt% of Dy as DyVO4 supported ZnO by template-free hydrothermal-thermal decomposition method and its photocatalytic activity towards degradation of azo dyes Rhodamine-B (Rh-B) and Trypan Blue (TB) in solar light, Electrocatalytic activity in methanol oxidation and Self-cleaning properties. The as prepared DyVO4-ZnO was characterized by surface analytical and spectroscopic techniques. The results suggested that Dysprosium vanadate doping on ZnO has increased its photocatalytic efficiency with high reusability. DyVO4-ZnO exhibits higher electrocatalytic activity than prepared ZnO for methanol electrooxidation in alkaline medium, revealing its promising potential as the anode in direct methanol fuel cells. Hydrophobicity of ZnO increases by doping of DyVO4. 相似文献
999.
This article describes the preparation and characterization of composites containing poly(ethylene-co-butyl acrylate) (EBA–13 and EBA–28 with 13 and 28 wt % butyl acrylate, respectively) and 2–12 wt % (0.5–3 vol %) of aluminum oxide nanoparticles (two types differing in specific surface area and hydroxyl-group concentration; uncoated and coated with, respectively, octyltriethoxysilane and aminopropyltriethoxysilane). A greater surface coverage was obtained with aminopropyltriethoxysilane than with octyltriethoxysilane. An overall good dispersion was obtained in the EBA-13 composites prepared by extrusion compounding. Composites with octyltriethoxysilane-coated nanoparticles showed the best dispersion. The addition of the nanoparticles to EBA–28 resulted in poor dispersion, probably due to insufficiently high shear forces acting during extrusion mixing which were unable to break down nanoparticle agglomerates. The nanoparticles had no effect on the crystallization kinetics in the EBA–13 composites, but in the EBA–28 composites the presence of the nanoparticles led to an increase in the crystallization peak temperature, suggesting that the nanoparticles had a nucleating effect in this particular polymer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
1000.
《Current Opinion in Solid State & Materials Science》2014,18(1):46-52
We review the use of two-dimensional psuedomorphic materials to accommodate an extraordinary range of misfit and allow novel new phases to be grown epitaxially. These materials assume the structure of the substrate and can thus be regarded as metamaterials. We illustrate these principles through a number of systems, including a detailed structural and spectroscopic study of epitaxial VO2/NiO heterostructures. In this case the metamaterial is VO1+x which is structurally and electronically distinct from the bulk of the VO2 film. In the transition region the crystal structure adopts that of the NiO layer, while the oxidation state of vanadium increases from ∼3+ to ∼4+ with thickness, accompanied by increasing lattice disorder. The formation and evolution of this interfacial phase, VO1+x, accommodates the change in crystal symmetry across the interface from the rock-salt structure of NiO to the rutile structure of VO2. The use of two-dimensional metamaterials opens a wealth of new opportunities for the growth of new materials with novel properties. 相似文献