全文获取类型
收费全文 | 1635篇 |
免费 | 299篇 |
国内免费 | 45篇 |
专业分类
电工技术 | 53篇 |
综合类 | 64篇 |
化学工业 | 709篇 |
金属工艺 | 240篇 |
机械仪表 | 45篇 |
建筑科学 | 10篇 |
矿业工程 | 22篇 |
能源动力 | 84篇 |
轻工业 | 14篇 |
石油天然气 | 68篇 |
武器工业 | 1篇 |
无线电 | 123篇 |
一般工业技术 | 299篇 |
冶金工业 | 158篇 |
原子能技术 | 34篇 |
自动化技术 | 55篇 |
出版年
2024年 | 10篇 |
2023年 | 47篇 |
2022年 | 45篇 |
2021年 | 60篇 |
2020年 | 63篇 |
2019年 | 48篇 |
2018年 | 56篇 |
2017年 | 71篇 |
2016年 | 71篇 |
2015年 | 53篇 |
2014年 | 88篇 |
2013年 | 124篇 |
2012年 | 96篇 |
2011年 | 90篇 |
2010年 | 73篇 |
2009年 | 84篇 |
2008年 | 79篇 |
2007年 | 97篇 |
2006年 | 97篇 |
2005年 | 86篇 |
2004年 | 74篇 |
2003年 | 61篇 |
2002年 | 55篇 |
2001年 | 48篇 |
2000年 | 54篇 |
1999年 | 25篇 |
1998年 | 34篇 |
1997年 | 20篇 |
1996年 | 36篇 |
1995年 | 18篇 |
1994年 | 25篇 |
1993年 | 14篇 |
1992年 | 18篇 |
1991年 | 17篇 |
1990年 | 11篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1976年 | 3篇 |
排序方式: 共有1979条查询结果,搜索用时 15 毫秒
1.
The effect of the platinum particle size was investigated for the catalytic oxidative dehydrogenation of aqueous ethanol to ethanal at a temperature of 303 K, an ethanol concentration of 260 mol m–3, a partial oxygen pressure 60 kPa, a pH of 9, and an ethanal and ethanoate concentration of 20 mol m–3. A particle size effect on the turnover frequency was observed but only for particle sizes smaller than 2 nm. Hence, the reaction shows a limited structure sensitivity. 相似文献
2.
Electrochemical corrosion measurements have been carried out with Pt-containing and Pt-free Al-diffusion coatings on IN 738 LC in a 90Na2SO4+ 10K2SO4 (mol%) melt at 1173 K. Pt improves the resistance to basic fluxing while there are no significant differences between both coating types in their resistance to acidic fluxing. The corrosion resistance of the Pt-containing coating is also higher in the passive potential region where protective scales rich in Al2O3 are formed. The reason for the different behavior of both coating types appears to be related to the high corrosion resistance of the Pt-rich surface layer of the coating and an increased Al2O3 content in the scale of the Pt-containing type. 相似文献
3.
Polyaniline films prepared on Au wires were employed as substrates to deposit Pt and/or Ru using a potential-programmed perturbation. Different compositions of Pt and Ru ions in acid electrolyte were employed to decorate the electrodes. The atomic percentages of Pt and Ru on Pani were determined by EDAX and particle size and distribution by SEM. The catalytic activity was tested for adsorbed CO and CH3OH electrooxidation. Nanoparticles of Pt–Ru with different Pt–Ru contents were obtained and characterized for each reaction. 相似文献
4.
The surfaces of Pt-45Pd-10Rh foils oxidized over the range 875–1075 K in a 20% O2-Ar mixture at atmospheric pressure were examined by Auger electron, X-ray photoelectron, and Raman spectroscopy. The composition of the oxide formed on the surface was found to vary with temperature from predominantly PdO at 875 K to PdRhO2 at 1075 K. Only a few atomic percent Pt was observed, present in both the metallic and (apparently) +1 oxidation states at 875 K and in the metallic state at 1075 K. The formation of PdRhO2 (and no Rh2O3) at 1075 K was found to persist upon reoxidation following a low-temperature reduction cycle in which the increased Rh concentration on the surface was retained. An oxidation-induced Rh enrichment of the surface of the alloy foil beyond 50 at. % does not appear likely within the temperature/pressure regime investigated. 相似文献
5.
6.
Yubao Li Jingchao Xiao Xinqi Cao Zhiwei Gu Wei Zhang 《Advanced functional materials》2023,33(17):2213385
Here an IR-heating chemical vapor deposition (CVD) approach enabling fast 2D-growth of WSe2 thin films is reported, and the great potential of metal contact doping in building CVD-grown WSe2-based lateral homojunction is demonstrated by contacting with TiN/Ni metals in favor of holes/electrons injection. Shortening nanosheet channel to ≈2 µm leads to pronounced enhancement in the performance of diode. The fabricated WSe2-based diode exhibits high rectification ratios without the need of gate modulation and can work efficiently as photovoltaic cell, with maximum open circuit voltage reaching up to 620 mV and a high power conversion efficiency over 15%, empowering it as superb self-powered photodetector for visible to near-infrared lights, with photoresponsivity over 0.5 A W−1 and a fast photoresponse speed of 10 µs under 520 nm illumination. It is of practical significance to achieve well-performed photovoltaic devices with CVD-grown WSe2 using fab-friendly metals and simple processing, which will help pave the way toward future mass production of optoelectronic chips. 相似文献
7.
8.
Antonio Di Bartolomeo Aniello Pelella Xiaowei Liu Feng Miao Maurizio Passacantando Filippo Giubileo Alessandro Grillo Laura Iemmo Francesca Urban Shi‐Jun Liang 《Advanced functional materials》2019,29(29)
Few‐layer palladium diselenide (PdSe2) field effect transistors are studied under external stimuli such as electrical and optical fields, electron irradiation, and gas pressure. The ambipolar conduction and hysteresis are observed in the transfer curves of the as‐exfoliated and unprotected PdSe2 material. The ambipolar conduction and its hysteretic behavior in the air and pure nitrogen environments are tuned. The prevailing p‐type transport observed at atmospheric pressure is reversibly turned into a dominant n‐type conduction by reducing the pressure, which can simultaneously suppress the hysteresis. The pressure control can be exploited to symmetrize and stabilize the transfer characteristics of the device as required in high‐performance logic circuits. The transistors are affected by trap states with characteristic times in the order of minutes. The channel conductance, dramatically reduced by the electron irradiation during scanning electron microscope imaging, is restored after an annealing of several minutes at room temperature. The work paves the way toward the exploitation of PdSe2 in electronic devices by providing an experiment‐based and deep understanding of charge transport in PdSe2 transistors subjected to electrical stress and other external agents. 相似文献
9.
10.
William A. Lackington Romy Wiestner Elena Pradervand Peter Schweizer Flavia Zuber Qun Ren Mihai Stoica Jörg F. Löffler Markus Rottmar 《Advanced functional materials》2023,33(48):2302069
Titanium alloys are commonly used as biomaterials in musculoskeletal applications, but their long-term efficacy can be limited by wear and corrosion, stress shielding, and bacterial colonization. As a promising alternative, bulk metallic glasses (BMGs) offer superior strength and corrosion resistance, but the influence of their chemical composition on their bioactivity remains largely unexplored. This study, therefore, aims to examine how the surface chemistry of palladium (Pd)-, platinum (Pt)-, and titanium (Ti)-based BMGs can steer their response to biological systems. The chemical composition of BMGs governs their thermophysical and mechanical properties, with Pd-based BMGs showing exceptional glass-forming ability suitable for larger implants, and all BMGs exhibiting a significantly lower Young's modulus than Ti-6Al-4 V (Ti64), suggesting a potential to reduce stress shielding. Although BMGs feature copper depletion at the near surface, their surface chemistry remains more stable than that of Ti64 and supports blood biocompatibility. Fibrin network formation is heavily dependent on BMGs’ chemical composition and Ti-based BMGs support thicker fibrin network formation than Ti64. Furthermore, BMGs outperform Ti64 in promoting mineralization of human bone progenitor cells and demonstrate antimicrobial properties against Staphylococcus aureus in a surface chemistry-dependent manner, thereby indicating their great potential as biomaterials for musculoskeletal applications. 相似文献