全文获取类型
收费全文 | 15178篇 |
免费 | 376篇 |
国内免费 | 366篇 |
专业分类
电工技术 | 119篇 |
综合类 | 328篇 |
化学工业 | 3538篇 |
金属工艺 | 1735篇 |
机械仪表 | 2138篇 |
建筑科学 | 434篇 |
矿业工程 | 373篇 |
能源动力 | 702篇 |
轻工业 | 343篇 |
水利工程 | 74篇 |
石油天然气 | 164篇 |
武器工业 | 43篇 |
无线电 | 1087篇 |
一般工业技术 | 3016篇 |
冶金工业 | 431篇 |
原子能技术 | 215篇 |
自动化技术 | 1180篇 |
出版年
2024年 | 10篇 |
2023年 | 150篇 |
2022年 | 246篇 |
2021年 | 291篇 |
2020年 | 292篇 |
2019年 | 255篇 |
2018年 | 239篇 |
2017年 | 322篇 |
2016年 | 399篇 |
2015年 | 451篇 |
2014年 | 646篇 |
2013年 | 1127篇 |
2012年 | 662篇 |
2011年 | 1181篇 |
2010年 | 794篇 |
2009年 | 974篇 |
2008年 | 939篇 |
2007年 | 982篇 |
2006年 | 871篇 |
2005年 | 697篇 |
2004年 | 692篇 |
2003年 | 617篇 |
2002年 | 533篇 |
2001年 | 367篇 |
2000年 | 315篇 |
1999年 | 322篇 |
1998年 | 272篇 |
1997年 | 254篇 |
1996年 | 203篇 |
1995年 | 177篇 |
1994年 | 133篇 |
1993年 | 114篇 |
1992年 | 75篇 |
1991年 | 69篇 |
1990年 | 57篇 |
1989年 | 44篇 |
1988年 | 44篇 |
1987年 | 28篇 |
1986年 | 21篇 |
1985年 | 24篇 |
1984年 | 11篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 5篇 |
1978年 | 2篇 |
1976年 | 4篇 |
1975年 | 1篇 |
1974年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 53 毫秒
41.
《Ceramics International》2020,46(4):4289-4299
In order to propel the application of the developed CuNi-Xwt%Ti active filler metal in AlN brazing and get the universal reactive wetting mechanism between liquid metal and solid ceramic, the reactive wetting behavior and mechanism of AlN ceramic by CuNi-Xwt%Ti active filler metal were investigated. The results indicate that, with the increasing Ti content, surface tension for liquid CuNi-Xwt%Ti filler metal increases at low-temperature interval, but very similar at high-temperature interval, which influence the wetting behavior on AlN ceramic obviously. CuNi/AlN is the typical non-reactive wetting system, the wetting process including rapid wetting stage and stable stage. The wettability is depended on surface tension of the liquid CuNi filler metal completely. However, the wetting process of CuNi-8wt.%Ti/AlN and CuNi-16 wt%Ti/AlN reactive wetting system is composed by three stages, which are rapid wetting stage decided by surface tension, slow wetting stage caused by interfacial reaction and stable stage. For CuNi-8wt.%Ti/AlN and CuNi-16 wt%Ti/AlN reactive wetting system, although the surface tension of liquid filler metal is the only factor to influence the instant wetting angle θ0 at rapid wetting stage, the reduced free energy caused by interfacial reaction at slow wetting stage plays the decisive role in influencing the final wettability. 相似文献
42.
《International Journal of Hydrogen Energy》2020,45(27):13789-13804
Herein, we report the fine tuning of electrocatalytic characteristics of CeO2–TiO2 composite by surface engineering to reduce overpotential and to improve exchange current density for enhanced alkaline hydrogen evolution reaction (HER). The enhanced electrocatalytic activity of the surface engineered CeO2–TiO2 composite through Ni and P decoration is attributed to the improved electron transport ability. The surface roughness characteristics and surface composition of electroactive species are tuned to generate high electronic conductivity on the surface engineered composite electrode surface. The developed hard electrode with leptokurtic surface (Sku > 3) exhibited a high average roughness value (Sa) of 3 μm due to incorporation of the mesoporous catalyst material into it. Tuning of a compact and continuous electrode surface with critical composition of elements Ni (52 at.%), P (20 at.%), Ce (9 at.%) and Ti (8 at.%) furnishes the high conductivity (contact potential difference = 0.83 V) to the electrode. The developed electrode with surface engineered CeO2–TiO2 catalyst exhibited a low overpotential of −111 mV (at a high current density of 250 mA cm−2) and high exchange current density (1.6 × 10−1 mA cm−2) with low charge transfer resistance (615 Ω cm2). High electrocatalytic activity and stability of the surface engineered CeO2–TiO2 catalyst electrode during alkaline (32 w/v.% NaOH) HER ensure its promising performance and applicability for long term HER. 相似文献
43.
44.
45.
Nadir Ouldhamadouche Amine Achour Raul Lucio-Porto Mohammad Islam Shahram Solaymani Ali Arman Azin Ahmadpourian Hamed Achour Laurent Le Brizoual Mohamed Abdou Djouadi Thierry Brousse 《材料科学技术学报》2018,34(6):976-982
Vanadium nitride(VN) was deposited by DC-sputtering on a vertically aligned carbon nanotube(CNTs)template for the purpose of nano-structuration. This led to the fabrication of hierarchically composite electrodes consisting of porous and nanostructured VN grown on vertically aligned CNTs in a nano-treelike configuration for micro-supercapacitor application. The electrodes show excellent performance with an areal capacitance as high as 37.5 m F cm~(-2) at a scan rate of 2 mV s~(-1) in a 0.5 MK_2SO_4 mild electrolyte solution. Furthermore, the capacitance decay was only 15% after 20,000 consecutive cycles. Moreover,the capacitance was found to increase with VN deposit thickness. The X-ray photoelectron spectroscopy analyses of the electrodes before and after cycling suggest that the oxide layers that form at the VN surface is the responsible for the redox energy storage in this material. Such electrodes can compete with other transition metal nitride based electrodes for micro-supercapacitors. 相似文献
46.
Wenbin Li Amir Ghazanfari Devin McMillen Ming C. Leu Gregory E. Hilmas Jeremy Watts 《Ceramics International》2018,44(11):12245-12252
The Ceramic On-Demand Extrusion (CODE) process is a novel additive manufacturing method for fabricating dense (~99% of theoretical density) ceramic components from aqueous, high solids loading pastes (>50?vol%). In this study, 3?mol% Y2O3 stabilized zirconia (3YSZ) specimens were fabricated using the CODE process. The specimens were then dried in a humidity-controlled environmental chamber and afterwards sintered under atmospheric conditions. Mechanical properties of the sintered specimens were examined using ASTM standard test techniques, including density, Young’s modulus, flexural strength, Weibull modulus, fracture toughness, and Vickers hardness. The microstructure was analyzed and grain size measured using scanning electron microscopy. The results were compared with those from Direct Inkjet Printing, Selective Laser Sintering, Lithography-based Ceramic Manufacturing (LCM), and other extrusion-based processes, and indicated that zirconia specimens produced by CODE exhibit superior mechanical properties among the additive manufacturing processes. Several sample components were produced to demonstrate CODE’s capability for fabricating geometrically complex ceramic components. The surface roughness of these components was also examined. 相似文献
47.
Enikö György Constantin Logofatu Ángel Pérez del Pino Angela Datcu Oana Pascu Raluca Ivan 《Ceramics International》2018,44(2):1826-1835
Light induced catalytic processes have attracted significant attention during the last years for wastewater treatment due to their efficiency in decomposition of organic contaminants. In this study we report the synthesis of graphene oxide (GO)/ZnO hybrid layers with high photocatalytic efficiency using laser radiation. The results show that the hybrid layers exhibit much improved photodecomposition efficiency as compared to pure GO or ZnO both under UV and visible-light irradiation. The enhanced photocatalytic efficiency of the hybrid as compared to the reference pure ZnO and GO layers was attributed to the contribution of GO to the separation and transport of the photogenerated charge carriers. Additionally, under visible light irradiation the organic molecules can act as first sensitizers in the degradation process. The recyclability of the layers was also investigated through repetitive photodegradation cycles under UV- or visible-light irradiation. After consecutive degradation runs, the hybrid photocatalyst layers were still stable and retained high degradation efficiency, ensuring reusability. The photocatalytic activity of the layers was correlated with the gradual change of their chemical structure during consecutive degradation cycles. Owing to the high photodegradation efficiency, reusability, and ease of recovery the synthesised hybrid layers consisting of easily available materials are suitable for environmental purification applications. 相似文献
48.
Min Yan Attila Csík Chun-Chuan Yang Yun Luo Tamás Fodor Shinn-Jyh Ding 《Ceramics International》2018,44(16):19665-19671
Veneering ceramics should be strongly bonded to zirconia core in order to achieve successfully long-term clinical practice. Indeed, to pursue the high zirconia core–veneering ceramic bonding is still a concerned issue. In this regard, this study was to treat zirconia surface using a 3?wt% Si3N4 solution in 4?M NaOH and to investigate the effect of soaking time (5, 10, and 20 days) on the surface properties of zirconia and shear bond strength between zirconia and veneering ceramics. The residual veneering ceramics on zirconia surfaces and failure modes were also examined after fracture. The results showed that the phase composition of zirconia before and after surface modification was not changed. The elemental mapping and depth profiling consistently revealed the soaking-time-dependent Si content on the zirconia surface. The surface roughness of zirconia was significantly (P?<?0.05) increased with the increasing soaking time. When zirconia was treated for 10 days, the shear bond strength value of 27.4?MPa was significantly (P?<?0.05) higher than the control (18.6?MPa), associated with greater remaining amounts of veneering ceramics on the zirconia surface. The failure mode of the treated zirconia was almost the mixed failure. On the basis of the data, surface modification using Si3N4 in NaOH solution for zirconia core could be a simple and effective method for enhancing the veneering ceramic–zirconia bonding. 相似文献
49.
Yue Wang Jingyi Qiu Zhongbao Yu Hai Ming Meng Li Songtong Zhang Yusheng Yang 《Ceramics International》2018,44(2):1312-1320
Surface-interface reaction between the electrode and electrolyte plays a key role in lithium-ion storage properties, especially for high voltage cathode such as LiCoPO4 and Ni-riched cathode. Generally, surface modification is an effective method to improve the electrochemical performance of electrode materials. Herein, in order to revise the LiCoPO4 cathode with desirable properties, uniform AlF3-modified LiCoPO4 (LiCoPO4@AlF3) cathode materials in nano-sized distribution are synthesized. XRD result indicates that there is no structural transformation observed after AlF3 coating. TEM characterization and XPS analysis reveal that the surface of LiCoPO4 particle is coated by a nano-sized uniform AlF3 layer. Further, the electrochemical results indicate that AlF3 layer significantly improves the cycling and rate performances of LiCoPO4 cathode within the voltage range of 3.0–5.0 V. After a series of optimization, 4 mol% AlF3-coated LiCoPO4 material exhibits the best properties including an initial discharge capacity of 159 mA h g?1 at 0.1 C with 91% capacity retention after 50 cycles, especially a discharge capacity of 90 mA h g?1 can be obtained at 1 C rate. CV curves indicate that the polarization of cathode is reduced by AlF3 layer and EIS curves reveal that AlF3 layer relieves the increase of resistance to facilitate Li-ion transfer at the interface between electrode and electrolyte during the cycling process. The enhanced electrochemical performances are attributed to that the AlF3 layer can stabilize the interface between the cathode and electrolyte, form steady SEI film and suppress the electrolyte continuous decomposition at 5 V high voltages. This feasible strategy and novel characteristics of LiCoPO4@AlF3 could promise the prospective applications in the stat-art of special lithium-ion battery with high energy and/or power density. 相似文献