全文获取类型
收费全文 | 6999篇 |
免费 | 379篇 |
国内免费 | 52篇 |
专业分类
电工技术 | 133篇 |
综合类 | 26篇 |
化学工业 | 1752篇 |
金属工艺 | 118篇 |
机械仪表 | 211篇 |
建筑科学 | 277篇 |
矿业工程 | 6篇 |
能源动力 | 462篇 |
轻工业 | 725篇 |
水利工程 | 76篇 |
石油天然气 | 115篇 |
无线电 | 652篇 |
一般工业技术 | 1140篇 |
冶金工业 | 337篇 |
原子能技术 | 83篇 |
自动化技术 | 1317篇 |
出版年
2024年 | 19篇 |
2023年 | 144篇 |
2022年 | 291篇 |
2021年 | 405篇 |
2020年 | 294篇 |
2019年 | 335篇 |
2018年 | 416篇 |
2017年 | 357篇 |
2016年 | 355篇 |
2015年 | 236篇 |
2014年 | 319篇 |
2013年 | 641篇 |
2012年 | 356篇 |
2011年 | 505篇 |
2010年 | 350篇 |
2009年 | 326篇 |
2008年 | 288篇 |
2007年 | 217篇 |
2006年 | 201篇 |
2005年 | 140篇 |
2004年 | 111篇 |
2003年 | 117篇 |
2002年 | 90篇 |
2001年 | 64篇 |
2000年 | 73篇 |
1999年 | 50篇 |
1998年 | 77篇 |
1997年 | 41篇 |
1996年 | 49篇 |
1995年 | 40篇 |
1994年 | 36篇 |
1993年 | 44篇 |
1992年 | 36篇 |
1991年 | 32篇 |
1990年 | 30篇 |
1989年 | 20篇 |
1988年 | 35篇 |
1987年 | 30篇 |
1986年 | 20篇 |
1985年 | 15篇 |
1984年 | 27篇 |
1983年 | 22篇 |
1982年 | 22篇 |
1981年 | 16篇 |
1980年 | 20篇 |
1979年 | 16篇 |
1978年 | 17篇 |
1976年 | 18篇 |
1975年 | 19篇 |
1974年 | 12篇 |
排序方式: 共有7430条查询结果,搜索用时 46 毫秒
931.
Zein K. Heiba Mohamed Bakr Mohamed Nasser Y. Mostafa 《International Journal of Applied Ceramic Technology》2019,16(4):1590-1595
Nanocrystalline Ni0.85Se was synthesized by a hydrothermal method. X-ray diffraction analysis by Rietveld method indicated that Ni0.85Se has a NiAs-type hexagonal structure. Narrow crystallite size distribution with an average area-weighted size of 〈ɛF〉 = 8.5 nm is obtained by Warren-Averbach method. Structural analysis revealed deformed Se atoms octahedron with the shortest distance between Se atoms in adjacent planes 〈Se–Se〉adj smaller than between nearest neighbors in layer plane 〈Se–Se〉nea, and a rather short interatomic distance between the transition metal atoms 〈Ni–Ni〉. The optical property of Ni0.85Se was studied by UV-spectroscopy. Magnetic measurement shows a ferromagnetic phase transition for Ni0.85Se below 14 K. 相似文献
932.
Salim Benaissa Mohamed Hamidouche Mostafa Kolli Gilbert Fantozzi 《International Journal of Applied Ceramic Technology》2019,16(2):638-646
The aim of this work was the analysis of the experimental results of a transparent alumina (BMA15) ceramic which was fabricated by Spark Plasma Sintering (SPS) from nanopowder (BMA15, Baikowski Chimie, France), at different temperatures (1200°C, 1250°C, 1300°C). With the application of a maximum uniaxial pressure of 73 MPa during all the fabrication-cycle (more than 3 hours). We sought an optimal sintering temperature combining better optical and mechanical properties of our pellets. The sintered alumina (BMA15) has a crystalline and dense microstructure. The samples sintered at 1200°C exhibit the best optical properties, in particular: good real inline transmission (RIT) and an optical gap greater than those of the samples sintered at 1250°C and 1300°C. Due to their low density, the Young modulus of alumina sintered at 1200 °C, deduced by ultrasound, has a low value which is about 385 GPa. Similarly, its small grain size gives it a better Vickers hardness ~ 21 GPa. Therefore, the value of the coefficient of friction μ stabilizes around the mean value of 0.21. 相似文献
933.
Silicon - Cu2ZnSnSe4 (CZTSe) thin film has been synthesized onto silicon substrates by liquid phase epitaxial growth for the first time in which Au/CZTSe/n-Si/Al heterojunction was successfully... 相似文献
934.
Magdy El-Hagary Said H. Moustafa Hany Hashem Essam R. Shaaban Mohamed Emam-Ismail 《Journal of the American Ceramic Society》2019,102(8):4737-4747
Mn-doped HgO nanostructured thin films (Hg1-xMnxO) have been prepared using electron beam evaporation technique on Corning glass (1022) substrate at room temperature with different concentrations x = 0, 0.015, 0.05, 0.1, 0.15, and 0.2. The microstructural, morphological, semiconducting, and optoelectronic properties of the films have been investigated. The X-ray diffraction spectra suggest a hexagonal wurtzite type structure with lattice parameters decreased with increasing Mn content. It was found that the average particle size of the films decreases with increasing Mn doping which is confirmed by FE-SEM and AFM micrographs. The optical band gap of the investigated Mn-doped HgO nanocrystalline films is determined from the absorption coefficient and found to increase with the increase of Mn concentration which is attributed to the sp-d exchange interaction and/or the quantum confinement effect. The refractive index and extinction coefficient of the Mn-doped HgO films are also reported. The refractive index dispersion n(λ) is analyzed by single-effective-oscillator dispersion model proposed by the Wemple–DiDomenico (WDD). The oscillator parameters were estimated. The obtained dispersion values are suitable for the design of optoelectronic devices. 相似文献
935.
936.
Chouaib Ennawaoui Houda Lifi Abdelowahed Hajjaji Cdric Samuel Mohamed Rguiti Samira Touhtouh Azeddine Azim Christian Courtois 《Polymer Engineering and Science》2019,59(7):1455-1461
In this article, the authors present a porous copolymer film with pseudo‐piezoelectric effects as a new candidate material for sensing applications. Porous films of poly(ethylene‐co‐vinyl acetate) (EVA) with a thicknesses ranging from 160 to 310 μm are fabricated by a coextrusion chemical foaming process and charged using a high‐voltage contact charging process. Output performances (piezoelectric constant and relative permittivity) with related thermal/mechanical stability are specifically studied as a function of the film porosity and of the electrical charging process. The piezoelectric constant d33 increases with the cell porosity and an interesting piezoelectric constant close to 5.1 pC/N is achieved with a porous EVA film containing 65% of porosity. Actual results are then discussed using a theoretical solid–gas multilayer model to describe and predict the pseudo‐piezoelectric effect of porous polymer materials. The originality of this work lies in the fact that all the steps leading to optimize pseudo piezoelectric films are included, and also in the use of EVA which is not a standard piezoelectric material. Therefore, this work is a contribution in the development of low‐cost piezoelectric materials with potential applications as sensor in different fields such as medical, security, environment, sport, and transport. POLYM. ENG. SCI., 59:1455–1461 2019. © 2019 Society of Plastics Engineers 相似文献
937.
Mohamed S. Abdel Aziz Hend E. Salama Gamal R. Saad 《Polymer Engineering and Science》2019,59(2):372-381
Conducting filler based on chitosan and grafted polyaniline (Ch‐g‐PANI) was prepared with different grafting ratios and used as fillers for polyester powder coating system. Differential scanning calorimetry is applied to study the effect of Ch‐g‐PANI on the curing of the polyester powder coating. The activation energy calculated by isoconversional Kissinger method was increased by either increasing the Ch‐g‐PANI content or the content of polyaniline in the filler, suggesting the contribution of the filler in the curing reactions. The cured samples were characterized using FTIR and TG analyses. Thermogravimetric analysis showed that the total thermal stability was enhanced upon the filler addition as detected from the values of integral procedural decomposition temperature. Furthermore, a dielectric study showed that the dielectric constant and loss were increased upon increasing of the filler. Vogel–Fulcher–Tammann equation was well‐fitted when used to examine the dependence of α‐relaxation on the temperature and the dielectrically calculated Tg values were comparable to that measured by DSC. The shielding effectiveness toward microwaves was enhanced by increasing the filler content. POLYM. ENG. SCI., 59:372–381, 2019. © 2018 Society of Plastics Engineers 相似文献
938.
Hindatu Yusuf Syed Mohammad Daniel Syed Mohamed Ramesh Subramaniam 《Chemical Engineering Communications》2019,206(6):731-745
Medium-chain-length poly-3-hydroxyalkanoates (PHA) and carboxyl group-functionalized multiwalled carbon nanotubes (MC) were used to fabricate a composite membrane for application in a double-chambered microbial fuel cell (MFC). MC was composited into PHA at 5%, 10%, and 20% w/w via ultrasound dispersion blending method. PHA-MC composite was compared with Nafion 117 as proton exchange membrane in MFC operated with palm oil mill effluent (POME) wastewater. The composite exhibited prerequisite separator membrane characteristics. The dispersion of MC in the polymer matrix increased its interfacial surface area and water uptake properties. PHA-MC10% membrane in MFC showed maximum power density of 361?mW/m2, which was comparable with Nafion 117 (372?mW/m2). Internal resistance decrease, chemical oxygen demand (COD) removal, coulombic efficiency (CE), and conductivity of the PHA-MC10% were superior to Nafion 117. The environmental-friendly material could provide an alternative towards realizing practical MFC application. 相似文献
939.
Pierrick Paillot Wissam Farhat Frédéric Becquart Ruben Vera Corinne Jegat Mohamed Taha 《应用聚合物科学杂志》2019,136(30):47799
The use of silver as an antimicrobial agent has exhibited great interest in recent years. In this research, poly(ethylene-co-vinyl alcohol) (EVOH)–silver acetate-based antimicrobial materials were prepared at high temperature by reactive extrusion. Silver acetates were used without pretreatment. The thermal reaction of silver acetates in the material and their effect on the thermal and mechanical properties of the polymer were investigated as a function of their concentration. The dispersed silver acetate salts within the EVOH matrix have displayed a significant thermal reaction. This reaction of metallic salts was partial when the extrusion temperature was fixed at 190 °C and completed at 230 °C. The antimicrobial agents also had significant effects on the properties of the matrix. Reductions of glass temperature and storage modulus were observed by the analyses. All the variations were dependent on both the concentration of silver acetate and the extrusion parameters. The antimicrobial activity was studied and demonstrated a promising potential to create an antimicrobial material in a one-step solvent free extrusion method. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47799. 相似文献
940.
Joselito P. Labis Anwar Q. Al-Anazi Hamad A. Al-Brithen Mahmoud Hezam Mohammad Abdulaziz Alduraibi Ahmad Algarni Abdulaziz A. Alharbi Abdulrhman S. Al-Awadi Aslam Khan Ahmed Mohamed El-Toni 《Journal of the American Ceramic Society》2019,102(7):4367-4375
In this study, pulsed laser ablation technique, also known as pulsed laser deposition (PLD), is used to design and grow zinc oxide (ZnO) nanostructures (nanoworms, nanowalls, and nanorods) by template/seeding approach for gas-sensing applications. Conventionally, ZnO nanostructures used for gas-sensing have been usually prepared via chemical route, where the 3D/2D nanostructures are chemically synthesized and subsequently plated on an appropriate substrate. However, using pulsed laser ablation technique, the ZnO nanostructures are structurally designed and grown directly on a substrate using a two-step temperature-pressure seeding approach. This approach has been optimized to design various ZnO nanostructures by understanding the effect of substrate temperature in the 300-750°C range under O2 gas pressure from 10-mTorr to 10 Torr. Using a thin ZnO seed layer as template that is deposited first at substrate temperature of ~300°C at background oxygen pressure of 10 mTorr on Si(100), ZnO nanostructures, such as nanoworms, nanowalls, and nanorods (with secondary flower-like growth) were grown at substrate temperatures and oxygen background pressures of (550°C and 2 Torr), (550°C and 0.5 Torr), and (650°C and 2 Torr), respectively. The morphology and the optical properties of ZnO nanostructures were examined by Scanning Electron Microscope (SEM-EDX), X-ray Diffraction (XRD), and photoluminescence (PL). The PLD-grown ZnO nanostructures are single-crystals and are highly oriented in the c-axis. The vapor-solid (VS) model is proposed to be responsible for the growth of ZnO nanostructures by PLD process. Furthermore, the ZnO nanowall structure is a very promising nanostructure due to its very high surface-to-volume ratio. Although ZnO nanowalls have been grown by other methods for sensor application, to this date, only a very few ZnO nanowalls have been grown by PLD for this purpose. In this regard, ZnO nanowall structures are deposited by PLD on an Al2O3 test sensor and assessed for their responses to CO and ethanol gases at 50 ppm, where good responses were observed at 350 and 400°C, respectively. The PLD-grown ZnO nanostructures are very excellent materials for potential applications such as in dye-sensitized solar cells, perovskite solar cells and biological and gas sensors. 相似文献