全文获取类型
收费全文 | 1498篇 |
免费 | 153篇 |
国内免费 | 78篇 |
专业分类
电工技术 | 11篇 |
综合类 | 58篇 |
化学工业 | 695篇 |
金属工艺 | 23篇 |
机械仪表 | 11篇 |
建筑科学 | 47篇 |
矿业工程 | 33篇 |
能源动力 | 77篇 |
轻工业 | 66篇 |
水利工程 | 9篇 |
石油天然气 | 32篇 |
武器工业 | 8篇 |
无线电 | 15篇 |
一般工业技术 | 96篇 |
冶金工业 | 248篇 |
原子能技术 | 278篇 |
自动化技术 | 22篇 |
出版年
2024年 | 5篇 |
2023年 | 10篇 |
2022年 | 42篇 |
2021年 | 49篇 |
2020年 | 62篇 |
2019年 | 49篇 |
2018年 | 38篇 |
2017年 | 37篇 |
2016年 | 53篇 |
2015年 | 41篇 |
2014年 | 62篇 |
2013年 | 225篇 |
2012年 | 59篇 |
2011年 | 86篇 |
2010年 | 61篇 |
2009年 | 84篇 |
2008年 | 61篇 |
2007年 | 65篇 |
2006年 | 67篇 |
2005年 | 72篇 |
2004年 | 64篇 |
2003年 | 52篇 |
2002年 | 48篇 |
2001年 | 65篇 |
2000年 | 40篇 |
1999年 | 29篇 |
1998年 | 26篇 |
1997年 | 21篇 |
1996年 | 18篇 |
1995年 | 11篇 |
1994年 | 16篇 |
1993年 | 16篇 |
1992年 | 17篇 |
1991年 | 12篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1987年 | 8篇 |
1986年 | 4篇 |
1985年 | 8篇 |
1984年 | 14篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1974年 | 1篇 |
1967年 | 1篇 |
1963年 | 1篇 |
1959年 | 1篇 |
1958年 | 2篇 |
1957年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有1729条查询结果,搜索用时 15 毫秒
51.
Effect of CO2 Exposure on the Chemical Stability and Mechanical Properties of BaZrO3‐Ceramics
下载免费PDF全文
![点击此处可从《Journal of the American Ceramic Society》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Rokas Sažinas Carlos Bernuy‐López Mari‐Ann Einarsrud Tor Grande 《Journal of the American Ceramic Society》2016,99(11):3685-3695
The reactivity of BaZrO3 with CO2 has been addressed as one of the major challenges with BaZrO3‐based electrolytes in protonic ceramic fuel cells. Here, we present a study of the effect of CO2 exposure on BaZrO3‐materials at elevated temperatures. Dense BaZr1?xYxO3?x/2 (x = 0, 0.05, 0.1, 0.2) and BaCe0.2Zr0.7Y0.1O2.95 ceramics were prepared by sintering of powder prepared by spray pyrolysis. The Vickers indentation method was used to determine the hardness and estimate the fracture toughness of pristine materials as well as the corresponding materials exposed to CO2. Formation of BaCO3 on the surface of exposed ceramics was confirmed by X‐ray diffraction and electron microcopy. The reaction resulted in formation of Ba‐deficient perovskite at the exposed surface. The reaction with CO2 was most pronounced at 650°C compared to the other temperatures applied in the study. The reactivity was also shown to depend on the Y‐content and the grain size and was most pronounced for BaZr0.9Y0.1O2.95. The reaction with CO2 was observed to have a profound effect on the fracture toughness of the ceramics, demonstrating a depression of the mechanical stability of the materials. The results are discussed with respect to the chemical and mechanical stability of BaZrO3 materials, with particular emphasis on the composition and grain size. 相似文献
52.
《Ceramics International》2016,42(3):4507-4516
Three dimensional, highly porous, ZrO2 scaffolds coated by glass–ceramic derived from 45S5 bioglass were fabricated. The surface reactivity of 45S5 in aqueous solution was investigated as a function of the immersion time. The influence of the solid loading on the rheological behavior of 45S5 aqueous slips with ammonium polyacrylate (NH4PA) was studied; besides the effect of poly(vinyl)alcohol (PVA) on the relative viscosity was determined. The structure and microstructure of uncoated and coated ZrO2 scaffolds were characterized. The high ionic exchange capability of 45S5 was demonstrated by the pH rise, the significant weight loss and the amorphous calcium phosphate nucleation, upon its immersion in aqueous solution. The addition of PVA did not affect the dispersion properties of the 45S5 powder, which were basically controlled by its negative surface charge. 30 wt% 45S5 slips with 4 wt% PVA exhibited a yield stress and an adequate viscosity in the low shear rate range, to produce a bioglass coating into the ZrO2 scaffold. The glass-ceramic coating was distributed along the strut surfaces, forming a thin film without altering the porosity and the strut thickness of the original ZrO2 scaffold structure. 相似文献
53.
Copolymerization is a useful way of modifying the physical properties of a material to meet specific needs, but it can result in a significant light scattering loss due to dielectric fluctuations in the material. Ideal random copolymers are known to be more transparent; however, the light-scattering properties of such copolymers in bulk have not been fully studied. In this paper, two representative ideal random copolymers were synthesized: methyl methacrylate (MMA)/benzyl methacrylate (BzMA) and MMA/2,2,2-trifluoroethyl methacrylate (TFEMA). The effects of copolymer composition and polymerization temperature on the light-scattering properties were investigated. Polarized light scattering (VV) in copolymers was more sensitive to the polymerization temperature. Higher temperatures were necessary to homogenize the dielectric fluctuations and minimize excess light scattering. However, once the heterogeneous structures vanished, the copolymer bulk exhibited low scattering losses, which are comparable with homopolymers, over the entire range of copolymer compositions. 相似文献
54.
55.
56.
Dmitry Oshchepkov Irina Chadaeva Rimma Kozhemyakina Karina Zolotareva Bato Khandaev Ekaterina Sharypova Petr Ponomarenko Anton Bogomolov Natalya V. Klimova Svetlana Shikhevich Olga Redina Nataliya G. Kolosova Maria Nazarenko Nikolay A. Kolchanov Arcady Markel Mikhail Ponomarenko 《International journal of molecular sciences》2022,23(5)
57.
Manuel Gacitúa Alexander Carreo Rosaly Morales-Guevara Dayn Pez-Hernndez Jorge I. Martínez-Araya Eyleen Araya Marcelo Preite Carolina Otero María Macarena Rivera-Zaldívar Andrs Silva Juan A. Fuentes 《International journal of molecular sciences》2022,23(5)
Searching for adequate and effective compounds displaying antimicrobial activities, especially against Gram-positive bacteria, is an important research area due to the high hospitalization and mortality rates of these bacterial infections in both the human and veterinary fields. In this work, we explored (E)-4-amino-3-((3,5-di-tert-butyl-2-hydroxybenzylidene)amino) benzoic acid (SB-1, harboring an intramolecular hydrogen bond) and (E)-2-((4-nitrobenzilidene)amino)aniline (SB-2), two Schiff bases derivatives. Results demonstrated that SB-1 showed an antibacterial activity determined by the minimal inhibitory concentration (MIC) against Staphylococcus aureus, Enterococcus faecalis, and Bacillus cereus (Gram-positive bacteria involved in human and animal diseases such as skin infections, pneumonia, diarrheal syndrome, and urinary tract infections, among others), which was similar to that shown by the classical antibiotic chloramphenicol. By contrast, this compound showed no effect against Gram-negative bacteria (Klebsiella pneumoniae, Escherichia coli, and Salmonella enterica). Furthermore, we provide a comprehensive physicochemical and theoretical characterization of SB-1 (as well as several analyses for SB-2), including elemental analysis, ESMS, 1H and 13C NMR (assigned by 1D and 2D techniques), DEPT, UV-Vis, FTIR, and cyclic voltammetry. We also performed a computational study through the DFT theory level, including geometry optimization, TD-DFT, NBO, and global and local reactivity analyses. 相似文献
58.
59.
60.
水淬渣的胶凝活性及其形成机理 总被引:2,自引:0,他引:2
采用重新熔融水淬的方法制备不同水淬矿渣样品,综合进行净浆强度实验和碱溶出实验研究,借助XRD,DTA, TEM, SEM和EDX等分析手段,研究了矿渣形成过程、形成结构和胶凝性能之间的关系,并在此基础上探讨了矿渣潜在胶凝活性的形成机理. 研究表明,在合适的排渣温度和冷却速度条件下,水淬渣能够形成分相结构,对水淬渣胶凝活性产生重要影响. 分相矿渣具有富钙相和富硅相,富钙相的迅速溶解和富硅相的缓慢溶解是水淬渣水化过程中产生足够早期强度和发挥稳定后期强度的主要原因. 由于玻璃分相的影响,排渣过程存在最佳工艺条件,即最佳的排渣过程能使水淬渣形成玻璃分相结构,从而具有最好的活性. 相似文献