全文获取类型
收费全文 | 126篇 |
免费 | 5篇 |
国内免费 | 9篇 |
专业分类
化学 | 66篇 |
晶体学 | 9篇 |
力学 | 1篇 |
物理学 | 64篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 6篇 |
2019年 | 5篇 |
2018年 | 4篇 |
2017年 | 2篇 |
2016年 | 7篇 |
2015年 | 2篇 |
2014年 | 1篇 |
2013年 | 8篇 |
2012年 | 4篇 |
2011年 | 9篇 |
2010年 | 3篇 |
2009年 | 12篇 |
2008年 | 7篇 |
2007年 | 6篇 |
2006年 | 14篇 |
2005年 | 3篇 |
2004年 | 6篇 |
2003年 | 5篇 |
2002年 | 5篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1982年 | 2篇 |
排序方式: 共有140条查询结果,搜索用时 15 毫秒
51.
X.L. Shi H. YangG.Q. Shao X.L. DuanZ. Xiong P. SunT.G. Wang 《Journal of magnetism and magnetic materials》2007
(Mg0.476Mn0.448Zn0.007)(Fe1.997Ti0.002)O4 nanocrystalline powder prepared by high energy ball-milling process were consolidated by microwave and conventional sintering processes. Phases, microstructure and magnetic properties of the ferrites prepared by different processes were investigated. The (Mg0.476Mn0.448Zn0.007)(Fe1.997Ti0.002)O4 nanocrystalline powder could be prepared by high energy ball-milling process of raw Fe3O4, MnO2, ZnO, TiO2 and MgO powders. Prefired and microwave sintered ferrites could achieve the maximum density (4.86 g/cm−3), the average grain size (15 μm) was larger than that (10 μm) prepared by prefired and conventionally sintered ferrites with pure ferrite phase, and the saturation magnetization (66.77 emu/g) was lower than that of prefired and conventionally sintered ferrites (88.25 emu/g), the remanent magnetization (0.7367 emu/g) was higher than that of prefired and conventionally sintered ferrites (0.0731 emu/g). Although the microwave sintering process could increase the density of ferrites, the saturation magnetization of ferrites was decreased and the remanent magnetization of ferrites was also increased. 相似文献
52.
Mirco Eckardt Sabrina L. J. Thomä Dr. Martin Dulle Dr. Gerald Hörner Prof. Birgit Weber Prof. Stefan Förster Prof. Mirijam Zobel 《ChemistryOpen》2020,9(11):1214-1220
Applications in biomedicine and ferrofluids, for instance, require long-term colloidally stable, concentrated aqueous dispersions of magnetic, biocompatible nanoparticles. Iron oxide and related spinel ferrite nanoparticles stabilized with organic molecules allow fine-tuning of magnetic properties via cation substitution and water-dispersibility. Here, we synthesize≤5 nm iron oxide and spinel ferrite nanoparticles, capped with citrate, betaine and phosphocholine, in a one-pot strategy. We present a robust approach combining elemental (CHN) and thermal gravimetric analysis (TGA) to quantify the ratio of residual solvent molecules and organic stabilizers on the particle surface, being of particular accuracy for ligands with heteroatoms compared to the solvent. SAXS experiments demonstrate the long-term colloidal stability of our aqueous iron oxide and spinel ferrite nanoparticle dispersions for at least 3 months. By the use of SAXS we approved directly the colloidal stability of the nanoparticle dispersions for high concentrations up to 100 g L−1. 相似文献
53.
54.
Wang Jin Zhi Fang Qing Qing 《物理学报》2004,(9)
采用溶胶 凝胶自燃烧法制备了纳米尺度的锌钴铁氧体Zn0 6 CoxFe2 4 -xO4 (x =0— 0 30 )粉体 ,分别在不同温度下进行了热处理 ,利用x射线衍射仪 (XRD)和振动样品磁强计 (VSM)对其物相结构和磁性进行了测量和分析 .实验结果表明 ,锌钴铁氧体Zn0 6 Co0 1 5Fe2 2 5O4 在 5 5 0— 80 0℃温度区间出现α Fe2 O3过渡相 ,在高于 80 0℃温度时生成单一尖晶石相锌钴铁氧体 ;随钴含量的增加 ,Zn0 6 CoxFe2 4 -xO4 的比饱和磁化强度先增后减 ,x =0 0 75— 0 1 5比饱和磁化强度较高 ;Zn0 6 CoxFe2 4 -xO4 在 1 30 0℃时x =0 0 75的矫顽力为 4 75 2 0A m ,x≥ 0 1 5时矫顽力在 1 2 0 0℃附近随温度缓慢上升 ,在 1 2 0 0— 1 30 0℃之间为平台状态 ,并且随钴含量的增加 ,矫顽力略有升高 .在x =0 1 0附近 ,可同时获得较高的比饱和磁化强度和较高的矫顽力 相似文献
55.
A. Grusková J. Lipka J. Sláma V. Jančárik M. Papánová M. Štofka A. González G. Mendoza 《Hyperfine Interactions》2006,169(1-3):1223-1230
BaFe12?2x M x Sn x O19 compounds, where M?=?Sn2+, Ni2+ or Zn2+ ions, were synthesized by mechanical milling and partially by citrate precursor methods. Analysis of magneto-crystalline structure has been carried out by Mössbauer spectroscopy. The Sn4+ ions replace Fe3+ ions on 2b and slightly on 2a?+?4f1 sites, Zn2+ ions strongly prefer 4f1 sites, Sn2+ ions prefer 4f1 sites too and Ni2+ ions occupy 4f2 and 12k or 2a sites. The magnetic properties were evaluated by the vibrating sample magnetometry and the thermomagnetic analysis. A large variation of the intrinsic coercivity H c (330 to 78 kA/m) and of temperature coefficient of coercivity of ΔH c /Δ? (0.39 to 0.22 kA/m°C) were achieved as a function of the (Zn–Sn) and (Sn–Sn) substitutions, respectively. The Curie temperature T c decreased with the (Ni–Sn) substitution from 447 to 399°C. 相似文献
56.
In this study, a powder mixture of Zn, Fe2O3 and NiO was used to produce different compositions of Ni1−xZnxFe2O4 (x=0.36, 0.5 and 0.64) nanopowders. High-energy ball milling with a subsequent heat treatment method was carried out. The XRD results indicated that for the content of Zn, x=0.64 a single phase of Ni–Zn ferrite was produced after 30 h milling while for the contents of Zn, x=0.36 and 0.5, the desired ferrite was formed after sintering the 30 h-milled powders at 500 °C. The average crystallite size decreased with increase in the Zn content. A DC electrical resistivity of the Ni–Zn ferrite, however, decreased with increase in the Zn content, its value was much higher than those samples prepared by the conventional ceramic route by using ZnO instead of Zn. This is attributed to smaller grains size which were obtained by using Zn. The FT-IR results suggested two absorption bands for octahedral and tetrahedral sites in the range of 350–700 cm−1. The VSM results revealed that by increasing the Zn content from 0.36 to 0.5, a saturation magnetization reached its maximum value; afterwards, a decrease was observed for Zn with x=0.64. Finally, magnetic permeability and dielectric permittivity were studied by using vector network analyzer to explore microwave-absorbing properties in X-band frequency. The minimum reflection loss value obtained for Ni0.5Zn0.5Fe2O4 samples, about −34 dB at 9.7 GHz, making them the best candidates for high frequency applications. 相似文献
57.
Ataullah Khan Panagiotis G. Smirniotis 《Journal of molecular catalysis. A, Chemical》2008,280(1-2):43-51
A series of modified ferrites were prepared by doping iron oxide with various transition/non-transition/inner-transition metal ions [M = Cr, Mn, Co, Ni, Cu, Zn and Ce] in situ during synthesis. All the modified ferrites thus obtained exhibit remarkably high surface areas, greater than that of pure iron oxide (Fe2O3) sample. The efficacy of the dopant ions in modifying the resultant specific surface area, could be directly related to variations in the rate of crystal growth. The nature and concentration of the foreign cations present in the system govern this variation. Interestingly all the modified ferrites, exhibit a narrow pore size distribution in the range of 4.9–25 nm. XRD analysis revealed the existence of hematite (Fe2O3) phase in all the as-prepared samples. The X-ray diffraction experiments performed on activated catalysts, confirmed the existence of magnetite (Fe3O4) phase with a nominal composition of Fe2.73M0.27O4. These inverse or mixed spinels with general formula A(1−δ)Bδ[AδB(2−δ)]O4, possess highly facile Fe3+ Fe2+ redox couple, the degree of facileness depends on the extent of synergistic interaction between iron and the other substitutent metal ion. The rapid electron hopping between Fe3+ Fe2+ in the Fe3O4 lattice system is essential to catalyze WGS reaction. From TPR it was observed that, incorporation of metal cations into the hematite (-Fe2O3) crystal structure alters the reducibility of the hematite particles, which in turn depends on the nature of the incorporated metal cation. A plausible explanation for the WGS activity over various modified ferrites has been attempted with the help of TPR analysis. 相似文献
58.
Luis A. García Rodenas Miguel A. Blesa Pedro J. Morando 《Journal of solid state chemistry》2008,181(9):2350-2358
Dissolution rates of NiO, CoO, ZnO, α-Fe2O3 and the corresponding ferrites in 0.1 mol dm−3 oxalic acid at pH 3.5 were measured at 70 °C. The dissolution of simple oxides proceeds through the formation of surface metal oxalate complexes, followed by the transfer of surface complexes (rate-determining step). At constant pH, oxalate concentration and temperature, the trend in the first-order rate constant for the transfer of the surface complexes (kMe; Me=Ni, Co, Zn, Fe) parallels that of water exchange in the dissolved metal ions (k−w). Thus, the most important factor determining the rates of dissolution of metal oxides is the lability of Me-O bonds, which is in turn defined by the electronic structure of the metal ion and its charge/radius ratio. UV (384 nm) irradiation does not increase significantly the dissolution rates of NiO, CoO and ZnO, whereas hematite is highly sensitive to UV light. For ferrites, the reactivity order is ZnFe2O4>CoFe2O4?NiFe2O4. Dissolution is congruent, with rates intermediate between those of the constituent oxides, Fe2O3 and MO (M=Co, Ni, Zn), reflecting the behavior of very thin leached layers with little Zn and Co, but appreciable amounts of Ni. The more robust Ni2+ labilizes less the corresponding ferrite. The correlation between log kM and log k−w is somewhat blurred and displaced to lower kM values. Fe(II), either photogenerated or added as salt, enhances the rate of Fe(III) phase transfer. A simple reaction mechanism is used to interpret the data. 相似文献
59.
Iron (III) rich pigments MgFe2O4 and ZnFe2O4 spinel ferrites and α-Fe2O3 hematite were synthesized by Pechini route and precipitation process, respectively. The compounds were characterized by X-ray diffraction (XRD), Mössbauer spectroscopy and visible-NIR spectroscopy. Diffuse reflectance spectra were interpreted in regard of structural features of the three oxides in order to correlate absorption bands positions with structural parameters. It has been demonstrated that the two main absorption edges occurring in visible range (400-800 nm) can be attributed to two 2p(O2−)→3d(Fe3+) charge transfers, the energy being directly linked to the distortion degree of the [FeO6] octahedra. 相似文献
60.
Interplay between elasticity,ferroelectricity and magnetism at the domain walls of bismuth ferrite
下载免费PDF全文
![点击此处可从《固体物理学:研究快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Multiferroic domain walls have recently been proposed as the active element in devices related to spintronics, data storage, and magnetic logic. Among multiferroics, BiFeO3 is by far the most studied material. Its domain walls have shown rich behaviours that include conductivity in an otherwise insulating crystal, and magnetotransport properties that are markedly different from those of the bulk. In this article we summarize the experimental evidence and the current models used to understand the interplay between elastic, electric, and magnetic properties of the domain walls. Starting from the considera‐ tion of antiferromagnetic domain structures on a background of ferroelectric domains, and emphasizing pinning effects, we proceed to discuss the microscopic behavior of ferroelectricity and magnetism at the walls. We describe how domain organization in BiFeO3 is caused by structural transformations, and scrutinize modelling works pinpointing their characteristic features. Finally, we summarize the recent progress and list open questions for future study on BiFeO3 domain structures. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献