全文获取类型
收费全文 | 226篇 |
免费 | 30篇 |
国内免费 | 25篇 |
专业分类
电工技术 | 3篇 |
综合类 | 11篇 |
化学工业 | 46篇 |
金属工艺 | 18篇 |
机械仪表 | 3篇 |
建筑科学 | 1篇 |
矿业工程 | 1篇 |
轻工业 | 1篇 |
武器工业 | 1篇 |
无线电 | 57篇 |
一般工业技术 | 127篇 |
冶金工业 | 9篇 |
原子能技术 | 1篇 |
自动化技术 | 2篇 |
出版年
2024年 | 1篇 |
2023年 | 12篇 |
2022年 | 5篇 |
2021年 | 9篇 |
2020年 | 12篇 |
2019年 | 14篇 |
2018年 | 7篇 |
2017年 | 19篇 |
2016年 | 13篇 |
2015年 | 8篇 |
2014年 | 21篇 |
2013年 | 14篇 |
2012年 | 11篇 |
2011年 | 14篇 |
2010年 | 16篇 |
2009年 | 9篇 |
2008年 | 12篇 |
2007年 | 15篇 |
2006年 | 7篇 |
2005年 | 10篇 |
2004年 | 8篇 |
2003年 | 18篇 |
2002年 | 3篇 |
2001年 | 9篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1985年 | 1篇 |
排序方式: 共有281条查询结果,搜索用时 15 毫秒
1.
2.
S. Ashhab 《Journal of Low Temperature Physics》2005,140(1-2):51-65
We study the thermodynamic phases of a Bose gas of spin-1/2 atoms in the Hartree-Fock approximation. Our main result is that, for repulsive or weakly attractive inter-component interaction strength, the superfluid and ferromagnetic phase transitions occur at the same temperature. For strongly attractive inter-component interaction strength, however, the ferromagnetic phase transition occurs at a higher temperature than the superfluid phase transition. We also find that the presence of a condensate acts as an effective magnetic field that polarizes the normal cloud. We finally comment on the validity of the Hartree-Fock approximation in describing different phenomena in this system. 相似文献
3.
4.
采用直流磁控溅射方法在玻璃基片上制备了不同Fe掺杂量的TiO2薄膜,并对薄膜分别在空气和真空氛围下500℃进行30min退火处理。研究了Fe掺杂量和退火氛围对TiO2薄膜的结晶状态、表面形貌和磁性能的影响。结果表明,真空中500℃下退火的Fe掺杂的TiO2薄膜表现为非晶态结构,没有观察到室温铁磁性能的出现,而空气中500℃退火的样品显示出良好的结晶状态,且所有掺杂的样品均显示出室温铁磁性,并且随着Fe掺杂量的增加,TiO2薄膜的晶体结构逐渐由锐钛矿相向金红石相转变。 相似文献
5.
Wei Yu Zishen Wang Xiaoxu Zhao Junyong Wang Tun Seng Herng Teng Ma Zhiyu Zhu Jun Ding Goki Eda Stephen J. Pennycook Yuan Ping Feng Kian Ping Loh 《Advanced functional materials》2020,30(31)
Chemical exfoliation has been used for the fast and large‐scale production of 2D nanosheets from graphene and transition metal dichalcogenides; however, it is rarely used for domain engineering of exfoliated nanosheets. Herein, it is found that the use of large sized molecular intercalants during electrochemical intercalation induce atomic row dislocation and parallel mirror twin boundaries (MTBs) on an otherwise pristine rhenium disulfide (ReS2) crystal, such that the exfoliated flakes possess a parallel, multi‐domain structure. These domains can be distinguished under a polarized microscope owing to the intrinsic in‐plane optical dichroic properties of ReS2, thereby affording a way to track the number of domains introduced versus the size of the molecular intercalant during electrochemical exfoliation. Ferromagnetism is detected on the intercalated sample using large sized molecular intercalants. Density function theory suggests that these may be due to the coupled effects of lattice strain and S vacancies in the MTBs. 相似文献
6.
7.
Zr doped ZnO nanoparticles are prepared by the sol-gel method with post-annealing. X-ray diffraction results show that all samples are the typical hexagonal wurtzite structure without any other new phase, as well as the Zr atoms have successfully entered into the ZnO lattices instead of forming other lattices. Magnetic measurements indicate that all the doping samples show room temperature ferromagnetism and the pure ZnO is paramagneism. The results of Raman and X-ray photoelectron spectroscopy indicate that there are a lot of oxygen vacancies in the samples by doping element of Zr. It is considered that the observed ferromagnetism is related to the doping induced oxygen vacancies. 相似文献
8.
《Ceramics International》2017,43(2):1997-2003
The single-phase Ni-doped PbPdO2 films with a body-centered orthorhombic structure were synthesized by the sol-gel spin-coating method and an oxidation treatment. The films with a thickness of about 440 nm were found to have a nanograin structure and large amount of Pb vacancies. The valence states of Ni and Pd ions within the Ni-doped PbPdO2 films were very close to 2+, while the Pb ions exhibited a mixed valence between 2+ and 4+. The existence of Pb vacancies and the low electronegativity of Pb2+ ion resulted in the increase of the valence of Pb ions. The analysis of the magnetic properties indicated that the magnetisms of the single-phase Ni-doped PbPdO2 nanograin films were all composed of the ferromagnetism and the paramagnetism. The ferromagnetism enhanced with the calcination temperature increasing and could be retained up to 380 K. A carrier-mediated mechanism bridged to the bound magnetic polaron model based on the Pb vacancies, the doped Ni ions and the Pb ions with a valence higher than 2+ were used to explain the magnetic origin of these Ni-doped PbPdO2 nanograin films. 相似文献
9.
Abdullah Ameen Saad Hassan Wasi Khan Shahid Husain Pooja Dhiman Mahavir Singh 《International Journal of Applied Ceramic Technology》2020,17(5):2430-2438
In this work, the physical properties of nanocrystalline samples of La0.7Sr0.3Mn1−xFexO3 (0.0 ≤ x ≤ 0.20) perovskite manganites synthesized by the reverse micelle (RM) technique were explored in detail. The phase purity, crystal structure, and crystallite size of the samples were determined using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. All the samples had rhombohedral crystal structure and crystallite size increased with increase in Fe content in La0.7Sr0.3MnO3. The scanning electron micrographs (SEMs) exhibited smooth surface morphology and nonuniform shape of the particles. The optical properties studied using UV-visible absorption spectroscopy revealed a decrease in the absorbance and optical band gap with an increase in Fe content in La0.7Sr0.3MnO3 compound. The temperature-dependent resistivity measurements revealed semiconducting nature of x = 0 and 0.1 samples up to the studied temperature range, while a metal-to-insulator transition was observed at higher Fe doping. Magnetic studies revealed weak ferromagnetism in all the samples and a reduction in the maximum magnetization with an increase in Fe content. A close correlation between electrical transport and magnetic properties was observed with the doping of Fe ion in La0.7Sr0.3MnO3 at Mn site. These results advocate strong interactions associated with the double exchange mechanism among Fe3+ and Mn3+ ions. 相似文献
10.
采用溶胶-凝胶法制备了不同粒径的纯净单相钙钛矿型BiFeO3纳米微粒. X射线衍射分析表明,BiFeO3纳米微粒仍为菱方结构,但晶格畸变随颗粒尺寸的减小而增大. 磁测量显示,BiFeO3纳米微粒具有明显弱铁磁性,且弱铁磁性随温度升高显著降低. 弱铁磁性的自发磁化强度随温度升高呈线性下降,磁化强度和磁化率均随颗粒尺寸的减小而增大. 穆斯堡尔谱分析揭示,颗粒愈小,自旋倾角愈大,其分布也愈宽. 从纳米微粒小尺寸效应和表面效应入手,讨论了BiFeO3纳米微粒结构与磁结构和弱铁磁性的关系. 相似文献