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61.
M. Miglierini 《Hyperfine Interactions》2005,164(1-4):41-49
A controlled annealing of amorphous precursors represents a simple way of obtaining nanocrystalline alloys featuring interesting magnetic properties suitable for technical applications. They stem from the presence of crystalline nanograins embedded in the amorphous residual matrix which determine the resulting macroscopic parameters. In order to understand correlation between the microstructure and the resulting magnetic behaviour, Mössbauer spectrometry is used as a method of local probe analysis. Possibilities of this technique are discussed and representative examples of investigation of NANOPERM-type nanocrystalline alloys are provided. 相似文献
62.
A.M. Vichare D.G. Kanhere 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(1):89-94
Density based molecular dynamics has been used to investigate the ground state structures of heterogeneous binary clusters
Al13Lin, n
= 1, 2, 3, 4, 10, 19, 20, 21. Some of these structures have also been investigated by full Kohn-Sham based calculations. Our
earlier investigations have shown that in the Al-Li cluster, the ground state configurations are the ones where the Al atoms
form a core around which the Li atoms form a “cage”. In the present work, we have chosen the well-known Al13 icosahedron as the surface over which we study the evolution of the surface coverage as the number of Li atoms increases.
On the basis of the earlier work, we expect that the Al13Li20 cluster would be the most stable and indeed our simulations do yield such a novel fivefold symmetric stable structure formed
out of purely metal atoms. This icosahedral substrate is also used to study the coverage of the aluminum surface by lithium
atoms. For a small number of Li atoms, these studies suggest that the Li-Li dimerisation is not particularly favored.
Received: 24 October 1997 / Revised: 7 April 1998 / Accepted: 29 June 1998 相似文献
63.
64.
Shiyong Liu Xiangbo Zeng Wenbo Peng Haibo Xiao Wenjie Yao Xiaobing Xie Chao Wang Zhanguo Wang 《Journal of Non》2011,357(1):121-125
We develop a double-layer p-type hydrogenated nanocrystalline silicon (p-nc-Si:H) structure consisting of a low hydrogen diluted i/p buffer layer and a high hydrogen diluted p-layer to improve the hydrogenated amorphous silicon (a-Si:H) n-i-p solar cells. The electrical, optical and structural properties of p-nc-Si:H films with different hydrogen dilution ratio (RH) are investigated. High conductivity, low activation energy and wide band gap are achieved for the thin films. Raman spectroscopy and high-resolution transmission electron microscopy (HRTEM) analyses indicate that the thin films contain nanocrystallites with grain size around 3-5 nm embedded in the amorphous silicon matrix. By inserting a p-nc-Si:H buffer layer at the i/p interface, the overall performance of the solar cell is improved significantly compared to the bufferless cell. The improvement is correlated with the reduction of the density of defect states at the i/p interface. 相似文献
65.
66.
采用自悬浮定向流法制备纳米Ni粉体,利用放电等离子烧结技术制备出了直径10 mm、厚2 mm,致密度为96.8 %,显微硬度为4.17 GPa的纳米块体材料。用X射线衍射仪、扫描电子显微镜和显微硬度计分析了烧结块体样品的相组成、晶粒尺寸、微观形貌和显微硬度。研究表明:随烧结温度的升高,块体样品的致密度和晶粒尺寸增大,当烧结温度为650 ℃时,致密度最高,晶粒尺寸为44.8 nm;显微硬度随烧结温度的增高先增大后减小,当烧结温度为550 ℃时,显微硬度最大为4.33 GPa;较高烧结温度下,断口微观形貌的纳米级韧窝出现,显示了韧性断裂的特征。 相似文献
67.
The magnetization reversal behaviour for SmCo6.8Zr0.2 and SmCo6.8Zr0.2/α-(Fe,Co) nanocrystalline magnets at low temperature 下载免费PDF全文
This paper reports that the SmCo 6.8 Zr 0.2 nanocrystalline permanent magnets and SmCo 6.8 Zr 0.2 /α-(Fe,Co) nanocomposite permanent magnets are successfully produced by mechanical alloying and subsequently annealing at 700 C for 10 minutes.The x-ray diffraction results show that the phase structure of SmCo 6.8 Zr 0.2 nanocrystalline permanent magnets is composed of SmCo 7 phase and SmCo 6.8 Zr 0.2 /α-(Fe,Co) nanocomposite permanent magnets is composed of SmCo 7 and α-(Fe,Co) phases.The mechanism of magnetization reversal is mainly controlled by inhomogeneous domain wall pinning in SmCo 6.8 Zr 0.2 and SmCo 6.8 Zr 0.2 /α-(Fe,Co) magnets.The inter-grain exchange interaction at low temperature is investigated,which shows that the inter-grain exchange interaction of SmCo 6.8 Zr 0.2 /α-(Fe,Co) magnets increases greatly by the decrease of the measured temperature.According to Δm irr-H/H cj,Δm rev-H/H cj and χ irr-H/H cj curves at room temperature and 100 K,the changes of irreversible and reversible magnetization behaviours of SmCo 6.8 Zr 0.2 and SmCo 6.8 Zr 0.2 /α-(Fe,Co) magnets with the decreasing temperature are analysed in detail.The magnetic viscosity and the activation volume of SmCo 6.8 Zr 0.2 and SmCo 6.8 Zr 0.2 /α-(Fe,Co) magnets at different temperatures are also studied. 相似文献
68.
The circular permeability μ′=μ′−jμ″ of two Fe-based soft magnetic wires with axial and transverse domains, has been determined from the measurements of impedance Z=R+jX as functions of frequency (f=10-105 Hz) and AC current amplitude (I=0.1-100 mA). From the magnetic spectra of μ′−f and μ″−f for a few circular fields (Hφ=0.4, 1.2, 4, 12, 40 A/m), we found that the sample with axial domain structure exhibits a relaxational feature, while for the one with transverse domain resonance-like spectra were observed when the circular field Hφ≥4 A/m. These results have been discussed in terms of domain structure and circular magnetization processes. 相似文献
69.
Voronoi tessellation has been used widely to approximate and model various cellular structures and stochastic patterns appearing in nature. In this work, we present an extended version of the Voronoi tessellation method that partitions the space with certain constraints commonly encountered in either experimental measurements or theoretical models, such as cell volume or size distribution. The new Voronoi method is implemented using an inverse Monte Carlo method. We calculate the topological and statistical properties of tessellated Voronoi cells in several model systems with cell volumes obeying lognormal and bimodal distributions. We also compare the results with those obtained using the conventional Poisson–Voronoi method. We observed systematic changes in the topological properties as well as deviations from some established topological relations as the parameters in the constraint were varied. The application of this constrained Voronoi method in microstructure modelling and characterization in poly- and nano-crystalline materials is briefly discussed. 相似文献
70.
PbS nanocrystalline thin film was prepared by chemical bath deposition on Si(1?0?0) substrate at bath temperatures of 25, 45 and 65 °C. Triethanolamine was added to the aqueous solution, which decreased the grain size and increased the luminescence of the nanocrystalline PbS thin film. PbS nanocrystals were identified using XRD, TEM and AFM. The crystalline size of the PbS film deposited at different bath temperatures was estimated by XRD and TEM to be 7–12 nm. The growth mechanism of the PbS crystallites were described at different bath temperatures. The confinement was reflected in the absorption spectra, photoluminescence excitation and photoluminescence spectra. The luminescence of Si(1?0?0) substrate and PbS nanocrystalline film deposited on Si(1?0?0) were compared, and the results revealed that the PbS nanocrystals altered and notably enhanced the emission features of the Si(1?0?0) substrate. The shifting of the maximum photoluminescence emission wavelength of PbS nanocrystals with a change in bath temperature and the variation in photoluminescent intensity of PbS nanocrystals prepared at 25 °C versus deposition time were investigated. A single-peak fit of a Gaussian function was employed to discern the photoluminescence of PbS on Si(1?0?0) substrate. 相似文献