全文获取类型
收费全文 | 5229篇 |
免费 | 371篇 |
国内免费 | 743篇 |
专业分类
化学 | 4725篇 |
晶体学 | 102篇 |
力学 | 38篇 |
综合类 | 17篇 |
数学 | 83篇 |
物理学 | 1378篇 |
出版年
2024年 | 21篇 |
2023年 | 128篇 |
2022年 | 78篇 |
2021年 | 83篇 |
2020年 | 146篇 |
2019年 | 190篇 |
2018年 | 172篇 |
2017年 | 180篇 |
2016年 | 182篇 |
2015年 | 161篇 |
2014年 | 196篇 |
2013年 | 317篇 |
2012年 | 289篇 |
2011年 | 332篇 |
2010年 | 267篇 |
2009年 | 359篇 |
2008年 | 321篇 |
2007年 | 385篇 |
2006年 | 348篇 |
2005年 | 325篇 |
2004年 | 317篇 |
2003年 | 185篇 |
2002年 | 171篇 |
2001年 | 158篇 |
2000年 | 153篇 |
1999年 | 112篇 |
1998年 | 116篇 |
1997年 | 101篇 |
1996年 | 96篇 |
1995年 | 94篇 |
1994年 | 55篇 |
1993年 | 47篇 |
1992年 | 44篇 |
1991年 | 44篇 |
1990年 | 40篇 |
1989年 | 15篇 |
1988年 | 25篇 |
1987年 | 15篇 |
1986年 | 17篇 |
1985年 | 5篇 |
1984年 | 11篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1973年 | 3篇 |
排序方式: 共有6343条查询结果,搜索用时 0 毫秒
101.
对以本征Si及重掺杂p型和n型Si作为中间层的Fe/Si多层膜的层间耦合进行研究,并通过退火,增大Fe,Si之间的扩散,分析界面扩散对层间耦合的影响. 实验结果表明,层状结构良好的制备态的多层膜,Fe,Si之间也存在一定程度的扩散,它是影响层间耦合的 主要因素,远远超过了半导体意义上的重掺杂,使不同种类的Si作为中间层的层间耦合基本 一致.进一步还发现,在一定范围内增大Fe,Si之间的扩散,即使多层膜的层状结构已经有了相当的退化,Fe/Si多层膜的反铁磁耦合强度基本保持不变.
关键词:
Fe/Si多层膜
层间耦合
界面扩散 相似文献
102.
The deformation surrounding Vickers indentations on InGaAsP/InP epilayers have been studied in detail. The surface topography was characterized by using atomic force microscopy (AFM). The material pile-up and sink-in regions around the indentation impression was observed for the quaternary InGaAsP/InP epilayers. The sectional analysis mode of the AFM shows the depth profile at the indented region. Microindentation studies were carried out for different atomic fraction of the quaternary InGaAsP/InP compound semiconductor alloys. The microhardness values of InGaAsP/InP epilayers were found to be in the range of 5.08 and 5.73 GPa. These results show that the hardness value of the quaternary alloy drastically increases as the composition of As was increased by 0.01 atomic fraction and when the phosphorous concentration decreases from 0.4 to 0.38. The reason may be that the increase in As concentration hardens the lattice when phosphorous concentration was less and hardness decreases when phosphorous was increased. 相似文献
103.
Fu Ri Ling Zhi Hong He Jian Quan Yao Baio Wang Shao Ji Jiang 《Optics & Laser Technology》2008,40(7):941-945
A series of near-stoichiometric Zn:Fe:LiNbO3 crystals were grown by the high-temperature top-seed solution growth (HTTSSG) method from stoichiometric melts doped with 6 mol% K2O. Infrared (IR) transmission spectra were measured and discussed in terms of the defect structure of the near-stoichiometric Zn:Fe:LiNbO3 crystals. The results of the transmitted beam pattern distortion method show that the optical damage resistance of the near-stoichiometric Zn:Fe:LiNbO3 crystals increases rapidly when the ZnO concentration exceeds a threshold value. The threshold value concentration of ZnO of the near-stoichiometric Zn:Fe:LiNbO3 crystals is much lower than that of the congruent LiNbO3 crystals. The dependence of the optical damage resistance on the defect structure of the near-stoichiometric Zn:Fe:LiNbO3 crystals are discussed, and the holographic recording properties of the near-stoichiometric Zn:Fe:LiNbO3 crystals are investigated. 相似文献
104.
P. T. Jochym K. Parlinski A. M. Oleś 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(2):173-179
The magnetization distribution, its energetic characterization by the
interlayer coupling constants and lattice dynamics of (001)-oriented
Fe/Pt multilayers are investigated using density functional theory
combined with the direct method to determine phonon frequencies.
It is found that ferromagnetic order between consecutive Fe layers is
favoured, with the enhanced magnetic moments at the
interface. The bilinear and biquadratic coupling coefficients between Fe
layers are shown to saturate fast with increasing thickness of
nonmagnetic Pt layers which separate them. The phonon calculations
demonstrate a rather strong dependence of partial iron phonon
densities of states on the actual position of Fe monolayer
in the multilayer structure. 相似文献
105.
E. Klempt 《The European Physical Journal A - Hadrons and Nuclei》2008,38(2):187-194
The mass spectrum of Δ -resonances is compared to predictions based on three quark-model variants, to predictions assuming
that chiral symmetry is restored in high-mass baryon resonances, and to predictions derived from AdS/QCD. The latter approach
yields a nearly perfect agreement when the confinement property of QCD is modeled by a soft wall in AdS. 相似文献
106.
The present work analyses, in detail, the optimization of a sonochemical process with respect to concentration of precursor and power supplied in a system. This is due to that even a small change in power dramatically changes the high-energy conditions created with the bubble collapse. A model reaction that has been considered for this purpose involves the decomposition of Fe(CO)5 in decalin solvent as this reaction is strongly influenced by the cavitation conditions. Sonochemical treatment of this carbonyl results in the formation of amorphous Fe2O3, which on heat treatment gives nanocrystalline Fe2O3. It has been observed that concentration and power density parameters play an important role to obtain higher decomposition of Fe(CO)5 and hence higher yield of the amorphous Fe2O3 product. Also, using the experimentally observed results, a correlation (polynomial) has been developed. 相似文献
107.
The energy levels, oscillator strengths, spontaneous radiative decay rates, and electron impact collision strengths are calculated for Fe VIII and Fe IX using the recently developed flexible atomic code (FAC). These atomic data are used to analyse the emission spectra of both laboratory and astrophysical plasmas. The nf-3d emission lines have been simulated for Fe VIII and Fe IX in a wavelength range of 6-14 nm. For Fe VIII, the predicted relative intensities of lines are insensitive to temperature. For Fe IX, however, the intensity ratios are very sensitive to temperature, implying that the information of temperature in the experiment can be inferred. Detailed line analyses have also been carried out in a wavelength range of 60-80 nm for Fe VIII, where the solar ultraviolet measurements of emitted radiation spectrometer records a large number of spectra. More lines can be identified with the aid of present atomic data. A complete dataset is available electronically from http://www.astrnomy.csdb.cn/EIE/. 相似文献
108.
Tomomi Kanazawa Kohei Ono Masashi Yamazaki Shiho Cho Fumiyoshi Takano 《Applied Surface Science》2008,254(23):7918-7920
We propose a reactive ion etching (RIE) process of an L10-FePt film which is expected as one of the promising materials for the perpendicular magnetic recording media. The etching was carried out using an inductively coupled plasma (ICP) RIE system and an etching gas combination of CH4/O2/NH3 was employed. The L10-FePt films were deposited on (1 0 0)-oriented MgO substrates using a magnetron sputtering system. The etching masks of Ti were patterned on the FePt films lithographically. The etch rates of ∼16 and ∼0 nm/min were obtained for the FePt film and the Ti mask, respectively. The atomic force microscopy (AFM) analyses provided the average roughness (Ra) value of 0.95 nm for the etched FePt surface, that is, a very flat etched surface was obtained. Those results show that the highly selective RIE process of L10-FePt was successfully realized in the present study. 相似文献
109.
《Physics letters. A》2019,383(30):125920
Based on the topological nature of Chern insulator and magnetoelectric coupling of chiral metamaterial, we investigate the electrodynamics for the interface associated with the two media. The Fresnel coefficients of the interface between Chern insulator and chiral metamaterial, as well as the corresponding polarization rotation angles, are derived. The reflection characteristics of the linearly polarized incident wave at the interface, such as complete polarization conversion and change of polarization state, are discussed. Under the combined influence of Chern insulator and chiral metamaterial, the partial polarization conversion may be enhanced to the complete polarization conversion, and the chiral metamaterial may compensate for the suppression effect of longitudinal conductivity of Chern insulator on the polarization conversion. 相似文献
110.
Absolute one-handed chiral quinoline tetramers andoctamers containing different oxazolylanilines at the C-terminus have been synthesized.The absolute one-handed sense and diastereomeric excess values were valued by^1H NMR.X-ray crystal diffractionand CD studies reveal that the S-oxazolylaniline always induces a P-handed helicity and the absolute helicity is driven by the stable three-center hydrogen bonding between protons in the amide and N atoms in oxazolylaniline and adjacent quinoline ring.CPL investigations demonstrated that S-CQn-a-d are CPL active and its g(lum)values are dependent on its length.Interestingly,the sizes of the substituents in the chiral centers are different,howeve r,they exert no effect on the dissymmetric factors g(abs)and g(lum)of quinoline oligoamide foldamers. 相似文献