全文获取类型
收费全文 | 201篇 |
免费 | 158篇 |
国内免费 | 139篇 |
专业分类
化学 | 214篇 |
晶体学 | 2篇 |
力学 | 4篇 |
数学 | 15篇 |
物理学 | 263篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 5篇 |
2020年 | 4篇 |
2019年 | 4篇 |
2018年 | 2篇 |
2017年 | 16篇 |
2016年 | 7篇 |
2015年 | 10篇 |
2014年 | 21篇 |
2013年 | 23篇 |
2012年 | 34篇 |
2011年 | 36篇 |
2010年 | 34篇 |
2009年 | 32篇 |
2008年 | 43篇 |
2007年 | 42篇 |
2006年 | 42篇 |
2005年 | 32篇 |
2004年 | 25篇 |
2003年 | 16篇 |
2002年 | 11篇 |
2001年 | 2篇 |
2000年 | 15篇 |
1999年 | 14篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
排序方式: 共有498条查询结果,搜索用时 15 毫秒
1.
Quantum State Transfer between Two Distant Atoms by Connecting Two Cavities via Optical Fibres 下载免费PDF全文
A scheme is proposed to unconditionally implement state transfer between two distant atoms by sending the atoms across two distant cavities connected via an optical fibre, respectively. The field state, which preserves the information about the first atom, is transmitted from one cavity to the other along the fibre. A Faraday rotator integrated in the fibre can be designed to completely stop the fields reflected from the second cavity, thus after the field interacts with the second atom for a defined time, the state transfer can be accomplished with unit efficiency. 相似文献
2.
采用溶胶-凝胶法在Pt/Ti/SiO2/Si衬底上制备了不同La掺杂浓度PLZT(x/40/60)薄膜- x射线衍射分析表明制备的PLZT(x/40/60)薄膜是具有单一钙钛矿结构的多晶薄膜- 通过红外椭圆偏振光谱仪测量了波长为2-5—12-6μm范围内PLZT薄膜的椭偏光谱,采用经典色 散模型拟合获得PLZT薄膜的红外光学常数,同时也拟合获得PLZT薄膜的厚度- 随着La掺杂浓 度的增大,折射率逐渐减小- 而消光系数除PLZT(4/40/60)薄膜外,呈现逐渐增大的趋势- 分析表明这些差异主要与PLZ
关键词:
PLZT薄膜
红外光学性质
红外椭圆偏振光谱 相似文献
3.
提出了由中间为高电导率的非铁磁性金属丝外面包裹一层铁磁材料组成的复合结构丝的电流 密度分布和巨磁阻抗(GMI)效应模型,并对Cu/FeCoNi复合丝进行了数值模拟. 结果表明:在 相同的磁性材料几何尺寸和磁特性时,Cu/FeCoNi复合丝铁磁层内的电流随频率的升高比匀 质FeCoNi铁磁丝内的电流更趋于表面分布,而且开始出现趋肤效应时对应的频率明显降低. 当在比较低的频率下就可以观察到明显的MI变化时,复合结构丝中的电阻和电抗变化主要是 由趋肤效应引起,趋肤效应仍然是引起复合结构材料(包括多层薄膜结构)
关键词:
电流密度
巨磁阻抗效应
趋肤效应 相似文献
4.
5.
A Triton X-100-4.0G-D (4.0G-D refers to a 4.0-generation dendrimer) was brought forward as a new phosphorescence labeling reagent. Two types of specific affinity adsorption (AA) reactions (direct method and sandwich method) were carried out between the labeling product of Triton X-100-4:0G-D-Wheat germ agglutinin (WGA) and alkaline phosphatase (ALP), the product of AA reaction preserved the good characteristics of room temperature phosphorescence (RTP) of 4.0G-D and △Ip of the product was proportional to the content of ALP. According to the fact stated above, a new method for the determination of trace ALP by affinity adsorption solid substrate-room temperature phosphorimetry (AA-SS-RTP) was established on the basis of WGA labeled with the Triton X-100-4.0G-D. The detection limits were 0.20 ag·spot^-1 (corresponding concentration: 5.0×10^-16 g·mL^-1, namely 5.0×10^-18 mol·L^-1) for a direct method and 0.14 ag·spot^-1 (corresponding concentration: 3.5×10^-16 g·mL^-1, namely 3.5×10^-18 mol·L^-1) for a sandwich method, respectively. For their high sensitivity, good repeatability and high accuracy, the direct method and sandwich method have been successfully appfied to determine the content of ALP in human serum, and the results were coincided with the clinical detection results of the enzyme-linked immunosorbent assay method by the Zhangzhou Hospital of Traditional Chinese Medicine. Meanwhile, the mechanism for the determination of trace ALP by AA-SS-RTP was discussed. 相似文献
6.
7.
Ferrocene with planar chirality are of increasing importance in the synthesis of chiral ligands used in asymmetric catalysis and asymmetric synthesis.[1~3] To prepare Ugi type of chiral base, the most common method is the resolution of rac-N,N-dimethyl- 1-ferrocenylethylamine (1). 相似文献
8.
Synthesis and characterization of the ligand, [2-tetradecyl-3,6,9-tris(carboxymethyl)-3,6,9-triazaundecan-1,11-dioic acid, H5L] and its Gd(Ⅲ) chelate are described. Protonation constants for H5L (lgKiH = 10.80, 8.40, 4.30, 2.80, 2.15) and the stability constant for GdL2- (lgKGdL2-= 22.75) were determined by potentiometric titration and are similar with the related values of DTPA and Gd-DTPA respectively. The results obtained show that the basicity of the ligand and the stability constant of its Gd(Ⅲ) chelate are not obviously altered after introduction of a linear chain tetradecyl group at the terminal acetic acid residue of DTPA. 相似文献
9.
Solvation interaction and ion association in solutions of lithium perchlorate/4-methoxymethyl-ethylene carbonate (MEC) have been studied by using Infrared and Raman spectra as a function of concentration of lithium perchlorate. The splitting of ring deformation band and ring ether asymmetric stretching band, and the change of carbonyl stretching band suggest that there should be a strong interaction between Li^+ and the solvent molecules, and the site of solvation should be the oxygen atom of carbonyl group. The apparent solvation number of Li^+ was calculated by using band fitting technique. The solvation number was decreased from 3.3 to 1.1 with increasing the concentration of LiClO4/MEC solutions. On the other hand, the band fitting for the ClO4^- band revealed the presence of contact ion pair, and free ClO4^- anion in the concentrated solutions. 相似文献
10.
Simulation of near-infrared photodiode detectors based on β-FeSi_2/4H-SiC heterojunctions 总被引:1,自引:0,他引:1 下载免费PDF全文
In this paper,we propose a near-infrared p-type β-FeSi2/n-type 4H-SiC heterojunction photodetector with semiconducting silicide(β-FeSi2) as the active region for the first time.The optoelectronic characteristics of the photodetector are simulated using a commercial simulator at room temperature.The results show that the photodetector has a good rectifying character and a good response to near-infrared light.Interface states should be minimized to obtain a lower reverse leakage current.The response spectrum of the β-FeSi2/4H-SiC detector,which consists of a p-type β-FeSi2 absorption layer with a doping concentration of 1×1015cm-3 and a thickness of 2.5 μm,has a peak of 755 mA/W at 1.42 μm.The illumination of the SiC side obtains a higher responsivity than that of the β-FeSi2 side.The results illustrate that the β-FeSi2/4H-SiC heterojunction can be used as a near-infrared photodetector compatible with near-infrared optically-activated SiC-based power switching devices. 相似文献