全文获取类型
收费全文 | 206篇 |
免费 | 50篇 |
国内免费 | 5篇 |
专业分类
化学 | 31篇 |
晶体学 | 5篇 |
力学 | 5篇 |
综合类 | 4篇 |
数学 | 4篇 |
物理学 | 212篇 |
出版年
2022年 | 1篇 |
2020年 | 5篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2015年 | 2篇 |
2014年 | 13篇 |
2013年 | 29篇 |
2012年 | 14篇 |
2011年 | 24篇 |
2010年 | 19篇 |
2009年 | 6篇 |
2008年 | 16篇 |
2007年 | 16篇 |
2006年 | 23篇 |
2005年 | 7篇 |
2004年 | 9篇 |
2003年 | 15篇 |
2002年 | 6篇 |
2001年 | 7篇 |
2000年 | 12篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有261条查询结果,搜索用时 31 毫秒
141.
Backscattering coefficients for electrons normally impinging on Si, Ge, GaN, GaAs and InSb targets have been calculated by using the Vicanek and Urbassek theory [M. Vicanek, H.M. Urbassek, Phys. Rev. B 44 (1991) 7234] for incident energies ≤5 keV. Electron range has been calculated from various semi-empirical analytical expressions. The cross-sections used to describe the electron transport are determined via the appropriate analytical expression given by Jablonski [A. Jablonski, Phys. Rev. B 58 (1998) 16470] whose new improved version has been recently reported by Rouabah et al. [Z. Rouabah, N. Bouarissa, C. Champion, N. Bouaouadja, Appl. Surf. Sci. 255 (2009) 6217]. The results may be seen as the first predictions for low-energy electron backscattering coefficients impinging on GaN, GaAs and InSb semiconductors. The models used in the calculation of the electron range affect both the accuracy and behaviour of the electron backscattering coefficients. 相似文献
142.
143.
Plasma induced sputtering yield and backscattering for ITER-relevant materials as calculated by TRIM
In this paper, we report an analytical model to estimate the variation of the yield (and hence the pressure) from sputtering, elastic collisions, and backscattering on a surface exposed to International Thermonuclear Experimental Reactor-relevant plasmas. To study the yield and the pressure exerted on the surfaces of carbon (C), silicon (Si) and tungsten (W) due to plasma exposure, the irradiation of H, Ar and Xe ions at normal incidence was considered. Transport and range of ions in matter simulations were done to calculate the backscattering/sputtering yields and the energies on the surfaces. The calculations are significant for the optimization of material facing the plasma in future fusion reactors where erosion and long term operation are key issues. The results show that yield increases with the increase of ion energy. The carbon surface is the least affected to exposure of the plasma. In the chosen ion energy range (0–1?keV), the simulations/calculations (for Ar ion incident on Si and W) are in good agreement with published experimental results. 相似文献
144.
采用金属有机化合物气相淀积法在(0001)取向的蓝宝石衬底上生长一层 大约20 nm厚的AlN缓冲层, 在缓冲层上生长大约2 μm厚、 晶体质量良好的AlxGa1-xN外延层, 通过深紫外光致发光法测量发光峰的能量Eg 判断外延层中铝含量的均匀性, 取样品均匀性良好的氮铝镓外延片进行卢瑟福背散射(RBS)实验, 通过两个高能离子束实验室分别进行RBS随机谱分析, 每个实验室测量六个样品, 由分析软件拟合随机谱获得外延层中的xAl. 并对样品的均匀性、堆积校准、计数统计、散射角、离子束能量与阻止截面 等影响测量结果准确性的不确定度来源进行分析. 结果表明, 采用入射离子4He, 能量为2000 keV, 散射角为165° 时, 氮铝镓外延片中铝含量(x=0.8) 的测量不确定度为2.0%, 包含扩展因子k=2.
关键词:
氮铝镓
卢瑟福背散射
测量不确定度
金属有机化合物气相淀积法 相似文献
145.
利用卢瑟夫背散射/沟道技术和金属有机化学气相沉积方法, 对蓝宝石衬底上 在不同温度、压强下生长的Ga2+xO3-x薄膜进行结构和结晶品质的测量与分析; 并结合高分辨X射线衍射分析技术, 通过对其对称(402)面的θ–2θ及ω扫描, 确定了其结构类型及结晶品质. 实验表明: 在相同的生长温度(500 ℃)下, 结晶品质随压强的下降而变好, 生长压强为15 Torr (1 Torr=133.322 Pa)的样品其结晶品质最好, 沿轴入射之比χmin值为14.5%; 在相同的生长压强(15 Torr)下, 结晶品质受生长温度的影响不大, 所以, 生长温度不是改变结晶品质的主要因素; 此外, 在相同的生长条件下制备的样品, 分别经过700, 800和900 ℃退火后, 其结晶品质随退火温度的变化而变化. 退火温度为800 ℃的样品的结晶品质最好, χmin值为11.1%; 当退火温度达到900 ℃时, 样品部分分解; 经热处理的样品其X射线衍射谱中有一个强的Ga2O3 (402)面衍射峰, 其半峰全宽为0.5°, 表明该Ga2O3外延膜是(402)择优取向.
关键词:
氧化镓
卢瑟夫背散射
X射线衍射
结晶品质 相似文献
146.
A. Cecal 《Isotopes in environmental and health studies》2013,49(1):4-6
Es wird eine schnelle und einfache Methode zur quantitativen Bestimmung der Komponenten eines ternären Systems beschrieben. Sie beruht auf der kombinierten Messung der Rückstreuung und Absorption von β-Strahlung. Als Beispiel wurde das System Na+, Ba2+, Cu2+ gewählt. Der Meβfehler der Methode liegt zwischen 0,5 und 3,5%. 相似文献
147.
Ferromagnetism is induced in pure TiO2 single crystals by oxygen ion irradiation. The ferro-magnetism is observed up to room temperature and is with weak temperature dependence. By combining X-ray diffraction, Rutherford backscattering/channelling, Raman scattering, and electron-spin resonance spectroscopy, supperconducting quantum interference device, displacement per atom, we measured the lattice damage accumulation with increasing flu-ences. A defect complex, i.e., Ti3+ on the substitutional accompanied by oxygen vacancies, has been identified in the irradiated TiO2. This kind of defect complex results in a local (TiO6-x) stretching Raman mode. We elucidate that Ti3+ with one unpaired 3d electron provide the local magnetic moments. 相似文献
148.
用革兰氏阳性金黄色葡萄球菌和革兰氏阴性大肠杆菌,研究了铜离子注入医用热解碳后的抗菌性能.铜离子注入能量为70keV,注入剂量为5×1014~1×1018ion·cm-2.抗菌实验结果表明,铜离子注入样品后对金黄色葡萄球菌和大肠杆菌均具有良好的抗菌效果;抗菌率随注入剂量的增加而提高,在注入剂量接近饱和剂量1×1018ion·cm-2时,抗菌率达到100%.应用卢瑟福背散射(RBS)分析技术,分析了热解碳中铜离子的分布,并初步探讨了铜离子的抗菌机理. 相似文献
149.
To study the electromagnetic (EM) backscatter
characteristics of freak waves at moderate incidence angles, we
establish an EM backscattering model for freak waves in
(1+1)-dimensional deep water. The nonlinear interaction between
freak waves and Bragg short waves is considered to be the basic
hydrodynamic spectra modulation mechanism in the model. Numerical
results suggest that the EM backscattering intensities of freak
waves are less than those from the background sea surface at
moderate incidence angles. The normalised radar cross sections
(NRCSs) from freak waves are highly polarisation dependent, even at
low incidence angles, which is different from the situation for
normal sea waves; moreover, the NRCS of freak waves is more
polarisation dependent than the background sea surface. NRCS
discrepancies between freak waves and the background sea surface
with using horizontal transmitting horizomtal (HH) polarisation are
larger than those with using vertical transmitting vertical (VV)
polarisation, at moderate incident angles. NRCS discrepancies
between freak waves and background sea surface decreases with the
increase of incidence angle, in both HH and VV polarisation radars.
As an application, in the synthetic-aperture radar (SAR) imaging of
freak waves, we suggest that freak waves should have extremely low
backscatter NRCSs for the freak wave facet with the strongest slope.
Compared with the background sea surface, the freak waves should be
darker in HH polarisation echo images than in VV echo images, in SAR
images. Freak waves can be more easily detected from the background
sea surface in HH polarisation images than in VV polarisation
images. The possibility of detection of freak waves at low incidence
angles is much higher than at high incidence angles. 相似文献
150.
针对弱非线性的Longuet-Higgins模型在模拟强非线性畸形波海面时所存在的问题,采用修正的相位调制法模拟一维畸形波时间、空间波面,该方法能够实现畸形波的定时定点生成,并且其波形既能保持目标谱的频谱结构,又能较大程度地满足波浪序列的统计特性.同时,基于改进的双尺度(TSM)法及时域有限差分法建立畸形波的电磁散射模型,经过相对平均偏差和均方根偏差误差分析后,基于TSM法研究分析了畸形波及其背景海面波的归一化雷达散射截面(NRCS)的计算结果.实验表明,合成孔径雷达成像中畸形波的NRCS比背景波要小,即畸形波的合成孔径雷达图像成像比背景波要灰暗,因此可以将NRCS作为畸形波的特征识别标识.通过分析研究不同极化方式、入射角、入射频率条件下畸形波与背景波面的电磁散射特性实验数据得出:当二者的NRCS差值大于-11.8 dB及以上时,即认为产生畸形波,这为实际的工程应用提供了参照标准. 相似文献