全文获取类型
收费全文 | 58篇 |
免费 | 10篇 |
国内免费 | 3篇 |
专业分类
化学 | 9篇 |
晶体学 | 15篇 |
力学 | 25篇 |
综合类 | 3篇 |
数学 | 2篇 |
物理学 | 17篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 1篇 |
2014年 | 1篇 |
2013年 | 3篇 |
2012年 | 1篇 |
2011年 | 4篇 |
2009年 | 3篇 |
2008年 | 2篇 |
2007年 | 6篇 |
2006年 | 9篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2002年 | 1篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 5篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1993年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
排序方式: 共有71条查询结果,搜索用时 15 毫秒
41.
42.
采用固相反应法制备了六方纤锌矿结构Zn1-xAlxO(0≤x≤0.03)系列多晶,探究了Al掺杂对ZnO多晶的微观形貌和热电输运性质的影响.结果表明,Al掺杂促使ZnO晶粒长大联结,晶界减少,x>0.003时出现在晶界分布的ZnAl2O4尖晶石相.掺杂后样品由ZnO的半导体行为转变为电阻率显著下降的金属行为,且x=0.003有最小的室温电阻率~1.7 mΩ·cm,主要由于掺杂使样品载流子浓度和迁移率显著提高,x=0.003时载流子浓度和迁移率为最高,分别为1.05×1021 cm-3和20 cm2/V·s;300 ~900 K下掺杂样品热电势的绝对值和功率因子均随温度升高而增大,x =0.003时有最大的室温功率因子~0.4mW/m·K2.综合得到ZnO中Al掺杂的饱和固溶度x≈0.003. 相似文献
43.
A. P. Okonechnikov I. N. Kassandrov V. M. Lifenko V. A. Pan''ko 《Journal of Applied Spectroscopy》2001,68(4):637-641
The optical absorption induced by the photosensitive centers formed upon electron irradiation (E = 5 MeV, = 1.7·1018 cm–2) of polycrystalline ZnSe has been studied. A comparison of the optical properties of the irradiated crystals with the known data for ZnS has allowed the assumption that the 496–, 563–, and 652–nm bands in ZnSe are associated with the anion vacancies being in different charge states. The ratio between the concentrations of the optical absorption centers in the crystals photoexcited at 80 K is determined by the electron traps participating in the processes of charge exchange of the vacancies. 相似文献
44.
Relationship between Electrical Activity and Grain Boundary Structural Configuration in Polycrystalline Silicon 总被引:1,自引:0,他引:1
Zhan-Jie Wang Sadahiro Tsurekawa Kenji Ikeda Takashi Sekiguchi Tadao Watanabe 《Interface Science》1999,7(2):197-205
Temperature dependent electron beam induced current (EBIC) technique has been applied to investigate the electrical activities of grain boundaries (GBs) in polycrystalline silicon. The GB character, misorientation and orientation of GB plane, were analyzed using a FE-SEM/EBSP/OIM system prior to the EBIC measurements. The EBIC contrasts were found to depend on GB character; low GBs showed weak contrasts compared with general GBs at any temperatures, and also demonstrated to vary at GB irregularities such as boundary steps. These results indicate that electrical properties depend on the orientation of the GB plane as well as the misorientation. On the other hand, there existed less differences in temperature dependence of EBIC contrast irrespective of GB characters. The EBIC contrast decreased with increasing temperature, showed a minimum around 250 K, then increased again with further increasing temperature. The resulting temperature dependence of EBIC contrast probably comes from the combination of two types of recombination processes of carriers. One is related to a shallow level associated with an inherent GB structure, though the exact energy levels also would probably depend on GB structures, and the other to a deep level associated with impurities segregated at GBs, which acts as recombination center. 相似文献
45.
46.
B. Jiang 《Journal of the mechanics and physics of solids》2004,52(5):1125-1149
Inspired by recent molecular dynamic simulations of nanocrystalline solids, a generalized self-consistent polycrystal model is proposed to study the transition of yield strength of polycrystalline metals as the grain size decreases from the traditional coarse grain to the nanometer scale. These atomic simulations revealed that a significant portion of atoms resides in the grain boundaries and the plastic flow of the grain-boundary region is responsible for the unique characteristics displayed by such materials. The proposed model takes each oriented grain and its immediate grain boundary to form a pair, which in turn is embedded in the infinite effective medium with a property representing the orientational average of all these pairs. We make use of the linear comparison composite to determine the nonlinear behavior of the nanocrystalline polycrystal through the concept of secant moduli. To this end an auxiliary problem of Christensen and Lo (J. Mech. Phys. Solids 27 (1979) 315) superimposed on the eigenstrain field of Luo and Weng (Mech. Mater. 6 (1987) 347) is first considered, and then the nonlinear elastoplastic polycrystal problem is addressed. The plastic flow of each grain is calculated from its crystallographic slips, but the plastic behavior of the grain-boundary phase is modeled as that of an amorphous material. The calculated yield stress for Cu is found to follow the classic Hall-Petch relation initially, but as the gain size decreases it begins to depart from it. The yield strength eventually attains a maximum at a critical grain size and then the Hall-Petch slope turns negative in the nano-range. It is also found that, when the Hall-Petch relation is observed, the plastic behavior of the polycrystal is governed by crystallographic slips in the grains, but when the slope is negative it is governed by the grain boundaries. During the transition both grains and grain boundaries contribute competitively. 相似文献
47.
A micromechanics-based finite element model for the constitutive behavior of polycrystalline ferromagnets is developed. In the model, the polycrystalline solid is assumed to comprise numerous single crystals with randomly distributed crystallographic orientations, and the single crystals, in turn, consist of ferromagnetic domains, each of which is represented by a cubic element. The dipole directions of the domains are randomly assigned to simulate the crystallographic nature of ferromagnetic polycrystals. A switching criterion for the domains is specified at the microscopic level. The macroscopic constitutive behavior is obtained by averaging the microscopic/local behavior of each domain. The developed model has been applied to the simulation of a ferromagnetic material. With appropriate material parameters adopted, hysteresis loops of the predicted magnetic induction versus magnetic field and those of the strain versus magnetic field are shown to agree well with experimental observations.The project supported by the National Natural Science Foundation of China (90205030, 10472088, 10425210), the National Basic Research Program of China (2006CB601202) and the State Administration of the Foreign Experts Affairs Through the “111” Project (B06024) The English text was polished by Yunming Chen. 相似文献
48.
49.
50.
以柠檬酸为燃烧剂,掺杂摩尔分数为2%的Ho3+,采用低温燃烧法制备Ho∶YbGG多晶粉体。通过对样品的X射线衍射和扫描电镜分析,确定最佳煅烧温度为900℃。样品的吸收光谱在536 nm和645 nm处出现较强吸收峰,分别对应Ho3+的5I8→5F4(5S2)和5I8→5F5能级跃迁;在940 nm和982 nm处出现强吸收谱带,对应于Yb3+的2F7/2→2F5/2能级跃迁。样品的荧光光谱在1 989 nm处有强发射谱带,对应于Ho3+的5I7→5I8能级跃迁。样品可以发出较强的上转换绿光和红光,分别对应于Ho3+的5F4(5S2)→5I8和5F5→5I8能级跃迁。对相应的上转换机制也进行了分析。 相似文献