全文获取类型
收费全文 | 301篇 |
免费 | 1篇 |
国内免费 | 37篇 |
专业分类
化学 | 188篇 |
晶体学 | 6篇 |
力学 | 1篇 |
物理学 | 144篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 5篇 |
2020年 | 8篇 |
2019年 | 4篇 |
2018年 | 4篇 |
2017年 | 1篇 |
2016年 | 5篇 |
2015年 | 10篇 |
2014年 | 4篇 |
2013年 | 14篇 |
2012年 | 21篇 |
2011年 | 28篇 |
2010年 | 19篇 |
2009年 | 31篇 |
2008年 | 26篇 |
2007年 | 20篇 |
2006年 | 21篇 |
2005年 | 20篇 |
2004年 | 21篇 |
2003年 | 9篇 |
2002年 | 3篇 |
2001年 | 8篇 |
2000年 | 3篇 |
1999年 | 9篇 |
1998年 | 10篇 |
1997年 | 6篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有339条查询结果,搜索用时 474 毫秒
331.
Rosemary S. Barker 《Journal of solid state chemistry》2006,179(6):1918-1923
A new neodymium molybdate, Nd6Mo10O39, has been identified in the Nd2O3-MoO3 phase system. Nd6Mo10O39 appears to be a metastable phase, which does not form directly from a stoichiometric mixture of Nd2O3 and MoO3 oxides. Instead, it can be obtained by thermal decomposition of Nd2Mo4O15. Nd2Mo4O15 usually decomposes into Nd2(MoO4)3, and the formation of Nd6Mo10O39 critically depends on the heating regime used.The structure of Nd6Mo10O39 has been determined by single crystal X-ray diffraction. It crystallizes in the monoclinic space group C2/c, with unit cell parameters of , , , β=100.767(2)°, at 120 K. Nd atoms are seven and eight coordinate, and pairs of coordination polyhedra share edges and faces, respectively, to form Nd2O12 and Nd2O13 groups. All Mo atoms are in tetrahedral coordination environments, with some of the tetrahedra sharing corners to form pyromolybdate groups. 相似文献
332.
C. Napierala C. Lepoittevin L. Sauques P. Laffez 《Journal of solid state chemistry》2010,183(7):1663-1669
Rare earth nickelates exhibit a reversible metal-semiconductor phase transition that is, in the infrared range, responsible for a thermo-optical contrast. The state of the art synthesis of these compounds usually requires high oxygen pressure to stabilize Ni in the oxidation state 3+. In this work, using polymeric precursor associated with moderate pressure annealing, we show that it is possible to obtain fully oxidized rare earth nickelate with metal-insulator transition. Using thermogravimetric analysis, X-ray diffraction and transmission electronic microscopy we compare different samples synthesized at different oxygen pressures and demonstrate their structural similarity. Thermo-optical properties were measured, in the infrared range, using reflectance measurements and confirmed the metal-insulator transition at 60 °C in both samples.TEM observations lead to the conclusion that the structure commonly obtained at 175 bar is perfectly observed in the 20 bar sample without major structural defects. The two samples exhibit a thermochromic behavior and thermo-optical properties of the two samples are equivalent. 相似文献
333.
Vladimir G. Zubkov Ivan I. Leonidov Alexander P. Tyutyunnik Ludmila L. Surat Marina A. Melkozerova Elena V. Zabolotskaya Dina G. Kellerman 《Journal of solid state chemistry》2010,183(5):1186-1346
The crystal structure of the promising optical materials Ln2M2+Ge4O12, where Ln=rare-earth element or Y; M=Ca, Mn, Zn and their solid solutions has been studied in detail. The tendency of rare-earth elements to occupy six- or eight-coordinated sites upon iso- and heterovalent substitution has been studied for the Y2−xErxCaGe4O12 (x=0-2), Y2−2xCexCa1+xGe4O12 (x=0-1), Y2Ca1−xMnxGe4O12 (x=0-1) and Y2−xPrxMnGe4O12 (x=0-0.5) solid solutions. A complex heterovalent state of Eu and Mn in Eu2MnGe4O12 has been found. 相似文献
334.
335.
Dapeng Wang Narayan Poudyal Chuanbing Rong Ying Zhang M.J. Kramer J. Ping Liu 《Journal of magnetism and magnetic materials》2012
Nanoscale hybrid magnets containing SmCo5 and Nd2Fe14B hard magnetic phases have been produced via a novel “in-one-pot” processing route. The grain size of the processed bulk composite materials is controlled below 20 nm. The refinement of the nanoscale morphology leads to effective inter-phase exchange coupling that results in single-phase like magnetic properties. Energy product of 14 MGOe was obtained in the isotropic nanocomposite magnets at room temperature. At elevated temperatures, the hybrid magnets have greatly improved thermal stability compared to the Nd2Fe14B single-phase counterpart and have substantially increased magnetization and energy products compared to the single-phase SmCo5 counterpart. 相似文献
336.
B.J. Ruck F. Natali N.O.V. Plank Binh Do Le M. Azeem Maha Alfheid C. Meyer H.J. Trodahl 《Physica B: Condensed Matter》2012,407(15):2954-2956
The rare-earth nitrides are ferromagnetic semiconductors with promise for spintronic devices. Their most common dopants are nitrogen vacancies (VN), with a small enough energy of formation that they exist at of order 1% in epitaxial films. Here we report preliminary investigations of their effect on the magnetic states of two of them in the series, GdN and EuN. In the former we find an enhanced Curie temperature at very high VN concentration, and the Eu2+ ions associated with VN in the latter show strong exchange with their Eu3+ neighbours that might form the basis of a diluted magnetic semiconductor. 相似文献
337.
Guohua Zhong Kang Zhang Fan HeXuhang Ma Lanlan LuZhuang Liu Chunlei Yang 《Physica B: Condensed Matter》2012,407(18):3818-3827
Because of their possible applications in spintronic and optoelectronic devices, GaN dilute magnetic semiconductors (DMSs) doped by rare-earth (RE) elements have attracted much attention since the high Curie temperature was obtained in RE-doped GaN DMSs and a colossal magnetic moment was observed in the Gd-doped GaN thin film. We have systemically studied the GaN DMSs doped by RE elements (La, Ce–Yb) using the full-potential linearized augmented plane wave method within the framework of density functional theory and adding the considerations of the electronic correlation and the spin-orbital coupling effects. We have studied the electronic structures of DMSs, especially for the contribution from f electrons. The origin of magnetism, magnetic interaction and the possible mechanism of the colossal magnetic moment were explored. We found that, for materials containing f electrons, electronic correlation was usually strong and the spin–orbital coupling was sometimes crucial in determining the magnetic ground state. It was found that GaN doped by La was non-magnetic. GaN doped by Ce, Nd, Pm, Eu, Gd, Tb and Tm are stabilized at antiferromagnetic phase, while GaN doped by other RE elements show strong ferromagnetism which is suitable materials for spintronic devices. Moreover, we have identified that the observed large enhancement of magnetic moment in GaN is mainly caused by Ga vacancies (3.0μB per Ga vacancy), instead of the spin polarization by magnetic ions or originating from N vacancies. Various defects, such as substitutional Mg for Ga, O for N under the RE doping were found to bring a reduction of ferromagnetism. In addition, intermediate bands were observed in some systems of GaN:RE and GaN with intrinsic defects, which possibly opens the potential application of RE-doped semiconductors in the third generation high efficiency photovoltaic devices. 相似文献
338.
Kui Wu Bin YaoHuaijin Zhang Haohai YuZhengping Wang Jiyang WangMinhua Jiang 《Journal of Crystal Growth》2010,312(24):3631-3636
Neodymium (Nd) doped lutetium gallium garnet (Nd:Lu3Ga5O12, Nd:LuGG) single crystal was successfully grown by the optical floating-zone method for the first time to our knowledge. Its absorption and luminescence spectra at room temperature were measured. By using the J–O theory, the spectral parameters of Nd:LuGG were calculated, which indicated that Nd:LuGG should possess comparable and even better laser properties than Nd:YAG. The maximum output power of 855 mW at 1062 nm was achieved with slope efficiency of 23.4% under a pump power of 5.2 W, and optical conversion efficiency of 16.4%. All the results show that Nd:LuGG is a potential laser material. 相似文献
339.