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61.
62.
Bao-xin Huang Yi-hua Liu Xiaobo Yuan Cheng-jian Wang Ru-zhen Zhang Liang-mo Mei 《Journal of magnetism and magnetic materials》2004,280(2-3):176-183
Enhancements of the low-field (LFMR) and high-field magnetoresistance (HFMR) were observed in the manganite system prepared by doping Nb2O5 into La0.67Sr0.33MnO3 powders. The maximum MR ratios at 77 K with H=1 T and 1 kOe are 30% and 20% for the 0.07 molar ratio doped sample, which are 1.7 times and 1.6 times as large as that for LSMO, respectively. An MR effect up to 6.5% was also found for the sample with x=0.03 at room temperature (RT). The spin-dependent tunneling and scattering at the interfaces of grain boundaries are responsible for the LFMR while the HFMR originates from a noncollinear spin structure in the surface layer. With increasing x, the Curie temperature (TC) decreases monotonically from 364 to 154 K while the temperature TP related to the peak resistivity decreases firstly to a minimum of 204 K (x=0.06) and then rises up to 240 K (x=0.1). There is a maximum resistivity ρ for the sample with x=0.06, which is higher than that for LSMO by five orders of magnitude. It is due to the enhancement of spin-dependent and independent scattering and tunneling effects on the interfaces of grain boundaries and inside the grains. 相似文献
63.
以SCC-DV-X,方法对Sm_4OCl_6、Eu_4OCl_6、Yb_4OCl_6和Gd_6N_2Cl_(12)等4个体系作了量化计算。结果表明,嵌入原子在四面体簇的合成中起决定性作用。体系6个骨架轨道中,3个是嵌入原子与稀土原子的成键轨道,另3个是稀土原子通过嵌入原子形成的弱键轨道。用Sm、Eu等元素能合成四面体嵌合物,与其价态较低有关,低价态使稀土元素d、f轨道收缩较少、成键能力增大。而富含f电子的Yb体系,4f为主要价轨道。 相似文献
64.
ICP-AES法测定高纯氧化铕中稀土杂质元素 总被引:1,自引:0,他引:1
研究了锌粉还原 5709萃淋树脂分离富集 ICP AES法测定高纯氧化铕中14个稀土杂质元素的方法,用ICP AES法测定稀土元素工作曲线下限为(以氧化物计)镧为0.05mg·L-1,铈、镨、钇为0.25mg·L-1,钕、钐、铽、镝、钬为0.1mg·L-1,铒、铥、镱、镥、钇为0.05mg·L-1,回收率为90%~106%。方法简便、准确、快速,可用于99.99%氧化铕中14个稀土杂质元素的测定。 相似文献
65.
66.
Theresa Komm 《Journal of solid state chemistry》2005,178(2):454-463
The two non-isotypical rubidium rare-earth(III) thiophosphates Rb3M3[PS4]4 of praseodymium and erbium can easily be obtained by the stoichiometric reaction of the respective rare-earth metal, red phosphorus and sulfur with an excess of rubidium bromide (RbBr) as flux and rubidium source at 950°C for 14 days in evacuated silica tubes. The pale green platelet-shaped single crystals of Rb3Pr3[PS4]4 as well as the pink rods of Rb3Er3[PS4]4 are moisture sensitive. Rb3Pr3[PS4]4 crystallizes triclinically in the space group (, , , α=84.329(4)°, β=88.008(4)°, γ=80.704(4)°; Z=2), Rb3Er3[PS4]4 monoclinically in the space group P21/n (, , , β=95.601(6)°; Z=4). In both structures, there are three crystallographically different rare-earth cations present. (M1)3+ is eightfold coordinated in the shape of a square antiprism, (M2)3+ and (M3)3+ are both surrounded by eight sulfur atoms as bicapped trigonal prisms each with a coordination number of eight as well as for the praseodymium, but better described as CN=7+1 in the case of the erbium compound. These [MS8]13− polyhedra form a layer according to by sharing edges with the isolated [PS4]3− tetrahedra (d(P-S)=200-209 pm, ?(S-P-S)=102-116°). These layers are stacked with a repetition period of three in the case of the praseodymium compound, but of only two for the erbium analog. The rubidium cation (Rb1)+ is located in cavities of these layers and tenfold coordinated in the shape of a tetracapped trigonal antiprism. The also tenfold but more irregularly coordinated rubidium cations (Rb2)+ and (Rb3)+ reside between the layers. 相似文献
67.
在金属氢化物一镍电池(MH/Ni)负极材料中,ABS型贮氢合金是非常具有吸引力的一种,以AB。型贮氢合金作为负极材料的MH/Ni电池目前已大批量进入市场.其中A代表混合稀土RE(主要成分为La,Ce,Pr,Nd);B代表Ni和Co,Mll,AI等取代元素.B侧取代元素已被广泛研究D,习,A侧混合稀土的成分也已引起人们的广泛重视*‘,’],*血1c等【阿针对儿一N13。5C00.75Mll。。A10.3,详细研究了L31。CI。BS系列合金,得出在。=0.2处合金具有较好的综合性能.本文针对B侧Ni。。。Coo,。Mno、。Alo二。(记为民)成分,在研… 相似文献
68.
Single crystals of CsHo3Te5 and Cs3Tm11Te18 have been grown as byproducts in the synthesis of CsLnZnTe3 (Ln=Ho or Tm) through the reaction of Ln, Zn, and Te with a CsCl flux at 850 °C. The crystal structures have been determined from single-crystal X-ray diffraction data. CsHo3Te5 crystallizes in space group Pnma of the orthorhombic system whereas Cs3Tm11Te18 crystallizes in the space group C2/m of the monoclinic system. Each of the compounds adopts a three-dimensional structure; each possesses tunnels built from LnTe6 octahedra that are filled with Cs atoms. The pseudo-rectangular tunnel in CsHo3Te5 is large enough in cross-section to accommodate two symmetrically equivalent Cs atoms. In the Cs3Tm11Te18 structure there are two different sized tunnels: the smaller one is only large enough to host one Cs atom per unit cell whereas the larger one can accommodate two Cs atoms. The electronic structure of CsHo3Te5 was calculated. The band gap is estimated to be about 1.2 eV, consistent with the black color of the crystals. 相似文献
69.
Svilen Bobev Eric D. Bauer John L. Sarrao Bernhard Eck 《Journal of solid state chemistry》2004,177(10):3545-3552
The Zintl compound EuGe2 crystallizes in the trigonal space group (No. 164) with the CeCd2-structure type. Its structure can be formally derived from the hexagonal AlB2-structure type by a strong puckering of the hexagonal layers. The chemical bonding in EuGe2 can be rationalized according to the Zintl concept as (Eu2+)(Ge1−)2, since the europium atoms are divalent and each germanium atom receives one additional valence electron. In that sense, EuGe2 is expected to be a closed-shell compound with semiconducting behavior. However, temperature dependent resistivity measurements show EuGe2 to be metallic. Subsequently, detailed crystallographic studies revealed the structure and the composition of EuGe2 to be free of defects and impurities, which, along with the confirmed divalent oxidation state of the europium atoms by means of magnetic measurements, make EuGe2 another example of a metallic Zintl phase. These results are in good agreement with the results of electronic structure calculations such as TB-LMTO-ASA (LDA) and FLAPW (GGA), which reveal non-zero DOS at the Fermi level. 相似文献
70.
《Current Applied Physics》2018,18(11):1205-1211
The frustrated magnet has been regarded as a system that could be a promising host material for the quantum spin liquid (QSL). However, it is difficult to determine the spin configuration and the corresponding mechanism in this system, because of its geometrical frustration (i.e., crystal structure and symmetry). Herein, we systematically investigate one of the geometrically frustrated magnets, the TbB4 compound. Using resonant soft x-ray scattering (RSXS), we explored its spin configuration, as well as Tb's quadrupole. Comprehensive evaluations of the temperature and photon energy/polarization dependences of the RSXS signals reveal the mechanism of spin reorientation upon cooling down, which is the sophisticated interplay between the Tb spin and the crystal symmetry rather than its orbit (quadrupole). Our results and their implications would further shed a light on the search for possible realization of QSL. 相似文献