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排序方式: 共有159条查询结果,搜索用时 187 毫秒
101.
研究了SrAl2O4∶Eu,Dy发光粉的机械余辉与机械劣化现象。结果表明,机械余辉强度与所施加的机械压力的大小及稀土掺杂离子的浓度有关。发光粉所受机械压力越大,掺杂Dy3 浓度越高,机械余辉强度越高;掺杂Eu2 浓度的变化,对机械余辉影响较小。从机械劣化研究结果可知,机械外力会导致荧光劣化和余辉劣化,而且后者总是先于前者发生。另外还对机械余辉与机械劣化机制进行了探讨,提出机械余辉是由机械能转化而来的热能将陷阱捕获的电子和空穴激发,二者复合导致发光;机械劣化是由于机械外力破坏了晶体结构,而且率先破坏晶格畸变严重的部分(包含Dy3 或空位的部分)。 相似文献
102.
103.
Erich Königsberger Peter M. May Glenn Hefter 《Monatshefte für Chemie / Chemical Monthly》2006,137(9):1139-1149
Summary. A Pitzer model representing the thermodynamics of alkaline sodium aluminate solutions is presented. It constitutes a key part of our
10-component synthetic Bayer liquor model communicated in this series of papers. The present model calculates thermodynamic properties, such as heat capacities,
osmotic coefficients, and densities, of these solutions as well as the solubilities of gibbsite and boehmite over temperature
and concentration ranges of industrial interest. 相似文献
104.
M. Ayvacikli 《光谱学快报》2014,47(7):504-511
A novel green-emitting phosphor copper-doped barium aluminate was synthesized by the conventional ceramic method. The crystallographic phase and microstructure identification were performed by powder X-ray diffraction and scanning electron microscopy. The X-ray diffraction pattern of the sample confirms the formation of the phosphor, and the scanning electron microscope image was recorded to observe the surface morphology. Differential thermal analysis results show that the initiatory decomposition temperature of barium carbonate starts at about 728°C. Cathodoluminescence studies have been undertaken to ensure the successful incorporation of copper ions in the barium aluminate host lattice. Under the excitation of the electron beam, the phosphor can efficiently display a broad green emission centered at 490 nm, corresponding to the transition from the conduction band edge to the excited state of copper in the barium aluminate host. However, there are no data available on copper luminescence in barium aluminate. New results on 3d activators of copper emission in the barium aluminate host are reported in this article, thus extending the list of copper-activated phosphors. These results strongly indicate that the copper-activated barium aluminate is a potential material used as a new high-brightness green phosphor for ultraviolet light-emitting diode and display devices. 相似文献
105.
Lilian AlcarazBertrand Coquebert de Neuville Andrew ListerBryan Roberts 《Tetrahedron letters》2011,52(45):5940-5942
The treatment of alkyl or aryl halides with an excess of tetrakis(pyridine)lithium tetrakis(N-dihydropyridyl)aluminate affords the corresponding 3-substituted-1,2,3,6-tetrahydropyridines in moderate to good yields via a tandem alkylation-reduction reaction. 相似文献
106.
选取了代表性水溶液体系铝硅酸钠的典型试样:铝酸钠溶液、硅酸钠溶液、铝硅酸钠溶液,分别测定了它们的拉曼光谱。构建了系列铝硅酸钠溶液微结构模型,应用量子化学从头计算方法优化了空间几何构型,并计算了其拉曼光谱,计算结果分别与相应试样的实验拉曼光谱进行对比。结果表明:在高浓度条件下,铝酸钠溶液中铝物种的主要存在形式是Al(OH)-4(Q0)和Al2O(OH)2-6(2Q1),低浓度时只存在Q0结构的铝酸根离子,以4Q0聚集态的四水合分子形式存在;在2.0M Na2SiO3溶液中,硅酸钠团簇结构可能的存在形式是四水合Na2H2SiO4;在铝硅酸钠溶液中,铝硅酸根离子的形态是由Si-O-Si和Al-O-Si键以不同铝硅原子配比相互连接形成的环状或链状结构。 相似文献
107.
用OP作增感剂原子吸收光谱法测定微量钙 总被引:3,自引:2,他引:1
研究以表面活性剂OP作增感剂。火焰原子吸收光谱法测定微量钙的方法。试验发展OP的加入可使吸光度增加70%,分析灵敏度得到提高。同时,以0.5mg.ml^-1钾、6.0mg.ml^-1镧盐及2.0mg.ml^-18-羟基喹啉作消电离剂、释放剂和保护剂消除基体物质的干扰。据此建立了标准加入法直接测定铝酸钠溶液中微量钙的分析方法。其线性范围为0-7.5mg.L^-1。灵敏度为0.05mg.L^-1/1%。方法灵敏度高,操作简便,结果准确度和精密度满足分析要求。 相似文献
108.
109.
The effect of calcium substitution on the afterglow of tetrastrontium aluminate phosphors (Sr4Al14O25:Eu2+, Dy3+) was investigated. A series of (Sr1-xCax)O⊎nAl2O3:Eu2+(1%), Dy3+(0.5%), with variation of calcium content (x = 0 − 1), were synthesized by a high temperature solid state reaction in a reducing
atmosphere. The photoluminescence, persistent luminescence (afterglow), and lumen equivalents of these materials were studied
and compared. It turned out that the afterglow properties of the phosphors were strongly dependent on the Sr/Ca ratio. As
the Ca content increased, a phase transition and blue shift in emission spectra were observed.
相似文献
110.
Crystals of scandium magnesium aluminate, ScAlMgO4, were grown from the melt prepared from stoichiometric quantities of Sc2O3, Al2O3 and MgO. Single-crystal X-ray diffraction indicates that ScAlMgO4 crystallizes in the space group R3 m with a = b = 3.2506(9) A, c = 25.152(8)A, V= 230.16(11)A^3, Z= 3, F(000) = 234,μ = 2.424 cm^-1, the final R = 0.0381 and wR = 0.1061 for 1874 observed reflections with I 〉 2σ(I). In ScAlMgO4, all Sc atoms are coordinated octahedrally, whereas AI or Mg atoms are forming a tetrahedron, or in a triangular bipyramid if one distant O atom is included. The structure of ScAlMgO4 is characterized by { [AlMgO4]^3-}∞^2 layers parallel to the ab plane, and they are further connected into a 3-dimen-sional framework by Sc atoms via O(1) atoms between the layers. 相似文献