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排序方式: 共有154条查询结果,搜索用时 546 毫秒
31.
B. Massani J. S. Loveday J. J. Molaison A. M. dos Santos X. P. Wang L. L. Daemen 《高压研究》2020,40(3):339-357
ABSTRACT Quantitative single crystal neutron-diffraction in diamond anvil cells has so far been limited by the neutron flux available at the various neutron sources. As a result, highly precise measurements of the exact position of light elements have not been possible preventing, for example, structural studies of hydrogen and hydrogen bonds under pressure. Here we report experiments carried out on SNAP at the Spallation Neutron Source (ORNL, TN, USA) to explore the possibility and current limits of such studies. Furthermore, we benchmarked the obtained data quality with reference experiments carried out on TOPAZ, a dedicated single-crystal instrument. We show that measuring single-crystal diffraction intensities on SNAP is possible to such a precision that we are able to resolve the hydrogen bonds in potassium dideuterium phosphate (DKDP) as well as in ice VI. 相似文献
32.
K. Schröter G. Wilde R. Willnecker M. Weiss K. Samwer E. Donth 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(1):1-5
High-resolution synchrotron-radiation powder diffraction experiments were performed to observe structural changes induced
by hydrogen loading in rapidly-quenched Ti-Zr-Ni alloy ribbons with dominant icosahedral character. Lattice expansion effects
due to hydrogen storage in Ti-Zr-Ni quasicrystals as well as phonon and phason disorder coefficients are obtained from an
analysis of diffraction linewidths.
Received: 26 August 1997 / Revised: 8 January 1998 / Accepted: 10 February 1998 相似文献
33.
On the mechanism of the interaction between oxygen and close-packed single-crystal aluminum surfaces
Using periodic first principles simulations we investigate the interaction of oxygen molecules with both regular Al(111) and Al(001) surfaces as well as a stepped Al(111) substrate. The limitation of this approach is the use of thin metallic slabs with a limited range for their coverage by adsorbed oxygen. The advantage is the detailed modeling that is possible at an atomic level. On the regular Al(111) surface, we have been able to follow the oxidation process from the approach of O2 molecules to the surface, through the chemisorption and absorption of O atoms, up to the formation of first Al2O3 formula units. An energetically feasible mechanism for the formation of these Al2O3 ‘molecules’ is proposed but their aggregation to Al2O3 growth nuclei can only be surmised. On the Al(001) surface, absorption of oxygen atoms occurs more readily without any restrictions on the density of their surface overlayer, in agreement with the failure to observe a distinct chemisorption stage for O on Al(001) experimentally. The stepped Al(111) surface contains both {111} and {001} microfacets: the latter are obviously preferred for penetration of the oxygen adatoms into the subsurface space of the substrate. Before considering the O/Al interfaces the computational method is tested thoroughly by simulations on bulk Al and close-packed aluminum surfaces. 相似文献
34.
分别以柠檬酸三钠 (TSC)及N 聚乙烯吡咯烷酮 (PVP)为稳定剂 ,首先采用KBH4化学还原法制得球形Ag纳米粒子溶胶 (粒径 12~ 18nm) ;再将两种溶胶置于 5 0 0W卤钨灯下进行光诱导转化实验 ,一定转化时间后 ,球形Ag纳米粒子分别转化为单晶Ag纳米三棱体 (边长 80~ 12 0nm)和立方体 (边长 90~ 2 0 0nm) .利用透射电子显微镜 (TEM )、电子衍射 (ED)和紫外 可见吸收光谱 (UV Vis)等手段对单晶Ag纳米三棱体和立方体进行了表征 ,对光转化过程中Ag粒子由球形到三棱体和立方体的转变原因进行了初步的分析和探讨 .认为主要原因在于不同种类稳定剂在Ag的不同晶面吸附作用不同 ,从而形成沿某一晶面取向生长的Ag单晶体 . 相似文献
35.
Yasuhiko Takahashi 《Journal of solid state chemistry》2005,178(12):3667-3671
Single crystals of the LiCoO2-LiAlO2 solid solution compounds LiAl0.32Co0.68O2 and LiAl0.71Co0.29O2 were synthesized by a flux method using alumina crucibles. A single-crystal X-ray diffraction study confirmed the trigonal space group and the lattice parameters a=2.8056(11) Å, c=14.1079(15) Å, and c/a=5.028 for LiAl0.32Co0.68O2, and a=2.8023(7) Å, c=14.184(4) Å, and c/a=5.061 for LiAl0.71Co0.29O2. The crystal structures have been refined to the conventional values R=3.2% and wR=2.4% for LiAl0.32Co0.68O2, and R=3.6% and wR=3.5% for LiAl0.71Co0.29O2. The evidence of the location of Al atoms in the pseudotetragonal coordination (6c site), reported previously in LiAl0.2Co0.8O2, could not be observed in the present electron density distribution maps in both LiAl0.32Co0.68O2 and LiAl0.71Co0.29O2. The octahedral distortion analysis indicated that the Al-substitution strongly affected the distortion of the LiO6 octahedron in this solid-solution compound system, but hardly affected that of the (Al.Co)O6 octahedron. 相似文献
36.
Ivan V. Ogorodnyk Igor V. Zatovsky Vyacheslav N. Baumer 《Journal of solid state chemistry》2006,179(12):3681-3687
The single crystals of caesium magnesium titanium (IV) tri-oxo-tetrakis-diphosphate bis-monophosphate, Cs3.70Mg0.60Ti2.78(TiO)3(P2O7)4(PO4)2, crystallize in sp. gr. P-1 (No. 2) with cell parameters a=6.3245(4), b=9.5470(4), c=15.1892(9) Å, α=72.760(4), β=85.689(5), γ=73.717(4), z=1. The titled compound possesses a three-dimensional tunnel structure built by the corner-sharing of distorted [TiO6] octahedra, [Ti2O11] bioctahedra, [PO4] monophosphate and [P2O7] pyrophosphate groups. The Cs+ cations are located in the tunnels. The partial substitution of Ti positions with Mg atoms is observed. The negative charge of the framework is balanced by Cs cations and Mg atoms leading to pronounced concurrency and orientation disorder in the [P2O7] groups, which coordinate both. 相似文献
37.
研究了不同电极表面结构及有机添加剂对C60电化学还原过程的影响。实验结果表明,富勒烯及其阴离子的电还原活性取决于电极表面结构的影响,即:ipc(多晶)〉ipc[Pt(111)]〉ipc[Pt(110)],且在Pt(111)及Pt(110)晶面上C60^1-及C60^2-的还原电位均有一定的位移。另外,实验结果还表明当溶液中分别添加苯胺及邻氨基酚时,其对C60电还原过程的影响机理将有所不同。 相似文献
38.
Fatima Zohra Chiboub Fellah Jean-Pierre Costes Françoise Dahan Carine Duhayon Jean-Pierre Tuchagues 《Polyhedron》2007
We demonstrate with the help of structural determinations and spectroscopic data that the nuclearity of Cu–Ca complexes derived from compartmental Schiff base ligands does not depend on the ionic radius of calcium. The main factors governing these reactions are the different affinities of the calcium ions for the anionic species present in solution: the tetradentate O2O2 coordination site of the ligand and the nitrato ions. Because these affinities do vary upon going from calcium to lanthanide ions, it is not possible to use the template effect of the trinuclear Cu–Ca–Cu complexes in order to prepare the corresponding Cu–Ln–Cu complexes. 相似文献
39.
《Comptes Rendus Physique》2018,19(8):657-671
Two outstanding aerospace-oriented high-temperature materials, the single-crystal nickel-based superalloys for high-pressure turbine blades and the γ-TiAl-based alloys for low pressure turbine blades, are being presented here. In both cases, the optimisation of their mechanical properties is based on a high knowledge of metallurgy, mixing together different aspects such as processes, alloy design, deformation mechanisms, impact of oxidative environment or interaction between protective layers and protected alloy. Historical evolutions are recalled and put into perspective with more recent research activities. 相似文献
40.
An in situ high-pressure X-ray diffraction study has been carried out at room temperature up to 9.26 GPa on synthetic Mn2Sb2O7 having a weberite-3T structure. A 2nd-order Birch–Murnaghan Equation of State (EoS) was used to refine the pressure–volume data. The refinement of the unit-cell volume and of the isothermal bulk modulus at room pressure leads to: V0 = 782.7(2), KT0 = 150(1) GPa. Unit-cell parameters decrease gradually as a function of pressure with a bulk modulus anisotropy scheme, with a being the softest direction. The overall mean polyhedral distances are quite constant, indicating a scarce compressibility of both the A and B polyhedra in the pressure range investigated. The compressional behaviour of Mn2Sb2O7 is compared with that shown by ingersonite, Ca3MnSb4O14, and synthetic orthorhombic Ca2Sb2O7. 相似文献