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71.
Dominic R. Alfonso 《Surface science》2006,600(19):4508-4516
Density functional theory is used to investigate the initial inclusion of sulfur into the subsurface interstitial sites of Pd(1 1 1) surface. Pure subsurface adsorption is found to be less energetically favorable than on-surface adsorption. The incorporation of sulfur into the metal becomes more favorable than continuous adsorption on the surface after a critical on-surface sulfur coverage. We find subsurface sulfur occupation to be energetically favorable after adsorption of more than half a monolayer on the surface. Occupation of subsurface sites induces a pronounced structural distortion of the Pd(1 1 1) surface. We find significant expansion of interplanar spacing between the uppermost surface metal layers and rearrangement of the S overlayer. The interplay between the energy cost due to structural distortion of Pd(1 1 1) and the energy gain due to bond formation for different structures is discussed. 相似文献
72.
密闭空间空气中24种金属气溶胶的原子吸收光谱法测定 总被引:1,自引:0,他引:1
用原子吸收光谱法,一次采样,同时测定连续密闭12昼的窨 空气中24种金属气溶胶,即银、铝、钡、钙、镉、钴、铬、铜、铁、钾、镁、钼、钠、镍、铅、锑、硒、硅、锡、锶、钛、钒和锌。根据空间金属气溶胶的浓度、性质和原子化行为的不同。将样品分为四组,采用干法和湿法结合处理样品,同时测定,回收率在88-110%之间,各元素间基本无干扰,测定结果与文献报道值相近。 相似文献
73.
R. P. Chiarello H. You H. K. Kim T. Roberts R. T. Kempwirth D. Miller K. E. Gray K. G. Vandervoort N. Trivedi S. R. Phillpot Q. J. Zhang S. Williams J. B. Ketterson 《Surface science》1997,380(2-3):245-257
We performed in-situ X-ray reflectivity measurements of gold films during sputter deposition on polished silicon substrates. The measurements were performed at several substrate temperatures and under two argon pressures. The gold surfaces were also examined by scanning tunneling microscopy after deposition to obtain their real-space topographic images. These images were used to complement the X-ray reflectivity measurements in determining the effect of argon pressure on the gold surface and its height-height difference functions. An approximation for height-height difference functions was employed to analyze the X-ray reflectivity data. The measured interface width during growth followed a simple power law, consistent with recent theoretical results of dynamic scaling behavior. The scaling exponents, however, do not agree well with predictions based on some models in 2 + 1 dimensions. 相似文献
74.
Rafael de Souza Monteiro Lílian W. C. Paes José Walkimar de M. Carneiro Donato A. G. Aranda 《Journal of Cluster Science》2008,19(4):601-614
The adsorption of CO on Fe, Pt and Co clusters was modeled by the DFT approach using the B3LYP and the BPW91 functionals together
with the LANL2DZ and the 6-31G(d) basis set. These calculations show that although CO adsorbs more strongly on Pt than on
either Fe or Co, the dissociation energy on Fe and on Co is lower than the corresponding dissociation energy on Pt. Therefore,
the activation energy for dissociation is not determined by the adsorption energy. Additionaly, the CO bond distances also
do not show any correlation to the adsorption energy. 相似文献
75.
本文描述农用薄膜中Al、Fe、Mg、Ca、Si、Cu、Ti杂质元素的发射光谱分析法,该方法直接压样于石墨电极中,简便,快速,取得了满意的结果。 相似文献
76.
77.
We report the formation of a family of bulk metallic glasses (BMGs) based on rare earth element of ytterbium and alkaline earth element of calcium. The glass-forming ability, atomic packing density and corrosion behaviors of the BMGs show an extremum around the eutectic point with the change of the concentration of Yb and Ca. 相似文献
78.
We report that both shear and bulk moduli, not only shear modulus, are critical parameters involved in both homogeneous and inhomogeneous flows in metallic glass. The flow activation energy (?F) of various glasses when scaled with average molar volume Vm, which is defined as flow activation energy density ρE = ?F/Vm, can be expressed as: . The extended elastic model is suggestive for understanding the glass transition and deformation in metallic glasses. 相似文献
79.
Moritz Schwabe 《Journal of Non》2011,357(2):490-493
Creep/recovery measurements of amorphous PdCuSi ribbons have been performed. From these data we calculated the activation volume of relaxation processes in the temperature range from the glass transition temperature (Tg) to crystallization. The results indicate a correlation between applied stress and the activation volume of clusters in temperature regime close to Tg. With these results it is possible to compare molecular dynamic simulations for microscopic loss processes in metallic glasses with experimental values for mobile clusters. 相似文献
80.
J.Q. Wang 《Journal of Non》2011,357(1):220-222
By statistically analyzing 48 kinds of metallic glasses, we report clear correlations between the dimensionless ratio of glass transition temperature/Debye temperature (Tg/ΘD) and density (ρ), and between Young's modulus or shear modulus and Tg/ρ, for the glasses consisting of only metal elements, while the metallic glasses alloyed with metalloid elements exhibit distinct deviation from the correlations. It is suggested that the alloying of metalloid elements would show covalent-like bonding characteristics in metallic glass, and the found correlations can be used to distinguish different bonding characteristics in metallic glasses. 相似文献