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1.
Traces of antimony, tin and arsenic in cadmium products were determined by pulse polarography. Arsenic was distilled, while antimony and tin were precipitated as hydroxides with manganese dioxide as carrier; some lead was coprecipitated with tin, hence these elements were further separated by distillation. In all cases quantitative recoveries were obtained. Antimony(III) was determined in a hydrochloric acid-sodium hypophosphite mixture, tin(IV) in a hydrochloric-hydrobromic acid mixture and arsenic(III) in sulphuric acid as supporting electrolytes; for arsenic(III), methylene blue had to be added. A sample weight of 10 g and an end volume of 10 ml allowed the determination down to about 0.004 p.p.m. antimony, 0.006 p.p.m. tin and 0.003 p.p.m. arsenic in cadmium. Several synthetic samples and commercially available cadmium products were analysed. 相似文献
2.
Brown SD Strange P Bouchenoire L Zarychta B Thompson PB Mannix D Stockton SJ Horne M Arola E Ebert H Szotek Z Temmerman WM Fort D 《Physical review letters》2007,99(24):247401
We report measured dipolar asymmetry ratios at the LIII edges of the heavy rare-earth metals. The results are compared with a first-principles calculation and excellent agreement is found. A simple model of the scattering is developed, enabling us to reinterpret the resonant x-ray scattering in these materials and to identify the peaks in the asymmetry ratios with features in the spin and orbital moment densities. 相似文献
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A pulse-polarographic method for the simultaneous determination of traces of nickel, zinc, cobalt and manganese in cadmium and its compounds is described. Interference from the reduction of the cadmium matrix was eliminated by a prior electrolytic deposition of cadmium on a mercury cathode at a controlled potential of –0.90 V vs. S.C.E. Iron in excess interfered with the determination of cobalt and was therefore extracted from the electrolysed solutions. The polarographic determination was performed in 0.1 M lithium acetate -0.025 M lithium thiocyanate as supporting electrolyte. A sample weight of 10 g and a final volume of 10 ml allowed the determination of about 0.08 p.p.m. nickel, 0.01 p.p.m. zinc, 0.02 p.p.m. cobalt and 0.003 p.p.m manganese. Less than 0.01 p.p.m. nickel could be determined with a 0.25 M pyridine 0.05 M potassium chloride supporting electrolyte. Several synthetic samples and commercially available cadmium products were analysed. 相似文献
4.
The second reduction step of Eu(III), Yb(III) and Sm(III) in 0.04 M tetramethylammonium perchlorate in the pH range 1.8–7 was investigated by cyclic voltammetry and d.c. polarography. The proposed reaction scheme at large hydrogen ion/lanthanide ion concentration ratios involves the reduction of the lanthanide(II) ion to the metallic state accompanied by a surface catalytic reaction in which the reactant is regenerated and also hydroxyl ions are formed which induces the precipitation of lanthanide(II) hydrous oxide on the electrode surface. This lanthanide(II) hydroxide is reduced at more negative potentials than the hydrated lanthanide(II) species. At lower hydrogen ion/lanthanide ion concentration ratios a preceding chemical reaction, probably involving hydrolyzed lanthanide(II) species, becomes rate determining. 相似文献
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The kinetics of the reduction of Sb(V) at a glassy carbon rotating-disk electrode have been investigated in 9.5 M HCl. The current-potential curve is characterized by a single irreversible wave, the limiting current being linearly related to the Sb(V) concentration and the square root of the rotation rate. Kinetic parameters of the reaction have been evaluated. Anodic oxidation currents of Sb(III) cannot be quantitatively measured owing to the interference of the oxidation of chloride. 相似文献
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The ab initio self-interaction-corrected local-spin-density approximation is used to study the electronic structure of both stoichiometric and nonstoichiometric nickelates. From total energy considerations it emerges that, in their ground state, both LiNiO2 and NaNiO2 are insulators, with the Ni ion in the Ni3+ low-spin state (t(2g)(6)e(g)(1)) configuration. It is established that a substitution of a number of Li/Na atoms by divalent impurities drives an equivalent number of Ni ions in the NiO2 layers from the Jahn-Teller (JT)-active trivalent low-spin state to the JT-inactive divalent state. We describe how the observed considerable differences between LiNiO2 and NaNiO2 can be explained through the creation of Ni2+ impurities in LiNiO2. The indications are that the random distribution of the Ni2+ impurities might be responsible for the destruction of the long-range orbital ordering in LiNiO2. 相似文献