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991.
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994.
Zheng Y Orbulescu J Ji X Andreopoulos FM Pham SM Leblanc RM 《Journal of the American Chemical Society》2003,125(9):2680-2686
Monolayers of several peptide lipids at air-water and air-solid interfaces were prepared using Langmuir and Langmuir-Blodgett (LB) film techniques, and tested as fluorescent sensors for copper ions in aqueous phase. In one method, both the ionophore and the fluorophore were in the same molecule (lipid A), so intramolecular interaction was responsible for the fluorescence quenching of monolayers of this lipid. In the other method, ionophore and fluorophore were located on two different molecules (lipids B and C) so the intramolecular coupling does not exist; instead the fluorescence quenching was realized by a through-space interaction mechanism. Several experimental techniques, including pi-A isotherm, epifluorescence microscopy, and absorption and emission spectroscopies were used to study the different characteristics of copper ion effect on the properties of the lipid monolayers. Additionally, the fluorescence quenching properties of the Langmuir monolayers were found to be transferred to the one-layer LB films. On LB films, the fluorescence response presented a clear selectivity for copper ions in comparison with several other transition metal ions. Further, an excellent reversibility was observed: the fluorescence was switched OFF by immersing the solid substrate in copper ion solution and ON by washing with HCl solution. The intermolecular approach used here seems to be a very flexible and general method to design surface-oriented fluorescent sensors to meet different analytic purposes. 相似文献
995.
A new lanthanide-sensitized luminescence system: europium–sparfloxacin–1,10-phenanthroline–sodium dodecyl sulfate has been discovered. The spectrofluorimetric properties of the system were studied. The effect of experimental conditions on the fluorescence intensity was defined. Under the optimum conditions, the fluorescence intensity of the system is a linear function of the concentration of europium in the range 5.0×10–9–1.0×10–6 mol L–1 and the detection limit is 1.0×10–10 mol L–1. The system was used for the determination of trace amounts of europium in rare earth samples with satisfactory results. 相似文献
996.
Photolysis of Ru(bpy)(2)(en)(2+) and Ru(bpy)(2)(tn)(2+), where bpy = 2,2'-bipyridine, en = ethylenediamine, and tn = 1,3-propylenediamine, was studied in acetonitrile using on-line electrospray mass spectrometry (ES-MS). These complexes are known to undergo a four-electron oxidation photochemically, giving the alpha,alpha'-diimine complexes. The monoimine complexes involved in this stepwise process were detectable after photoirradiation (lambda >420 nm). Also, new ligand-oxidized complexes Ru(bpy)(2)(en+14)(2+) and Ru(bpy)(2)(tn+14)(2+) were observed together with photosubstitution products such as Ru(bpy)(2)(AN)(2)(2+) and Ru(bpy)(2)(AN)(2)X(+) (AN = acetonitrile). The notation (en+14) and (tn+14) represents loss of two hydrogen atoms and addition of an oxygen atom to the en and tn ligands. Photosubstitution intermediates with the monodentate diamine, Ru(bpy)(2)(tn)(AN)(2+) and Ru(bpy)(2)(tn)(AN)X(+), were detected in the ES mass spectrum of the tn complex but not in that of the en complex. Other photosubstituted intermediates with the monodentate (en+14) and (tn+14) ligands were detected by on-line mass analysis. The electrospray technique combined with use of a flow-through photoreaction cell was shown to be a useful tool for studying photolysis of inorganic metal complexes. 相似文献
997.
Si Jung Yeh J. M. Lo C. L. Tseng 《Journal of Radioanalytical and Nuclear Chemistry》1988,124(1):157-170
The radioactive tracer technique was used to investigate the adsorption behaviour of 47 ions onto hydrous magnesium oxide. Detailed studies on Co(II), Zn(II), La(III) and Ce(III) reveal that the adsorption isotherms of these ions obey Langmuir's law. Radiochemical separation using hydrous magnesium oxide was applied to the RNAA of NBS standard reference materials, and satisfactory results were obtained. Hydrous magnesium oxide was also used to adsorb various ions from aqueous solution for the purpose of preconcentration which was followed by NAA or ICP-AES analysis. Satisfactory results have been observed in both methods. 相似文献
998.
A dysprosium/EDTA/Tiron/surfactant system at pH 11–12 is used for the spectrofluorimetric determination of dysprosium. The fluorescence intensity is increased 22-fold on addition of cetyltrimethylammonium bromide. There is no interference from at least a 100-fold molar excess of other rare earth ions, except for terbium. 相似文献
999.
The catalytic performance of Ni(η^5-Ind)2 complex in the dimerization of propylene was studied in combimation with an organoaluminum co-catalyst,eventually in the presence of a phosphine ligand.The effects of the type of aluminum co-catalyst and its relative amount,the nature of phosphine ligand and P/Ni ratio as well as the reaction temperature were examined.The results indicated that the nickel precatalyst exhibited high productivity for the propylene dimerization together with organoaluminum.It was likely to strongly modify the reactivity in the catalytic sytem when using phosphine ligand as additives,especially at the reaction temperature below 0℃.The catalytic system based on Ni(η^5-Ind)2 complex displaed an extremely high productivity(TOF up to 16900h^-1)and a good regioselectivity to 2,3-dimethylbutenes (2,3-DMB) in dimers(66.4%)under proper reaction parameters. 相似文献
1000.
Kui Liao Xiao‐Si Hu Ren‐Yi Zhu Ruo‐Han Rao Jin‐Sheng Yu Feng Zhou Jian Zhou 《中国化学》2019,37(8):753-753
The cover picture shows a highly enantioselective organocatalytic protonation of monofluorinated silyl enol ethers to α‐secondary α‐fluoroketones using water as proton source. Notably, in the presence of D2O and MeOD, the facile access of chiral α‐deuterated α‐fluoroketones in excellent enantioselectivity is achieved. More details are discussed by Zhou et al. on page 799–806.