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51.
1H NMR spectra of 26 substituted chalcones (3-aryl-1 phenyl-2-propene-1-ones and 1-aryl-3-phenyl-2-propene-1-ones) have been studied. The chemical shifts of the α and β protons to the carbonyl group were correlated with Hammett s? parameters. To gain information on the effect of the transmission of the resonance and inductive contributions of the substituents on the chemical shifts of H-α and H-β, two parameter correlations with ?? and ?? parameters were also perfomed. The chemical shifts of the aromatic protons of the para-disubstituted benzene ring correlated with the ai substituent increments. 相似文献
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The precipitation and dissolution of AgI in the presence of methylene blue (MB · Cl) and sodium dodecyl sulphate (NaDS) was followed by X-ray diffraction analysis.At high MB · Cl concentration, the absence of AgI precipitates was observed, which is explained by considering the redox process MB+ + 2I– MB– + I2. The decrease in I– concentration causes dissolution or inhibition of growth of solid AgI which is significant at relatively high MB · Cl concentrations. The addition of NaDS causes the disappearance of these effects, which is explained by the incorporation of MB in NaDS micelles.These explanations are supported by the potentiometric measurements using Ag/Ag2S and Pt electrodes. 相似文献
54.
F. Blomberg H. Rüterjans K. Lintner F. Toma S. Fermandjian 《Magnetic resonance in chemistry : MRC》1978,11(12):598-602
The dipeptide alanylproline has been prepared with the proline residue both 13C (15%) and 15N (95%) enriched. 15N NMR spectra of alanylproline reveal signals for both possible conformations—cis and trans—of the dipeptide backbone in solution. Different pK values for both conformers are obtained from the pH dependence of the 15N chemical shifts using a least square programme based on the Henderson–Hasselbach equation. These different values are discussed in terms of interaction between the α-amino group and the carboxylate group and between the carboxylate oxygen and the carbonyl oxygen of the dipeptide via hydrogen bonding. Further evidence for these interactions is obtained from the pH dependence of the ratio of the 15N NMR signal intensities of the two conformers. One, two or three bonded 13C? 15N coupling constants measured in the 13C NMR high resolution spectra have different values in the cis and trans isomers of alanylproline and thus indicate different geometry in the pyrrolidine ring. 相似文献
55.
N. Filipović-Vinceković V. Tomašić N. Nekić M. Široki 《Journal of Radioanalytical and Nuclear Chemistry》1990,139(2):239-247
The influence of long-term interactions on sorption of cesium on montmorillonite has been examined. After initial fast sorption due to ion-exchange, the additional two-step sorption as a result of dissolution of main clay constituents, changes in solution chemistry and readsorption and/or precipitation of resultant species, were observed. 相似文献
56.
The Knight shift and the spin-lattice relaxation time of 7Li and 1H have been measured in Li-methylamine solutions, in which a transition from the metallic to the nonmetallic states occurs. 相似文献
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This paper presents analytical travel time models for the computation of travel time for automated warehouses with the aisle transferring S/R machine (in continuation multi-aisle AS/RS). These models consider the operating characteristics of the storage and retrieval machine such as acceleration and deceleration and the maximum velocity. Assuming uniform distributed storage rack locations and pick aisles and using the probability theory, the expressions of the cumulative distribution functions with which the mean travel time is calculated, have been determined. The computational models enable the calculation of the mean travel time for the single and dual command cycles, from which the performance of multi-aisle AS/RS can be evaluated. A simulation model of multi-aisle AS/RS has been developed to compare the performances of the proposed analytical travel time models. The analyses show that regarding all examined types of multi-aisle AS/RS, the results of proposed analytical travel time models correlate with the results of simulation models of multi-aisle AS/RS. 相似文献
60.
Buatier de Mongeot F Toma A Molle A Lizzit S Petaccia L Baraldi A 《Physical review letters》2006,97(5):056103
CO dissociation on rhomboidal faceted nanopyramids, produced on Rh(110) by fine-tuning of ion irradiation conditions, has been studied by high resolution core-level spectroscopy. We find that this morphology presents a large efficiency towards CO dissociation, a process which is inhibited on flat (110) terraces. We also measured the reactivity of nanostructures bound by different artificial step distributions identifying the sites responsible for the molecular bond disruption in the undercoordinated (n=6) edges running along the [11[over ]2] equivalent directions, with CO sitting in on-top configuration. 相似文献