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101.
This work deals with the derivation and the analysis of a new mathematical model for vehicular traffic along a one-way road obtained by the coupling of a uniform and an adaptive discretization of the velocity variable in the framework of the kinetic theory. Interactions are modelled by stochastic games where the output of interactions depends on the local density and is not linearly additive. 相似文献
102.
We review estimates for effects of parity mixing on the α-capture of vector polarized 6Li to the 5.16 MeV, 2+, T = 1 state in 10B. The cross section depends on the 6Li polarization direction because of isovector parity mixing with the 5.11 MeV, 2?, T = 0 state. The effect is enhanced due to isospin conservation. The α-width of the 5.11 MeV state, an important parameter for calculating the enhancement, has been measured to be 0.98 ± 0.07 keV. The consequences of parity mixing are reevaluated using best available values for the relevant parameters. 相似文献
103.
Alessandro D’Aprano Bianca Sesta Noemi Proietti Vincenzo Mauro 《Journal of solution chemistry》1997,26(6):649-662
Conductivity measurements, focused on the counterion binding of lithium perfluorononanoate (LiPFN) micelles in pure water
and in the presence of poly(vinyl pyrrolidone) (PVP), have been carried out. An abrupt decrease of the conductance of the
LiPFN in pure water, due to the self aggregation of anions and to dynamic linkage of cations on the micellar surface, has
been found. Analysis of the conductometric data indicates that about 50% of the stoichiometric concentration of Li+ interacts with the head groups of the perfluorinated anions involved in micellar assembly. Conductometric data of LiPFN-water-PVP
systems reveals a favorable influence of the PVP on the micellization process modulated by the concentration and by the molecular
weight of the polymer. Analysis of these data shows that in presence of PVP the degree of binding of lithium ion to the micellar
assemblies linked to the polymer is smaller than in pure water. By increasing the amount of surfactant in solution up to the
concentration where the polymer becomes saturated by LiPFN micelles, the binding of lithium ion in the system becomes slightly
greater than that observed in LiPFN-water system. This finding can be interpreted in terms of additional binding of lithium
ion to the polymer chains. Conductivity measurements carried out on LiClO4 and KClO4 in water + PVP support this interpretation. 相似文献
104.
Ribicki Ariane Caroline Chemin Bianca Gurski Van Haandel Viviane Jandira Winiarski João Paulo de Castro Rozada Thiago Pessoa Christiana Andrade Estrada Ruben Auccaise Fiorin Barbara Celânia Fujiwara Sérgio Toshio 《Journal of Sol-Gel Science and Technology》2018,87(1):216-229
Journal of Sol-Gel Science and Technology - A silsesquioxane based on a silica matrix and 4-(aminomethyl)pyridine group was successfully synthesized using the sol–gel process with the... 相似文献
105.
Hansen J Titko MA DeSchepper D Dodson G Donnelly TW Dow K Ent R Farkhondeh M Korsch W Kramer LH Lee K Makins NC Milner RG Tieger DR Welch TP Jones CE Arrington J Beise EJ Bray B Carr RW Filippone BW Gao H Lung A McKeown RD Mueller B Pitt ML Schulze R Sauer PU Candell E Napolitano J Tripp C Wojtsekhowski BB Lorenzon W 《Physical review letters》1995,74(5):654-657
106.
Biosynthetic studies have shown that pheomelanins, the distinctive pigments of red human hair, arise from oxidative polymerization of cysteinyldopas via 1,4-benzothiazinylalanine intermediates. However, the mode of formation of the pigment polymer remains controversial. To address this point, we have investigated the conversion of the major biosynthetic precursor 5-S-cysteinyldopa (2a) to pheomelanin under biomimetic conditions. Peroxidase/H(2)O(2) oxidation of 2a was shown to lead in the early stages to the 1,4-benzothiazinylalanine 8a, which rapidly declines with concomitant formation of a distinct pattern of oligomeric products. Reduction of the reaction mixture at this stage allowed the isolation of dimer 17 in 10% yield, along with trimers 18 and 19 in smaller amounts. A restricted rotation about the ethereal C-O bond of 17 was apparent by the presence of two NMR-detectable conformational isomers, separated by an activation energy barrier of 17.83 +/- 0.03 kcal mol(-)(1). Under similar oxidation conditions, the model catechol 2b gave the related dimers 15 and 16. The structure of oligomers 17-19, all characterized by C-C and C-O bonds between the benzothiazine units, would suggest that the peroxidase-promoted polymerization proceeds by phenol-type coupling of an aryloxy radical generated by initial one-electron oxidation of 8a. Overall, these results point to a structural model for the pheomelanin polymer which is basically different from that proposed on the basis of degradative studies. 相似文献
107.
108.
Scrimin P Tecilla P Tonellato U Verzini M Andreini BP Coutant JE Zerilli LF 《The Journal of organic chemistry》1996,61(18):6268-6272
The thermodynamics and kinetics of binding of model tripeptides epsilon-N-acetyl-alpha-N-dansyl-L-Lys-D-Ala-D-Ala (ADLAA) or alpha-N,epsilon-N-diacetyl-L-Lys-D-Ala-D-Ala (AALAA) to teicoplanin (1a) and a series of semisynthetic derivatives with (1b-f) or devoid of (2a-g) the glycidic side arms and modified at the terminal amino acids of the peptide backbone have been studied by fluorescence or UV spectroscopy. The binding process is suggested to occur via a two-step mechanism. The first, fast process is likely governed by an electrostatic interaction between the C- and N-termini of the peptide chain of the substrate and of the antibiotic, respectively, while the second slower one, accounts for the formation of the hydrogen bonds responsible of the major contribution to the overall binding energy. The binding constants with all modified derivatives are smaller than that with native teicoplanin. Larger modification of the overall binding constant are observed when the sugar residues are removed and, to a lower extent, when the N-terminus of the peptide chain is acylated. The kinetic process is very little affected by the modifications introduced. 相似文献
109.
A simple and rapid method was developed for the determination of 20 antibiotics (sulfonamides, tetacyclines, and flumequine) in honey by liquid chromatography tandem mass spectrometry. The proposed method is sensitive (limit of detection 0.5 to 10 ppb for the various antibiotics) and selective. A hydrolysis step ensures the liberation of sugar-bound sulfonamides. The approach has been used to analyze some 300 honey samples. A number of them were found to have exceeded the Swiss limit of 50 ppb. 相似文献
110.
Angelo Albert Francesco Paolo Colonna Maurizio Guerra Bianca F. Bonini Germana Mazzanti Zoltàn Dinya Gian Franco Pedulli 《Journal of organometallic chemistry》1981,221(1):47-55
The radical adducts resulting from the reaction between group IVB organometallic radicals MR3 (M = Si, Ge, Sn; R = alkyl or aryl) and a number of thioketones of the chromone and flavone series have been investigated by ESR spectroscopy. The spectral parameters obtained for these species have been compared with those of similar adducts of the corresponding ketones. Both classes of radicals adopt an orthogonal conformation, and the differences between the former and the latter paramagnetic species can be accounted for by the different electronegativity of oxygen and sulphur. the effects of substitution of the heterocyclic oxygen with a sulphur or selenium atom on the spin density distribution are likewise explained. INDO calculations have been carried out on the model systems CH2XSiH3 (X = O, S). 相似文献