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21.
DellaGreca M Iesce MR Previtera L Temussi F Zarrelli A Mattia CA Puliti R 《The Journal of organic chemistry》2002,67(25):9011-9015
Androst-4-ene-3,17-dione (1) and 17alpha-methyltestosterone (2) are dimerized in the solid-state by UV radiation. These substances were selected by a search in the CSD among the steroid enones presenting in the crystalline state an intermolecular short contact between a hydrogen alpha to a carbonyl group and the oxygen of an enone system. Dimerization occurs by transfer of the hydrogen to the oxygen and connection between the two involved carbons. Androst-4-ene-3,17-dione (1) affords dimer 3 and trimer 4, both formed by connection of the C-16 of a molecule with the C-3 of a near one. Irradiation of 17alpha-methyltestosterone (2) gives the isomeric trienones 5 and 6. These compounds are reasonably formed by dehydration of unisolated intermediate products 7 and/or 8 obtained by coupling of two molecules through a linkage between the C-2 and the C-3' carbons. The formation mechanisms of the photoproducts are satisfactory explained on the basis of the molecular arrangement of the monomers in the crystal state. Modeling of the dimeric molecules was done using molecular mechanics calculations. A single-crystal X-ray of the dimer of androst-4-ene-3,17-dione confirms the structural interpretation of spectral data. The conformer found in the solid-state agrees well with the results of molecular mechanics calculations. 相似文献
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Di Santo G Blankenburg S Castellarin-Cudia C Fanetti M Borghetti P Sangaletti L Floreano L Verdini A Magnano E Bondino F Pignedoli CA Nguyen MT Gaspari R Passerone D Goldoni A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(51):14354-14359
Scratching the surface: Formation of a monolayer of 2H-tetraphenylporphyrins (2H-TPP) on Ag(111), either by sublimation of a multilayer in the range 525-600?K or by annealing (at the same temperature) a monolayer deposited at room temperature, induces a chemical modification of the molecules. Rotation of the phenyl rings into a flat conformation is observed and tentatively explained, by using DFT calculations, as a peculiar reaction due to molecular dehydrogenation. 相似文献
24.
Falconi M Oteri F Di Palma F Pandey S Battistoni A Desideri A 《Journal of computer-aided molecular design》2011,25(2):181-194
Comparative homology modelling techniques have been used to model the protein ZnuA from Salmonella enterica serovar Typhimurium using the 3D structure of the homologous protein from Escherichia coli. These two-domain proteins bind one Zn2+ atom, with high affinity, in the inter-domain cleft and possess a histidine-rich loop in the N-terminal domain. Alternative
structures of the ZnuA histidine-rich loop, never resolved by the X-ray diffraction method, have been modelled. A model of
the apo form, one with the histidine-rich loop deleted and two alternative structures with a second zinc ion bound to the
histidine-rich loop, have been generated. In all the modelled proteins, investigated through molecular dynamics simulation,
the histidine-rich loop is highly mobile and its fluctuations are correlated to the ligand stability observed in the zinc
sites. Based on the plasticity of the histidine-rich loop and its significant effects on protein mobility a possible role
in the capture and/or transfer of the zinc ions has been suggested. 相似文献
25.
Chiara Dall’Asta Mattia Mangia Franz Berthiller Alexandra Molinelli Michael Sulyok Rainer Schuhmacher Rudolf Krska Gianni Galaverna Arnaldo Dossena Rosangela Marchelli 《Analytical and bioanalytical chemistry》2009,395(5):1335-1345
In this paper, the results obtained by five independent methods for the quantification of fumonisins B1, B2, and B3 in raw maize are reported. Five naturally contaminated maize samples and a reference material were analyzed in three different
laboratories. Although each method was validated and common calibrants were used, a poor agreement about fumonisin contamination
levels was obtained. In order to investigate the interactions among analyte and matrix leading to this lack of consistency,
the occurrence of fumonisin derivatives was checked. Significant amounts of hidden fumonisins were detected for all the considered
samples. Furthermore, the application of an in vitro digestion protocol to raw maize allowed for a higher recovery of native
fumonisins, suggesting that the interaction occurring among analytes and matrix macromolecules is associative rather than
covalent. Depending on the analytical method as well as the maize sample, only 37–68% of the total fumonisin concentrations
were found to be extractable from the samples. These results are particularly impressive and significant in the case of the
certified reference material, underlying the actual difficulties in ascertaining the trueness of a method for fumonisin determination,
opening thus an important issue for risk assessment. 相似文献
26.
Daniela Metro Mattia Papa Luigi Manasseri Teresa Gervasi Luca Campone Vito Pellizzeri 《Natural product research》2020,34(16):2255-2261
Abstract Breakfast habits affect the nutritional status and health of people, in particular children and adolescents. This is the second part a previous study about the adherence to the Mediterranean diet in a Sicilian (Italy) student population. The investigation analysed both normal weight and overweight subjects in order to understand how eating habits, number of meals and daily calorie intakes could affect their body mass indexes (BMI). The aim of this second part was to analyse the breakfast nutritional profiles of this student population. The results highlighted that breakfast was regularly consumed by a percentage ranging from a maximum of 84% (in normal subjects) to a minimum value of 57.4% (in overweight/obese students). Milk, yoghurt, sugar, bread/rusk and tea contributed as main foods to the breakfast composition. The results highlighted that subjects who consumed breakfast showed lower BMI values with significant differences between normal and overweight/obese students. 相似文献
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28.
Mattia Falconi Ruggero Gallimbeni Emanuele Paci 《Journal of computer-aided molecular design》1996,10(5):490-498
Summary Molecular dynamics (MD) simulations of 100 ps have been carried out to study the active-site behaviour of the Cu,Zn superoxide dismutase dimer (SOD) in water. The active site of each subunit was monitored during the whole simulation by calculating the distances between functional residues and the catalytic copper. The results indicate that charge orientation is maintained at each active site but the solvent accessibility varies. Analysis of the MD simulation, carried out by using the atomic displacement covariance matrix, has shown a different intra-subunit correlation pattern for the two monomers and the presence of inter-subunit correlations. The MD simulation presented here indicates an asymmetry in the two active sites and different dynamic behaviour of the two SOD subunits. 相似文献
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