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111.
Intrinsic fluorescence of peptides and proteins is extensively used to monitor their specific interactions with several natural and synthetic molecules known to have wide-ranging beneficial or detrimental effects on health. A consequence of these interactions would be a significant decrease of the fluorescence emission intensity of Tyrosine (Tyr) and/or Tryptophan (Trp) residues in the protein due to structural rearrangements of proteic microenvironment. However fluorescence quenching can be also caused by “trivial” artefacts. In this study we examined the effect of Ferulic acid (FA) on Tyr fluorescence. FA is a natural anti-oxidant suggested to bind to and to modify the structural properties of several proteins thus altering their biological activities. Fluorescence spectroscopy experiments on Tyr and on proteins containing Tyr and no Trp like beta amyloid peptides and Insulin were performed. Our results suggest that Tyr fluorescence loss can mainly result from an inner filter effect rather than from specific interactions with FA. 相似文献
112.
Kamel Rezgui Riadh Othmen Antonella Cavanna Hosni Ajlani Ali Madouri Meherzi Oueslati 《Journal of Raman spectroscopy : JRS》2013,44(11):1529-1533
InAs self‐assembled quantum dots (QDs) were grown by molecular beam epitaxy on (001) GaAs substrate. Uncapped and capped QDs with GaAs and graphene layers were studied using atomic force microscopy and Raman spectroscopy. Graphene multi‐layer was grown by chemical vapor deposition and transferred on InAs/GaAs QDs. It is well known that the presence of a cap layer modifies the size, shape, and density of the QDs. According to the atomic force microscopy study, in contrast to the GaAs capped sample, which induce a dramatic decrease of the density and height of dots, graphene cap layer sample presents a slight influence on the surface morphology and the density of the islands compared with the uncapped one. The difference shown in the Raman spectra of the samples is due to change of strain and alloy disorder effects on the QDs. Residuals strain and the relaxation coefficients have been investigated. All results confirm the best crystalline quality of the graphene cap layer dots sample relative to the GaAs capped one. So graphene can be used to replace GaAs in capping InAs/GaAs dots. To our knowledge, such study has not been carried out until now. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
113.
Valentina Noemi Madia Daniela De Vita Davide Ialongo Valeria Tudino Alessandro De Leo Luigi Scipione Roberto Di Santo Roberta Costi Antonella Messore 《Molecules (Basel, Switzerland)》2021,26(15)
Growing attention to environmental protection leads food industries to adopt a model of “circular economy” applying safe and sustainable technologies to recover, recycle and valorize by-products. Therefore, by-products become raw material for other industries. Tomato processing industry produces significant amounts of by-products, consisting of skins and seeds. Tomato skin is very rich in lycopene, and from its seeds, high nutritional oil can be extracted. Alternative use of the two fractions not only could cut disposal costs but also allow one to extract bioactive compounds and an oil with a high nutritional value. This review focused on the recent advance in extraction of lycopene, whose beneficial effects on health are widely recognized. 相似文献
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Siani G Angelini G De Maria P Fontana A Pierini M 《Organic & biomolecular chemistry》2008,6(22):4236-4241
The rates of tautomerization of 2-nitrocyclohexanone (2-NCH) have been measured spectrophotometrically at 25.0 +/- 0.1 degrees C in several organic aprotic solvents and their binary mixtures. In cyclohexane the reaction is effectively catalyzed by bases and inhibited by acids while the so-called "spontaneous reaction" appears essentially due to autocatalysis. Apparent second order rate constants (k(app)(B)) for the reaction catalyzed by triethylamine (TEA) and pyridine (Pyr) have been obtained. From the experimental k(app)(B) values rate constants for the enolization (k(1)(B)) and ketonization (k(-1)(B)) reactions have been calculated. A Kamlet-Taft type linear solvation energy relationship (LSER) adequately accounts for the observed solvent effects. Activation parameters for both reactions show that solvent effects are mainly entropic in origin and that there is a shift of the transition state from a ketone-like to an enol-like structure on passing from less to more polar solvents. 相似文献
118.
Antonella Fontana Paolo Lo Meo Stefano Morganti Egon Rizzato Romina Zappacosta 《Tetrahedron》2008,64(4):733-740
Rate constants, kA,R, for the rearrangement of the (Z)-phenylhydrazones (1a-e) of a series of 5-alkyl-3-benzoyl-1,2,4-oxadiazoles substituted at C(5) with linear alkyl chains of different length (from C4 up to C12) into the relevant 4-acylamino-2,5-diphenyl-1,2,3-triazoles (2a-e) have been measured in dioxan/water in the base-catalyzed region (pS+ 10.5-12.6). For each substrate log kA,R are linearly related to pS+. The significant decrease of the slopes of these straight lines (from 0.96 down to 0.78) upon increasing the length of the linear alkyl chain at C(5) and that of the reactivity (down to 14-26%) upon increasing the substrate concentration suggest a decrease of the polarity of the ‘actual’ reaction medium and provide indirect evidence of the tendency of the substrates (Z)-1a-e to self-assemble. To confirm the above outcome direct evidence of the formation of self-assemblies in solution were obtained from 1H NMR and spectrofluorimetry measurements while ESI-MS experiments point out the presence of aggregated substrates also in the gas phase. 相似文献
119.
The Et(3)N-assisted addition of beta-ketoester 3 to MVK in chloroform is catalyzed with high turnover efficiency by the phenyl-substituted uranyl-salophen compound 2b but not by the parent compound 1b. A plausible mechanism is suggested, involving concomitant nucleophilic attack at the beta-carbon and hydrogen bonding between the Et(3)NH(+) countercation and the carbonyl oxygen of the s-cis conformation of the enone reactant. The role of the van der Waals interactions with the aromatic side arm of 2b as a crucial driving force for catalysis is discussed. 相似文献
120.
Dr. Michela Parafioriti Dr. Minghong Ni Maurice Petitou Dr. Courtney J. Mycroft-West Dr. Timothy R. Rudd Dr. Neha S. Gandhi Prof. Vito Ferro Prof. Jeremy E. Turnbull Dr. Marcelo A. Lima Dr. Mark A. Skidmore Prof. David G. Fernig Dr. Edwin A. Yates Dr. Antonella Bisio Dr. Marco Guerrini Dr. Stefano Elli 《Chemistry (Weinheim an der Bergstrasse, Germany)》2023,29(1):e202202599
Infection of host cells by SARS-CoV-2 begins with recognition by the virus S (spike) protein of cell surface heparan sulfate (HS), tethering the virus to the extracellular matrix environment, and causing the subunit S1-RBD to undergo a conformational change into the ‘open’ conformation. These two events promote the binding of S1-RBD to the angiotensin converting enzyme 2 (ACE2) receptor, a preliminary step toward viral-cell membrane fusion. Combining ligand-based NMR spectroscopy with molecular dynamics, oligosaccharide analogues were used to explore the interactions between S1-RBD of SARS CoV-2 and HS, revealing several low-specificity binding modes and previously unidentified potential sites for the binding of extended HS polysaccharide chains. The evidence for multiple binding modes also suggest that highly specific inhibitors will not be optimal against protein S but, rather, diverse HS-based structures, characterized by high affinity and including multi-valent compounds, may be required. 相似文献