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201.
Binding and distribution properties of trimethoprim (TMP) in the presence of various anionic surfactants; sodium octyl sulfate (C8SO4Na), sodium decyl sulfate (C10SO4Na), sodium lauryl sulfate (C12SO4Na), and sodium tetradecyl sulfate (C14SO4Na) has been studied by conductivity, spectrophotometry and surface tension measurements. The surface properties of anionic surfactants, that is, maximum surface excess concentration (Γ max ) and minimum area per surfactant molecule (A min ) at the air/water interface have been evaluated in the absence and presence of TMP using Gibbs adsorption isotherm. From conductivity data the ionization degree and counterion binding parameter have been obtained. Spectrophotometric experiments were used to determine binding constants of TMP to anionic micelles. With the increasing alkyl chain of surfactants, the interaction becomes stronger, which shows the importance of hydrophobic forces and incorporation of TMP molecules to the pure micelles of anionic surfactants increased. The results obtained from the surface tension and conductometric studies have been correlated with those obtained from the spectroscopic studies and binding tendency of TMP to anionic micelles followed the order as: C14SO4Na > C12SO4Na > C10SO4Na > C8SO4Na. From these results, the study of the interaction TMP in different anionic micellar solutions provided information about the characteristics of binding properties of poorly soluble drugs. 相似文献
202.
Pınar Esra Erden Nazife Aslan Alev Doğan Esin Canel Esma Kiliç 《Journal of solution chemistry》2014,43(6):1156-1166
Stoichiometric protonation constants (log10 K 1 and log10 K 2) of some aliphatic dipeptides (Gly–Tyr, Gly–Phe, Gly–Val, Gly–Leu, Gly–Thr, Gly–Met and Gly–Pro) were determined potentiometrically in 20, 40, and 60 % (v/v) 1,4-dioxane–water and dimethyl sulfoxide–water mixtures at 25.0 (±0.1) °C with an ionic strength of 0.10 mol·L?1 sodium chloride. The protonation constants were calculated with the computer program PKAS and selection of the best fit chemical models is based on the statistical parameters. The effects of solvent composition on these protonation constants are discussed to determine the factors which control these processes. It has been observed that, while the correlation between log10 K 1 and log10 K 2 with the percentages of dimethyl sulfoxide in the dimethyl sulfoxide–water mixtures are not linear, these values linearly increase as the concentration of 1,4-dioxane increases in the solvent mixtures. 相似文献
203.
204.
In the present study, Pt4(CH)n (1 ≤ n ≤ 7) and Pt4(benzene)2 metalorganic complexes have been investigated by performing density functional theory within spin polarized local density approximation, generalized gradient approximation and hybrid exchange correlation functionals in terms of the geometric properties, stability and energetics, electronic properties and chemical reactivity indexes. Locally stable isomers are distinguished from transition states by vibrational frequency analysis. Our calculations indicate that Pt4(CH)4 and Pt4benzene metal hydrocarbon complexes are the most stable structures among the studied species. 相似文献
205.
Photocatalytic Hydrogen Evolution by Oleic Acid‐Capped CdS,CdSe, and CdS0.75Se0.25 Alloy Nanocrystals
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Emre Aslan Okan Birinci Abdalaziz Aljabour Faruk Özel Ilker Akın Dr. Imren Hatay Patir Dr. Mahmut Kus Prof. Dr. Mustafa Ersoz 《Chemphyschem》2014,15(13):2668-2671
Photocatalytic generation of hydrogen by using oleic acid‐capped CdS, CdSe, and CdS0.75Se0.25 alloy nanocrystals (quantum dots) has been investigated under visible‐light irradiation by employing Na2S and Na2SO3 as hole scavengers. Highly photostable CdS0.75Se0.25 alloy nanocrystals gave the highest hydrogen evolution rate (1466 μmol h?1 g?1), which was about three times higher than that of CdS and seven times higher than that of CdSe. 相似文献
206.
In this letter we report the observation of angular-dependent Metal Enhanced Fluorescence (MEF) from fluorophores deposited onto silver island films (SiFs). When illuminated with laser light (473 nm) at angles of 45 and 90 degrees from the surface, SiFs scattered light at wide observation angles biased by the direction of the incident light. We observed angular-dependent MEF (10-fold) from FITC-HSA immobilized onto the SiFs, again slightly biased with respect to the direction of the incident light. We also measured the photostability of FITC from the back of the glass substrate at angles of 225 and 340 degrees. 相似文献
207.
KP Birin YG Gorbunova AY Tsivadze 《Dalton transactions (Cambridge, England : 2003)》2012,41(32):9672-9681
New heteroleptic triple-decker terbium complexes of general structure [Br(4)TPP]Tb[(15C5)(4)Pc]Tb[Br(4)TPP] (Tb-TD) and [Br(4)TPP]Tb[(15C5)(4)Pc]Tb[(15C5)(4)Pc] (Tb-TD*) (Br(4)TPP = tetrakis-meso-(4-bromophenyl)-porphyrin, (15C5)(4)Pc = tetra-(15-crown-5)-phthalocyanine) are synthesized with 48% and 57% yields, respectively. The triple-decker complexes were prepared by interaction of generated in situ terbium monoporphyrinate [Br(4)TPP]Tb(acac) and corresponding double-decker precursors. The heteroleptic double-decker precursor [Br(4)TPP]Tb[(15C5)(4)Pc] was prepared for the first time in a two step one-pot synthesis. No ligand scrambling was observed in the synthesis of Tb-TD, while 4% scrambling was determined in the case of Tb-TD*. High yields of target triple-decker complexes were achieved despite the presence of electron-donating crown-ether fragments with low thermal stability at the phthalocyanine deck. Analysis of lanthanide-induced paramagnetic shifts of protons of Tb-TD together with data of previously reported La, Pr, Nd and Eu analogues allowed precise separation of contributions of contact and dipolar lanthanide terms as well as verification of isostructurality of complexes within the series. 相似文献
208.
In this short paper we report the interactions of silver island films with chemiluminescing species. Our findings show that silver island films can increase the detectability of chemiluminescent reactions/species, with an approximately 5-fold increase in signal intensity. This finding not only suggests the use of silver nanostructures to amplify chemiluminscent signatures in assay platforms, and therefore increase the detectability of analytes or biospecies, but more importantly, suggests that surface plasmons can be directly excited by chemically induced electronically excited molecules. This finding is of significance towards our understanding of fluorophore–metal interactions, a relatively new near-field fluorescence concept, recently named metal-enhanced fluorescence and also radiative decay engineering. 相似文献
209.
Metal-enhanced fluorescence-based RNA sensing 总被引:1,自引:0,他引:1
Aslan K Huang J Wilson GM Geddes CD 《Journal of the American Chemical Society》2006,128(13):4206-4207
210.
The stoichiometric protonation constants of some α-amino acid esters (glycine methyl ester, glycine t-butyl ester, l-valine methyl ester, l-valine ethyl ester, l-valine t-butyl ester, l-serine methyl ester, l-serine ethyl ester, l-leucine methyl ester, l-leucine ethyl ester, l-leucine t-butyl ester, l-alanine methyl ester, l-alanine benzyl ester, l-phenylalanine methyl ester, l-phenylalanine ethyl ester, and l-phenylalanine t-butyl ester) in water and 20%, 40%, and 60% (v/v) 1,4-dioxane–water mixtures have been determined at an ionic strength of
0.10 mol⋅L−1 NaCl and at 25.0±0.1 °C under a nitrogen atmosphere. A potentiometric method was used and the calculation of the protonation
constants has been carried out using the BEST computer program. The results were discussed in terms of macroscopic properties
of the mixed solvent. The stoichiometric protonation constants were influenced by changes in solvent composition and their
variations were discussed in terms of preferential solvation. Also, knowledge the protonation constant of α-amino acid esters will be helpful when determining the microscopic equilibrium constants of their corresponding amino acids. 相似文献