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排序方式: 共有247条查询结果,搜索用时 15 毫秒
241.
Lie algebras graded by finite irreducible reduced root systems have been classified up to central extensions by Berman and
Moody, Benkart and Zelmanov, and Neher. In this paper we determine the central extensions of these Lie algebras and hence
describe them completely up to isomorphism.
Received: 22 May 1997 / in final form: 13 January 1999 相似文献
242.
Dais P Stefanaki I Fragaki G Mikros E 《The journal of physical chemistry. B》2005,109(35):16926-16936
Two-dimensional NMR spectroscopy has been used for a complete assignment of the proton and carbon-13 spectra of the metabolite from Aspergillus ochraceus, ochratoxin A. In addition, phase-sensitive nuclear Overhauser effect spectrometry experiments and computational molecular modeling (MM2 and MMFF force field programs) have been employed to examine the conformational properties of ochratoxin A in chloroform solutions. Particular attention has been given to intramolecular hydrogen-bonding formation involving the phenolic group on dihydroisocoumarin, which may be responsible for the toxic mechanism of ochratoxin A. 相似文献
243.
244.
An integrated analytical method for the simultaneous determination of 4-n-nonylphenol (4-n-NP), nonylphenol monoethoxylate (NP1EO), nonylphenol diethoxylate (NP2EO), bisphenol A (BPA) and triclosan (TCS) in wastewater (dissolved and particulate phase) and sewage sludge was developed based on gas chromatography-mass spectrometry. Chromatographic analysis was achieved after derivatization with bis(trimethylsilyl)trifluoroacetamide (BSTFA). Extraction from water samples was performed by solid-phase extraction (SPE). The optimization of SPE procedure included the type of sorbent and the type of the organic solvent used for the elution. Referred to solid samples, the target compounds were extracted by sonication. In this case the optimization of the extraction procedure included the variation of the amount of the extracted biomass, the duration and the temperature of sonication and the type of the extraction organic solvent. The developed extraction procedures resulted in good repeatability and reproducibility with relative standard deviations (RSDs) less than 13% for all the tested compounds for both types of samples. Satisfactory recoveries were obtained (>60%) for all the compounds in both liquid and solid samples, except for 4-n-NP, which gave recoveries up to 35% in wastewater samples and up to 63% in sludge samples. The limits of detection (LODs) of the target compounds varied from 0.03 (4-n-NP) to 0.41 microg l(-1) (NP2EO) and from 0.04 (4-n-NP) to 0.96 microg kg(-1) (NP2EO) for liquid and solid samples, respectively. The developed methods were successfully applied to the analysis of the target compounds in real samples. 相似文献
245.
Vasiliki Vakali Michail Papadourakis Nikitas Georgiou Nikoletta Zoupanou Dimitrios A. Diamantis Uro Javornik Paraskevi Papakyriakopoulou Janez Plavec Georgia Valsami Andreas G. Tzakos Demeter Tzeli Zoe Cournia Thomas Mauromoustakos 《Molecules (Basel, Switzerland)》2022,27(17)
Quercetin (QUE) is a well-known natural product that can exert beneficial properties on human health. However, due to its low solubility its bioavailability is limited. In the present study, we examine whether its formulation with two cyclodextrins (CDs) may enhance its pharmacological profile. Comparative interaction studies of quercetin with 2-hydroxyl-propyl-β-cyclodextrin (2HP-β-CD) and 2,6-methylated cyclodextrin (2,6Me-β-CD) were performed using NMR spectroscopy, DFT calculations, and in silico molecular dynamics (MD) simulations. Using T1 relaxation experiments and 2D DOSY it was illustrated that both cyclodextrin vehicles can host quercetin. Quantum mechanical calculations showed the formation of hydrogen bonds between QUE with 2HP-β-CD and 2,6Μe-β-CD. Six hydrogen bonds are formed ranging between 2 to 2.8 Å with 2HP-β-CD and four hydrogen bonds within 2.8 Å with 2,6Μe-β-CD. Calculations of absolute binding free energies show that quercetin binds favorably to both 2,6Me-β-CD and 2HP-β-CD. MM/GBSA results show equally favorable binding of quercetin in the two CDs. Fluorescence spectroscopy shows moderate binding of quercetin in 2HP-β-CD (520 M−1) and 2,6Me-β-CD (770 M−1). Thus, we propose that both formulations (2HP-β-CD:quercetin, 2,6Me-β-CD:quercetin) could be further explored and exploited as small molecule carriers in biological studies. 相似文献
246.
Samuel Quinn E. Stephen Davies Nicholas Pearce Callum Rosenberg Constance R. Pfeiffer Georgia R. F. Orton Neil R. Champness 《Molecules (Basel, Switzerland)》2022,27(24)
Donor-acceptor dyads and triads comprising core-substituted naphthalene diimide (NDI) chromophores and either phenothiazine or phenoxazine donors are described. Synthesis combined with electrochemical and spectroelectrochemical investigations facilitates characterisation of the various redox states of these molecules, confirming the ability to combine arrays of electron donating and accepting moieties into single species that retain the redox properties of these individual moieties. 相似文献
247.
Baardman Lennart Cristian Rares Perakis Georgia Singhvi Divya Skali Lami Omar Thayaparan Leann 《Mathematical Programming》2023,197(1):1-26
Mathematical Programming - In this paper, we present a new framework of bi-level unconstrained minimization for development of accelerated methods in Convex Programming. These methods use... 相似文献