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Effect of methoxyl groups on the NMR spectra: configuration and conformation of natural and synthetic indanic and tetralinic structures 下载免费PDF全文
Beatriz Lantaño José M. Aguirre Eleonora V. Drago Diego J. de la Faba Nicolás Pomilio Jorge D. Mufato 《Magnetic resonance in chemistry : MRC》2017,55(7):619-633
Here, we studied the influence of the methoxyl groups attached at C‐7 and C‐2′ of natural and synthetic 1‐arylindanes on the chemical shift of the signal of bibenzylic hydrogen and carbon atoms and J1,2 coupling constants. This influence was also analysed in natural 1‐aryltetralins and related compounds that possess methoxyl and/or hydroxyl groups bound at C‐8 and C‐2′. The methoxyl groups attached at C‐7 in indanes or at C‐8 in tetralins produce a deshielding signal at H‐1 and shield at C‐1 and a strong decrease in the value of J1,2 due to the pseudoequatorial location adopted by the aryl group bound at C‐1, avoiding an ‘A1,3 strain’. Furthermore, compounds with hydroxyl or methoxyl groups in C‐2′, in the absence of substituents of C‐7 or C‐8, present a strong deshielding signal at H‐1, strong shield of the C‐1 signal and a decrease in the value of J1,2. This is attributed to the stereoelectronic effects of the methoxyl or hydroxyl groups, which we have called ‘Asarone effect’. NOESY experiments were conducted to confirm the configuration and conformation of some of the compounds included in this work. This study shows that both effects, A1,3 strain and Asarone effect, must be taken into account when the structure of natural indanes and tetralins is analysed by using 1H‐NMR and 13C‐NMR spectra. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Igor I. Patsanovsky Eleonora A. Ishmaeva 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4)
Abstract The influence of classical systems connected with phosphorus atom: >P(Y)-C(R)=C<, >P(Y)-C[tbnd]S- and unusual ones, -P=E and P[tbnd]S- on spatial and electronic structure of or-ganophosphorus compounds has been considered. On the complex analysis ground of polarity and polarizability data, obtained for model olefines, imines, acetylenes and nitriles the existence of nonformal similarity between this compounds classes has been demonstrated. It is reflected in analogy of conformational behaviour and electron effects, realized with participation of multiple carbon, nitrogen and phosphorus bonds: 相似文献
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Mauro Formica Luca Giorgi Eleonora Macedi Giovanni Piersanti Maria Antonietta Varrese 《Supramolecular chemistry》2013,25(6):365-379
The synthesis and anion binding studies of the new neutral receptor 1,1′-(2,2′-(4,10-dimethyl-1,4,7,10-tetraazacyclododecane-1,7-diyl)bis(2-oxoethane-2,1-diyl))bis(3-(3,5-bis(trifluoromethyl)phenyl)urea) (L1) are reported. L1 is a macrocyclic ligand containing the 3,5-trifluoromethylphenylureido-binding fragment attached as a side arm on the tetraazacyclododecane. L1 is soluble in numerous organic solvents; the binding properties of L1 towards several simple anions (G) were investigated by NMR, UV–vis and fluorescence techniques in DMSO and CH3CN solutions. L1 is able to bind F? , Cl? and AcO? in both solvents; in addition, it binds Br? in CH3CN. Fluoride shows the highest constant values in the halide series (F? > Cl? > Br? ) and AcO? is the most strongly bound among all the anions investigated. L1 is able to signal the presence of the anions in solution by fluorescence change; in the case of acetate, this occurs in the visible range. 相似文献
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Alessio Mezzi Eleonora Bolli Saulius Kaciulis Matteo Mastellone Marco Girolami Valerio Serpente Alessandro Bellucci Riccardo Carducci Riccardo Polini Daniele M. Trucchi 《Surface and interface analysis : SIA》2020,52(12):968-974
Thin films of barium fluorides with different thicknesses were deposited on GaAs substrate by electron beam evaporation. The aim of the work was to identify the best growth conditions for the production of coatings with a low work function suitable for the anode of hybrid thermionic-photovoltaic (TIPV) devices. The chemical composition and work function φ of the films with different thicknesses were investigated by X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). The lowest value of φ = 2.1 eV was obtained for the film with a thickness of ~2 nm. In the valence band spectra of the films at low kinetic energy, near the cutoff, a characteristic peak of negative electron affinity was present. This effect contributed to a further reduction of the film's work function. 相似文献
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Eleonora Bolli Alessandra Fava Saulius Kaciulis Alessio Mezzi Roberto Montanari Alessandra Varone 《Surface and interface analysis : SIA》2020,52(12):1089-1092
Cr martensitic steels are promising materials for structural applications in future nuclear fusion reactors. Because the embrittlement after tempering treatments can be a serious problem, the fracture mode of a steel with 10.5 wt% of Cr treated at 700°C for 18 h has been investigated through Charpy tests in the temperature range from −100°C to +150°C. X-ray photoelectron spectroscopy (XPS) analyses carried out on the fracture surfaces evidenced the segregation of Cr in both ductile and brittle (quasicleavage) fields. The unexpected result indicates that Cr segregation weakens the atomic bonds; thus, the fracture path in both the cases corresponds to the zones with higher Cr content. 相似文献
18.
Eleonora Truzzi Mohamed Aymen Chaouch Gaia Rossi Lorenzo Tagliazucchi Davide Bertelli Stefania Benvenuti 《Molecules (Basel, Switzerland)》2022,27(5)
The main focus of the current research was the characterization of the by-products from the steam distillation of Lavandula angustifolia Mill. (LA) and Lavandula x intermedia Emeric ex Loisel (LI) aerial parts, as they are important sources of bioactive compounds suitable for several applications in the food, cosmetic, and pharmaceutical industries. The oil-exhausted biomasses were extracted and the total polyphenol and flavonoid contents were, respectively, 19.22 ± 4.16 and 1.56 ± 0.21 mg/g for LA extract and 17.06 ± 3.31 and 1.41 ± 0.10 mg/g for LI extract. The qualitative analysis by liquid chromatography-electrospray tandem mass spectrometry (HPLC-ESI-MS) revealed that both the extracts were rich in phenolic acids and glycosylated flavonoids. The extracts exhibited radical scavenging, chelating, reducing activities, and inhibitory capacities on acetylcholinesterase and tyrosinase. The IC50 values against acetylcholinesterase and tyrosinase were, respectively, 5.35 ± 0.47 and 5.26 ± 0.02 mg/mL for LA, and 6.67 ± 0.12 and 6.56 ± 0.16 mg/mL for LI extracts. In conclusion, the oil-exhausted biomasses demonstrated to represent important sources of bioactive compounds, suitable for several applications in the food, cosmetic, and pharmaceutical industries. 相似文献
19.
Dr. Daniele Paderni Dr. Eleonora Macedi Dr. Larisa Lvova Dr. Gianluca Ambrosi Prof. Mauro Formica Prof. Luca Giorgi Prof. Roberto Paolesse Prof. Vieri Fusi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(49):e202201062
A new series of ligands containing the 2-(2-hydroxy-3- naphthyl)-4-methylbenzoxazole (HNBO) fluorophore showed selectivity for Mg2+ ions, without the interference of Ca2+. The most promising representative L3 resulted the best performing sensor for Mg2+ both in solution and embedded in an all-solid-state optode, especially towards real samples of drinkable water. 相似文献
20.
Giampiero Mei Almerinda Di Venere Eleonora Nicolai Nicola Rosato Alessandro Finazzi Agro' 《Journal of fluorescence》2003,13(1):33-39
Tryptophan fluorescence is extremely useful to monitor structural conformational transitions in proteins. Denaturant-induced unfolding of azurin and ascorbate oxidase has been studied by dynamic fluorescence measurements in the frequency domain and the results have been interpreted in terms of continuous distribution of lifetimes. The data add new information on the unfolding mechanism that was previously analyzed by steady-state emission spectroscopy. In particular, the existence of multiple, parallel unfolding pathways may be envisaged and correlated, in both cases, to the two protein structures. The effect of metal depletion has been also characterized by fluorescence lifetime measurements. In the case of azurin, a monomeric protein, the data demonstrate that copper removal yields a totally different unfolding pathways with respect to the holo protein, indicating that metal ion plays a fundamental structural role in the wild type, native protein. In the case of ascorbate oxidase a dimer of 140 kDa, only minor effects have been detected by copper removal. However, the analysis of the fluorescence decay in presence of different amounts of guanidinium hydrochloride gives new important insights on the unfolding intermediates. In particular the data support the hypothesis of a partial exposure of an outer layer of dimer at intermediate denaturant concentration. This ability of dynamic fluorescence to pinpoint the presence of structural micro-heterogeneity in the unfolding pathways of proteins demonstrates the greater power of this technique compared to the most commonly used steady-state measurements. 相似文献