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41.
Opening Enediyne Scissors Wider: pH‐Dependent DNA Photocleavage by meta‐Diyne Lysine Conjugates 下载免费PDF全文
Photochemical activation of meta‐diynes incapable of Bergman and C1–C5 cyclizations still leads to efficient double‐strand DNA cleavage. Spatial proximity of the two arylethynyl groups is not required for efficient DNA photocleavage by the enediyne‐lysine conjugates. Efficiency of the cleavage is a function of the external pH and DNA damage is strongly enhanced at pH < 7. The pH‐dependence of the DNA photocleavage activity stems from the protonation states of lysine amino groups, the internal electron donors responsible for intramolecular PET quenching and deactivation of the photoreactive excited states. DNA‐binding analysis suggests intercalative DNA binding for phenyl substituted conjugate and groove binding for TFP‐substituted conjugate. Additional insights in the possible mechanism for DNA damage from the ROS (Reactive Oxygen Species) scavenger experiments found that generation of singlet oxygen is partially involved in the DNA damage. 相似文献
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(13)CO exchange studies of racemization catalyst (η(5)-Ph(5)C(5))Ru(CO)(2)Cl and (η(5)-Ph(5)C(5))Ru(CO)(2)(Ot-Bu) by (13)C NMR spectroscopy are reported. CO exchange for the active catalyst form, (η(5)-Ph(5)C(5))Ru(CO)(2)(Ot-Bu) is approximately 20 times faster than that for the precatalyst (η(5)-Ph(5)C(5))Ru(CO)(2)Cl. An inhibition on the rate of racemization of (S)-1-phenylethanol was observed on addition of CO. These results support the hypothesis that CO dissociation is a key step in the racemization of sec-alcohols by (η(5)-Ph(5)C(5))Ru(CO)(2)Cl, as also predicted by DFT calculations. 相似文献
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Azabicyclic [3.1.0] and [4.1.0] Kulinkovich products underwent a facile reduction/fragmentation to afford a variety of 3-piperidinones and 3-azepinones, respectively, in the presence of catalytic palladium on carbon and formic acid in an atmosphere of hydrogen. 相似文献
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Lingam Venkata Reddy Mamatha Nakka Alishetty Suman Soumen Ghosh Madeleine Helliwell Khagga Mukkanti Alok Kumar Mukherjee Sarbani Pal 《Journal of heterocyclic chemistry》2011,48(3):555-562
Reduction of nimesulide followed by treating the N‐acyl derivative of resulting arylamine with Vilsmeier‐Haack reagent provided novel 2‐chloro‐3‐formylquinoline derivatives. The construction of quinoline ring using Vilsmeier‐Haack reagent afforded an unexpected compound, N‐(2‐chloro‐3‐formyl‐7‐phenoxy quinolin‐6‐yl)formamide, in addition to the expected product. The structure of this unexpected quinoline derivative was established via single‐crystal X‐ray analysis and its formation could be explained by an unprecedented N‐S bond cleavage under Vilsmeier‐Haack reaction conditions. The 2‐chloro‐3‐formylquinoline derivatives obtained were converted to a number of corresponding Schiff bases with potential pharmacological importance. J. Heterocyclic Chem., 2011. 相似文献
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Samuel Cheeseman Z. L. Shaw Jitraporn Vongsvivut Russell J. Crawford Madeleine F. Dupont Kylie J. Boyce Sheeana Gangadoo Saffron J. Bryant Gary Bryant Daniel Cozzolino James Chapman Aaron Elbourne Vi Khanh Truong 《Molecules (Basel, Switzerland)》2021,26(13)
Biofilms are assemblages of microbial cells, extracellular polymeric substances (EPS), and other components extracted from the environment in which they develop. Within biofilms, the spatial distribution of these components can vary. Here we present a fundamental characterization study to show differences between biofilms formed by Gram-positive methicillin-resistant Staphylococcus aureus (MRSA), Gram-negative Pseudomonas aeruginosa, and the yeast-type Candida albicans using synchrotron macro attenuated total reflectance-Fourier transform infrared (ATR-FTIR) microspectroscopy. We were able to characterise the pathogenic biofilms’ heterogeneous distribution, which is challenging to do using traditional techniques. Multivariate analyses revealed that the polysaccharides area (1200–950 cm−1) accounted for the most significant variance between biofilm samples, and other spectral regions corresponding to amides, lipids, and polysaccharides all contributed to sample variation. In general, this study will advance our understanding of microbial biofilms and serve as a model for future research on how to use synchrotron source ATR-FTIR microspectroscopy to analyse their variations and spatial arrangements. 相似文献
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Résumé Les spectres d'absorption infrarouge de l'acétate de méthyle et de l'acétate de méthyle perdeutéré ont été étudiés de 300 à 4000 cm–1. La comparaison des spectres a permis l'attribution certaine des bandes de l'acétate de méthyle, en particulier de la bande observée vers 1245 cm–1 qui correspond à une vibration concernant la liaison C-O.
Summary The infrared absorption spectra of methyl acetate and the perdeuterated methyl acetate have been studied from 300 to 4000 cm–1. The comparison of the spectra has made it possible to attribute certain of the bands of methyl acetate, in particular the band observed around 1245 cm–1, which corresponds to a vibration involving the C-O bond.
Zusammenfassung Die Absorptionsspektren von Methylacetat der Zusammensetzung CH3COOCH3 und CD3COOCD3 im Infrarot wurden zwischen 300 und 4000 cm–1 untersucht. Der Vergleich dieser Spektren führte zur sicheren Zuordnung der Banden des Methylacetats, insbesondere der bei 1245 cm–1 gelegenen Bande, die der C-O-Bindung zugehört.相似文献