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71.
Tin-free Giese reaction and the related radical carbonylation process proceeded efficiently in the presence of sodium cyanoborohydride and tetrabutylammonium cyanoborohydride. The reaction took place chemoselectively at the carbon-iodine bond but not at the carbon-bromine and carbon-chlorine bonds. The iodine atom transfer followed by hydride reduction of the resulting carbon-iodine bond is proposed as a possible mechanism. 相似文献
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75.
Masahiro Yoshita Yuhei Hayamizu Hidefumi Akiyama Loren N. Pfeiffer Ken W. West 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):230
A T-shaped single quantum-wire laser with high spatial uniformity has been fabricated by a cleaved-edge overgrowth method with molecular beam epitaxy and a growth-interrupt annealing technique. Using micro-photoluminescence imaging and spectroscopy, we confirmed the formation of a spatially uniform quantum wire over 20 μm long without hetero-interface roughness. By optical pumping, we achieved single-mode lasing from the ground state of the single quantum wire at a threshold excitation power as low as 5 mW at 5 K. 相似文献
76.
The dynamic heat capacity of nematic liquid crystals just above the clearing point is calculated as an extension of our previous theory of static heat capacity. The present theory explains semi-quantitatively the available experimental results of anomalous ultrasonic absorption and dispersion. 相似文献
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78.
Haru Ogawa Hiroshi Morita Satoko Suemura Taiji Imoto Yasuyoshi Nogami Toshitaka Koga Yujiro Sakuragi Izumi Miyamoto Hidefumi Kato Yōichi Taniguchi 《Tetrahedron letters》1985,26(45):5567-5570
The titled annulenone 1 could be converted into new annulenones 3 and 8 by carbonyl transposition reactions. Compound 8 can be regarded as the first 14π hydroxy-enone as a higher homolog of tropolone (6π) and hydroxy[11]annulenones (10π), and was proved to be aromatic. 相似文献
79.
Hidefumi Hirai Makoto Komiyama 《Journal of polymer science. Part A, Polymer chemistry》1974,12(12):2701-2719
The equilibrium constants for the complex formation between stannic chloride and methyl methacrylate were determined in n-hexane–toluene solution at 0, ?20, and ?30°C by using the absorption band at 350 nm. Continuous variation plots at ?20°C in n-hexane based on the 1H-chemical shifts definitely show a 1:1 interaction between the coordinated methyl methacrylate and styrene or toluene. The magnitudes of the shifts for the four groups of protons in methyl methacrylate are found to be in a specific ratio in common with the 1:2 complex–styrene or -toluene system. The equilibrium constants for the ternary molecular complex formation between the 1:2 complex and styrene or toluene were determined in n-hexane in the temperature range ?50 to +20°C by use of the chemical shifts. The concentrations of the complex species in the alternating copolymerization solutions were estimated by use of the equilibrium constants. There is a linear relationship between the enthalpy and the entropy changes for the ternary molecular complex formation, which is governed by the enthalpy factor. The specificity of the interactions indicates a specific time-averaged orientation of benzene ring to the coordinated methyl methacrylate. The effects of the coordination of methyl methacrylate to stannic chloride were discussed on the basis of results of 13C-NMR spectroscopy. 相似文献
80.
Tarui N Nakahama K Nagano Y Izawa M Matsumoto K Kori M Nagata T Miki T Yukimasa H 《Chemical & pharmaceutical bulletin》2002,50(1):59-65
Microbial enantioselective ester hydrolysis for the preparation of optically active (3R,5S)-(-)-5-phenyl-4,1-benzoxazepine-3-acetic acid derivatives as potent squalene synthase inhibitors was investigated. Pseudomonas diminuta and Pseudomonas taetrolens hydrolyzed the racemic ethyl ester of the 5-(2-chlorophenyl) analogue to yield the (-)-carboxylic acid with excellent enantiomeric excess (>99% ee). We found that the (-)-enantiomer was an active inhibitor. Bulkiness of the ester moiety did not affect the enantioselectivity but did affect reactivity. The racemic ethyl ester of the 5-(2-methoxyphenyl) analogue, 5-(2,3-dimethoxyphenyl) analogue and 5-(2,4-dimethoxyphenyl) analogue were also hydrolyzed with Pseudomonas taetrolens to afford enantiomerically pure (-)-carboxylic acids in large scale. As another route to (3R,5S)-(-)-7-chloro-5-(2,3-dimethoxyphenyl)-1-neopentyl-2-oxo-1,2,3,5-tetrahydro-4,1-benzoxazepine-3-acetic acid [(-)-1c], the earlier intermediate (-)-2-amino-5-chloro-alpha-(2,3-dimethoxyphenyl)benzyl alcohol [(-)-12] was successfully obtained by asymmetric hydrolysis of (+/-)-5-chloro-alpha-(2,3-dimethoxyphenyl)-2-pivaloylaminobenzyl acetate with Pseudomonas sp. S-13 with >99% ee in kilogram scale followed by alkaline treatment. The product (-)-12 was converted to (-)-1c without racemization. 相似文献