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171.
In the enantiodifferentiating supramolecular photocyclodimerization of 2-anthracenecarboxylate using gamma-cyclodextrin with a dicationic side chain, a dramatic switching of the product selectivity and a significant enhancement of the enantiomeric excess were achieved by introducing a flexible dicationic sidearm to native gamma-cyclodextrin and also by lowering the temperature and solvent polarity. 相似文献
172.
Kakinoki K Yamane K Igarashi M Yamamoto M Teraoka R Matsuda Y 《Chemical & pharmaceutical bulletin》2005,53(7):811-815
To characterize the photocatalytic activity of TiO2 via solid-state reaction, the relationship between the physicochemical properties and photocatalytic activity of TiO2 was investigated and estimated from the results of photodegradation of nisoldipine. The photodegradation of nisoldipine was significantly enhanced by addition of TiO2. Two degradation products, nitroso-phenylpyridine derivative and nitro-phenylpyridine derivative, were formed. The degree of photocatalytic activity of TiO2 was quite different between the various types of TiO2 investigated, even when the crystalline phase was the same. As a result of the investigations into the relationship between the photocatalytic activity and physicochemical properties of TiO2, it was found that for the rutile form the photocatalytic activity has good correlation with specific surface area of TiO2, but poor correlation with water loss on drying of TiO2. However, for the anatase form, the photocatalytic activity has good correlation with water loss on drying of TiO2, but poor correlation with specific surface area. Moreover, it was found that the crystallinity of TiO2 has a moderate correlation with the photocatalytic activity of both crystal forms of TiO2. These results suggest that a degree of photocatalytic activity of TiO2 depends on the various physicochemical properties of each type of TiO2 investigated. 相似文献
173.
Yoshihisa Kurasawa Ho Sik Kim Ritsuko Katoh Tae Kawano Atsushi Takada Yoshihisa Okamoto 《Journal of heterocyclic chemistry》1991,28(3):787-792
The reaction of the hydrazones 5a-c with 2-chloroacrylonitrile produced the 1,2-diazepino[3,4-b]quinoxaline hydrochlorides 6a-c , which were transformed into the 5,6,7,13-tetrahydro-5,14-methano-16-oxo-1,5,6-benzoxadiazonino[3,4-b]quinoxalines 7a-c , respectively. The oxidation of 7a-c with diethyl azodicarboxylate afforded the 7,13-dihydro-5,14-methano-16-oxo-1,5,6-benzoxadiazonino[3,4-b]quinoxalines 8a-c , respectively. Compounds 7a-c and 8a-c were also obtained by a one-pot synthesis from 5a-c and 6a-c , respectively. 相似文献
174.
7-Amino-3-β-D-ribofuranosyl-3H-imidazo[4,5-b]pyridine (III, 1-deazaadenosine) was synthesized in 32% yield from the diacetyl derivative prepared from 7-aminoimidazo[4,5-b ]pyridine (1-deazaadenine) and 1,2,3,5-tetra-O-acetyl-β-D-ribose by the fusion method. A synthesis of 7-amino-4-b?-D-ribofuranosyl-4H-imidazo[4,5-b]pyridine (IV) was also achieved. 相似文献
175.
Yoshihisa Kurasawa Yumiko Kamigaki Ho Sik Kim Chisako Watanabe Megumi Kanoh Mari Okiyama Atsushi Takada Yoshihisa Okamoto 《Journal of heterocyclic chemistry》1989,26(3):861-863
The reaction of the 3-substituted 4-aminopyrazolo[5, 1-c][1, 2, 4]triazines 1a-d with thiosemicarbazide hydrochloride in acetic acid gave new pyrazolo[5′,1′:3, 4][1, 2, 4]triazino[6, 5-f][1, 3, 4]thiadiazepines 3, 4 and 6 , which were converted into the 5-oxo derivatives 5 and 7 by hydrolysis in hydrochloric acid/acetic acid. 相似文献
176.
A facile synthesis of novel 1,2-diazepino[3,4-b]quinoxalines by a 1,3-dipolar cycloaddition reaction
Ho Sik Kim Yoshihisa Kurasawa Chiemi Yoshii Minako Masuyama Atsushi Takada Yoshihisa Okamoto 《Journal of heterocyclic chemistry》1990,27(3):819-822
The 1,3-dipolar cycloaddition reaction of the quinoxaline 4-oxides 4a,b with 2-chloroacrylonitrile gave the 2,3-dihydro-1H-1,2-diazepino[3,4-b]quinoxalines 5a,b , respectively, which were converted into the 2,3,4,6-tetrahydro-1H-1,2-diazepino[3,4-b]quinoxalines 7a,b and 8a,b , respectively. 相似文献
177.
Grosch B Orlebar CN Herdtweck E Kaneda M Wada T Inoue Y Bach T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(9):2179-2189
1,2,3,4-Tetrahydro-2-oxoquinoline-5-aldehyde (2) was prepared from m-aminobenzoic acid and 3-ethoxyacryloyl chloride (4) in 19 % overall yield. Compound 2 underwent a photochemically induced [4+2]-cycloaddition reaction with various dienophiles upon irradiation in toluene solution. The exo product 10 a was obtained with acrylonitrile (9 a) as the dienophile, whereas methyl acrylate (9 b) and dimethyl fumarate (9 c) furnished the endo products 11 b and 11 c (69-77 % yield). The reactions proceeded at -60 degrees C in the presence of the chiral complexing agent 1 (1.2 equiv) with excellent enantioselectivity (91-94 % ee). The enantiomeric excess increases in the course of the photocycloaddition as a result of the lower product association to 1. The intermediate (E)-dienol 8 was spectroscopically detected at -196 degrees C in an EPA (diethyl ether/isopentane/ethanol) glass matrix. The association of the substrate 2 to the complexing agent 1 was studied by circular dichroism (CD) titration. The measured association constant (K(A)) was 589 M(-1) at room temperature (25 degrees C) and normal pressure (0.1 MPa). An increase in pressure led to an increased association. At 400 MPa the measured value of K(A) was 703 M(-1). Despite the stronger association the enantioselectivity of the reaction decreased with increasing pressure. At 25 degrees C the enantiomeric excess for the enantioselective reaction 2 + 9 a-->10 a decreased from 68 % ee at 0.1 MPa to 58 % ee at 350 MPa. This surprising behavior is explained by different activation volumes for the diastereomeric transition states leading to 10 a and ent-10 a. 相似文献
178.
Ho Sik Kim Eun Kyoung Kim Sung Sik Kim Yong Tae Park Young Seuk Hong Yoshihisa Kurasawa 《Journal of heterocyclic chemistry》1997,34(1):39-42
The pyridazino[3,4-b]quinoxaline 12 was synthesized by the cyclization of the α-arylhydrazonoacyl-hydrazide 11. The reaction of compound 12 with phosphoryl chloride gave pyridazino[3,4-b]quinoxaline 13, whose reactions with sodium azide or cyclic secondary amines provided pyridazino[3,4-b]quinoxalines 14,17 and 18, respectively. The acylhydrazide 15 was also cyclized to pyridazino[3,4-b]quinoxaline 16. 相似文献
179.
Yoshihisa Kurasawa Tomoyoshi Hosaka Atsushi Takada Ho Sik Kim Yoshihisa Okamoto 《Journal of heterocyclic chemistry》1994,31(6):1661-1665
The 3-(arylhydrazono)methyl-2-oxo-1,2-dihydroquinoxalines 1a-e and 2a-i showed tautomeric equilibria between the hydrazone imine A and diazenyl enamine B forms in dimethyl sulfoxide media. The sub-stituent effects on the tautomer ratios of A to B in compounds 1a-e and 2a-i were studied by the nmr spec-troscopy. The electron-donating or electron-withdrawing p-substituents R1 in compounds 2a-i represented a tendency to increase the ratios of the tautomer A or the tautomer B , respectively, exhibiting the linear correlation of the Hammett constants σp (-0.17 to +0.78) with the tautomer ratios of A to B or the tautomeric equilibrium constants KT. However, the presence of the ester group R2 in compounds 1a-e induced the exclusive existence of the tautomer A regardless of the nature of the p-substituents R1. In the tautomeric thermodynamic study, the elevating temperature increased the ratios of the hydrazone imine tautomer A in compounds 2a-i . The tautomeric thermodynamic parameters ΔG°, ΔH° and ΔS° were derived from the van't Hoff plots for compounds 2a , b , h , i , wherein the entropy term dominated the free-energy difference between the A and B tautomers. 相似文献
180.
The UV.-isomerisation of 11-oxo-14β,17α-pregnane 9 to the 11,19-cyclo-derivative 11 is described. In addition the Pb(OAc)4-fragmentation of photoproduct 11 was investigated. 11 yielded besides the expected 11-oxo-19-hydroxy-pregnane 18 the novel 9,11-seco-11,19-cyclosteroid 19 . The structure of 19 was established by chemical transformations and subsequently confirmed by X-ray analysis [2]. 相似文献