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41.
Takushi Kurihara Yasuhiko Sakamoto Toshio Kobayashi Masanobu Mori 《Journal of heterocyclic chemistry》1978,15(5):737-743
Extensive studies of the Knoevenagel condensation of aromatic aldehydes and active methyl-lene compounds have been reported (2). In 1894, Knoevenagel reported (3) the reaction of benz-aldehyde with ethyl benzoylpyruvate in the presence of piperidine to give ehtyl benzyl-(bis-benzoyl)pyruvate, m.p. 162°, but no yield of the product was reported. This paper deals with the interesting results of the reactions of ethyl acetylpyruvate ( 2 ) ( 4 ) and ethyl benzoylpyruvate ( 3 ) (5) with some aromatic aldehydes ( 1a-f ). 相似文献
42.
Harusawa S Araki L Terashima H Kawamura M Takashima S Sakamoto Y Hashimoto T Yamamoto Y Yamatodani A Kurihara T 《Chemical & pharmaceutical bulletin》2003,51(7):832-837
(+)-4(5)-[(2R,5R)-5-aminomethyltetrahydrofuran-2-yl]imidazole [(+)-1, imifuramine] and its 2R,5S-stereoisomer (+)-2 were expected as base compounds to develop selective human histamine H4-receptor ligands. The improved synthesis of (+)-1 was done via cyclization of a diazafulvene intermediate generated by Bu3P/N,N,N',N'-tetramethylazodicarboxamide (TMAD) treatment of a diol 17ab bearing an unsubstituted imidazole moiety in good yields. This methodology also afforded an alternative synthetic route to trans- and cis-ethyl 4(5)-(5-hydroxymethyltetrahydrofuran-2-yl)imidazole carboxylates (5 and 6), reported previously. Also, 4(5)-[(2R,5S)-5-aminomethyltetrahydrofuran-2-yl]imidazole (+)-2 was synthesized from ethyl 4(5)-(2-deoxy-beta-D-ribofuranosyl)imidazole-1-carboxylate (35) via the four steps involving deoxygenation. 相似文献
43.
Zhao ZY McLeod A Harusawa S Araki L Yamaguchi M Kurihara T Lilley DM 《Journal of the American Chemical Society》2005,127(14):5026-5027
We constructed a modified form of the VS ribozyme containing an imidazole ring in place of adenine at position 756. The novel ribozyme is active in both cleavage and ligation reactions. The reaction is efficient, although relatively slow. The results are consistent with a role for nucleobase catalysis in the catalytic mechanism of this ribozyme. 相似文献
44.
Yamada T Nagata T Sugi KD Yorozu K Ikeno T Ohtsuka Y Miyazaki D Mukaiyama T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(18):4485-4509
The highly enantioselective borohydride reduction of aromatic ketones or imines to the corresponding alcohols was developed in the presence of a catalytic amount of an optically active cobalt(II) complex catalyst. This enantioselective reduction is carried out using a precisely premodified borohydride with alcohols such as tetrahydrofurfuryl alcohol, ethanol and methanol. High optical yields are obtained by choosing the appropriate alcohol as modifiers and a suitable beta-ketoiminato ligand of the catalyst. The enantioselective borohydride reduction has been successfully applied to the preparation of optically active 1,3-diols, the stereoselective reduction of diacylferrocenes, and dynamic and/or kinetic resolution of 1,3-dicarbonyl compounds. 相似文献
45.
Takushi Kurihara Hirokatsu Tanno Shigetaka Takemura Shinya Harusawa Ryuji Yoneda 《Journal of heterocyclic chemistry》1993,30(3):643-652
C-nor-4,6-Secocamptothecin 2 , 4-ethyl-4-hydroxy-6-(2-quinolinyl)-1H-pyrano[3,4-c]pyridine-3,8(4H,7H)-dione, lacking the C-ring of camptothecin 1 , and its related compounds 3 and 4 were prepared from ethyl quinoline-2-carboxylate 7 . By an analogous reaction sequences, synthesis of 6-(2-pyridinyl)-1H-pyrano[3,4-c]-pyridine-3,8(4H7H)-dione derivatives 5 and 6 , which contain the B, D, and E ring of 1 , were achieved. 相似文献
46.
Aqueous phosphoric acid as a mild reagent for deprotection of tert-butyl carbamates, esters, and ethers 总被引:1,自引:0,他引:1
Li B Berliner M Buzon R Chiu CK Colgan ST Kaneko T Keene N Kissel W Le T Leeman KR Marquez B Morris R Newell L Wunderwald S Witt M Weaver J Zhang Z Zhang Z 《The Journal of organic chemistry》2006,71(24):9045-9050
Aqueous phosphoric acid (85 wt %) is an effective, environmentally benign reagent for the deprotection of tert-butyl carbamates, tert-butyl esters, and tert-butyl ethers. The reaction conditions are mild and offer good selectivity in the presence of other acid-sensitive groups, including CBZ carbamates, azetidine, benzyl and methyl esters, TBDMS, and methyl phenyl ethers. The mildness of the reaction is further demonstrated in the synthesis of clarithromycin derivative, in which a tert-butyl ester is removed in the presence of cyclic carbamate, lactone, ketal, acetate ester, and epimerizable methyl ketone functionalities. The reaction preserves the stereochemical integrity of the substrates. The reactions are high yielding, and the workup is convenient. 相似文献
47.
We investigated the effects of refractive correction and refractive defocus on the assessment of sensory ocular dominance.
In 25 healthy subjects (4 males and 21 females) aged between 20 and 31 years, a quantitative measurement of sensory ocular
dominance was performed with refractive correction and the addition of a positive lens on the dominant eye. Sensory ocular
dominance was measured with a chart using binocular rivalry targets. The reversal point changed after the addition of a +1.00
D lens on the dominant eye in all subjects. However, sighting ocular dominance and stereopsis did not change after the addition
of a positive lens on the dominant eye (P > 0:05, Wilcoxon test). These results suggest that refractive correction affects sensory ocular dominance, indicating the
possible development of a new type of occlusion for amblyopia in the future. 相似文献
48.
Takeshi Mori Takushi Watanabe Keiji Minagawa Masami Tanaka 《Journal of polymer science. Part A, Polymer chemistry》2005,43(8):1569-1578
Rod–coil amphiphilic diblock copolymers, consisting of oligo(p‐phenylenevinylene) (OPV) as a rod and hydrophobic block and poly(ethylene oxide) (PEO) as a coil and hydrophilic block, were synthesized by a convergent method. The aggregation behavior of the block copolymers in a selective solvent (tetrahydrofuran/H2O) was probed with the absorption and emission of the OPV block. With increasing H2O concentration, the absorption maximum was blueshifted, the emission from the molecularly dissolved OPV decreased, and that from the aggregated OPV increased. This indicated that the OPV blocks formed H‐type aggregates in which the OPV blocks aligned in a parallel orientation with one another. The transmission electron microscopy observation revealed that the block copolymers with PEO weight fractions of 41 and 62 wt % formed cylindrical aggregates with a diameter of 6–8 nm and a length of several hundreds nanometers, whereas the block copolymer with 79 wt % PEO formed distorted spherical aggregates with an average diameter of 13 nm. Furthermore, the solubilization of an OPV homooligomer with the block copolymer was studied. When the total polymer concentration was less than 0.1 wt %, the block copolymer solubilized OPV with a 50 mol % concentration. The structure of the aggregates was a cylinder with a relatively large diameter distribution. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1569–1578, 2005 相似文献
49.
50.
Tamao Ishida Yuta Onuma Kota Kinjo Akiyuki Hamasaki Hironori Ohashi Tetsuo Honma Tomoki Akita Takushi Yokoyama Makoto Tokunaga Masatake Haruta 《Tetrahedron》2014
Palladium nanoparticles (Pd NPs) encapsulated by conjugated microporous polymers (CMPs) were prepared by the Pd-catalyzed polymerization followed by a thermal treatment with N2 or H2. The Pd catalysts were embedded in the porous network during polymerization and used as a precursor for the generation of Pd NPs in CMP. Although no Pd NPs were formed in the as-synthesized Pd/CMPs, Pd NPs with 1.6–3.5 nm size were formed after the thermal treatment. The obtained Pd/CMP-N2 and -H2 catalysts were highly selective in the hydrogenation of 4-nitrostyrene to 4-ethylnitrobenzene, whereas Pd NPs supported on carbon (Ketjen black) gave a fully reduced product, 4-ethylaniline. Substituents in CMP framework could change the catalytic activity of Pd NPs; hydroxy-substituted CMP encapsulated Pd NPs showed higher catalytic activity than Pd/CMP-H2 for benzyl alcohol oxidation. 相似文献