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101.
Palladium-catalyzed methoxycarbonylation of (−)-(2R,3S)-1-tert-butyldimethylsiloxy-3-methyl-2-methoxypenta-4-yne 9 derived from (2R,3S)-epoxy butanoate 5 gave the acetylenic ester 10, which was treated with MeOH in the presence of Bu3P to afford selectively (Z)-β-methoxy acrylate congener 11 in 86% yield. Treatment of (Z)-11 with 99.8% enrichment of CDCl3 followed by consecutive desilylation and oxidation afforded the left-half aldehyde (+)-2. The overall yield (10 steps from 5; 23%) of (+)-2 via the present route was improved in comparison to that (10 steps from 5; 10%) of the previously reported route. By applying the modified Julia's coupling method, selectivity (E/Z=14:1) of the (E)-form (cystothiazole A 1) against the (Z)-form was improved in comparison to the Wittig method (E/Z=4:1 to 6.9:1). 相似文献
102.
Iwata N Tani K Watada A Ikeura-Sekiguchi H Araki T Hitchcock AP 《Micron (Oxford, England : 1993)》2006,37(4):290-295
Toners are micron scale polymer particles constructed of several kinds of resin, pigment, wax, etc. Transmission electron microscopy (TEM) is used for observation of the dispersion of the component materials in toners, but TEM images cannot identify simultaneously all components. Scanning transmission X-ray microscopy (STXM) not only provides simultaneous observation of spatial distributions of wax, resin and carbon black in toners, but it also provides detailed, quantitative, chemical information about the wax and resin environments through chemical component maps derived from multiple energy image sequences. The capabilities of STXM for toner analysis are illustrated by results of a study of a toner for black/white copy/print applications. 相似文献
103.
104.
SK Podiyanachari R Fröhlich CG Daniliuc JL Petersen G Kehr G Erker N Suzuki S Yuasa K Hagimori S Inoue T Asada T Takemoto Y Masuyama 《Dalton transactions (Cambridge, England : 2003)》2012,41(35):10811-10816
The reaction of η(2)-iminozirconocene chloride complexes with trimethylsilylethynyl lithium leads to rapid C-C coupling at room temperature to yield the corresponding five-membered aza-zirconacycloallenoids. Such compounds were also obtained by trapping of in situ generated zirconocene with alkynyl imines. 相似文献
105.
Usuki T Yamada H Hayashi T Yanuma H Koseki Y Suzuki N Masuyama Y Lin YY 《Chemical communications (Cambridge, England)》2012,48(26):3233-3235
Desmosine, a crosslinking amino acid of elastin, is an attractive biomarker for diagnosis of chronic obstructive pulmonary disease (COPD). In this study, the first total synthesis of (+)-desmosine was achieved in 11% overall yield in 13 steps utilizing stepwise and regioselective Sonogashira cross-coupling reactions. 相似文献
106.
Yahia Didane Rocio Ponce Ortiz Jian Zhang Keijyu Aosawa Toshinori Tanisawa Hecham Aboubakr Frédéric Fages Jörg Ackermann Noriyuki Yoshimoto Hugues Brisset Christine Videlot-Ackermann 《Tetrahedron》2012,68(24):4664-4671
Solution and solid-state properties of two new perfluoroalkyl end-substituted analogues of distyryl-bithiophene (CF3-DS2T and diCF3-DS2T) are presented. Vacuum deposited thin films were investigated by atomic force microscopy, X-ray diffraction, and implemented as active layers into organic thin film transistors. While physicochemical measurements in solution suggest a preferential hole injection and transport inside CF3-DS2T and diCF3-DS2T films, electrical measurements performed under high vacuum show that CF3-DS2T behaves as n-type semiconductor while no charge transport was measured in diCF3-DS2T. The results highlighted the importance of substituents on conjugated backbone and on the resulting fine ordering in solid state to control the charge transport. 相似文献
107.
Noriyuki Otsubo 《Mathematische Zeitschrift》2012,270(1-2):423-444
We study the Abel–Jacobi image of the Ceresa cycle ${W_k-W_k^-}$ , where W k is the image of the kth symmetric product of a curve X on its Jacobian variety. For the Fermat curve of degree N, we express it in terms of special values of generalized hypergeometric functions and give a criterion for the non-vanishing of ${W_k-W_k^-}$ modulo algebraic equivalence, which is verified numerically for some N and k. 相似文献
108.
Noriyuki Suzuki Kosuke Nishimura Nozomu Ohara Masayoshi Nishiura Yoshiro Masuyama 《Journal of organometallic chemistry》2012,696(26):4321-4326
The stereoisomerization of 2,5-disubstituted 1-zirconacyclopent-3-yne compounds, stable five-membered cycloalkynes, has been studied with regard to the mechanism. The bimetallic complex of 1,4-bis(trimethylsilyl)butatriene was synthesized and structurally characterized, although it seems unimportant for the stereoisomerization reactions. The isomerization of trans-1,1-bis(η5-cyclopentadienyl)-2,5-bis(trimethylsilyl)-1-zirconacyclopent-3-yne 2a into the cis-form in benzene-d6 solution were observed using 1H NMR spectroscopy at 50 °C in various concentrations. The reaction was first order with respect to trans-2a. This ruled out the possibility that a bimetallic complex was responsible for the isomerization. A kinetic isotope effect was observed (kH/kD = 1.8), suggesting that C–H activation is involved in the rate-determining step. A mechanism via hydrogen elimination from the complex of η4-π,π-coordination mode is proposed. 相似文献
109.
Solvent effects on a potential energy surface crossing are investigated by optimizing a conical intersection (CI) in solution. To this end, the analytic energy gradient has been derived and implemented for the collinear spin-flip density functional theory (SFDFT) combined with the effective fragment potential (EFP) solvent model. The new method is applied to the azomethane-water cluster and the chromophore of green fluorescent protein in aqueous solution. These applications illustrate not only dramatic changes in the CI geometries but also strong stabilization of the CI in a polar solvent. Furthermore, the CI geometries obtained by the hybrid SFDFT/EFP scheme reproduce those by the full SFDFT, indicating that the SFDFT/EFP method is an efficient and promising approach for understanding nonadiabatic processes in solution. 相似文献
110.
H Nagase S Imaide T Yamada S Hirayama T Nemoto N Yamaotsu S Hirono H Fujii 《Chemical & pharmaceutical bulletin》2012,60(8):945-948
On the basis of the three-dimensional pharmacophore model of opioid κ agonists, we simplified the structure of nalfurafine (selective κ agonist) to find the essential structural moieties for binding the opioid receptors, especially κ receptor type. As a result, we found that the trans-fused decahydroisoquinoline derivatives without a phenol ring bound the opioid receptor in micromolar order and that both the amide side chain and the nitrogen substituted by the cyclopropylmethyl group were indispensable moieties for eliciting the κ selectivity. The simple decahydroisoquinoline without amide side chain also bound the opioid receptor without receptor type selectivity, suggesting that the message-address concept would be applicable to even these simple derivatives. These findings that the simple decahydroisoquinoline derivatives showed the affinities for the opioid receptors, especially some of the compounds showed κ selectivity, are the first example in the opioid field. 相似文献