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41.
A new reagent, lithium di(3-furyl)cuprate·2furyllithium, which is distinct from lithium di(3-furyl)cuprate, possesses an excellent nucleophilicity and gives 3-substituted furans in good yields by the reactions with less reactive oxiranes. 相似文献
42.
In order to elucidate the structure-activity relationships of the antifeeding diterpenes having a -clerodane skeleton, clerodin homolog was stereoselectively synthesized through 18 steps a key intermediate . Perhydrofuro[2,3-b]furan ring in the synthesized homolog was more unstable than that of the natural product, and gave a -MeOH adduct in a similar behavior to that of the model compounds and . 相似文献
43.
1-Phenyltridecamethylbicyclo[2.2.2]octasilane (1) is prepared by the reaction of the corresponding 1-chlorotridecamethylbicyclo[2.2.2]octasilane with phenyllithium in the presence of N,N,N',N'-tetramethylethylenediamine and the molecular structure of is determined by X-ray crystallography. Phenyloligosilane shows dual fluorescence even in non-polar hexane though the TICT-like mechanism is not applicable. 相似文献
44.
In this study, the Euler-Bernoulli beam model is used to analyze the resonant vibration of double-walled carbon nanotubes (DWCNTs) with inner and outer nanotubes of different lengths. The resonant properties of DWCNTs with different inner and outer nanotube lengths are investigated in detail using this theoretical approach. The resonant vibration is significantly affected by the vibrational modes of the DWCNTs, and by the lengths of the inner and outer nanotubes. For an inner or outer nanotube of constant length, the vibrational frequencies of the DWCNTs increase initially and then decrease as the length of another nanotube increases. A design for nanoelectromechanical devices that operate at various frequencies can be realized by controlling the length of the inner and outer nanotubes of DWCNTs. This investigation may be helpful in applications of carbon nanotubes such as high frequency oscillators, dynamic mechanical analysis and mechanical sensors. 相似文献
45.
46.
Natsuki Mori 《Tetrahedron》2009,65(17):3509-2495
The reaction of 1-chlorovinyl p-tolyl sulfoxides, derived from ketones and chloromethyl p-tolyl sulfoxide, with i-PrMgCl at −78 °C gave magnesium alkylidene carbenoids. Treatment of the magnesium carbenoids with 2-lithiothiophenes and 2-lithiofurans resulted in the formation of 2-alkenylated thiophenes and furans, respectively, in good to high yields. The intermediates of these reactions were found to be alkenylmagnesium, which could be trapped with several electrophiles to afford thiophenes and furans bearing a fully substituted alkene at the 2-position. Treatment of the magnesium alkylidene carbenoids with 2-lithio-5-methoxyfuran afforded allenes conjugated with α,β-unsaturated methyl ester in moderate yields. These procedures offer a new and versatile one-pot synthesis of 2-alkenylthiophenes, 2-alkenylfurans, and allenes conjugated with α,β-unsaturated methyl ester from 1-chlorovinyl p-tolyl sulfoxides. 相似文献
47.
48.
Based on molecular mechanics coupled with the atomistic-based continuum theory, a structural mechanics approach is presented to examine the nonlinear elastic properties of carbon nanotubes (CNTs) subjected to large axial deformations. According to molecular mechanics, the interaction force between atoms is modeled using the Morse potential. The nanoscale continuum theory is established to directly incorporate the Morse potential function into the constitutive model of CNTs. In this paper, we simulate and examine the influence of CNT structures on the stress–strain response. The linear elastic property of CNTs is independent of the helicity of the hexagonal carbon lattice along the tubes, while their nonlinear elastic behavior shows a larger chirality dependence. The present theoretical approach supplies a set of very simple formulas and is able to serve as a good approximation of the mechanical properties of CNTs. PACS 62.20.-x; 62.20.Dc; 62.25.+g 相似文献
49.
Natsuki Takei Misaki Morioka Mari Yoshizato Takuya Tanaka Shin-ichi Sasaki Satoshi Ito Hitoshi Tamiaki Toru Oba 《Tetrahedron》2014
Chlorophyll derivatives that possessed a phenylsulfanyl group at the C31- or C32-position were synthesized and their optical properties were investigated. Methyl 31-phenylsulfanyl-mesopyropheophorbide-a was prepared by substitutions of the corresponding C31-hydroxy-chlorin, methyl bacteriopheophorbide-d, with thiophenol in the presence of zinc iodide or of the corresponding C31-bromo-chlorin with thiophenol. The regioisomeric C32-phenylsulfanyl-chlorin was obtained by addition of thiophenol to the C3-vinyl group of methyl pyropheophorbide-a in the presence of AIBN. Both the synthetic compounds gave similar electronic absorption and emission spectra in chloroform, but fluorescence quantum yield of the C31-sulfanyl-chlorin (0.18) was ca. 30% smaller than those of the C32-sulfanyl-chlorin (0.25) and the C3-ethyl-chlorin (0.24). These observations were consistent with their fluorescence lifetime data. It is suggested that the heavy atom effect of a sulfur atom at the C31-position can tune photophysical properties of the chlorophyll derivatives. 相似文献
50.
Mori Yoshikazu Katayama Yoshihiro Shikata Toshiyuki Kasuya Natsuki 《Research on Chemical Intermediates》2020,46(1):609-620
Research on Chemical Intermediates - The synthesis of 5-ethoxymethylfurfural (EMF) from glucose using metal chlorides or combined metal–surfactant catalysts as Lewis acids in a solution of... 相似文献