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131.
132.
Segawa Y Suzuki Y Yamashita M Nozaki K 《Journal of the American Chemical Society》2008,130(47):16069-16079
A series of lithium salts of boryl anion, boryllithiums, were synthesized and characterized by NMR spectroscopy and crystallographic analysis. In addition to the parent boryllithium compound 35a, structural modification of boryllithium, using saturated C-C and benzannulated C=C backbones in the five-membered ring and mesityl groups on the nitrogen atoms, also allowed generation of the corresponding boryllithium. The solid state structures of boryllithium showed that the boron-lithium bond is polarized where the boron atom is anionic in all (35a x DME)(2), 35a x (THF)(2), 35b x (THF)(2), and 35c x (THF)(2) when compared to the structures of hydroborane 38a-c and optimized free boryl anion opt-46a-c. Dissolution of the isolated single crystals of (35a x DME)(2) and 35a x (THF)(2) in THF-d(8) showed that the boron-lithium bond remained in solution and free DME or THF molecules were observed. Temperature-dependent (11)B NMR chemical shift changes of 35a were observed in THF-d(8) or methylcyclohexane-d(14), suggesting a change of chemical shift anisotropy around the boron center. The HOMO of opt-35a x (THF)(2) had a lone pair character on the boron atom, as observed for phenyllithium, whereas the HOMO of hydroborane 38a corresponds to the pi-orbital of the boron-containing five-membered heterocycle. The polarity of the B-Li bond, estimated by AIM analysis, was similar to that of alkyllithium. Boryllithiums 35a and 35b behave as a base or a boron nucleophile in reaction with organic electrophiles via deprotonation, S(N)2-type substitution, halogen-metal exchange or electron-transfer, 1,2-addition to a carbonyl group, and S(N)Ar reaction. In the case of the reaction with CO(2), intramolecular cyclization followed by CO elimination from borylcarboxylate anion and subsequent protonation gave hydroxyboranes 64a and 64b. The characters of the carbonyl groups in the borylcarbonyl compounds 60a, 60b, 61, 62, and 63a, which were obtained from the reaction of boryllithiums 35a and 35b, were investigated by X-ray crystallography, IR, and (13)C NMR spectroscopy to show that the boryl substituent weakened the C=O bond when compared to carbon substituted analogues. 相似文献
133.
Hiroyuki Ishibashi Motofumi Okada Kyoko Iida Masazumi Ikeda 《Journal of heterocyclic chemistry》1985,22(6):1527-1529
A variety of ethyl isothiochroman-1-carboxylates and related compounds were synthesized by treatment of 2-chloro-2-[(2-arenyl)ethylthio]acetates with stannic chloride in methylene chloride. The same procedure was applied to the synthesis of ethyl 4-chloro-4-methyltetrahydrothiopyran-2-carboxylate. Some isothiochroman-1-carboxylic acids were prepared and evaluated for antiinflammatory activity. Among the compounds tested, 7-phenoxyisothiochroman-1-carboxylic acid showed weak activity. 相似文献
134.
We present three types of summation formulas for the root system G2úG_{2}^{\vee}, which are generalized from Bailey’s summation formula for a very-well-poised balanced 6
ψ
6 basic hypergeometric series. 相似文献
135.
The CO2 TEA laser irradiation of CBr2F2 in the presence of Cl2 yielded 13C-enriched CBrClF2 and 13C-enriched CCl2F2 under selected experimental conditions. As the photolysis proceeded, the 13C concentration of CBrClF2 decreased gradually and that of CCl2F2 increased up to 90% or higher. These results can be explained by the mechanism involving the secondary 13C-selective IRMPD of the primary product CBrClF2. On the other hand, the carbon-containing product for a CCl2F2/Br2 system was only CBrClF2; the further IRMPD of which probably regenerated CBrClF2 in the presence of Br2. The decomposition probabilities of 12C- and 13C-containing molecules in both systems were measured as functions of laser line, laser fluence, and reactant pressures. 相似文献
136.
Recently, a relatively simple scheme for the construction of isotropic intermolecular potentials has been proposed and tested for the like species interactions involving He, Ne, Ar, Kr and H2. The model potential has an adjustable parameter which controls the balance between its exchange and Coulomb energy components. The representation of the Coulomb energy contains a damped multipolar dispersion energy series (which is truncated through O(R?10) and provides additional flexibility through adjustment of the dispersion energy coefficients, particularly C8 and C10, within conservative error estimates. In this paper the scheme is tested further by application to interactions involving unlike noble gas atoms where the parameters in the potential model are determined by fitting mixed second virial coefficient data as a function of temperature. Generally the approach leads to potential of accuracy comparable to the best available literature potentials which are usually determined using a large base of experimental and theoretical input data. Our results also strongly indicate the need of high quality virial data. 相似文献
137.
Efficient routes for the syntheses of optically pure and hitherto unknown l-chiro- and d-allo-inositol derivatives, azido- and aminocyclitols of l-chiro-configuration, diazido- and diaminocyclitols of d-allo-configuration from economically viable myo-inositol are described. These routes provide access to synthetically flexible 1,2:4,5-di-O-isopropylidene-chiro-inositol and 1,6:3,4-di-O-isopropylidene-allo-inositol, which are otherwise difficult to synthesize directly from their parent inositols. A one pot methodology that allows rapid access to both chiro- and allo-inositol derivatives has also been developed. Investigations on the glycosidase inhibitory properties of these novel azido- and amino-inositols unraveled the potentials of these classes of compounds as novel class of glycosidase inhibitors. Both d and l forms of these cyclitols could be synthesized from myo-inositol in gram scales and hence by exploiting the difference in reactivities of cis- and trans-ketals, a variety of protected derivatives, which are useful for the synthesis of unnatural phosphoinositols and natural products, can be synthesized. 相似文献
138.
Tsujioka T Sesumi Y Takagi R Masui K Yokojima S Uchida K Nakamura S 《Journal of the American Chemical Society》2008,130(32):10740-10747
We report here a novel phenomenon: selective metal deposition on photoswitchable diarylethene (DAE) surfaces. Magnesium vapor was deposited by vacuum evaporation on the colored DAE but not on the uncolored surface. The selective deposition originates in the change of the glass transition temperature of the amorphous DAE film resulting from photoisomerization and therefore from changes of surface molecular motion. We clarified that Mg atoms on the uncolored surface actively migrated on the surface and were desorbed from the surface. The possibility of depositing other metals is also discussed. Light-controllable metal-integrated deposition was demonstrated as a new function of the photoswitchable molecular surfaces. This study reveals new features of the photoswitchable molecular surfaces, and their potential suggests bright prospects for future applications in organic electronics. 相似文献
139.
The structure and hydrogen bonding of water incorporated in a thin film of amphoteric terpolymers composed of various ratios of MA, DMAPMA, and BMA were analyzed using the band shapes of the O--H stretching in the IR spectra. At an early stage of sorption of water, the IR spectrum for the water incorporated in the film with comparative contents of MA and DMAPMA residues was similar to that for free water. This is consistent with the tendency for zwitterionic polymers, but is in contrast with the drastic change in the IR spectrum of water incorporated in non-ionic polymer films such as polyBMA. These results suggest a correlation between the mildness of the charge-balanced polymers to the structure of incorporated water and their blood compatibilities. 相似文献
140.
Crystalline Isotactic Polar Polypropylene from the Palladium‐Catalyzed Copolymerization of Propylene and Polar Monomers 下载免费PDF全文
Yusuke Ota Dr. Shingo Ito Dr. Minoru Kobayashi Dr. Shinichi Kitade Kazuya Sakata Takao Tayano Prof. Kyoko Nozaki 《Angewandte Chemie (International ed. in English)》2016,55(26):7505-7509
Moderately isospecific homopolymerization of propylene and the copolymerization of propylene and polar monomers have been achieved with palladium complexes bearing a phosphine‐sulfonate ligand. Optimization of substituents on the phosphorus atom of the ligand revealed that the presence of bulky alkyl groups (e.g. menthyl) is crucial for the generation of high‐molecular‐weight polypropylenes (Mw≈104), and the substituent at the ortho‐position relative to the sulfonate group influences the molecular weight and isotactic regularity of the obtained polypropylenes. Statistical analysis suggested that the introduction of substituents at the ortho‐position relative to the sulfonate group favors enantiomorphic site control over chain end control in the chain propagation step. The triad isotacticity could be increased to mm=0.55–0.59, with formation of crystalline polar polypropylenes, as supported by the presence of melting points and sharp peaks in the corresponding X‐ray diffraction patterns. 相似文献