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21.
Kleeberg C Cheung MS Lin Z Marder TB 《Journal of the American Chemical Society》2011,133(47):19060-19063
Reaction of [(IPr)Cu-OtBu] (1) with pinB-SiMe(2)Ph (2) leads to the Cu-silyl complex [(IPr)Cu-SiMe(2)Ph] (3). Insertion of CO(2) into the Cu-Si bond of 3 is followed by transformation of the resulting silanecarboxy complex [(IPr)Cu-O(2)CSiMe(2)Ph] (4) to the silanolate complex [(IPr)Cu-OSiMe(2)Ph] (5) via extrusion of CO. As 5 reacts readily with 2 to regenerate 3, a catalytic CO(2) reduction to CO is feasible. The individual steps were studied by in situ(13)C NMR spectroscopy of a series of stoichiometric reactions. Complexes 3, 4, and 5 were isolated and fully characterized, including single-crystal X-ray diffraction studies. Interestingly, the catalytic reduction of CO(2) using silylborane 2 as a stoichiometric reducing agent leads not only to CO and pinB-O-SiMe(2)Ph but also to PhMe(2)Si-CO(2)-SiMe(2)Ph as an additional reduction product. 相似文献
22.
Hubert G. Theuns Richard H. A. M. Janssen Hubertus W. A. Biessels Cornelis A. Salemink 《Magnetic resonance in chemistry : MRC》1984,22(12):793-794
13C NMR chemical shifts are assigned for some quaternary morphinan derivatives, including the ‘minor isomer’ of the thebaine N-oxides. In quaternary morphinan alkaloids having an 8.14-double bond, electric field effects cause unusual 13C NMR shifts. 相似文献
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[PdCl(TeMe2)3](BArF) – The First Structurally Characterized Palladium(II) Complex with TeMe2 Ligands
[PdCl(TeMe2)3]BArF ( 4 ) forms as the major tellurium containing product from the reaction of [(4‐Mebti)PdCl] with TeMe2 and Na(BArF) and is isolated by crystallization from the reaction mixture. At ?20 °C, the compound forms orange columns from toluene/pentane, space group , with Z = 2. In the solid, the cationic [PdCl(TeMe2)3]+ complex ions show a non‐planar PdClTe3 coordination unit and are associated to dimers via weak Pd···Te interactions. 相似文献
26.
Jonker N Kool J Krabbe JG Retra K Lingeman H Irth H 《Journal of chromatography. A》2008,1205(1-2):71-77
A novel methodology is shown enabling the screening of mixtures of compounds for their affinity to a receptor protein. The system presented, dynamic protein-affinity chromatography solid-phase extraction (DPAC-SPE), overcomes the limitations of the existing methods by performing an incubation of the His-tagged protein with a mixture of possible ligands, which are still in their native conditions. This is followed by a fully automated affinity trapping step, coupled on-line to an LC-MS system in order to detect and identify the bound ligands. The system has been optimized using a commercially available on-line SPE system, using the estrogen receptor alpha (ERalpha) as model protein. A representative range of ligands with sub-nanomolar to millimolar affinities has been identified successfully from a mixture. The weakest binder that can be identified is norethindrone (approximately K(d)=0.1-1mM). The same setup also provides the possibilities to measure EC50 curves of both weak and strong binders. 相似文献
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We report synthetically accessible receptors with protonated amines attached to a conformationally constrained backbone including amide units, and demonstrate that these receptors have high affinities (log K > 5) for phosphate anions in aqueous media at pH 7 in the presence of high concentrations of competitive chloride anions (ca. 100-fold excess). 相似文献
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The reaction of 1,3-bis(4,6-dimethylpyridyl-2-imino)isoindoline and palladium acetate in methanol selectively yields the expected acetato palladium N,N,N-chelate or a cyclometalated tetranuclear dimer depending on the stoichiometry of the reactants. 相似文献
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High-performance liquid chromatography-mass spectrometry-based acetylcholinesterase assay for the screening of inhibitors in natural extracts 总被引:1,自引:0,他引:1
de Jong CF Derks RJ Bruyneel B Niessen W Irth H 《Journal of chromatography. A》2006,1112(1-2):303-310
The present paper describes a High-performance liquid chromatography-mass spectrometry (LC-MS) methodology for the screening of acetylcholinesterase (AChE) inhibitors in natural extracts. AChE activity of sample components is monitored by a post-column biochemical assay that is based on the separate, sequential mixing of AChE and acetylcholine, respectively, with the HPLC eluate. AChE inhibitors are detected by measuring a decrease of product formation using electrospray MS. Ammonium bicarbonate was used as buffer in order to achieve optimum compatibility between biochemical assay and MS detection conditions. The assay is robust and stable for over 13 h and compares favourably with other AChE assays in terms of stability and sensitivity. IC(50) values of 9-aminoacridine, galanthamine, gallamine, (-)-huperzine A and thioflavin T were determined to be 0.12, 0.38, 6.4, 0.46 and 3.2 microM, respectively. The assay was used to effectively identify an AChE inhibitor present in a crude extract of Narcissus c.v. "Bridal Crown". 相似文献