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1.
The N-bonded nitrile complexes -[Co(tetren)NCR]3+ (R=Me, Ph, p-MeOC6 H4) have been prepared by the reaction of -[Co(tetren)OH2]3+ with the corresponding nitrile. The kinetics of base hydrolysis have been studied by pH-stat methods. The reactions involve an SN1CB displacement of the nitrile to give the hydroxopentamine; nucleophilic attack at the nitrile carbon to give the corresponding carboxamido complex does not occur. NaN3 reacts with the nitrile complexes in slightly acidic solution (pH ca. 5.7) to give the tetrazolato complexes [Co(tetren)N4 R]2+ (R=Me, Ph) which have been characterised. The reaction of azide ion with -[Co(tetren)NCMe]3+ has been studied kinetically. The reaction is biphasic involving the initial rapid formation of the N1-bonded (5-methyltetrazolato) pentaminecobalt(III) complex with k=2×10–2dm3 mol–1s–1 at 25°C followed by the slow isomerisation to the N2-bonded complex with k=3.5×10–5s–1 at pH 5.7. 相似文献
2.
Allan C. Baxter James H. Cameron Alexander McAuley Fiona M. McLaren John M. Winfield 《Journal of fluorine chemistry》1977,10(4):289-298
Copper(II) fluorine reacts with the pentafluorides, TaF5, PF5, and AsF5, in acetonitrile to give solvated CuII, hexafluoroanion salts. These react with copper metal to give the corresponding CuI compounds. Similar reactions occur between AsF5 and silver(I) or thallium(I) fluorides, but silver(II) fluoride reacts with MeCN, and AgI hexafluoroarsenate is formed. PF5 oxidises Cu slowly in MeCN to give CuI hexafluorophosphate, but AsF5 has no oxidising ability towards metals in MeCN. Spectroscopic data for Cu(MF6)2·5MeCN and Cu(MF6)·4MeCN (M = Ta or P) are discussed. 相似文献
3.
A comparative evaluation has been made of both proton and (13)C nuclear magnetic resonance techniques in the quantitative characterization of commercial urea-formaldehyde resins. There is good agreement between data derived from (13)C NMR spectra and from (1)H high-field continuous wave, or low-field (Fourier transform) NMR spectra. Low-field continuous wave proton spectra exhibit inferior resolution and provide inaccurate quantitative data. Combination of (13)C and proton NMR with nitrogen analysis gives a quantitative characterization technique for these resins. 相似文献
4.
The characterisation of two cross-linked poly(acryloylmorpholines), Enzacry Gel K1 and Enzacryl Gel K2, as matrices for aqueous gel permeation chromatography is described. Near ideal plots of logarithm molecular weight versus distribution coefficient, Kd, are obtained for polyethylene glycols and linear, oligomeric α,ω-diols approximate molecular weight (
n) fractionation ranges being 0–4000 and 0–20,000 for Enzacryl Gel K1 and Enzacryl Gel K2, respectively. Anomalous retardation of the Schardinger dextrins, cyclomaltohexose and cyclomaltoheptose, is observed although linear maltosaccharides behave normally. The internal gel volumes, calculated from column elution data in water, are significantly larger than the volumes of solvent imbibed by the dry column packings on constituting the gel. Internal gel volumes and solvent imbibition volumes in water are compared with the corresponding values obtained in chloroform and tetrahydrofuran. The two parameters are discussed, in the case of Enzacryl Gel K2 in water and chloroform, in the light of plots of logarithm viscometric hydrodynamic volume versus Kd for polyethylene glycols. 相似文献
5.
Jose Castro‐Perez Nathan Hatcher Nana Kofi Karikari Sheng‐Ping Wang Vivienne Mendoza Henry Shion Alan Millar John Shockcor Mark Towers David McLaren Vinit Shah Stephen Previs Karen Akinsanya Michele Cleary Thomas P. Roddy Douglas G. Johns 《Rapid communications in mass spectrometry : RCM》2014,28(22):2471-2479
6.
This report discloses a novel concise synthesis of a series of 3-hydroxypyrazoles 5 via a tandem Ugi/debenzylation /hydrazine-mediated cyclization sequence. Herein, n-butyl isocyanide 4b was utilized as an alternative to classical convertible isocyanides enabling high yielding hydrazine-mediated cyclization. Taken together, a novel class of 3-hydroxypyrazoles 5a-5i was synthesized with potential to be of interest in future library enrichment strategies. 相似文献
7.
A systematic evaluation of continuous flow-counterbalanced capillary electrophoresis for microscale preparative applications is presented. The success of the technique was found to depend on the specific nature of the analyte and background electrolyte and was most heavily influenced by factors such as solution conductivity and rate of buffer depletion. The performance of the technique for the system studied was ultimately limited by contamination arising from changes in analyte mobilities during extended run times. Marked improvements in both purification rate and yield were observed using the zwitterionic buffer 2-(N-cyclohexylamino)ethanesulfonic acid when compared to similar runs carried out using a borate background electrolyte. A quantitative evaluation of the technique was performed for the analytes studied and the performance of the technique has been compared to fraction collection methods. The highest recovery achieved was 5.2% of the fastest migrating component present in the original sample with a resolution of 9 to the adjacent peak and required 100 min under optimized conditions. Recovery could be further increased to 9.0% in 120 min for the same analyte using pressure-ramped flow-counterbalanced capillary electrophoresis. 相似文献
8.
J. W. McLaren K. W. M. Siu J. W. Lam S. N. Willie P. S. Maxwell A. Palepu M. Koether S. S. Berman 《Fresenius' Journal of Analytical Chemistry》1990,337(6):721-728
Summary The versatility of ICP-MS in marine analytical chemistry is illustrated with applications to the multielement trace analysis of two recently released marine reference materials, the coastal seawater CASS-2 and the non-defatted lobster hepatopancreas tissue LUTS-1, and to the determination of tributyltin and dibutyltin in the harbour sediment reference material PACS-1 by HPLC-ICP-MS. Seawater analyses were performed after separation of the trace elements either by adsorption on immobilized 8-hydroxy-quinoline or by reductive coprecipitation with iron and palladium. Simultaneous determination of seven trace elements in LUTS-1, including mercury, by isotope dilution ICP-MS, was achieved after dissolution by microwave digestion with nitric acid and hydrogen peroxide. Butyltin species in PACS-1 were separated by cation exchange HPLC of an extract of the sediment; method detection limits for tributyltin and dibutyltin in sediment samples are estimated to be 5 ng Sn/g and 12 ng Sn/g, respectively.Summer assistant 1988Summer assistant 1989 相似文献
9.
Amelie Heuer-JungemannRoss G. McLaren Maximillian S. HadfieldAi-Lan Lee 《Tetrahedron》2011,67(9):1609-1616
Gold(I)-catalysed intermolecular iodoalkoxylation of allenes occurs in a regioselective and stereoselective manner to produce versatile iodo-tert-allyllic ether products. The products can be further elaborated through cross-couplings to yield highly substituted tert-allylic ethers. 相似文献
10.
Castro-Perez J Roddy TP Nibbering NM Shah V McLaren DG Previs S Attygalle AB Herath K Chen Z Wang SP Mitnaul L Hubbard BK Vreeken RJ Johns DG Hankemeier T 《Journal of the American Society for Mass Spectrometry》2011,22(9):1552-1567
A high content molecular fragmentation for the analysis of phosphatidylcholines (PC) was achieved utilizing a two-stage [trap (first generation fragmentation) and transfer (second generation fragmentation)] collision-induced dissociation (CID) in combination with travelling-wave ion mobility spectrometry (TWIMS). The novel aspects of this work reside in the fact that a TWIMS arrangement was used to obtain a high level structural information including location of fatty acyl substituents and double bonds for PCs in plasma, and the presence of alkali metal adduct ions such as [M?+?Li]+ was not required to obtain double bond positions. Elemental compositions for fragment ions were confirmed by accurate mass measurements. A very specific first generation fragment ion m/z 577 (M-phosphoryl choline) from the PC [16:0/18:1 (9Z)] was produced, which by further CID generated acylium ions containing either the fatty acyl 16:0 (C15H31CO+, m/z 239) or 18:1 (9Z) (C17H33CO+, m/z 265) substituent. Subsequent water loss from these acylium ions was key in producing hydrocarbon fragment ions mainly from the α-proximal position of the carbonyl group such as the hydrocarbon ion m/z 67 (+H2C-HC?=?CH-CH?=?CH2). Formation of these ions was of important significance for determining double bonds in the fatty acyl chains. In addition to this, and with the aid of 13C labeled lyso-phosphatidylcholine (LPC) 18:1 (9Z) in the ω-position (methyl) TAP fragmentation produced the ion at m/z 57. And was proven to be derived from the α-proximal (carboxylate) or distant ω-position (methyl) in the LPC. 相似文献