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1.
Hägele Gerhard Boenigk Winfried Engelhardt Michael 《Analytical and bioanalytical chemistry》1985,320(7):676-677
Analytical and Bioanalytical Chemistry - 相似文献
2.
The NMR titration methodology to determine acid dissociation constants in aqueous solutions is extended for pK(a) values between 0 and 2, where potentiometric titrations are no longer applicable. (1)H NMR spectra are acquired for single samples of constant acid concentration (e.g. 0.02M), controlled ionic strength (I=1M with HNO(3)/NaNO(3)) and varying pH. To avoid biased pH readings due to the acid error of the glass electrode, true, concentration-based pH values are deduced by combination of the charge balance equation with information from (1)H NMR chemical shifts of the investigated acid. The method has been tested on histidine (pK(1)=1.83+/-0.02) and yielded the dissociation constant of dichloroacetic acid (pK=1.06+/-0.01) for the first time with good accuracy and precision. Dichloroacetic acid is recommended as an NMR spectroscopical "indicator molecule" for in situ monitoring the pH in strong acidic solutions of other equilibrium systems. 相似文献
3.
(CO)6Fe2(PhPH)2 bildet mit PhPCl2 den phosphidoverbrückten tetranuklearen Komplex [PhPHFe2(CO)6PPh]2PPh. 31P{1H}-NMR-Spektren der Titelverbindung werden als [AB]2C-Systeme analysiert, Stereoisomere werden diskutiert. 31P-NMR Studies on PhPH(CO)6Fe2(PPh)3Fe2(CO)6PPhH ? a Tetranuclear Complex with an Unusual (PPh)3 Bridge (CO)6Fe2(PhPH)2 and PhPCl2 form [PhPHFe2(CO)6PPh]2PPh, a tetranuclear complex with phosphido bridges. 31P{1H}-NMR spectra are analysed as [AB]2C systems, stereoisomers are discussed. 相似文献
4.
P. Ackerbauer J. Werner W. H. Breunlich M. Cargnelli M. Jeitler P. Kammel J. Marton N. Nägele A. Scrinzi J. Zmeskal J. Bistirlich K. M. Crowe C. Petitjean R. H. Sherman P. Baumann H. Bossy H. Daniel F. J. Hartmann W. Schott T. von Egidy W. Neumann 《Hyperfine Interactions》1993,82(1-4):357-372
A main source of information about the muon-catalyzed fusion cycle in D-T mixtures are the cycling rates c, which are characteristic for the kinetic equilibrium of states attained rapidly in dense targets. The measurement, analysis and interpretation of these rates will be discussed, concentrating on the extensive set of rates observed at PSI over the last decade in gaseous, liquid and solid targets.Invited talk presented by Peter Kammel. 相似文献
5.
Paul Bendig Florian Hägele Walter Vetter 《Analytical and bioanalytical chemistry》2013,405(23):7485-7496
Food and contaminated indoor environments are the most relevant sources of human exposure to polyhalogenated chemicals. This study analyzed for the first time fat residues in kitchen hoods for contaminations with polyhalogenated compounds. A wide range of contaminants was detected in all kitchen hoods (n?=?15) and most of them could be quantified. Between 0.2 and 18 μg polyhalogenated chemicals/g fat were detected, with chlorinated paraffins being the most relevant contaminant group. Aside from the chlorinated paraffins, each kitchen hood fat sample showed a distinct fingerprint. A wide range of old and current-use brominated flame retardants were also detected in the samples. In addition to these contaminants originating from their use in indoor equipment, residues of organochlorine pesticides and semi-volatile halogenated natural products verified that cooking of food, accompanied with the release of contaminants from the heated food, was another relevant source of contamination. Re-analyses of two samples after 3 months only resulted in small variations in contaminant pattern and concentrations. Therefore, fat from kitchen hoods is proposed as an easily accessible matrix to assess contamination of these hazardous polyhalogenated chemicals. Figure
Picture of a kitchen hood and its filter. The fat collected from kitchen hood filters contained plenty of polyhalogenated chemicals 相似文献
6.
Karlsson Erik Neuhausen Jörg Eichler Robert Danilov Ivan I. Vögele Alexander Türler Andreas 《Journal of Radioanalytical and Nuclear Chemistry》2021,328(2):707-715
Journal of Radioanalytical and Nuclear Chemistry - The usage of silver as a filtering material for removal of iodine from the gas phase of a lead–bismuth eutectic based nuclear reactor was... 相似文献
7.
8.
The molecular structure of t-butyl-phenylphosphinic acid (?)-menthyl ester (1eS) has been determined by X-ray analysis and the results compared with the findings of a detailed NMR-study. 1eS crystallises in the monoclinic space group P2 1 with a = 9.304(2), b = 10.678(4), c = 12.681(4) Å, β = 124.91(1)°, Z = 2, Dx = 1.08 g cm?3. The structure was refined to R = 0.035 for 1842 independent reflections. The absolute configuration was confirmed as S(p). Both methyl functions of the menthyl-iso-propyl substituent take up positions close to the phenyl ring system. 相似文献
9.
The 1H and 19F NMR spectra of the CH2FCHF group in FCH2CHFCO2C2H5 were analysed on the basis of an ABCXY spin system. The non-equivalence of the methylene protons is discussed in terms of rotational isomerism. It is concluded that the dominant rotamer is probably considerably distorted from a perfectly staggered orientation. The variation of 3JHF with substituent electronegativity is reviewed. 相似文献
10.
Cichocki B Ekiel-Jezewska ML Nägele G Wajnryb E 《The Journal of chemical physics》2004,121(5):2305-2316
A system of many spherical particles, suspended in a quiescent fluid and touching a planar free fluid-gas interface, is considered. Stick fluid boundary conditions at the sphere surfaces are assumed. The free surface boundary conditions are taken into account with the use of the method of images. For such a quasi-two-dimensional system, the one-sphere resistance operator is calculated numerically. Moreover, the corresponding friction and mobility tensors are constructed from irreducible multipole expansion. Finally, the long-distance terms of the two-sphere mobility tensor are evaluated explicitly up to the order of 1/r3, where r is the interparticle distance. Experiments which have motivated this work are outlined. 相似文献