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41.
Milan Meloun Zuzana Ferenčíková Lucie Netolická Aleš Vrána 《Central European Journal of Chemistry》2011,9(1):66-74
The mixed dissociation constant of naphazoline is determined at various ionic strengths I [mol dm−3] in the range of 0.01 to 0.26 and at temperatures of 25°C and 37°C using ESAB and HYPERQUAD regression analysis of the potentiometric
titration data. A strategy of efficient experimentation is proposed in a protonation constant determination, followed by a
computational strategy for the chemical model with a protonation constant determination. Two group parameters, L
0 and H
T were ill-conditioned in the model and their determination is therefore uncertain. These group parameters, L
0 and H
T, can significantly influence a systematic error in the estimated common parameter pKa and they always should be refined together with pK
a. The thermodynamic dissociation constant pK
aT was estimated by nonlinear regression of {pK
a, I} data at 25°C and 37°C: for naphazoline pK
alT = 10.41(1) and 10.13(2). Goodness-of-fit tests for various regression diagnostics enabled the reliability of the parameter
estimates to be found.
相似文献
42.
The clay mineral montmorillonite has been tested as modifier for the carbon paste electrode with a novel electrode modification technique. The differential pulse voltammetric determination of copper(II) by means of this modified carbon paste electrode has been studied. A detection limit of 4×10-8 mol/l has been achieved after 10 min preconcentration under open circuit conditions with subsequent anodic stripping voltammetry. The calibration curve for Cu(II) is linear in the range of 4×10-8–8×10-7 mol/l. Pb interferes in a 10-fold molar and Cd and Hg in a 100-fold molar excess. The interference by humic ligands is significant. 相似文献
43.
Stanislav Dubniĉka Anna Zuzana Dubniĉkova Jerzy Kraskiewicz Ryszard Raczka 《Zeitschrift fur Physik C Particles and Fields》1995,68(1):153-162
The Körner-Kuroda model of the electromagnetic structure of octet 1/2+ baryons is restored on a more topical physical basis. Electromagnetic radii of baryons under consideration are calculated and compared with other model predictions. By an incorporation of a two-cut approximation of correct form factor analytic properties and nonzero vector-meson widths, the Körner-Kuroda model is unitarized, providing in this manner imaginary parts of the octet 1/2+ baryon form factors to be nonzero just starting from a branch point corresponding to the lowest threshold. 相似文献
44.
Zuzana Málková Josef Novák Vra Hamplová Zdena Pokorná 《Fresenius' Journal of Analytical Chemistry》1993,347(12):478-479
Summary A photometric method is described for determining the oxygen balance in oxide superconductors. It is based on the oxidation of Fe2+ to Fe3+ by the superconductors and the following determination of the residual Fe2+ ions as complex with 1,10-phenanthroline. Hydrobromic acid is used for dissolving the samples. The method has been developed for 10 mg sample weights. Good reliability of the method was verified by comparison with the cerimetric determination using 80 mg samples. 相似文献
45.
The characteristic properties of the principal solution for half-linear differential equation
(a(t)Φ(x′))′+b(t)Φ(x)=0, 相似文献
46.
47.
Jitka Kuldov Peter Koovan Zuzana Limpouchov Karel Prochzka 《Macromolecular theory and simulations》2013,22(1):61-70
We present a computer study of the association behavior of copolymer chains with a gradient part and soluble tail of variable length. As a simulation method we use dynamic Monte Carlo simulation on a simple cubic lattice with pair interaction parameters. The solvent quality and selectivity is modeled by the variation of pair interaction parameters between nearest neighbors on the lattice. The role of the length of soluble part in the self‐assembly and its effect on the structure of aggregates was the main goal of this work. The size and structure of aggregates were analyzed using an improved topological classification method which has been developed and tested in the present study. The structure and association numbers of aggregates were compared with those of linear diblock copolymers.
48.
49.
Martina Havlikova Radomir Cabala Vera Pacakova Miroslava Bursova Zuzana Bosakova 《Journal of separation science》2019,42(1):273-284
Sample pretreatment techniques or preconcentration constitute a very important step before the analysis of environmental, clinical, pharmaceutical, and other complex samples. Thanks to extraction techniques it is possible to achieve higher method sensitivities and selectivities. Miniaturization microextraction methods make them more environmentally friendly and only small amounts of samples are required. In the past 30 years, a number of microextraction methods have been developed and used and are documented in thousands of articles. Many reviews have been written focusing on their use in specified professional fields or on the latest trends. Unfortunately, no uniform nomenclature has been introduced for these methods. Therefore, this review attempts to classify all the essential microextraction techniques and describes their advantages, disadvantages, and the latest innovations. The methods are divided into two main groups: single drop and sorbent‐based techniques according to the type of extraction phase. 相似文献
50.
Lenka Morávková Ondřej Vopička Jiří Vejražka Hana Vychodilová Zuzana Sedláková Karel Friess Pavel Izák 《Chemical Papers》2014,68(12):1739-1746
The emissions of hydrocarbons from fossil fuels into atmosphere entail both an economic loss and an environmental pollution. Membrane separations can be used for vapour recovery and/or vapour removal from the permanent gas stream, given that the appropriate membrane is identified. A neat poly(vinylidene fluoride-co-hexafluoropropylene) membrane is impermeable to both the representatives of aliphatic hydrocarbons and branched hydrocarbons, namely hexane and isooctane, whereas the permeation flux is enhanced by the presence of 80 mass % of the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulphonyl)imide in the membrane, as detailed in this work. The permeabilities of hydrocarbon vapours were determined from the binary mixture containing hydrocarbon and nitrogen to simulate the real input of an air stream containing a condensable hydrocarbon. The diffusion coefficient determined from sorption measurements was higher for hexane, as would be expected for a smaller molecule, whereas both the sorption isotherms and permeabilities of the hydrocarbons studied were found to be almost identical. It is possible that the sorption effect predominates in the transport mechanism for VOCs/N2 separations. 相似文献