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61.
We show that if is an -regular set in for which the triple integral of the Menger curvature is finite and if , then almost all of can be covered with countably many curves. We give an example to show that this is false for .
62.
63.
Two-dimensional thermal field-flow fractionation (2D-ThFFF) is a new instrumental technique devised for continuous fractionation of soluble macromolecules and particles. The sample mixture is introduced into a disc-shaped channel and the separated sample components are collected continuously from the channel outlets. The method is based on a two-dimensional fractionation mechanism with radial and tangential flow components in the channel. The effects of flow components and thermal gradient on the fractionation were studied in the separation of polystyrene samples of different molecular masses using cyclohexane or a binary solvent consisting of 25% ethylbenzene and 75% cyclohexane as carrier. The continuous separation of polystyrene samples was improved with increasing thermal gradient and with the use of slow radial and tangential flow rates. The technique can be applied to preparative continuous separation of macromolecules. 相似文献
64.
Alexei Babkin Harry Alles Pertti Hakonen Alexander Parshin Juusi Ruutu Jari Saram?ki 《Czechoslovak Journal of Physics》1996,46(Z1):465-466
The equilibrium shape ofhcp
4He crystals has been studied at temperatures 0.05≤T≤0.7 K by means of a high precision optical interferometer. We find that the profile of the interfacial boundary, close to
an almost horizontal c-facet, has a well-defined slope discontinuity separating two angular regions with different behavior
of the surface stiffness. For surfaces tilted by an angle ϕ≤100 μrad with respect to the c-facet, we obtain, contrary to the linear angular dependence predicted by current theories. 相似文献
65.
A systematic investigation of structurally identical flame retardant viscose, modal and polyester blended fabrics and fibres was carried out in order to develop a chemical basis for more effective products based on organic and inorganic flame retardants. The oxygen indices and chemical compositions of phosphorus-nitrogen flame retardants (P-N) were used in efficiency and synergy evaluations. A new flame retardant viscose fibre containing silicid acid was included in the comparative evaluation procedure. Thermal gravimetry and X-ray diffractometry were used for determine physical factors during pyrolyzing of fibres. Charred residues were analyzed by applying elementary and solid 13-C NMR (CPMAS) spectrometry. The pyrolysis gas-liquid chromatographer connected with a gas phase FT infrared spectrometer was applied to identify the decomposition products of P-N-containing fabrics. 相似文献
66.
DNA or protein adducts are reaction products of endogenous or exogenous chemicals and cellular macromolecules. Adducts are
useful in toxicological studies and/or human biomonitoring exercises. In particular, DNA damage provides invaluable information
for risk analysis. Second, metabolites or conjugates can be regarded as markers of phase II reactions though they may not
give accurate information about the levels of reactive and damage-provoking reactive compounds or intermediates. Electrophiles
are often short-lived molecules and therefore difficult to monitor. In contrast, adducts are often chemically stable, though
their levels in biological samples are low, which makes their detection challenging. The assay of adducts is similar to the
analysis of any other trace organic molecule, i.e. problems with the matrix and small amounts of analytes in samples. The
32P-postlabelling assay is a specific method for DNA adducts but immunochemical and fluorescence-based methods have been developed
which can detect adducts linked to both DNA and protein. Tandem mass spectrometry, particularly if combined with ultrahigh-performance
liquid chromatography, is currently the recommended detection technique; however investigators are striving to develop novel
ways to achieve greater sensitivity. Standards are a prerequisite in adduct analysis, but unfortunately they are seldom commercially
available. 相似文献
67.
Holding pressure was expected to change the free flow of the liquid crystalline melt. Because of the complex mold used and the two variables, nozzle and mold temperature, the shear and elongational flow were in the injection molding study evaluated by means of the notched Charpy and Izod impact strength. The tensile modulus, the flexural strength and modulus mainly depended on the elongational flow induced skin. On the grounds of the microstructure composed of 4 distinct layers a free flow model of the liquid crystal polymer having a yield stress is proposed. 相似文献
68.
The relationship between vocal fold strain and vocal pitch in singersand nonsingers singing a rising pitch series has been indirectly investigated by means of lateral radiographs. Nonsingers tend to exhibit more strain than singers. To standardize the degree of strain, an index of strain per semitone is proposed. The semitone strain indicates the average amount of strain per 1 semitone of pitch increase or decrease. The index has been shown to be affected by several factors: gender, singing training, singing technique, voice class, age, and status of muscle function. Observations suggest that similar groups of individuals occupy different positions on the stress-strain curve, indicated by their semitone strain values. 相似文献
69.
Anne Vuorema Mika Sillanpää Marianna Vehviläinen Taina Kamppuri Pertti Nousiainen Wim Thielemans Frank Marken 《Electroanalysis》2013,25(7):1773-1779
Reconstituted cellulose spontaneously self‐assembles at surfaces from an alkaline cellulose solution (ca. 1 wt%, pH 14, prepared with an enzymatic method from wood pulp) into porous films with approximately 300 nm thickness per layer, for example onto immersed tin‐doped indium oxide (ITO) electrodes. Sequential multi‐layer deposition allows control over the thickness of the assembled films. The hydrophilic properties of the cellulose film electrodes are utilised here (i) as dip‐probe with capillary force picking up sample solution and (ii) as flow‐through generator‐collector probe, for example for future application in in situ chromatographic separation in end‐column detection with nano‐molar sensitivity. 相似文献
70.
Ari Seppälä Arttu Meriläinen Lisa Wikström Pertti Kauranen 《Experimental Thermal and Fluid Science》2010,34(5):523-527
Some liquids can be kept in a supercooled or supersaturated metastable state for substantially long periods. Such liquids can be applied as long-term heat storage where the latent heat can be released when needed. As xylitol possesses a relatively high value of latent heat and as it can be easily supercooled, it has promising properties for this application. However, the speed of the crystallization of xylitol is low, leading to a low release rate of latent heat.Several additives have been experimentally tested for the purpose of accelerating the crystallization speed. The effect of the additives on the latent heat, on the melting temperatures, and on the long-term durability of the supercooled state was also measured.The highest speeds of the crystallization front, at a temperature of 22 °C, were achieved with methanol as an additive leading to speeds 33 times higher in vertical experiments and in 170 times higher in horizontal ones than with pure xylitol. The improved speed of the crystallization front is mostly caused by the methanol flow currents generated as a result of the separation of methanol during crystallization, and to a lesser extent, as a result of the increase in the speed of the growth of the crystals. 相似文献