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排序方式: 共有67条查询结果,搜索用时 78 毫秒
1.
Zbigniew Gregorowicz Barbara Piwowarska Franciszek Buhl und Krystyna Kania 《Fresenius' Journal of Analytical Chemistry》1968,237(5):347-351
Zusammenfassung Es wurde eine UV-spektrophotometrische Methode zur Bestimmung der 2,2-Dicinchoninsäure beschrieben. Messung erfolgt bei pH 10 bei dem Absorptionsmaximum von 260 nm. Der Bestimmungsbereich beträgt 1,71–20,52 g der 2,2-Dicinchonin-Ionen in 25 ml Lösung. Ba2+, Sr2+, Ca2+, Mg2+, Ni2+, Co2+, Zn2+, Hg2+ und Al3+ in 100fachem sowie Pb2+ in 10fachem Überschuß verursachen keine Störungen. Blei in 20 fachem sowie Ag+ und Hg2
2+ in einfachem Überschuß verursachen Ausscheidung von Niederschlägen.
Summary An UV-spectrophotometric method for the determination of 2,2-dicinchonic acid is described. The absorption is measured in a solution of pH 10 at the maximum of 260 nm.The range of application of the method was 1,71 to 20,52 g of DC2– ions in 25 ml of solution. Ba2+, Sr2+, Ca2+, Mg2+, Ni2+, Co2+, Al3+, Zn2+, Hg2+ ions present in hundredfold excess do not interfere with the determination. Ag+, Hg2 2+ ions in one-fold and Pb2+ ion in twenty-fold excess cause the deposition of a precipitate, but five-fold and ten-fold excess of Pb2+ does not interfere.相似文献
2.
We prove that a WLD subspace of the space consisting of all bounded, countably supported functions on a set Γ embeds isomorphically into if and only if it does not contain isometric copies of . Moreover, a subspace of is constructed that has an unconditional basis, does not embed into , and whose every weakly compact subset is separable (in particular, it cannot contain any isomorphic copies of ). 相似文献
3.
PbYb1/2Ta1/2O3 single crystals were obtained for the first time. They were grown by the flux method. The PbOPbF2B2O3 system was used as a solvent. Dielectric investigations were carried out in 1 0 0c, 1 1 0c and 1 1 1c pseudocubic directions. These studies pointed to anisotropy of dielectric properties. Frequency-independent ε′(T) and ε″(T) maxima related to the antiferroelectric–paraelectric (AFE—PE) phase transition are observed for all directions at 562 K. The frequency-dependent ε′(T) and ε″(T) maxima near 400 K related to the ferroelectric (FE)–AFE phase transition are observed only in 1 1 1c direction. The hysteresis loops were observed in this direction only. These results point that ferroelectric relaxor properties appear only in 1 1 1c direction. We propose to consider the ferroelectric phase as ferrielectric one. 相似文献
4.
The paper is devoted to local and global solvability in locally uniform spaces and to the existence of a global attractor for a parabolic problem containing fractional power of the minus Laplace operator. Several useful technical tools and estimates are also collected in this paper. 相似文献
5.
Thomas Kania Boris Schilder Thilo Kissel Peter Stephan Steffen Hardt Andreas Dreizler 《Flow, Turbulence and Combustion》2013,90(4):741-761
New developments in portable electrical and mechanical devices have created demand for increasing amounts of energy and thus new ways of supplying energy. The high energy density of hydrocarbon fuels are a possible way to solve this issue. This paper deals with the development of an adapted thermodynamic concept for a micro energy converter based on the thermoelectric effect. Developing a PowerMEMS device that does not contain any moving parts is the main design feature. In the proposed concept liquid hydrocarbon fuel, such as methanol, is evaporated in a micro evaporator, mixed with air, and combusted in a micro combustion chamber. The combustion process is assisted by catalytically coated microfibers. Electrical power can be generated by a thermoelectric generator, which is located between the hot combustion zone and the cold micro evaporator. This arrangement leads to large temperature differences between hot and cold junctions, which is necessary for efficient thermoelectric energy conversion and hence power generation. For a more detailed investigation of thermal boundary conditions and interior thermal management, in-situ temperature measurements of the combustor walls are performed using thermographic phosphors. 相似文献
6.
The transition between insulator and metal conductor states, induced by oxygen non-stoichiometry, was studied for NaNbO3 : Mn crystals. Conditions for an optimal reduction were determined on the basis of TGA tests. The temperature dependencies of the resistance measured on the macroscale showed that the transition from thermally activated to metallic features depends on the level of oxygen deficiency. The LC-AFM measurement exhibited non-homogeneous electric resistance on the nanoscale. We ascribed the local insulator–metal transition to changeover in the electronic state of the Nb ions occurring in filaments. The Mn dopant stabilised the induced oxygen non-stoichiometry and the metallic conduction down to room temperature. 相似文献
7.
X-ray powder diffraction patterns of the AgNbO3 have been obtained in a wide temperature range: from room temperature up to 850 K. The type of distortion and the multiplicity of the pseudo-cubic perovskite cell has been determined from the splitting of the main diffraction lines and from analysis of the superlattice peaks. The scheme of oxygen octahedra tilting and the sequence of the distorted pseudocubic cell is: <artwork name="GPHT21121eu1"> 相似文献
8.
Sophia Boden Franziska Reise Jessica Kania Thisbe K. Lindhorst Laura Hartmann 《Macromolecular bioscience》2019,19(4)
This study investigates the influence of an increasingly hydrophobic backbone of multivalent glycomimetics based on sequence‐defined oligo(amidoamines) on their resulting affinity toward bacterial lectins. Glycomacromolecules are obtained by stepwise assembly of tailor‐made building blocks on solid support, using both hydrophobic aliphatic and aromatic building blocks to enable a gradual change in hydrophobicity of the backbone. Their binding behavior toward model lectin Concanavalin A (ConA) is evaluated using isothermal titration calorimetry (ITC) and surface plasmon resonance (SPR) showing higher affinities for glycomacromolecules with higher content of hydrophobic and aromatic moieties in the backbone. Finally, glycomacromolecules are tested in a bacterial adhesion inhibition study against Escherichia coli where more hydrophobic backbones yield higher inhibitory potentials most likely due to additional secondary interactions with hydrophobic regions of the protein receptor as well as a change in conformation exposing carbohydrate ligands for increased binding. Overall, the results highlight the influence and thereby importance of the polymer backbone itself on the resulting properties of polymeric biomimetics. 相似文献
9.
The axial coordination of central Mg(2+) ion in chlorophylls is of great structural and functional importance for virtually all photosynthetic chlorophyll proteins; however, little thermodynamic data are available on the ligand binding to these pigments. In the present study, spectral deconvolution of the bacteriochlorophyll Q(X) band serves to determine the ligand binding equilibria and relationships between thermodynamic parameters of ligand binding, ligand properties, and steric interactions occurring within the pigment. On the basis of the temperature effects on coordination, DeltaH degrees, DeltaS degrees, and DeltaG degrees of binding various types of ligands (acetone, dimethylformamide, imidazole, and pyridine) to diastereoisomeric bacteriochlorophylls were derived from respective van't Hoff's plots. At ambient temperatures, only ligation by imidazole and pyridine occurs spontaneously while DeltaG degrees becomes positive for ligation by acetone and dimethylformamide, due to a relatively large entropic effect, which is dominating when the energetic effects of ligation are small. It reflects, in quantitative terms, the control of the equatorial coordination of the Mg(2+) ion via the axial coordination: a "hard" free Mg(2+) ion is made into a softer center through the coordination of tetrapyrrole. Pigment structural features have comparable effects on the energetic and entropic contributions to the difference of ligation free energy between the diastereoisomers of bacteriochlorophyll. DeltaS degrees and DeltaH degrees values are consistently lower for the S epimer, most likely due to the steric crowding between bulky substituents. The two epimers show a 5 J.mol(-1).K(-1) difference in DeltaS degrees values, regardless of the ligand type, while the difference in DeltaH degrees amounts to 1.7 kJ.mol(-1), depending on the ligand. Such steric control of ligation would relate to the partial diastereoselectivity of chlorophyll self-assembly and, in particular, the very high diastereoselectivity of the ligation of chlorophylls in photosynthetic proteins. 相似文献
10.
Adamczyk K Candelaresi M Kania R Robb K Bellota-Antón C Greetham GM Pollard MR Towrie M Parker AW Hoskisson PA Tucker NP Hunt NT 《Physical chemistry chemical physics : PCCP》2012,14(20):7411-7419
The ultrafast equilibrium fluctuations of the Fe(III)-NO complex of a single point mutation of Myoglobin (H64Q) have been studied using Fourier Transform 2D-IR spectroscopy. Comparison with data from wild type Myoglobin (wt-Mb) shows the presence of two conformational substates of the mutant haem pocket where only one exists in the wild type form. One of the substates of the mutant exhibits an almost identical NO stretching frequency and spectral diffusion dynamics to wt-Mb while the other is distinctly different in both respects. The remarkably contrasting dynamics are largely attributable to interactions between the NO ligand and a nearby distal side chain which provides a basis for understanding the roles of these side chains in other ferric haem proteins. 相似文献