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1.
Bucataru Ioan Constantinescu Oana Creţu Georgeta 《Annals of Global Analysis and Geometry》2022,62(4):815-827
Annals of Global Analysis and Geometry - We prove that in a Finsler manifold with vanishing $$\chi $$ -curvature (in particular with constant flag curvature) some non-Riemannian geometric... 相似文献
2.
Juliu Voicu 《Colloid and polymer science》1934,67(2):148-154
Zusammenfassung Die an den in einer vorangehenden Abhandlung aufgestellten Gleichungen der wiederholten Auszüge xp=(x0
p- K) (1−r)pq+K (A) oder xp=Ax(1−r)pq+K (a)θ
p=θ
0
p
−K
θ
)(1−r)pq+K
θ
(B) oderθ
p=A
θ
(1−r)pq+K
θ
(b) angestellten überlegungen betrafen unter anderem die Bestimmung der Parameter Ax, A
θ
, K und K
θ
durch graphische Darstellung. Es wurde auch der auf die Werte von K und K
θ
ausgeübte Einflu?, der durch ?nderung von m, der Menge des Adsorbenten, und von V, des Volumens der L?sung, infolge einer
?nderung in der quantitativen Zusammensetzung des Systems entstand, er?rtert.
Es wurde auf die Verkleinerung von K und K
θ
, die nach einer gewissen Zahl von Auszügen infolge einer zu starken Verdünnung der L?sung des Systems eintreten mu?, aufmerksam
gemacht. Diese Verkleinerung erkl?rt sich aus der Anwesenheit des Koeffizienten a und des Exponenten n der Adsorptionsisotherme
in den Gleichungen
; denn die beiden Werte von α und n sind nur für einen beschr?nkten Konzentrationsbereich praktisch konstant.
Es wurde auch gefunden, da? die Werte vonθ, der Substanzmenge in L?sung, oder von x, der Konzentration in 1 ccm, die nach einem Auszug einer beliebigen Ordnung bestimmt
wurden, den Gleichungen (b) und (a) für die Werte p′ von p, die andere sind als der zum untersuchten System geh?rende Wert,
genügen unter der Bedingung, für K, K
θ
, Ax und A
θ
angemessene Werte zu finden. Die oben erw?hnte Schlu?folgerung gilt auch für p=1. Man erh?lt die beiden Gleichungen x=A′(1−r)q+ K′ (E)θ=A (1−r)q+K′θ, (F) die x undθ, die einer Auszugsordnung q entsprechen, direkt ergeben. Die Parameter A′, A, K′ und K′θ k?nnen graphisch ermittelt werden.
Multipliziert man die Gleichung (F) mit r, dem bei dem Auszug entnommenen Volumteil, so erh?lt man die dem System durch einen
Auszug entzogene Substanzmenge aq: aq=rA(1−r)q−1+ c, (G) wo c=rK′θ.
Am Schlu? der Abhandlung wird auf bestimmte Vorteile der Gleichungen (F) und (G) aufmerksam gemacht.
I. Teil: Kolloid-Z.66, 322 (1934).
übersetzt von E. Lottermoser (Leipzig). 相似文献
3.
D. Berger C. Matei F. Papa G. Voicu V. Fruth 《Progress in Solid State Chemistry》2007,35(2-4):183-191
We report the synthesis of La1−xSrxCoO3 nanopowders by solution combustion method using metal nitrates and -alanine (alanine method) or urea (urea method) as fuel. The influence of metal nitrates/organic substance molar ratio and the type of fuel was investigated. The isolated complex precursors were characterized by atomic absorption spectroscopy (AAS), FT-IR spectra and DTA–TG analysis. The La1−xSrxCoO3 (x = 0–0.3) powders were characterized by X-ray diffraction (XRD), scanning electron microscopy–energy-dispersive X-ray analysis (SEM–EDX), as well as by specific surface area measurements. XRD patterns indicate the formation of single-phase LaCoO3 (rhombohedral) when as-synthesized powders were calcined at 873 K, 3 h in the case of the alanine method and at 1073 K, 3 h for urea-based system. Also, strontium doped lanthanum cobaltites obtained by both methods at 1273 K are single phase with rhombohedral perovskite-like structure as XRD data have proved. SEM investigation of pure and doped lanthanum cobaltites reveal that the samples prepared by both methods have fine particles with tendency of agglomerates formation with different shapes, spongy aspect and high porosity. La1−xSrxCoO3 nanopowders obtained by alanine method have larger specific surface area values than those prepared by urea method. 相似文献
4.
Summary A new type of liquid-membrane iodide-selective electrode based on a 0.001M solution of tris(l,10-phenanthroline)ruthenium(II) iodide in 1,2-dichlorobenzene is described. The electrode has Nernstian behaviour down to 7×1O–6M iodide. It has good selectivity towards halide (k
I, Cl=5.3×10–6 andk
I, Br=1.6×10–4) and other inorganic ions, and a linear response to iodide at pH-values from 3 to 9. It can be used either in direct iodide analyses or in potentiometric titrations. Titration of halide mixtures or of pseudohalides is also possible. The method has been used for determining the free formaldehyde present in dispersing agents.
Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980. 相似文献
Herstellung und analytische Anwendung einer jodid-spezifischen Elektrode mit Flüssigmembran mit einem Metallkomplex als Austauscher
Zusammenfassung Eine neue jodid-spezifische Flüssig-Membran-Elektrode auf der Basis einer 0,001 M Lösung von Tris(1,10-phenanthrolin)-Ruthenium(II)-jodid in 1,2-Dichlorbenzol wurde beschrieben. Sie zeigt Nernstsches Verhalten bis zu 7×10–8 M Jodid, gute Selektivität gegenüber Halogeniden (k I, Cl=5,3× 10–6 undk I, Br=1,6×10–4) und anderen anorganischen Ionen und ein lineares Verhalten gegenüber Jodid bei pH 3–9. Die Elektrode läßt sich für direkte Jodidbestimmungen oder für potentiometrische Titrationen verwenden. Die Titration von Halogenidgemischen oder Pseudohalogeniden ist ebenfalls möglich. Das Verfahren wurde zur Bestimmung von freiem Formaldehyd in Dispersionsmitteln verwendet.
Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980. 相似文献
5.
Luminita Georgeta Confederat Cristina Gabriela Tuchilus Maria Dragan Mousa Shaat Oana Maria Dragostin 《Molecules (Basel, Switzerland)》2021,26(12)
Despite the advantages presented by synthetic polymers such as strength and durability, the lack of biodegradability associated with the persistence in the environment for a long time turned the attention of researchers to natural polymers. Being biodegradable, biopolymers proved to be extremely beneficial to the environment. At present, they represent an important class of materials with applications in all economic sectors, but also in medicine. They find applications as absorbers, cosmetics, controlled drug delivery, tissue engineering, etc. Chitosan is one of the natural polymers which raised a strong interest for researchers due to some exceptional properties such as biodegradability, biocompatibility, nontoxicity, non-antigenicity, low-cost and numerous pharmacological properties as antimicrobial, antitumor, antioxidant, antidiabetic, immunoenhancing. In addition to this, the free amino and hydroxyl groups make it susceptible to a series of structural modulations, obtaining some derivatives with different biomedical applications. This review approaches the physico-chemical and pharmacological properties of chitosan and its derivatives, focusing on the antimicrobial potential including mechanism of action, factors that influence the antimicrobial activity and the activity against resistant strains, topics of great interest in the context of the concern raised by the available therapeutic options for infections, especially with resistant strains. 相似文献
6.
L. C. Nistor S. V. Nistor V. Teodorescu I. Voicu 《Crystal Research and Technology》1979,14(12):1525-1528
Single crystals of CaF2 doped with ThO2 were grown by the Czochralski-Kyropoulos technique in graphite crucibles. The distribution of thorium in the as grown crystals has been investigated by optical and transmission electron microscopy, selected area diffraction and optical spectroscopy. 相似文献
7.
L. Gavrila FlorescuE. Vasile I. SanduI. Soare C. FleacaR. Ianchis C. LuculescuE. Dutu R. BirjegaI. Morjan I. Voicu 《Applied Surface Science》2011,257(12):5270-5273
The work presents preliminary studies with the goal to extend the share of long graphene ribbons in laser-synthesized carbon black. Investigations revealed the existence, as a major constituent, of graphene ribbons composed of up to 10-15 graphene layers, spaced at ∼0.35-0.37 nm and of tens of nanometres in length. The samples used to study the development of this specific structure were obtained from sensitized acetylene-based mixtures and the experiments were performed following the variation of both the experimental parameters and gas composition. 相似文献
8.
Popescu C. Voicu I. Alexandrescu R. Morjan I. Dumitras D. Popescu M. Fatu D. 《Journal of Thermal Analysis and Calorimetry》1999,56(1):183-189
This paper reports on the synthesis of various iron oxides by the IR laser processing of different iron salts. X-ray diffraction
techniques were used to characterize the reaction products. Some differences in terms of crystallite size and isotropy between
these oxides and those obtained from the same salt by thermal means are described and explained.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
9.
Dolocan VO 《J Phys Condens Matter》2011,23(44):446005
The spin-wave modes of cylindrical nanowires of moderate diameter-to-length ratios are investigated in this paper. Based on three-dimensional simulations and analytical calculations we determine the spatial structures of the modes. We show that standing spin waves and localized edge modes form the discrete spectrum of the nanowires. Using a simple analytical model we infer an extended dispersion relation for spin waves in cylinders. Considering the variation of the demagnetizing (internal) field we show that the localized dipole-exchange modes at the edges are always present. 相似文献
10.
Emil C. Buruiana Tinca Buruiana Georgeta Strat Mitachi Strat 《Journal of polymer science. Part A, Polymer chemistry》2005,43(17):3945-3956
Hydrophilic ionic polyurethanes with 4‐chloromethylphenylcarbamoyl‐1‐oxymethylpyrene located on the quaternary ammonium structure from a polymer based on poly(ethylene glycol), isophorone diisocyanate, and N‐methyldiethanolamine were prepared by a quaternization reaction, in which the amount of pyrene covalently attached to the polymeric backbone ranged from 1.14 to 19.82 mmol of fluorophore/100 g of polymer. It was interesting to compare the photoluminescence of the pyrene polyurethane carrying a few mole percent of pyrene moieties with that of a third polymer resulting from its subsequent quaternization with benzyl chloride up to a concentration of ionic groups as in the latter (quaternization degree = 14.15%). The process of excimer formation between the pyrene molecules attached to the ionic polyurethane was investigated in tetrahydrofuran (THF), dimethylformamide, film, and THF/H2O to illustrate the expected differences in the polymer behavior compared with that of the starting pyrene derivative. The formation of aggregates or core–shell micelles was sustained by the fluorescence data, which indicated the existence of pyrene units in the ground state of the molecule, giving rise thus to an explanation for the high excimer‐to‐monomer intensity ratio. The fluorescence decay of pyrene polyurethanes in the presence of various concentrations of nitrobenzene used as a quencher was analyzed too when the fluorescence quenching in the polymer solution normally followed Stern–Volmer kinetics. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3945–3956, 2005 相似文献