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1.
A procedure for the generation of slanted gas-filled icicles by freezing, using a domestic refrigerator, is described. The freezing vessel was a plastic ice-cube tray, which was filled both with tap and deionized water and was frozen successively from the outer to the inner compartments of the tray. Icicles having slanted elevations grew out of the surface of the deionized water of the innermost compartments. The erection angle of the icicles to the horizontal lay between 30° and 60°, for the three longest and thinnest specimens it was almost exactly 30°. All icicles have gas inclusions. Their shape varies between an irregular distribution of circular bubbles and a nearly uninterrupted axial gas channel together with dendrite-like, radially distorted bubbles. If a cold (-18°C) specimen comes into contact with warm and humid room-air, then hoarfrost is observed at the bottom and the top of the icicle, while the area in between remains transparent. 相似文献
2.
A solid state extrusion technique is applied as to produce oriented block copoly(ether ester) under various physical conditions. The morphology of the extruded samples is characterized in relation to the extrusion parameters and hard segment compositions of the polymer, using thermal analysis and X-ray methods. The lateral dimensions of the crystalline domains are found to be approximately 150 Å depending on the extrusion conditions. The statistics of the long range periodicity of the structure along the extrusion direction is in agreement with a one-dimensional two phase model, the crystalline portion of which does not vary much in thickness (35 – 45 Å). The unexpected increase in the long period and the thermal shrinkage suggest the existence of strained interlamellar amorphous chains (tie molecules). The observed variations in tensile properties are interpreted under the assumption that both the number of such tie molecules and their fully extended lengths are determined by the hard segment composition and the extrusion conditions. It is also argued that the increase in the glass transition temperature is not only a function of the composition of hard segments in the amorphous phase but also of the number of strained tie molecules.Herrn Dr. Dr. h. c. H. Hellmann zum 70. Geburtstag gewidmet.Part 3 cf. lit [11] 相似文献
3.
E. Lüscher 《Mikrochimica acta》1955,43(2-3):696-702
Zusammenfassung Es wird zunächst ein Überblick über die wichtigsten Arbeiten auf dem Gebiet der Röntgenstrahlenemissionsspektrographie gegeben. Dann wird der prinzipielle Aufbau des Röntgenstrahlen- Quantometers erläutert. Der Spektralbereich für dispersive Messungen geht von 0,6 Å bis 3,1 Å. Als Energiedetektoren werden Geiger-Müller-Zählrohre und Szintillationszähler verwendet. Als Analysatoren werden ebene und zylindrische Einkristalle verwendet. Mit der nichtdispersiven Anordnung wurde eine Bestimmung von Blei und Brom in Benzin durchgeführt.
Summary The most important work in the range ofX-Ray emission spectrography and the basic construction of theX-Ray Quantometer are described. The spectral range for dispersive measurements goes from 0.6 to 3.1 Å. Geiger-Müller counters and scintillation counters are used as energy-detectors. Plain and cylindric mono-crystals are used as analysators. With the nondispersive arrangement a determination of lead and bromide in benzine is made.
Résumé Un aperçu des travaux importants dans le domaine de la spectrographie d'émission à rayonsX est donné. La construction de base du quantomètre est ensuite démontrée. La région spectrale pour les mesures dispersives s'étend de 0,6 à 3,1 Å. On utilise des compteurs Geiger-Müller et des compteurs de scintillation comme détecteurs d'énergie. Comme analysateurs on utilise de mono-cristaux planes ou cylindriques. La détermination du plomb et du bromide dans la benzine est faite grâce à l'utilisation du dispositiv nondispersif.相似文献
4.
The magnetic susceptibility of liquid NaSb alloys was measured in a temperature range between 600°C and 1100°C. The NaSb system is supposed to exhibit, as does the CsSb system, a metal to semiconductor transition dependent upon composition. A relatively strong diamagnetic minimum of x = ?26 × 10?6 cm3/mol was found near the composition of the stoichiometric formula Na3Sb. This minimal susceptibility can be relatively well described with an ionic type binding model. 相似文献
5.
The annealing induced morphological changes in isotropic block copoly(etherester)s are investigated by small angle X-ray scattering methods. The observed results are consistent with a lamellar model which is comprised of a crystalline core of thickness 35 to 45 Å, a diffuse boundary zone of width 9 Å, and an amorphous layer which is varying strongly in thickness. The enhanced crystallinity of the samples annealed at higher temperatures is mainly due the lateral growth of the lamellae; the long period increases by not more than 20%. The scattering power of the samples is explained by means of an equivalent two-phase model in which the crystalline phase has the same structure as theα-form of poly(butylene terephthalate), whereas the amorphous phase is a mixture of the uncrystallized ester segments and the ether segments. The crystallinity determined from the scattering power is very much higher than that determined from thermoanalytical investigations. 相似文献
6.
M. Lüscher 《Communications in Mathematical Physics》1976,50(1):23-52
Let 1(x) and 2(y) be two local fields in a conformal quantum field theory (CQFT) in two dimensional spacetime. It is then shown that the vector-valued distribution 1(x)2(y)|0 is a boundary value of a vectorvalued holomorphic function which is defined on a large conformally invariant domain. By group theoretical arguments alone it is proved that 1(x)2(y)|0 can be expanded into conformal partial waves. These have all the properties of a global version of Wilson's operator product expansions when applied to the vacuum state |0. Finally, the corresponding calculations are carried out more explicitly in the Thirring model. Here, a complete set of local conformally covariant fields is found, which is closed under vacuum expansion of any two it its elements (a vacuum expansion is an operator product expansion applied to the vacuum).Work supported by Deutsche Forschungsgemeinschaft 相似文献
7.
Enzyme immobilization is a technology that enables (bio-)catalysts to be applied in continuous-flow systems. However, there is a plethora of immobilization methods available with individual advantages and disadvantages. Here, we assessed the influence of simple and readily available methods with respect to the performance of 2-deoxy-d-ribose-5-phosphate aldolase (DERA) in continuous-flow conditions. The investigated immobilization strategies cover the unspecific attachment to carriers via epoxides, affinity-based attachment via metal ion affinity, StrepTag™-StrepTactin™ interaction as well as the covalent affinity attachment of an enzyme to a matrix tethered by the HaloTag®. The metal-ion-affinity-based approach outperformed the other methods in terms of immobilized activity and stability under applied conditions. As most enzymes examined today already have a HisTag for purification purposes, effective immobilization may be applied, as simple as a standard purification, if needed. 相似文献
8.
Thomas Ihn Susanne Dröscher Stephan Schnez Helena Knowles Johannes Güttinger Magdalena Huefner Christoph Stampfer Yigal Meir Klaus Ensslin 《Solid State Communications》2012,152(15):1306-1310
We report two experiments on graphene nanostructures. The first was performed on a graphene nanoribbon, where the nature of electronic transport was investigated in detail. Electrons or holes are found to localize in pockets of the potential along the ribbon. Transport is governed by the joint action of localization and Coulomb interaction. The temperature-dependence of the conductance shows activated behavior at temperatures above a few Kelvin. The activation energy retraces the edges of Coulomb blockade diamonds found in nonlinear transport. In the second experiment the metallic tip of a low-temperature scanning force microscope was scanned above a graphene quantum dot. In addition to the familiar Coulomb blockade fringes, localized states are detected forming in the constrictions connecting the dot to source and drain. 相似文献
9.
Lüscher S Moore LS Rejec T Meir Y Shtrikman H Goldhaber-Gordon D 《Physical review letters》2007,98(19):196805
Compressibility measurements are performed on a quantum point contact (QPC). Screening due to mobile charges in the QPC is measured quantitatively, using a second point contact. These measurements are performed from pinch-off through the opening of the first few modes in the QPC. While the measured signal closely matches a Thomas-Fermi-Poisson prediction, deviations from the classical behavior are apparent near the openings of the different modes. Density functional calculations attribute the deviations to a combination of a diverging density of states at the opening of each one-dimensional mode and exchange interaction, which is strongest for the first mode. 相似文献
10.