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排序方式: 共有97条查询结果,搜索用时 15 毫秒
1.
Hermann Jahnke 《OR Spectrum》1993,15(1):21-30
Zusammenfassung Eine Lagerzielmengenpolitik für den Fall intermittierender Fertigung mehrerer Sorten auf einer Anlage bei stochastischer Nachfrage wird durch ein Warteschlangenmodell abgebildet. Für die sich ergebenden Kostenfunktion wird eine Approximation vorgeschlagen. Die Bestimmung optimaler Losgrößen und Lagerzielmengen wird untersucht. 相似文献
2.
Cortical spreading depression is a wave of electrical and biochemical changes that spreads across the cerebral cortex. It has been hypothesized to be an important underlying cause of the visual disturbances occurring during the migraine aura, but this is difficult to test in animals or humans. We created a computational model of cortical spreading depression and found that during the wave of biochemical changes the spatial pattern of neural activity broke up into irregular patterns of lines and small patches of highly activated elements. The corresponding visual disturbances that would be produced by these patterns of neural activity resemble the hallucinations reported during the migraine aura, providing strong support for the cortical spreading depression hypothesis of migraine. The model also makes the testable prediction that these hallucinations move at an exponentially increasing speed across the visual field. 相似文献
3.
The influence of different precipitation treatments upon the radiation-induced void formation was studied on an Al-Mg-Si alloy and the results were compared with those obtained on high-purity Al. The changes in the microstructure and the void formation were investigated by TEM methods for the dose range 0.8 to 80 dpa and the temperature range 55 to 250° C. The irradiations were carried out using 100 keV Al ions. Highpurity Al showed void formation over the whole temperature range investigated with a maximum volume increase V/V of 3.4% at 150° C. The behaviour of the Al-Mg-Si alloys depends strongly upon the thermal pretreatments. The alloy in its homogenized state shows no voids between 55 and 140° C. Trapping of vacancies on solute Si atoms could be the explanation. An ageing treatment leading to coherent precipitates results in the complete suppression of void formation for the temperature region of highest swelling (0.35 T
sT0.44 T
s). On the other hand, treatments which cause incoherent or partially coherent precipitates result in swelling. The amount of swelling, however, is lower compared to pure Al and the temperature of the swell maximum is shifted to lower temperatures. These results could be explained by the mechanism of trapping vacancies by solute atoms, on the one hand, and the coherent precipitates acting as recombination centres, on the other. 相似文献
4.
Utilizing services of legacy and third party COTS components has become vital for the timely development and evolution of software systems. Component interfaces typically have to be adapted before they can be re-used in a system context. This paper presents an approach to generating component adapters. The approach focuses on mapping multiple events, and their associated parameters, generated from a source component to multiple calls in the target component. The novelty of our mechanism is that it allows developers to generate asynchronous as well as synchronous adapters. As a result we can generate adapters for components with incompatible event structure. A prototype called Asynchronous Component Adapter (ACA) was developed which demonstrates the idea with Java Beans, but the methodology can be applied to any component-based system that supports introspection like Microsoft .NET assemblies. 相似文献
5.
A. Letourneau J. Galin F. Goldenbaum B. Lott A. P ghaire M. Enke D. Hilscher U. Jahnke K. Nü nighoff D. Filges R. D. Neef N. Paul H. Schaal G. Sterzenbach A. Tietze 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2000,170(3-4):299-322
Neutron experimental data relevant to the design of the target of neutron spallation sources are presented and discussed. The data include the reaction cross-sections for W, Hg and Pb investigated with 0.4, 0.8, 1.2, 1.8 and 2.5 GeV proton beams as well as the neutron production, neutron multiplicity distribution, as determined event per event using a high-efficiency detector. The production as a function of target material is investigated for both thin (with a single reaction) and thick targets (multiple reactions). Comparisons are made with the predictions of a high-energy transport code. 相似文献
6.
Maike Gleichenhagen Benno F. Zimmermann Birgit Herzig Ingar Janzik Siegfried Jahnke Markus Boner Peter Stehle Rudolf Galensa 《Food chemistry》2013
The intrinsic isotopic labelling of plants with 13CO2 is an effective method to generate highly labelled compounds using photosynthesis and avoiding labour-intensive complex organic syntheses. In this study, the intrinsic isotopic labelling of polyphenols in parsley, spinach and peppermint is shown for the first time. The plants were grown in an atmosphere where 12CO2 was replaced by 13CO2, in order to generate highly labelled compounds. The total content of 13C as well as the individual polyphenols were analysed by Isotopic Ratio-MS and HPLC–Iontrap-MSn. 相似文献
7.
Comparative investigation of the biocompatibility of various silicon nitride ceramic qualities in vitro 总被引:8,自引:0,他引:8
Neumann A Reske T Held M Jahnke K Ragoss C Maier HR 《Journal of materials science. Materials in medicine》2004,15(10):1135-1140
There is a controversy about the biocompatibility of silicon nitride ceramics contained in the literature, which appears to be related to a factor of the individual chemical composition of different qualities of silicon nitride ceramics and of the different surface properties. This study attempts to investigate the cytotoxicity of different qualities of industrial silicon nitride ceramics applying an L929-cell culture model in a direct contact assay combined with a cell viability assessment. Five different qualities of industrial standard silicon nitride ceramics were chosen for in vitro testing. The chemical composition was determined by EDS analysis. Different biomedically approved aluminium oxide qualities, a titanium alloy, glass and polyvinylchloride (PVC) served as control materials. L929 mice fibroblasts were incubated directly on the materials for 24 h, stained with bisbenzimide and propidium iodine for double fluorochromasia viability testing, and evaluated by inversion-fluorescence microscopy to control cell morphology, viability and cell counts compared to empty well values. Scanning electron microscopy was applied to additionally investigate cell morphology. There was no observation of cytotoxic effects on the silicon nitride ceramic samples; moreover cell morphology remained the same as on aluminium oxide and titanium. Viability testing revealed the presence of avital cells exclusively on PVC, which served as a negative control. Cell counts on all polished surfaces showed significantly higher numbers, whereas some rough surface samples showed significantly lower numbers. We conclude that silicon nitride ceramics show no cytotoxic effects and should be considered for biomedical application owing to its favourable physiochemical properties, especially its superior resistance to mechanical stress, which would be useful for compression loaded conditions. Polished surfaces would appear to promote advanced biocompatibility. 相似文献
8.
The Australian rodent, Uromys caudimaculatus, consists of two chromosome races. a) The Southern Race is characterized by the possession of two to twelve B-chromosomes. These vary considerably in size, morphology, and C- and G-banding characteristics, they behave as univalent at meiosis and are inherited in a random manner. b) The Northern Race lacks B-chromosomes, but possesses large blocks of distal C-positive heterochromatin on between 18 and 28 of the 46 chromosomes. The C-blocks may be entirely G-positive entirely G-negative, or G-banded, suggesting heterogeneity with the C-blocks. There is extensive variation both between and within populations of the northern race in the number and size of the distal heterochromatic blocks. There is no apparent difference between the races in chiasma frequency. The northern race does have much higher proportion of interstitial versus distal chiasmata, although it is probable that this is merely a reflection of lack of crossing over in the heterochromatic blocks rather than an actual shift of chiasma localisation within the euchromatin. Despite the extensive differences between the races in the amount and organization of constitutive heterochromatin, hybrids show no abnormalities at meiosis and they are fully fertile. 相似文献
9.
10.
Electrical Percolation Behavior in Silver Nanowire–Polystyrene Composites: Simulation and Experiment
Sadie I. White Rose M. Mutiso Patrick M. Vora David Jahnke Sam Hsu James M. Kikkawa Ju Li John E. Fischer Karen I. Winey 《Advanced functional materials》2010,20(16):2709-2716
The design and preparation of isotropic silver nanowire‐polystyrene composites is described, in which the nanowires have finite L/D (< 35) and narrow L/D distribution. These model composites allow the L/D dependence of the electrical percolation threshold, ?c, to be isolated for finite‐L/D particles. Experimental ?c values decrease with increasing L/D, as predicted qualitatively by analytical percolation models. However, quantitative agreement between experimental data and both soft‐core and core–shell analytical models is not achieved, because both models are strictly accurate only in the infinite‐L/D limit. To address this analytical limitation, a soft‐core simulation method to calculate ?c and network conductivity for cylinders with finite L/D are developed. Our simulated ?c results agree strongly with our experimental data, suggesting i) that the infinite‐aspect‐ratio assumption cannot safely be made for experimental networks of particles with L/D < 35 and ii) in predicting ?c, the soft‐core model makes a less significant assumption than the infinite‐L/D models do. The demonstrated capability of the simulations to predict ?c in the finite‐L/D regime will allow researchers to optimize the electrical properties of polymer nanocomposites of finite‐L/D particles. 相似文献