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111.
Helga Hornberger Hannah Kissel Birgit Striegl Matthias Kronseder Florian Vollnhals Silke Christiansen 《工业材料与腐蚀》2022,73(1):8-19
In the current research, magnesium and its alloys have been intensively studied as resorbable implant materials. Magnesium materials combine their good mechanical properties with bioactivity, which make them interesting for guided bone regeneration and for the application as barrier membranes. In this study, the in vitro degradation behavior of thin magnesium films was investigated in cell medium and simulated body fluid. Three methods were applied to evaluate corrosion rates: measurements of (i) the gaseous volume evolved during immersion, (ii) volume change after immersion, and (iii) polarization curves. In this comparison, measurements of H2 development in Dulbecco's modified Eagle's medium showed to be the most appropriate method, exhibiting a corrosion rate of 0.5 mm·year?1. Observed oxide and carbon contamination have a high impact on controlled degradation, suggesting that surface treatment of thin foils is necessary. The bioactivity test showed positive results; more detailed tests in this area are of interest. 相似文献
112.
Silke Scheible 《Language Resources and Evaluation》2012,46(4):635-666
Although superlatives are commonly used in natural language, so far there has been no large-scale computational investigation of the types of comparisons they express. This article describes a comprehensive annotation scheme for superlatives, which classifies superlatives according to their surface forms and motivates an initial focus on so-called “ISA superlatives”. This type of superlative comparison is especially suitable for a computational approach because both their targets and comparison sets are explicitly realised in the text, and the proposed annotation scheme offers guidelines for annotating the spans of such comparative elements. The annotations are tested and evaluated on 500 tokens of superlatives with good inter-annotator agreement. In addition to providing a platform for investigating superlatives on a larger scale, this research also introduces a new text-based Wikipedia corpus in which all superlative instances have been annotated according to the proposed annotation scheme, and which has been used to develop a tool that can reliably distinguish between different superlative types, and identify the comparative components of ISA superlatives. 相似文献
113.
Railway crew scheduling deals with generating driver duties for a given train timetable such that all work regulations are met and the resulting schedule has minimal cost. Typical problem instances in the freight railway industry require the generation of duties for thousands of drivers operating tens of thousands of trains per week. Due to short runtime requirements, common solution approaches decompose the optimization problem into smaller subproblems that are solved separately. Several studies have shown that the way of decomposing the problem significantly affects the solution quality. An overall best decomposition strategy for a freight railway crew scheduling problem, though, is not known. In this paper, we present general considerations on when to assign two scheduled train movements to separate subproblems (and when to rather assign them to the same subproblem) and deduct a graph partitioning based decomposition algorithm with several variations. Using a set of real-world problem instances from a major European railway freight carrier, we evaluate our strategy and benchmark the performance of the decomposition algorithm both against a common non-decomposition algorithm and a lower bound on the optimal solution schedule. The test runs show that our decomposition algorithm is capable of producing high-quality solution schedules while significantly cutting runtimes compared to the non-decomposition solution algorithm. We are following a ”greenfield” approach, where no information on previous schedules is needed. Hence, our approach is applicable to any railway crew scheduling setting, including network enlargement, integration of new customers, etc. 相似文献
114.
Dorothea Ehlers Silke Hilmer und Stefan Bartholomae 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1995,200(4):282-288
Zusammenfassung Über Zimthochdruckextrakte, die neuerdings zunehmend im Handel anzutreffen sind, liegen im Gegensatz zu Zimtölen bisher fast keine Literaturangaben vor. Mittels HPLC wurden daher handelsübliche Zimtrinden-CO2-Hochdruckextrakte vonCinnamomum zeylanicum (Ceylon- und Madagaskar-Zimt),C. cassia (Chinesischer Zimt) undC. burmanii (Padang-Zimt) im Vergleich mit Zimtölen untersucht. Dabei zeigte sich, daß die relevanten Inhaltsstoffe abhängig von der Zimtart einerseits und der Probenart andererseits in unterschiedlichen, charakteristischen Konzentrationen vorlagen, wobei sich nicht nur Öle und Hochdruckextrakte, sondern auch sog. Selektivextrakte (40°C/90 bar) und Totalextrakte (40°C/ 280–300 bar) deutlich voneinander unterschieden.
HPLC analysis of supercritical CO2 cinnamon and cassia extracts in comparison with cinnamon and cassia oils
Nowadays supercritical CO2 extracts of cinnamon and cassia are coming more and more in trade. Contrary to cinnamon and cassia oils there are very few references in literature about these. Commercially available supercritical CO2 extracts of cinnamon and cassia barks (cinnamon type Ceylon and type Madagascar, cassia type China and type Indonesia) were analysed by HPLC and compared with cinnamon and cassia oils. The results of the analysis showed that the main compounds evidently differed depending on the species of cinnamon (Cinnamomum zeylanicum, C. cassia andC. burmanii) and on the kind of sample, whereby there was a great difference not only between oils and CO2 extracts, but also between so-called selective extracts (40°C/90 bar) and total extracts (40°/280–300 bar).相似文献
115.
Dirk?W?LachenmeierEmail author Willi?Frank Eberhard?Humpfer Hartmut?Sch?fer Silke?Keller Monika?M?rtter Manfred?Spraul 《European Food Research and Technology》2005,220(2):215-221
High-resolution nuclear magnetic resonance (NMR) spectroscopy is introduced for the quality control and authenticity assessment of beer in official food control. Measurements were performed using a 400-MHz NMR spectrometer using flow injection technology for automatic sample changing. Only degassing and addition of buffer (pH 5.6 in D2O for locking and 0.1% TSP for referencing) is required to prepare the beer samples. Differences in the spectral profiles of beers varying in type and origin were studied by principal component analysis (PCA), considering the spectrum to be a characteristic fingerprint. For the first time, the high throughput of a Flow-Injection NMR system allowed a comprehensive database of beer spectra for PCA classification to be established efficiently. Beers made with barley malt could be distinguished from those made with wheat malt. Clustering of beers from the same brewing sites was observed, as well as significant discrimination of beers with deteriorated quality. Using the partial least squares (PLS) method to correlate NMR spectra with results from reference methods, models for calculating the original gravity, ethanol and lactic acid were established. The results obtained suggest that NMR is a useful tool in the quality control of beer samples, since quantitative determination of essential compounds as well as chemometric classification are simultaneously possible. Compared to conventional methods, 1H NMR spectroscopy is faster and requires simpler sample preparation. 相似文献
116.
The electrochemistry of 50 μm diameter Pt electrodes used for neural stimulation was studied in vitro by reciprocal derivative chronopotentiometry. This differential method provides well-defined electrochemical signatures of the various polarization phenomena that occur at Pt microelectrodes and are generally obscured in voltage transients. In combination with a novel in situ coulometric approach, irreversible H(2) and O(2) evolution, Pt dissolution and reduction of dissolved O(2) were detected. Measurements were performed with biphasic, charge-balanced, cathodic-first and anodic-first current pulses at charge densities ranging from 0.07 to 1.41 mC/cm(2) (real surface area) in phosphate buffered saline (PBS) with and without bovine serum albumin (BSA). The extent to which O(2) reduction occurs under the different stimulation conditions was compared in O(2)-saturated and deoxygenated PBS. Adsorption of BSA inhibited Pt dissolution as well as Pt oxidation and oxide reduction by blocking reactive sites on the electrode surface. This inhibitory effect promoted the onset of irreversible H(2) and O(2) evolution, which occurred at lower charge densities than those in PBS. Reduction of dissolved O(2) on Pt electrodes accounted for 19-34% of the total injected charge in O(2)-saturated PBS, while a contribution of 0.4-12% was estimated for in vivo stimulation. These result may prove important for the interpretation of histological damage induced by neural stimulation and therefore help define safer operational limits. 相似文献
117.
Dr. Bernhard Wagner Thomas Walter Dr. Thomas Himmelsbach Patrick Clos Antje Beer Dr. D?rte Budziak Dr. Thomas Dreher Dr. Hans-Gerhard Fritsche Mathias H��bschmann Dr. Silke Marczinek Annett Peters Heidrun Poeser Hannsj?rg Schuster Dr. Anke Steinel Frank Wagner Dr. Gunther Wirsing 《Grundwasser》2011,16(3):155-162
One of the main objectives of the EC water framework directive is to ensure good chemical status for all groundwater bodies. For this reason the geological surveys of Germany have produced a nationwide map of the background values of groundwater. Only naturally occurring inorganic parameters were taken into account, including the relevant major and trace elements. Based on the hydrogeological map of Germany at the scale of 1:200,000 (HüK 200), and its delimited hydrogeological regions, a total of 186 hydrogeochemical units were defined and mapped geochemically. This involved collection of more than 52,000 groundwater samples in a database and allocation to their appropriate hydrogeochemical units. In order to separate anomalies within the data-sets from the underlying normal population, probability nets were used as a statistical tool. The procedure allowed to determine the normal populations of the investigated parameters within the hydrogeochemical units and to quantify them in the form of percentiles. The resulting hydrogeochemical background values are accessible through an internet web map service that includes an online map application. The main intention of this technical note is to inform the reader about the existing internet service, which necessitates some web-site content duplication. 相似文献
118.
Borschel C Spindler S Lerose D Bochmann A Christiansen SH Nietzsche S Oertel M Ronning C 《Nanotechnology》2011,22(18):185307
Ion beams can be used to permanently bend and re-align nanowires after growth. We have irradiated ZnO nanowires with energetic ions, achieving bending and alignment in different directions. Not only the bending of single nanowires is studied in detail, but also the simultaneous alignment of large ensembles of ZnO nanowires. Computer simulations reveal how the bending is initiated by ion beam induced damage. Detailed structural characterization identifies dislocations to relax stresses and make the bending and alignment permanent, even surviving annealing procedures. 相似文献
119.
120.
Remote Trap Passivation in Colloidal Quantum Dot Bulk Nano‐heterojunctions and Its Effect in Solution‐Processed Solar Cells
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