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91.
We investigated the effect of an elevated ambient temperature on performance in a persistence task. The task involved the coding of incorrect symbols and participants were free to decide how long to spend performing this task. Applying a between-subject design, we tested 125 students in an office-like environment in one of the three temperature conditions. The comfort condition (Predicted Mean Vote [PMV] = 0.01) featured an average air temperature of 24 °C. The elevated ambient temperature condition was 28 °C (PMV = 1.17). Condition three employed an airstream of approximately 0.8 m/s, intended to compensate for performance decrements at the elevated air temperature (28 °C, PMV = 0.13), according to Fanger’s thermal comfort equation. Participants in the warm condition were significantly less persistent compared with participants in the control and compensation conditions. As predicted by the thermal comfort equation, the airstream seemed to compensate for the higher temperature. Participants’ persistence in the compensation and comfort conditions did not differ.
Practitioner Summary: A laboratory experiment involving a simulated office environment and three ambient temperature conditions (24 °C, 28 °C and 28 °C plus airstream) showed that persistence at a task is significantly impaired at 28 °C. An airstream of 0.8 m/s at 28 °C compensated for the disinclination to persist with the task. 相似文献
92.
CO oxidation over structured carriers: A comparison of ceramic foams, honeycombs and beads 总被引:1,自引:0,他引:1
Florina Corina Patcas Gerardo Incera Garrido Bettina Kraushaar-Czarnetzki 《Chemical engineering science》2007,62(15):3984-3990
This work aims an experimental comparison of different packings on the basis of their pressure drop, mass and heat transfer properties. Ceramic foams, beads and a honeycomb monolith were used as carriers in the oxidation of carbon monoxide. The carriers were coated with active Pt/SnO2. The CO oxidation rate was measured in the regime of external diffusion control at superficial gas velocities between 1 and 10 m/s. The volumetric rate coefficients and the pressure drop of packings with similar geometric surface area decreased in the sequence particles > foams > honeycomb. The magnitude of the temperature gradient along the catalytic bed decreased as going from honeycomb over larger particles to foams and small particles. Foams were superior over particle beds from the viewpoint of combined high mass transfer and low-pressure drop. The main advantage of foams as compared to honeycomb resided in the radial mixing enabling a better heat transfer to the reactor walls. 相似文献
93.
Kamal Zellag Bettina Kemme 《The VLDB Journal The International Journal on Very Large Data Bases》2014,23(1):147-172
Modern transaction systems, consisting of an application server tier and a database tier, offer several levels of isolation providing a trade-off between performance and consistency. While it is fairly well known how to identify qualitatively the anomalies that are possible under a certain isolation level, it is much more difficult to detect and quantify such anomalies during run-time of a given application. In this paper, we present a new approach to detect and quantify consistency anomalies for arbitrary multi-tier application running under any isolation levels ensuring at least read committed. In fact, the application can run even under a mixture of isolation levels. Our detection approach can be online or off-line and for each detected anomaly, we identify exactly the transactions and data items involved. Furthermore, we classify the detected anomalies into patterns showing the business methods involved as well as analyzing the types of cycles that occur. Our approach can help designers to either choose an isolation level where the anomalies do not occur or to change the transaction design to avoid the anomalies. Furthermore, we provide an option in which the occurrence of anomalies can be automatically reduced during run-time. To test the effectiveness and efficiency of our approach, we have conducted a set of experiments using a wide range of benchmarks. 相似文献
94.
A competing risks model based on Lomax distributions is considered under progressive Type-II censoring. Maximum likelihood estimates for the distribution parameters are established. Moreover, the expected Fisher information matrix is computed and optimal Fisher information based censoring plans are discussed. In particular, it turns out that the optimal censoring scheme depends on the particular parametrization of the Lomax distributions. 相似文献
95.
Karl‐Heinz Wagner Bettina Isnardy Ibrahim Elmadfa 《European Journal of Lipid Science and Technology》2004,106(1):44-51
The antioxidative effects of γ‐ and mainly δ‐tocopherol in a multiphase system were hardly considered up to now. The aim of this study was i) to assess the effects and ii) to follow the degradation of α‐, γ‐ and δ‐tocopherol in concentrations of 0.01%, 0.05%, 0.1% and 0.25% during the oxidation of a 10% purified rapeseed oil triacylglycerol‐in‐water emulsion at 40 °C in the dark for 15 wk in a system containing a low oxygen concentration. Oxidation experiments were performed weekly by assessing the formation of hydroperoxides and hexanal, and the stability of the tocopherols was determined using high‐performance liquid chromatography. Storage tests were conducted with and without the addition of 0.01% α, α′‐azoisobutyronitrile (AIBN), which is a known radical initiator. α‐Tocopherol increased the formation of hydroperoxides in both tests as well as the generation of hexanal when the radical initiator was added; furthermore it was the least stable. γ‐Tocopherol delayed the formation of hexanal and prolonged the stability of the emulsion in a dose‐dependant manner. δ‐Tocopherol was the most stable and also the most effective in delaying lipid oxidation in the emulsions. Each concentration that was tested reduced the rate of hydroperoxide and especially hexanal formation. Hexanal was only formed to a slight extent after 15 wk of oxidation in the test with AIBN and the lowest dose of 0.01% δ‐tocopherol. For all tocopherols, strong correlations were found between tocopherol stability and the extent of oxidation. Results suggest that i) mainly δ‐tocopherol, but also γ‐tocopherol even less pronounced, are very good antioxidants in order to stabilize and prolong the shelf life of oil‐in‐water emulsions, ii) the antioxidative effects were intensified with increasing amounts. 相似文献
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This paper explores and describes resident’s experiences from a smart grid project that involved 20 households in a rural area in Denmark and ran from 2014 to 2015. The study is based on qualitative data from the participating households, collected 6, 12 and 18 months after the start of the intervention. Drawing on theories of social practice and the three intertwined elements of a practice: competences, images and materials, the paper contributes with an in-depth analysis of a complex intervention, focusing on how the participants changed energy practices as a result of the installed smart grid technologies. Long-term studies on such comprehensive energy interventions and derived changes in domestic energy practices are exceptional. The results show that people relate to their natural environment in new ways and construct new practices according to the movements of the sun; that they gradually become skilled practitioners and prosumers; and that they also increase consumption and develop expectations towards the energy company, requesting better dialogue on energy consumption and control. The paper concludes with reflections and suggestions on how findings may be relevant to policy and research in the area. 相似文献