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The service life of cement-rendered facades is closely related to the environmental conditions to which they are exposed. The probability distribution is determined for the degradation condition of render facades considering different environmental exposures. A sample of 100 render facades was subjected to meticulous fieldwork to determine their condition. The analysis focuses on the environmental factors that most influence the overall degradation of the facades, evaluated through the condition level. Probabilistic models based on Markov chains are developed to predict the evolution of facade deterioration according to exposure to outdoor environmental conditions. The proposed model provides data on the synergy between the degradation agents and the degradation condition of render facades, the average time of permanence in each degradation level, and indications of the effect of degradation on the durability of render that may be applied in the implementation and fine-tuning of maintenance procedures. A better understanding of the durability of render facades allows a more rational management of their maintenance, contributing to a reduction of their life cycle costs. The proposed stochastic model provides information that can be applied in the context of insurance policies, allowing an evaluation of the risk of failure of coatings. 相似文献
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Mayra A. D. Saleh Renato C. F. Neves Paula M. Moraes Paula M. Lima Felipe A. dos Santos Fábio A. Silva Pedro M. Padilha 《Sensing and Instrumentation for Food Quality and Safety》2009,3(2):108-113
This paper proposes a method to determine iron in samples of fish feed and feces using ultrasound in the extraction of the
analyte and in subsequent quantification by flame atomic absorption spectrometry. Using HCl 0.10 mol L−1 as the extraction solution, the optimal conditions of extraction were found to be: granulometry of the sample <60 μm; a sonication
time of five cycles of 10 s and sonication power of 136 W. The method was applied in studies of the availability of iron in
four food sources used in the diet of Nile Tilapia. The results obtained with the proposed extraction method allowed us to
calculate the coefficients of apparent digestibility of iron in the food sources, which was not possible when using results
obtained from samples mineralized by acid digestion. 相似文献
35.
Miguel Correia Nuno Ferreira Neves Lau Cheuk Lung Paulo Veríssimo 《Distributed Computing》2005,17(3):237-249
The application of the tolerance paradigm to security - intrusion tolerance - has been raising a reasonable amount of attention in the dependability and security communities. In this paper we present a novel approach to intrusion tolerance. The idea is to use privileged components - generically designated by wormholes - to support the execution of intrusion-tolerant protocols, often called Byzantine-resilient in the literature.The paper introduces the design of wormhole-aware intrusion-tolerant protocols using a classical distributed systems problem: consensus. The system where the consensus protocol runs is mostly asynchronous and can fail in an arbitrary way, except for the wormhole, which is secure and synchronous. Using the wormhole to execute a few critical steps, the protocol manages to have a low time complexity: in the best case, it runs in two rounds, even if some processes are malicious. The protocol also shows how often theoretical partial synchrony assumptions can be substantiated in practical distributed systems. The paper shows the significance of the TTCB as an engineering paradigm, since the protocol manages to be simple when compared with other protocols in the literature.Published online: 29 October 2004This work was partially supported by the EC, through project IST-1999-11583 (MAFTIA), and by the FCT, through the Large-Scale Informatic Systems Laboratory (LASIGE) and projects POSI/1999/CHS/33996 (DEFEATS) and POSI/CHS/39815/2001 (COPE). 相似文献
36.
W. F. P. Neves‐Junior C. F. de O. Graeff M. Ferreira M. Mulato M. S. Bernardes J. Coutinho‐Netto 《应用聚合物科学杂志》2006,100(1):702-707
The mechanical properties of rubber tubes produced by dip‐coating technique and the influence of the fabrication process on their structural properties were evaluated. Cyclic tension versus deformation tests were performed to investigate the elastic properties of the samples and to understand the changes in rubber tubes behavior under repetitive stress. The effect of the wall thickness on the elastic response of the tubes was also studied. The mechanical properties of opened tubes were also investigated for transversal and longitudinal directions to evaluate the influence of the fabrication process on the alignment of the polymer chains. This investigation indicated that the fabricated tubes are resistant and extremely elastic. They can be elongated up to 800% of its initial length before rupture, and thicker tubes are a bit more resistant to elongation than the thinner ones. In addition, the fabricated tubes have an anisotropic structure due to the fabrication process. Finally, natural rubber tubes may have a great potential to be used as vascular prosthesis, or in other applications that require a large range of resistance and elasticity. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 702–707, 2006 相似文献
37.
Kenneth W. Neves 《Computer Physics Communications》1982,26(3-4):303-310
The principles of vector computation are reviewed including a definition of “depth of parallelism”. The latter concept is related to algorithm performance on various computer architectures (in particular the CRAY-1 and the FPS AP120B). The challenge of providing efficient mathematical software libraries on vector computers and the subsequent trade-offs introduced by vector architecture are discussed. Boeng's multi-level library approach to meet vector computer user's needs is explained. Some timing comparisons for software on the CRAY-1 are also given. 相似文献
38.
do Lago CL da Silva HD Neves CA Brito-Neto JG da Silva JA 《Analytical chemistry》2003,75(15):3853-3858
A new microfabrication process based on a xerographic process is described. A laser printer is used to selectively deposit toner on a polyester film, which is subsequently laminated against another polyester film. The toner layer binds the two polyester films and allows the blank regions to become channels for microfluidics. These software-outlined channels are approximately 6 microm deep. Approximately twice this depth is obtained by laminating two printed films. The resulting devices were not significantly damaged after 24 h of exposure to aqueous solutions of H3PO4, NaOH, methanol, acetonitrile, or sodium dodecyl sulfate. Electric tests with an impedance analyzer and microchannels filled with KCl solution demonstrated that (1) wide channels suffer from deformation of the top and bottom walls due to the lamination of the polyester films and (2) the toner walls are somewhat porous. Although these drawbacks limit the maximum width of a channel and the minimum distance between two channels, the process is an attractive option to other expensive, laborious, and time-consuming methods for microchannels fabrication. The process has been used to implement devices for electrospray tip and capillary electrophoresis with contactless conductivity detection. 相似文献
39.
Francisco Andrade Paulo Novais José Machado José Neves 《Artificial Intelligence and Law》2007,15(4):357-373
The combined use of computers and telecommunications and the latest evolution in the field of Artificial Intelligence brought along new ways of contracting and of expressing will and declarations. The question is, how far we can go in considering computer intelligence and autonomy, how can we legally deal with a new form of electronic behaviour capable of autonomous action? In the field of contracting, through Intelligent Electronic Agents, there is an imperious need of analysing the question of expression of consent, and two main possibilities have been proposed: considering electronic devices as mere machines or tools, or considering electronic devices as legal persons. Another possibility that has been frequently mentioned consists in the application of the rules of agency to electronic transactions. Meanwhile, the question remains: would it possible, under a Civil Law framework, to apply the notions of “legal personhood” and “representation” to electronic agents? It is obvious that existing legal norms are not fit for such an endeavouring challenge. Yet, the virtual world exists and it requires a new but realistic legal approach on software agents, in order to enhance the use of electronic commerce in a global world. 相似文献
40.
The management of financial portfolios or funds constitutes a widely known problematic in financial markets which normally requires a rigorous analysis in order to select the most profitable assets. The presented paper proposes a new approach, based on Intelligent Computation, in particular genetic algorithms, which aims to manage a financial portfolio by using technical analysis indicators (EMA, HMA, ROC, RSI, MACD, TSI, OBV). In order to validate the developed solution an extensive evaluation was performed, comparing the designed strategy against the market itself and several other investment methodologies, such as Buy and Hold and a purely random strategy. The time span (2003–2009) employed to test the approach allowed the performance evaluation under distinct market conditions, culminating with the most recent financial crash. The results are promising since the approach clearly beats the remaining approaches during the recent market crash. 相似文献