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61.
A. A. Castro F. Morales M. Romero A. Conde- Gallardo R. Escamilla 《Journal of Materials Science》2018,53(11):8067-8073
Polycrystalline samples of Gd2?xCo x Ru2O7 with x = 0.0, 0.1 and 0.4 were synthesized by the molten salt method. The samples were studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrical resistivity measurements. Rietveld refinements of the XRD patterns and XPS measurements showed that the Co2+ ion replaces Gd3+ sites. As a result, the lattice parameter a and the Ru–O bond length decrease; then, the Ru–O–Ru bond angle increases. Those changes induce a charge compensation which was detected by XPS measurements. The analysis of these results shows that the Ru 3d5/2 core level could be fitted assuming the contribution of two different chemical states of the Ru. The Ru 3d5/2 core level is localized at 280.7 and 281.6 eV, which corresponds to Ru4+ and Ru5+. The valence band XPS spectra show an increase in Co 3d states at the Fermi level as the Co content increases, which contribute to the decrease in the electrical resistivity. 相似文献
62.
Jan Pospisil Antonio Guerrero Oldrich Zmeskal Martin Weiter Juan Jesus Gallardo Javier Navas Germ Garcia‐Belmonte 《Advanced functional materials》2019,29(32)
Solar cells, light emitting diodes, and X‐ray detectors based on perovskite materials often incorporate gold electrodes, either in direct or indirect contact with the perovskite compound. Chemical interactions between active layers and contacts deteriorate the operation and induce degradation, being the identification of the chemical nature of such interfacial structures an open question. Chemical reactivity of gold in contact with the perovskite semiconductor leads to reversible formation of oxidized gold halide species and explains the generation of halide vacancies in the vicinity of the interface. Electrical biasing induces contact reaction and produces modifications of the current level by favoring the ability of perovskite/Au interfaces to inject electronic carriers. The current injection increment does not depend on the halogen source used, either extrinsically by iodine vapor sublimation of Au electrodes, or intrinsically by bias‐driven migration of bromide ions. In addition, the formation of a dipole‐like structure at the reacted electrode that lowers the potential barrier for electronic carriers is confirmed. These findings highlight adequate selection of the external contacts and suggest the need for a deeper understanding of contact reactivity as it dominates the operation characteristics, rather than being governed by the bulk transport properties of the charge carriers, either electronic or ionic. 相似文献
63.
Gustavo A. Abraham Kemal Kesenci Luca Fambri Claudio Migliaresi Alberto Gallardo Julio San Romn 《大分子材料与工程》2002,287(12):938-945
Poly(methyl methacrylate)‐poly(ε‐caprolactone) (PMMA/PCL) microparticles were synthesized by suspension polymerization of methyl methacrylate in the presence of PCL. The incorporation of a small amount of a macromonomer, methacryloyl‐terminated PCL (M‐PCL), into the reaction mixture, led to the formation of grafted systems, namely PMMA‐g‐PCL/PCL. The synthesis of the macromonomer and its characterization by nuclear magnetic spectroscopy (1H NMR) is described. The role of M‐PCL as an effective compatibilizing agent in the composite was investigated. PMMA/PCL and PMMA‐g‐PCL/PCL composites were fully characterized by 1H NMR, gel permeation chromatography (GPC) and thermal analysis, including thermogravimetric analysis (TGA), conventional differential scanning calorimetry (DSC), modulated DSC (MDSC) and dynamic mechanical thermal analysis (DMTA). Finally, the morphology of the prepared systems was investigated by scanning electron microscopy (SEM). The addition of compatibilizing agent led the formation of a more homogeneous microcomposite with improved mechanical properties.
64.
Jos�� M. Gallardo Sergio Ortega Marc de?la Asunci��n Jos�� Miguel Mantas 《Journal of scientific computing》2011,48(1-3):141-163
We present a new kind of high-order reconstruction operator of polynomial type, which is used in combination with the scheme presented in Castro et al. (J. Sci. Comput. 39:67?C114, 2009) for solving nonconservative hyperbolic systems. The implementation of the scheme is carried out on Graphics Processing Units (GPUs), thus achieving a substantial improvement of the speedup with respect to normal CPUs. As an application, the two-dimensional shallow water equations with geometrical source term due to the bottom slope is considered. 相似文献
65.
Jesús Gallardo Ana I. Molina Crescencio Bravo Miguel A. Redondo César A. Collazos 《Expert systems with applications》2011,38(2):1099-1118
One of the most important aspects of collaborative systems is the concept of awareness, which refers to the perception and knowledge of the group and its activities. Support for the design and automatic development of awareness mechanisms within collaborative systems is hard to find. Furthermore, awareness conceptualizations are usually partial and differ greatly between the proposals of different authors. In response to these problems, we propose an awareness ontology that conceptualizes some of the most important aspects of awareness in a specific kind of system: collaborative systems for carrying out modeling activities. The awareness ontology brings together and extends a series of ontologies we have developed in the past. The ontology is prepared to better meet the specific implementation needs of a model-driven development approach. In order to validate the usefulness of this ontology, we relate its concepts to the awareness dimensions set out in Gutwin and Greenberg’s framework, and we apply the ontology to two systems presently in use. 相似文献
66.
Sobral H. Raineri M. Schinca D. Gallardo M. Duchowicz R. 《Quantum Electronics, IEEE Journal of》1999,35(9):1308-1313
The emission characteristics of an ultraviolet-visible pulsed multi-ionic xenon laser were studied through time-resolved spectroscopy and the results were interpreted using a collisional-radiative theoretical model. This analysis includes more than 20 laser lines belonging to several ionic species (Xe III-VIII). Depending on the experimental conditions, different temporal distributions of the laser lines and their corresponding spontaneous emissions can be observed. In particular, laser emission presents temporal oscillations near threshold. Pumping processes for the laser transitions have been analyzed by using this model. Relativistic Hartree-Fock calculations of laser level lifetimes and radiative transition probabilities were performed. Experimental laser gain for several transitions were obtained and compared with the theoretical values derived from the calculations 相似文献
67.
Gallardo S. Barrero F.J. Martinez-Torres M.R. Toral S.L. Duran M.J. 《Education, IEEE Transactions on》2007,50(2):129-136
This paper proposes and details a course organization methodology based on learner satisfaction achievement. The approach follows the prevailing tendency in modern university reforms which are primarily concerned about "how people learn." As a consequence, the learner has been placed as the main actor of the teaching-learning process. Nevertheless, the current learning literature has not addressed the measurement of learner satisfaction within laboratory and practical subjects. This study develops a general and comprehensive methodology for learner satisfaction measurement in practical subjects. As a case example, the proposed methodology has been applied to an electronic instrumentation and measurement course, confirming the variables with a significant influence on learner satisfaction and becoming the starting point for curriculum redesign based on the learner satisfaction approach. To assess the improvement of the proposed course organization methodology, a comparison with previous academic years has been performed showing the students' rated score evolution. Results fully confirm the validity of the technique and the novel course organization 相似文献
68.
The effect of kraft mill sludge addition (25 to 75 ton/ha) to soil derived from volcanic ashes (Andisol) on wheat (Triticum aestivum L.cv. Puken) biomass production, and in the nutrient absorption by the plants was evaluated. Respiration activity and seed germination tests were carried out on the soil/sludge mixtures, in order to evaluate possible toxic effects due to the sludge addition to the soil. Soil without sludge was used as a control treatment. The plants were grown in a greenhouse (25 degrees C, 14 h-photoperiod) during 120 days, then the plants were collected and dried at 65 degrees C for 72 h for the determination of biomass production (root and aerial) and analyzed for mineral content (Ca, Mg, K and P). The mixtures of soil/sludge showed no toxicity. Seed germination and respiration activity increased with the increment of the sludge. The accumulated CO2 in the soil without sludge was 41.66 mg CO2/100; this value shows a low microbial activity. The biomass increased with the increment of sludge addition to the soil and five times more biomass was obtained when 75 ton/ha sludge was added to the soil. The nutrient absorption efficiency was also improved with the sludge addition. 相似文献
69.
A.M. Chaparro A.J. Martín M.A. Folgado B. Gallardo L. Daza 《International Journal of Hydrogen Energy》2009
Because of the different experimental conditions found in literature for the measurement of the electroactive area of Pt/C electrodes of proton exchange membrane fuel cells (PEMFC) by means of underpotential hydrogen adsorption (HUPD) voltammetry, specially concerning sweep rate and temperature, it was found necessary to perform an analysis of these parameters. With this aim, the electroactive area of PEMFC electrodes has been measured by means of HUPD voltammetry at different sweep rates and temperatures, in liquid electrolyte and solid polymer contact. Both configurations show that HUPD adsorption and desorption charges are strongly dependent on sweep rate voltage and temperature. The most common behaviour observed is a maximum in HUPD desorption charge, typically in the 100–10 mV s−1 sweep rate range, whereas HUPD adsorption charge shows continuous increase with decreasing sweep rate. The decrease of desorption charge at low sweep rates is attributed to adsorbing species related with carbon support reactivity. These processes are also responsible for the increase in desorption HUPD charge at low sweep rate. At high sweep rate, both adsorption and desorption HUPD charges decrease due to limiting diffusion of protons through the microporous electrode. As a consequence, it is found that the closest approximation to the real electroactive area (i.e. the area accessible to protons) corresponds to the maximum in the HUPD desorption charge in the range of 10–100 mV s−1 sweep rate. The influence of measuring temperature is also tested in the range 25 °C–80 °C. A dependence of the adsorption and desorption hydrogen charges is found, due to thermodynamic and kinetics factors. We observe that the processes competing with hydrogen adsorption, i.e. generation and adsorption of carbon species are enhanced with temperature, so a low measuring temperature is found as most appropriate. 相似文献
70.
Nutritional composition and safety of Patagonotothenramsayi, a discard species from Patagonian Shelf
María Jesús González Jose Manuel Gallardo Paul Brickle & Isabel Medina 《International Journal of Food Science & Technology》2007,42(10):1240-1248
Patagonotothen ramsayi, a nototheniid discard species from the southwest Atlantic, was studied to evaluate its composition, quality and suitability for human consumption. The chemical composition of the flesh revealed that P. ramsayi is a valuable food with protein and fat contents ranging between 16–19% and 0.78–1.34%, respectively. It has a high amount of unsaturated fatty acids, especially docosahexaenoic acid (30–42%) and eicosapentaenoic acid (12–18%). It is also a potential source of minerals, with important amounts of magnesium, potassium and phosphorous. The microbial quality of P. ramsayi was good and the detection of toxic metals such as Pb, Cd and Hg revealed that there is no intrinsic risk associated with its consumption. Additionally, no parasites with potential public health implications were found in the flesh. Finally, its flesh is white, with a shellfish odour, and has a firm and elastic texture. The present study shows that P. ramsayi is a nutritious species of high value for human consumption. 相似文献