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661.
Leonardo G. Paterno Fernando J. Fonseca Maria A.G. Soler João P. Sinnecker Emília C.D. Lima Luiz Henrique C. Mattoso 《Thin solid films》2009,517(5):1753-5595
In this study, the layer-by-layer technique is used to deposit nanostructured films exhibiting electrical conductivity and magnetic behavior, from poly(o-ethoxyaniline) (POEA), sulfonated polystyrene (PSS) and positively-charged maghemite nanoparticles. In order to incorporate the nanoparticles into the films, maghemite nanoparticles, in the form of magnetic fluid, were added to POEA solutions, and the resulting suspensions were used for film deposition. UV-Vis spectroscopy and atomic force microscopy images reveal that POEA remains doped in the films, even in the presence of the maghemite nanoparticles, and its typical globular morphology is also present. Electrical measurements show that a POEA/PSS film prepared from POEA solution containing 800 µL of the magnetic fluid exhibits a similar conductivity to that of the control film and, additionally, magnetic measurements indicated that nanosized maghemite phase was incorporated within the polymeric film. 相似文献
662.
Fluxes of nitrous oxide from soil under different crop rotations and tillage systems in the South of Brazil 总被引:3,自引:1,他引:2
Claudia P. Jantalia Henrique P. dos Santos Segundo Urquiaga Robert M. Boddey Bruno J. R. Alves 《Nutrient Cycling in Agroecosystems》2008,82(2):161-173
The zero tillage (ZT) system is used in a large area (>24 Mha) of crop production in Brazil. This management system can contribute
to soil C sequestration, but many studies in other countries have registered greater nitrous oxide emissions under ZT compared
to conventional tillage (CT), which may reduce greenhouse gas mitigation benefits. The aim of this study was to estimate the
emission of N2O from cropping systems under conventional and zero tillage in an 18-year-old experiment conducted on a Rhodic Ferralsol in
the South of Brazil. Fluxes of N2O were measured over two years using static-closed chambers in the two tillage systems with three crop rotations. Soil water
filled pore space (%WFPS) and soil mineral N were monitored along with rainfall and air temperature. Estimates of N2O emissions were obtained by integrating the fluxes with time and also by applying the IPCC direct emission factor (EF1 = 1%)
to the amounts of N added as fertilisers and returned as crop residues. Fluxes of N2O were relatively low, apart from a short period at the beginning of measurements. No relationship between N2O fluxes and %WFPS or mineral N were observed. Nitrous oxide emissions were not influenced either by tillage system or crop
rotation. For the crop rotation receiving high rates of N fertiliser in the second year, field-measured N2O emissions were significantly underestimated by the IPCC emission factor 1 (EF1). For the other treatments measured N2O emissions fell within the EF1 uncertainty range, but always considerably lower than the EF1 estimate, which suggests IPCC
EF1 overestimates true N2O emissions for the Ferralsol under evaluation. 相似文献
663.
Pedro Arias J. Carlos Caamaño Henrique Lorenzo & Julia Armesto 《Computer-Aided Civil and Infrastructure Engineering》2007,22(8):597-611
Abstract: This article deals with the application of low-cost Close Range Digital Photogrammetry to obtain an accurate three-dimensional (3D) re-construction of irregular geometry structures in the field of building construction, with special attention to the evaluation of old structures. Photogrammetry can be used as a non-destructive tool to give precise 3D information about the size and shape of some elements of a structure, quickly and with no risk to the surveyors. The geometric data achieved can be used by engineers and architects to obtain the section properties, and also to estimate the influence of geometric variations in the distribution of stress. This allows us to compare areas subject to higher stress, and could be of special interest regarding some historic and cultural heritage constructions—such as the timber roof structure included as a case study in this work—from two points of view: On the one hand, Photogrammetry makes it possible to obtain precise 3D models of highly irregular elements, as old timber purlines and trusses in the case of ancient constructions; on the other, Photogrammetry is a non-contact method that minimizes the measurement time and allows us to obtain the section properties, which can be used together with some material testing characterization to evaluate the structural safety of the construction. 相似文献
664.
Aurelio Amodei Jr Luís Henrique M. K. Costa Otto Carlos M. B. Duarte 《International Journal of Communication Systems》2008,21(7):695-711
In this paper we propose a new medium access mechanism for HomePNAv2 and HomePNAv3 standards. This mechanism uses a priority aggregation mechanism to avoid collisions, increasing these protocols throughput. Furthermore, this mechanism does not require modifying standards, since it can be implemented over their actual MAC sublayers. Simulation results show that the proposed mechanism is able to increase the throughput up to 44% for HomePNAv2 and 36% for HomePNAv3. Moreover, we also show how this mechanism affects network delay, analyzing average delay and jitter for all protocols presented. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
665.
Leak detection in petroleum pipelines using a fuzzy system 总被引:7,自引:0,他引:7
Henrique V. da Silva Celso K. Morooka Ivan R. Guilherme Tiago C. da Fonseca Jos R.P. Mendes 《Journal of Petroleum Science and Engineering》2005,49(3-4):223
A methodology for pipeline leakage detection using a combination of clustering and classification tools for fault detection is presented here. A fuzzy system is used to classify the running mode and identify the operational and process transients. The relationship between these transients and the mass balance deviation are discussed. This strategy allows for better identification of the leakage because the thresholds are adjusted by the fuzzy system as a function of the running mode and the classified transient level. The fuzzy system is initially off-line trained with a modified data set including simulated leakages. The methodology is applied to a small-scale LPG pipeline monitoring case where portability, robustness and reliability are amongst the most important criteria for the detection system. The results are very encouraging with relatively low levels of false alarms, obtaining increased leakage detection with low computational costs. 相似文献
666.
Adriano G. Fisch Nilo S.M. Cardozo Argimiro R. Secchi Fernanda C. Stedile Cludio Radtke Denise S. De S Zênis N. da Rocha Joo Henrique Z. dos Santos 《Applied Catalysis A: General》2009,370(1-2):114-122
The immobilization of Cp2ZrCl2 was performed by entrapment within the binary oxide SiO2–WO3 using a non-hydrolytic sol–gel route. The catalyst and oxide matrix were characterized by complementary techniques (Rutherford backscattering spectrometry, ultraviolet–visible diffuse reflectance and infrared transmission spectroscopy, differential pulse voltammetry, adsorption–desorption of N2, and X-ray diffraction). The catalyst performance in terms of catalytic activity and polymer properties was evaluated by ethylene polymerization. Catalyst characterization suggested that the entrapped complex exhibited lower Zr electronic density than the corresponding unsupported metallocene. The polymerization results also revealed that this low Zr electronic density is optimized in terms of complex activation with low MAO concentration (low [Al/Zr] ratio) and reactivity. This fine tuning results in a catalyst system that is active with a low [Al/Zr] ratio and that achieves high catalytic activity. The results demonstrate that the entrapping method allows the generation of a catalyst system in which part of the activation process is attributed to the support. In this sense, the support may partially play MAO functions by stabilizing the active catalytic species. 相似文献
667.
Physicochemical,biochemical, microbiological and safety aspects of Pico cheese: Assessment throughout maturation and on the final product
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Sandra P A Câmara Airidas Dapkevicius Henrique J D Rosa Célia C G Silva F Xavier Malcata Maria L N Enes Dapkevicius 《International Journal of Dairy Technology》2017,70(4):542-555
Pico cheese is a traditional variety manufactured on the eponymous Azorean Island (Portugal). In total, 153 cheeses were analysed. The average total solids (TS) content by the end of maturation was 63.3 ± 0.3 g/100 g, Aw 0.943–0.966, salt‐in‐moisture 2.12–4.17 g/100 g and pH 4.89–5.11 ± 0.02. Proteolysis was similar to that of other Iberian raw milk cheeses, but the free fatty acid content was generally higher. Lactococci were the predominant bacteria. Coagulase‐positive staphylococci constituted the most severe hygiene problem. Positive correlations were found between maturation time and TS, titratable acidity, Aw, proteolysis indices and Enterobacteriaceae and coagulase‐positive staphylococcus viable numbers. 相似文献
668.
Amélia Guimarães Carvalho Antonio José Vinha Zanuncio Benedito Rocha Vital Angélica de Cássia Oliveira Carneiro Carlos Miguel Simões da Silva Gustavo Henrique Denzin Tonoli 《Holz als Roh- und Werkstoff》2018,76(1):155-162
The aim of this study was to evaluate the effect of hydrothermal treatment in strand particles of pine used for oriented strand boards (OSB) production. Strand particles of pine were hydrothermally treated at 130, 150 and 170 °C for 7 and 21 min, for the determination of chemical composition, pH, equilibrium moisture content, particles mass loss, and contact angle of these particles with phenol–formaldehyde resin. Afterwards, OSB panels were produced using 8% phenol–formaldehyde resin, with a nominal density of 0.7 g/cm3, and pressing cycle at 170 °C and 3.14 MPa for 8 min. Then, the panels were kept in climate chamber until mass stabilization for the determination of their physical and mechanical properties, and for comparison with the European standards. The hydrothermal treatment in the particles decreased carbohydrate, especially mannan, xylan and arabinans, resulting in reduced equilibrium moisture content, pH, and contact angle, and increasing buffer capacity and mass loss. In OSB panels, treated particles caused the drop in the equilibrium moisture content and reduction of the thickness swelling of the panel, without reducing the mechanical strength, making the hydrothermal treatment very attractive. The hydrothermal treatment at 170 °C for 7 min allowed the resulting OSB panel being classified into the categories 1 and 2 of the European standard, expanding its range of use. 相似文献
669.
670.
Pedro Henrique A. Nóbrega Helcio R.B. Orlande Jean-Luc Battaglia 《International Communications in Heat and Mass Transfer》2011,38(9):1172-1177
In this paper, we apply the Markov Chain Monte Carlo method, within the Bayesian framework, for the estimation of parameters appearing in the heat conduction model in metals under the condition of thermal non-equilibrium between electrons and lattice. Such non-equilibrium can be experimentally observed in a time scale of up to few picoseconds, during the heating of thin metal films with laser pulses of the order of femtoseconds. Simulated measurements containing random errors are used for the solution of the inverse problem. Results are presented for the simultaneous estimation of the electron–phonon coupling factor, the thermal conductivity and the heat capacity of the electron gas. 相似文献