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51.
The purpose of a cooled moderator on a pulsed neutron source may be to extend to longer wavelengths the neutron slowing down range with its narrow pulse widths, or to enhance the long wavelength intensity. The intensity and pulse length as a function of wavelength are determined by the rate of energy exchange, and by leakage and capture of neutrons. Energy deposition and radiation damage present serious problems, and restrict the choice of moderators. Radiation damage, in particular, may limit the lifetime and stability of the moderator, giving rise to problems of corrosion and, in the case of solid moderators, stored energy release. The advantages of solid ammonia are its high hydrogen atom density, and its thermal neutron absorption cross-section which allows the moderator to act as its own homogeneous poison. On the other hand this impairs its use for cold neutron production in those instances where neutron intensity rather than burst width is important. In such cases solid methane is favourable, though the radiation damage problem for methane at high intensity sources is severe, and liquid hydrogen is indicated. 相似文献
52.
Characteristics of Convective Drying of Pepino Fruit (Solanum muricatum Ait.): Application of Weibull Distribution 总被引:2,自引:0,他引:2
Elsa Uribe Antonio Vega-G��lvez Karina Di Scala Romina Oyanadel Jorge Saavedra Torrico Margarita Miranda 《Food and Bioprocess Technology》2011,4(8):1349-1356
The aim of this research was to study the behaviour of the drying kinetics of pepino fruit (Solanum muricatum Ait.) at five temperatures (50, 60, 70, 80 and 90 °C). In addition, desorption isotherms were determined at 20, 40 and 60 °C
over a water activity range from 0.10 to 0.90. The Guggenheim, Anderson and de Boer model was suitable to depict the desorption
data. A monolayer moisture content from 0.10 to 0.14 g water g−1 d.m. was reported. The equations of Newton, Henderson–Pabis, Modified Page, Wang–Singh, Modified Henderson–Pabis, Logarithmic
as well as standardised Weibull were tested for modelling drying kinetics. Besides, Fick’s second law model was used to calculate
the water diffusion coefficient which increased with temperature from 2.55 to 7.29 × 10−10 m2 s−1, with estimated activation energy of 27.11 kJ mol−1. The goodness of fit of the models was evaluated using sum squared error and chi-square statistical tests. The comparison
of the experimental moisture values with respect to the calculated values showed that the standardised Weibull model presented
the best goodness of fit, showing that this equation is very accurate for simulating drying kinetics for further optimisation
of drying times. 相似文献
53.
Antonio Vega-Gálvez Elsa Uribe Gipsy Tabilo-Munizaga Purificación Garcia-Segovia Karina Di Scala 《LWT》2011,44(2):384-391
The effect of High Hydrostatic Pressure (HHP) and other pretreatments on the drying kinetics, antioxidant activity, firmness and microstructure of Aloe vera gel was investigated during convective drying at 70 °C. The pretreatments analyzed were high hydrostatic pressure, blanching, enzymatic and microwaves. Simulation of drying curves was studied through the application of several mathematical models such as Newton, Henderson and Pabis, Page, Modified Page, Wang and Singh, and Weibull. Among them, the Weibull model provided the best fit for the experimental data. All pretreatments increased the water diffusion coefficient compared to the control sample. Microwaves followed by HHP presented the fastest drying rates. All pretreatments modified the microstructure and hence the texture of the product. HHP and microwaves increased firmness while blanching and enzymatic treatments produced a softer final product. Blanching, microwaves and HHP enhanced A. vera antioxidant activity. However, the HHP pretreated samples showed the highest antioxidant activity compared to the rest. Based on these results, HHP together with convective drying offers the chance of producing dried aloe with high antioxidant attributes. 相似文献
54.
Karina T. Magalhães Giuliano Dragone Gilberto V. de Melo Pereira José M. Oliveira Lucília Domingues José A. Teixeira João B. Almeida e Silva Rosane F. Schwan 《Food chemistry》2011
Cheese whey (CW) and deproteinised cheese whey (DCW) were investigated for their suitability as novel substrates for the production of kefir-like beverages. Lactose consumption, ethanol production, as well as organic acids and volatile compounds formation, were determined during CW and DCW fermentation by kefir grains and compared with values obtained during the production of traditional milk kefir. The results showed that kefir grains were able to utilise lactose from CW and DCW and produce similar amounts of ethanol (7.8–8.3 g/l), lactic acid (5.0 g/l) and acetic acid (0.7 g/l) to those obtained during milk fermentation. In addition, the concentration of higher alcohols (2-methyl-1-butanol, 3-methyl-1-butanol, 1-hexanol, 2-methyl-1-propanol, and 1-propanol), ester (ethyl acetate) and aldehyde (acetaldehyde) in cheese whey-based kefir and milk kefir beverages were also produced in similar amounts. Cheese whey and deproteinised cheese whey may therefore serve as substrates for the production of kefir-like beverages similar to milk kefir. 相似文献
55.
Yissleen Nuñez-Mancilla Mario Perez-Won Antonio Vega-Gálvez Viviana Arias Gipsy Tabilo-Munizaga Vilbett Briones-Labarca Roberto Lemus-Mondaca Karina Di Scala 《Innovative Food Science and Emerging Technologies》2011,12(3):338-343
Simultaneous application of high hydrostatic pressure (200–400 MPa) during osmotic dehydration of strawberries was studied in this investigation. The high hydrostatic pressure treatment improved the diffusion coefficients of water and soluble solids compared to atmospheric pressure operation. Effects of process pressure on diffusion coefficients were achieved through an Arrhenius-type equation. Mathematical modeling of mass transfer was performed applying Newton, Henderson–Pabis, Page and Weibull models. Based on statistical results, the Weibull model gave the best goodness of fit on the experimental data under the studies' operative conditions.Industrial relevance: This article deals with the mathematical modeling of mass transfer during simultaneous high hydrostatic pressure treatment and osmotic dehydration of strawberries. Transfer of water and soluble solids during this combined process were satisfactorily simulated with the Weibull model. Results indicated that application of this innovative technology improved strawberries dehydration rates compared to atmospheric pressure operation resulting in a dried fruit with intermediate moisture content ready to be used as input material of further processes. 相似文献
56.
Guangran Zhang Iva Milisavljevic Karina Grzeszkiewicz Piotr Stachowiak Dariusz Hreniak Yiquan Wu 《Journal of the European Ceramic Society》2021,41(6):3621-3628
Highly transparent X2O3 sesquioxide ceramics were obtained from a solid solution of five different oxides (Lu2O3, Y2O3, Yb2O3, Gd2O3, and Dy2O3), mixed in an equal molar ratio according to the principle of high-entropy. The fabricated (Lu, Y, Yb, Gd, Dy)2O3 ceramics achieved 99.97 % of the relative density and exhibited a high degree of optical transparency with the in-line transmittance of almost 80 % in the visible wavelength range. Emissions of Gd3+ (6PJ → 8S7/2 at 312 nm), Dy3+ (4F9/2 → 6H15/2 at 492 nm and 4F9/2 → 6H13/2 at 572 nm), and Yb3+ (2F5/2 → 2F7/2 at 1031 nm) suggested a potential application of the high-entropy ceramics as multi-wavelength emission phosphor transparent ceramics. High-entropy ceramics also exhibited lower specific heat and thermal conductivity compared to single-element sesquioxide ceramics. This work demonstrated that highly transparent oxide ceramics, with complex chemical compositions and good optical properties, could be obtained using the high-entropy principle. 相似文献
57.
58.
59.
Catarine Massucato Nishijima Flavia Karina Delella Clenilson Martins Rodrigues Daniel Rinaldo Monica Valdyrce dos Anjos Lopes-Ferreira Lucia Regina Machado da Rocha Wagner Vilegas Sergio Luis Felisbino Clélia Akiko Hiruma-Lima 《International journal of molecular sciences》2015,16(6):12454-12466
Inflammation and haemorrhage are the main characteristics of tissue injury in botropic envenomation. Although some studies have shown that anti-venom prevents systemic reactions, it is not efficient in preventing tissue injury at the site of the bite. Therefore, this work was undertaken to investigate the anti-inflammatory effects of the methanolic extract and fractions from D. elliptica and to evaluate the role of matrix metalloproteinases (MMPs) in this process. Effects of the extract and fractions from D. elliptica were evaluated using a carrageenan-induced paw oedema model in rats, and leukocyte rolling was visualized by intravital. The quantification of MMPs activities (MMP-2 and MMP-9) extracted from the dermis of mice treated with extract and fractions alone or incubated with venom was determined by zymographic analyses. Our results show that intraperitoneal (i.p.) injection of fractions significantly reduced paw oedema after the carrageenan challenge. Treatment with the tannins fraction also resulted in considerable inhibition of the rolling of leukocytes and this fraction was able to decrease the activation of MMP-9. These results confirmed the anti-inflammatory activity of the methanolic extract and tannins fraction of D. elliptica and showed that the dermonecrosis properties of B. jararaca venom might be mediated through the inhibition of MMP-9 activity. 相似文献
60.
Jhon Larry Moreno Thierry Tran Borja Cantero-Tubilla Karina López-López Luis Augusto Becerra Lopez Lavalle Dominique Dufour 《International Journal of Food Science & Technology》2021,56(3):1171-1183
The physicochemical and physiological attributes of three contrasting commercial varieties of Musaceae, Dominico Harton (plantain), Guineo (cooking banana) and Gros Michel (dessert banana), were evaluated and statistically analysed during post-harvest ripening. Quality attributes differed markedly among varieties, both in fresh fruits and during ripening. Variety (V) had a significant effect (P < 0.001) on all attributes except total soluble solids (TSS), carotenes and total chlorophyll. Storage time (ST) had a significant effect on all attributes except colour parameter b* and total carotenes. Starch levels decreased significantly (P < 0.001) during ripening, with nearly complete hydrolysis in Gros Michel, followed by Guineo and Dominico Harton. Discriminant analysis showed that central diameter, TSS of the pulp, colour parameter a* and total starch had the highest weight in the differentiation among varieties. These results point out which parameters may help improve current methods for monitoring ripening of bananas, in particular the commercially important varieties in this study. 相似文献