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71.
Brahim Bchir Mohamed Ali Bouaziz Christophe Blecker Hamadi Attia 《Journal of texture studies》2020,51(3):475-487
This study examines the effects of incorporating fresh, frozen, osmodehydrated, and dried pomegranate seeds, at different concentrations (5, 10, and 20%) on the physicochemical, antioxidant, textural, and sensory properties of yoghurt. Antioxidant activity, pH, acidity, syneresis, and color of yoghurt were also evaluated during the storage (28 days) at 4°C. The principal component analysis (PCA) was performed to assess the correlations between different yoghurt formulation and their sensory attributes. Data showed that the addition of pomegranate seeds reduced pH and modified the chromatics coordinate (L*, a*, b*, C*, h°) and firmness of the yoghurt samples. In addition, acidity, °Brix, and syneresis increased compared to the control. Thanks to their high anthocyanin content, pomegranate seeds considerably improved the antioxidant activity essentially for yoghurt enriched with frozen seeds. In addition, the supplementation of 20% of frozen seeds into yoghurt was the most appreciated by panelists and improved the sensory properties in comparison to other formulation. According to PCA, taste and appearance were the main criteria for the overall acceptability of yoghurt. After 28 days of storage, the reddish color was reinforced; however, the antioxidant activity of yoghurts was reduced. Overall, it can be concluded that pomegranate seeds can be used as a natural ingredient to develop a novel yoghurt with high nutritional properties. 相似文献
72.
73.
In this paper, we report on the effect of chemical vapor etching-based porous silicon (PS) on the performance of multicrystalline silicon solar cells performed via deep n+/p junction-type structures. Chemical vapor etching of silicon leads to the formation of porous silicon (PS) nanostructures that dramatically decrease the surface reflectivity from 30% to about 8%, and increase the minority carrier diffusion lengths from 90 μm to 170 μm. As a result, the short-circuit current density was improved by more than 20% and the fill factor (FF) by about a 10%. An enhancement of the photovoltaic conversion energy efficiency of the solar cells from 7% to 10% was observed. This low-cost PS formation process can be applied in the photovoltaic cell technology as a standard procedure. 相似文献
74.
Alex Bach Isabel Guasch Guillermo Elcoso Julie Duclos Hajer Khelil-Arfa 《Journal of dairy science》2018,101(11):9777-9788
With the objective of evaluating the potential effects of sodium bicarbonate or a magnesium-based product on rumen pH and milk performance of dairy cattle exposed to a dietary challenge, 30 lactating Holstein cows (648 ± 67 kg of body weight; 44.4 ± 9.9 kg/d of milk yield; 155 ± 75 d in milk) were blocked by parity (9 primiparous and 21 multiparous) and randomly distributed to 3 treatment groups. One group received a total mixed ration (TMR) that acted as a control (CTR), a second group (SB) received the same TMR but with an additional supplementation of 0.8% of sodium bicarbonate, and a third group (MG) received the same TMR as CTR but an additional supplementation of 0.4% of a magnesium-based product (pHix-Up, Timab, Dinard, France). After 1 wk of exposure to this TMR, all 3 rations were supplemented with 1 kg/d of barley, which was then increased 1 kg/wk until reaching 3 kg/d of barley during wk 4 of the study. Every kilogram of barley replaced 1 kg of forage in the diet. Individual feed intake and behavior were monitored using electronic feed bins. Seven cows per treatment were equipped with an intraruminal bolus that recorded pH every 15 min. As the severity of the barley challenge increased, dry matter intake decreased, but this decrease was more pronounced in SB cows than in MG cows, with an intermediate response for CTR cows. The MG cows produced more milk when challenged with 2 or 3 kg/d of additional barley than when challenged with 1 kg/d, whereas CTR cows produced less milk with the 3 kg/d challenge compared with 1 or 2 kg/d, and the SB cows maintained milk production. Milk fat content decreased with barley challenges, with CTR cows experiencing a more severe decrease than SB cows, which maintained stable butterfat values throughout the study, and MG cows showed a decline in milk fat content only with the 3 kg/d of additional barley. Meal size was also reduced as the severity of barley challenge increased, and this reduction was more modest in MG cows than in SB cows. The number of daily meals consumed by SB and MG cows was more constant than that recorded in CTR cows. Cows on the CTR and SB treatments showed a marked decrease in rumen pH with the 3 kg/d of additional barley, whereas MG cows maintained stable rumen pH during the barley challenges and had greater average rumen pH (5.93 ± 0.04) than CTR cows (5.83 ± 0.04) with the 3 kg/d of additional barley; SB cows showed intermediate values (5.85 ± 0.04). Last, MG cows spent less time (32.3 ± 6.1%) with rumen pH ≤5.8 when exposed to the 3 kg/d of barley challenge than CTR and SB cows (50.7 ± 5.02%). In conclusion, supplementation with MG prevents the decline in dry matter intake and milk production induced by a rumen challenge, whereas supplementation with SB prevents the decay in milk production but does not prevent the decrease in feed intake. These changes were probably due to the ability of the MG treatment to prevent a reduction in rumen pH when challenging cows with 3 kg/d of additional barley in the ration. 相似文献
75.
76.
The problem of two-dimensional natural convection flow of a dielectric fluid in a square inclined enclosure with a fin placed on the hot wall is investigated numerically. The fin thickness and length are 1/10 and 1/2 of the enclosure side, respectively. The Rayleigh number is varied from 103 to 5 × 105 and the solid to fluid thermal conductivity ratio is fixed at 103. The enclosure tilt or inclination angle is varied from 0° to 90°. The streamlines and isotherms within the enclosure are produced and the heat transfer is calculated. It is found that for 2.5 × 104 ≤ Ra ≤ 2.5 × 105, the average Nusselt number is maximum when γ = 0° and minimum when γ = 90°. For Ra = 5 × 105, the values of enclosure tilt angle for which the average Nusselt number is maximum or minimum are completely different due to the transition to unsteady state. In this case, the maximum heat transfer is obtained for γ = 60°, while the minimum heat transfer is predicted for γ = 0°. Monomial correlations relating the average Nusselt number with the different values of the Rayleigh number from 104 to 105 are determined for two different angles, γ = 0° and γ = 90°. 相似文献
77.
In this article, a numerical study of swirling flows with heat transfer generated by two rotating end disks (co- and counter-rotating) inside a cylindrical enclosure having an aspect ratio equal to 2, filled with a liquid metal, and submitted to a vertical temperature gradient and an axial magnetic field is studied. The governing Navier-Stokes, energy, and potential equations along with appropriate boundary conditions are solved by using the finite-volume method. The flow and temperature fields are presented by stream function and isotherms, respectively. This flow is very unstable and reveals a great richness of structures. In an oscillatory regime, results are presented for various values of the Hartmann number, Ha = 5, 10, 20 and 30, and Richardson numbers, Ri = 0, 0.5, 1, 2 and 4, in order to see their effects on the value of the critical Reynolds number, Recr. Stability diagrams are established according to the numerical results of this investigation. These diagrams show the dependence of Recr with the increase of Ha for various values of Ri. The flow between co-rotating end disks is very different from the flow between counter-rotating end disks. Finally, this study confirms the possibility of stabilization of a liquid metal flow by application of an axial magnetic field. 相似文献
78.
Ammar Mahjoubi Ridha Fethi Mechlouch Belgacem Mahdhaoui Ammar Ben Brahim 《国际可持续能源杂志》2013,32(5):434-448
For estimating the performance of a photovoltaic (PV) water pumping system without battery storage, a simple algorithm has been developed. This simulation program uses the hourly global solar radiation, the hourly ambient temperature and the hourly wind speed as the input, moreover the characteristics of region (latitude, longitude, ground albedo) and characteristics of PV water pumping system (orientation, inclination, nominal PV module efficiency, NOCT, PV array area, PV temperature coefficient, miscellaneous power conditioning losses, miscellaneous PV array losses, temperature of reference, moto-pump efficiency and inverter efficiency). This work allows evaluating the economic interest of a remote PV water pumping systems in the desert of Southern Tunisia, which will have to satisfy an average daily volume of 45 m3 throughout the year compared to another very widespread energy system in the area, the diesel genset (DG), by using the method of the life-cycle cost (LCC). The cost per m3 of water was calculated for this system. It is found that the LCC for PV system is 0.500 TND/m3 and the LCC DG is 0.837 TND/m3. The present study indicates economic viability of PV water pumping systems in the desert of Tunisia. 相似文献
79.
Groundwater interaction in the coastal environment: hydrochemical,electrical and seismic approaches 总被引:1,自引:0,他引:1
Lahcen Zouhri Erick Carlier Brahim Ben Kabbour El Arbi Toto Christian Gorini Barbara Louche 《Bulletin of Engineering Geology and the Environment》2008,67(1):123-128
The heterogeneous Plio-Quaternary coastal aquifer of the Mamora Basin is the most significant reservoir of Morocco. It is
composed of sandstones, conglomerates, limestones and more or less argillaceous sands. The increase in the requirements for
water in this area requires further information on the relations between the geometry of the aquifer and the salinity of the
water. A hydrochemical analysis was undertaken and highlighted three zones of high mineralization. A geophysical approach
allowed the determination of the principal aquifer levels, the localization of the various types of water (fresh, brackish
and salt) and the geometry of the aquifer base. The results obtained by these two approaches provide a better image of the
phenomena governing the groundwater flows and their interactions
相似文献
80.
Hajer Trabelsi Olfa Aicha CherifFaouzi Sakouhi Pierre VilleneuveJustin Renaud Nathalie BarouhSadok Boukhchina Paul Mayer 《Food chemistry》2012,131(2):434-440
This research has determined oil, fatty acid and sterol contents of the Tunisian Pistacialentiscus (Lentisc) fruits during maturation. Low oil accumulation was observed during the first 35 days after the fruiting (DAF) date (from 1.83% to 2.57%). After that, two phases were distinguished (35th until the 60th and 105th to the 145th DAF), where the rate of oil accumulation increased significantly. At the last stage of maturation, the lentisc fruits had the highest percentage of lipid content, 42.54%. The changing profile of fatty acids during maturation had been marked mainly by an increase in oleic acid content (from 19.49% to 50.72%) paralleling a decrease in linoleic acid content (from 42.5% to 21.75%). At the 15th DAF, the alpha-linolenic acid was found with a maximum of 13.81%. At full maturity, the main fatty acids were oleic acid, followed by palmitic and linoleic acid. Other fatty acids were present in trace proportions, such as palmitoleic, stearic, linolenic, gadoleic and arachidic acid. In all stages of ripening only four sterols were identified and quantified. β-Sitosterol was the major 4-desmethylsterol in samples tested, followed by campesterol. Cholesterol and stigmasterol were detected in trace amounts. During the first stage of ripening, the amount of total sterols was about 5.19/100 g of oil. It decreased to 0.43/100 g in the last stage. Sitosterol and campesterol showed nearly the same profile during the ripening of P. lentiscus fruit which could be linked to the relation between these compounds during their biosynthesis. 相似文献