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排序方式: 共有132条查询结果,搜索用时 15 毫秒
1.
The pulp and paper industry has invested heavily over recent years in cleaner processing, to reduce losses and minimise its impact on the environment. Over the past fifteen years, a New Zealand integrated bleached kraft mill has undergone a comprehensive programme of upgrades to increase production, reduce water consumption and streamline its biological treatment process. Whilst the overall discharge of contaminants from the site decreased, the treatment system performance did not show a concurrent improvement as may have been expected. Reduced BOD removal, low dissolved oxygen levels, and poor solids settlability were symptomatic of phosphorus limitation in the aerated lagoon treatment system. The wastewater entering the system was found to be phosphorus limited at a BOD:P ratio of 100:0.2. Mono-ammonium-phosphate was supplemented, at approximately 30 kg P/d, to raise the phosphorus levels to a BOD:P ratio of 100:0.3. Treatment efficiencies improved very quickly after phosphorus dosage, with a 50% reduction in BOD and TSS discharge, a significant increase in dissolved oxygen levels, and improved BOD removal (85% to 93%). This case study demonstrates that whilst more closed operation can result in reduced discharge of organic loads, there may be negative impacts on the availability of nutrients for balanced biological growth. 相似文献
2.
Up to 30% of the released colour arising from bleached kraft pulp and paper production comes from the alkaline extraction stage. This waste stream can therefore be readily targeted to remove colour at source in mills where improved colour management is required. The efficacy of five advanced oxidative treatment and physico-chemical technologies in removing colour from a typical Eop stage effluent was compared. The most effective oxidative treatment was peroxymonosulphate (79% colour removal in 15 minutes). Ozone and TAML treatments removed 74% and 58% of colour respectively within 30 minutes. In comparison, hydrogen peroxide alone was only able to remove 35% of the colour over 4 hours. Coagulation with polyaluminium chloride achieved 89% colour removal within 5 minutes. However, this treatment produced an undesirable sludge, and may cause toxicity in the treated wastewater. Overall, colour removal ability of the five technologies ranked from highest to lowest was polyaluminium chloride > peroxymonosulfate > ozone > TAML > hydrogen peroxide. Other factors, such as operating costs, feedstock modification and capital infrastructure, also need to be taken into account when selecting the most suitable colour management option. 相似文献
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Slade G.W. Carin L. Xu Q. Borchardt S.E. Webb K.J. 《Antennas and Propagation, IEEE Transactions on》1990,38(3):411-414
The results of an experimental investigation of several millimeter-wave slotline leaky-wave antennas at 94 GHz are given. The experimental results show how variations in the transverse slot geometry affect the radiation pattern. Additionally, slot geometry variations also change the polarization performance of the antenna. The narrow transverse slot array was more sensitive to a perpendicularly (E y-E z) polarized electric field than the wide slot case. Also, the change in the effective phase constant along the antenna with changing slot dimensions caused a noticeable shift in the angle of the main beams. However, the beamwidths for all cases remained about the same. A simple model is presented to explain this. For designing an antenna of this form, the effective phase constant, β, can be approximately determined using a numerical analysis of the uniform slot problem. Given β and the operating frequency and the scanning ranges, the element spacing can be determined. The attenuation constant does not change much when the transverse slot widths are varied. If greater sensitivity to an E y-E z polarized wave is desired, the transverse slots should be narrow 相似文献
6.
Alexander M. Slade Christiana B. Honsberg Stuart R. Wenham 《Solar Energy Materials & Solar Cells》2001,66(1-4)
Boron-diffused rear surfaces are used in place of an Al/Si alloy to form a back surface field (BSF) for single-sided buried contact (SSBC) cells. The findings are that a heavy boron diffusion over a large area can retain high bulk lifetime and have a low saturation current. SSBC solar cells that were made had the entire rear heavily boron diffused. These cells had open-circuit voltages of 650, 645, and 640 mV on 3 and 10 Ω cm p-type, and 100 Ω cm (rear junction) n-type, respectively. 相似文献
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Stewart CM Cole MB Legan JD Slade L Vandeven MH Schaffner DW 《Journal of food protection》2001,64(1):51-57
Knowing the precise boundary for growth of Staphylococcus aureus is critical for food safety risk assessment, especially in the formulation of safe, shelf-stable foods with intermediate relative humidity (RH) values. To date, most studies and resulting models have led to the presumption that S. aureus is osmotolerant. However, most studies and resulting models have focused on growth kinetics using NaCl as the humectant. In this study, glycerol was used to investigate the effects of a glass-forming nonionic humectant to avoid specific metabolic aspects of membrane ion transport. The experiments were designed to produce a growth boundary model as a tool for risk assessment. The statistical effects and interactions of RH (84 to 95% adjusted by glycerol), initial pH (4.5 to 7.0 adjusted by HC1), and potassium sorbate (0, 500, or 1,000 ppm) or calcium propionate (0, 500, or 1,000 ppm) on the aerobic growth of a five-strain S. aureus cocktail in brain heart infusion broth were explored. Inoculated broths were distributed into microtiter plates and incubated at 37 degrees C over appropriate saturated salt slurries to maintain RH. Growth was monitored by turbidity during a 24-week period. Toxin production was explored by enterotoxin assay. The 1,280 generated data points were analyzed by SAS LIFEREG procedures, which showed all studied parameters significantly affected the growth responses of S. aureus with interactions between RH and pH. The resulting growth/no growth boundary is presented. 相似文献
9.
Srivatsan Srinivas Marvin Graham M. Heather Brink Slade Gardner Richey M. Davis James E. McGrath Garth L. Wilkes 《Polymer Engineering and Science》1996,36(14):1928-1940
Novel high performance semicrystalline polyimides, based on controlled molecular weight phthalic anhydride (PA) endcapped 1,4-bis(4-aminophenoxy)benzene (TPEQ diamine) and oxydiphthalic dianhydride (ODPA), were synthesized. They exhibited excellent thermal stability in nitrogen and air atmospheres as determined by thermogravimetric analysis (TGA). The glass transition temperatures (Tg) for these polymers ranged from 225°C for the 10,000 Mn (10K) polymer, to 238°C for the 30,000 (30K) Mn material. The observed melting temperatures for all the polymers were ∼420°C. The crystallization behavior of these polymers showed a strong molecular weight dependence, as illustrated by the observation that the 10K and 12.5K polymers crystallized with relative ease, whereas the 15K, 20K, and 30K polymers showed little or no ability to undergo thermal recrystallization. The thermal stability of these polymers above Tm was investigated by studying the effect of time and temperature in the melt on the cold crystallization and melting of these polymers. Increased time and temperature in the melt resulted in lower crystallinity because of melt state degradation, such as crosslinking and branching, as evidenced by an increase in melt viscosity, which was more prominent for the higher molecular weight polymers. 相似文献
10.
Electrolyte powders with low sintering temperature and high-ionic conductivity can considerably facilitate the fabrication and performance of solid oxide fuel cells (SOFCs). Gadolinia-doped ceria (GDC) is a promising electrolyte for developing intermediate- and low-temperature (IT and LT) SOFCs. However, the conventional sintering temperature for GDC is usually above 1200 °C unless additives are used. In this work, a nanocrystalline powder of GDC, (10 mol% Gd dopant, Gd0.1Ce0.9O1.95) with low-sintering temperature has been synthesized using ammonium benzoate as a novel, environmentally friendly and cost-effective precursor/precipitant. The synthesized benzoate powders (termed washed- and non-washed samples) were calcined at a relatively low temperature of 500 °C for 6 h. Physicochemical characteristics were determined using thermal analysis (TG/DTA), Raman spectroscopy, FT-IR, SEM/EDX, XRD, nitrogen absorptiometry, and dilatometry. Dilatometry showed that the newly synthesized GDC samples (washed and non-washed routes) start to shrink at temperatures of 500 and 600 °C (respectively), reaching their maximum sintering rate at 650 and 750 °C. Sintering of pelletized electrolyte substrates at the sintering onset temperature for commercial GDC powder (950 °C) for 6 h, showed densification of washed- and non-washed samples, obtaining 97.48 and 98.43% respectively, relative to theoretical density. The electrochemical impedance spectroscopy (EIS) analysis for the electrolyte pellets sintered at 950 °C showed a total electrical conductivity of 3.83 × 10?2 and 5.90 × 10?2 S cm?1 (under air atmosphere at 750 °C) for washed- and non-washed samples, respectively. This is the first report of a GDC synthesis, where a considerable improvement in sinterability and electrical conductivity of the product GDC is observed at 950 °C without additives addition. 相似文献