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排序方式: 共有539条查询结果,搜索用时 0 毫秒
1.
Ellagic acid (2, 3, 7, 8‐tetrahydroxy(1)benzopyrano(5, 4, 3‐cde)(1)benzopyran‐5, 10‐dione) was selected as a model pollutant which is present in the tannic fraction of cork processing wastewater. The ultrafiltration of aqueous ellagic acid solutions through three membranes was studied in tangential UF laboratory equipment. Two of the membranes were polyethersulfone (Biomax10K and Biomax5K, with MWCO of 10000 and 5000 Da, respectively), and the third made of regenerated cellulose (Ultracel5K, with MWCO of 5000 Da). The water hydraulic permeability was evaluated for each membrane. The evolution of the permeate flow rate with processing time was followed, and the influence of the main operating variables (feed flow rate, trans‐membrane pressure and nature of the membranes) on the permeate flux was also established. According to the hypothesis of the film theory, the intrinsic and apparent rejection coefficients, as well as the mass transfer coefficients, were also determined, and the values obtained were discussed as a function of the operating conditions used. 相似文献
2.
Convection promotion within a tubular ceramic membrane by using the kenics static mixer is studied. The experiments were carried out with aqueous solutions of pectin and sodium carboxymethylcellulose (CMC), for Reynolds number in the range of 60-5000. From the results of these experiments it can be concluded that the presence of convection promotor decreasing the concentration of the gel layer. The experimental data are correlated satisfactorily by the equation of the general form Sh=A ReaScb. 相似文献
3.
White-salted cheeses were prepared from ultrafiltered (UF) cows' milk and salted to give final salt-in-moisture (SM) levels of 2.5, 3.2 and 4.0%. The cheeses were stored at 5°C and 10°C for up to 15 weeks. The microflora was dominated by lactic acid bacteria (LAB) but some mould growth was evident within 15 weeks at all SM levels and both temperatures. Levels of water-soluble nitrogen (WSN), attributed to chymosin activity, increased significantly with time, the rate being inversely proportional to the SM level and increasing with storage temperature. Similar effects were noted for trichloroacetic acid-soluble nitrogen (TCA-SN) and free amino acid (FAA) levels, both of which would also be affected by bacterial protease activity. The proteolytic activity was reflected by changes in the hardness and fracturability of the cheeses. 相似文献
4.
This study was carried out to determine the physical, chemical, microbiological and organoleptic properties of koumiss made from bovine milk. The bovine milk was modified according to the composition of mares’ milk using ultrafiltration, microfiltration and nanofiltration. Koumiss made from modified bovine milk and mares’ milk were compared. In order to assess options for a consistent fermentation, a starter culture, instead of the prevailing spontaneous flora in traditional manufacture of koumiss, was used. Key compositional factors modified were the contents of dry matter, mineral, protein and lactose and the casein-to-whey protein ratio. Koumiss made from modified bovine milk and by starter cultures was found to be very similar to koumiss from mares’ milk in terms of pH, titratable acidity, alcohol, proteolytic activity, apparent viscosity, and microbiological composition, when assessed both in the freshly made product and that after 15 days storage at 4°C. 相似文献
5.
In membrane filtration, solution environment factors such as pH and solvent density are important in controlling the filtration
rate and the rejection of the particles and/or the macromolecules. The filtration rate and the rejection in membrane filtration
have been investigated from physicochemical aspects. It was shown that the properties of the filter cake formed on the membrane
surface play a vital role in determining the filtration rate in mem-brane filtration. It was clearly demonstrated that such
filtration behaviors as the filtration rate and the rejection are highly dependent on the electrical nature of the particles
and/or the macromolecules. Furthermore, it was shown that the solvent density ρ has a large effect on the steady filtration
rate in upward ultrafiltration. 相似文献
6.
The objectives of this research are to identify the membrane fouling potential due to different fractions of NOM and correlate
the physicochemical properties of NOM and membranes with the adsorption of humic substances on membrane and investigate the
mechanism of coagulation affecting UF, and find the optimum conditions of the combined of coagulation with UF membrane filtration
for NOM removal. For Nakdong river water, the humic acid fraction was the most reactive precursor fraction for the formation
of the ratio of THMFP/DOC (STHMFP) and TOXFP/DOC (STOXFP). The result of adsorption kinetics tests showed that hydrophobic
organics adsorbed much more quickly than hydrophilic organics on both membranes. Thus, hydrophobic compounds exhibited a preferential
adsorption onto membrane. In case of the effect of membrane properties on the adsorption of organic fractions, the adsorption
ratio (C1/Ce) was greater for the hydrophobic membrane than for the hydrophilic membrane regardless of the kind of organic fractions.
For combined coagulation with membrane process, flux reduction rate showed lower than the UF process alone. Also, the rate
of flux decline for the hydrophobic membrane was considerably greater than for the hydrophilic membrane. Applying the coagulation
process before membrane filtration showed not only reduced membrane fouling, but also improved removal of dissolved organic
materials that might otherwise not be removed by the membrane. That is, during the mixing period, substantial changes in particle
size distribution occurred under rapid and slow mixing conditions due to the simultaneous formation of microflocs and NOM
precipitates. Therefore, combined pretreatment using coagulation (both rapid mixing and slow mixing) improved not only dissolved
organic removal efficiency but also DBP (Disinfection By-Product) precursor's removal efficiency. 相似文献
7.
Water management plays an important role in obtaining high performance from a polymer electrolyte membrane fuel cell (PEMFC).
To reduce the volume and energy consumption of widely-used bubble humidifiers, membrane humidifiers were fabricated by using
an ultrafiltration (UF) membrane and Nafion membranes. The performance of the membrane humidifiers was examined as a function
of gas flow rate and operating temperature. A single cell was operated using the UF membrane humidifiers exhibiting almost
the same performance with that employing bubble humidifiers. 相似文献
8.
Hasan Idrees Ibrahim M. A. ElSherbiny Meagan Hecket Qirong Ke Christian Staaks Ahmed S. G. Khalil Mathias Ulbricht Stefan Panglisch 《化学,工程师,技术》2021,93(9):1408-1416
Reusing wastewater from oil-related industries is becoming increasingly important, especially in water-stressed oil-producing countries. Before oily wastewater can be discharged or reused, it must be properly treated, e.g., by membrane-based processes like ultrafiltration. A major issue of the applied membranes is their high fouling propensity. This paper reports on mitigating fouling inside ready-to-use ultrafiltration hollow-fiber modules used in a polishing step in oil/water separation. For this purpose, in-situ polyzwitterionic hydrogel coating was applied. The membrane performance was tested with oil nano-emulsions using a mini-plant system. The main factors influencing fouling were systematically investigated using statistical design of experiments. 相似文献
9.
从蛋壳中提取溶菌酶的研究 总被引:7,自引:0,他引:7
蛋壳中存在溶菌酶,抽提溶液是抽提此酶的关键,本文通过正交试验,对抽提液的各个因子进行了筛选,确定了较佳的抽提条件,经热变性等电点沉淀法去除杂蛋白,超滤膜浓缩,透析,等电点结晶等方法提取溶菌酶,取得了良好效果,得率0.13%。 相似文献
10.
从多方面考察了碱性有肪酶超滤浓缩液的稳定性,推导出液体碱性脂肪酶失活动力学方程,得到了液体碱脂肪酶的失活级数为1.36级。 相似文献