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91.
Partial characterization of polyphenoloxidase from a hybridized wheat (Triticum aestivum L.) 总被引:1,自引:0,他引:1
Mustafa Erat Yaşar Nuri Şahin Gülşah Aksoy Ahmet Demirkol 《European Food Research and Technology》2010,231(6):899-905
Polyphenol oxidase was extracted and partially purified from wheat leaves by a procedure that included ammonium sulfate fractionation
followed by dialysis and gel filtration chromatography. These procedures led to 35.21-fold purification with 17.65% recovery.
Optimum pH, temperature, and ionic strength were determined with six substrates. Some kinetic properties of the enzyme such
as V
max,
K
M, and k
cat were calculated for the substrates. The k
cat/K
M values of the PPO for catechol, catechin, pyrogallol, l-dopa, dopamine, and 4-methyl catechol were 31408, 31167, 28404, 15378, 4865, and 4967 mM/min, respectively. The best substrate
of wheat PPO was found to be catechol. The native molecular weight of the PPO was estimated to be 243 kDa based on its mobility
in gel filtration column. The inhibitory effects of glutathione, sodium azide, ascorbic acid, oxalic acid, l-cysteine, and thiourea on the reaction catalyzed by the enzyme were tested, and I
50 values were estimated to be 8.0 mM, 10.12 mM, 11.18 mM, 77.33 mM, 183 mM, and 413 mM, and K
i constants were also calculated as 0.416 ± 0.244 mM, 0.317 ± 0.208 mM, 0.820 ± 0.111 mM, 13.80 ± 1.179 mM, 14.10 ± 5.069 mM,
and 130 ± 62.45 mM, respectively, by means of Lineweaver–Burk graphs. The most effective inhibitor was glutathione. Glutathione,
sodium azide, oxalic acid, and thiourea were competitive inhibitors, whereas ascorbic acid and l-cysteine were also noncompetitive inhibitors. 相似文献
92.
The incidence of Salmonella spp., Listeria monocytogenes and Escherichia coli O157:H7 was determined in 100 Turkish sausage (soudjouck) samples collected from shops and markets in the Afyon province, Turkey. Salmonella spp. were detected in 7% of the samples. All of the isolates were S. enterica Paratyphi B. In addition, Listeria spp. were detected in 9% of the samples. Its distribution was 7% L. monocytogenes and 1% each of L. ivanovii and L. innocua. Serological study of the seven L. monocytogenes isolates showed that three of these were 1/2 ab, three were 5/6 ab and one was 1 ab. E. coli O157:H7 was not detected in any of the samples. The pH values of the samples ranged from 4.8 to 6.5. In conclusion, increasing number of listeriosis and salmonellosis cases in Turkey and the contamination levels found indicate that risk assessment and improved preventive measures are required for these sausages. 相似文献
93.
Treatability of paint manufacturing wastewater (PMW) by electrocoagulation (EC) process was investigated. Effects of operating parameters for the EC process such as electrode type (Al or Fe), initial pH (2–10), current density (5–80 A/m2) and operating time (0–50 min) were evaluated for optimum operating conditions. The highest removal efficiencies for COD and TOC in PMW were obtained with 93% and 88% for Fe and 94% and 89% for Al electrodes at the optimum conditions (35 A/m2, 15 min and pH 6.95). Operating costs for removal of PMW at the optimum conditions were calculated for Fe and Al electrodes as 0.187 €/m3 and 0.129 €/m3. Toxicity test was carried out to obtain information about toxic effect of the raw and treated wastewaters at optimum operating conditions. The samples measured by respirometric method contained hardly toxicities. Performance of Al electrode was better than that of Fe electrode in terms of removal efficiency and operating cost. 相似文献
94.
95.
Thermal conductivities of three different edible oils, namely sunflower oil, corn oil and olive oil, were measured at temperatures 25, 40, 60, and 80°C. The measurements were carried out using a hot wire probe method. The calibration of the probe was performed using 0.3% agar gel with water and glycerin. In general, thermal conductivities of oils used in this study are found to be decreasing with temperature. The values of thermal conductivity measured are quite near to each other, the highest and the lowest being respectively 0.168 W/m K for sunflower oil at 25°C and 0.152 W/m K for corn oil at 80°C. 相似文献
96.
Nihal Türk Hakan Gündoğmuş Mustafa Akyol Z. Deniz Yakıncı Ahmet Ekicibil Bekir Özçelik 《Journal of Superconductivity and Novel Magnetism》2014,27(3):711-716
The superconducting Bi1.6Pb0.4Sr2Ca2Cu3?x W x O10+y (x=0.00, 0.05, 0.10, 0.15) bulk samples were prepared by the solid-state reaction method. The effects of W substitution on the BSCCO system have been investigated by the electrical resistivity (ρ-T), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), magnetic hysteresis and critical current density measurements. It has been found that the Bi-(2212) low-T C phase is formed for all the substitution levels, together with the Bi-(2223) high-T C phase. The results obtained from the XRD data show that the Bi-(2223) phase gradually transforms into the Bi-(2212) phase with increasing W substituting for Cu. In addition, from the magnetization measurements at the temperatures below the zero resistance temperatures of the samples, we have observed that a decreasing in magnitude of |M| with the increasing measurement temperature and W concentration. Therefore, the decreasing of |M| related to superconducting volume seems to imply an existence of flux-pinning centers in our samples. 相似文献
97.
Streptococcus thermophilus is a commonly used starter bacterium in dairy industry. It reduces the pH of milk rapidly and equilibrates the medium for the growth of Lactobacillus delbrueckii subsp. bulgaricus during yoghurt fermentation. Efforts to increase the diversity of artisanal yoghurt starters are not only important to bring new strains with novel and desirable characteristics, but also for the preservation of natural diversity which diminishes with the overuse and spread of industrial starters to natural resources. In the present study, 14 artisanal yoghurt samples were processed for the isolation of promising strains for yoghurt starter culture production and 66 strains were subsequently characterized. They were all identified as S. thermophilus using species-specific PCR and 16S rRNA gene sequencing. Genotypic diversity at the strain level was investigated by pulsed field gel electrophoresis (PFGE), and 22 homology groups were obtained. Further phenotypic characterization unearthed a significant phenotypic heterogeneity within homology groups, mostly with atypical novel character. Only 7 out of 66 strains showed S. thermophilus type-strain like phenotypic traits. Majority of the isolates were determined to be protease positive and fast milk acidifier to be used as yoghurt starter culture. 相似文献
98.
Pinar Sarisaray Boluk Sebnem Baydere A. Emre Harmanci 《Mobile Networks and Applications》2011,16(2):149-170
Robust image and video communications have become more imperative due to the ubiquitous proliferation of multimedia applications
over wireless sensor networks. In this work, the transmission distortions on the image data induced by both channel and instant
node failures for Wireless Sensor Networks (WSN) are considered. The effect of two techniques and their integration with multipath
transmission are investigated to compensate the multimedia distortions at the expense of incurring additional energy consumption
and/or wasting bandwidth resources. First technique is watermarking based error concealment utilizing discrete wavelet transform
for embedding downsized replicas of original image into itself. The other is conventional Reed–Solomon (RS) coding utilizing
additional information bits to correct bit/symbol errors. Performance results obtained from extensive simulations utilizing
a communication and energy model applicable to WSN show that error concealment (EC) integrated schemes, especially EC with
multipath fusion (ECMF), are more promising to compensate losses than RS-coding-integrated and pure multipath transmission
techniques in WSN. 相似文献
99.
Berna Kilinc Sukran Cakli Sebnem Tolasa Tolga Dincer 《European Food Research and Technology》2006,222(5-6):604-613
The production of sardine fermented fish sauce was replicated in the laboratory in order to study the chemical, microbiological
and sensory changes associated with the process. Fish sauce were produced by incubating mixtures of sardine (Sardina pilchardus) at different concentrations of sodium chloride and glucose at 37 °C for 57 days. Changes in chemical composition (moisture,
protein, fat contents), pH, total volatile basic nitrogen (TVB-N, mg N/100 g fish flesh), trimethylamine (TMA-N, mg/100 g
fish flesh), thiobarbituric acid (TBA, mg malonaldehyde/kg fish flesh), water activity (aw), color measurement, total viable
count, lactic acid bacteria count, yeast and moulds counts and sensory analyses were observed. The fish sauces with spices
were determined lower bacteria counts than fish sauces without spices. The addition of glucose to the fish sauces caused a
significant increasing in the bacterial counts. Staphylococcus aureus and yeast-mould counts were not detected during fermentation period. The use of spices in fermentation of sardine enhanced
good color, aroma and taste. 相似文献
100.
A single ferrite/dielectric image line is analyzed using the effective permittivity method adapted for ferrites. E/sub pq//sup x/ modes are used in association with a transverse bias direction to obtain nonreciprocal behavior. It is shown that the required conditions can be obtained that enable the composite image line to guide in one direction and leak in the other. Thus, the structure behaves as a "leaky-wave isolator." Dispersion diagrams showing this behavior in the frequency range of 14-30 GHz are obtained for a 2 /spl times/ 2 mm/sup 2/ ferrite (type TT1-390) rod with adjacent dielectric loading with /spl epsiv/r=10. The structure is built and the bias is applied externally in a direction transverse to and in the plane of the direction of propagation. The required modes are excited and probed by semirigid coaxial cables mounted on vernier mechanisms. The S-parameters indicating the nonreciprocal behavior in the frequency range expected are shown. 相似文献