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We propose a new hypothesis that explains the maintenance and evolution of MHC polymorphism. It is based on two phenomena: the constitution of the repertoire of naive T lymphocytes and the evolution of the pathogen and its impact on the immune memory of T lymphocytes. Concerning the latter, pathogen evolution will have a different impact on reinfection depending on the MHC allomorph. If a mutation occurs in a given region, in the case of MHC allotypes, which do not recognize the peptide in this region, the mutation will have no impact on the memory repertoire. In the case where the MHC allomorph binds to the ancestral peptides and not to the mutated peptide, that individual will have a higher chance of being reinfected. This difference in fitness will lead to a variation of the allele frequency in the next generation. Data from the SARS-CoV-2 pandemic already support a significant part of this hypothesis and following up on these data may enable it to be confirmed. This hypothesis could explain why some individuals after vaccination respond less well than others to variants and leads to predict the probability of reinfection after a first infection depending upon the variant and the HLA allomorph. 相似文献
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《Food Control》2017
Ready-to-eat (RTE) foods are not further treated before consumption in such a way that may significantly reduce the microbial load, therefore the risk of foodborne disease must be considered. In this regard, the use of natural antimicrobial compounds is an interesting method to be considered. On this topic, the antibacterial activity of cranberry juice concentrate (CJC) have been evaluated in vitro and in situ against 3 foodborne pathogenic bacteria. Results showed a high antimicrobial effect with a noticeable inhibition capacity against Escherichia coli O157:H7, Listeria monocytogenes, Salmonella typhimurium. Acid sensitivity studies of bacteria indicated that at the same pH level (pH = 2.4) in presence of organic acid solution (citric and quinic acids), cranberry juice concentrate showed greater antibacterial effects than the acids due to their phenolic compounds. In situ studies showed 2.5, 1.8 and 5 log reduction of E. coli, L. monocytogenes and S. typhimurium, respectively in presence of cranberry juice concentrate, on pre-cut red peppers after 7 days of storage at 4 °C. A total inhibition of L. monocytogenes on fresh cranberry fruits in primary day of storage, was observed. Cranberries treated with CJC also showed a 3 log reduction of S. typhimurium after 4 days of storage at 4 °C. The results suggest that CJC can be an effective preservation, source of natural antibacterial, to protect the RTE foods from foodborne pathogens contamination without effecting on sensorial properties of treated samples and allow to maintain the freshness, sensory and the nutritional quality of RTE foods. 相似文献
96.
Kyle S. Landry Andrea Vu Robert E. Levin 《International journal of molecular sciences》2014,15(1):1300-1314
The ability to induce an extracellular DNase from a novel thermophilic fungus was studied and the DNAse purified using both traditional and innovative purification techniques. The isolate produced sterile hyphae under all attempted growing conditions, with an average diameter of 2 μm and was found to have an optimal temperature of 45 °C and a maximum of 65 °C. Sequencing of the internal transcribed region resulted in a 91% match with Chaetomium sp., suggesting a new species, but further clarification on this point is needed. The optimal temperature for DNase production was found to be 55 °C and was induced by the presence of DNA and/or deoxyribose. Static growth of the organism resulted in significantly higher DNase production than agitated growth. The DNase was purified 145-fold using a novel affinity membrane purification system with 25% of the initial enzyme activity remaining. Electrophoresis of the purified enzyme resulted in a single protein band, indicating DNase homogeneity. 相似文献
97.
A rapid simple and economical method was described for the determination of ochratoxin A produced by Aspergillusochraceus ITEM 5117 grown in a biofermenter in submerged culture. The ochratoxin A was determinate with RP-HPLC-FLD (reverse phase high performance liquid chromatography) with direct injection in the HPLC apparatus using a C18 column. The mycotoxin was completely resolved by using the mixture acetonitrile, water and acetic acid (49:49:2 v/v) as the mobile phase with a flow rate of 1.0 mL/min. Mean recoveries of ochratoxin A ranged from 95.36% to 103.15%. The limit of detection for ochratoxin A in medium was found to be 1 μg L−1. 相似文献
98.
The use of eco-freindly polymers as antimicrobial materials is in growth due to the need to reduce the negative impact of conventional treatments on the environment and the human health. The purpose of the present study was to assess the antifungal properties of films and solutions based on chitosan with different molecular weight at different concentrations. Surfactants were added to the formulation to assess their impact on treatment efficiency. The antifungal activity was conducted against tree fungi, Aspergillus niger, Alternaria alternata and Rhizopus oryzae. Results indicated important and significant differences of the antifungal activity between chitosan based solutions and chitosan based films. Furthermore, the antifungal activity of the different treatment depended on the type of fungus treated. Thus, chitosan film treatments were significantly more effective on A. niger than solution treatments. On the other hand, solution treatments resulted in higher radial inhibition when applied against A. alternata or R. oryzae. The highest radial inhibition was observed against A. alternata (97%) using a chitosan solution. The influence of the other parameters (concentration, molecular weight and surfactant type) on treatment efficiency was not as important and their significance depended on treatment type and fungus nature. 相似文献
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100.
Maria Jonstrup Marika Murto Bo Mattiasson 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2013,88(3):388-394
BACKGROUND: Phanerochaete chrysosporium, Trametes versicolor and Bjerkandera sp BOL13 were compared for decolorization of azo dyes supplied individually or as a mixture. The dye decolorization was also evaluated during continuous treatment under non‐sterile conditions using a lignocellulosic growth substrate. RESULTS: Bjerkandera sp BOL13 showed the highest dye decolorization potential. This fungus was also found to support high decolorization of Remazol Red RR at an initial pH of 4‐6 and when using straw as co‐substrate. The fungus was evaluated for Remazol Red RR decolorization in a continuously fed packed‐bed bioreactor operated under non‐sterile conditions with 3 days of hydraulic retention time. When glucose was supplied as growth‐substrate, decolorization efficiencies of 65‐90% were maintained for 12 days in a bioreactor packed with wooden material. The decolorization efficiency was lower when glucose was not fed to the fungus or when a plastic material was used as packing. Higher manganese peroxidase and laccase activities were also recorded when the wood packing was used. Contamination caused a drop in decolorization efficiency after 17‐19 days operation. CONCLUSIONS: The potential of Bjerkandera sp BOL13 for decolorization of azo dyes under non‐sterile conditions using lignocellulosic growth substrates was demonstrated. Research is needed to reduce contamination under non‐sterile conditions. © 2012 Society of Chemical Industry 相似文献