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91.
Alina-Crina Ciubotariu Lidia Benea Magda Lakatos-Varsanyi Viorel Dragan 《Electrochimica acta》2008,53(13):4557-4563
In this paper, the results on the electrochemical impedance spectroscopy and corrosion properties of electrodeposited nanostructured Al2O3-Ni composite coatings are presented. The nanocomposite coatings were obtained by codeposition of alumina nanoparticles (13 nm) with nickel during plating process. The coating thickness was 50 μm on steel support and an average of nano Al2O3 particles inside of coatings at 15 vol.% was present. The structure of the coatings was investigated by scanning electron microscopy (SEM). It has been found that the codeposition of Al2O3 particles with nickel disturbs the nickel coating's regular surface structure. The electrochemical behavior of the coatings in the corrosive solutions was investigated by polarization potentiodynamic and electrochemical impedance spectroscopy methods. As electrochemical test solutions 0.5 M sodium chloride and 0.5 M potassium sulphate were used in a three electrode open cell. The corrosion potential is shifted to more negative values for nanostructured coatings in 0.5 M sodium chloride. The polarization resistance in 0.5 M sodium chloride decreases in 24 h, but after that increases slowly. In 0.5 M potassium sulphate solution the polarization resistance decreases after 2 h and after 30 h of immersion the polarization resistance is higher than that of the beginning value. The corrosion rate calculated by polarization potentiodynamic curves obtained after 30 min from immersion in solution is smaller for nanostructured coatings in 0.5 M potassium sulphate (4.74 μm/year) and a little bit bigger in 0.5 M sodium chloride (5.03 μm/year). 相似文献
92.
The dispersion characteristics of respiratory droplets are important in controlling transmission of airborne diseases indoors.
This study investigates the spatial concentration distribution and temporal evolution of exhaled and sneezed/coughed droplets
within the range of 1.0 − 10.0μm in an office room with three air distribution methods, specifically mixing ventilation (MV),
displacement ventilation (DV), and under-floor air distribution (UFAD). The diffusion, gravitational settling and deposition
mechanism of particulate matter were accounted by using an Eulerian modeling approach with one-way coupling. The simulation
results indicate that exhaled droplets up to 10μm in diameter from normal human respiration are uniformly distributed in MV.
However, they become trapped in the breathing zone by thermal stratifications in DV and UFAD, resulting in a higher droplet
concentration and an increased exposure risk to other room occupants. Sneezed/coughed droplets are more slowly diluted in
DV/UFAD than in MV. Low air speed in the breathing zone in DV/UFAD can lead to prolonged human exposure to droplets in the
breathing zone. 相似文献
93.
Detection of Yersinia spp. in meat products by enrichment culture, immunomagnetic separation and nested PCR 总被引:1,自引:0,他引:1
The prevalence of Yersinia enterocolitica in meat products was assessed by four methods: cold enrichment in trypticase soy broth (A), enrichment in modified Rappaport broth at 25 °C (B), concentration by immunomagnetic separation (C) and yadA nested PCR (D). Furthermore, the pathogenic potentials of the isolates were established by phenotypic and genotypic tests, and their genomic relationships were determined by pulsed-field gel electrophoresis (PFGE). A total of 238 samples were collected at retail level in the city of San Luis, Argentina, during the period 2007–2008. The highest Yersinia prevalence in meat products was observed by method D (92 positive samples), followed by methods A (13 positive samples) and C (5 positive samples); however, no isolation was obtained by method B. Fourteen Y. enterocolitica and 4 Yersinia intermedia strains were recovered by culture. All Y. enterocolitica 2/O:9 strains gave results related to virulence by phenotypic tests and exhibited the genotype virF+myfA+ail+ystA+. Two biotype 1A strains showed a genotype virF−myfA−ail+ystA+ystB+. The 14 Y. enterocolitica strains isolated during this work plus one reference strain were separated into 11 genomic types by PFGE. This genomic heterogeneity of the isolates shows the diversity of Y. enterocolitica strains in our region. It is the first time that IMS was used to search Y. enterocolitica strains from naturally contaminated meat products. 相似文献
94.
The ease with which populations of the budding yeast Saccharomyces cerevisiae can be synchronized using the mating pheromone α-factor has been invaluable for studies of the cell cycle. The α-factor response pathway has also remained an important model to study the molecular mechanism of G-protein coupled receptor signalling. α-Factor is a 13 amino acids long peptide that is readily available by automated peptide synthesis. However, only cells of the a mating type respond to α-factor. Cells of the opposite α mating type respond to a-factor, a farnesylated and C-terminally methylated 12 amino acids peptide. Because of its more difficult chemical synthesis, a-factor is not readily available and consequently the a-factor response is less well understood. Here we describe an improved strategy for producing a-factor, based on solid-phase peptide synthesis, followed by two simple steps in solution that show favourable characteristics and good yield. We demonstrate the successful use of the resulting a-factor to synchronize cell cycle progression of α cells. Notably, the a-factor concentrations required for cell synchronization are an order of magnitude lower than typically used α-factor concentrations. Despite a similar cell cycle response, shmoo formation was less pronounced compared to α-factor-treated a cells. Our protocol makes a-factor widely accessible, extending the ease of cell cycle synchronization to budding yeast cells of both mating types and facilitating the study of a-factor signalling. 相似文献
95.
Stasiak-Ró?ańska Lidia B?a?ejak Stanis?aw 《European Food Research and Technology》2012,235(6):1125-1132
Dihydroxyacetone (1,3-dihydroxy-2-propanone, DHA) is applied in the food and cosmetic industries as well as in pharmacy and medicine. It is produced as a result of incomplete oxidation of glycerol by acetic acid bacteria Gluconobacter oxydans. This reaction is catalyzed by PQQ-dependent membrane-bound glycerol dehydrogenase. The research developed a method of obtaining DHA by oxidation of a 3?% aqueous solution of glycerol (pH 7.5) at a temperature of 23?°C, with the only reaction biocatalyst being an immobilized cell preparation obtained from G. oxydans cells. After 5?days of the process, DHA concentration in the solution accounted for 27.2?g/L and the reaction efficiency for 94?%. After 4?days of the reaction run in culture media with pH 5.0, at a temperature of 28?°C, free or immobilized cells of G. oxydans produced on average 25?g of DHA/L at the reaction efficiency of 87?%. 相似文献
96.
Determination of Iron Species in Samples of Iron-Fortified Food 总被引:1,自引:0,他引:1
Przemyslaw Niedzielski Magdalena Zielinska-Dawidziak Lidia Kozak Pawel Kowalewski Barbara Szlachetka Sylwia Zalicka Weronika Wachowiak 《Food Analytical Methods》2014,7(10):2023-2032
The paper presents the determination of iron forms in food products. The procedure of sample extraction was developed and optimized, preserving the content of particular forms of iron. The colorimetric method using 2,2′-bipirydyl (measurements at 520 nm) was applied in Fe(II) determinations, while in Fe(III) determinations, the colorimetric method with potassium thiocyanate (measurements at 470 nm) was applied. The total content of iron was determined by the technique of atomic absorption spectrometry, which allowed for the determination of iron content in organic and inorganic complex compounds. Detection limits of 1 mg kg?1 were obtained for all determined iron forms, with the precision ranging between 0.7 % and 1.5 % for 10 mg kg?1 concentration. The optimized analytical procedure was applied in the determinations of iron forms in iron-fortified food products. 相似文献
97.
98.
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100.
Ian Branford Shevaun Johnson Aspinas Chapwanya Samantha Zayas Filip Boyen Matylda Barbara Mielcarska Lidia Szulc-Dbrowska Patrick Butaye Felix Ngosa Toka 《International journal of molecular sciences》2021,22(13)
Dermatophilus congolensis is a bacterial pathogen mostly of ruminant livestock in the tropics/subtropics and certain temperate climate areas. It causes dermatophilosis, a skin disease that threatens food security by lowering animal productivity and compromising animal health and welfare. Since it is a prevalent infection in ruminants, dermatophilosis warrants more research. There is limited understanding of its pathogenicity, and as such, there is no registered vaccine against D. congolensis. To better understanding the genomics of D. congolensis, the primary aim of this work was to investigate this bacterium using whole-genome sequencing and bioinformatic analysis. D. congolensis is a high GC member of the Actinobacteria and encodes approximately 2527 genes. It has an open pan-genome, contains many potential virulence factors, secondary metabolites and encodes at least 23 housekeeping genes associated with antimicrobial susceptibility mechanisms and some isolates have an acquired antimicrobial resistance gene. Our isolates contain a single CRISPR array Cas type IE with classical 8 Cas genes. Although the isolates originate from the same geographical location there is some genomic diversity among them. In conclusion, we present the first detailed genomic study on D. congolensis, including the first observation of tet(Z), a tetracycline resistance-conferring gene. 相似文献