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301.
Graham MC Oliver IW MacKenzie AB Ellam RM Farmer JG 《The Science of the total environment》2011,409(10):1854-1866
Uranium associations with colloidal and truly dissolved soil porewater components from two Ministry of Defence Firing Ranges in the UK were investigated. Porewater samples from 2-cm depth intervals for three soil cores from each of the Dundrennan and Eskmeals ranges were fractionated using centrifugal ultrafiltration (UF) and gel electrophoresis (GE). Soil porewaters from a transect running downslope from the Dundrennan firing area towards a stream (Dunrod Burn) were examined similarly. Uranium concentrations and isotopic composition were determined using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) and Multi-Collector-Inductively Coupled Plasma-Mass Spectrometry (MC-ICP-MS), respectively.The soils at Dundrennan were Fe- and Al-rich clay-loam soils whilst at Eskmeals, they were Fe- and Al-poor sandy soils; both, however, had similar organic matter contents due to the presence of a near-surface peaty layer at Eskmeals. These compositional features influenced the porewater composition and indeed the associations of U (and DU). In general, at Dundrennan, U was split between large (100 kDa-0.2 μm) and small (3-30 kDa) organic colloids whilst at Eskmeals, U was mainly in the small colloidal and truly dissolved fractions. Especially below 10 cm depth, association with large Fe/Al/organic colloids was considered to be a precursor to the removal of U from the Dundrennan porewaters to the solid phase. In contrast, the association of U with small organic colloids was largely responsible for inhibiting attenuation in the Eskmeals soils.Lateral migration of U (and DU) through near-surface Dundrennan soils will involve both large and small colloids but, at depth, transport of the smaller amounts of U remaining in the porewaters may involve large colloids only. For one of the Dundrennan cores the importance of redox-related processes for the re-mobilisation of DU was also indicated as MnIV reduction resulted in the release of both MnII and UVI into the truly dissolved phase. 相似文献
302.
MacKinnon G MacKenzie AB Cook GT Pulford ID Duncan HJ Scott EM 《The Science of the total environment》2011,409(23):5010-5019
Results are presented for a study of spatial distributions and temporal trends in concentrations of lead (Pb) from different sources in soil and vegetation of an arable farm in central Scotland in the decade since the use of leaded petrol was terminated. Isotopic analyses revealed that in all of the samples analysed, the Pb conformed to a binary mixture of petrol Pb and Pb from industrial or indigenous geological sources and that locally enhanced levels of petrol Pb were restricted to within 10 m of a motorway and 3 m of a minor road. Overall, the dominant source of Pb was historical emissions from nearby industrial areas. There was no discernible change in concentration or isotopic composition of Pb in surface soil or vegetation over the decade since the ban on the sale of leaded petrol. There was an order of magnitude decrease in Pb concentrations in road dust over the study period, but petrol Pb persisted at up to 43% of the total Pb concentration in 2010. Similar concentrations and spatial distributions of petrol Pb and non petrol Pb in vegetation in both 2001 and 2010, with enhanced concentrations near roads, suggested that redistribution of previously deposited material has operated continuously over that period, maintaining a transfer pathway of Pb into the biosphere. The results for vegetation and soil transects near minor roads provided evidence of a non petrol Pb source associated with roads/traffic, but surface soil samples from the vicinity of a motorway failed to show evidence of such a source. 相似文献
303.
R. L. Judd H. S. MacKenzie M. A. Elbestawi 《The International Journal of Advanced Manufacturing Technology》1995,10(6):357-366
A novel proposal is presented in this paper for reducing the thermal inaccuracy of turning on a lathe by removing the portion of the heat generated during the cutting process which is transferred to the carbide cutting insert by installing a heat pipe in the toolholder. The ability of the heat pipe to affect the temperature of the carbide cutting insert and the elongation of the toolholder is inferred from the response of thermocouples and strain gauges mounted on the toolholder to the heat generated during various cutting conditions. The results of the experimental investigation have proved the feasibility of the concept and recommendations have been made for continuing the research and improving the performance of the system. 相似文献
304.
W. M. MacKenzie 《Journal of the Institute of Brewing》2010,116(3):215-229
The authenticity of a specific brand of Scotch whisky may be confirmed by comparing analytical data for suspect samples with reference to analytical ranges for the genuine brand. Wider generic authenticity issues exist when a product purports to be Scotch whisky when it has not been produced in Scotland in accordance with the legal definition of Scotch whisky. When such cases reach litigation, courts may ask chemists to analyse suspect products and draw conclusions on authenticity. This paper presents analytical profiles generated from a survey of Malt, Grain and Blended Scotch whiskies and compares the results with whiskies of other origins and examples of a diverse range of suspect products purporting to be Scotch whisky. The concentrations and ratios of concentrations of the major volatile compounds (or congeners), particularly methanol, n‐propanol, isobutanol and 2‐ and 3‐methyl butanol, were found to be important factors in the authenticity decision‐making process. In addition, the absence of known Scotch whisky congeners, the presence of compounds known to be absent from genuine whisky and abnormal maturation congener profiles all contributed to the decision process. From this review of genuine analytical profiles, an experimental protocol for determining the authenticity of Scotch whisky is proposed. 相似文献
305.
MacKenzie DA Defernez M Dunn WB Brown M Fuller LJ de Herrera SR Günther A James SA Eagles J Philo M Goodacre R Roberts IN 《Yeast (Chichester, England)》2008,25(7):501-512
Ten medically important Saccharomyces strains, comprising six clinical isolates of Saccharomyces cerevisiae and four probiotic strains of Saccharomyces boulardii, were characterized at the genetic and metabolic level and compared with non-medical, commercial yeast strains used in baking and wine-making. Strains were compared by genetic fingerprinting using amplified fragment length polymorphism (AFLP) analysis, by ribosomal DNA ITS1 sequencing and by metabolic footprinting using both direct injection mass spectrometry (DIMS) and gas chromatography-time of flight-mass spectrometry (GC-ToF-MS). Overall, the clinical isolates fell into different groupings when compared with the non-medical strains, with good but not perfect correlation amongst strains at both the genetic and metabolic levels. Probiotic strains of S. boulardii that are used therapeutically to treat human gastro-intestinal tract disorders showed tight clustering both genetically and metabolically. Metabolomics was found to be of value both as a taxonomic tool and as a means to investigate anomalous links between genotype and phenotype. Key discriminatory metabolites were identified when comparing the three main groups of clinical, probiotic and non-medical strains and included molecules such as trehalose, myo-inositol, lactic acid, fumaric acid and glycerol 3-phosphate. This study confirmed the link between a subset of clinical isolates and baking or probiotic strains but also highlighted that in general the clinical strains were more diverse at both the genomic and metabolic levels. 相似文献