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61.
Genetic analysis of the population structure of the western blacklegged tick, Ixodes pacificus Cooley & Kohls, was conducted using allozymes. This vector tick transmits the Lyme disease spirochete, Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner, in the far-western United States. It ranges from British Columbia to Baja California and disjunct populations are present in Oregon, Nevada, Utah, and Arizona. Host-seeking adult ticks were collected from vegetation across the range of the species and were partially fed on rabbits prior to analysis. Twelve putative loci were resolved using starch gel electrophoresis. One locus, glucose-6-phosphate isomerase, formed an apparent north/south latitudinal cline and showed significant geographic structure. None of the remaining loci exhibited much genetic differentiation. Estimates of gene flow were high relative to other arthropods. Isolation-by-distance analysis suggests a recent and rapid range expansion. We conclude that the overall lack of differentiation is due high rates of gene flow. 相似文献
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The protein tyrosine phosphatase PTP-PEST displays remarkable substrate specificity, in vitro and in vivo for p130cas a signalling intermediate implicated in mitogenic signalling, cell-adhesion induced signalling, and in transformation by a variety of oncogenes. We have identified a high affinity interaction between the SH3 domain of p130cas and a proline-rich sequence (P335PPKPPR) within the C-terminal segment of PTP-PEST. Mutation of proline 337 within this sequence to alanine significantly impairs the ability of PTP-PEST to recognise tyrosine phosphorylated p130cas as a substrate, without qualitatively affecting the selectivity of the interaction. Thus the highly specific nature of the interaction between PTP-PEST and p130cas appears to result from a combination of two distinct substrate recognition mechanisms; the catalytic domain of PTP-PEST contributes specificity to the interaction with p130cas, whereas the SH3 domain-mediated association of p130cas and PTP-PEST dramatically increases the efficiency of the interaction. Furthermore, our results indicate that one important function of the p130cas SH3 domain is to associate with PTP-PEST and thereby facilitate the dephosphorylation of p130cas, resulting in the termination of tyrosine phosphorylation-dependent signalling events downstream of p130cas. 相似文献
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Radiographic findings associated with small talar dome fractures were analyzed in 21 patients. Representative cases are presented. The classification of talar dome fractures, and the role of the radiologist in their evaluation, are discussed. 相似文献
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The aim of this study was to describe an outbreak of hepatitis A in a family group which extended to a day care center and to the families of the children attending the same and to determine the risk of acquiring the disease based on exposure to one or several sources of infection. The temporary distribution of the cases and the rate of hepatitis A in the population at risk were analyzed. The risk of acquiring hepatitis by exposure to one or more sources of infection was studied by logistic regression, calculating the odds ratio and the confidence interval of 95%. Initiation of the outbreak was in May 1996, in a 25-year-old male and finalized in November, having affected 63 people. The rate of global attack was of 12% and the risk of infection 18-fold greater (CI 95% = 5.4-61.8) in those exposed to more than one source of infection than in those exposed to only one source and 3.5-fold greater (CI 95% = 1.2-9.9) in the group from 15 to 29 years of age than in those under 14. The massive administration of immunoglobulin was useful to control the hepatitis in the day care center and in the school. The size of this epidemic of hepatitis A was due to its occurrence in a population little exposed to the virus. The greatest involvement was observed in young adults, with person to person transmission and the greater risk of acquiring hepatitis A on exposure to several sources of infection characterizing the outbreak. The possible usefulness of designing prevention strategies with the vaccine should be considered. 相似文献
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Event-related potentials were recorded to brief presentations of four levels of inspiratory flow-resistive loads in young adults. We labeled the loads according to the level of resistance they provided subjectively: sub-threshold (0.34 cmH2O/l per s), near-threshold (4.01 cmH2O/l per s), intermediate (10.4cmH2O/l per s), and near-occlusion (57.5 cmH2O/l per s). No discernible ERPs were elicited by the undetected, sub-threshold stimulus but late components of the ERP (P2, N2, and P3) were observed to each of the three larger stimuli. They were related, in part, to behavioral judgments obtained during the stimulus periods. Both the latency and amplitude of the ERP components varied systematically as a function of stimulus magnitude, in a manner comparable to that observed in ERP paradigms using auditory and visual stimuli. Thus, the data show that event-related potentials to breathing are sensitive to physiologic effects of resistive loads present at the onset of inspiration. Respiratory ERPs may be used to infer sensory and perceptual responses to increases in airflow resistance and, accordingly, may relate to the perception of airflow obstruction in patient populations. 相似文献
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