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101.
Immunohistochemistry (IHC) is used to detect antibody-specific antigens in tissues; the results depend on the ability of the primary antibodies to bind to their antigens. Therefore, results depend on the quality of preservation of the specimen. Many investigators have overcome the deleterious effects of over-fixation on the binding of primary antibodies to specimen antigens using IHC, but if the specimen is under-fixed or fixation is delayed, false negative results could be obtained despite certified laboratory practices. Microtubule-associated protein 2 (MAP2) is an abundant microtubule-associate protein that participates in the outgrowth of neuronal processes and synaptic plasticity; it is localized primarily in cell bodies and dendrites of neurons. MAP2 immunolabeling has been reported to be absent in areas of the entorhinal cortex and hippocampus of Alzheimer’s disease brains that were co-localized with the dense-core type of amyloid plaques. It was hypothesized that the lack of MAP2 immunolabeling in these structures was due to the degradation of the MAP2 antigen by the neuronal proteases that were released as the neurons lysed leading to the formation of these plaques. Because MAP2 is sensitive to proteolysis, we hypothesized that changes in MAP2 immunolabeling may be correlated with the degree of fixation of central nervous system (CNS) tissues. We detected normal MAP2 immunolabeling in fixed rat brain tissues, but MAP2 immunolabeling was decreased or lost in unfixed and delayed-fixed rat brain tissues. By contrast, two ubiquitous CNS-specific markers, myelin basic protein and glial fibrillary acidic protein, were unaffected by the degree of fixation in the same tissues. Our observations suggest that preservation of various CNS-specific antigens differs with the degree of fixation and that the lack of MAP2 immunolabeling in the rat brain may indicate inadequate tissue fixation. We recommend applying MAP2 IHC for all CNS tissues as a pre-screen to assess the quality of the tissue preservation and to avoid potentially false negative IHC results. 相似文献
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Louise A O'Sullivan Erwan G Roussel Andrew J Weightman Gordon Webster Casey RJ Hubert Emma Bell Ian Head Henrik Sass R John Parkes 《The ISME journal》2015,9(4):922-933
Bacterial spores are widespread in marine sediments, including those of thermophilic, sulphate-reducing bacteria, which have a high minimum growth temperature making it unlikely that they grow in situ. These Desulfotomaculum spp. are thought to be from hot environments and are distributed by ocean currents. Their cells and spores upper temperature limit for survival is unknown, as is whether they can survive repeated high-temperature exposure that might occur in hydrothermal systems. This was investigated by incubating estuarine sediments significantly above (40–80 °C) maximum in situ temperatures (∼23 °C), and with and without prior triple autoclaving. Sulphate reduction occurred at 40–60 °C and at 60 °C was unaffected by autoclaving. Desulfotomaculum sp. C1A60 was isolated and was most closely related to the thermophilic D. kuznetsoviiT (∼96% 16S rRNA gene sequence identity). Cultures of Desulfotomaculum sp. C1A60, D. kuznetsoviiTand D. geothermicum B2T survived triple autoclaving while other related Desulfotomaculum spp. did not, although they did survive pasteurisation. Desulfotomaculum sp. C1A60 and D. kuznetsovii cultures also survived more extreme autoclaving (C1A60, 130 °C for 15 min; D. kuznetsovii, 135 °C for 15 min, maximum of 154 °C reached) and high-temperature conditions in an oil bath (C1A60, 130° for 30 min, D. kuznetsovii 140 °C for 15 min). Desulfotomaculum sp. C1A60 with either spores or predominantly vegetative cells demonstrated that surviving triple autoclaving was due to spores. Spores also had very high culturability compared with vegetative cells (∼30 × higher). Combined extreme temperature survival and high culturability of some thermophilic Desulfotomaculum spp. make them very effective colonisers of hot environments, which is consistent with their presence in subsurface geothermal waters and petroleum reservoirs. 相似文献
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M D Lee G E Quinton R E Beeman A A Biehle R L Liddle D E Ellis RJ Buchanan Jr 《Journal of industrial microbiology & biotechnology》1997,18(2-3):106-115
For the full scale implementation of in situ anaerobic bioremediation of tetrachloroethene (PCE) in groundwater, the following issues must be addressed: which organic
substrates at which concentration would be most effective in promoting dechlorination and are economical; how far the substrate,
electron acceptor, and nutrients can be transported in the aquifer; and the placement of delivery and recovery wells for
distributing these amendments. In a microcosm study, almost all of the tested inexpensive substrates supported reductive
dechlorination of PCE through vinyl chloride (VC) under methanogenic conditions. A minimum of about 60 mg L−1 of organic carbon was needed to dechlorinate 23 μM PCE with a single feeding. In a second microcosm study dechlorination
stopped at 1,2-dichloroethene (DCE) in microcosms fed higher concentrations of several substrates. At the highest concentrations
the substrates inhibited DCE production. Three field tracer tests were conducted to evaluate methods to distribute the amendments
across the aquifer. The natural groundwater gradient is not sufficient to distribute substrate evenly. Groundwater injection
at 60 times the natural flux rate increased the distribution of substrate. A mixing strategy of cross-gradient injection
further increased the distribution of the substrate. Ammonia-nitrogen, sulfate, and phosphate were retarded relative to
the substrate and inorganic tracer.
Received 30 October 1995/ Accepted in revised form 07 June 1996 相似文献
107.
Cytosolic isocitrate dehydrogenase in humans, mice, and voles and phylogenetic analysis of the enzyme family 总被引:3,自引:0,他引:3
Nekrutenko A; Hillis DM; Patton JC; Bradley RD; Baker RJ 《Molecular biology and evolution》1998,15(12):1674-1684
In this study, we report cDNA sequences of the cytosolic NADP-dependent
isocitrate dehydrogenase for humans, mice, and two species of voles
(Microtus mexicanus and Microtus ochrogaster). Inferred amino acid
sequences from these taxa display a high level of amino acid sequence
conservation, comparable to that of myosin beta heavy chain, and share
known structural features. A Caenorhabditis elegans enzyme that was
previously identified as a protein similar to isocitrate dehydrogenase is
most likely the NADP-dependent cytosolic isocitrate dehydrogenase enzyme
equivalent, based on amino acid similarity to mammalian enzymes and
phylogenetic analysis. We also suggest that NADP-dependent isocitrate
dehydrogenases characterized from alfalfa, soybean, and eucalyptus are most
likely cytosolic enzymes. The phylogenetic tree of various isocitrate
dehydrogenases from eukaryotic sources revealed that independent gene
duplications may have given rise to the cytosolic and mitochondrial forms
of NADP-dependent isocitrate dehydrogenase in animals and fungi. There
appears to be no statistical support for a hypothesis that the
mitochondrial and cytosolic forms of the enzyme are orthologous in these
groups. A possible scenario of the evolution of NADP-dependent isocitrate
dehydrogenases is proposed.
相似文献
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