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101.
Myelinogenesis in optic nerve. A morphological, autoradiographic, and biochemical analysis
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Morphological, autoradiographic, and biochemical methods were used to study the time of appearance, distribution, and nature of sulfated constituents in the developing rat optic nerve. Electron microscope studies showed that myelination begins (6 days postnatal) shortly after the appearance of oligodendroglia (5 days postnatal). Over the ensuing 3 wk, myelination increased rapidly. During the 1st postnatal wk, mucopolysaccharides and glycoproteins were labeled with 35S and autoradiographs showed grains over arachnoidal cells, astroglia, and the glia limitans. These results indicated that astroglia synthesize sulfated mucopolysaccharides of the glia limitans. After the onset of myelination, however, the major portion of [35S]sulfate was incorporated into sulfatide. Autoradiographs showed a shift of radioactive grains from astroglia and arachnoidal cells to myelin, indicating that actively myelinating oligodendroglia incorporate [35S]sulfate into myelin sulfatide; there was a concomitant increase in the activity of cerebroside sulfotransferase. In addition, the increasing amounts of proteolipid protein and myelin basic protein corresponded with the morphological appearance of myelin. These results point to a strict correlation between the structural and biochemical changes occurring during myelination. This system provides a useful model for studies designed to evaluate the effects of various perturbations on the process of myelination. 相似文献
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Anne-Ga?lle Biacabe Jorg G Jacobs Anna Bencsik Jan PM Langeveld Thierry GM Baron 《朊病毒》2007,1(1):61-68
We previously reported that some cattle affected by bovine spongiform encephalopathy (BSE) showed distinct molecular features of the protease-resistant prion protein (PrPres) in Western blot, with a 1–2 kDa higher apparent molecular mass of the unglycosylated PrPres associated with labelling by antibodies against the 86–107 region of the bovine PrP protein (H-type BSE). By Western blot analyses of PrPres, we now showed that the essential features initially described in cattle were observed with a panel of different antibodies and were maintained after transmission of the disease in C57Bl/6 mice. In addition, antibodies against the C-terminal region of PrP revealed a second, more C-terminally cleaved, form of PrPres (PrPres #2), which, in unglycosylated form, migrated as a ≈ 14 kDa fragment. Furthermore, a PrPres fragment of ≈7 kDa, which was not labelled by C-terminus-specific antibodies and was thus presumed to be a product of cleavage at both N- and C-terminal sides of PrP protein, was also detected. Both PrPres #2 and ≈7 kDa PrPres were detected in cattle and in C57Bl/6 infected mice. These complex molecular features are reminiscent of findings reported in human prion diseases. This raises questions regarding the respective origins and pathogenic mechanisms in prion diseases of animals and humans.Key Words: prion, BSE, Creutzfeldt-Jakob, Gerstmann-Sträussler-Scheinker, Western blot, amyloid 相似文献
104.
Gibson S Kibiki Bert Mulder Wil MV Dolmans Jessica L de Beer Martin Boeree Noel Sam Dick van Soolingen Christophe Sola Adri GM van der Zanden 《BMC microbiology》2007,7(1):51
Background
Tuberculosis (TB) is a major health problem and HIV is the major cause of the increase in TB. Sub-Saharan Africa is endemic for both TB and HIV infection. Determination of the prevalence of M. tuberculosis strains and their drug susceptibility is important for TB control. 相似文献105.
Transfection of neonatal rat Schwann cells with SV-40 large T antigen gene under control of the metallothionein promoter 总被引:5,自引:2,他引:5
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G I Tennekoon J Yoshino K W Peden J Bigbee J L Rutkowski Y Kishimoto G H DeVries G M McKhann 《The Journal of cell biology》1987,105(5):2315-2325
Secondary cultures of Schwann cells were transfected with a plasmid containing the SV-40 T antigen gene expressed under the control of the mouse metallothionein-I promoter. We used the calcium phosphate method for transfection and obtained a transfection efficiency of 0.01%. The colonies were cloned by limited dilution, and these cloned cell lines were carried in medium containing zinc chloride (100 microM). One cloned cell line, which has now been carried for 180 doublings, appears to have a transformed phenotype with a doubling time of 20 h. These cells express SV-40 T antigen while maintaining established Schwann cell properties (positive staining for 217c, Ran-2, A5E3, glial fibrillary acidic protein, presence of 2',3'-cyclic nucleotide phosphohydrolase [CNPase] activity, and the ability to synthesize sulfogalactosylceramide and mRNA for the myelin protein, P0). Removal of zinc chloride from the medium resulted in reduced expression of T antigen and a change in the appearance of the cells to a more bipolar shape, although they still did not exhibit contact inhibition and maintained a doubling time of 20 h. These cells now became Ran-2-negative and showed increases in CNPase activity and in their ability to synthesize sulfogalactosylceramide. The amount of P0 mRNA remained unchanged. Transfected Schwann cells, however, stopped dividing when they contacted either basal lamina or neurites and became bipolar in appearance. The Schwann cells in contact with the neurites then extended processes to wrap around bundles of neurites. Transfection with the SV-40 T antigen gene therefore provides a method for obtaining Schwann cell lines that continue to express properties associated with untransfected cells in culture and may be used to study axon-Schwann cell interaction. 相似文献
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J A Benjamins M Guarnieri K Miller M Sonneborn G M McKhann 《Journal of neurochemistry》1974,23(4):751-757
—Cerebroside sulphotransferase activity in oligodendroglia from calf brain is 8-fold greater per cell than in calf neurons isolated at the same time under similar conditions. However, neuronal cell fractions from calf or rat brain have significant sulphotransferase activity, and in neurons isolated from rat brain at various ages, the capacity to synthesize sulphatide increases during myelination. The neuronal and oligodendroglial enzymes have similar substrate specificities and pH optima. Less of the enzyme could be extracted with Triton X-100 from the isolated cells than from microsomes prepared from whole brain. 相似文献
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