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71.
72.
Sequence variation in the guillemot (Alcidae: Cepphus) mitochondrial control region and its nuclear homolog 总被引:4,自引:0,他引:4
We describe sequence variation in the mitochondrial control region and its
nuclear homolog in three species and seven subspecies of guillemots
(Cepphus spp.). Nuclear homologs of the 5' end of the control region were
found in all individuals. Nuclear sequences were approximately 50%
divergent from their mitochondrial counterparts and formed a distinct
phylogenetic clade; the mitochondrial-nuclear introgression event must have
predated the radiation of Cepphus. As in other vertebrates, the guillemot
control region has a relatively conserved central block flanked by
hypervariable 5' and 3' ends. Mean pairwise interspecific divergence values
among control regions were lower than those in other birds. All individuals
were heteroplasmic for the number of simple tandem nucleotide repeats
(A(n)C) at the 3' end of the control region. Phylogenetic analyses suggest
that black guillemots are basal to pigeon and spectacled guillemots, but
evolutionary relationships among subspecies remain unresolved, possibly due
to incomplete lineage sorting. Describing molecular variation in nuclear
homologs of mitochondrial genes is of general interest in phylogenetics
because, if undetected, the homologs may confound interpretations of
mitochondrial phylogenies.
相似文献
73.
A phylogenetic survey using the polymerase chain reaction (PCR) has
identified four major P element subfamilies in the saltans and willistoni
species groups of Drosophila. One subfamily, containing about half of the
sequences studied, consists of elements that are very similar to the
canonical (and active) P element from D. melanogaster. Within this
subfamily, nucleotide sequence differentiation among different copies from
the same species and among elements from different species is relatively
low. This observation suggests that the canonical elements are relatively
recent additions to the genome or, less likely, are evolving slowly
relative to the other subfamilies. Elements belonging to the three
noncanonical lineages are distinct from the canonical elements and from one
another. Furthermore, there is considerably more sequence variation, on the
average, within the noncanonical subfamilies compared to the canonical
elements. Horizontal transfer and the coexistence of multiple,
independently evolving element subfamilies in the same genome may explain
the distribution of P elements in the saltans and willistoni species
groups. Such explanations are not mutually exclusive, and each may be
involved to varying degrees in the maintenance of P elements in natural
populations of Drosophila.
相似文献
74.
Pig Reticulocytes. III. Glucose permeability in naturally occurring reticulocytes and red cells from newborn piglets 总被引:1,自引:1,他引:0
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The loss of facilitated glucose transport of red cells occurring in the newborn pig was monitored in 11 density-separated cells from birth to a 4 wk of age. At birth there was a threefold increase in glucose permeability from the lightest cells to the most dense, suggesting that cells having progressively less glucose permeability are released into the circulation as gestation proceeds. Because of extraordinary stimulation of erythropoietic activity, the uppermost top fraction constituting 2-3 percent of the total cells is composed purely of reticulocytes in the growing animal. The glucose permeability of these reticulocytes which at birth has a slow but significant rate of 3.7 μmol/ml cell x min at 25 degrees C is rapidly decreased within 3-4 days to the level of reticulocytes produced in the adult in response to phenylhydrazine assault. Moreover, reticulocytes themselves discard their membrane permeability to glucose in the course of maturation to red cells. Thus, even though reticulocytes at birth are permeable to glucose, they will become red cells practically impervious to glucose within a few days. These findings suggest that the transition from a glucose- permeable fetal state to a glucose-impermeable postnatal state is brought about by two mechanisms: (a) dilution of fetal cells by glucose-impervious cells produced coincidentally with or shortly after birth; and (b) elimination of fetal cells, which have a shorter half-life, from the circulation. 相似文献
75.
Brennan FM Smith NM Owen S Li C Amjadi P Green P Andersson A Palfreeman AC Hillyer P Foey A Beech JT Feldmann M 《Arthritis research & therapy》2008,10(2):R36-13
Background
Previously we described a system whereby human peripheral blood T cells stimulated for 8 days in a cytokine cocktail acquired effector function for contact-dependent induction of proinflammatory cytokines from monocytes. We termed these cells cytokine-activated (Tck) cells and found that the signalling pathways elicited in the responding monocytes were identical whether they were placed in contact with Tck cells or with T cells isolated from rheumatoid arthritis (RA) synovial tissue.Methods
Here, using magnetic beads and fluorescence-activated cell sorting, we extensively phenotype the Tck effector cells and conclude that effector function resides within the CD4+CD45RO+, CCR7-, CD49dhigh population, and that these cells are derived from the effector memory CD4+ T cells in resting blood.Results
After stimulation in culture, these cells produce a wide range of T-cell cytokines, undergo proliferation and differentiate to acquire an extensively activated phenotype resembling RA synovial T cells. Blocking antibodies against CD69, CD18, or CD49d resulted in a reduction of tumour necrosis factor-α production from monocytes stimulated with CD4+CD45RO+ Tck cells in the co-culture assay. Moreover, blockade of these ligands also resulted in inhibition of spontaneous tumour necrosis factor-α production in RA synovial mononuclear cell cultures.Conclusion
Taken together, these data strengthen our understanding of T-cell effector function, highlight the multiple involvement of different cell surface ligands in cell-cell contact and, provide novel insights into the pathogenesis of inflammatory RA disease. 相似文献76.
77.
Previous studies have indicated that peripheral administration of interleukin-6 (IL-6) increases brain concentrations of tryptophan and 5-hydroxyindoleacetic acid (5-HIAA), the major catabolite of serotonin (5-HT). To determine whether these changes were related to increased synaptic release of 5-HT, we studied the responses to peripheral administration of IL-6 by in vivo microdialysis and in vivo amperometry. Intraperitoneal injection of recombinant IL-6 resulted in an elevation of microdialysate concentrations of 5-HT in the rat striatum. Also, amperometric measurements indicated that i.p. IL-6 enhanced the 5-HT-like signal obtained from the striatum following electrical stimulation of the dorsal raphe nucleus. These results indicate that the increases in brain concentrations of 5-HIAA observed in earlier studies indeed reflect increased synaptic release of 5-HT. 相似文献
78.
Marloes L. de Groote Pernette J. Verschure Marianne G. Rots 《Nucleic acids research》2012,40(21):10596-10613
Despite significant advances made in epigenetic research in recent decades, many questions remain unresolved, especially concerning cause and consequence of epigenetic marks with respect to gene expression modulation (GEM). Technologies allowing the targeting of epigenetic enzymes to predetermined DNA sequences are uniquely suited to answer such questions and could provide potent (bio)medical tools. Toward the goal of gene-specific GEM by overwriting epigenetic marks (Epigenetic Editing, EGE), instructive epigenetic marks need to be identified and their writers/erasers should then be fused to gene-specific DNA binding domains. The appropriate epigenetic mark(s) to change in order to efficiently modulate gene expression might have to be validated for any given chromatin context and should be (mitotically) stable. Various insights in such issues have been obtained by sequence-specific targeting of epigenetic enzymes, as is presented in this review. Features of such studies provide critical aspects for further improving EGE. An example of this is the direct effect of the edited mark versus the indirect effect of recruited secondary proteins by targeting epigenetic enzymes (or their domains). Proof-of-concept of expression modulation of an endogenous target gene is emerging from the few EGE studies reported. Apart from its promise in correcting disease-associated epi-mutations, EGE represents a powerful tool to address fundamental epigenetic questions. 相似文献
79.
5-Aminolevulinic acid (ALA), a precursor of porphyrin synthesis, increased the production of various porphyrin compounds in Candida guilliermondii cells. Metalloporphyrins and protoporphyrin IX (PPIX) were predominantly accumulated, respectively, at ALA concentrations of 0.2-0.4 mM and at those higher than 1.5 mM. 2,2;-Dipyridyl which complexed with bivalent metals significantly increased the content of endogenous PPIX even at ALA concentrations lower than 0.5 mM. Under these conditions, the yeast sensitivity to photodynamic effect of visible light (400-600 nm) dramatically increased due to photosensitization by endogenous PPIX. 相似文献