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31.
Proteolytic enzymes have been used both to modify properties of the cell membrane and to dissociate cells from many tissues including pituitary (4, 5, 12). Exposure of secretory tissues to pronase can alter their secretory response. Thus incubation of pancreatic islets of Langerhans in the presence of low concentrations of pronase increased the subsequent release of insulin in the presence of stimulatory and nonstimulatory glucose concentrations (7). The purpose of the present investigation was to determine whether low concentrations of pronase have the same stimulatory effect on the release of a pituitary hormone, growth hormone. Such an effect on hormone release could be of some importance in view of the development of dissociated cell systems as models for the study of the control of hormone release (4, 5). 相似文献
32.
Viktoria Gloy Wolfgang Langhans Jacquelien JG Hillebrand Nori Geary Lori Asarian 《Biology of sex differences》2011,2(1):1-13
Background
Men are at an increased risk of dying from heart failure caused by inflammatory heart diseases such as atherosclerosis, myocarditis and dilated cardiomyopathy (DCM). We previously showed that macrophages in the spleen are phenotypically distinct in male compared to female mice at 12 h after infection. This innate immune profile mirrors and predicts the cardiac immune response during acute myocarditis.Methods
In order to study sex differences in the innate immune response, five male and female BALB/c mice were infected intraperitoneally with coxsackievirus B3 (CVB3) or phosphate buffered saline and their spleens were harvested 12 h later for microarray analysis. Gene expression was determined using an Affymetrix Mouse Gene 1.0 ST Array. Significant gene changes were verified by quantitative real-time polymerase chain reaction or ELISA.Results
During the innate immune response to CVB3 infection, infected males had higher splenic expression of genes which are important in regulating the influx of cholesterol into macrophages, such as phospholipase A2 (PLA2) and the macrophage scavenger receptor compared to the infected females. We also observed a higher expression in infected males compared to infected females of squalene synthase, an enzyme used to generate cholesterol within cells, and Cyp2e1, an enzyme important in metabolizing cholesterol and steroids. Infected males also had decreased levels of the translocator protein 18 kDa (TSPO), which binds PLA2 and is the rate-limiting step for steroidogenesis, as well as decreased expression of the androgen receptor (AR), which indicates receptor activation. Gene differences were not due to increased viral replication, which was unaltered between sexes.Conclusions
We found that, compared to females, male mice had a greater splenic expression of genes which are important for cholesterol metabolism and activation of the AR at 12 h after infection. Activation of the AR has been linked to increased cardiac hypertrophy, atherosclerosis, myocarditis/DCM and heart failure in male mice and humans. 相似文献33.
Kathryn R. Ayres Carl D. Sayer Eleanor R. Skeate Martin R. Perrow 《Biodiversity and Conservation》2008,17(9):2153-2168
This palaeolimnological study investigates recent changes in the biological structure of an English shallow lake (Upton Great
Broad, Norfolk). By focusing on the historical occurrence of submerged macrophytes, particularly the rare UK species, Najas marina L. (Holly-leaved Naiad), we address a management question that frequently arises for shallow lakes, namely whether to undertake
sediment removal to increase water depth and/or restore conservation value. Macro-remains of aquatic macrophytes and molluscs
were analysed in two littoral sediment cores and combined with other historical ecological data covering the last 100 years.
Before around 1900, the lake had Chara meadows (including at least three species) and an associated species-rich community of Mollusca. Between around 1900–1970
a period of high angiosperm diversity is suggested with a reduction of Characeae and the development of patches of water-lily
(particularly Nymphaea alba L.) and fen swamp in the open water. Then, after around 1970, our data indicate a rapid shift towards Najas-dominance coupled with a decrease in the seasonal length of the plant-covered period. The expansion of Najas was clearly associated with, and may even be dependent upon, a highly unusual fluid, green sediment formation that developed
at the site from around the same time. Thus, despite the loss of an earlier more diverse vegetation and associated fauna,
we suggest that best practice conservation may be allow natural site development and not to undertake active management such
as sediment removal which might threaten the status of Najas. Our conclusion could only have been arrived at through the long-term ecological perspective that a palaeolimnological approach
provides. 相似文献
34.
Yuansha Chen Peter Bystricky Jacob Adeyeye Pinaki Panigrahi Afsar Ali Judith A Johnson CA Bush JG MorrisJr OC Stine 《BMC microbiology》2007,7(1):20
Background
In V. cholerae, the biogenesis of capsule polysaccharide is poorly understood. The elucidation of capsule structure and biogenesis is critical to understanding the evolution of surface polysaccharide and the internal relationship between the capsule and LPS in this species. V. cholerae serogroup O31 NRT36S, a human pathogen that produces a heat-stable enterotoxin (NAG-ST), is encapsulated. Here, we report the covalent structure and studies of the biogenesis of the capsule in V. cholerae NRT36S. 相似文献35.
Andrew JG Simpson 《Genome biology》2000,1(1):reports411.1-reports4112
A meeting report of the sessions on human, eukaryotic and bacterial genome sequencing at the American Society for Microbiology and Institut Pasteur joint conference: Genomes 2000 International Conference on Microbial and Model Genomes, Paris, April 11-15, 2000 相似文献
36.
Chromosomal DNA from 23 closely related, pathogenic strains of Escherichia
coli was digested and probed for the insertion sequences IS1, IS2, IS4,
IS5, and IS30. Under the assumption that elements residing in DNA
restriction fragments of the same apparent length are identical by descent,
parsimony analysis of these characters yielded a unique phylogenetic tree.
This analysis not only distinguished among bacterial strains that were
otherwise identical in their biochemical characteristics and enzyme
electrophoretic mobilities, but certain aspects of the topology of the tree
were consistent across several unrelated insertion elements. The
distribution of IS elements was then reexamined in light of the inferred
phylogenetic relationships to investigate the biological properties of the
elements, such as rates of insertion and deletion, and to discover apparent
recombinational events. The analysis shows that the pattern of distribution
of insertion elements in the bacterial genome is sufficiently stable for
epidemiological studies. Although the rate of recombination by conjugation
has been postulated to be low, at least two such events appear to have
taken place.
相似文献
37.
Homologues of glucosephosphate isomerase (GPI, EC 5.3.1.9) were purified to
homogeneity and kinetically characterized from Mytilus edulis and Isognomon
alatus, two bivalve molluscs experiencing contrasting thermal environments.
The enzyme isolated from I. alatus functions at warmer temperatures (25-35
C) than GPI from M. edulis, a species that inhabits colder marine littoral
habitats (5-20 C). The former exhibits apparent first-order (with respect
to substrate) catalytic rate constants (Vmax/KM) in vitro that become
progressively greater than the mussel enzyme as the assay temperature is
raised. Apparent zero-order catalytic rate constants (Vmax) are relatively
less differentiated. Catalytic efficiency, defined as the rate at which a
catalytic event occurs in either reaction direction for reference standard
states (substrate concentrations), is greater for the enzyme from the
tropical species (I. alatus) at all realistic combinations of temperature
and substrate concentration except for the lowest temperatures and highest
substrate concentrations, where the GPI from the boreal/temperate M. edulis
is more efficient. This pattern of catalytic divergence appears to be due
primarily to differentiation in Vmax/KM. These results and other published
data are reviewed and shown to be inconsistent with claims that adaptation
of enzymes to higher cell temperatures requires a loss in catalytic
efficiency.
相似文献
38.
Jacques-Henri Torres Michael Mechali Olivier Romieu Paul Tramini Sylvie Callas Frédéric JG Cuisinier Bernard Levallois 《Biomedical engineering online》2011,10(1):28
Background
Most dental implant systems are presently made of two pieces: the implant itself and the abutment. The connection tightness between those two pieces is a key point to prevent bacterial proliferation, tissue inflammation and bone loss. The leak has been previously estimated by microbial, color tracer and endotoxin percolation. 相似文献39.
40.