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61.
Smith TJ Hill KK Foley BT Detter JC Munk AC Bruce DC Doggett NA Smith LA Marks JD Xie G Brettin TS 《PloS one》2007,2(12):e1271
Background
Clostridium botulinum and related clostridial species express extremely potent neurotoxins known as botulinum neurotoxins (BoNTs) that cause long-lasting, potentially fatal intoxications in humans and other mammals. The amino acid variation within the BoNT is used to categorize the species into seven immunologically distinct BoNT serotypes (A–G) which are further divided into subtypes. The BoNTs are located within two generally conserved gene arrangements known as botulinum progenitor complexes which encode toxin-associated proteins involved in toxin stability and expression.Methodology/Principal Findings
Because serotype A and B strains are responsible for the vast majority of human botulism cases worldwide, the location, arrangement and sequences of genes from eight different toxin complexes representing four different BoNT/A subtypes (BoNT/A1-Ba4) and one BoNT/B1 strain were examined. The bivalent Ba4 strain contained both the BoNT/A4 and BoNT/bvB toxin clusters. The arrangements of the BoNT/A3 and BoNT/A4 subtypes differed from the BoNT/A1 strains and were similar to those of BoNT/A2. However, unlike the BoNT/A2 subtype, the toxin complex genes of BoNT/A3 and BoNT/A4 were found within large plasmids and not within the chromosome. In the Ba4 strain, both BoNT toxin clusters (A4 and bivalent B) were located within the same 270 kb plasmid, separated by 97 kb. Complete genomic sequencing of the BoNT/B1 strain also revealed that its toxin complex genes were located within a 149 kb plasmid and the BoNT/A3 complex is within a 267 kb plasmid.Conclusions/Significance
Despite their size differences and the BoNT genes they contain, the three plasmids containing these toxin cluster genes share significant sequence identity. The presence of partial insertion sequence (IS) elements, evidence of recombination/gene duplication events, and the discovery of the BoNT/A3, BoNT/Ba4 and BoNT/B1 toxin complex genes within plasmids illustrate the different mechanisms by which these genes move among diverse genetic backgrounds of C. botulinum. 相似文献62.
We study the issue of identifiability of mixture models in the context of capture-recapture abundance estimation for closed populations. Such models are used to take account of individual heterogeneity in capture probabilities, but their validity was recently questioned by Link (2003, Biometrics 59, 1123-1130) on the basis of their nonidentifiability. We give a general criterion for identifiability of the mixing distribution, and apply it to establish identifiability within families of mixing distributions that are commonly used in this context, including finite and beta mixtures. Our analysis covers binomial and geometrically distributed outcomes. In an example we highlight the difference between the identifiability issue considered here and that in classical binomial mixture models. 相似文献
63.
Sherlock O Dobrindt U Jensen JB Munk Vejborg R Klemm P 《Journal of bacteriology》2006,188(5):1798-1807
Glycosylation is a common modulation of protein function in eukaryotes and is biologically important. However, in bacteria protein glycosylation is rare, and relatively few bacterial glycoproteins are known. In Escherichia coli only two glycoproteins have been described to date. Here we introduce a novel member to this exclusive group, namely, antigen 43 (Ag43), a self-recognizing autotransporter protein. By mass spectrometry Ag43 was demonstrated to be glycosylated by addition of heptose residues at several positions in the passenger domain. Glycosylation of Ag43 by the action of the Aah and TibC glycosyltransferases was observed in laboratory strains. Importantly, Ag43 was also found to be glycosylated in a wild-type strain, suggesting that Ag43-glycosylation may be a widespread phenomenon. Glycosylation of Ag43 does not seem to interfere with its self-associating properties. However, the glycosylated form of Ag43 enhances bacterial binding to human cell lines, whereas the nonglycosylated version of Ag43 does not to confer this property. 相似文献
64.
Prevention of bacterial adhesion 总被引:1,自引:0,他引:1
Per Klemm Rebecca Munk Vejborg Viktoria Hancock 《Applied microbiology and biotechnology》2010,88(2):451-459
Management of bacterial infections is becoming increasingly difficult due to the emergence and increasing prevalence of bacterial
pathogens that are resistant to available antibiotics. Conventional antibiotics generally kill bacteria by interfering with
vital cellular functions, an approach that imposes selection pressure for resistant bacteria. New approaches are urgently
needed. Targeting bacterial virulence functions directly is an attractive alternative. An obvious target is bacterial adhesion.
Bacterial adhesion to surfaces is the first step in colonization, invasion, and biofilm formation. As such, adhesion represents
the Achilles heel of crucial pathogenic functions. It follows that interference with adhesion can reduce bacterial virulence.
Here, we illustrate this important topic with examples of techniques being developed that can inhibit bacterial adhesion.
Some of these will become valuable weapons for preventing pathogen contamination and fighting infectious diseases in the future. 相似文献
65.
66.
Glutamine starvation of monocytes inhibits the ubiquitin-proteasome proteolytic pathway 总被引:2,自引:0,他引:2
Zellner M Gerner C Munk Eliasen M Wurm S Pollheimer J Spittler A Brostjan C Roth E Oehler R 《Biochimica et biophysica acta》2003,1638(2):138-148
Peripheral blood monocytes utilize free glutamine (Gln) in addition to glucose as an important energy substrate. Although this demand increases upon activation, monocytes are commonly confronted with decreased plasma Gln during critical illness and thus suffer from Gln-starvation. Here we investigate the influence of Gln-starvation on protein stability and its effects on the monocyte proteome. Gln-starvation caused a reduction of protein degradation which was accompanied by an accumulation of ubiquitin-protein conjugates and a reduction of intracellular ATP. Similar effects were observed under ATP-reducing conditions and in the presence of a proteasome inhibitor. Using two-dimensional gel electrophoresis we identified the IL-1beta precursor protein (pIL-1beta) as the, by far, most induced protein in endotoxin-treated monocytes. The degradation of the short-lived pIL-1beta was strongly reduced during Gln-starvation, while the degradation of the long-lived, constitutively expressed beta-actin was less affected. This indicates that although Gln-starvation reduces protein breakdown on the overall proteasome level, it leads to differential changes in the stability of specific proteins. This selective effect is likely to contribute to the immunocompromised state of monocytes commonly observed during critical illness. 相似文献
67.
Ole Munk 《Acta zoologica》1999,80(4):265-284
The article deals with the structure and presumed functions of the escal photophore found in the bulbous tip of the cephalic fin ray or illicium, situated on the upper part of the head in metamorphosed females in most species of deep-sea anglerfishes (ceratioids). The escal photophore consists of the light gland proper and certain accessory structures. An accessory structure common to all species is a lightproof cup enclosing the light gland and provided with a distal opening, while the escae in a number of ceratioids in addition posses reflecting structures, tubular modifications of which form light guides in some species. The light gland proper is a roughly oval or spherical body, typically consisting of radiating branched glandular tubules arranged around a central escal cavity which communicates with the exterior via the vestibule, a usually slit-like epithelium-lined space lying above the distal part of the light gland. All lumina within the light gland contain bioluminescent symbiotic bacteria. The esca is generally thought to function as a lure, prey being attracted by the light emitted from the photophore and movements of the illicium. A possible additional function may be the ejection of a luminous material to confuse predators. 相似文献
68.
Summary . We study the issue of identifiability of mixture models in the context of capture–recapture abundance estimation for closed populations. Such models are used to take account of individual heterogeneity in capture probabilities, but their validity was recently questioned by Link (2003, Biometrics 59, 1123–1130) on the basis of their nonidentifiability. We give a general criterion for identifiability of the mixing distribution, and apply it to establish identifiability within families of mixing distributions that are commonly used in this context, including finite and beta mixtures. Our analysis covers binomial and geometrically distributed outcomes. In an example we highlight the difference between the identifiability issue considered here and that in classical binomial mixture models. 相似文献
69.
H Kirchner G Darai H M Hirt K Keyssner K Munk 《Journal of immunology (Baltimore, Md. : 1950)》1978,120(2):641-645
Spleen cells of B6 mice not previously immunized were induced to DNA synthesis by supernatants from HSV-infected tissue culture. The stimulatory principle could be passed through a 45-micrometer filter and sedimented at 100,000 x G. It was abolished by UV light, heating at 56 degrees C, and by an anti-HSV serum. The possibility that the observed stimulation was caused by LPS was therefore excluded, and there was a-so no indication of mycoplasma contamination. Partial purification of spleen cells from macrophages resulted in an increased stimulation by HSV. From experiments with nylon columns, anti-theta antibody, and nude mice it was concluded that HSV acted as a B cell mitogen. Strains of both HSV types 1 and 2 were stimulatory for B6 spleen cells. Of nine freshly isolated HSV strains with identical passage history (twice in HEF) four were strongly stimulatory, three showed a moderate stimulation, and two did not stimulate. Spleen cells from A/J and DBA/2 mice were stimulated to the same extent by HSV (WAL) as spleen cells from B6 mice. No viral replication was demonstrable in B6 spleen cell cultures stimulated for DNA synthesis by HSV. Thus our study demonstrates induction of cellular DNA synthesis in B lymphocytes by HSV which is abolished by inactivation of the virus. 相似文献
70.
Darai G. Flügel R. M. Braun R. Berger U. Matz B. Munk K. 《In vitro cellular & developmental biology. Plant》1978,14(6):536-542
Summary Rat and tupaia 41° C temperature variant cell clones were derived from parental embryonic cells, cloned and established in
tissue cultures. Both variant cell clones grew permanently at 41° C. The morphology of these cell clones was altered in comparison
to the original fibroblast cell clones. The cell biological characterization of the rat and tupaia 41° C temperature variant
cell clones showed that both cell clones were stable. After abolishing the selection pressure (incubation at 41° C) for more
than 10 further cell passages by incubation at 37°C and then raising the temperature again to 41° C, neither of the cell clones
lost their newly acquired property of prowing at 41° C. This fact demonstrates that the newly acquired property is certain
to be genetically manifest in both cell clones. The modal number of chromosomes of the rat 41° C temperature variant cell
clone was increased, and the case of the tupaia variant cell clone, bimodality was observed. The plating efficiency of both
cell clones did not rise significantly in comparison to the parental cells. Neither of the 41° C temperature variant cell
clones grew in semi-solid medium.
This work was partially supported by the Deutsche Forschungsgemeinschaft, Sonderforschungsbereich 136. 相似文献