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Functional and ultrastructural effects of nontypeable haemophilus influenzae in a hamster trachea organ culture system 总被引:1,自引:0,他引:1
Joseph M. Mylotte Richard R. Stack Timothy F. Murphy John Asirwatham Michael A. Apicella 《In vitro cellular & developmental biology. Plant》1985,21(10):575-582
Summary A hamster trachea organ culture system was utilized to evaluate quantitatively the effects of a strain of nontypeableHaemophilus influenzae (NTHI) and culture supernatants of the same strain on ciliary activity. Tracheal explants were maintained in organ culture
for 96 to 144 h and ciliary activity was observed daily with an inverted microscope. Explants continuously exposed to a strain
of NTHI had a progressive decline in ciliary activity which was significantly lower than uninfected controls evaluated concomitantly
by 48 h of exposure and thereafter. Histologic studies revealed a progressive degeneration of mucosal cells and exfoliation
of ciliated cells. Scanning electron microscopy showed little adherence of NTHI to the mucosal surface. Sterile broth cultures
of NTHI and supernatants of organ cultures infected with the same NTHI strain had no adverse effect on ciliary activity. Infected
tracheal explants treated with ampicillin 24, 48, or 72 h after continuous bacterial challenge had no significant decline
in ciliary activity compared to controls. The lack of adherence and the histologic changes observed when hamster trachea cultures
were infected with NTHI suggested a toxin might mediate the damage observed. Broth and organ culture supernatants, however,
produced no damage. Therefore, further studies are needed to determine the role, if any, of a toxin in the production of damage
to hamster tracheal explants by NTHI.
This work was supported by a Merit Review grant from the Veterans Administration and by Grant AI-19641 from the National Institute
of Allergy and Infectious Diseases. 相似文献
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The Escherichia coli arginine repressor (ArgR) is an l -arginine-dependent DNA-binding protein that controls expression of the arginine biosynthetic genes and is required as an accessory protein in Xer site-specific recombination at cer and related recombination sites in plasmids. Site-directed mutagenesis was used to isolate two mutants of E. coli ArgR that were defective in arginine binding. Results from in vivo and in vitro experiments demonstrate that these mutants still act as repressors and bind their specific DNA sequences in an arginine-independent manner. Both mutants support Xer site-specific recombination at cer. One of the mutant proteins was purified and shown to bind to its DNA target sequences in vitro with different affinity and as a different molecular species to wild-type ArgR. 相似文献
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The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from
nucleotide sequence variation across a 765-bp region in the cytochrome
oxidase I and II genes of the mitochondrial genome. Most parsimonious
relationships of 25 haplotypes from 16 Greya species and two outgroup
genera (Tetragma and Prodoxus) showed substantial congruence with the
species relationships indicated by morphological variation. Differences
between mitochondrial and morphological trees were found primarily in the
positions of two species, G. variabilis and G. pectinifera, and in the
branching order of the three major species groups in the genus. Conflicts
between the data sets were examined by comparing levels of homoplasy in
characters supporting alternative hypotheses. The phylogeny of Greya
species suggests that host-plant association at the family level and larval
feeding mode are conservative characters. Transition/transversion ratios
estimated by reconstruction of nucleotide substitutions on the phylogeny
had a range of 2.0-9.3, when different subsets of the phylogeny were used.
The decline of this ratio with the increase in maximum sequence divergence
among taxa indicates that transitions are masked by transversions along
deeper internodes or long branches of the phylogeny. Among transitions,
substitutions of A-->G and T-->C outnumbered their reciprocal
substitutions by 2-6 times, presumably because of the approximately 4:1
(77%) A+T-bias in nucleotide base composition. Of all transversions,
73%-80% were A<-->T substitutions, 85% of which occurred at third
positions of codons; these estimates did not decrease with an increase in
maximum sequence divergence of taxa included in the analysis. The high
frequency of A<-->T substitutions is either a reflection or an
explanation of the 92% A+T bias at third codon positions.
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