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61.
Opsteegh M Teunis P Züchner L Koets A Langelaar M van der Giessen J 《International journal for parasitology》2011,41(3-4):343-354
The role of beef in human infections with Toxoplasma gondii is not clear. To get a better understanding of the value of seroprevalence as an indication of the role of beef in human infections with T. gondii we studied the seroprevalence of T. gondii in Dutch cattle and analysed the correlation between detection of antibodies and parasitic DNA. An indirect ELISA was developed and used to test a sample of the Dutch cattle population. Since validation of the ELISA was hampered by a lack of sufficient bovine reference sera, the results were analysed in two different ways: using a cut-off value that was based on the course of the OD in 27 calves followed from birth until 16 months of age, and by fitting a mixture of two normal distributions (binormal mixture model) to the log-transformed ODs observed for the different groups of cattle in the study population. Using the cut-off value, the seroprevalence was estimated at 0.5% for white veal, 6.4% for rosé veal and 25.0% for cattle. However, using the frequency distributions the prevalences were higher: 1.9% for white veal, 15.6% for rosé veal and 54.5% for cattle. Next, for 100 cattle the results with two different serological assays (ELISA and Toxo-Screen DA) were compared with detection of parasites by our recently developed sensitive magnetic capture PCR. Toxoplasma gondii DNA was detected in only two seronegative cattle. This discordance demonstrates that seroprevalence cannot be used as an indicator of the number of cattle carrying infectious parasites. Demonstrating parasitic DNA in seronegative cattle and not in seropositive cattle suggests that only recent infections are detectable. Whether beef from these PCR-positive cattle is infectious to humans remains to be studied. 相似文献
62.
Lysine is catabolized via the saccharopine pathway in plants and mammals. In this pathway, lysine is converted to α-aminoadipic-δ-semialdehyde (AASA) by lysine-ketoglutarate reductase/saccharopine dehydrogenase (LKR/SDH); thereafter, AASA is converted to aminoadipic acid (AAA) by α-aminoadipic-δ-semialdehyde dehydrogenase (AASADH). Here, we investigate the occurrence, genomic organization and functional role of lysine catabolic pathways among prokaryotes. Surprisingly, only 27 species of the 1478 analyzed contain the lkr and sdh genes, whereas 323 species contain aasadh orthologs. A sdh-related gene, identified in 159 organisms, was frequently found contiguously to an aasadh gene. This gene, annotated as lysine dehydrogenase (lysdh), encodes LYSDH an enzyme that directly converts lysine to AASA. Pipecolate oxidase (PIPOX) and lysine-6-aminotransferase (LAT), that converts lysine to AASA, were also found associated with aasadh. Interestingly, many lysdh–aasadh–containing organisms live under hyperosmotic stress. To test the role of the lysine-to-AASA pathways in the bacterial stress response, we subjected Silicibacter pomeroyi to salt stress. All but lkr, sdh, lysdh and aasadh were upregulated under salt stress conditions. In addition, lysine-supplemented culture medium increased the growth rate of S. pomeroyi under high-salt conditions and induced high-level expression of the lysdh–aasadh operon. Finally, transformation of Escherichia coli with the S. pomeroyi lysdh–aasadh operon resulted in increased salt tolerance. The transformed E. coli accumulated high levels of the compatible solute pipecolate, which may account for the salt resistance. These findings suggest that the lysine-to-AASA pathways identified in this work may have a broad evolutionary importance in osmotic stress resistance. 相似文献
63.
Phylogenetic analysis of slippage-like sequence variation in the V4 rRNA expansion segment in tiger beetles (Cicindelidae) 总被引:1,自引:1,他引:0
Sequence variation in the middle part of the small-subunit rRNA was studied
for representatives of the major groups in the family Cicindelidae
(Coleoptera). All taxa exhibited a much expanded segment in variable region
V4 compared to D. melanogaster. This expanded segment was not found in
other groups of beetles, including three taxa in the closely related
Carabidae. Secondary structure predictions indicate that the expanded
segment folds into a single stem-loop structure in all taxa. Despite its
structural conservation, the fragment differs strongly in primary sequence,
even between closely related sister taxa. Several features of these
sequences are consistent with slippage replication as the mechanism that
has generated this sequence variation: the level of internal sequence
repetition as measured by the relative simplicity factor (RSF), its
variation in length between close relatives, and the strong nucleotide bias
compared to the remainder of the gene. With few exceptions, there was also
a correlation between sequence length and the level of sequence repetition,
frequently interpreted as the result of slippage. Phylogenies inferred from
the expansion segment were not consistent with existing hypotheses from
other molecular data for the group. This indicates that DNA sequences in
this region are not homologous throughout the entire Cicindelidae, but it
leaves open the possibility that this expansion segment can be used for
phylogeny reconstruction within subgroups. The implications of a
phylogenetic approach to the understanding of slippage-like evolution are
discussed.
相似文献
64.
Nimmy Mohan Sudheesh AP Nimmy Francis Richard Anderson Rakesh S. Laishram 《Nucleic acids research》2015,43(14):7005-7020
Star-PAP is a nuclear non-canonical poly(A) polymerase (PAP) that shows specificity toward mRNA targets. Star-PAP activity is stimulated by lipid messenger phosphatidyl inositol 4,5 bisphoshate (PI4,5P2) and is regulated by the associated Type I phosphatidylinositol-4-phosphate 5-kinase that synthesizes PI4,5P2 as well as protein kinases. These associated kinases act as coactivators of Star-PAP that regulates its activity and specificity toward mRNAs, yet the mechanism of control of these interactions are not defined. We identified a phosphorylated residue (serine 6, S6) on Star-PAP in the zinc finger region, the domain required for PIPKIα interaction. We show that S6 is phosphorylated by CKIα within the nucleus which is required for Star-PAP nuclear retention and interaction with PIPKIα. Unlike the CKIα mediated phosphorylation at the catalytic domain, Star-PAP S6 phosphorylation is insensitive to oxidative stress suggesting a signal mediated regulation of CKIα activity. S6 phosphorylation together with coactivator PIPKIα controlled select subset of Star-PAP target messages by regulating Star-PAP-mRNA association. Our results establish a novel role for phosphorylation in determining Star-PAP target mRNA specificity and regulation of 3′-end processing. 相似文献
65.
66.
Simultaneous saccharification and fermentation of straw to ethanol using the thermotolerant yeast strain Kluyveromyces marxianus imb3 总被引:1,自引:0,他引:1
The thermotolerant, ethanol-producing yeast strain Kluyveromyces marxianus IMB3 was grown at 45°C on media containing 2, 4 and 6 % (w/v) pulverized barley straw and supplemented with 2% (v/v) cellulase. Maximum ethanol concentrations produced were 2, 3 and 3.6g/l, respectively. When the pulverized straw was replaced by NaOH pretreated straw (at 2, 4 and 6% (w/v); based on original untreated straw), ethanol concentrations increased to maxima of 3.9, 8, and 12g/l, respectively. The ethanol yields amount to 20g ethanol from 100g of straw. 相似文献
67.
Evolutionary relatedness of some primate models of Plasmodium 总被引:1,自引:0,他引:1
Primate--and, specifically, monkey--malaria infections are commonly used
for understanding the pathology of and immune response to the human disease
because they are thought to resemble most closely the host-parasite
relationship found in humans. Plasmodium cynomolgi is used extensively as a
model for the human parasite, P. vivax, and P. knowlesi is used primarily
as a model for the development of erythrocytic-stage vaccines. Both of
these simian parasites can naturally infect man, resulting in mildly
symptomatic episodes of the disease. The phylogenetic relationship between
these two simian parasites and previously characterized Plasmodium species,
including P. vivax, was examined by comparison of the asexually expressed
small- subunit ribosomal RNA genes. Our analysis confirmed that P. vivax is
most closely related to P. cynomolgi and that it remains an appropriate
model of the human pathogen. Furthermore, with P. knowlesi and P. fragile,
these two species form a group of closely related species, distant from
other Plasmodium species. What is considered to be the most ancient of the
human malaria pathogens, P. malariae, was also included in the analysis and
does not group at all with other simian or human parasites.
相似文献
68.
Evolution and phylogenetic information content of the ITS-1 region in the tiger beetle Cicindela dorsalis 总被引:6,自引:0,他引:6
Sequence divergence in the internal transcribed spacer region 1 (ITS-1) of
the ribosomal DNA locus was assessed in subspecies of the coastal North
American tiger beetle, Cicindela dorsalis. The spacer region was amplified
using the polymerase chain reaction and cloned for sequencing. Of a total
of 50 clones obtained from 12 specimens, 42 clones were different in at
least one nucleotide position. In a parsimony analysis of these sequences,
the main phylogenetic distinction was found to separate sequences from the
Gulf of Mexico and the Atlantic Ocean. Within these two assemblages
phylogenetic resolution was low, and the variation within individuals was
almost as high as the variation within the entire lineage. The pattern of
sequence variation suggests the existence of two forms of the ITS-1 that
are maintained on different chromosomes. Polymorphisms of limited
geographical distribution could be detected, and 41 additional clones were
partly sequenced, to assess the geographic distribution of these
polymorphisms in more detail. In a population aggregation analysis, the
geographic pattern of ITS-1 distribution was basically congruent with that
obtained in earlier studies from mitochondrial DNA in the same C. dorsalis
populations.
相似文献
69.
Hypothesis: For any one time and place a ‘functional signature’ can be derived for a sample of herbaceous vegetation in a way that concisely represents the balance between the different clusters of functional attributes that are present among component species. Methods: We developed a spreadsheet‐based tool for calculating functional signatures within the context of the C‐S‐R system of plant functional types. We used the tool to calculate and compare signatures for specimen British vegetation samples which differed in management regime and location in time. Conclusion: The integrative power of the ‘C‐S‐R signature’ is useful in comparative studies involving widely differing samples. Movements in the signature can be used to indicate degree of resistance, resilience, eutrophication and dereliction. Systems of plant functional types other than C‐S‐R might also be approached in this way. Availability: The tool can be downloaded free of charge from the first author's web pages or from the journal's electronic archive. 相似文献
70.