全文获取类型
收费全文 | 91篇 |
免费 | 14篇 |
出版年
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 3篇 |
2015年 | 4篇 |
2014年 | 9篇 |
2013年 | 5篇 |
2012年 | 4篇 |
2011年 | 6篇 |
2010年 | 4篇 |
2009年 | 3篇 |
2008年 | 2篇 |
2007年 | 9篇 |
2006年 | 7篇 |
2005年 | 2篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 3篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1977年 | 1篇 |
1973年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有105条查询结果,搜索用时 31 毫秒
61.
The southern brown bandicoot (Isoodon obesulus) was once widely distributed throughout coastal regions of Australia, however, populations have now become fragmented and the number of individuals are declining rapidly. As a result, this species is now classified as endangered in New South Wales and requires management. We have developed eight microsatellite markers to investigate levels of genetic variation and subdivision among these isolated populations. These microsatellite markers show levels of variability ranging from four to eight alleles and observed heterozygosities of 0.353–0.938. These microsatellite markers are also suitable for similar population studies on other related marsupials. 相似文献
62.
Anja Hilbert Sabrina Baldofski Markus Zenger Bernd L?we Anette Kersting Elmar Braehler 《PloS one》2014,9(1)
Objective
Internalizing the pervasive weight bias commonly directed towards individuals with overweight and obesity, co-occurs with increased psychopathology and impaired quality of life. This study sought to establish population norms and psychometric properties of the most widely used self-report questionnaire, the Weight Bias Internalization Scale (WBIS), in a representative community sample.Design and Methods
In a survey of the German population, N = 1158 individuals with overweight and obesity were assessed with the WBIS and self-report measures for convergent validation.Results
Item analysis revealed favorable item-total correlation of all but one WBIS item. With this item removed, item homogeneity and internal consistency were excellent. The one-factor structure of the WBIS was confirmed using confirmatory factor analysis. Convergent validity was shown through significant associations with measures of depressive and somatoform symptoms. The WBIS contributed to the explanation of variance in depressive and somatoform symptoms over and above body mass index. Higher WBIS scores were found in women than in men, in individuals with obesity than in individuals with overweight, and in those with lower education or income than those with higher education or income. Sex-specific norms were provided.Conclusions
The results showed good psychometric properties of the WBIS after removal of one item. Future research is warranted on further indicators of reliability and validity, for example, retest reliability, sensitivity to change, and prognostic validity. 相似文献63.
Effect of medium hypertonicity on reovirus translation rates. An application of kinetic modeling in vivo 总被引:1,自引:0,他引:1
Translation rates were determined for host and virus mRNAs in reovirus-infected SC-1 cells in hypertonic medium. The effect of low doses of cycloheximide on these translation rates was also measured. The results show that hypertonicity selectively stimulates viral translation relative to host translation. Moreover, in hypertonic medium, host translation is slightly stimulated by low doses of cycloheximide, whereas viral translation is markedly inhibited. This effect of cycloheximide is precisely the opposite to what was previously observed in isotonic media [Walden, W. E., Godefroy-Colburn, T., & Thach, R. E. (1981) J. Biol. Chem. 256, 11739-11746]. It is shown that both these effects of hypertonicity are predicted by the message competition/discrimination model previously described and thus provide support for the applicability of certain aspects of the model to translation rates in vivo. 相似文献
64.
Roel GW Verhaak Frank JT Staal Peter JM Valk Bob Lowenberg Marcel JT Reinders Dick de Ridder 《BMC bioinformatics》2006,7(1):105-15
Background
Intensity values measured by Affymetrix microarrays have to be both normalized, to be able to compare different microarrays by removing non-biological variation, and summarized, generating the final probe set expression values. Various pre-processing techniques, such as dChip, GCRMA, RMA and MAS have been developed for this purpose. This study assesses the effect of applying different pre-processing methods on the results of analyses of large Affymetrix datasets. By focusing on practical applications of microarray-based research, this study provides insight into the relevance of pre-processing procedures to biology-oriented researchers. 相似文献65.
Stow A Zenger K Briscoe D Gillings M Peddemors V Otway N Harcourt R 《Biology letters》2006,2(2):308-311
Anthropogenic impacts are believed to be the primary threats to the eastern Australian population of grey nurse sharks (Carcharias taurus), which is listed as critically endangered, and the most threatened population globally. Analyses of 235 polymorphic amplified fragment length polymorphisms (AFLP) loci and 700 base pairs of mitochondrial DNA control region provide the first account of genetic variation and geographical partitioning (east and west coasts of Australia, South Africa) in C. taurus. Assignment tests, analysis of relatedness and Fst values all indicate that the Australian populations are isolated from South Africa, with negligible migration between the east and west Australian coasts. There are significant differences in levels of genetic variation among regions. Australian C. taurus, particularly the eastern population, has significantly less AFLP variation than the other sampling localities. Further, the eastern Australian sharks possess only a single mitochondrial haplotype, also suggesting a small number of founding individuals. Therefore, historical, rather than anthropogenic processes most likely account for their depauperate genetic variation. These findings have implications for the viability of the eastern Australian population of grey nurse sharks. 相似文献
66.
DNA-protein cross-links are generated by both endogenous and exogenous DNA damaging agents, as intermediates during normal DNA metabolism, and during abortive base excision repair. Cross-links are relatively common lesions that are lethal when they block progression of DNA polymerases. DNA-protein cross-links may be broadly categorized into four groups by the DNA and protein chemistries near the cross-link and by the source of the cross-link: DNA-protein cross-links may be found (1) in nicked DNA at the 3' end of one strand (topo I), (2) in nicked DNA at the 5' end of one strand (pol beta), (3) at the 5' ends of both strands adjacent to nicks in close proximity (topo II; Spo 11), and (4) in one strand of duplex DNA (UV irradiation; bifunctional carcinogens and chemotherapeutic agents). Repair mechanisms are reasonably well-defined for groups 1 and 3, and suggested for groups 2 and 4. Our work is focused on the recognition and removal of DNA-protein cross-links in duplex DNA (group 4). 相似文献
67.
Effects of nucleotide sequence alignment on phylogeny estimation: a case study of 18S rDNAs of apicomplexa 总被引:13,自引:5,他引:8
The reconstruction of phylogenetic history is predicated on being able to
accurately establish hypotheses of character homology, which involves
sequence alignment for studies based on molecular sequence data. In an
empirical study investigating nucleotide sequence alignment, we inferred
phylogenetic trees for 43 species of the Apicomplexa and 3 of Dinozoa based
on complete small-subunit rDNA sequences, using six different
multiple-alignment procedures: manual alignment based on the secondary
structure of the 18S rRNA molecule, and automated similarity-based
alignment algorithms using the PileUp, ClustalW, TreeAlign, MALIGN, and SAM
computer programs. Trees were constructed using neighboring-joining,
weighted-parsimony, and maximum- likelihood methods. All of the multiple
sequence alignment procedures yielded the same basic structure for the
estimate of the phylogenetic relationship among the taxa, which presumably
represents the underlying phylogenetic signal. However, the placement of
many of the taxa was sensitive to the alignment procedure used; and the
different alignments produced trees that were on average more dissimilar
from each other than did the different tree-building methods used. The
multiple alignments from the different procedures varied greatly in length,
but aligned sequence length was not a good predictor of the similarity of
the resulting phylogenetic trees. We also systematically varied the gap
weights (the relative cost of inserting a new gap into a sequence or
extending an already-existing gap) for the ClustalW program, and this
produced alignments that were at least as different from each other as
those produced by the different alignment algorithms. Furthermore, there
was no combination of gap weights that produced the same tree as that from
the structure alignment, in spite of the fact that many of the alignments
were similar in length to the structure alignment. We also investigated the
phylogenetic information content of the helical and nonhelical regions of
the rDNA, and conclude that the helical regions are the most informative.
We therefore conclude that many of the literature disagreements concerning
the phylogeny of the Apicomplexa are probably based on differences in
sequence alignment strategies rather than differences in data or
tree-building methods.
相似文献
68.
Cross-hybridizing snake satellite, Drosophila, and mouse DNA sequences may have arisen independently 总被引:2,自引:0,他引:2
Previous reports have interpreted hybridization between snake satellite DNA
and DNA clones from a variety of distant taxonomic groups as evidence for
evolutionary conservation, which implies common ancestry (homology) and/or
convergence (analogy) to produce the cross- hybridizing sequences. We have
isolated 11 clones from a genomic library of Drosophila melanogaster, using
a cloned 2.5-kb snake satellite probe of known nucleotide sequence. We have
also analysed published sequence data from snakes, mice, and Drosophila.
These data show that (1) all of the cross-hybridization between the snake,
fly, and mouse clones can be accounted for by the presence of either of two
tandem repeats, [GATA]n and [GACA]n and (2) these tandem repeats are
organized differently among the different species. We find no evidence that
these sequences are homologous apart from the existence of the simple
repeat itself, although their divergence from a common ancestral sequence
cannot be ruled out. The sequences contain a variety of homogeneous
clusters of tandem repeats of CATA, GA, TA, and CA, as well as GATA and
GACA. We suggest that these motifs may have arisen by a self-accelerating
process involving slipped-strand mispairing of DNA. Homogeneity of the
clusters might simply be the result of a rate of accumulation of tandem
repeats that exceeds that of other mutations.
相似文献
69.
Structural comparison of fibroblast growth factor-specific heparan sulfates derived from a growing or differentiating neuroepithelial cell line 总被引:3,自引:1,他引:2
Brickman YG; Nurcombe V; Ford MD; Gallagher JT; Bartlett PF; Turnbull JE 《Glycobiology》1998,8(5):463-471
Heparan sulfate (HS) glycosaminoglycans are essential modulators of
fibroblast growth factor (FGF) activity both in vivo and in vitro, and
appear to act by cross-linking particular forms of FGF to appropriate FGF
receptors. We have recently isolated and characterized two separate HS
pools derived from immortalized embryonic day 10 mouse neuroepithelial 2.3D
cells: one from cells in log growth phase, which greatly potentiates the
activity of FGF-2, and the other from cells undergoing contact-inhibition
and differentiation, which preferentially activates FGF-1. These two pools
of HS have very similar functional activities to those species isolated
from primary neuroepithelial cells at corresponding stages of active
proliferation or differentiation. We present here a structural comparison
between these cell line HS species to establish the nature of the changes
that occur in the biosynthesis of HS. A combination of chemical and
enzymatic cleavage, low pressure chromatography and strong anion-exchange
HPLC were used to generate full chain models of each species. Overall, the
HS pools synthesized in the dividing cell line pools possessed less complex
sulfation than those derived from more differentiated, growth arrested
cells.
相似文献
70.
BACKGROUND: CD69 is a surrogate marker of T-cell responsiveness to mitogen and Ag stimulus and can be used as a measure of T-lymphocyte activation. Quantitative flow cytometric determination of CD69 expression on T lymphocytes has several advantages over traditional lymphocyte proliferation assays, but this method has not yet been standardized for clinical applications. METHODS: We qualified a commercially available assay using the manufacturer's procedures for measurement of T-cell response to a mitogen (PHA), superantigen (Staphylococcus endotoxin B; SEB) and Ca(2+) ionophore (phorbyl myristate acetate; PMA) with peripheral blood from healthy volunteers. Following this, we tested the usefulness of the assay in determining T-cell responses to PHA and SEB for six immunocompromised patients. RESULTS: Healthy volunteers showed 17-fold increases in T-cell CD69 Ab bound per cell (ABC) with PHA stimulation compared with the baseline. SEB was also an effective T-cell activating agent, increasing CD69 ABC by 5-fold, comparable with results obtained with PMA stimulation. PHA- and SEB-stimulated T-cell CD69 ABC for patients 100 days post-BM transplant were generally below 1 SD of that from healthy volunteers. SEB-stimulated T-cell CD69 expression was significantly depressed for CD8(+) T cells while CD4(+) T-cell responses to SEB were generally within 1 SD of the mean for healthy volunteers. DISCUSSION: These results suggest that quantitative measurement of CD69 surface expression by flow cytometry is a useful diagnostic tool for detailed assessment of T-lymphocyte and subset activation. 相似文献