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排序方式: 共有312条查询结果,搜索用时 15 毫秒
1.
Immunochemical and amino-terminal sequence comparison of two cytoadhesins indicates they contain similar or identical beta subunits and distinct alpha subunits 总被引:26,自引:0,他引:26
M H Ginsberg J Loftus J J Ryckwaert M Pierschbacher R Pytela E Ruoslahti E F Plow 《The Journal of biological chemistry》1987,262(12):5437-5440
Platelet membrane glycoprotein (GP) IIb-IIIa is functionally and antigenically related to proteins present on many cell types, suggesting that it is a member of the proposed cytoadhesin family of membrane proteins. We have compared the purified tissue vitronectin receptor (VnR) with GP IIb-IIIa. Anti-VnR immunoprecipitated GP IIb-IIIa and a related endothelial cell protein. In immunoblots, GP IIIa reacted with anti-VnR and the beta subunit of the VnR reacted with poly and monoclonal anti-GP IIIa. In contrast, the alpha subunit of the VnR failed to react either with a polyclonal anti-GP IIb or with monoclonal anti-GP IIb. Furthermore, the amino-terminal sequence of GP IIIa and the beta subunit of VnR were identical at determined residues while the alpha subunit and the GP IIb were different, but showed 33% identity. These data indicate the identity or close homology of GP IIIa and the beta subunit of the VnR. In contrast, the alpha subunit and GP IIb are distinct polypeptides which may be homologous. Since GP IIb-IIIa and the VnR differ in ligand recognition specificity, the data also suggest that this specificity may be governed by the alpha subunit of cytoadhesins. 相似文献
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Occupancy of an adhesive glycoprotein receptor modulates expression of an antigenic site involved in cell adhesion 总被引:19,自引:0,他引:19
A L Frelinger S C Lam E F Plow M A Smith J C Loftus M H Ginsberg 《The Journal of biological chemistry》1988,263(25):12397-12402
Binding of ligands that contain Arg-Gly-Asp to adhesion receptors induces cell spreading and aggregation and alters gene expression, possibly due to conformational changes within occupied adhesion receptors. PMI-1 is a monoclonal antibody which reacts with the platelet fibrinogen receptor, glycoprotein IIb-IIIa, and reports such a conformational change. ADP stimulation of platelets results in a fibrinogen-dependent increase in binding of the PMI-1 antibody. Peptides containing Arg-Gly-Asp also reversibly increase the binding of this antibody to cells and to purified glycoprotein IIb-IIIa. The PMI-1 antibody inhibits platelet adhesion and spreading on certain substrata (Shadle, P. J., Ginsberg, M. H., Plow, E. F., and Barondes, S. H. (1984) J. Cell Biol. 99, 2056-2060); thus this occupancy-modulated site may participate in adhesive function. 相似文献
4.
A comparative description of mitochondrial DNA differentiation in selected avian and other vertebrate genera 总被引:14,自引:1,他引:13
Levels of mitochondrial DNA (mtDNA) sequence divergence between species
within each of several avian (Anas, Aythya, Dendroica, Melospiza, and
Zonotrichia) and nonavian (Lepomis and Hyla) vertebrate genera were
compared. An analysis of digestion profiles generated by 13-18 restriction
endonucleases indicates little overlap in magnitude of mtDNA divergence for
the avian versus nonavian taxa examined. In 55 interspecific comparisons
among the avian congeners, the fraction of identical fragment lengths (F)
ranged from 0.26 to 0.96 (F = 0.46), and, given certain assumptions, these
translate into estimates of nucleotide sequence divergence (p) ranging from
0.007 to 0.088; in 46 comparisons among the fish and amphibian congeners, F
values ranged from 0.00 to 0.36 (F = 0.09), yielding estimates of P greater
than 0.070. The small mtDNA distances among avian congeners are associated
with protein-electrophoretic distances (D values) less than approximately
0.2, while the mtDNA distances among assayed fish and amphibian congeners
are associated with D values usually greater than 0.4. Since the
conservative pattern of protein differentiation previously reported for
many avian versus nonavian taxa now appears to be paralleled by a
conservative pattern of mtDNA divergence, it seems increasingly likely that
many avian species have shared more recent common ancestors than have their
nonavian taxonomic counterparts. However, estimates of avian divergence
times derived from mtDNA- and protein-calibrated clocks cannot readily be
reconciled with some published dates based on limited fossil remains. If
the earlier paleontological interpretations are valid, then protein and
mtDNA evolution must be somewhat decelerated in birds. The empirical and
conceptual issues raised by these findings are highly analogous to those in
the long-standing debate about rates of molecular evolution and times of
separation of ancestral hominids from African apes.
相似文献
5.
Methods for computing the standard errors of branching points in an evolutionary tree and their application to molecular data from humans and apes 总被引:23,自引:2,他引:21
Statistical methods for computing the standard errors of the branching
points of an evolutionary tree are developed. These methods are for the
unweighted pair-group method-determined (UPGMA) trees reconstructed from
molecular data such as amino acid sequences, nucleotide sequences,
restriction-sites data, and electrophoretic distances. They were applied to
data for the human, chimpanzee, gorilla, orangutan, and gibbon species.
Among the four different sets of data used, DNA sequences for an
895-nucleotide segment of mitochondrial DNA (Brown et al. 1982) gave the
most reliable tree, whereas electrophoretic data (Bruce and Ayala 1979)
gave the least reliable one. The DNA sequence data suggested that the
chimpanzee is the closest and that the gorilla is the next closest to the
human species. The orangutan and gibbon are more distantly related to man
than is the gorilla. This topology of the tree is in agreement with that
for the tree obtained from chromosomal studies and DNA-hybridization
experiments. However, the difference between the branching point for the
human and the chimpanzee species and that for the gorilla species and the
human-chimpanzee group is not statistically significant. In addition to
this analysis, various factors that affect the accuracy of an estimated
tree are discussed.
相似文献
6.
Anonymous nuclear DNA markers in the American oyster and their implications for the heterozygote deficiency phenomenon in marine bivalves 总被引:4,自引:0,他引:4
A puzzling population-genetic phenomenon widely reported in allozyme
surveys of marine bivalves is the occurrence of heterozygote deficits
relative to Hardy-Weinberg expectations. Possible explanations for this
pattern are categorized with respect to whether the effects should be
confined to protein-level assays or are genomically pervasive and expected
to be registered in both protein- and DNA-level assays. Anonymous nuclear
DNA markers from the American oyster were employed to reexamine the
phenomenon. In assays based on the polymerase chain reaction (PCR), two
DNA-level processes were encountered that can lead to artifactual genotypic
scorings: (a) differential amplification of alleles at a target locus and
(b) amplification from multiple paralogous loci. We describe symptoms of
these complications and prescribe methods that should generally help to
ameliorate them. When artifactual scorings at two anonymous DNA loci in the
American oyster were corrected, Hardy-Weinberg deviations registered in
preliminary population assays decreased to nonsignificant values.
Implications of these findings for the heterozygote-deficit phenomenon in
marine bivalves, and for the general development and use of PCR-based
assays, are discussed.
相似文献
7.
A YAC contig encompassing the Treacher Collins syndrome critical region at 5q31.3-32. 总被引:1,自引:1,他引:0
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J. Dixon A. J. Gladwin S. K. Loftus J. H. Riley R. Perveen J. J. Wasmuth R. Anand M. J. Dixon 《American journal of human genetics》1994,55(2):372-378
Treacher Collins syndrome (TCOF1) is an autosomal dominant disorder of craniofacial development the features of which include conductive hearing loss and cleft palate. Previous studies have localized the TCOF1 locus between D5S519 (proximal) and SPARC (distal), a region of 22 centirays as estimated by radiation hybrid mapping. In the current investigation we have created a contig across the TCOF1 critical region, using YAC clones. Isolation of a novel short tandem repeat polymorphism corresponding to the end of one of the YACs has allowed us to reduce the size of the critical region to approximately 840 kb, which has been covered with three nonchimeric YACs. Restriction mapping has revealed that the region contains a high density of clustered rare-cutter restriction sites, suggesting that it may contain a number of different genes. The results of the present investigation have further allowed us to confirm that the RPS14 locus lies proximal to the critical region and can thereby be excluded from a role in the pathogenesis of TCOF1, while ANX6 lies within the TCOF1 critical region and remains a potential candidate for the mutated gene. 相似文献
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10.
A highly conserved nuclear gene for low-level phylogenetics: elongation factor-1 alpha recovers morphology-based tree for heliothine moths 总被引:8,自引:2,他引:6
Cho S; Mitchell A; Regier JC; Mitter C; Poole RW; Friedlander TP; Zhao S 《Molecular biology and evolution》1995,12(4):650-656
Molecular systematists need increased access to nuclear genes. Highly
conserved, low copy number protein-encoding nuclear genes have attractive
features for phylogenetic inference but have heretofore been applied mostly
to very ancient divergences. By virtue of their synonymous substitutions,
such genes should contain a wealth of information about lower-level
taxonomic relationships as well, with the advantage that amino acid
conservatism makes both alignment and primer definition straightforward. We
tested this postulate for the elongation factor-1 alpha (EF-1 alpha) gene
in the noctuid moth subfamily Heliothinae, which has probably diversified
since the middle Tertiary. We sequenced 1,240 bp in 18 taxa representing
heliothine groupings strongly supported by previous morphological and
allozyme studies. The single most parsimonious gene tree and the
neighbor-joining tree for all nucleotides show almost complete concordance
with the morphological tree. Homoplasy and pairwise divergence levels are
low, transition/transversion ratios are high, and phylogenetic information
is spread evenly across gene regions. The EF-1 alpha gene and presumably
other highly conserved genes hold much promise for phylogenetics of
Tertiary age eukaryote groups.
相似文献