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1.

Background  

Populations of the Oriental White-backed Vulture (Gyps bengalensis) have declined by over 95% within the past decade. This decline is largely due to incidental consumption of the non-steroidal anti-inflammatory veterinary pharmaceutical diclofenac, commonly used to treat domestic livestock. The conservation status of other Gyps vultures in southern Asia is also of immediate concern, given the lack of knowledge regarding status of their populations and the continuing existence of taxonomic uncertainties. In this study, we assess phylogenetic relationships for all recognized species and the majority of subspecies within the genus Gyps. The continuing veterinary use of diclofenac is an unknown but potential risk to related species with similar feeding habits to Gyps bengalensis. Therefore, an accurate assessment of the phylogenetic relationships among Gyps vultures should aid in their conservation by clarifying taxonomic uncertainties, and enabling inference of their respective relatedness to susceptible G. bengalensis.  相似文献   
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In the preceding paper [Havel, H. A., Kauffman, E. W., Plaisted, S. M., & Brems, D. N. (1986) Biochemistry (preceding paper in this issue)], an associated intermediate was shown to be highly populated during the equilibrium denaturation of bovine growth hormone. In this paper, we describe its partial characterization and propose a mechanism for association. The associated equilibrium intermediate is populated under conditions that induce partial denaturation and at protein concentrations greater than 0.2 mg/mL. The remaining nativelike helical structure present in the partially denatured species is implicated in the mechanism of association as demonstrated by similar concentration dependencies and thermal stabilities of the helix and the associated equilibrium intermediate. Furthermore, it is suggested that a putative amphiphilic helix from residues 110-127 plays a critical role in the association as demonstrated by a diminution of the associated equilibrium intermediate when mixed with the peptide fragment 96-133. A model is proposed to account for these results in which partial denaturation exposes the segment of the protein corresponding to the hydrophobic face of the putative amphiphilic helix 110-127. This metastable form is the species from which association occurs. Association is stabilized by the hydrophobic interactions resulting from intermolecular packing of the lipophilic faces of the helices. The implications of these results to protein folding studies are described.  相似文献   
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alpha 1-Proteinase inhibitor (alpha 1-PI), a member of the serine proteinase inhibitor superfamily, has a primary role in controlling neutrophil elastase activity within the mammalian circulation. Several studies have indicated that the reactive center region of alpha 1-PI, the amino acid sequence of which is critical to recognition of and binding to target proteinases, is highly divergent within and among species. This appears to be a consequence of accelerated rates of evolution that may have been driven by positive Darwinian selection. In order to examine this and other features of alpha 1-PI evolution in more detail, we have isolated and sequenced cDNAs representing alpha 1- PI mRNAs of the mouse species Mus saxicola and Mus minutoides and have compared these with a number of other mammalian alpha 1-PI mRNAs. Relative to other mammalian mRNAs, the extent of nonsynonymous substitution is generally high throughout the alpha 1-PI mRNA molecule, indicating greater overall rates of amino acid substitution. Within and among mouse species, the 5'-half of the mRNA, but not the 3'-half, has been homogenized by concerted evolution. Finally, the reactive center is under diversifying or positive Darwinian selection in murid rodents (rats, mice) and guinea pigs yet is under purifying selection in primates and artiodactyls. The significance of these findings to alpha 1-PI function and the possible selective forces driving evolution of serpins in general are discussed.   相似文献   
6.
QTL analysis of trichome-mediated insect resistance in potato   总被引:10,自引:0,他引:10  
Genetic mapping of several components of a complex type of insect resistance has been undertaken as a means toward more efficient use of the valuable characteristics of a wild relative of potato. RFLP maps constructed on interspecific diploid progenies of Solanum tuberosum × S. berthaultii were used in conjunction with morphological, biochemical and biological phenotyping to identify quantitative trait loci (QTLs) contributing to trichome-mediated insect resistance. By superimposing QTL data for a wide range of phenotypes including biochemical assays, correlative and direct screens for insect resistance, and adaptation to the target environment on the genetic maps, we have addressed the organization, action and interaction of genes controlling the resistance mechanism. The outcome contributes to an understanding of the association between component traits and between desirable and undesirable features of the donor species generated in an applied breeding program. Research is proceeding toward the development of selectable markers for the introgression and transfer of this resistance among potato gene pools.  相似文献   
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It has been theorized that in cross-pollinated polyploid species hybrid vigor is maximized by the frequent occurrence of more than two alleles per chromosomal locus. In polyploid crops this condition of maximum heterozygosity has been reported to be associated with increased yield and optimum field performance. We report herein the first direct test of the maximum heterozygosity hypothesis. Molecular markers were used to examine the association between maximum heterozygosity and several components of yield in three different populations of tetraploid potatoes. The results indicate that the value of maximum heterozygosity is not universal but dependent on the genetic background of the material under evaluation. In a cross between adapted breeding lines, homozygosity was negatively correlated with tuber yield, and maximum heterozygosity was positively correlated with the proportion of tuber yield in the large-size fraction. In contrast, in crosses between adapted and unadapted parents, maximum heterozygosity had no detectable effect on any character. Quantitative trait locus (QTL) analysis of the three populations reveals that, regardless of the genetic background, additive genetic effects are more strongly correlated with the components of yield than are any measures of heterozygosity and that some common QTLs may be influencing yield in all three populations.  相似文献   
8.
Patterns of mitochondrial DNA (mtDNA) variation were examined in 133 mole-rats constituting all four chromosomal species (2n = 52, 2n = 54, 2n = 58, and 2n = 60) of the Spalax ehrenbergi superspecies in Israel, as well as the peripheral isolates of 2n = 60. In the main range of the complex, a total of 28 mtDNA haplotypes were found in 64 mole-rats, with most haplotypes being unique to either a single chromosomal species or population. mtDNA divergence increased from low to high diploid number in a north-to-south direction in Israel. Overall levels of mtDNA diversity were unexpectedly the highest in the 2n = 60, the youngest species of the complex. The mtDNA haplotypes can be separated into two major groups, 2n = 52-54 and 2n = 58-60, and a phylogenetic analysis for each group revealed evidence of a few haplotypes not sorted by diploid number. The overall patterns of mtDNA divergence seen within and among the four chromosomal species are consistent with the parapatric mode of speciation as suggested from previous studies of allozyme and DNA hybridization. In a separate data set the patterns of mtDNA variation were examined across the main geographic range and across peripheral semi-isolates and isolates of the 2n = 60 chromosomal species. Fifteen haplotypes were found in 69 mole-rats. High levels of mtDNA diversity characterized the main range, semi-isolated, and even some desert isolated populations. The peripheral isolates contain much mtDNA diversity, including novel haplotypes.   相似文献   
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Arginine decarboxylase (ADC) is an important enzyme in the production of putrescine and polyamines in plants. It is encoded by a single or low-copy nuclear gene that lacks introns in sequences studied to date. The rate of Adc amino acid sequence evolution is similar to that of ndhF for the angiosperm family studied. Highly conserved regions provide several target sites for PCR priming and sequencing and aid in nucleotide and amino acid sequence alignment across a range of taxonomic levels, while a variable region provides an increased number of potentially informative characters relative to ndhF for the taxa surveyed. The utility of the Adc gene in plant molecular systematic studies is demonstrated by analysis of its partial nucleotide sequences obtained from 13 representatives of Brassicaceae and 3 outgroup taxa, 2 from the mustard oil clade (order Capparales) and 1 from the related order Malvales. Two copies of the Adc gene, Adc1 and Adc2, are found in all members of the Brassicaceae studied to data except the basal genus Aethionema. The resulting Adc gene tree provides robust phylogenetic data regarding relationships within the complex mustard family, as well as independent support for proposed tribal realignments based on other molecular data sets such as those from chloroplast DNA.   相似文献   
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