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排序方式: 共有170条查询结果,搜索用时 15 毫秒
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Human immunodeficiency virus pseudotypes with expanded cellular and species tropism. 总被引:17,自引:17,他引:0
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D H Spector E Wade D A Wright V Koval C Clark D Jaquish S A Spector 《Journal of virology》1990,64(5):2298-2308
One mechanism for expanding the cellular tropism of a virus is through the formation of phenotypically mixed particles or pseudotypes, a process commonly occurring during viral assembly in cells infected with two or more viruses. We report here that dual infection of cells with human immunodeficiency virus (HIV) and a murine amphotropic retrovirus leads to the production of HIV pseudotypes that have acquired the host range of the amphotropic retrovirus and are capable of infecting not only CD4- human cells but also mouse cells. The replication of the HIV pseudotypes in the various CD4- cells was determined by measuring the appearance of HIV antigens in the supernatants, by cocultivation of CD4+ CEM cells with the infected CD4- cells, and in some cases by assaying the culture supernatants directly for infectious virus. Of the cells tested, human foreskin fibroblasts were the best host cells, and by in situ cytohybridization, we were able to document that all cells in the culture were infected. In addition, the temporal appearance of HIV-specific proteins in the HIV pseudotype-infected fibroblasts was similar to that seen in CD4+ CEM cells. If the human fibroblasts were first infected with the amphotropic retrovirus, they demonstrated the property of superinfection exclusion and were resistant to subsequent infection by the HIV pseudotype. In other cell lines, including the human glioblastoma-derived cell line U373MG, HeLa cells, BALB/c mouse embryo cells, and SC-1 wild mouse cells, although the HIV pseudotype infection appeared to be less efficient, substantial amounts of HIV were nevertheless produced. These results indicate that the HIV (amphotropic retrovirus) pseudotypes may be useful for studying the molecular biology of HIV infections in a wide range of cells. 相似文献
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Patterns of genetic variation in gas-exchange physiology were analyzed in a 15-year-old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) plantation that contains 25 populations grown from seed collected from across the natural distribution of the species. Seed was collected from 33°30 to 53°12 north latitude and from 170 m to 2930 m above sea level, and from the coastal and interior (Rocky Mountain) varieties of the species. Carbon isotope discrimination () ranged from 19.70() to 22.43() and was closely related to geographic location of the seed source. The coastal variety (20.50 (SE=0.21)) was not significantly different from the interior variety (20.91 (0.15)). Instead, most variation was found within the interior variety; populations from the southern Rockies had the highest discrimination (21.53 (0.20)) (lowest water-use efficiency). Carbon isotope discrimination (), stomatal conductance to water vapor (g), the ratio of intercellular to ambient CO2 concentration (ci/ca), and intrinsic water-use efficiency (A/g) were all correlated with altitude of origin (r=0.76, 0.73, 0.74, and –0.63 respectively); all were statistically significant at the 0.01 level. The same variables were correlated with both height and diameter at age 15 (all at P0.0005). Observed patterns in the common garden did not conform to our expectation of higher WUE, measured by both A/g and , in trees from the drier habitats of the interior, nor did they agree with published in situ observations of decreasing g and with altitude. The genetic effect opposes the altitudinal one, leading to some degree of homeostasis in physiological characteri tics in situ. 相似文献
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Improved white spruce (Picea glauca) genome assemblies and annotation of large gene families of conifer terpenoid and phenolic defense metabolism
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René L. Warren Christopher I. Keeling Macaire Man Saint Yuen Anthony Raymond Greg A. Taylor Benjamin P. Vandervalk Hamid Mohamadi Daniel Paulino Readman Chiu Shaun D. Jackman Gordon Robertson Chen Yang Brian Boyle Margarete Hoffmann Detlef Weigel David R. Nelson Carol Ritland Nathalie Isabel Barry Jaquish Alvin Yanchuk Jean Bousquet Steven J. M. Jones John MacKay Inanc Birol Joerg Bohlmann 《The Plant journal : for cell and molecular biology》2015,83(2):189-212
8.
Range-wide chloroplast and mitochondrial DNA imprints reveal multiple lineages and complex biogeographic history for Douglas-fir 总被引:1,自引:0,他引:1
Xiao-Xin Wei Jean Beaulieu Damase P. Khasa Jes��s Vargas-Hern��ndez Javier L��pez-Upton Barry Jaquish Jean Bousquet 《Tree Genetics & Genomes》2011,7(5):1025-1040
The contemporary genetic structure of species offers key imprints of how organisms responded to past geological and climatic
events, which have played a crucial role in shaping the current geographical distribution of north-temperate organisms. In
this study, range-wide patterns of genetic variation were examined in Douglas-fir (Pseudotsuga menziesii), a dominant forest tree species distributed from Mexico to British Columbia in western North America. Two organelle DNA
markers with contrasting modes of inheritance were genotyped for 613 individuals from 44 populations. Two mitotypes and 42
chlorotypes were recovered in this survey. Both genomes showed significant population subdivision, indicative of limited gene
flow through seeds and pollen. Three distinct cpDNA lineages corresponding to the Pacific Coast, the Rocky Mountains, and
Mexico were observed. The split time of the two lineages from the Rockies lineage was dated back to 8.5 million years (Ma).
The most recent common ancestors of Mexican and coastal populations were estimated at 3.2 and 4.8 Ma, respectively. The northern
populations of once glaciated regions were characterized by a high level of genetic diversity, indicating a large zone of
contact between ancestral lineages. A possible northern refugium was also inferred. The Mexican lineage, which appeared established
by southward migration from the Rockies lineage, was characterized by the lowest genetic diversity but highest population
differentiation. These results suggest that the effects of Quaternary climatic oscillations on the population dynamics and
genetic diversity of Douglas-fir varied substantially across the latitudinal section. The results emphasize the pressing need
for the conservation of Mexican Douglas-fir. 相似文献
9.
Background
Distance-based methods are popular for reconstructing evolutionary trees thanks to their speed and generality. A number of methods exist for estimating distances from sequence alignments, which often involves some sort of correction for multiple substitutions. The problem is to accurately estimate the number of true substitutions given an observed alignment. So far, the most accurate protein distance estimators have looked for the optimal matrix in a series of transition probability matrices, e.g. the Dayhoff series. The evolutionary distance between two aligned sequences is here estimated as the evolutionary distance of the optimal matrix. The optimal matrix can be found either by an iterative search for the Maximum Likelihood matrix, or by integration to find the Expected Distance. As a consequence, these methods are more complex to implement and computationally heavier than correction-based methods. Another problem is that the result may vary substantially depending on the evolutionary model used for the matrices. An ideal distance estimator should produce consistent and accurate distances independent of the evolutionary model used. 相似文献10.