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Desiree C. Petersen Ondrej Libiger Elizabeth A. Tindall Rae-Anne Hardie Linda I. Hannick Richard H. Glashoff Mitali Mukerji Indian Genome Variation Consortium Pedro Fernandez Wilfrid Haacke Nicholas J. Schork Vanessa M. Hayes 《PLoS genetics》2013,9(3)
Within-population genetic diversity is greatest within Africa, while between-population genetic diversity is directly proportional to geographic distance. The most divergent contemporary human populations include the click-speaking forager peoples of southern Africa, broadly defined as Khoesan. Both intra- (Bantu expansion) and inter-continental migration (European-driven colonization) have resulted in complex patterns of admixture between ancient geographically isolated Khoesan and more recently diverged populations. Using gender-specific analysis and almost 1 million autosomal markers, we determine the significance of estimated ancestral contributions that have shaped five contemporary southern African populations in a cohort of 103 individuals. Limited by lack of available data for homogenous Khoesan representation, we identify the Ju/''hoan (n = 19) as a distinct early diverging human lineage with little to no significant non-Khoesan contribution. In contrast to the Ju/''hoan, we identify ancient signatures of Khoesan and Bantu unions resulting in significant Khoesan- and Bantu-derived contributions to the Southern Bantu amaXhosa (n = 15) and Khoesan !Xun (n = 14), respectively. Our data further suggests that contemporary !Xun represent distinct Khoesan prehistories. Khoesan assimilation with European settlement at the most southern tip of Africa resulted in significant ancestral Khoesan contributions to the Coloured (n = 25) and Baster (n = 30) populations. The latter populations were further impacted by 170 years of East Indian slave trade and intra-continental migrations resulting in a complex pattern of genetic variation (admixture). The populations of southern Africa provide a unique opportunity to investigate the genomic variability from some of the oldest human lineages to the implications of complex admixture patterns including ancient and recently diverged human lineages. 相似文献
193.
The Cambrian Period, primarily known for animal life diversifying, experienced global extinctions. Pulses of extinction in Cambrian Series 2 are exemplified by the disappearance of archaeocyath sponges and olenelline and redlichiid trilobites. However, the effect of such extinctions on outer shelf organisms, as typify Burgess Shale‐type (BST) deposits, remains relatively unknown. The phylogeny of naraoiid arthropods, represented in BST deposits globally, has consequently been reconstructed from either side of the Series 2 – Miaolingian extinction event to evaluate the response of offshore marine organisms to Cambrian environmental perturbation. As soft anatomy is known for only a subset of naraoiid species, exoskeletal morphology has proven important. Misszhouia and Naraoia (Naraoia) are distinguished morphometrically by posterior shield length/width and anterior shield length/posterior shield length. Morphometry has also been used to strengthen the identification of some cryptic naraoiid species and revise stratigraphic ranges. A revised naraoiid phylogeny reveals Misszhouia as a monophyletic subgenus, the former genus Pseudonaraoia nests within Naraoia and is placed in synonymy, and the systematic position and status of the Subfamily Liwiinae are sensitive to character weighting. Ten species of Naraoiidae range across the Series 2 – Miaolingian boundary, all naraoiid lineages originating during the main BST window. The persistence of outer shelf naraoiids throughout the Series 2 extinctions suggests that deeper offshore marine environments were resilient to extinction during periods of environmental stress. This study provides novel empirical support for the asylum of BST communities, which may contribute to the taxonomic longevity and widespread geographic distribution of taxa in these biotas. 相似文献
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Wilfrid Oakley 《BMJ (Clinical research ed.)》1973,3(5881):636-637
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Joost H. Smid Lapo Mughini Gras Albert G. de Boer Nigel P. French Arie H. Havelaar Jaap A. Wagenaar Wilfrid van Pelt 《PloS one》2013,8(2)
In this study, 1208 Campylobacter jejuni and C. coli isolates from humans and 400 isolates from chicken, collected in two separate periods over 12 years in The Netherlands, were typed using multilocus sequence typing (MLST). Statistical evidence was found for a shift of ST frequencies in human isolates over time. The human MLST data were also compared to published data from other countries to determine geographical variation. Because only MLST typed data from chicken, taken from the same time point and spatial location, were available in addition to the human data, MLST datasets for other Campylobacter reservoirs from selected countries were used. The selection was based on the degree of similarity of the human isolates between countries. The main aim of this study was to better understand the consequences of using non-local or non-recent MLST data for attributing domestically acquired human Campylobacter infections to specific sources of origin when applying the asymmetric island model for source attribution. In addition, a power-analysis was done to find the minimum number of source isolates needed to perform source attribution using an asymmetric island model. This study showed that using source data from other countries can have a significant biasing effect on the attribution results so it is important to carefully select data if the available local data lack in quality and/or quantity. Methods aimed at reducing this bias were proposed. 相似文献
200.
Brigitte A. van Cleef Erwin J. M. Verkade Mireille W. Wulf Anton G. Buiting Andreas Voss Xander W. Huijsdens Wilfrid van Pelt Mick N. Mulders Jan A. Kluytmans 《PloS one》2010,5(2)