全文获取类型
收费全文 | 309篇 |
免费 | 47篇 |
国内免费 | 14篇 |
出版年
2023年 | 12篇 |
2022年 | 11篇 |
2021年 | 12篇 |
2020年 | 24篇 |
2019年 | 23篇 |
2018年 | 17篇 |
2017年 | 22篇 |
2016年 | 22篇 |
2015年 | 14篇 |
2014年 | 17篇 |
2013年 | 19篇 |
2012年 | 21篇 |
2011年 | 16篇 |
2010年 | 15篇 |
2009年 | 16篇 |
2008年 | 13篇 |
2007年 | 16篇 |
2006年 | 8篇 |
2005年 | 10篇 |
2004年 | 6篇 |
2003年 | 6篇 |
2002年 | 9篇 |
2001年 | 6篇 |
2000年 | 2篇 |
1999年 | 7篇 |
1998年 | 2篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1989年 | 2篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1982年 | 1篇 |
排序方式: 共有370条查询结果,搜索用时 15 毫秒
21.
Anecdotal evidence from many hunter-gatherer societies suggests that successful hunters experience higher prestige and greater
reproductive success. Detailed quantitative data on these patterns are now available for five widely dispersed cases (Ache,
Hadza, !Kung, Lamalera, and Meriam) and indicate that better hunters exhibit higher age-corrected reproductive success than
other men in their social group. Leading explanations to account for this pattern are: (1) direct provisioning of hunters’
wives and offspring, (2) dyadic reciprocity, (3) indirect reciprocity, (4) costly signaling, and (5) phenotypic correlation.
I examine the qualitative and quantitative evidence bearing on these explanations and conclude that although none can be definitively
rejected, extensive and apparently unconditional sharing of large game somewhat weakens the first three explanations. The
costly signaling explanation has support in some cases, although the exact nature of the benefits gained from mating or allying
with or deferring to better hunters needs further study.
For comments on earlier drafts, I thank Monique Borgerhoff Mulder, Mike Gurven, Ray Hames, Kristen Hawkes, Kim Hill, Robert
Kelly, Frank Marlowe, John Patton, and Polly Wiessner. Rebecca Bliege Bird and Douglas W. Bird invited me to collaborate in
the Meriam research and (along with Del Passi of Mer) collected the data on Meriam demography. Geoff Kushnick and Matt Wimmer
ably assisted with coding and statistical analysis of these data.
Eric Alden Smith (PhD 1980, Cornell University) is a professor of anthropology at the University of Washington, Seattle. His
research interests include the links between production and reproduction, the ecology and evolution of collective action,
and politics in small-scale societies. He has conducted fieldwork among Inuit on Hudson Bay, Meriam in Torres Strait, and
Mardu Aborigines in the Australian Western Desert. 相似文献
22.
Agrawal R Chandrashekhar R Mishra AK Ramadevi J Sharma Y Aggarwal RK 《Journal of biosciences》2002,27(3):251-259
τ-Crystallin is a taxon-specific structural protein found in eye lenses. We present here the cloning and sequencing of complete
τ-crystallin cDNA from the embryonic lens ofCrocodylus palustris and establish it to be identical to the α-enolase gene from non-lenticular tissues. Quantitatively, the τ-crystallin was
found to be the least abundant crystallin of the crocodilian embryonic lenses. Crocodile τ-crystallin cDNA was isolated by
RT-PCR using primers designed from the only other reported sequence from duck and completed by 5′- and 3′-rapid amplification
of cDNA ends (RACE) using crocodile gene specific primers designed in the study. The complete τ-crystallin cDNA of crocodile
comprises 1305 bp long ORF and 92 and 409 bp long untranslated 5′- and 3′-ends respectively. Further, it was found to be identical
to its putative counterpart enzyme α-enolase, from brain, heart and gonad, suggesting both to be the product of the same gene.
The study thus provides the first report on cDNA sequence of τ-crystallin from a reptilian species and also re-confirms it
to be an example of the phenomenon of gene sharing as was demonstrated earlier in the case of peking duck. Moreover, the gene
lineage reconstruction analysis helps our understanding of the evolution of crocodilians and avian species. 相似文献
23.
Herbaceous species possess several mechanisms to compensate for tissue loss. For clonal herbaceous species, clonal integration may be an additional mechanism. This may especially hold true when tissue loss is very high, because other compensatory mechanisms may be insufficient. On inland dunes in northern China, we subjected Bromus ircutensis and Psammochloa villosa ramets within 0.5 m×0.5 m plots to three clipping treatments, i.e., no clipping, moderate (50% shoot removal) and heavy clipping (90% shoot removal), and kept rhizomes at the plot edges connected or disconnected. Moderate clipping did not reduce ramet, leaf or biomass density of either species. Under moderate clipping, rhizome connection significantly improved the performance of Psammochloa, but not that of Bromus. Heavy clipping reduced ramet, leaf and biomass density in the disconnected plots of both species, but such negative effects were negated or greatly ameliorated when the rhizomes were connected. Therefore, clonal integration contributed greatly to the compensatory growth of both species. The results suggest that clonal integration is an additional compensatory mechanism for clonal plants and may be important for their long-term persistence in the heavily grazed regions in northern China. 相似文献
24.
Separation in flowering time contributes to the maintenance of sympatric cryptic plant lineages 下载免费PDF全文
Sympatric cryptic lineages are a challenge for the understanding of species coexistence and lineage diversification as well as for management, conservation, and utilization of plant genetic resources. In higher plants studies providing insights into the mechanisms creating and maintaining sympatric cryptic lineages are rare. Here, using microsatellites and chloroplast sequence data, morphometric analyses, and phenological observations, we ask whether sympatrically coexisting lineages in the common wetland plant Juncus effusus are ecologically differentiated and reproductively isolated. Our results show two genetically highly differentiated, homoploid lineages within J. effusus that are morphologically cryptic and have similar preference for soil moisture content. However, flowering time differed significantly between the lineages contributing to reproductive isolation and the maintenance of these lineages. Furthermore, the later flowering lineage suffered less from predispersal seed predation by a Coleophora moth species. Still, we detected viable and reproducing hybrids between both lineages and the earlier flowering lineage and J. conglomeratus, a coexisting close relative. Flowering time differentiation between the lineages can be explained by neutral divergence alone and together with a lack of postzygotic isolation mechanisms; the sympatric coexistence of these lineages is most likely the result of an allopatric origin with secondary contact. 相似文献
25.
26.
鸟类的鸣唱方言是研究非人类文化进化及其与种群遗传分化相互作用的理想素材。该研究通过比较跨度8年的2001年和2009年青海门源赭红尾鸲(Phoenicurus ochruros rufiventris)鸣唱,研究结果显示,青海门源赭红尾鸲的种特异性音节、经典唱段中的部分音节、典型唱段结构和鸣唱方言的基本形式都具有较高的时间稳定性。2009年赭红尾鸲唱段曲目多于2001年,共享唱段出现了一定的分化,唱段的共享程度和鸣唱的相似性与个体领域间的距离相关,相邻个体的鸣唱相似性程度高于较远距离的个体。 相似文献
27.
28.
29.
30.
Multilevel modeling analysis of dyadic network data with an application to Ye'kwana food sharing 下载免费PDF全文
Jeremy Koster George Leckie Andrew Miller Raymond Hames 《American journal of physical anthropology》2015,157(3):507-512
Behavioral ecologists have recently begun using multilevel modeling for the analysis of social behavior. We present a multilevel modeling formulation of the Social Relations Model that is well suited for the analysis of dyadic network data. This model, which we adapt for count data and small datasets, can be fitted using standard multilevel modeling software packages. We illustrate this model with an analysis of meal sharing among Ye'kwana horticulturalists in Venezuela. In this setting, meal sharing among households is predicted by an association index, which reflects the amount of time that members of the households are interacting. This result replicates recent findings that interhousehold food sharing is especially prevalent among households that interact and cooperate in multiple ways. We discuss opportunities for human behavioral ecologists to expand their focus to the multiple currencies and cooperative behaviors that characterize interpersonal relationships in preindustrial societies. We discuss possible extensions to this statistical modeling approach and applications to research by human behavioral ecologists and primatologists. Am J Phys Anthropol 157:507–512, 2015. © 2015 Wiley Periodicals, Inc. 相似文献