全文获取类型
收费全文 | 30831篇 |
免费 | 2814篇 |
国内免费 | 26篇 |
出版年
2023年 | 108篇 |
2022年 | 77篇 |
2021年 | 500篇 |
2020年 | 259篇 |
2019年 | 397篇 |
2018年 | 487篇 |
2017年 | 454篇 |
2016年 | 760篇 |
2015年 | 1316篇 |
2014年 | 1447篇 |
2013年 | 1780篇 |
2012年 | 2299篇 |
2011年 | 2292篇 |
2010年 | 1524篇 |
2009年 | 1310篇 |
2008年 | 1919篇 |
2007年 | 1980篇 |
2006年 | 1834篇 |
2005年 | 1798篇 |
2004年 | 1746篇 |
2003年 | 1664篇 |
2002年 | 1612篇 |
2001年 | 302篇 |
2000年 | 228篇 |
1999年 | 363篇 |
1998年 | 440篇 |
1997年 | 290篇 |
1996年 | 248篇 |
1995年 | 260篇 |
1994年 | 241篇 |
1993年 | 262篇 |
1992年 | 266篇 |
1991年 | 222篇 |
1990年 | 218篇 |
1989年 | 175篇 |
1988年 | 149篇 |
1987年 | 151篇 |
1986年 | 116篇 |
1985年 | 176篇 |
1984年 | 166篇 |
1983年 | 147篇 |
1982年 | 174篇 |
1981年 | 155篇 |
1980年 | 149篇 |
1979年 | 111篇 |
1978年 | 123篇 |
1977年 | 116篇 |
1976年 | 107篇 |
1975年 | 82篇 |
1973年 | 75篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Eric L. Stevens Joseph D. Baugher Matthew D. Shirley Laurence P. Frelin Jonathan Pevsner 《PloS one》2012,7(11)
Correct annotation of the genetic relationships between samples is essential for population genomic studies, which could be biased by errors or omissions. To this end, we used identity-by-state (IBS) and identity-by-descent (IBD) methods to assess genetic relatedness of individuals within HapMap phase III data. We analyzed data from 1,397 individuals across 11 ethnic populations. Our results support previous studies (Pemberton et al., 2010; Kyriazopoulou-Panagiotopoulou et al., 2011) assessing unknown relatedness present within this population. Additionally, we present evidence for 1,657 novel pairwise relationships across 9 populations. Surprisingly, significant Cotterman''s coefficients of relatedness K1 (IBD1) values were detected between pairs of known parents. Furthermore, significant K2 (IBD2) values were detected in 32 previously annotated parent-child relationships. Consistent with a hypothesis of inbreeding, regions of homozygosity (ROH) were identified in the offspring of related parents, of which a subset overlapped those reported in previous studies (Gibson et al. 2010; Johnson et al. 2011). In total, we inferred 28 inbred individuals with ROH that overlapped areas of relatedness between the parents and/or IBD2 sharing at a different genomic locus between a child and a parent. Finally, 8 previously annotated parent-child relationships had unexpected K0 (IBD0) values (resulting from a chromosomal abnormality or genotype error), and 10 previously annotated second-degree relationships along with 38 other novel pairwise relationships had unexpected IBD2 (indicating two separate paths of recent ancestry). These newly described types of relatedness may impact the outcome of previous studies and should inform the design of future studies relying on the HapMap Phase III resource. 相似文献
32.
33.
34.
Elinor McKone Sacha Stokes Jia Liu Sarah Cohan Chiara Fiorentini Madeleine Pidcock Galit Yovel Mary Broughton Michel Pelleg 《PloS one》2012,7(10)
Other-race and other-ethnicity effects on face memory have remained a topic of consistent research interest over several decades, across fields including face perception, social psychology, and forensic psychology (eyewitness testimony). Here we demonstrate that the Cambridge Face Memory Test format provides a robust method for measuring these effects. Testing the Cambridge Face Memory Test original version (CFMT-original; European-ancestry faces from Boston USA) and a new Cambridge Face Memory Test Chinese (CFMT-Chinese), with European and Asian observers, we report a race-of-face by race-of-observer interaction that was highly significant despite modest sample size and despite observers who had quite high exposure to the other race. We attribute this to high statistical power arising from the very high internal reliability of the tasks. This power also allows us to demonstrate a much smaller within-race other ethnicity effect, based on differences in European physiognomy between Boston faces/observers and Australian faces/observers (using the CFMT-Australian). 相似文献
35.
Eric S. J. Harris Shugeng Cao Sean D. Schoville Chengming Dong Wenquan Wang Zaiyou Jian Zhongzhen Zhao David M. Eisenberg Jon Clardy 《PloS one》2012,7(11)
Oridonin is a diterpenoid with anti-cancer activity that occurs in the Chinese medicinal plant Isodon rubescens and some related species. While the bioactivity of oridonin has been well studied, the extent of natural variation in the production of this compound is poorly known. This study characterizes natural variation in oridonin production in order to guide selection of populations of Isodon with highest oridonin yield. Different populations of I. rubescens and related species were collected in China, and their offspring were grown in a greenhouse. Samples were examined for oridonin content, genotyped using 11 microsatellites, and representatives were sequenced for three phylogenetic markers (ITS, rps16, trnL-trnF). Oridonin production was mapped on a molecular phylogeny of the genus Isodon using samples from each population as well as previously published Genbank sequences. Oridonin has been reported in 12 out of 74 species of Isodon examined for diterpenoids, and the phylogeny indicates that oridonin production has arisen at least three times in the genus. Oridonin production was surprisingly consistent between wild-collected parents and greenhouse-grown offspring, despite evidence of gene flow between oridonin-producing and non-producing populations of Isodon. Additionally, microsatellite genetic distance between individuals was significantly correlated with chemical distance in both parents and offspring. Neither heritability nor correlation with genetic distance were significant when the comparison was restricted to only populations of I. rubescens, but this result should be corroborated using additional samples. Based on these results, future screening of Isodon populations for oridonin yield should initially prioritize a broad survey of all species known to produce oridonin, rather than focusing on multiple populations of one species, such as I. rubescens. Of the samples examined here, I. rubescens or I. japonicus from Henan province would provide the best source of oridonin. 相似文献
36.
37.
Mounting evidence shows that contrasting selection pressures generate variability in dispersal patterns among individuals or populations of the same species, with potential impacts on both species dynamics and evolution. However, this variability is hardly considered in empirical works, where a single dispersal function is considered to adequately reflect the species-specific dispersal ability, suggesting thereby that within-species variation is negligible as regard to inter-specific differences in dispersal abilities. We propose here an original method to make the comparison of intra- and inter-specific variability in dispersal, by decomposing the diversity of that trait along a phylogeny of closely related species. We used as test group European butterflies that are classic study organisms in spatial ecology. We apply the analysis separately to eight metrics that reflect the dispersal propensity, the dispersal ability or the dispersal efficiency of populations and species. At the inter-specific level, only the dispersal ability showed the signature of a phylogenetic signal while neither the dispersal propensity nor the dispersal efficiency did. At the within-species level, the partitioning of dispersal diversity showed that dispersal was variable or highly variable among populations: intra-specific variability represented from 11% to 133% of inter-specific variability in dispersal metrics. This finding shows that dispersal variation is far from negligible in the wild. Understanding the processes behind this high within-species variation should allow us to properly account for dispersal in demographic models. Accordingly, to encompass the within species variability in life histories the use of more than one value per trait per species should be encouraged in the construction of databases aiming at being sources for modelling purposes. 相似文献
38.
39.
40.