全文获取类型
收费全文 | 218篇 |
免费 | 16篇 |
国内免费 | 3篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 13篇 |
2020年 | 6篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 9篇 |
2015年 | 13篇 |
2014年 | 13篇 |
2013年 | 12篇 |
2012年 | 25篇 |
2011年 | 20篇 |
2010年 | 9篇 |
2009年 | 9篇 |
2008年 | 11篇 |
2007年 | 11篇 |
2006年 | 8篇 |
2005年 | 4篇 |
2004年 | 3篇 |
2003年 | 2篇 |
2002年 | 5篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 10篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1994年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1967年 | 1篇 |
1966年 | 2篇 |
1900年 | 1篇 |
排序方式: 共有237条查询结果,搜索用时 0 毫秒
1.
F. A. Saw 《BMJ (Clinical research ed.)》1900,1(2043):433-434
2.
3.
S H Saw 《Journal of biosocial science》1990,22(1):101-112
Differences in fertility between the three major ethnic groups (Malays, Chinese and Indians) in Peninsular Malaysia and Singapore have existed since before the onset of fertility decline in the late 1950s and remain today, although the relative positions and the actual differences have changed due to the varying rates of decline. By 1987, the Malays experienced the highest fertility and the Chinese the lowest in both countries but in Singapore the Malay fertility was lower than the Chinese fertility in Peninsular Malaysia. The fertility differentials will lead to changes in the ethnic composition in both countries but more so in Peninsular Malaysia. 相似文献
4.
Detecting non-neutral heterogeneity across a region of DNA sequence in the ratio of polymorphism to divergence 总被引:11,自引:4,他引:7
Natural selection, in the form of balancing selection or selective sweeps,
can result in a decoupling of the amounts of molecular polymorphism and
divergence. Thus natural selection can cause some areas of DNA sequence to
have greater silent polymorphism, relative to divergence between species,
than other areas. It would be useful to have a statistical test for
heterogeneity in the polymorphism to divergence ratio across a region of
DNA sequence, one that could identify heterogeneity greater than that
expected from the neutral processes of mutation, drift, and recombination.
The only currently available test requires that a region be arbitrarily
divided into sections that are compared with each other, and the
subjectivity of this division could be problematic. Here a test is proposed
in which runs of polymorphic and fixed sites are counted, where a "run" is
a set of one or more sites of one type preceded and followed by the other
type. The number of runs is smaller than otherwise expected if
polymorphisms are clumped together. By simulating neutral evolution and
comparing the observed number of runs to the simulations, a statistical
test is possible which does not require any a priori decisions about
subdivision.
相似文献
5.
An inventory was made of 50 ha of primary lowland rain forest in Peninsular Malaysia, in which ca. 340,000 trees 1 cm dbh or larger were measured and identified to species. Out of a total plot tree flora of 820 species, 76 species are known to bear edible fruit. Especially diverse were the wild species of mango (Mangifera, Anacardiaceae, 12 spp.), mangosteen (Garcinia, Clusiaceae, 13 spp.), breadfruit (Artocarpus, Moraceae, 10 spp.) and rambutan (Nephelium, Sapindaceae, 5 spp.). Median population size for all species of fruit trees was 3.0 trees per ha and 0.2 adult trees per ha. Direct economic value of wild fruit trees was small; only one species has been very much collected and sold, Parkia speciosa (Fabaceae), amounting to less than US$20 per ha per year. The potential value of the species as genetic resources is very large: 24 species are cultivated, 38 edible species are congeneric with cultivated crops and at least 10 other species bear inedible fruit but are related to cultivated crops. We conclude that the Peninsular Malaysian rain forest is exceedingly rich in wild fruit trees, that these normally live at low densities, and that their principal economic value is as genetic resources. 相似文献
6.
7.
8.
Jordan Bai Muhammad Farid Abdul-Rahman Anne Rifkin-Graboi Yap-Seng Chong Kenneth Kwek Seang-Mei Saw Keith M. Godfrey Peter D. Gluckman Marielle V. Fortier Michael J. Meaney Anqi Qiu 《PloS one》2012,7(10)
We studied a sample of 75 Chinese, 73 Malay, and 29 Indian healthy neonates taking part in a cohort study to examine potential differences in neonatal brain morphology and white matter microstructure as a function of ethnicity using both structural T2-weighted magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI). We first examined the differences in global size and morphology of the brain among the three groups. We then constructed the T2-weighted MRI and DTI atlases and employed voxel-based analysis to investigate ethnic differences in morphological shape of the brain from the T2-weighted MRI, and white matter microstructure measured by fractional anisotropy derived from DTI. Compared with Malay neonates, the brains of Indian neonates’ tended to be more elongated in anterior and posterior axis relative to the superior-inferior axis of the brain even though the total brain volume was similar among the three groups. Although most anatomical regions of the brain were similar among Chinese, Malay, and Indian neonates, there were anatomical variations in the spinal-cerebellar and cortical-striatal-thalamic neural circuits among the three populations. The population-related brain regions highlighted in our study are key anatomical substrates associated with sensorimotor functions. 相似文献
9.
Congenital diaphragmatic hernia must be seriously considered in the differential diagnosis of acute respiratory distress in neonates as well as in older infants who present with chronic progressive gastrointestinal and respiratory symptoms. An x-ray film of the chest is mandatory and is almost always diagnostic. Immediate nasogastric decompression of the stomach, with simultaneous fluid and electrolyte replacement and prompt surgical intervention offers the patient the best chance of survival. 相似文献
10.