全文获取类型
收费全文 | 518篇 |
免费 | 38篇 |
出版年
2018年 | 5篇 |
2017年 | 6篇 |
2016年 | 7篇 |
2015年 | 17篇 |
2014年 | 17篇 |
2013年 | 26篇 |
2012年 | 19篇 |
2011年 | 18篇 |
2010年 | 29篇 |
2009年 | 26篇 |
2008年 | 21篇 |
2007年 | 21篇 |
2006年 | 17篇 |
2005年 | 19篇 |
2004年 | 15篇 |
2003年 | 13篇 |
2002年 | 8篇 |
2001年 | 9篇 |
2000年 | 15篇 |
1999年 | 7篇 |
1998年 | 11篇 |
1997年 | 14篇 |
1996年 | 6篇 |
1995年 | 11篇 |
1993年 | 7篇 |
1991年 | 8篇 |
1988年 | 7篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1982年 | 16篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1977年 | 6篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1971年 | 4篇 |
1925年 | 4篇 |
1924年 | 6篇 |
1923年 | 3篇 |
1922年 | 6篇 |
1921年 | 7篇 |
1920年 | 9篇 |
1919年 | 11篇 |
1917年 | 5篇 |
1916年 | 9篇 |
1914年 | 15篇 |
1913年 | 3篇 |
1912年 | 4篇 |
1910年 | 3篇 |
排序方式: 共有556条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
6.
The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from
nucleotide sequence variation across a 765-bp region in the cytochrome
oxidase I and II genes of the mitochondrial genome. Most parsimonious
relationships of 25 haplotypes from 16 Greya species and two outgroup
genera (Tetragma and Prodoxus) showed substantial congruence with the
species relationships indicated by morphological variation. Differences
between mitochondrial and morphological trees were found primarily in the
positions of two species, G. variabilis and G. pectinifera, and in the
branching order of the three major species groups in the genus. Conflicts
between the data sets were examined by comparing levels of homoplasy in
characters supporting alternative hypotheses. The phylogeny of Greya
species suggests that host-plant association at the family level and larval
feeding mode are conservative characters. Transition/transversion ratios
estimated by reconstruction of nucleotide substitutions on the phylogeny
had a range of 2.0-9.3, when different subsets of the phylogeny were used.
The decline of this ratio with the increase in maximum sequence divergence
among taxa indicates that transitions are masked by transversions along
deeper internodes or long branches of the phylogeny. Among transitions,
substitutions of A-->G and T-->C outnumbered their reciprocal
substitutions by 2-6 times, presumably because of the approximately 4:1
(77%) A+T-bias in nucleotide base composition. Of all transversions,
73%-80% were A<-->T substitutions, 85% of which occurred at third
positions of codons; these estimates did not decrease with an increase in
maximum sequence divergence of taxa included in the analysis. The high
frequency of A<-->T substitutions is either a reflection or an
explanation of the 92% A+T bias at third codon positions.
相似文献
7.
8.
9.
R J Buist R Deslauriers J K Saunders G W Mainwood 《Canadian journal of physiology and pharmacology》1991,69(11):1663-1669
23Na nuclear magnetic resonance spectroscopy (NMR) is increasingly being used to study Na+ gradients and fluxes in biological tissues. However, the quantitative aspects of 23Na NMR applied to living systems remain controversial. This paper compares sodium concentrations determined by 23Na NMR in intact rat hindlimb (n = 8) and excised rat gastrocnemius muscle (n = 4) with those obtained by flame photometric methods. In both types of samples, 90% of the sodium measured by flame photometry was found to be NMR-visible. This is much higher than previously reported values. The NMR measurements for intact hindlimb correlated linearly with the flame photometric measurements, implying that one pool of sodium, predominantly extracellular, is 100% visible. From measurements on excised muscle, in which extracellular space is more clearly defined, the NMR visibility of intracellular Na+ was calculated to be 70%, assuming an extracellular space of 12% of the total tissue water volume and an extracellular NMR visibility of 100%. 23Na transverse relaxation measurements were carried out using a Hahn spin echo on both intact hindlimb (n = 1) and excised muscle (n = 2) samples. These showed relaxation curves that could each be described adequately using two relaxation times. The rapidly relaxing component showed a T2 value of 3-4 ms and the slowly relaxing component a T2 of 21-37 ms. A spin lattice relaxation (T1) measurement on intact hindlimb yielded a value of 51 ms. These relatively long relaxation times show that the quadrupolar relaxation effect of Na+ complexing to large macromolecules or being otherwise motionally restricted is relatively weak. This is consistent with the high NMR visibilities reported here. 相似文献
10.
Identification of a splice-site mutation in the aldolase B gene from an individual with hereditary fructose intolerance. 总被引:3,自引:1,他引:2
下载免费PDF全文
![点击此处可从《American journal of human genetics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Hereditary fructose intolerance (HFI) is a potentially fatal autosomal recessive disease of carbohydrate metabolism. HFI patients exhibit a deficiency of fructose 1-phosphate aldolase (aldolase B), the isozyme expressed in tissues that metabolize fructose. The eight protein-coding exons, including splicing signals, of the aldolase B gene from one HFI patient were amplified by PCR. Dot-blot hybridization of the amplified DNA with allele-specific oligonucleotide (ASO) probes revealed a previously described A149P mutation in one allele from the proband. The mutation in the other allele was identified by direct sequencing of the double-stranded PCR-amplified material from the proband. The nucleotide sequence of exon 9 revealed a 7-base deletion/1-base insertion (delta 7 + 1) at the 3' splice site of intron 8 in one allele. This mutation was confirmed by cloning PCR-amplified exon 9 of the proband and determining the sequence of each allele separately. ASO analysis of 18 family members confirmed the Mendelian inheritance of both mutant alleles. The implications of this unique splice-site mutation in HFI are discussed. 相似文献