全文获取类型
收费全文 | 433篇 |
免费 | 29篇 |
出版年
2018年 | 4篇 |
2016年 | 8篇 |
2015年 | 14篇 |
2014年 | 16篇 |
2013年 | 25篇 |
2012年 | 15篇 |
2011年 | 15篇 |
2010年 | 28篇 |
2009年 | 27篇 |
2008年 | 15篇 |
2007年 | 16篇 |
2006年 | 11篇 |
2005年 | 17篇 |
2004年 | 14篇 |
2003年 | 5篇 |
2002年 | 5篇 |
2001年 | 9篇 |
2000年 | 9篇 |
1999年 | 8篇 |
1998年 | 10篇 |
1997年 | 11篇 |
1996年 | 5篇 |
1995年 | 12篇 |
1994年 | 4篇 |
1993年 | 7篇 |
1991年 | 5篇 |
1989年 | 6篇 |
1988年 | 11篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 17篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 10篇 |
1976年 | 4篇 |
1975年 | 6篇 |
1974年 | 5篇 |
1973年 | 7篇 |
1972年 | 3篇 |
1971年 | 4篇 |
1970年 | 6篇 |
1969年 | 4篇 |
1968年 | 2篇 |
1967年 | 6篇 |
1966年 | 2篇 |
排序方式: 共有462条查询结果,搜索用时 15 毫秒
1.
The role of the carbohydrate residues of fibronectin concerning the specificities of that glycoprotein to interact with fibroblastic cell surfaces, gelatin, and heparin was examined. Tunicamycin was used to produce carbohydrate-depleted fibronectin; it was synthesized by cultured fibroblasts. Unglycosylated and glycosylated fibronectins were analyzed for their ability to bind gelatin and heparin, using affinity columns. Fibronectin-coated surfaces were used to quantitatively measure cell adhesion and spreading. The results showed that the lack of carbohydrates significantly increased the interaction of the protein with gelatin and markedly enhanced its ability to promote adhesion and spreading of fibroblasts. In contrast, the binding of fibronectin to heparin was not influenced by glycosylation. The composite data indicate that the Asn-linked oligosaccharides of fibronectin act as modulators of biological functions of the glycoprotein. 相似文献
2.
3.
4.
5.
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
6.
D. J. Morré R. Merriman L. R. Tanzer L. -Y. Wu D. M. Morré W. C. MacKellar 《Protoplasma》1995,184(1-4):203-208
Summary Inhibition of NADH oxidase activity of plasma membranes isolated from a series of human xenografts and cell lines by the antitumor sulfonylurea, N-(4-methylphenylsulfonyl)-N-(4-chlorophenyl) urea (LY 181984), correlated with the ability of the sulfonylurea to inhibit cell growth. Growth of rat kidney cells either untransformed or transformed with Kirsten-ras (K-ras) were unaffected by the sulfonylurea. Similarly, the NADH oxidase activity of isolated plasma membranes from K-ras transformed cells was unaffected by LY 181984. In contrast, when transformed with Harvey-ras (H-ras), both growth and NADH oxidase activity were inhibited. With the inactive but structurally related LY 181985 (N-4-methylphenyl-sulfonyl)-N-(phenyl)urea), neither growth nor plasma membrane NADH oxidase activity of either sulfonylurea-susceptible or -resistant tissues or cell lines was inhibited. Both sulfonylureas were inactive with rat liver plasma membranes but NADH oxidase activity of plasma membranes and growth with HeLa cells was inhibited by the active (LY 181984) but not by the inactive (LY 181985) sulfonylurea. The findings suggest a possible correlation between inhibition of plasma membrane NADH oxidase activity by the antitumor sulfonylureas and their oncolytic action. 相似文献
7.
8.
9.
10.