全文获取类型
收费全文 | 479篇 |
免费 | 41篇 |
出版年
2020年 | 4篇 |
2019年 | 2篇 |
2018年 | 7篇 |
2017年 | 6篇 |
2016年 | 8篇 |
2015年 | 21篇 |
2014年 | 22篇 |
2013年 | 40篇 |
2012年 | 24篇 |
2011年 | 25篇 |
2010年 | 31篇 |
2009年 | 30篇 |
2008年 | 20篇 |
2007年 | 16篇 |
2006年 | 15篇 |
2005年 | 22篇 |
2004年 | 20篇 |
2003年 | 7篇 |
2002年 | 9篇 |
2001年 | 12篇 |
2000年 | 14篇 |
1999年 | 6篇 |
1998年 | 11篇 |
1997年 | 11篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 7篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 9篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 10篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 16篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1973年 | 3篇 |
1971年 | 4篇 |
1970年 | 2篇 |
1966年 | 2篇 |
排序方式: 共有520条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
Edward L. Kean 《Glycoconjugate journal》1996,13(4):675-680
Mannosyl-P-dolichol (man-P-dol) has been shown to stimulate the early reactions of the dolichol pathway, specifically, the biosynthesis of GlcNAc-P-P-dol and GlcNAc-GlcNAc-P-P-dol, and thus may play a regulatory role in glycoprotein biosynthesis. The site of action of man-P-dol has previously been suggested to be the GlcNAc-transferase concerned with the formation of the monoglucosaminyl derivative. Since the concentration of the chitobiosyl compound also increases as a result of the presence of man-P-dol, the immediate site of the activation was reexamined. The effect of man-P-dol on the formation of GlcNAc-GlcNAc-P-P-dol using GlcNAc-P-P-dol synthesizedin situ or added exogenously as the substrate was investigated. In addition, the distribution of radioactivity in the glucosaminyl constituents of the products under the stimulatory conditions was determined. The results of these studies supported the conclusion that the stimulation of GlcNAc-lipid synthesis by man-P-dol is due to the enhanced synthesis of GlcNAc-P-P-dol. It is not a result of the activation of the GlcNAc-transferase catalyzing the attachment of the second GlcNAc residue for the biosynthesis of the chitobiosyl derivative.Abbreviations GlcNAc-P-P-dol
N-acetylglucosaminylpyrophosphoryldolichol
- GlcNAc-GlcNAc-P-P-dol
N-acetylglucosaminyl-N-acetylglucosaminylpyrophosphoryldolichol;
- chito
N-N-diacetylchitobiose
- man-P-dol
mannosylphosphoryldolichol
- TX-100
triton X-100
- Tes
2-{[tris-(hydroxymethyl)-methyl]-amino}-ethanesulfonic acid 相似文献
6.
Sequences within the poliovirus internal ribosome entry segment control viral RNA synthesis. 总被引:26,自引:0,他引:26 下载免费PDF全文
The 5' untranslated region of poliovirus RNA has been reported to possess two functional elements: (i) the 5' proximal 88 nucleotides form a cloverleaf structure implicated in positive-strand RNA synthesis during viral replication, and (ii) nucleotides 134 to at least 556 function as a highly structured internal ribosome entry segment (IRES) during cap-independent, internal initiation of translation. We show here that the IRES itself is bifunctional and contains sequences necessary for viral RNA synthesis per se. For this purpose, we used a dicistronic poliovirus RNA in which the translation of the viral non-structural (replication) proteins is uncoupled from the poliovirus IRES. In this system, RNA synthesis is readily detectable in transfected cells, even when the poliovirus IRES is inactivated by point mutation. However, deletion of the major part of the poliovirus IRES renders viral-specific RNA synthesis undetectable. Using the same system, we show that a three nucleotide deletion at position 500 in the 5' untranslated region drastically affects both translation efficiency and RNA synthesis. Furthermore, disruption of the secondary structure of the IRES around nucleotide 343 has minimal effects on IRES function, but dramatically reduces viral RNA replication. Taken together, these results provide direct evidence that sequences essential for viral RNA synthesis are located in the 3' region of the poliovirus IRES. 相似文献
7.
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
8.
9.
E Homsher C J Kean A Wallner V Garibian-Sarian 《The Journal of general physiology》1979,73(5):553-567
Unpoisoned sartorius muscles of Rana temporaria were stimulated tetanically in isometric contractions lasting up to 20 s at 0 degrees C. The observed enthalpy (heat + work) production and the chemical changes in these contractions were measured, and a comparison was made between the observed enthalpy and the enthalpy that could be explained by the chemical changes. Like earlier workers, we found that the only net known reaction of energetic significance that occurred was dephosphorylation of n-phosphoryl creatine (PC), and we found a significant evolution of unexplained enthalpy (UE), a portion of the observed enthalpy which could not be explained by the extent of PC dephosphorylation. We measured the total quantity and the rate of production of the UE, and we found that its rate of evolution, which was most rapid during the first 750 ms of contraction, fell progressively to zero by the 8th s of contraction: i.e., after 8 s of contraction, all the observed enthalpy is adequately explained by PC dephosphorylation. The time-course of evolution of the UE was slower than that of the labile enthalpy (a component of the enthalpy evolved in isometric contraction whose rate of production declines exponentially at approximately 1 s-1). We conclude that, although the magnitudes of these enthalpy quantities may be similar, they are not derived from the same chemical reaction in muscle. 相似文献
10.