首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   110篇
  免费   10篇
  2023年   1篇
  2021年   4篇
  2020年   1篇
  2019年   4篇
  2018年   2篇
  2017年   1篇
  2016年   6篇
  2015年   5篇
  2014年   7篇
  2013年   4篇
  2012年   9篇
  2011年   7篇
  2010年   3篇
  2009年   3篇
  2008年   7篇
  2007年   6篇
  2006年   5篇
  2005年   7篇
  2004年   1篇
  2003年   4篇
  2002年   3篇
  2001年   4篇
  2000年   2篇
  1999年   2篇
  1998年   2篇
  1997年   3篇
  1996年   3篇
  1995年   1篇
  1994年   2篇
  1993年   2篇
  1992年   2篇
  1991年   2篇
  1988年   1篇
  1984年   1篇
  1981年   1篇
  1980年   1篇
  1976年   1篇
排序方式: 共有120条查询结果,搜索用时 15 毫秒
1.
We have evaluated codon usage bias in Drosophila histone genes and have obtained the nucleotide sequence of a 5,161-bp D. hydei histone gene repeat unit. This repeat contains genes for all five histone proteins (H1, H2a, H2b, H3, and H4) and differs from the previously reported one by a second EcoRI site. These D. hydei repeats have been aligned to each other and to the 5.0-kb (i.e., long) and 4.8-kb (i.e., short) histone repeat types from D. melanogaster. In each species, base composition at synonymous sites is similar to the average genomic composition and approaches that in the small intergenic spacers of the histone gene repeats. Accumulation of synonymous changes at synonymous sites after the species diverged is quite high. Both of these features are consistent with the relatively low codon usage bias observed in these genes when compared with other Drosophila genes. Thus, the generalization that abundantly expressed genes in Drosophila have high codon bias and low rates of silent substitution does not hold for the histone genes.   相似文献   
2.
In this study, new chiral thiourea and 1,3-thiazolidine-4,5-dione derivatives were synthesized, it was aimed to evaluate the various biological activities and molecular docking of these compounds. Firstly, the new thioureas ( 1 – 16 ) were obtained by reacting 1-naphthylisothiocyanate with different chiral amines. Then, the chiral thioureas were cyclized with oxalyl chloride to obtain 1,3-thiazolidine-4,5-dione derivatives ( 17 – 32 ). All compounds were evaluated with several in vitro antioxidant and enzyme inhibition activities. Compound 30 was the most active compound against AChE, with a value of IC50=8.09±0.58 μM. On the other hand, all compounds were tested in silico absorption, distribution, metabolism, and excretion (ADME) assays to better understand their bioavailability. These physicochemical properties, pharmacokinetics, and drug-likeness of all compounds were calculated using SwissADME. Furthermore, according to molecular docking analyses compound 30 exhibited significant binding affinities for all enzymes. Based on our overall observations, compound 30 could be recommended as a potential lead for the therapuetic of Alzheimer's.  相似文献   
3.
The rate of uptake of uridine into the acid-soluble fraction of Novikoff hepatoma cells is inhibited by low concentrations of the ionophores A23187 and gramicidin and other perturbants of intracellular cation levels. Inhibition of uridine uptake by A23187 is dependent on Ca2+ and is reduced by serum and high levels of Mg2+. The effectiveness of A23187 is dependent on the Ca2+/Mg2+ ratio rather than the absolute concentration of either ion. Inhibition of uridine uptake by gramicidin is not significantly affected by serum or divalent cations. Other effectors of monovalent cation flux such as ouabain and valinomycin also inhibit uridine uptake. These results indicate that net uptake of uridine may be influenced by intracellular levels of certain monovalent and divalent inorganic cations.  相似文献   
4.
5.
6.
The semen of many primate species coagulates into a mating plug believed to prevent the sperm of subsequent mating events from accessing the ova. The texture of the coagulum varies among species: from a semisoft mass in humans to a firm plug in chimpanzees. In humans, a component of the coagulum, semenogelin I, also inhibits sperm motility. We tested the hypothesis that polymorphism and divergence at semenogelin I differ among hominoid species with different mating systems. Sequence data for the semenogelin I locus were obtained from 12 humans, 10 chimpanzees, 7 gorillas, and 1 bonobo. Mitochondrial D-loop data were collected from a subset of individuals to assess levels of variation at an unlinked locus. HKA tests using D-loop sequence data revealed a significant reduction of polymorphism at semenogelin I in chimpanzees, consistent with predictions of a selective sweep at this locus. This result was supported by independent HKA tests using polymorphism data from a putatively neutral locus from the literature. Humans show a similar trend toward reduced polymorphism, although HKA tests were only marginally significant. Gorilla sequence data show evidence of functional loss at the semenogelin I locus, indicated by stop codons within the putative open reading frame as well as high levels of polymorphism. Elevated K a/K s ratios within the PanHomo clade suggest a history of positive selection at semenogelin I. Our results suggest that there is a positive relationship between the intensity of sperm competition in a species and the strength of positive Darwinian selection on the seminal protein semenogelin I.  相似文献   
7.
Peripheral blood cultures were exposed to various doses (5 to 500 mg/L) of boron compounds. Sister-chromatid exchange, micronucleus and chromosomal aberration tests were applied to estimate the DNA damage, and biochemical parameters (superoxide dismutase, catalase, glutathione peroxidase, glutathione-S-transferase, glucose-6-phosphate dehydrogenase, total glutathione, malondialdehyde and total antioxidant capacity) were examined to determine oxidative stress. According to our findings, various boron compounds at low doses were useful in supporting antioxidant enzyme activities in human blood cultures. It was found that the boron compounds do not have genotoxic effects even in the highest concentrations, though in increasing doses they constitute oxidative stress. It is concluded that the tested boron compounds can be used safely, but it is necessary to consider the tissue damages which are likely to appear depending on the oxidative stress.  相似文献   
8.
Time course gene expression experiments are a popular means to infer co-expression. Many methods have been proposed to cluster genes or to build networks based on similarity measures of their expression dynamics. In this paper we apply a correlation based approach to network reconstruction to three datasets of time series gene expression following system perturbation: 1) Conditional, Tamoxifen dependent, activation of the cMyc proto-oncogene in rat fibroblast; 2) Genomic response to nutrition changes in D. melanogaster; 3) Patterns of gene activity as a consequence of ageing occurring over a life-span time series (25y-90y) sampled from T-cells of human donors. We show that the three datasets undergo similar transitions from an "uncorrelated" regime to a positively or negatively correlated one that is symptomatic of a shift from a "ground" or "basal" state to a "polarized" state. In addition, we show that a similar transition is conserved at the pathway level, and that this information can be used for the construction of "meta-networks" where it is possible to assess new relations among functionally distant sets of molecular functions.  相似文献   
9.
Tatar M 《Developmental cell》2007,12(3):322-324
How dietary restriction extends life span may involve anticipatory neurons. The odor of dietary yeast is sufficient to speed Drosophila aging while mutants of an odorant-binding protein extend life span.  相似文献   
10.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号