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   77篇
  免费   21篇
  2023年   1篇
  2022年   1篇
  2021年   1篇
  2020年   1篇
  2019年   1篇
  2018年   1篇
  2017年   2篇
  2015年   3篇
  2014年   5篇
  2013年   4篇
  2012年   4篇
  2011年   2篇
  2010年   6篇
  2009年   3篇
  2008年   4篇
  2007年   3篇
  2006年   3篇
  2005年   5篇
  2004年   5篇
  2003年   3篇
  2002年   1篇
  2001年   2篇
  2000年   5篇
  1999年   2篇
  1998年   1篇
  1996年   1篇
  1993年   5篇
  1991年   1篇
  1990年   2篇
  1989年   1篇
  1988年   5篇
  1985年   10篇
  1983年   2篇
  1980年   1篇
  1974年   1篇
排序方式: 共有98条查询结果,搜索用时 109 毫秒
61.
62.
63.
64.
Three species of Entomophthorales were found on adult carrot flies (Psila rosae F.) during two successive seasons:Entomophthora muscae (C.) Fres.,Condiobolus apiculatus (Thax.) Remaud. & Keller andErynia sp.E. muscae was by far the most common species and caused epizootics in one carrot fly population up to 3 times per year. Flies cuaght in the hedge showed a higher infection level than flies caught in the field close to the hedge. Flies caught 200 m away from the hedge showed the lowest infection level. Apparently the hedge was the site of infection, since carrot flies, killed byE. muscae, were found there attached to the underside of the leaves. Flies caught on yellow sticky traps developed only to a limited extend symptoms and gave little information about the fungus infection levels.  相似文献   
65.
Single-copy human beta-globin transgenes are very susceptible to suppression by position effects of surrounding closed chromatin. However, these position effects are overcome by a 20 kbp DNA fragment containing the locus control region (LCR). Here we show that the 6.5 kbp microlocus LCR cassette reproducibly directs full expression from independent single-copy beta-globin transgenes. By testing individual DNase I-hypersensitive sites (HS) present in the microlocus cassette, we demonstrate that the 1.5 kbp 5'HS2 enhancer fragment does not direct beta-globin expression from single-copy transgenes. In contrast, the 1.9 kbp 5'HS3 fragment directs beta-globin expression in five independent single-copy transgenic mouse lines. Moreover, the 5'HS3 core element and beta-globin proximal promoter sequences are DNase I hypersensitive in fetal liver nuclei of these expressing transgenic lines. Taken together, these results demonstrate that LCR activity is the culmination of at least two separable functions including: (i) a novel activity located in 5'HS3 that dominantly opens and remodels chromatin structure; and (ii) a recessive enhancer activity residing in 5'HS2. We postulate that the different elements of the LCR form a 'holocomplex' that interacts with the individual globin genes.  相似文献   
66.
The beta-globin dominant control region: hypersensitive site 2.   总被引:58,自引:10,他引:48       下载免费PDF全文
The Dominant Control Region (DCR) of the human beta-globin gene locus consists of four strong hypersensitive sites (HSS) upstream of the epsilon-globin gene. Addition of these sites confers copy number dependent expression on the human beta-globin gene in murine erythroleukaemia cells and transgenic mice, at levels comparable with the endogenous mouse globin genes. We have shown previously that a 1.9 kb fragment comprising HSS 2 accounts for 40-50% of the full effect of the DCR. In this paper we describe a deletional analysis of HSS 2. We show that a 225 bp fragment is sufficient to direct high levels of expression of the human beta-globin gene which is copy number dependent and integration site independent. This 225 bp fragment overlaps the major region that is hypersensitive 'in vivo'. DNase I footprinting shows the presence of four binding sites for the erythroid specific protein NF-E1; the three other footprinted regions display a remarkable redundancy of the sequence GGTGG and bind a number of proteins including Sp1 and the CACC box protein. The significance of these results for the regulation of globin gene expression is discussed.  相似文献   
67.
68.
Hypersensitive site 5 (5'HS5) of the beta-globin Locus Control Region functions as a developmental stage-specific border in erythroid cells. Here, we have analyzed the role of 5'HS5 in the three dimensional organization of the beta-gene locus using the Chromatin Conformation Capture (3C) technique. The results show that when 5'HS5 is deleted from the locus, both remote and internal regulatory elements are still able to interact with each other in a three-dimensional configuration termed the Active Chromatin Hub. Thus, the absence of 5'HS5 does not have an appreciable effect on the three dimensional organization of the beta-globin locus. This rules out models in which 5'HS5 nucleates interactions with remote and/or internal regulatory elements. We also determined the binding of CTCF, the only defined insulator protein in mammalian cells, to 5'HS5 by using chromatin immunoprecipitation (ChIP) assays. We detect low levels of CTCF binding to 5'HS5 in primitive erythroid cells, in which it functions as a border element. Surprisingly, we also observe binding levels of CTCF to 5'HS5 in definitive erythroid cells. Thus, binding of CTCF to 5'HS5 per se does not render it a functional border element. This is consistent with the previous data suggesting that CTCF has dual functionality.  相似文献   
69.
The main purpose of this study was to examine whether adult patients with attention deficit hyperactivity disorder (ADHD) demonstrate sets of dysfunctional cognitive beliefs and behavioural tendencies according to Jeffrey Young’s schema-focused therapy model. Sets of dysfunctional beliefs (maladaptive schemas) were assessed with the Young Schema Questionnaire (YSQ-S2) in 78 adult ADHD patients and 80 control subjects. Patients with ADHD scored significantly higher than the control group on almost all maladaptive schemas. The ‘Failure’, ‘Defectiveness/Shame’, ‘Subjugation’ and ‘Emotional Deprivation’ schemas were most pronounced in adult ADHD patients, while only ‘Vulnerability to Harm or Illness’ did not differ between the two groups. The schemas which were most pronounced in adult patients with ADHD correspond well with their learning histories and core symptoms. By demonstrating the existence of early maladaptive schemas in adults suffering from ADHD, this study suggests that schema theory may usefully be applied to adult ADHD therapy.  相似文献   
70.
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