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   78篇
  免费   4篇
  82篇
  2019年   3篇
  2017年   1篇
  2016年   2篇
  2015年   2篇
  2014年   3篇
  2013年   2篇
  2012年   4篇
  2011年   2篇
  2010年   1篇
  2008年   5篇
  2007年   2篇
  2006年   1篇
  2005年   3篇
  2004年   1篇
  2002年   1篇
  2001年   2篇
  2000年   3篇
  1999年   2篇
  1996年   1篇
  1995年   1篇
  1993年   1篇
  1992年   3篇
  1990年   1篇
  1989年   1篇
  1988年   1篇
  1987年   2篇
  1985年   2篇
  1982年   1篇
  1980年   1篇
  1977年   1篇
  1975年   2篇
  1973年   3篇
  1972年   2篇
  1971年   3篇
  1970年   4篇
  1969年   1篇
  1968年   6篇
  1966年   2篇
  1965年   1篇
  1964年   1篇
  1945年   1篇
排序方式: 共有82条查询结果,搜索用时 15 毫秒
1.

Background  

Microarray-based pooled DNA experiments that combine the merits of DNA pooling and gene chip technology constitute a pivotal advance in biotechnology. This new technique uses pooled DNA, thereby reducing costs associated with the typing of DNA from numerous individuals. Moreover, use of an oligonucleotide gene chip reduces costs related to processing various DNA segments (e.g., primers, reagents). Thus, the technique provides an overall cost-effective solution for large-scale genomic/genetic research. However, few publicly shared tools are available to systematically analyze the rapidly accumulating volume of whole-genome pooled DNA data.  相似文献   
2.
3.
Circulating hematopoietic progenitor cells in runners.   总被引:1,自引:0,他引:1  
Because endurance exercise causes release of mediators and growth factors active on the bone marrow, we asked whether it might affect circulating hematopoietic progenitor cells (HPCs) in amateur runners [n = 16, age: 41.8 +/- 13.5 (SD) yr, training: 93.8 +/- 31.8 km/wk] compared with sedentary controls (n = 9, age: 39.4 +/- 10.2 yr). HPCs, plasma cortisol, interleukin (IL)-6, granulocyte colony-stimulating factor (G-CSF), and the growth factor fms-like tyrosine kinase-3 (flt3)-ligand were measured at rest and after a marathon (M; n = 8) or half-marathon (HM; n = 8). Circulating HPC counts (i.e., CD34(+) cells and their subpopulations) were three- to fourfold higher in runners than in controls at baseline. They were unaffected by HM or M acutely but decreased the morning postrace. Baseline cortisol, flt3-ligand, IL-6, and G-CSF levels were similar in runners and controls. IL-6 and G-CSF increased to higher levels after M compared with HM, whereas cortisol and flt3-ligand increased similarly postrace. Our data suggest that increased HPCs reflect an adaptation response to recurrent, exercise-associated release of neutrophils and stress and inflammatory mediators, indicating modulation of bone marrow activity by habitual running.  相似文献   
4.
  总被引:2,自引:0,他引:2  
We evaluated the levels of15(S)-hydroxyeicosatetraenoic acid [15(S)-HETE] and the expression of15-lipoxygenase (15-LO) mRNA in induced sputum obtained from 10 controland 15 chronic bronchitis subjects. 15(S)-HETE was evaluated by reversephase high-performance liquid chromatography separationfollowed by specific RIA. 15-LO mRNA expression was determined byprimed in situ labeling. The levels of both soluble and cell-associated 15(S)-HETE resulted significantly higher in chronic bronchitis than incontrol subjects. The percentage of cells expressing 15-LO mRNA wassignificantly higher in chronic bronchitis than in control subjects(P < 0.01). Double staining for specific cell typemarkers and 15-LO mRNA showed macrophages and neutrophils positive for 15-LO, whereas similar staining of peripheral blood neutrophils did notshow evidence for 15-LO expression, suggesting that expression of 15-LOin neutrophils takes place on migration into the airways. Because15(S)-HETE inversely correlated with the percentage of neutrophils insputum of chronic bronchitis subjects, we studied the effect of15(S)-HETE on leukotriene B4 (LTB4) productionin vitro and evaluated the concentration of LTB4 in inducedsputum and the contribution of LTB4 to the chemotacticactivity of induced sputum samples ex vivo. The results obtainedindicate that macrophages and neutrophils present within the airways ofchronic bronchitis subjects express 15-LO mRNA; increased basal levelsof 15(S)-HETE may contribute to modulate, through the inhibition of5-lipoxygenase metabolites production, neutrophil infiltration andairway inflammation associated with chronic bronchitis.

  相似文献   
5.
    
Studies of thermal level‐related asynchrony in a host–parasitoid relationship are necessary to understand the effects of climate change on new host–parasitoid interactions. In the Asian chestnut gall wasp Dryocosmus kuriphilus (Hymenoptera: Cynipidae) and its Chalcidoidea parasitoids, phenological synchrony is assumed to be weather‐dependent in a new area of expansion. To evaluate the effects of environmental thermal regimes on the host, a phenology model for different cynipid stages (larvae, pupae, adults, and adult emergence) and a host–parasitoid phenological estimator are developed in three chestnut fields during two successive growth seasons and subsequently validated in areas with chestnut fields at two different altitudes. Comparisons of the timings of the juvenile and adult stages with those of the parasitoid complex demonstrate that the shortest period of occurrence for cynipids within galls has negative effects on the host–parasitoid relationships at higher temperature levels, thereby increasing phenological asynchrony for some parasitoids species. Reducing the development time of pupae and adults decreases the likelihood of success for some parasitoid species at higher temperature levels. We also record the extension of the gall wasp development time (approximately 15 days) at higher altitudes (linked to a lower mean temperature of approximately 1.5 °C). These results highlight how parasitization on the new hosts is dependent on the host phenology and, in the present study, is limited by the short duration of the presence of the host in galls, which could explain the considerable differences in cynipid gall wasp parasitization recorded at different altimeters.  相似文献   
6.
7.
8.
    
In this study, the MCF-7 breast cancer cells that lack caspase-3 were transfected with a wild type (WT) or mutant caspase-3 cDNA. Expression of the WT, but not of the mutant, caspase-3 was associated with increased caspase activity and susceptibility to staurosporine (STS)-induced apoptosis. Both derivatives displayed inhibition of cell growth compared with vector control cells. Growth inhibition was associated with increased expression of the cyclin dependent kinase (CDK) inhibitor p27Kip1 in the WT, but not in the mutant caspase-3 expressing cells. Cyclin D1 expression level was not affected by caspase-3 expression. Phosphorylation of the Akt protein was decreased in both WT and mutant caspase transfected cells, although Akt expression level remained unchanged. These results suggest that caspase-3 might have biological functions independent of its protease activity and that its loss might contribute to tumor development by increasing the growth potential of cancer cells.  相似文献   
9.
10.
以黄嘌岭(X)-黄嘌呤氧化酶(XO)系统产生氧自由基,应用微量生物测定法观察慢性缺氧(5000m,10d)对大鼠氧自由基所致肺内动脉收缩的影响及内皮舒张因子(EDRF)在其中的作用。慢性缺氧大鼠有内皮的肺内动脉环对氧自由基的收缩反应较正常环境中的对照动物明显增强,加入EDRF灭活剂还原型血红蛋白(RHb)后更加显著;而加入超氧化物歧化酶(铜锌SOD)后则减弱,甚至消除。反之,不论加入RHb或SOD对氧自由基所致去内皮肺内动脉环的收缩反应均无明显影响。上述结果表明慢性缺氧引起肺内动脉收缩增强与EDRF有密切关系:慢性缺氧可能使EDRF的作用减弱,肺内动脉对氧自由基的反应性增强。表示EDRF及其与氧自由基的关系在慢性缺氧性肺动脉高压的形成中可能具有十分重要的意义。  相似文献   
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