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   74篇
  免费   5篇
  国内免费   10篇
  2023年   1篇
  2022年   2篇
  2021年   6篇
  2020年   6篇
  2019年   2篇
  2018年   3篇
  2017年   2篇
  2016年   7篇
  2015年   2篇
  2014年   7篇
  2013年   1篇
  2012年   10篇
  2011年   3篇
  2010年   8篇
  2009年   11篇
  2008年   4篇
  2007年   2篇
  2006年   3篇
  2005年   1篇
  2004年   3篇
  2003年   1篇
  2001年   2篇
  1999年   1篇
  1998年   1篇
排序方式: 共有89条查询结果,搜索用时 15 毫秒
71.
72.
Accumulating evidence has indicated that long noncoding RNA NEAT1 exerts critical roles in cancers. So far, the detailed biological role and mechanisms of NEAT1, which are responsible for human gastric cancer (GC), are still largely unknown. Here, we observed that NEAT1 and STAT3 expressions were significantly upregulated in human GC cells including BGC823, SGC-7901, AGS, MGC803, and MKN28 cells compared with normal gastric epithelial cells GES-1, while miR-506 was downregulated. We inhibited NEAT1 and observed that NEAT1 inhibition was able to repress the growth, migration, and invasion of GC cells. Conversely, overexpression of NEAT1 exhibited an increased ability of GC progression in BGC823 and SGC-7901 cells. Bioinformatics analysis, dual luciferase reporter assays, RIP assays, and RNA pull-down tests validated the negative binding correlation between NEAT1 and miR-506. In addition, it was found that miR-506 can modulate the expression of NEAT1 in vitro. STAT3 was predicted as a messenger RNA (mRNA) target of miR-506, and miR-506 mimics can suppress STAT3 mRNA expression. Subsequently, it was observed that downregulation of NEAT1 can restrain GC development by decreasing STAT3, which can be reversed by miR-506 inhibitors. Therefore, it was hypothesized in our study that NEAT1 can be recognized as a competing endogenous RNA to modulate STAT3 by sponging miR-506 in GC. In conclusion, we implied that NEAT1 can serve as an important biomarker in GC diagnosis and treatment.  相似文献   
73.
BackgroundScrub typhus (ST) is a life-threatening infectious disease if appropriate treatment is unavailable. Large discrepancy of clinical severity of ST patients was reported among age groups, and the underlying risk factors for severe disease are unclear.MethodsClinical and epidemiological data of ST patients were collected in 55 surveillance hospitals located in Guangzhou City, China, from 2012 to 2018. Severe prognosis and related factors were determined and compared between pediatric and elderly patients.ResultsA total of 2,074 ST patients including 209 pediatric patients and 1,865 elderly patients were included, with a comparable disease severity rate of 11.0% (95% CI 7.1%–16.1%) and 10.3% (95% CI 9.0%–11.8%). Different frequencies of clinical characteristics including lymphadenopathy, skin rash, enlarged tonsils, etc. were observed between pediatric and elderly patients. Presence of peripheral edema and decreased hemoglobin were the most important predictors of severe illness in pediatric patients with adjusted ORs by 38.99 (9.96–152.67, p<0.001) and 13.22 (1.54–113.50, p = 0.019), respectively, while presence of dyspnea and increased total bilirubin were the potential determinants of severe disease in elderly patients with adjusted ORs by 11.69 (7.33–18.64, p<0.001) and 3.17 (1.97–5.11, p<0.001), respectively. Compared with pediatric patients, elderly patients were more likely to receive doxycycline (64.8% v.s 9.9%, p<0.001), while less likely to receive azithromycin therapy (5.0% v.s 41.1%, p<0.001).ConclusionThe disease severity rate is comparable between pediatric and elderly ST patients, while different clinical features and laboratory indicators were associated with development of severe complications for pediatric and elderly patients, which is helpful for diagnosis and progress assessment of disease for ST patients.  相似文献   
74.
种群密度与施肥对垂穗披碱草刈割后补偿作用的影响   总被引:22,自引:1,他引:21       下载免费PDF全文
 以甘南亚高山草甸常见牧草垂穗披碱草(Elymus nutans)为对象,通过考察种群密度、施肥与刈割处理等对植物生长和生殖的影响效应,比较了垂穗披碱草在5个密度及2个施肥实验处理条件下对4种刈割处理的补偿性反应特点。结果表明,在所有密度及施肥处理条件下,早期轻度刈割处理 (分蘖期刈割,留茬4 cm) 都有利于植物的补偿作用,后期重度处理 (拔节期刈割,留茬2 cm) 可显著降低植物的地上部分生物量及生殖部分干重 (穗重)。在不施肥情况下,刈割对垂穗披碱草的影响程度随种群密度而加大,在低密度处理中早期轻度刈割的植物发生了超补偿。可以认为,低密度种群中植物具有较多的分蘖是植物在刈割后表现出较高补偿能力的一个重要生物学原因。实验还发现,施肥可提高植物个体的分蘖能力和秆叶再生能力,因而总体上可增强植物的补偿能力,并且在中等密度条件下垂穗披碱草的补偿能力较强,尽管没有发生超补偿现象。不过,施肥主要是有利于植物地上营养器官的补偿,生殖器官的补偿程度较小一些。试验结果对科学管理人工草场具有一定的指导意义。  相似文献   
75.
Sexual conflict in producing and raising offspring is a critical issue in evolutionary ecology research.Individual experience affects their breeding performance,as measured by such traits of provisioning of offspring and engagement in extra-pair copulations,and may cause an imbalance in sexual conflict.Thus,divorce is hypothesized to occur within aged social pairs,irrespective of current reproductive success.This concept was explored in the azure-winged magpie Cyanopica cyanus by investigating the divorce of a social pair and its relationship to their changes in breeding performance with prior experience.Females engaging in extra-pair copulation may intensify sexual conflicts and may be the main reason for divorce.Once divorced,females repairing with an inexperienced male realized higher reproductive success than that repairing with an experienced male;males repairing with an experienced female realized higher reproductive success than that repairing with an inexperienced female.This finding indicates that the fitness consequence of divorce depends on the breeding experience of new mates.Divorced females can obtain more extra-pair copulations,whereas divorced males cannot,when they repair with inexperienced breeders.Divorced females provisioned a brood at lower rates than inexperienced females whereas divorced males had no such difference.It appears that divorced females can obtain an advantage in sexual conflicts with inexperienced mates in future reproduction.Consequently,females are probably more active than males in divorcing their aged mates so as to select an inexperienced male as a new mate.Azure-winged magpies thus provide novel insights into the implicaticns of sexual conflict in birds.  相似文献   
76.
Four new compounds, 3-(4-hydroxy-3,5-dimethoxyphenyl)propyl formate (1), 2,6-dimethoxy-4-[(1S)-3-methoxypropyl]phenol (2), (1R,2R)-4-[(3R)-3-hydroxybutyl]-3,3,5-trimethylcyclohex-4-ene-1,2-diol (3), and (1S,3R,3aR,6S,7S,9aR)-decahydro-1-(hydroxymethyl)-1,7-dimethyl-3a,7-methano-3aH-cyclopentacyclooctene (4) were isolated from the leaves of Acer truncatum, together with twelve known compounds. Their structures were elucidated on the basis of extensive spectroscopic techniques. The absolute configuration of compound 3 was established by the modified Mosher's method. All compounds were evaluated for antibacterial activities.  相似文献   
77.
Xie BB  Liu HY  Ni W  Chen CX  Lü Y  Wu L  Zheng QT 《化学与生物多样性》2006,3(11):1211-1218
Five new steroids, including the four new steroidal saponins ypsilandroside B (1), ypsilandroside A (2), isoypsilandroside A (4), and isoypsilandroside B (5), as well as the new steroidal sapogenin isoypsilandrogenin (3), were isolated from the whole plant of Ypsilandra thibetica Franch. Their structures were determined on the basis of spectroscopic analyses, including extensive 2D-NMR techniques. The structure and relative configuration of ypsilandroside B (=(3beta,12alpha,25R)-3-[(alpha-L-rhamnopyranosyl-(1-->2)-beta-D-apiofuranosyl)oxy]spirost-5-ene-12,27-diol; 1) was unequivocally determined by single-crystal X-ray diffraction. The antifungal and antibacterial activities of 1-5 towards various types of fungi and bacteria are reported.  相似文献   
78.
[目的]明确白星花金龟Protaetia brevitarsis Lewis聚集信息素的有效成分,为白星花金龟的绿色防控提供支持.[方法]通过动态顶空法收集白星花金龟雌虫、雄虫和雌雄虫混合挥发物,用气相色谱-质谱(Gas chromatography-mass spectrometry,GC-MS)联用技术对收集的挥发物进行分析鉴定,并利用触角电位(Electroantennogram,EAG)仪和Y型嗅觉仪测定白星花金龟对8种化合物的触角电位和行为选择反应.[结果]白星花金龟雌虫、雄虫和雌雄虫混合挥发物中皆鉴定出8类15种化合物,包括6种烷烃类、2种酚类、2种芳香烃类、1种烯类、1种吡啶类、1种胺类、1种醇类和1种酮类.EAG试验结果表明,白星花金龟对8种化合物都有EAG反应,且不同挥发物间、同种挥发物不同浓度间的EAG反应存在差异.白星花金龟对蒎烷胺、3,4-二甲基-6-乙基苯酚、2,3-二甲基苯乙酮和2,6,10,14-四甲基十七烷4种挥发物的EAG反应相对值在1μg/μtL时达到最大,对萘、苯并噻唑、百里酚和正十四烷4种挥发物的EAG反应相对值在10 μtg/μtL时达到最大.行为选择反应表明,白星花金龟雌成虫、雄成虫对2,3-二甲基苯乙酮有明显趋向性,选择反应率大于70%,对2,6,10,14-四甲基十七烷、萘、苯并噻唑、百里酚和正十四烷5种物质均表现出显著或极显著的驱避效果,对3,4-二甲基-6-乙基苯酚和蒎烷胺表现出了性别上的差异,雄虫对3,4-二甲基-6-乙基苯酚表现出显著的趋向性,对蒎烷胺表现出显著的驱避性,而雌虫对这2种挥发物却无明显反应.[结论]2,3-二甲基苯乙酮对白星花金龟雌成虫、雄成虫有明显的引诱效果,2,6,10,14-四甲基十七烷、萘、苯并噻唑、正十四烷和百里酚有较强的驱避作用,推测2,3-二甲基苯乙酮是白星花金龟聚集信息素的有效组分.  相似文献   
79.
目的:以感受器相互作用分子(STIMI)为报告基因优化悬浮培养的二甲基亚砜(DMSO)诱导分化的HL-60细胞的电穿孔转染条件。方法:通过控制电压、电容、电阻、细胞状态等转染条件,采用不同条件组合后用电穿孔法将靶向STIMI的siRNA转入悬浮培养的dHL-60细胞,用荧光显微镜观察转染率,蛋白免疫印记方法检测干扰效率。结果:适当提高电压能提高悬浮培养的dHL-60细胞的转染效率,细胞状态不同干扰效率有所差异,DMSO诱导4d的dHL-60细胞在电压295V、电容1180μF、电阻5000的条件下转入STIMI siRNA系列并得到最大干扰效率(约60%)。结论:针对dHL-60细胞这种比较特殊的细胞系来说,电穿孔转染法是一种较好的基因转染方法,通过优化其转染条件,可以提高其对dHL-60细胞的SiRNA干扰效率。  相似文献   
80.
盐皮质激素的非基因组作用及其机制   总被引:1,自引:0,他引:1  
盐皮质激素(以醛固酮为代表)是调节机体水盐代谢的重要甾体激素,有着重要的生理、病理功能,阐明其作用机制具有重要的基础和临床意义.现已明确,醛固酮的作用有经典的基因组作用和快速的非基因组作用.关于前者,人们已有较多的评述,本文旨在综述近年来有关醛固酮非基因组作用及其可能分子机制的研究进展.目前的研究表明,醛固酮既可能通过膜受体,又可能通过核受体发挥快速非基因组作用.非基因组作用可以激活细胞内多种信号转导通路.另外,非基因组作用与基因组作用之间还存在整合和交互对话的途径.  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