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   15篇
  国内免费   1篇
  完全免费   12篇
  2020年   1篇
  2019年   1篇
  2018年   1篇
  2017年   1篇
  2016年   3篇
  2015年   3篇
  2014年   3篇
  2013年   1篇
  2012年   2篇
  2011年   2篇
  2009年   1篇
  2008年   1篇
  2007年   1篇
  2006年   1篇
  2005年   3篇
  2003年   1篇
  2002年   1篇
  1995年   1篇
排序方式: 共有28条查询结果,搜索用时 78 毫秒
1.
Massive loss of cardiac myocytes after myocardial infarction (MI) is a common cause of heart failure. The present study was designed to investigate the improvement of cardiac function in MI rats after embryonic stem (ES) cell transplantation. MI in rats was induced by ligation of the left anterior descending coronary artery. Cultured ES cells used for cell transplantation were transfected with the marker green fluorescent protein (GFP). Animals in the treated group received intramyocardial injection of ES cells in injured myocardium. Compared with the MI control group injected with an equivalent volume of the cell-free medium, cardiac function in ES cell-implanted MI animals was significantly improved 6 wk after cell transplantation. The characteristic phenotype of engrafted ES cells was identified in implanted myocardium by strong positive staining to sarcomeric alpha-actin, cardiac alpha-myosin heavy chain, and troponin I. GFP-positive cells in myocardium sectioned from MI hearts confirmed the survival and differentiation of engrafted cells. In addition, single cells isolated from cell-transplanted MI hearts showed rod-shaped GFP-positive myocytes with typical striations. The present data demonstrate that ES cell transplantation is a feasible and novel approach to improve ventricular function in infarcted failing hearts.  相似文献
2.
内蒙古典型草原生态系统健康评价   总被引:6,自引:1,他引:5       下载免费PDF全文
以草原生态系统中的植物-土壤-大气界面的关键生态过程为基础,结合典型草原生态系统的群落特征及其退化演替模式,并考虑水分因子的限制作用,在确定生态系统健康评价模式(参照)系统和基况评价指标的同时,建立了典型草原生态系统健康评价的CVOR综合指数的计算模型和方法.通过分析放牧压力和围封保育对内蒙古典型草原生态系统健康的影响,检验了CVOR综合指数的可行性,可为草原生态系统健康管理提供一个综合、简单、准确、宜行的评价方法.  相似文献
3.
Ezrin is a member of ezrin, radixin, moesin (ERM) protein family that links F-actin to membranes. The NH2- and COOH-terminal association domains of ERM proteins, known respectively as N-ERMAD and C-ERMAD, participate in interactions with membrane proteins and F-actin, and intramolecular and intermolecular interactions within and among ERM proteins. In gastric parietal cells, ezrin is heavily represented on the apical membrane and is associated with cell activation. Ezrin-ezrin interactions are presumably involved in functional regulation of ezrin and thus became a subject of our study. Fluorescence resonance energy transfer (FRET) was examined with cyan fluorescent protein (CFP)- and yellow fluorescent protein (YFP)-tagged ezrin incorporated into HeLa cells and primary cultures of parietal cells. Constructs included YFP at the NH2 terminus of ezrin (YFP-Ez), CFP at the COOH terminus of ezrin (Ez-CFP), and double-labeled ezrin (N-YFP-ezrin-CFP-C). FRET was probed using fluorescence microscopy and spectrofluorometry. Evidence of ezrin oligomer formation was found using FRET in cells coexpressing Ez-CFP and YFP-Ez and by performing coimmunoprecipitation of endogenous ezrin with fluorescent protein-tagged ezrin. Thus intermolecular NH2- and COOH-terminal association domain (N-C) binding in vivo is consistent with the findings of earlier in vitro studies. After the ezrin oligomers were separated from monomers, FRET was observed in both forms, indicating intramolecular and intermolecular N-C binding. When the distribution of native ezrin as oligomers vs. monomers was examined in resting and maximally stimulated parietal cells, a shift of ezrin oligomers to the monomeric form was correlated with stimulation, suggesting that ezrin oligomers are the membrane-bound dormant form in gastric parietal cells. fluorescence resonance energy transfer; acid secretion; radixin; moesin; cytoskeleton; ERM family  相似文献
4.
不同演替阶段褐沙蒿种群特征研究   总被引:3,自引:1,他引:2  
以生长于内蒙古浑善达克沙地上的特有种——褐沙蒿种群为对象,对处于植被演替不同阶段(流动沙地、半流动沙地、半固定沙地和固定沙地生境)的褐沙蒿种群生长状态和及其生境特征进行了观测。结果表明,随着沙地表层的逐步固定,土层0~5cm的土壤含水量在逐渐增加,雨后各样地内土壤含水量的最大值都出现在0~5cm表土层;土壤有机质、全氮含量在各样地间差异极为显著,并表现出随着沙地的固定逐渐增加的趋势。褐沙蒿基株数、构件的枝条数在各演替阶段间虽无显著的差异,但随土壤基质的改变,反映种群生态功能的特征,如冠幅、生物量、生殖配额等特征在各样地间却有显著差异,且表现出随着沙地的固定而下降的趋势。在此基础上尝试性地提出了褐沙蒿种群综合活力指数(CVI),试图以一个综合的指标来表示褐沙蒿种群在不同衰退阶段生长状态上的差异。分析表明,随着沙地的逐步固定,褐沙蒿种群综合活力指数在各演替阶段差异极为显著,其值从流动沙地的0.63显著下降到固定沙地的0.38,并与土壤有机质含量、全氮量之间表现出显著的负相关性。  相似文献
5.
梨枣花果期耗水规律及其与茎直径变化的相关分析   总被引:2,自引:0,他引:2       下载免费PDF全文
设置4个水分处理,研究了4年生梨枣2010年及2011年花果期不同供水条件下土壤水分动态和耗水规律,分析了梨枣日耗水量与茎直径变化间的相关性,建立回归模型.结果表明:(1)2a内各处理梨枣耗水量随土壤供水量的增加而增大,其日耗水量最大值均出现在灌水后1周内;各处理果实膨大期日耗水强度大于开花坐果期.(2)2a内各处理茎直径日变化平均值(MTD)、茎直径日最大值(MXTD)均符合Logistic函数关系,MXTD与MTD在表征梨枣茎秆生长规律方面效果一致,各处理茎直径变化指标(MTD、MXTD)增长率因水分处理的不同而存在差异.(3)高水分(T1处理)条件下茎直径变化指标(MTD、MXTD、MDS(茎直径日最大收缩量)、DG(茎直径日生长量))在表征枣树耗水状况方面不敏感;在低水分(T4处理)条件下,日耗水量与茎直径日最大收缩量(MDS)相关系数较其他3个茎直径变化指标(MTD、MXTD、DG)高且达极显著水平,说明MDS能够更好的表征低水分处理的梨枣耗水规律.在此基础上建立耗水量与茎直径变化回归模型,为评价梨枣耗水状况提供依据.  相似文献
6.
陈彪  陈立欣  刘清泉  刘平生  张志强 《生态学报》2015,35(15):5076-5084
作为我国半干旱地区重要的造林绿化树种之一,樟子松在城市林业建设中被广泛使用,研究樟子松在半干旱地区城市环境下的蒸腾耗水及其环境响应对于城市森林建设具有重要的理论意义和应用价值。从2012年8月至10月,以位于内蒙古呼和浩特市树木园内的30年生樟子松为研究对象,按照其径阶分布,选定8株样木,采用热扩散探针法对其树干边材液流进行了连续动态监测,并采用小型自动气象站和土壤水分传感器同步连续测定小气候因子与土壤含水量动态变化。结果表明:在不同天气条件下,樟子松树干液流密度日变化存在差异,晴天时液流密度曲线表现为单峰曲线,且液流密度较大,阴天与雨天液流密度相对较小;液流密度的大小与供试树木胸径无显著相关关系(P>0.05);太阳辐射(r= 0.731, P<0.01)和大气饱和水汽压亏缺(VPD) (r= 0.877, P<0.01)是影响樟子松蒸腾的主要因子,风速与液流密度极显著相关(P<0.01),但相关系数仅为0.518;土壤水分并未显著影响液流密度(r =-0.071, P>0.05)。以太阳辐射Ra、VPD作为自变量建立的模型能够分别解释樟子松68%、71%的液流变化。  相似文献
7.
芦苇、香蒲和藨草3种挺水植物的养分吸收动力学   总被引:1,自引:0,他引:1       下载免费PDF全文
采用常规耗竭法研究了浅水富营养化湖泊——乌梁素海湖滨植被带3种挺水植物芦苇、香蒲和藨草对H2PO4-、NH4+、NO3-的吸收动力学特征及差异。结果表明:3种挺水植物吸收H2PO4-时,藨草的吸收速率显著大于芦苇和香蒲,但三者对低浓度H2PO4-的适应能力均无显著差异;藨草对NH4+和NO3-的吸收速率均显著大于芦苇和香蒲,且在低浓度NO3-环境下仍能吸收该离子,但对低浓度NH4+环境的适应能力较差;与藨草相比,香蒲对NH4+的亲和力最强,吸收低浓度NH4+的效果最好。3种植物对NH4+的吸收能力均大于NO3-。挺水植物的养分吸收特征具有物种特异性并受根系结构的影响。利用植物的养分吸收特征,在富营养化湖泊生态修复中适宜用藨草治理含高浓度H2PO4-,NH4+和NO3-的水体,修复到一定程度后再种植香蒲来维持水质。  相似文献
8.
Huang G  Wang L  Liu Y 《The EMBO journal》2006,25(22):5349-5357
Circadian singularity behavior (also called suppression of circadian rhythms) is a phenomenon characterized by the abolishment of circadian rhythmicities by a critical stimulus. Here we demonstrate that both temperature step up and light pulse, stimuli that activate the expression of the Neurospora circadian clock gene frequency (frq), can trigger singularity behavior in this organism. The arrhythmicity is transient and is followed by the resumption of rhythm in randomly distributed phases. In addition, we show that induction of FRQ expression alone can trigger singularity behavior, indicating that FRQ is a state variable of the Neurospora circadian oscillator. Furthermore, mutations of frq lead to changes in the amplitude of FRQ oscillation, which determines the sensitivity of the clock to phase-resetting cues. Our results further suggest that the singularity behavior is due to the loss of rhythm in all cells. Together, these data suggest that the singularity behavior is due to a circadian negative feedback loop driven to a steady state after the critical treatment. After the initial arrhythmicity, cell populations are then desynchronized.  相似文献
9.
本文采用定量PCR方法观察了慢性乙型肝炎患者HBV-DNA的复制水平。结果表明在HBeAg阳性患者血清HBV-DNA检出率和水平显著高于HBeAg阴性患者(P<0.01);血清HBV-DNA水平的高低与ALT异常情况未发现有相关性。  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