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   278篇
  免费   24篇
  2023年   1篇
  2022年   11篇
  2021年   14篇
  2020年   12篇
  2019年   21篇
  2018年   19篇
  2017年   15篇
  2016年   16篇
  2015年   14篇
  2014年   25篇
  2013年   36篇
  2012年   25篇
  2011年   22篇
  2010年   10篇
  2009年   9篇
  2008年   15篇
  2007年   11篇
  2006年   5篇
  2005年   2篇
  2004年   2篇
  2003年   4篇
  2002年   6篇
  2001年   2篇
  2000年   1篇
  1999年   2篇
  1997年   1篇
  1995年   1篇
排序方式: 共有302条查询结果,搜索用时 15 毫秒
131.
Previous research has shown that interacting with natural environments vs. more urban or built environments can have salubrious psychological effects, such as improvements in attention and memory. Even viewing pictures of nature vs. pictures of built environments can produce similar effects. A major question is: What is it about natural environments that produces these benefits? Problematically, there are many differing qualities between natural and urban environments, making it difficult to narrow down the dimensions of nature that may lead to these benefits. In this study, we set out to uncover visual features that related to individuals'' perceptions of naturalness in images. We quantified naturalness in two ways: first, implicitly using a multidimensional scaling analysis and second, explicitly with direct naturalness ratings. Features that seemed most related to perceptions of naturalness were related to the density of contrast changes in the scene, the density of straight lines in the scene, the average color saturation in the scene and the average hue diversity in the scene. We then trained a machine-learning algorithm to predict whether a scene was perceived as being natural or not based on these low-level visual features and we could do so with 81% accuracy. As such we were able to reliably predict subjective perceptions of naturalness with objective low-level visual features. Our results can be used in future studies to determine if these features, which are related to naturalness, may also lead to the benefits attained from interacting with nature.  相似文献   
132.
Among the progressive neurodegenerative disorders, Parkinson's disease (PD) is the second most common. Different factors have critical role in pathophysiology of PD such as apoptosis pathways, inflammatory cytokines, oxidative stress, and neurotransmitters and its receptors abnormalities. Acupuncture and electroacupuncture were considered as nondrug therapies for PD. Although numerous studies has been conducted for assessing the mechanism underlying electroacupuncture and acupuncture, various principal aspects of these treatment procedures remain not well-known. There have also been few investigations on the molecular mechanism of acupuncture and electroacupuncture therapy effects in PD. This review evaluates the effects of electroacupuncture and acupuncture on the molecular mechanism in PD.  相似文献   
133.
The present study was designed to evaluate possible protective effects of purified histaminase from Lathyrus sativus L. seedling on the myocardial injuries upon isoprenaline-induced myocardial infarction in rats. In this regard, blood histamine concentration, creatine kinase-MB (CK-MB) activity, antioxidant status, and histopathological changes of the hearts were measured. A total of 40 adult male Sprague–Dawley rats were divided into five equal groups and treated in the following order: control (normal saline), isoprenaline (isoproterenol 110 mg/kg BW), Isopren.-H1 (isoprenaline plus histaminase 80 U/kg BW), Isopren.-H2 (isoprenaline plus histaminase 120 U/kg BW), and Isopren.-H3 (isoprenaline plus histaminase 160 U/kg BW). Myocardial infarction was manifested by a significant elevation in the level of CK-MB and histopathological findings in isoprenaline group when compared to controls. In contrast, histaminase pretreatment at dose of 160 U/kg prevented isoprenaline-induced histamine release and significantly decreased CK-MB activity as well as histopathological changes in Isopren.-H3 group. A significant increase in the catalase (CAT) and superoxide dismutase (SOD) activities was also observed by histaminase treatment in Isopren.-H2 and Isopren.-H3 groups. Although the activity of glutathione peroxidase (GPx) increased significantly to suppress oxidative stress in isoprenaline group, it was not able to prevent lipid peroxidation (as shown by TBARS concentration) in the heart of rats. In conclusion, the plant-originated histaminase presented as a promising enzyme with antioxidant properties against histamine release and myocardial infarction in rats, and it seems be a suitable therapeutic agent for future clinical trials in humans.  相似文献   
134.
A low relative area change (RAC) of the proximal pulmonary artery (PA) over the cardiac cycle is a good predictor of mortality from right ventricular failure in patients with pulmonary hypertension (PH). The relationship between RAC and local mechanical properties of arteries, which are known to stiffen in acute and chronic PH, is not clear, however. In this study, we estimated elastic moduli of three PAs (MPA, LPA and RPA: main, left and right PAs) at the physiological state using mechanical testing data and correlated these estimated elastic moduli to RAC measured in vivo with both phase-contrast magnetic resonance imaging (PC-MRI) and M-mode echocardiography (on RPA only). We did so using data from a canine model of acute PH due to embolization to assess the sensitivity of RAC to changes in elastic modulus in the absence of chronic PH-induced arterial remodeling. We found that elastic modulus increased with embolization-induced PH, presumably a consequence of increased collagen engagement, which corresponds well to decreased RAC. Furthermore, RAC was inversely related to elastic modulus. Finally, we found MRI and echocardiography yielded comparable estimates of RAC. We conclude that RAC of proximal PAs can be obtained from either MRI or echocardiography and a change in RAC indicates a change in elastic modulus of proximal PAs detectable even in the absence of chronic PH-induced arterial remodeling. The correlation between RAC and elastic modulus of proximal PAs may be useful for prognoses and to monitor the effects of therapeutic interventions in patients with PH.  相似文献   
135.
Tomato leaf curl virus-Australia (ToLCV) C4 protein has been shown to be associated with virus pathogenesis. Here, we demonstrate that C4 acts as a suppressor of gene silencing. To understand the multifunctional role of C4, a novel shaggy-like kinase (SlSK) from tomato, which interacts with ToLCV C4 in a yeast two-hybrid assay, was isolated and interaction between these proteins was confirmed in vitro and in planta. Using deletion analysis of C4, a 12 amino acid region in the C-terminal part of C4 was identified which was shown to be essential for its binding to SlSK. We further demonstrate that this region is not only important for the interaction of C4 with SlSK, but is also required for C4 function to suppress gene silencing activity and to induce virus symptoms in a PVX system. The potential significance of ToLCV C4 and SlSK interaction is discussed.  相似文献   
136.
The evolutionary conserved family of heat shock proteins (HSP) is responsible for protecting cells against different types of stress, including oxidative stress. Although the levels of HSPs can be readily measured in blood serum, the levels of HSP70 in patients with different durations of diabetes have not been studied before. We quantified serum HSP70 levels in a healthy control group (n = 36) and two groups of type 2 diabetic patients, defined as newly diagnosed diabetes (n = 36) and patients with diabetes duration of more than 5 years (n = 37). The clinical characteristics and biochemical parameters were evaluated in the studied population. We found that serum HSP70 levels were significantly higher in patients with diabetes when compared with controls (p < 0.001) and it was higher in patients with disease for more than 5 years than in newly diagnosed patients (p < 0.001). Serum HSP70 was inversely correlated with fasting blood sugar in patients with diabetes for more than 5 years (r = −0.500, p = 0.002), positively correlated with the history of hypertension in newly diagnosed patients (p < 0.001), and positively correlated with age in patients with diabetes (r = 0.531, p = 0.001). Serum level of HSP70 is significantly higher in patients with diabetes and correlates with the duration of disease. Higher HSP70 in prolonged diabetes versus newly diagnosed diabetes may be an indicator of metabolic derangement in the course of diabetes.  相似文献   
137.
138.
139.
The etiology of radiation-induced cardiovascular disease (CVD) after chronic exposure to low doses of ionizing radiation is only marginally understood. We have previously shown that a chronic low-dose rate exposure (4.1 mGy/h) causes human umbilical vein endothelial cells (HUVECs) to prematurely senesce. We now show that a dose rate of 2.4 mGy/h is also able to trigger premature senescence in HUVECs, primarily indicated by a loss of growth potential and the appearance of the senescence-associated markers ß-galactosidase (SA-ß-gal) and p21. In contrast, a lower dose rate of 1.4 mGy/h was not sufficient to inhibit cellular growth or increase SA-ß-gal-staining despite an increased expression of p21. We used reverse phase protein arrays and triplex Isotope Coded Protein Labeling with LC-ESI-MS/MS to study the proteomic changes associated with chronic radiation-induced senescence. Both technologies identified inactivation of the PI3K/Akt/mTOR pathway accompanying premature senescence. In addition, expression of proteins involved in cytoskeletal structure and EIF2 signaling was reduced. Age-related diseases such as CVD have been previously associated with increased endothelial cell senescence. We postulate that a similar endothelial aging may contribute to the increased rate of CVD seen in populations chronically exposed to low-dose-rate radiation.  相似文献   
140.
High doses of ionising radiation significantly increase the risk of cardiovascular disease (CVD), the vascular endothelium representing one of the main targets. Whether radiation doses lower than 500 mGy induce cardiovascular damage is controversial. The aim of this study was to investigate radiation-induced expression changes on protein and microRNA (miRNA) level in primary human coronary artery endothelial cells after a single 200 mGy radiation dose (Co-60). Using a multiplex gel-based proteomics technology (2D-DIGE), we identified 28 deregulated proteins showing more than ±1.5-fold expression change in comparison with non-exposed cells. A great majority of the proteins showed up-regulation. Bioinformatics analysis indicated “cellular assembly and organisation, cellular function and maintenance and molecular transport” as the most significant radiation-responsive network. Caspase-3, a central regulator of this network, was confirmed to be up-regulated using immunoblotting. We also analysed radiation-induced alterations in the level of six miRNAs known to play a role either in CVD or in radiation response. The expression of miR-21 and miR-146b showed significant radiation-induced deregulation. Using miRNA target prediction, three proteins found differentially expressed in this study were identified as putative candidates for miR-21 regulation. A negative correlation was observed between miR-21 levels and the predicted target proteins, desmoglein 1, phosphoglucomutase and target of Myb protein. This study shows for the first time that a low-dose exposure has a significant impact on miRNA expression that is directly related to protein expression alterations. The data presented here may facilitate the discovery of low-dose biomarkers of radiation-induced cardiovascular damage.  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