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   152篇
  免费   8篇
  2022年   2篇
  2021年   4篇
  2020年   7篇
  2019年   4篇
  2018年   6篇
  2017年   7篇
  2016年   6篇
  2015年   7篇
  2014年   14篇
  2013年   8篇
  2012年   12篇
  2011年   12篇
  2010年   7篇
  2009年   3篇
  2008年   2篇
  2007年   14篇
  2006年   7篇
  2005年   12篇
  2004年   6篇
  2003年   11篇
  2002年   7篇
  2001年   2篇
排序方式: 共有160条查询结果,搜索用时 109 毫秒
1.
Knowledge on transport and deposition of fine particulate organic matter (FPOM) from reservoir dams is increasingly required for habitat management and restoration of dam tailwater ecosystems. Variations in the transport distance of FPOM, however, have never been studied well, particularly in relation to channel morphology, due to channel size restrictions of artificial tracers such as corn pollen when applied to larger river channels. This study aims to show the relations between FPOM retention efficiency and channel morphology in dam tailwaters using lentic plankters as tracers. We estimated the mean transport distance, S p, by calculating downstream reduction ratios of lentic tracer plankters and calculated the deposition velocity, v dep. Suspended FPOM samples were collected in tailwaters of two river channels below reservoir dams and two artificial canals below Lake Biwa in the Yodo River system. The longest S p (19.2 km) and the shortest one (2.2 km) were recorded in the deep canal and shallow canal, respectively, showing a positive correlation with channel hydraulic radius. The values of v dep were 4.7–6.4 times higher in river channels than in artificial canals. These results indicate that increasing complexity of bed morphology can minimize S p, whereas bed degradation and armored bed materials may lead to increased S p. Advantages of lentic plankters as tracers for estimating distance ranges of reservoir dam impact on river ecosystems are also discussed.  相似文献   
2.
3.
The dysfunction of left atrial appendage (LAA) is prone to form thrombus when atrial fibrillation (AF) sustained more than 48 h. Traditional 2D-TEE (transesophageal echocardiography) can not accurate evaluate the function of LAA. The purpose of this study is to analyze the relationship of LAA function parameters and thrombus formation in patients with non-valvular atrial fibrillation (NVAF) by real-time three-dimensional transesophageal echocardiography (RT-3D-TEE). High risk patients can be identified according to the characteristics of ultrasonic index in patients with left atrial appendage thrombosis, which has important clinical value and significance in the risk assessment, guiding treatment and judging prognosis. We examined the relationship between the echocardiographic parameters of LAA function and the incidence of thrombus in 102 NVAF patients. They underwent RT-3D-TEE and left atrial appendage thrombus (LAAT)/severe spontaneous echocardiographic contrast (SSEC) was found in 67 patients (thrombus group) but absent in the remaining 35 patients (non-thrombus group). After measured by QLAB software, the LAA functional parameters were significantly associated with LAAT/SEC formation. Univariate analysis indicated that AF time, LAD, LVEF, LAA-OAmax, LAAVmax, LAAVI and LAAEF demonstrated a positive association (P < 0.05). However, logistic regression analysis identified that AF time (OR:1.73, P < 0.05)、LAAEF (OR:4.09, P < 0.01)and LAAVI (OR:3.28, P < 0.01) were independent predictors of LAAT/SSEC. In patients with nonvalvular atrial fibrillation, echocardiographic parameters of LAA function are significantly associated with LAAT/SSEC.  相似文献   
4.
As the importance of personalized therapeutics in aggressive papillary thyroid cancer (PTC) increases, accurate risk stratification is required. To develop a novel prognostic scoring system for patients with PTC (n = 455), we used mRNA expression and clinical data from The Cancer Genome Atlas. We performed variable selection using Network‐Regularized high‐dimensional Cox‐regression with gene network from pathway databases. The risk score was calculated using a linear combination of regression coefficients and mRNA expressions. The risk score and clinical variables were assessed by several survival analyses. The risk score showed high discriminatory power for the prediction of event‐free survival as well as the presence of metastasis. In multivariate analysis, the risk score and presence of metastasis were significant risk factors among the clinical variables that were examined together. In the current study, we developed a risk scoring system that will help to identify suitable therapeutic options for PTC.  相似文献   
5.
The antigenotoxic effects of estrogen and genistein (isoflavones) were compared by measuring the degree of protection against plasmid DNA strand breakage induced by peroxyl free radicals using the DNA strand scission assay with pBR322 DNA. Isoflavones decreased DNA strand breakage by AAPH radical treatment at the all of three concentrations tested (0.5, 1.0, 1.5 microg/ml) with the range of 89.5% to 99.6%. Compared to genistein, estrogen was not as effective as genistein showing 46.9% to 29.6% protection, and this protective effect was decreased as estrogen concentrations increased from 0.1 to 0.3 microg/ml. DNA ladder experiments showed that genistein induced apoptosis in cultured cell lines, whereas estrogen did not induce any apoptosis. The effects of cell signal trandsduction protein expression patterns were compared between estrogen and genistein. The increased expression of cyclin B1 by estrogen was tampered by genistein at the highest concentration. Antigenotoxic and antiproliferative effects of genistein shown in this study support the hypothesis that it has a chemopreventive effect against particular types of cancers.  相似文献   
6.
Acute gastric anisakiasis with multiple anisakid larvae infection is reported. A 68-year-old woman residing in Busan, Korea, had epigastric pain with severe vomiting about 5 hours after eating raw anchovies. Four nematode larvae penetrating the gastric mucosae in the great curvature of the middle body and fundus were found and removed during gastro-endoscopic examination. Another one thread-like moving larva was found in the great curvature of upper body on the following day. On the basis of their morphology, the worms were identified as the 3rd stage larvae of Anisakis simplex. This case is acute gastric anisakiasis provoking severe clinical problems by the multiple infection and the greatest number of anisakid larvae found in a patient in Korea.  相似文献   
7.
Suk K  Kim SY  Leem K  Kim YO  Park SY  Hur J  Baek J  Lee KJ  Zheng HZ  Kim H 《Life sciences》2002,70(21):2467-2480
In traditional Oriental medicine, Uncaria rhynchophylla has been used to lower blood pressure and to relieve various neurological symptoms. However, scientific evidence related to its effectiveness or precise modes of action has not been available. Thus, in the current study, we evaluated neuroprotective effects of U. rhynchophylla after transient global ischemia using 4-vessel occlusion model in rats. Methanol extract of U. rhynchophylla administered intraperitoneally (100-1000 mg/kg at 0 and 90 min after reperfusion) significantly protected hippocampal CA1 neurons against 10 min transient forebrain ischemia. Measurement of neuronal cell density in CA1 region at 7 days after ischemia by Nissl staining revealed more than 70% protection in U. rhynchophylla-treated rats compared to saline-treated animals. In U. rhynchophylla-treated animals, induction of cyclooxygenase-2 in hippocampus at 24 hr after ischemia was significantly inhibited at both mRNA and protein levels. Furthermore, U. rhynchophylla extract inhibited TNF-alpha and nitric oxide production in BV-2 mouse microglial cells in vitro. These anti-inflammatory actions of U. rhynchophylla extract may contribute to its neuroprotective effects.  相似文献   
8.
To examine the effect of two types of resistant starch on blood glucose and insulin levels, colonic events, hypolipidemic actions and humoral immune responses, Sprague-Dawley streptozotocin-induced diabetic rats were fed diet containing resistant starch from corn or rice. The marked body weight loss by inducing diabetes was not recovered by feeding resistant starch, even though there are no differences in food intakes compared to the non-diabetic control rats. No significant effect of resistant starch feeding on blood glucose and insulin was found. Even though the length of small intestines, and cecum, colon and rectum together with the tissue weight of cecum were not affected by feeding resistant starch, the intestinal transit time was markedly shortened by both types of resistant starch and resistant starch from corn had a more pronounced effect. The short chain fatty acids in the intestinal contents did not appear to be different among the groups. Nonetheless, both of resistant starch from corn and rice significantly lowered plasma total lipid and cholesterol concentrations compared to the diabetic control. The total liver cholesterol lowering effect was observed with resistant starch from rice. Neither immunoglobulin G nor C(3) were influenced by resistant starch.  相似文献   
9.
MicroRNA (miRNA) is an endogenous non-coding RNA species that either inhibits RNA translation or promotes degradation of target mRNAs. miRNAs often regulate cellular signaling by targeting multiple genes within the pathways. In the present study, using Gene Set Analysis, a useful bioinformatics tool to identify miRNAs with multiple target genes in the same pathways, we identified miR-185 as a key candidate regulator of cardiac hypertrophy. Using a mouse model, we found that miR-185 was significantly down-regulated in myocardial cells during cardiac hypertrophy induced by transverse aortic constriction. To confirm that miR-185 is an anti-hypertrophic miRNA, genetic manipulation studies such as overexpression and knock-down of miR-185 in neonatal rat ventricular myocytes were conducted. The results showed that up-regulation of miR-185 led to anti-hypertrophic effects, while down-regulation led to pro-hypertrophic effects, suggesting that miR-185 has an anti-hypertrophic role in the heart. Our study further identified Camk2d, Ncx1, and Nfatc3 as direct targets of miR-185. The activity of Nuclear Factor of Activated T-cell (NFAT) and calcium/calmodulin-dependent protein kinase II delta (CaMKIIδ) was negatively regulated by miR-185 as assessed by NFAT-luciferase activity and western blotting. The expression of phospho-phospholamban (Thr-17), a marker of CaMKIIδ activity, was also significantly reduced by miR-185. In conclusion, miR-185 effectively blocked cardiac hypertrophy signaling through multiple targets, rendering it a potential drug target for diseases such as heart failure.  相似文献   
10.
Although the various biological roles of thymosin β4 (Tβ4) have been studied widely, the effect of Tβ4 and Tβ4-expressing cells in the liver remains unclear. Therefore, we investigated the expression and function of Tβ4 in chronically damaged livers. CCl4 was injected into male mice to induce a model of chronic liver disease. Mice were sacrificed at 6 and 10 weeks after CCl4 treatment, and the livers were collected for biochemical analysis. The activated LX-2, human hepatic stellate cell (HSC) line, were transfected with Tβ4-specific siRNA and activation markers of HSCs were examined. Compared to HepG2, higher expression of Tβ4 in RNA and protein levels was detected in the activated LX-2. In addition, Tβ4 was up-regulated in human liver with advanced liver fibrosis. The expression of Tβ4 increased during mouse HSC activation. Tβ4 was also up-regulated and Tβ4-positive cells were co-localized with α-smooth muscle actin (α-SMA) in the livers of CCl4-treated mice, whereas such cells were rarely detected in the livers of corn-oil treated mice. The suppression of Tβ4 in LX-2 cells by siRNA induced the down-regulation of HSC activation-related genes, tgf-β, α-sma, collagen, and vimentin, and up-regulation of HSC inactivation markers, ppar-γ and gfap. Immunofluorescent staining detected rare co-expressing cells with Tβ4 and α-SMA in Tβ4 siRNA-transfected cells. In addition, cytoplasmic lipid droplets were observed in Tβ4 siRNA-treated cells. These results demonstrate that activated HSCs expressed Tβ4 in chronically damaged livers, and this endogenous expression of Tβ4 influenced HSC activation, indicating that Tβ4 might contribute to liver fibrosis by regulating HSC activation.  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