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   161篇
  免费   8篇
  2023年   2篇
  2022年   2篇
  2021年   11篇
  2020年   6篇
  2019年   4篇
  2018年   5篇
  2017年   7篇
  2016年   4篇
  2015年   4篇
  2014年   9篇
  2013年   16篇
  2012年   8篇
  2011年   12篇
  2010年   3篇
  2009年   2篇
  2008年   4篇
  2007年   8篇
  2006年   9篇
  2005年   7篇
  2004年   2篇
  2003年   1篇
  2002年   4篇
  2001年   5篇
  2000年   1篇
  1999年   1篇
  1998年   3篇
  1997年   3篇
  1995年   1篇
  1988年   1篇
  1987年   7篇
  1986年   1篇
  1985年   1篇
  1981年   1篇
  1980年   1篇
  1979年   3篇
  1978年   2篇
  1977年   3篇
  1974年   1篇
  1973年   2篇
  1971年   1篇
  1967年   1篇
排序方式: 共有169条查询结果,搜索用时 15 毫秒
1.
The run of elvers of Anguilla anguilla (L) up the Mex canal, Alexandria, Egypt, starts at the end of February and continues until June, with the main bulk of elvers arriving in April and May. Variations in the timing of this run may be attributable to variations in local ecological conditions. The run is affected by meteorological and hydrographic factors. The effects of the latter have been assessed, and a low oxygen content, a pH between 7.7 and 8.0, a chloride content between 2.1 and 2.3 Cl/1 and a temperature between 20 and 25°C have been found to encourage large numbers of elvers to migrate up the fresh water canal. In contrast to previous findings, the results of this study suggest that the mean length of elvers running increases towards the end of the season.  相似文献   
2.
A population of Solea vulgaris was transplanted in 1938 from the Mediterranean to a land locked brackish lake. In 1977, the morphology of these fishes was investigated and a number of measurements made and compared with those of fish caught in the Mediterranean. Among these variations was less vertebrae and fewer dorsal fin rays in the lake soles.  相似文献   
3.
In vitro screening of 17 Alpine lichen species for their inhibitory activity against 5-lipoxygenase, microsomal prostaglandin E2 synthase-1 and nuclear factor kappa B revealed Cetrelia monachorum (Zahlbr.) W.L. Culb. & C.F. Culb. As conceivable source for novel anti-inflammatory compounds. Phytochemical investigation of the ethanolic crude extract resulted in the isolation and identification of 11 constituents, belonging to depsides and derivatives of orsellinic acid, olivetolic acid and olivetol. The two depsides imbricaric acid (4) and perlatolic acid (5) approved dual inhibitory activities on microsomal prostaglandin E2 synthase-1 (IC50 = 1.9 and 0.4 µM, resp.) and on 5-lipoxygenase tested in a cell-based assay (IC50 = 5.3 and 1.8 µM, resp.) and on purified enzyme (IC50 = 3.5 and 0.4 µM, resp.). Additionally, these two main constituents quantified in the extract with 15.22% (4) and 9.10% (5) showed significant inhibition of tumor necrosis factor alpha-induced nuclear factor kappa B activation in luciferase reporter cells with IC50 values of 2.0 and 7.0 µM, respectively. In a murine in vivo model of inflammation, 5 impaired the inflammatory, thioglycollate-induced recruitment of leukocytes to the peritoneum. The potent inhibitory effects on the three identified targets attest 4 and 5 a pronounced multi-target anti-inflammatory profile which warrants further investigation on their pharmacokinetics and in vivo efficacy.  相似文献   
4.
5.
6.
7.
BackgroundStudies revealed that insulin resistance is associated with fibrosis progression and has negative impact on sustained virological response after standard antiviral therapy in patients with chronic hepatitis C (CHC).AimTo assess the role of IR on progression of liver fibrosis and early virological response (EVR) rates in patients with chronic hepatitis C infection.Patients and methodsThe study population comprised 79 subjects who underwent combination therapy for CHC. Laboratory investigations in the form of glucose, insulin, bilirubin, alanine aminotransferase (ALT), cholesterol and triglycerides and liver biopsy were done for all patients. Insulin resistance was calculated using the homeostasis model of IR (HOMA-IR).ResultsIR was increased (>2 IU) in 31 (40.7%) of patients. Early virological response was achieved among 37 patients (48.7%). No difference in EVR, viral load or grade of liver fibrosis between patients with and without IR. A significant positive correlation was found between IR and liver steatosis.ConclusionInsulin resistance is a common finding in CHC, it is associated with increase liver steatosis. However it has no impact on EVR to combined interferon ribavirin therapy, viral load or necroinflammation.  相似文献   
8.

Objective:

To examine the relative association of abdominal visceral adipose tissue (VAT) with cardiometabolic risk factors between African and European Americans.

Design and Methods:

We conducted a cross‐sectional study of 2035 African Americans from Jackson Heart Study (JHS) and 3170 European Americans from Framingham Heart Study (FHS) who underwent computed tomography assessment of VAT and subcutaneous adipose tissue (SAT). The FHS participants were weighted to match the age distribution of the JHS participants and the metabolic risk factors were examined by study groups in relation to VAT.

Results:

JHS participants had higher rates of obesity, hypertension, diabetes and metabolic syndrome than FHS participants (all p = 0.001). The associations were weaker in JHS women for VAT with blood pressure, triglycerides, HDL‐C, and total cholesterol (pinteraction = 0.03 to 0.001) than FHS women. In contrast, JHS men had stronger associations for VAT with high triglycerides, low HDL, and metabolic syndrome (all pinteraction = 0.001) compared to FHS men. Similar associations and gender patterns existed for SAT with most metabolic risk factors.

Conclusions:

The relative association between VAT and cardiometabolic risk factors is weaker in JHS women compared to FHS women, whereas stronger association with triglycerides and HDL were observed in JHS men.  相似文献   
9.
Epiphytes constitute over 70% of orchid diversity, but little is known about the functioning of their mycorrhizal associations. Terrestrial orchid seeds germinate symbiotically in soil and leaf litter, whereas epiphytic orchids may be exposed to relatively high light levels from an early stage of development and often produce green seeds. This suggests that seedlings of the two groups of orchids may differ in their responses to light and requirements for mycorrhiza-supplied carbon. The interactive effects of light, exogenous carbon and mycorrhizal status on germination and growth were investigated in vitro using axenic agar microcosms for one tropical epiphyte and three geophytic orchid species. The geophytic species strongly depended on their mycorrhiza for growth and this could not be substituted by exogenous sucrose, whereas the epiphytic species achieved 95% of the mycorrhizal seedling volume when supplied with exogenous sucrose in the dark. Mycorrhiza status strongly interacted with light exposure, enabling germination. Light inhibited or severely reduced growth, especially for the terrestrial orchids in the absence of mycorrhiza. For the first time, this study showed the parallel ecological importance of mycorrhizal fungi in overcoming light inhibition of seed germination and growth in both terrestrial and epiphytic orchids.  相似文献   
10.
We previously identified pituitary tumor-derived fibroblast growth factor receptor 4 (ptd-FGFR4), an alternatively transcribed N-terminally truncated cytoplasmic receptor isoform. Unlike wild-type FGFR4, ptd-FGFR4 facilitates cell transformation and results in pituitary tumor formation in transgenic mice. To investigate differences in the tumorigenic properties of FGFR4 and ptd-FGFR4, we examined their abilities to modulate cell adhesiveness. Introduction of ptd-FGFR4 into GH4 pituitary cells or NIH 3T3 fibroblasts resulted in significant reduction in cell adhesion to a collagen IV matrix compared with FGFR4- or empty vector-transfected cells. This adhesive difference was evident in the absence or presence of FGF stimulation. Furthermore, treatment with beta1-integrin neutralizing antibody markedly reduced adhesiveness in FGFR4-transfected cells but had little effect on the depressed adhesiveness of ptd-FGFR4-transfected cells. Unlike wild-type FGFR4, ptd-FGFR4 does not associate with neural cell-adhesion molecule (NCAM). Cells expressing FGFR4 demonstrate membranous N-cadherin with a noninvasive growth pattern identical to control GH4 cells when injected into immunodeficient mice. In contrast, ptd-FGFR4-expressing cells develop invasive tumors in vivo with marked loss of N-cadherin that localizes to the cytoplasm. Consistent with these changes, beta-catenin expression was diminished and its interaction with N-cadherin was disrupted in the presence of ptd-FGFR4, but both were intact in the presence of wild-type FGFR4. These data highlight the importance of membrane-anchored FGFR4 in assembling a multiprotein FGFR4 complex with NCAM and N-cadherin playing pivotal functions in maintaining normal cell adhesion. Disruption of distinct NCAM/N-cadherin proadhesive complexes by a tumor-derived FGFR4 isoform provides a novel mechanism beyond ligand independence that explains the pathobiology of proliferative and infiltrative but nonmetastatic neoplasms.  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