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   200篇
  免费   4篇
  204篇
  2021年   4篇
  2019年   2篇
  2017年   2篇
  2016年   1篇
  2015年   2篇
  2014年   9篇
  2013年   6篇
  2012年   8篇
  2011年   10篇
  2010年   7篇
  2009年   11篇
  2008年   11篇
  2007年   5篇
  2006年   6篇
  2005年   5篇
  2004年   5篇
  2003年   3篇
  2002年   5篇
  2001年   10篇
  2000年   3篇
  1999年   4篇
  1998年   4篇
  1997年   3篇
  1996年   2篇
  1995年   1篇
  1992年   4篇
  1991年   7篇
  1990年   5篇
  1989年   6篇
  1988年   4篇
  1987年   5篇
  1986年   9篇
  1985年   4篇
  1984年   1篇
  1982年   2篇
  1980年   1篇
  1979年   3篇
  1978年   1篇
  1977年   2篇
  1976年   3篇
  1975年   1篇
  1974年   1篇
  1972年   1篇
  1971年   3篇
  1970年   4篇
  1969年   2篇
  1967年   1篇
  1966年   2篇
  1965年   1篇
  1962年   1篇
排序方式: 共有204条查询结果,搜索用时 15 毫秒
21.
22.

Background  

Parkinson's disease (PD) is the second most common neurodegenerative disorder. As there is no definitive diagnostic test, its diagnosis is based on clinical criteria. Recently transcranial duplex scanning (TCD) of the substantia nigra in the brainstem has been proposed as an instrument to diagnose PD. We and others have found that TCD scanning of substantia nigra duplex is a relatively accurate diagnostic instrument in patients with parkinsonian symptoms. However, all studies on TCD so far have involved well-defined, later-stage PD patients, which will obviously lead to an overestimate of the diagnostic accuracy of TCD.  相似文献   
23.
The rate of tumour growth is dependent on the balance between proliferation and apoptosis at all stages of carcinogenesis. Apoptosis inhibition, in turn, depends partly on the balance between expression of two cell death regulatory genes, Bcl-2 and Bax. Colon cancer has long been associated with disturbances in apoptosis regulation. The aim of our study was to determine the expression levels of Bcl-2 and Bax mRNAs in 1 microg sample of total RNA obtained from normal colon and colon adenocarcinoma. This study was intended to evaluate possible differences in Bcl-2 and Bax mRNA levels at particular stages of colon adenocarcinoma classified according to Duke's system. The apoptotic frequency (represented by Bax mRNA copy number) was inversely proportional to the decrease of Bcl-2 gene expression. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) was performed to confirm apoptosis.  相似文献   
24.
New methodologies for surveillance and identification of Mycobacterium tuberculosis are required to stem the spread of disease worldwide. In addition, the ability to discriminate mycobacteria at the strain level may be important to contact or source case investigations. To this end, we are developing MALDI-TOF MS methods for the identification of M. tuberculosis in culture. In this report, we describe the application of MALDI-TOF MS, as well as statistical analysis including linear discriminant and random forest analysis, to 16 medically relevant strains from four species of mycobacteria, M. tuberculosis, M. avium, M. intracellulare, and M. kansasii. Although species discrimination can be accomplished on the basis of unique m/z values observed in the MS fingerprint spectrum, discrimination at the strain level is predicted on the relative abundance of shared m/z values among strains within a species. For the 16 mycobacterial strains investigated in the present study, it is possible to unambiguously identify strains within a species on the basis of MALDI-TOF MS data. The error rate for classification of individual strains using linear discriminant analysis was 0.053 using 37 m/z variables, whereas the error rate for classification of individual strains using random forest analysis was 0.023 using only 18 m/z variables. In addition, using random forest analysis of MALDI-TOF MS data, it was possible to correctly classify bacterial strains as either M. tuberculosis or non-tuberculous with 100% accuracy.  相似文献   
25.
The expression of the genes coding TNFalpha and TNF RII receptors (TNF RII: TNFR2 membrane and soluble domain, TNFR2/R7 soluble domain) was analysed in colon cancer at the II and III stage of disease, by estimation of mRNA expression. The study included 80 patients with histopathologically confirmed adenocarcinoma. The number of TNFalpha mRNA, TNFR2 mRNA and TNFR2/R7 mRNA copies were estimated in tumour and healthy tissue. The highest number of mRNA TNF-alpha copies were investigated in all samples of tissue and independently of the stage of disease. Simultaneously, we noticed the largest number of mRNA copies for TNFalpha and TNF R2/R7 in healthy cells at stage III of the disease. It is possible to draw a hypothetical line separating the anti-cancer activity of TNFalpha and its influence on cancer progression.  相似文献   
26.
27.
The paper contains the results of natural film experiments carried out on inland and coastal waters in the Dead Vistula catchment area and mouth during 2000–2002, using the integrated Langmuir trough–Wilhelmy plate system. The static film parameters result from the generalized scaling procedures applied to the surface pressure–area isotherms. They appear to reflect in a quantitative and sensitive way the film composition (Alim, Mw, Eisoth), film solubility and the miscibility of its components (via R, ΔSc and y factors), and surface concentration (πeq, Γeq). The adsorption kinetics parameters: effective diffusion coefficient Deff/D and activation energy barrier Ea/RT are derived from dynamic surface pressure. There is a reason to suggest that certain classes of film-forming components or ‘end-members’ may dominate the static and dynamic surface properties. Variation in the surface rheological parameters of source-specific biosurfactants is postulated to reflect organic matter dynamics in natural waters and were measured for the Dead Vistula river, its tributaries and the adjacent coastal area.  相似文献   
28.
ABSTRACT: BACKGROUND: Diabetes (DM) deteriorates the prognosis in patients with coronary heart disease. However, the prognostic value of different glucose abnormalities (GA) other than DM in subjects with acute myocardial infarction (AMI) treated invasively remains unclear. AIMS: To assess the incidence and impact of GA on clinical outcomes in AMI patients treated with percutaneous coronary intervention (PCI). METHODS: A single-center, prospective registry encompassed 2733 consecutive AMI subjects treated with PCI. In all in-hospital survivors (n = 2527, 92.5 %) without the history of DM diagnosed before or during index hospitalization standard oral glucose tolerance test (OGTT) was performed during stable condition before hospital discharge and interpreted according to WHO criteria. The mean follow-up period was 37.5 months. RESULTS: The incidence of GA was as follows: impaired fasting glycaemia - IFG (n = 376, 15 %); impaired glucose tolerance - IGT (n = 560, 22 %); DM (n = 425, 17 %); new onset DM (n = 384, 15 %); and normal glucose tolerance NGT (n = 782, 31 %). During the long-term follow-up, death rate events for previously known DM, new onset DM and IGT were significantly more frequent than those for IFG and NGT (12.3; 9.6 and 9.4 vs. 5.6 and 6.4 %, respectively, P < 0.05). The strongest and common independent predictors of death in GA patients were glomerular filtration rate < 60 ml/min/1,73 m^2 (HR 2.0 and 2.8) and left ventricle ejection fraction < 35 % (HR 2.5 and 1.8, all P < 0.05) respectively. CONCLUSIONS: Glucose abnormalities are very common in AMI patients. DM, new onset DM and IGT increase remote mortality. Impaired glucose tolerance bears similar long-term prognosis as diabetes.  相似文献   
29.
Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces apoptosis and preferentially kills tumor cells by engaging specific glycosylated death receptors, resulting in the internalization of ligand/receptor complexes and recruitment of the initiator caspase-8 to an activation platform known as the death-inducing signaling complex (DISC). However, emergence of TRAIL-resistant sub-populations may contribute to therapeutic failure. To investigate resistance mechanisms, we isolated a stable TRAIL-resistant sub-population of the metastatic colon cancer cell line LS-LIM6, designated LIM6-TR. LIM6-TR cells are impaired in endocytosis of TRAIL/death receptors complexes and failed to recruit/activate caspase-8 to the DISC upon TRAIL stimulation. Differential activation of Wnt and JNK pathways is not responsible for acquisition of TRAIL resistance. LIM6-TR cells display a marked increase in cell-surface expression of galectin-3, an endogenous lectin, which co-localizes with and binds death receptors. Silencing of galectin-3 restores TRAIL sensitivity and promotes TRAIL-mediated endocytosis of TRAIL/death receptors complexes. Inhibitors of galectin-3 and glycosylation also re-sensitize LIM6-TR to TRAIL and restore internalization of ligand/receptors complexes. These studies identify a novel TRAIL-resistance mechanism in which galectin-3 impedes trafficking of death receptor by anchoring them in glycan nano-clusters, blocking the execution of the apoptosis signal.  相似文献   
30.
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