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   95篇
  免费   11篇
  106篇
  2021年   2篇
  2020年   2篇
  2019年   1篇
  2018年   3篇
  2017年   2篇
  2016年   10篇
  2015年   4篇
  2014年   6篇
  2013年   5篇
  2012年   4篇
  2011年   8篇
  2010年   4篇
  2009年   4篇
  2008年   8篇
  2007年   2篇
  2006年   1篇
  2005年   3篇
  2004年   1篇
  2003年   3篇
  2002年   1篇
  2001年   4篇
  2000年   5篇
  1999年   1篇
  1998年   2篇
  1996年   1篇
  1995年   1篇
  1993年   1篇
  1992年   1篇
  1991年   3篇
  1990年   2篇
  1988年   1篇
  1983年   1篇
  1980年   1篇
  1979年   1篇
  1977年   1篇
  1975年   1篇
  1972年   1篇
  1970年   1篇
  1969年   2篇
  1963年   1篇
排序方式: 共有106条查询结果,搜索用时 15 毫秒
1.

Background

Although recent studies report on the benefits of blended learning in improving medical student education, there is still no empirical evidence on the relative effectiveness of blended over traditional learning approaches in medical statistics. We implemented blended along with on-site (i.e. face-to-face) learning to further assess the potential value of web-based learning in medical statistics.

Methods

This was a prospective study conducted with third year medical undergraduate students attending the Faculty of Medicine, University of Belgrade, who passed (440 of 545) the final exam of the obligatory introductory statistics course during 2013–14. Student statistics achievements were stratified based on the two methods of education delivery: blended learning and on-site learning. Blended learning included a combination of face-to-face and distance learning methodologies integrated into a single course.

Results

Mean exam scores for the blended learning student group were higher than for the on-site student group for both final statistics score (89.36±6.60 vs. 86.06±8.48; p = 0.001) and knowledge test score (7.88±1.30 vs. 7.51±1.36; p = 0.023) with a medium effect size. There were no differences in sex or study duration between the groups. Current grade point average (GPA) was higher in the blended group. In a multivariable regression model, current GPA and knowledge test scores were associated with the final statistics score after adjusting for study duration and learning modality (p<0.001).

Conclusion

This study provides empirical evidence to support educator decisions to implement different learning environments for teaching medical statistics to undergraduate medical students. Blended and on-site training formats led to similar knowledge acquisition; however, students with higher GPA preferred the technology assisted learning format. Implementation of blended learning approaches can be considered an attractive, cost-effective, and efficient alternative to traditional classroom training in medical statistics.  相似文献   
2.
Horseradish peroxidase is a well-known member of the peroxidase family that catalyzes oxidation of flavonoids and phenolic substrates to free phenoxyl or semiquinone radicals. Aim of this study was to investigate in vitro oxidation of quercetin by horseradish peroxidase in the presence of l-cysteine as nucleophilic agent, and its influence on previously formed semiquinone- and quinone-type metabolites. The obtained results showed that in the reaction without l-cysteine several products were present, such as quercetin quinone methide, phloroglucinol carboxylic acid, protocatechuic acid, as well as quercetin heterodimer and derivates of quercetin heterodimer. On the other hand, in the presence of l-cysteine only three products were obtained, quercetin quinone methide and two new isomeric mono-cysteine derivatives of quercetin with mass exp. m/z 420.04?±?0.1 [quercetin?+?cysteine–H] (theor. m/z 420.0389 [quercetin?+?cysteine–H]).  相似文献   
3.
Kv1.3 is a voltage gated potassium channel that has been implicated in pathophysiology of multiple sclerosis (MS). In the present study we investigated temporal and cellular expression pattern of this channel in the lumbar part of spinal cords of animals with experimental autoimmune encephalomyelitis (EAE), animal model of MS. EAE was actively induced in female Dark Agouti rats. Expression of Kv1.3 was analyzed at different time points of disease progression, at the onset, peak and end of EAE. We here show that Kv1.3 increased by several folds at the peak of EAE at both gene and protein level. Double immunofluorescence analyses demonstrated localization of Kv1.3 on activated microglia, macrophages, and reactive astrocytes around inflammatory lesions. In vitro experiments showed that pharmacological block of Kv1.3 in activated astrocytes suppresses the expression of proinflammatory mediators, suggesting a role of this channel in inflammation. Our results support the hypothesis that Kv1.3 may be a therapeutic target of interest for MS and add astrocytes to the list of cells whose activation would be suppressed by inhibiting Kv1.3 in inflammatory conditions.  相似文献   
4.
The predictive value of B-type natriuretic peptide (BNP) with respect to the occurrence of new-onset atrial fibrillation (AF) in patients with ST-segment elevation myocardial infarction (STEMI) treated by primary percutaneous coronary intervention (PCI) is unknown. The aim of this study was to evaluate whether BNP has a predictive value for the occurrence of new-onset AF in patients with STEMI treated by primary PCI. In 180 patients with STEMI treated by primary PCI, BNP concentrations were measured 24h after chest pain onset. The Receiver Operating Characteristic analysis was performed to identify the most useful BNP cut-off level for the prediction of AF. The patients were divided into the two groups according to calculated cut-off level: high BNP group (BNP≥720 pg/mL, n=33) and low BNP group (BNP<720 pg/mL, n=147). The incidence of AF was 5.0%, and occurred more frequently in high BNP group (7/33, 21.2%) than in low BNP group (2/147, 1.4%), (p<0.001). Patients with high BNP were older (p=0.017), had more often anterior wall infarction (p=0.015), higher Killip class on admission (p=0.038), higher peak troponin I (p=0.002), lower left ventricular ejection fraction (p=0.029) than patients with low BNP. After multivariate adjustment, BNP was an independent predictor of AF (OR 3.70, 95% CI 1.40-9.77, p=0.008). BNP independently predicts the occurrence of new-onset AF in STEMI patients treated by primary PCI.  相似文献   
5.
Whole-body cryotherapy (WBC) involves exposing minimally dressed participants to very cold air (injecting liquid nitrogen with temperature −195 °C), either in a specially designed chamber (cryo-chamber) or cabin (cryo-cabin), for a short period of time. The aim of this study was to examine the actual temperature of the air in the cryo-cabin at different locations throughout the cabin by using human subjects and a manikin. Additionally, we monitored skin temperature before and for 60 min after the cryo-cabin session. Twelve subjects completed one 3 min cryo-cabin session. Temperature next to the skin was assessed during the session, while the skin temperature was monitored before, 3 min after and every 10 min for 60 min after completing the session. There was a statistically significant interaction (time×position) for temperature among the different body parts during the WBC, and for skin temperature among different body parts after the cryo-cabin session. Statistically significant time effects during and following cryo-cabin session were present for all body parts. We showed that actual temperature in the cryo-cabin is substantially different from the one reported by the manufacturer. Thermal response after cryo-cabin session is similar to response observed after cryo-chamber cold exposure reported in previously published studies. This could be of great practical value as cryo-cabins are less expensive and easier to use compared to cryo-chambers.  相似文献   
6.
Journal of Plant Growth Regulation - Over the last years, cytokinin deficiency has been studied in a variety of plant species, using transgenic expression of cytokinin oxidase/dehydrogenase genes...  相似文献   
7.
Because adenosine plays a role in the regulation of glomerular filtration rate and of the release of renin, we examined the possibility of a local source for this mediator. We found that rat cultured glomerular mesangial cells converted 5'-AMP into adenosine. The properties of the enzyme involved in the reaction were those of an ecto-5' nucleotidase: (1) the products of the reaction were generated in the extracellular fluid although no 5'-nucleotidase was released by the cells into the medium; (2) identical activities were found for cultured cells in situ and sonicated cells; (3) the diazonium salt of sulfanilic acid which is a nonpenetrating reagent inhibited up to 75% of the enzyme activity. Ecto-5'-nucleotidase activity of intact cells obeyed Michaelis-Menten kinetics. Apparent Km for 5'-AMP was 0.32 mM. 5'-UMP was a strictly competitive inhibitor. ADP exerted a very powerful inhibitory effect and behaved also as a competitive inhibitor. ATP was inhibitory both by increasing Km and by decreasing Vmax. Ecto-5'-nucleotidase was active in the absence of divalent cations. However, Mg2+, Ca2+, Co2+ and Mn2+ were stimulatory. Zn2+ and Cu2+ suppressed the activity. Concanavalin A, a plant lectin, was markedly inhibitory, suggesting that a glycoprotein moiety was necessary to express enzyme activity. Ecto-5'-nucleotidase activity was not modified during phagocytosis of serum-treated zymosan by mesangial cells. Rat cultured glomerular epithelial cells exhibited a 5'-nucleotidase activity which was 4 times lower than that of the mesangial cells in primary culture.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
8.
Biochemical properties of enzyme alpha-amylase were surveyed in Drosophila obscura Old world group of species (D. subobscura, D. ambigua, D. obscura and D. tristis) sampled in the same habitat, with the aim to reveal some ecological and evolutionary aspects of amylase polymorphism, which has been studied extensively in D. subobscura, but not compared with other species in the group. The data obtained show that D. subobscura is distinct from the other three species regarding all biochemical amylase properties. Such a divergence also correlates with the niche breadth and relative abundance of these species in the same habitat.  相似文献   
9.
Advanced oxidation protein products (AOPP) and total thiol (SH) groups levels in plasma and CSF were studied in a cohort of 50 clinically isolated syndrome (CIS) and 57 relapsing remittent multiple sclerosis (RRMS) patients related to 20 control group (CG) patients’ values. The obtained results were compared regarding patients demographic, biochemical, clinical (EDSS) and MRI features (total T2 weighted lesions number and Gd enhancement lesion volume).  相似文献   
10.
The screening of microbial natural products continues to represent an important route to the discovery of novel chemicals for development of new therapeutic agents. The aim of this work was to develop an efficient method for the detection of immunosuppressive compounds produced by soil actinomycetes. Mutant strain of Saccharomyces cerevisiae, named FAV20, sensitive to FK506 was constructed by disrupting VMA22 gene using the selectable marker kanMX4 which allowed detection of integration events. Actinomycetes were isolated from different soil samples and in a newly developed test with S. cerevisiae FAV20, six strains have been identified that produce bioactive compounds with the same mechanism of action as FK506. S. cerevisiae FAV20 can be easily used as a test strain in drug screening programs based on inhibition of the calcineurin phosphatase dependent signaling pathway in the cell.  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