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   112篇
  免费   0篇
教育   58篇
科学研究   45篇
各国文化   1篇
文化理论   1篇
信息传播   7篇
  2023年   4篇
  2022年   3篇
  2021年   3篇
  2019年   2篇
  2018年   6篇
  2017年   9篇
  2016年   6篇
  2015年   4篇
  2014年   4篇
  2013年   15篇
  2012年   7篇
  2011年   3篇
  2010年   5篇
  2009年   4篇
  2008年   5篇
  2007年   4篇
  2006年   1篇
  2005年   3篇
  2004年   3篇
  2003年   2篇
  2002年   1篇
  2001年   5篇
  2000年   4篇
  1999年   1篇
  1997年   2篇
  1995年   1篇
  1992年   1篇
  1988年   1篇
  1987年   1篇
  1980年   1篇
  1979年   1篇
排序方式: 共有112条查询结果,搜索用时 0 毫秒
1.
Deficiency or excess of certain trace elements has been considered as risk factor for prostate cancer. This study was aimed to detect differential changes and mutual correlations of selected trace elements in prostate cancer tissue versus benign prostatic hyperplasia tissue. Zinc, copper, iron, calcium and selenium were analysed in histologically proven 15 prostate cancer tissues and 15 benign prostatic hyperplasia tissues using atomic absorption spectrophotometer. Unpaired two tailed t test/Mann–Whitney U test and Pearson correlation coefficient were used to compare the level of trace elements, elemental ratios and their interrelations. As compared to benign prostatic tissue, malignant prostatic tissue had significantly lower selenium (p = 0.038) and zinc (p = 0.043) concentrations, a lower zinc/iron ratio (p = 0.04) and positive correlation of selenium with zinc (r = 0.71, p = 0.02) and iron (r = 0.76, p = 0.009). Considerably divergent interrelationship of elements and elemental ratios in prostate cancer versus benign prostatic hyperplasia was noted. Understanding of differential elemental changes and their interdependence may be useful in defining the complex metabolic alterations in prostate carcinogenesis with potential for development of element based newer diagnostic, preventive and therapeutic strategies. Further studies may be needed to elucidate this complex relationship between trace elements and prostate carcinogenesis.  相似文献   
2.
Systems biology     
Systems biology seeks to study biological systems as a whole, contrary to the reductionist approach that has dominated biology. Such a view of biological systems emanating from strong foundations of molecular level understanding of the individual components in terms of their form, function and interactions is promising to transform the level at which we understand biology. Systems are defined and abstracted at different levels, which are simulated and analysed using different types of mathematical and computational techniques. Insights obtained from systems level studies readily lend to their use in several applications in biotechnology and drug discovery, making it even more important to study systems as a whole.  相似文献   
3.
An estimate of water levels due to the interaction of tide and surge associated with a storm including air bubble effects is made along the coastal region of Bangladesh. For this purpose, a vertically integrated shallow water model in Cartesian coordinate system is developed introducing air bubbles and is solved using nested finite difference schemes. A fine grid model covering the region between 21°15′N to 23°N and 89°E to 92° E has been nested into a coarse grid model covering the region between 15°N to 23°N and 85°E to 95°E in the Bay of Bengal to incorporate all the major islands and coastal bending accurately. By applying tidal forcing through the southern open boundary of the coarse grid model appropriate tidal conditions are generated in the problem domain. Numerical experiments are performed with the help of the model to simulate water levels due to tide and surge interaction including air bubble effects associated with the tropical storm of April 1991. The model results are found to be reasonable and the model can be found to simulate higher water levels in the presence of air bubbles.  相似文献   
4.
This study examined issues in supporting middle-school teachers to become more learner centered when implementing computer-based, workplace simulations in their classrooms. Specifically, this report focuses on a participant observation study of two teachers to develop and evolve a framework for professional development. The framework was developed based on prior professional development efforts, information on developing learner-centered classrooms, and data about teacher change. The framework included five key pieces: (a) reflection, (b) proximal goals, (c) collegial support groups, (d) one-on-one feedback, and (e) support materials for the teachers. The foundation for the framework was a belief that change is individual and needs to be supported in context and over time. The data included field observations as the teachers used the simulations in their classrooms made by the author and three outside observers, and interviews with each teacher following her use of the simulation program. During the four-month study, the original framework evolved in response to the data collected. The final version of the framework focuses on the professional developer working with teachers to develop reflective skills. Proximal goals became a focusing tool for reflection after teachers had begun to develop their reflective skills. The interplay between reflection and proximal goals was enhanced by outside resources, one-on-one feedback, and collegial group meetings. The work reported here was comp;eted as part of a dissertation conducted at Indiana University’s Center for Innovation in Assessment, and was supported in part by grants from the Andrew W. Mellon Foundation and the Russell Sage Fundation. The school and participant names have been changed to protect their identity. All researcher names are actual.  相似文献   
5.
The antioxidants are essential molecules in human system but are not miracle molecules. They are neither performance enhancers nor can prevent or cure diseases when taken in excess. Their supplemental value is debateable. In fact, many high quality clinical trials on antioxidant supplement have shown no effect or adverse outcomes ranging from morbidity to all cause mortality. Several Chochrane Meta-analysis and Markov Model techniques, which are presently best available statistical models to derive conclusive answers for comparing large number of trials, support these claims. Nevertheless none of these statistical techniques are flawless. Hence, more efforts are needed to develop perfect statistical model to analyze the pooled data and further double blind, placebo controlled interventional clinical trials, which are gold standard, should be implicitly conducted to get explicit answers. Superoxide dismutase (SOD), glutathione peroxidase and catalase are termed as primary antioxidants as these scavenge superoxide anion and hydrogen peroxide. All these three enzymes are inducible enzymes, thereby inherently meaning that body increases or decreases their activity as per requirement. Hence there is no need to attempt to manipulate their activity nor have such efforts been clinically useful. SOD administration has been tried in some conditions especially in cancer and myocardial infarction but has largely failed, probably because SOD is a large molecule and can not cross cell membrane. The dietary antioxidants, including nutrient antioxidants are chain breaking antioxidants and in tandem with enzyme antioxidants temper the reactive oxygen species (ROS) and reactive nitrogen species (RNS) within physiological limits. Since body is able to regulate its own requirements of enzyme antioxidants, the diet must provide adequate quantity of non-enzymic antioxidants to meet the normal requirements and provide protection in exigent condition. So far, there is no evidence that human tissues ever experience the torrent of reactive species and that in chronic conditions with mildly enhanced generation of reactive species, the body can meet them squarely if antioxidants defense system in tissues is biochemically optimized. We are not yet certain about optimal levels of antioxidants in tissues. Two ways have been used to assess them: first by dietary intake and second by measuring plasma levels. Lately determination of plasma/serum level of antioxidants is considered better index for diagnostic and prognostic purposes. The recommended levels for vitamin A, E and C and beta carotene are 2.2–2.8 μmol/l; 27.5–30 μmol/l; 40–50 μmol/l and 0.4–0.5 μmol/l, respectively. The requirement and recommended blood levels of other dietary antioxidants are not established. The resolved issues are (1) essential to scavenge excess of radical species (2) participants in redox homeostasis (3) selective antioxidants activity against radical species (4) there is no universal antioxidant and 5) therapeutic value in case of deficiency. The overarching issues are (1) therapeutic value as adjuvant therapy in management of diseases (2) supplemental value in developing population (3) selective interactivity of antioxidant in different tissues and on different substrates (4) quantitative contribution in redox balance (5) mechanisms of adverse action on excess supplementation (6) advantages and disadvantages of prooxidant behavior of antioxidants (7) behavior in cohorts with polymorphic differences (8) interaction and intervention in radiotherapy, diabetes and diabetic complications and cardiovascular diseases (9) preventive behavior in neurological disorders (10) benefits of non-nutrient dietary antioxidants (11) markers to assess optimized antioxidants status (12) assessment of benefits of supplementation in alcoholics and heavy smokers. The unresolved and intriguing issues are (1) many compounds such as vitamin A and many others possessing both antioxidant and non-antioxidant properties contribute to both the activities in vivo or exclusively only to non-antioxidant activity and (2) since human tissues do not experience the surge of FR, whether there is any need to develop stronger synthetic antioxidants. Theoretically such antioxidants may do more harm than good.  相似文献   
6.
7.
Abnormal lipid profile is often found in women with Polycystic Ovary Syndrome. To assess the impact of abnormal lipid profile on atherosclerosis in young Polycystic Ovary Syndrome women, carotid intima-media thickness as judged by B-mode ultrasonography were done in 30 young (18–35 yrs) Polycystic Ovary Syndrome women and in similarly age-matched 30 apparently healthy controls. Compared to controls, young Polycystic Ovary Syndrome women had significantly elevated serum total cholesterol, triglyceride and LDL-C levels and carotid intima-media thickness. HDL-C level did not differ significantly between two groups of women. In Polycystic Ovary Syndrome women carotid intima-media thickness was positively correlated with serum total cholesterol, triglyceride and LDL-C and negatively correlated with serum HDL-C. Our study suggests that even young Polycystic Ovary Syndrome women are prone to atherosclerosis from early age.  相似文献   
8.
Variability in analytical performance of some analyte indicated the need of evaluation of quality plan of our laboratory. We tried to put the same degree of effort into our quality metrics as we put into the laboratory processes themselves. Application of six sigma methodologies improve the quality by focusing on the root causes of the problems in performance and analyzing by flowcharts, fishbone diagrams and other quality tools. Sigma metric was calculated for laboratory parameters for a period of 8 months during 2018–19. The analytes with poor sigma metric were free Thyroxine (FT3, FT4), Sodium, Calcium and Magnesium. Sigma metric of free Thyroxine (FT3, FT4), Sodium, Calcium and Magnesium were below 3. A road map for process improvement was designed with DMAIC (Define-Measure-Analyze-Improve-Control) model to solve the issue. Possible causes for low analytical performance of the particular analytes were depicted in Fishbone diagram. The Fishbone analysis identified the water quality issues with electrolyte analysis while high ambient temperature was culprit for poor assay performance of free Thyroxine. Sigma metric of the analytical performance was assessed once again after root cause analysis. Sigmametric showed marked improvement in control phase. Identification of problems led to reduction in non value added work leading to adequate resource utilization by addressing the priority issue. Therefore, DMAIC tool with Fish bone model analysis can be recommended as a well suited method for troubleshooting in poor performance of laboratory parameter.  相似文献   
9.
10.
The key to agricultural development in the eastern region of India, where problems of excess water and water scarcity coexist, is the scientific management of water resources with the adoption of recommended water-management technologies. A vast networking of infrastructure for the development and dissemination of water- management technologies have been designed since the very inception of planned economic change. Despite these concerted efforts, a large number of recommended technologies are either being adopted in piece-meal or not at all. The research and extension systems have been generating and disseminating technologies, therefore, it was felt worthwhile to assess the feasibility and appropriateness of recommended tecnologies as perceived in the first instance by the personnel of the research system and followed by the extension personnel. These steps were felt to be a precursor to screen the recommended technologies for their dissemination and evaluation in different farming systems. The assessment of recommended water-management technologies was performed after their documentation from different organisations working in the field of water management in two eastern India states viz. Orissa and West Bengal. The perception of 30 personnel members of the research system regarding the feasibility of these technologies elucidated that out of 86 documented recommended water-management technologies, 40 were having feasibility scores of ≥ 4.0; 8 technologies with score £ 3.0 and the rest of the 38 technologies with a score between 3.0 and 4.0 on a feasibility continuum range from 1.0 (not feasible) to 5.0 (highly feasible). Out of 40 recommended technologies (already assessed as highly feasible by the research personnel), extension personnel have perceived 16 and 10 technologies as highly appropriate and feasible, respectively. While six and four technologies were found to be less appropriate and feasible, respectively. Correlation of all nine indicators of appropriateness with feasibility of technologies was significant. Five indicators of appropriateness viz. simplicity, physical compatibility, production sustainability, cultural compatibility and cost together constituted 36.8 per cent of the total variation in feasibility with the ‘t’ values and ‘F’ values being significant. It indicates that not appropriateness of technologies alone but other factors influence the feasibility of technologies.  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