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   348篇
  免费   7篇
教育   170篇
科学研究   161篇
各国文化   5篇
体育   5篇
信息传播   14篇
  2023年   2篇
  2022年   7篇
  2021年   15篇
  2020年   6篇
  2019年   10篇
  2018年   18篇
  2017年   15篇
  2016年   15篇
  2015年   17篇
  2014年   15篇
  2013年   51篇
  2012年   19篇
  2011年   15篇
  2010年   11篇
  2009年   18篇
  2008年   15篇
  2007年   13篇
  2006年   17篇
  2005年   7篇
  2004年   8篇
  2003年   2篇
  2002年   3篇
  2001年   6篇
  2000年   7篇
  1999年   5篇
  1998年   2篇
  1997年   6篇
  1995年   3篇
  1994年   7篇
  1993年   2篇
  1992年   4篇
  1991年   3篇
  1989年   4篇
  1988年   1篇
  1986年   1篇
  1985年   2篇
  1984年   1篇
  1980年   1篇
  1973年   1篇
排序方式: 共有355条查询结果,搜索用时 218 毫秒
11.
Present investigation shows that hydroethanolic extract of Moringa oleifera (MOHE) and its isolated saponin (SM) attenuates DMBA induced renal carcinogenesis in mice. Isolation of SM was achieved by TLC and HPLC and characterization was done using IR and 1H NMR. Animals were pre-treated with MOHE (200 and 400 mg/kg body weight; p.o), BHA as a standard (0.5 and 1 %) and SM (50 mg/kg body weight) for 21 days prior to the administration of single dose of DMBA (15 mg/kg body weight). Administration of DMBA significantly (p < 0.001) enhanced level of xenobiotic enzymes. It enhanced renal malondialdehyde, with reduction in renal glutathione content, antioxidant enzymes and glutathione-S-transferase. The status of renal aspartate transaminase, alanine transaminase, alkaline phosphatase and total protein content were also found to be decreased along with increase in total cholesterol in DMBA administered mice. Pretreatment with MOHE and SM significantly reversed the DMBA induced alterations in the tissue and effectively suppressed renal oxidative stress and toxicity.  相似文献   
12.
13.
14.
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   
15.
This study deals with the effects of freeze dried rhizome powder of Curcuma longa (C. longa) dissolved in milk on normal as well as diabetic models. Diabetes of type II and type I was within 3 days of a single administration of doses of 45 and 65 mg kg−1 of streptozotocin respectively. Various parameters such as blood glucose levels, triglycerides, total cholesterol, high density lipoprotein, very low density lipoprotein, low density lipoprotein, serum glutamic oxaloacetic transaminase, serum glutamic pyruvate transaminase, alkaline phosphatase, creatinine, hemoglobin, urine protein and urine sugar in addition to body weight were taken in to consideration and were analyzed after administration of variable doses of rhizome powder. The dose of 200 mg kg−1 was identified as the most effective dose as it increased HDL, Hb and bw (P<0.05) with significant decrease in the levels of blood glucose, lipid profile and hepatoprotective enzymes (P<0.001).  相似文献   
16.
The study explores the institutional factors which influence the impact of education in building academic entrepreneurship in higher educational institutes of Uttarakhand state, India. In order to understand the institutional barriers, the author interviewed 68 senior-level educationists, who were working in the capacity of Director General, Professor, Head, or Director in three different universities or their affiliated institutions. Based on the qualitative data obtained from interviews, we identified five major and four minor factors which were influencing the impact of education in building academic entrepreneurship in the state. The major barriers identified were – poor entrepreneurial ecosystem, poor entrepreneurial orientation, and inclination of universities and institutes to prepare students for jobs, inadequate content of the subject, need for training of entrepreneurship faculty, or specialized entrepreneurship faculty and ineffective teaching methodology. The results so obtained were further reviewed and validated on the basis of past research. The study also takes into account the institutional problems in developing academic entrepreneurship in other developing countries and compares the results. The study will help policy-makers, teachers, and educational institutions to recognize the possible shortfalls in the education system, which eventually result in poor academic entrepreneurship. Suggestions for improvements are included.  相似文献   
17.
18.
An external quality assessment was conducted to assess the performance of various laboratories for RIA of thhyroid related hormones in two phases. In the first phase thirty five laboratories participated. At the end of first phase a meeting cum workshop was organised to discuss the results of first phase, difficultires faced by the participants and pinpoint the short oming. A second phase was then initiated with an objective of improvement in the performance, if any, where twelve samples from four pools were distributed to twenty four laboratories who participated for the second phase. The overall return of the results increased significantly from 71.8% (1586/2208) for the first phase to 92.4% (732/792) for the second phase. The inter laboratory %CV for T3, T4 and TSH were lower during the second phase (30.6%, 19.0% and 31.6% respectively) as compared to those observed during first phase (36.3%, 22.7% and 52.8% respectively). Similarly, there was an improvement in reproducibility of ALTM as %CV for T3, T4 and TSH decreased from 6.0%, 9.8% and 13.4% respectively to 4.5%, 4.6% and 8.5% respectively. The individual performances of the participating laboratories viz. bias, variability of bias and imprecision also showed a trend towards improvement as percent laboratories having desirable or acceptable results for T3, T4 and TSH increased from 10.7%, 60.7% and 0.0% respectively to 20.8%, 66.7% and 22.2% respectively. External quality assessment thus appears to be beneficial in assessing the performane of a laboratory in comfparison with other laboratories and indeed helps in improving the performance.  相似文献   
19.
Endogenous oestrogens are thought to be involved in breast cancer, but few studies could show the direct relationship between hormones and pathological process of the disease. In the present study, oestradiol was estimated in the serum of pre-and postmenopausal breast cancer patients along with normal healthy controls and patients with carcinoma of the uterine cervix which is not dependent on oestrogens. Premenopausal patients with breast cancer showed higher levels of oestradiol as compared to premenopausal control women as well as cervical cancer patients. Whereas, no statistically significant differences were observed in serum oestradiol levels amongst postmenopausal groups of breast cancer, cervical cancer and normal women. The result of the study reflects the association of oestradiol as well as its difference in the pathological events of pre and postmenopausal breast cancer.  相似文献   
20.
Many plants have been used for the treatment of diabetes mellitus in Indian system of medicine and in other ancient systems of the world. Out of these only a few have been evaluated as per modern system of medicine. From many such plants only extracts have been prepared and their usefulness evaluated in experimental diabetes in animals. In some plants likeAllium cepa, Allium sativum, Ficus bengalensis, Gymnema sylvestre, Pterocarpus marsupium etc. active hypoglycemic principles have been isolated and their mechanism of action studied. Most of them seem to act directly on pancreas (pancreatic effect) and stimulate insulin level in blood. Some have extra pancreatic effect also by acting directly on tissues like liver, muscle etc. and alter favourably the activities of the regulatory enzymes of glycolysis, gluconeogenesis and other pathways. Since the plant products have less side effects, they have the potential as good hypoglycemic drugs. They may also provide clues for the development of new and better oral drugs for diabetes.  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