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   537篇
  免费   2篇
  国内免费   1篇
教育   245篇
科学研究   256篇
各国文化   3篇
体育   2篇
文化理论   3篇
信息传播   31篇
  2023年   2篇
  2022年   6篇
  2021年   20篇
  2020年   5篇
  2019年   10篇
  2018年   36篇
  2017年   25篇
  2016年   24篇
  2015年   29篇
  2014年   28篇
  2013年   53篇
  2012年   16篇
  2011年   19篇
  2010年   24篇
  2009年   28篇
  2008年   23篇
  2007年   17篇
  2006年   29篇
  2005年   21篇
  2004年   14篇
  2003年   24篇
  2002年   10篇
  2001年   8篇
  2000年   7篇
  1999年   6篇
  1998年   11篇
  1997年   6篇
  1996年   3篇
  1995年   6篇
  1994年   4篇
  1993年   5篇
  1992年   5篇
  1991年   1篇
  1990年   1篇
  1989年   2篇
  1986年   2篇
  1985年   1篇
  1983年   2篇
  1979年   1篇
  1977年   1篇
  1976年   2篇
  1975年   1篇
  1973年   1篇
  1962年   1篇
排序方式: 共有540条查询结果,搜索用时 546 毫秒
31.
Ensuring quality of laboratory services is the need of the hour in the field of health care. Keeping in mind the revolution ushered by six sigma concept in corporate world, health care sector may reap the benefits of the same. Six sigma provides a general methodology to describe performance on sigma scale. We aimed to gauge our laboratory performance by sigma metrics. Internal quality control (QC) data was analyzed retrospectively over a period of 6 months from July 2009 to December 2009. Laboratory mean, standard deviation and coefficient of variation were calculated for all the parameters. Sigma was calculated for both the levels of internal QC. Satisfactory sigma values (>6) were elicited for creatinine, triglycerides, SGOT, CPK-Total and Amylase. Blood urea performed poorly on the sigma scale with sigma <3. The findings of our exercise emphasize the need for detailed evaluation and adoption of ameliorative measures in order to effectuate six sigma standards for all the analytical processes.  相似文献   
32.
Methionine synthase reductase (MTRR) is an important enzyme of the folate/homocysteine pathway. It is responsible for regulation of methionine enzyme by reductive methylation. A common variant A66G is reported in the FMN-binding domain of the MTRR gene, which leads to substitution of isoleucine by methionine (I22M) in MTRR enzyme with reduced activity. Reduced catalytic activity of enzyme leads to high homocysteine concentration in blood and increases risk for numerous diseases. The frequency of A66G polymorphism varies in different ethnic groups. The present study has been designed to evaluate the frequency of MTRR A66G gene polymorphism in the Eastern UP population by PCR–RFLP method. Along with this we also performed a meta-analysis to evaluate the global prevalence of this polymorphism. Databases were screened to identified the eligible studies. The prevalence of the G allele and GG genotype was determined by the use of prevalence proportion with 95% CI. Open meta-analyst software was used for the meta-analysis. Total 1000 blood samples were analyzed, the frequencies of A and G alleles were 0.35 and 0.65 respectively. Meta-analysis results revealed that the prevalence of G allele and GG genotype were 49.4% (95% CI 40.6–58.1, p ≤ 0.001) and 24.3% (95% CI 17.8–30.9, p ≤ 0.001) respectively. In sub-group meta-analysis, the lowest frequency of G allele was found in South America (32.7%; 95% CI 14.1–51.3, p ≤ 0.001), and highest in Asia (56.4%; 95% CI 39.5–73.3, p ≤ 0.001). The results of the meta-analysis showed that the Asian population has the highest frequency of G allele and highest frequency of the GG genotype was found in the European population.  相似文献   
33.
In this study, a simple roller burnishing tool was made to operate burnishing processes on A356/5%SIC metal matrix composite fabricated by electromagnetic stir casting under different parameters. The effects of burnishing speed, burnishing force and number of burnishing passes on the surface roughness and tribological properties were measured. Scanning electron microscopy (SEM) graphs of the machined surface with PCD (insert-10) tool and roller burnished surface with tungsten carbide (WC) roller were taken into consider- ation to observe the surface finish of metal matrix composites. The mechanical properties (tensile strength, hardness, duc- tility) of A356/5%SIC metal matrix composites were studied for both unburnished samples and burnished samples. The results revealed that the roller burnished samples of A356/ 5%SIC led to the improvement in tensile strength, hardness and ductility. In order to find out the effects of roller bur- nishing process parameters on the surface roughness of A356/ 5%SIC metal matrix composite, response surface methodol- ogy (RSM) (Box-Behnken design) was used and a prediction model was developed relevant to average surface roughness using experimental data. In the range of process parameters, the result shows that roller burnishing speed increases, and surface roughness decreases, but on the other hand roller burnishing force and number of passes increase, and surface roughness increases. Optimum values of burnishing speed (1.5 m/s), burnishing force (50 N) and number of passes (2) during roller burnishing of A356/5%SIC metal matrix com- posite to minimize the surface roughness (predicted 1.232 μm) have been found out. There was only 5.03% error in the experimental and modeled results of surface roughness.  相似文献   
34.
This pilot study set out to examine the impact of a regular practice of yoga within schooling curricular hours on the well-being and behaviors of atypically developing children. The design of this study was based on a qualitative hermeneutic-phenomenology approach. The intervention consisted of 5 weekly sessions of yoga of 15 minutes each and composed of breathing techniques (pranayama), postures (pranayama), and lying down relaxation exercises (yoga nidra). The research site was a special needs school in South Auckland, New Zealand in an area characterized by poor socio-economic living conditions with a composite range of different ethnic groups. The findings of this study suggest that a regular practice of yoga can have numerous benefits for children on the Autism Spectrum Disorder (ASD). They found yoga to be a fun-filled and engaging experience. They improved significantly in their flexibility levels and general physical health. Emotionally, the children reported that the breathing techniques allowed them to feel calmer and more relaxed. The children felt that incorporating a regular practice of yoga within formal curriculum will be another effective tool to enhancing their overall health and well-being.  相似文献   
35.
36.
The University of Florida offers an online professional practice Ed.D. focused on Educational Technology. Twenty-three students have completed professional practice dissertations and graduated since the program’s inception in 2008. The purpose of this article is to share what these dissertations have looked like and to begin a dialogue about professional practice dissertations completed in online educational technology programs. Specifically, we (1) provide an overview of different ways professional practice Ed.D. dissertations are structured, (2) share guiding principles for professional practice dissertations in our Ed.D. program, (3) analyze the ways in which these guiding principles played out in the dissertations and (4) discuss the implications of our analysis for our program and for other online professional practice programs in Educational Technology.  相似文献   
37.
38.
39.
India is one of the oldest civilizations with a kaleidoscopic variety and rich cultural heritage. It has achieved multi-faccted socio-economic progress during the last 47 years of its independence. This article reports on a survey of the usage of modern technologies (e.g. photocopiers, microfilming, computers, facsimile transmission, audio-visual, online searching and CD-ROMs) in Indian libraries. These libraries include university, engineering, scientific, medical, government and public libraries. The study used a questionnaire, personal visits to many libraries and interviews. The paper examines the impact of modern technologies on these libraries. It concludes with a summary of the problems faced by the librarians in adopting the modern technologies and suggests measures for implementation of modern technologies.  相似文献   
40.
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