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   1724篇
  免费   154篇
  国内免费   15篇
电工技术   12篇
综合类   59篇
化学工业   67篇
金属工艺   21篇
机械仪表   78篇
建筑科学   358篇
矿业工程   9篇
能源动力   44篇
轻工业   463篇
水利工程   18篇
石油天然气   23篇
武器工业   3篇
无线电   64篇
一般工业技术   168篇
冶金工业   123篇
原子能技术   20篇
自动化技术   363篇
  2024年   8篇
  2023年   31篇
  2022年   36篇
  2021年   68篇
  2020年   66篇
  2019年   44篇
  2018年   47篇
  2017年   54篇
  2016年   66篇
  2015年   67篇
  2014年   110篇
  2013年   129篇
  2012年   122篇
  2011年   116篇
  2010年   124篇
  2009年   106篇
  2008年   81篇
  2007年   88篇
  2006年   101篇
  2005年   78篇
  2004年   65篇
  2003年   60篇
  2002年   42篇
  2001年   28篇
  2000年   23篇
  1999年   23篇
  1998年   17篇
  1997年   13篇
  1996年   12篇
  1995年   7篇
  1994年   9篇
  1993年   7篇
  1992年   4篇
  1991年   4篇
  1990年   4篇
  1989年   2篇
  1986年   2篇
  1985年   4篇
  1984年   2篇
  1982年   1篇
  1981年   3篇
  1980年   3篇
  1977年   1篇
  1974年   2篇
  1973年   1篇
  1972年   2篇
  1968年   2篇
  1965年   2篇
  1963年   1篇
  1958年   3篇
排序方式: 共有1893条查询结果,搜索用时 15 毫秒
991.
BackgroundThe fruits of Malpighia glabra and M. emarginata (Family: Malpighiaceae) are commonly known as ‘Acerola cherry’ or ‘Barbados cherry’. Acerola fruits are well known for their high content of vitamin C, phenolic compounds, including benzoic acid derivatives, phenylpropanoids, flavonoids, anthocyanins, and carotenoids. In recent years, there is a growing interest in the role of Acerola as a nutraceutical or functional food with increasing market value. Extracts and bioactive compounds isolated from Acerola are studied for their various health promoting activities and biological activities such as antioxidant, antitumor, antihyperglycemic and skin protecting/skin whitening.Scope and approachThis article reviewed the scientific studies regarding the bioactive chemical constituents and the health beneficial effects of Acerola extracts and isolated compounds. These findings may help in future research concerning Acerola and Acerola based nutritional products.Key findings and conclusionsAcerola fruits can be considered as good candidates for the development of novel functional foods. However, detailed in vitro, in vivo and clinical studies, particularly mechanism-based studies are needed for the development of evidence-based functional food products in future.  相似文献   
992.
The use of health claims on foods with a poor nutritional composition could pose a risk of misleading some groups of consumers in their food choices. This study aimed to explore the influence of the use of claims on consumers’ preferences for yoghurts with a different nutritional composition and the influence of more and less familiar claims on food choices. The study was conducted on 371 consumers using conjoint methodology and further cluster analysis. Fruit yoghurt was used as a base product. We investigated the impact of the following product attributes on consumers’ preferences: presence/absence of a probiotic and fat metabolism claim; sugar content; and fat content. The results suggest that, while consumers generally consider the nutritional composition of yoghurt to be more important than the tested claims, some groups of consumers are more sensitive to the use of health-related statements. We observed the consumers’ generally positive preference for a familiar probiotic claim, and their negative preference for a non-familiar fat metabolism claim. Overall, these results indicate that some groups of consumers are more sensitive to the use of health-related communications and are therefore more exposed to the risk of being misled if the composition of the yoghurt they buy is in fact less favourable. It would be beneficial if nutrient profiles were introduced to limit the use of claims on foods.  相似文献   
993.
为修订GB5128—85皮蛋卫生标准,对标准执行情况进行了研究,收集统计分析了14省775份皮蛋卫生指标检测数据。根据皮蛋加工工艺的改进对皮蛋进行了分类,对铅等重金属指标进行了修订并增加了锌、铜等指标。建议皮蛋卫生指标:传统工艺生产的皮蛋铅≤2mg/kg,砷≤0.5mg/kg,pH≥9.5;非传统工艺生产的皮蛋铅≤0.5mg/kg,砷≤0.5mg/kg,铜≤10mg/kg,锌≤20mg/kg;硬心皮蛋及其它皮蛋铅≤0.5mg/kg,砷≤0.5mg/kg,pH≥9.5,菌落总数≤500/g;大肠菌群≤30MPN/100g,致病菌不得检出  相似文献   
994.
Baroness Sally Greengross has a long and deep knowledge of issues surrounding ageing. Until 2000 she was Director General of Age Concern for 13 years, and also joint Chair of the Institute of Gerontology at King's College London and Secretary General of Eurolink Age. She is now President/Chief Executive of the International Longevity Centre-UK (ILC-UK), an influential think-tank impacting policy on longevity, ageing and population change. Since 2000, she has been a crossbench (independent) member of the House of Lords and she chairs five All-Party Parliamentary Groups: Dementia, Corporate Responsibility, Intergenerational Futures, Continence Care, and Ageing and Older People (Co-Chair). Here, the Editor of AD, Helen Castle , interviews her on shifting attitudes to ageing and the importance of designing for the older population.  相似文献   
995.
Space travel is on the brink of a new era. Larry Bell , Professor of Architecture and Space Architecture at the University of Houston, describes how new ambitions are being reached for, such as the exploration of distant Mars, which will require longer and ever more complex missions. At the same time Space is being opened up internationally, with the participation of China and India, and space tourism is introducing privatisation and new commercial players.  相似文献   
996.
In 2013, Walter Menteth Architects entered the 2013 Royal Institute of British Architects (RIBA) Re-imagine Ageing Design Competition with an entry that focused on the delivery of customised housing to suit individual specifications. Here Walter Menteth , a director of the practice, describes the research the office undertook as part of the project and how it led to a solution that radically questioned the current procurement process for development-led retirement housing by proposing a new, distinctively ‘branded’ delivery vehicle that improves access to consumers while expanding buyer choice and engagement.  相似文献   
997.
Architectural historian and author Edward Denison and architect and researcher Guang Yu Ren lift the lid on the complex and urgent matter of China's ageing population. The impending crisis is not only a matter of numbers – a third of China's population are projected to be over 60 by 2050 – but also one of shifting social responsibility. Whereas the care of ageing relatives has traditionally been the individual family's responsibility – filial obligation being written into the constitution – urban migration and economic development and the legacy of the One Child Policy are disrupting this, creating a greater need for state and private housing provision for the elderly.  相似文献   
998.
健康信念模式在减重行为中的运用   总被引:1,自引:0,他引:1  
肥胖患病率在世界范围内呈上升趋势,已经成为发达国家和发展中国家面临的最严重的公共卫生问题之一。导致超重或肥胖的危险因素主要有膳食、运动、饮酒等行为因素,行为改变对于预防和治疗超重和肥胖至关重要,其防治措施主要是建立健康的饮食、生活方式。健康信念模式是一个有效且合适的管理体重的工具。利用健康信念模式建立支持性的环境,树立肥胖者的信心,提供健康教育保证肥胖者理解肥胖的危害以及和许多疾病的相关性,可以达到减轻体重的目的。  相似文献   
999.
The effect of personalized ventilation (PV) on people's health, comfort, and performance in a warm and humid environment (26 and 28°C at 70% relative humidity) was studied and compared with their responses in a comfortable environment (23°C and 40% relative humidity). Thirty subjects participated in five 4‐h experiments in a climate chamber. Under the conditions with PV, the subjects were able to control the rate and direction of the supplied personalized flow of clean air. Subjective responses were collected through questionnaires. During all exposures, the subjects were occupied with tasks used to assess their performance. Objective measures of tear film stability, concentration of stress biomarkers in saliva, and eye blinking rate were taken. Using PV significantly improved the perceived air quality (PAQ) and thermal sensation and decreased the intensity of Sick Building Syndrome (SBS) symptoms to those prevailing in a comfortable room environment without PV. Self‐estimated and objectively measured performance was improved. Increasing the temperature and relative humidity, but not the use of PV, significantly decreased tear film quality and the concentration of salivary alpha‐amylase, indicating lower mental arousal and alertness. The use of PV improved tear film stability as compared to that in a warm environment without PV.  相似文献   
1000.
As part of the US‐Japan co‐operative research programme, this report presented at the 1985 UJNR Panel Conference reviews two workshops, the first held at Tsukuba in 1983 and the second at Berkeley, California in 1984. The highlights of those workshops are discussed here, and some conclusions drawn.  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