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   2315篇
  免费   144篇
  国内免费   9篇
电工技术   9篇
技术理论   2篇
综合类   269篇
化学工业   108篇
金属工艺   4篇
机械仪表   5篇
建筑科学   1617篇
矿业工程   14篇
能源动力   18篇
轻工业   141篇
水利工程   23篇
石油天然气   2篇
武器工业   1篇
无线电   18篇
一般工业技术   61篇
冶金工业   56篇
原子能技术   5篇
自动化技术   115篇
  2024年   6篇
  2023年   41篇
  2022年   79篇
  2021年   68篇
  2020年   81篇
  2019年   65篇
  2018年   25篇
  2017年   48篇
  2016年   27篇
  2015年   53篇
  2014年   213篇
  2013年   129篇
  2012年   145篇
  2011年   153篇
  2010年   187篇
  2009年   175篇
  2008年   191篇
  2007年   154篇
  2006年   128篇
  2005年   85篇
  2004年   61篇
  2003年   60篇
  2002年   72篇
  2001年   47篇
  2000年   31篇
  1999年   12篇
  1998年   5篇
  1997年   13篇
  1996年   5篇
  1995年   12篇
  1994年   10篇
  1993年   7篇
  1992年   9篇
  1991年   7篇
  1990年   13篇
  1989年   7篇
  1988年   11篇
  1987年   7篇
  1986年   8篇
  1985年   6篇
  1984年   6篇
  1983年   1篇
  1981年   1篇
  1980年   1篇
  1960年   1篇
  1956年   1篇
  1955年   1篇
排序方式: 共有2468条查询结果,搜索用时 46 毫秒
1.
为了生产优良食味稻米,克服栽培环境的影响非常重要。主要论述了灌浆期最适宜的用水管理、新鲜稻谷的干燥温度以及糙米水分含量与其食味之间的关系。水稻灌浆期最适宜的用水管理是湿润管理法,通过对灌浆期水稻的湿润管理,可有效抑制水田土壤温度上升,保持根系活力,提高稻米结实率,最终实现稻米增收与食味提升。新鲜稻谷水分含量不同,干燥所需的送风温度也不同,22%、25%、30%的水分含量分别对应的适宜温度为55、48、35℃。糙米中14%~15%的水分含量能够保证稻米的最佳食味。  相似文献   
2.
3.
Acrylamide is a probable human carcinogen and known human neurotoxin that can be generated in food through heating. Using a mathematical modelling approach, our previous study estimated long-term average dietary exposure to acrylamide in the Japanese people; however, the validity of these estimates remained unknown. Here, we aimed to obtain a more accurate estimate of acrylamide exposure that would reflect the usual practice of heat processing and consumption of foods in the population. We collected duplicate diet samples and dietary records during 24 h from a group of Japanese adults. A total of 110 duplicate diet samples were analysed for acrylamide by LC-MS/MS. Data from individual dietary records were used to examine the association between dietary acrylamide exposure and consumption of selected food groups (e.g., coffee, tea, confectioneries, and vegetables prepared at high temperature [deep-frying, stir-frying, sautéing, and baking]). Of the 110 homogenised diet samples, 108 contained detectable levels of acrylamide. Dietary exposure to acrylamide ranged from 8 to 1582 ng/kg body weight (bw)/day, with the mean value of 215 ng/kg-bw/day and median value of 143 ng/kg-bw/day. This mean value was higher than the value we previously estimated for Japanese adults using a mathematical approach. Multiple linear regression analysis showed log dietary acrylamide exposure was significantly associated with consumption of coffee and vegetables prepared at high temperature during 24-hr of sampling (adj. R2 = 0.250, p < 0.001). We revealed significant difference in dietary acrylamide exposure between participants who had coffee and vegetables prepared at high temperature (median, 169 ng/kg-bw/day; range, 35–1224 ng/kg-bw/day, n = 42) and those who had none of them (median, 75 ng/kg-bw/day; range, 8–311 ng/kg-bw/day, n = 15) (Steel-Dwass test, p < 0.05).  相似文献   
4.
Tocopherols, phytosterols, carotenoids, and squalene are present in mature seeds of Japanese quince. Yet, little is known about the relationship between these compounds and oil yield during fruit and seed development. The profile change of lipophilic compounds during fruit and seed development in Japanese quince cultivars “Darius,” “Rondo,” and “Rasa” is investigated. It is shown here that during fruit and seed development, there is a significant reduction, three‐ to over tenfold, in the concentration of minor bioactive compounds in seed oil. It is recorded that delay between synthesis of tocopherols and oil in Japanese quince seeds during the fruit development results in a logarithmic relationship between the oil content and tocopherols concentration in the seed oil (R2 = 0.980). Similar trends are observed between oil yield and phytosterols, and carotenoids (R2 = 0.927 and R2 = 0.959, respectively). The profile of fatty acids during the development of the seeds significantly is changed. The reduction of linoleic, palmitic, and gondoic acids levels and increment of oleic acid is noted. The oil content, profile of fatty acids, and concentration of bioactive compounds in all three genotypes of Japanese quince do not change significantly statistically during the last month of fruit development. Practical Applications: Some fruits are harvested at different degrees of maturity mainly due to a logistic issue and uneven ripening of fruits, which affects the chemical composition of whole fruit including seeds. Therefore, it would be good to know how the chemical composition is changing in plant material during development especially in the last month before harvest. Production of Japanese quince continues to rise year to year and with it the volume of generated by‐products such as seeds. This study demonstrates how it changes the oil content, profile of fatty acid, and concentration of tocopherols, squalene, phytosterols, and carotenoids in the seeds and seed oil of three Japanese quince cultivars “Rondo,” “Darius,” and “Rasa” during plant development. The provided information can be very useful for the manufactories oriented on the processing of by‐products, mainly seeds, generated by other branches of industry, for instance, fruit‐processing.  相似文献   
5.
专类园是一种强调专类植物收集、展示和植物造 景的园林形式,在植物园建设中具有重要地位。藤本植物因 其独特的观赏特征、生长习性及生态效应,近年已成为城市 园林绿化的重要造景材料。在分析华南植物园藤本植物专类 园建设背景、园址概况的基础上,结合其功能定位,提出了 科学性、功能性、地域性、艺术性及以人为本的规划原则; 确定了“一轴、三线、三点、五片区”的总体规划布局。在 文化线的园林构图及造景上,重点阐述了三大主题景观节 点——帷幄疏影、西关居、文昌亭的设计理念及其园林建筑 风格,探讨了岭南传统建筑、小品及文化在构建地域特色园 林景观中的作用;在植物线的园林造景上,简介了各景区的 植物布置方式及组景模式;在科普旅游线的组织上,介绍了 园区的园林小品造景意境及科普设施布置形式,以期为中国 藤本植物专类园建设提供参考。  相似文献   
6.
Xavier Kurten (?–1840) was a Prussian landscape gardener who worked for the Savoy family in the Piedmont region of Italy in the first half of the nineteenth century. He designed or redesigned all royal parks, creating a specific style based on the English naturalistic garden approach. This research was performed with the aim of investigating the development of the English landscape garden in Italy. Historical documents relating to Kurten’s biography and his work in Piedmont, including plans, were collected and analysed. We analyse and discuss the features that characterised his work: the relationship between the landscape—garden—house, the path system, the use of water, the vegetation, and the garden as a productive landscape. Kurten’s style is compared with the projects of William Kent and Lancelot ‘Capability’ Brown.  相似文献   
7.
8.
采石场伴随着人类文明而产生,也将伴随着人类社会的发展而长期存在。采石遗留的岩壁、岩石,以及地下水和雨水汇集形成的湖面水潭等构成了采石场景观的基础。采石场修复应当遵循自然规律,同时体现中国传统山水美学。南宁园博园7个采石场花园的设计,通过对场地景观特征的挖掘和恰当的人工介入,建立了融合于场地而又具有鲜明艺术特征的新景观体系。  相似文献   
9.
晚明江南造园兴盛,呈现出日益专业化的倾向,涌现出一批造园名家,周廷策即其中之一,其代表作为止园飞云峰。首先梳理周秉忠、周廷策父子的相关史料,总结其作品的艺术特征;继而结合诗文绘画对止园飞云峰进行复原分析,并从可望、可行、可游、可居4个角度探讨飞云峰的营筑意匠。指出以飞云峰为代表的周氏叠山,既继承了魏晋以来"小中见大"的叠山传统,又体现了晚明画意影响造园的时代新风,具有重要的艺术价值和历史地位。  相似文献   
10.
西雅图社区花园的用地获取、功能分区和元素组成   总被引:1,自引:0,他引:1       下载免费PDF全文
李倞 《风景园林》2019,26(11):113-119
社区花园在欧美具有悠久历史,在健康城市建设和促进社区发展方面的功效已经得到证实。目前,已针对社区花园的功能、类型、经营和科普等开展研究,但对土地获取和设计相关的研究较少。西雅图的社区花园历史悠久,并获得政府支持,是美国发展社区花园的城市典范。通过对西雅图23个典型案例进行调研,对用地获取方式、功能类型、分区和元素组成进行分类总结,为设计建造具有中国特色的社区花园提供启示。  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