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   7029篇
  免费   335篇
  国内免费   268篇
电工技术   185篇
技术理论   8篇
综合类   896篇
化学工业   588篇
金属工艺   149篇
机械仪表   228篇
建筑科学   1715篇
矿业工程   208篇
能源动力   111篇
轻工业   569篇
水利工程   210篇
石油天然气   744篇
武器工业   32篇
无线电   204篇
一般工业技术   432篇
冶金工业   746篇
原子能技术   57篇
自动化技术   550篇
  2024年   9篇
  2023年   37篇
  2022年   79篇
  2021年   110篇
  2020年   138篇
  2019年   99篇
  2018年   101篇
  2017年   149篇
  2016年   155篇
  2015年   163篇
  2014年   312篇
  2013年   381篇
  2012年   341篇
  2011年   430篇
  2010年   346篇
  2009年   405篇
  2008年   379篇
  2007年   495篇
  2006年   494篇
  2005年   423篇
  2004年   389篇
  2003年   369篇
  2002年   323篇
  2001年   266篇
  2000年   228篇
  1999年   175篇
  1998年   140篇
  1997年   102篇
  1996年   97篇
  1995年   56篇
  1994年   68篇
  1993年   43篇
  1992年   50篇
  1991年   25篇
  1990年   22篇
  1989年   23篇
  1988年   21篇
  1987年   21篇
  1986年   12篇
  1985年   15篇
  1984年   14篇
  1983年   11篇
  1981年   6篇
  1974年   7篇
  1968年   6篇
  1961年   5篇
  1959年   10篇
  1957年   7篇
  1955年   5篇
  1954年   14篇
排序方式: 共有7632条查询结果,搜索用时 15 毫秒
1.
Construction of this 67 m high RSS was completed in December 2006. After seven years in-service, a tension crack was observed at the top of the slope. In March 2015 this RSS structure catastrophically collapsed. This RSS structure collapsed in a compound failure mode; as the failure plane passed beneath, partially behind, and partially through the reinforced soil mass. The failure plane beneath the RSS was along a shale-claystone interface. The failure surface partially behind the RSS was along sandstone bedrock with water-seeping bedding planes dipping out of the rock mass. The failure surface through the upper portion of the RSS is where the geogrid reinforcement was overwhelmed by stresses originating from underlying deformation. The RSS collapse occurred after 8.3 years in-service as the shear strength along the shale-claystone interface decreased and approached the fully softened strength. The primary causative factors of this failure are: (i) an insufficient subsurface investigation program and interpretation of data for design and detailing; (ii) insufficient specifications and construction plan details for both foundation preparation and rock backcut benching; (iii) insufficient foundation preparation and rock backcut benching during construction; and (iv) adaptations to the design made during construction.  相似文献   
2.
This study investigates a video game's effects on implicit and explicit attitudes towards depicted historical events in the short- and long-term on a sample of 148 young adults. We used, as an intervention tool, a serious game Czechoslovakia 38–89: Borderlands that deals with the expulsion of the Sudeten Germans from the former Czechoslovakia after the WWII. Results showed more negative pretest-posttest explicit attitude changes towards the expulsion on a general level (d = −0.34) and a specific level (d = −0.53) compared to the control group. Over the long-term, group differences in attitude change remained significant for the specific level (d = −0.44), but not for general one (d = −0.16). Exploratory analysis on the item level indicated that especially attitudes towards the expulsion's (un)fairness were affected by the game. However, no significant changes were found in implicit attitudes in the experimental group. This study is the first of such scale to empirically investigate video games' effects on a society's historical awareness.  相似文献   
3.
进行了圆柱振动台试验,对模型的加速度反应数据进行获取。试验表明,随着地震的加速度峰值的不断增加,圆柱顶部加速度极值不断增加。柱顶的加速度响应有着增大的趋势,且极值比输入的加速度的极值有一定的放大。  相似文献   
4.
5.
刘禹彤  杜文君 《园林》2021,(3):9-14
汉代是中国园林的形成阶段,不仅园林建筑物有所增加,成为住宅的延伸与扩展,而且人工造景比重也增大,造园要素趋于完备。园林的内容与功能随着社会生活的改变而逐步多样和完善,不仅是射猎、走狗、跑马的场所,还可以是游船、宴乐、赏鱼虫走兽、观看百戏的地方。造园在布局上也采用灵活多变的手法,按功能的需要,穿插安置不同形式的厅堂、楼阁、亭榭等。通过对鲁灵光殿时代背景及汉代园林、建筑营造形式的深入研究,结合文献的相关记述,梳理出鲁灵光殿的沿革,并以此为依据,对鲁灵光殿进行复原。  相似文献   
6.
传统文化电视节目在探索发展的过程中,选题逐渐聚焦中国风物人文,视野逐步向百姓生活延伸,立意兼顾文化内涵与百姓情感需求,编排制作节目内容与造型双发展。在此基础上,传统文化节目迎来更大的繁荣。  相似文献   
7.
With more than one billion people lacking access to electricity in the world, ensuring universal access to electricity by 2030 remains a major challenge which cannot be left to the government initiatives alone. Access to local information and identification of potential areas for investment can be a challenge for investors. This paper provides a tool for preliminary assessment of potential markets for off-grid electrification in developing countries and applies this to Ghana to demonstrate its applicability. A multi-criteria approach is used to rank the districts according to the overall potential and the best markets and least favourable areas for investment are identified. The tool offers flexibility to include new inputs to the analysis and the factor weights can be adjusted as appropriate. The case study shows that the tool can effectively identify potential areas from a list of candidates and offers support to analysts.  相似文献   
8.
This paper looks at the role of state and society in the history of epidemic governance in China for an appreciation of the way China manages the current COVID-19 epidemic.  相似文献   
9.
We tell the story of the Lise Meitner-Minerva Center, its establishment and activities, its members and their scientific activity, and its instrumental role in weaving intense relationships with the theoretical community in Germany, and in amalgamating the Israeli community of computational quantum chemistry into a national center that enjoys a high international reputation.  相似文献   
10.
The lack of consensus on the meaning of energy security and how it should be measured hinders the evaluation of alternatives for improving the Cape Verdean energy sector. The objective of the paper is to develop an energy security index adjusted to the country's context. The methods used are the multi-criteria analysis and the Delphi survey. Different alternatives to improve energy security are assessed: electrically interconnect Cape Verde's islands, increase the share of renewable energy, and a combination of the previous alternatives. The results of our analysis indicate that increasing renewable energy is the optimal alternative for Cape Verde.  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