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   2002篇
  免费   61篇
  国内免费   13篇
电工技术   9篇
综合类   76篇
化学工业   50篇
金属工艺   8篇
机械仪表   11篇
建筑科学   1175篇
矿业工程   160篇
能源动力   60篇
轻工业   90篇
水利工程   172篇
石油天然气   4篇
无线电   23篇
一般工业技术   54篇
冶金工业   9篇
原子能技术   2篇
自动化技术   173篇
  2025年   15篇
  2024年   18篇
  2023年   22篇
  2022年   37篇
  2021年   52篇
  2020年   52篇
  2019年   47篇
  2018年   47篇
  2017年   30篇
  2016年   74篇
  2015年   83篇
  2014年   117篇
  2013年   104篇
  2012年   122篇
  2011年   118篇
  2010年   116篇
  2009年   115篇
  2008年   115篇
  2007年   121篇
  2006年   151篇
  2005年   87篇
  2004年   109篇
  2003年   81篇
  2002年   67篇
  2001年   37篇
  2000年   39篇
  1999年   35篇
  1998年   14篇
  1997年   9篇
  1996年   9篇
  1995年   11篇
  1994年   2篇
  1992年   2篇
  1991年   3篇
  1990年   2篇
  1989年   3篇
  1988年   1篇
  1987年   4篇
  1986年   2篇
  1985年   1篇
  1984年   1篇
  1981年   1篇
排序方式: 共有2076条查询结果,搜索用时 15 毫秒
1.
基于生态学思维的高校图书馆建设   总被引:2,自引:0,他引:2  
温新瑞 《机械管理开发》2007,(5):113-114,117
高校图书馆,是全校师生汲取知识的重要园地.高校图书馆的建设应遵循生态学的规律,不仅要重视其外部环境的建设,更重要的是加强图书馆的内涵素养,充分体现生态图书馆的持续发展观、和谐价值观与生态世界观的基本特征.  相似文献   
2.
Heavy metals have increased in natural woodlands and shrublands over the last several decades as a consequence of anthropogenic activities. However, our knowledge of the effects of these elements on woody species is scarce. In this study, we examined the responses of six Mediterranean woody species to increasing levels of zinc in hydroponic culture and discussed the possible implications for the restoration of contaminated sites. The species used, Pinus pinea L., Pinus pinaster Ait., Pinus halepensis Mill., Tetraclinis articulata (Vahl) Mast., Rhamnus alaternus L. and Quercus suber L. represent a climatic gradient from dry sub-humid to semi-arid conditions. Zinc concentrations in shoots ranged from 53 μg g− 1 in Q. suber to 382 μg g− 1 in T. articulata and were well below the levels found in roots. Zinc inhibited root elongation and root biomass and changed the root length distribution per diameter class, but the magnitude of the effects was species-specific. Only P. halepensis and Q. suber showed toxicity symptoms in aboveground parts. Species more characteristic from xeric environments (T. articulata, R. alaternus and P. halepensis) were more sensitive to zinc than species from mesic environments (Q. suber, P. pinaster and P. pinea). According to the Zn responses and bioaccumulation, Q. suber P. pinea and P. halepensis are the best candidates for field trials to test the value of woody species to restore contaminated sites. None of the species tested seemed suitable for phytoremediation.  相似文献   
3.
The French government has a 10-year history of negotiations with industry, resulting in voluntary agreements on energy consumption. When implemented, these voluntary agreements produced very few results in terms of global reduction of greenhouse emissions (Politiques et Management Public 11(4) (1993) 47), hence the idea of an energy tax became increasingly attractive for many French decision-makers. Ecological/Environmental Tax Reform (ETR) should have been one of the major political decisions and successes of the past leftwing coalition government. Instead it became one of its major failures as the Constitutional Court decided to terminate the energy tax project in December 2000. Through insights gleaned from focus groups and interviews with business-people and decision-makers, an attempt is made to understand the failure of the energy tax project. Firstly, decision-makers lacked crucial information about public and business opinions and secondly, there were conflicts between the relevant administrations. The fuel revolts of 2000 ended any hope of resolving the conflicts and implementing ETR, which was ultimately found unconstitutional. This paper examines the political controversies raised by the ETR project and the reasons for its eventual collapse, in the hope of contributing new understanding to the body of knowledge on the political difficulties of introducing environmental policy instruments.  相似文献   
4.
Environmental tax reform (ETR) is widely accepted to be a policy with desirable environmental, and other economic effects. The question arises then as to why its implementation has been so patchy. There is a broad literature on the economic impact of ETR, however, there have been very few research efforts devoted to understanding the roles and imperatives of the public, policy makers, businesses and other stakeholders who are addressed by ETR. This paper examines the impediments to ETR in Ireland. Focus groups were formed comprising of members of the general public and these provided a forum for detailed reactions to the ETR concept. Interviews were conducted with policy makers and key business people in an attempt to identify both the patterns of thinking behind ETR and the main obstacles to its introduction. Having presented the results, a theory of the main impediments to ETR is developed. The opinions of the members of the public, the business community and the policy makers highlight a number of issues that need to be addressed in the future design of ETR in Ireland. The principal potential impediments to ETR include: mistrust of the government, implausibility of the policy, means of hypothecation, information asymmetries, the political system, the structure of government, the macroeconomic environment, the impact on competitiveness, inequity between sectors, regressivity, elasticities and the level of the tax, terminology, and the marketing of ETR.  相似文献   
5.
Unity3d产品虚拟展示技术的研究与应用   总被引:14,自引:0,他引:14  
本文是在介绍虚拟现实技术的基础上,阐述应用专业引擎Unity3D为工具,实现虚拟产品模型展示的设计流程以及各个环节,最终开发出基于网络的,数据精准.表现力强,交互性强的工业产品虚拟展示应用系统。通过搭建一个跨越时空局限性的交流互动平台,实现企业与消费者之间更加方便快捷的产品信息交流,满足信息化时代人们对高速高效电子商务的需求。  相似文献   
6.
数字媒体时代下,人们所看到的广告已经不再是单纯的平面化、实体化的户外印刷广告,更多的是以数字媒体为载体的互联网终端广告,影视广告就是典型的存在。为了博得大众眼球、达到广告宣传效果,部分影视广告在内容和形式表现上忽视了生态伦理价值。文章通过对案例分析得出在生态伦理意识上公益影视广告对比商业影视广告的优势,并提出解决商业影视广告生态伦理问题的方法与策略。  相似文献   
7.
在家具产品的展示空间中涉及色彩的因素很多,色彩以其独特的魅力丰富了视觉空间;本文针对展示空间中色彩的特点探讨了面向家具展示空间的色彩创意。  相似文献   
8.
《造纸信息》2014,(5):73-73
In order to promote the development of China's paper industry, display the technical achievements of a conlmu of paper nication paper industry, and provide platform for the enterprises and relative industries, China Paper Association,  相似文献   
9.
山区是首都的生态涵养区,在落实首都山区生态功能定位的同时,促进山区经济发展是当前面临的重要任务。以怀柔区为例,在阐述林下经济内涵的基础上,对生态涵养区发展林下经济进行了条件分析,论述了适合生态涵养区发展的两种林下经济模式,即林菌模式和林禽模式,并对发展林下经济提出了一些建议。  相似文献   
10.
生态条件对不同烤烟品种烟叶产质量的影响   总被引:75,自引:1,他引:75  
对云南省推广种植的 6个主要品种进行了不同生态条件的对比试验。结果表明 :生态条件对烟株田间长相长势、烟叶的产量和产值、化学成分、致香物质含量和烟叶评吸质量的影响大于品种造成的影响。因此 ,烤烟品种的合理布局是生产优质烟叶的关键措施之一。  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