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   1955篇
  免费   235篇
  国内免费   57篇
电工技术   88篇
技术理论   7篇
综合类   238篇
化学工业   200篇
金属工艺   18篇
机械仪表   64篇
建筑科学   610篇
矿业工程   126篇
能源动力   181篇
轻工业   64篇
水利工程   180篇
石油天然气   64篇
武器工业   1篇
无线电   60篇
一般工业技术   119篇
冶金工业   80篇
原子能技术   3篇
自动化技术   144篇
  2024年   14篇
  2023年   55篇
  2022年   123篇
  2021年   136篇
  2020年   140篇
  2019年   111篇
  2018年   96篇
  2017年   101篇
  2016年   93篇
  2015年   78篇
  2014年   173篇
  2013年   214篇
  2012年   79篇
  2011年   108篇
  2010年   80篇
  2009年   91篇
  2008年   76篇
  2007年   89篇
  2006年   75篇
  2005年   69篇
  2004年   77篇
  2003年   39篇
  2002年   40篇
  2001年   26篇
  2000年   23篇
  1999年   14篇
  1998年   6篇
  1997年   3篇
  1996年   2篇
  1995年   3篇
  1994年   2篇
  1993年   1篇
  1992年   3篇
  1991年   1篇
  1990年   2篇
  1989年   1篇
  1987年   1篇
  1985年   1篇
  1984年   1篇
排序方式: 共有2247条查询结果,搜索用时 594 毫秒
81.
The concept of territoriality and its relationship to the focus and substance of spatial planning is the subject of much interest at the present time and this paper seeks to contribute to the debate by stepping into the sea. The first part of the paper establishes a framework for considering the spatial planning implications of changing conceptions of territoriality, outlining key sources of territorial innovation and their implications in terms of the development of new units and styles of governance, new challenges for planning practice, and the potential for feedback informing the development of planning theory. The application of the framework is then illustrated in the second part of the paper with reference to the emerging field of maritime spatial planning and in particular to the pioneering work that is being undertaken in Europe. This work is testing established notions of territoriality by highlighting the strong and growing connections between the land and the sea. Here some of the key implications for future spatial planning practice are identified. These indicate that there is a growing recognition of the need for innovation in the territorial units of governance in maritime regions and in the themes, processes and methods of spatial planning in these areas. The paper concludes with some observations on the implications of these findings for the theory of spatial planning.  相似文献   
82.
83.
汽车排放的氮氧化物(NOx)和碳烟颗粒物(PM)会对环境和人类健康造成严重的危害,但是现有的技术仅能对NOx或PM的排放实现单独净化。与其他尾气净化技术相比,柴油机颗粒物-氮氧化物减排系统(DPNR)兼具NOx和PM净化效果,成为下一代NOx和PM协同净化的首选催化系统。本文综述了DPNR催化反应机理以及系统中NOx和PM系统净化用的贵金属催化剂的研究进展;总结了Pt基催化剂在不同条件下同时消除NOx和PM的催化活性,系统地讨论了Ba、K、Mn等元素掺杂对Pt基催化剂的影响。同时归纳比较Ag基、Ru基与Pt基催化剂在PM氧化和NOx消除方面的区别,为研究开发同时消除NOx和PM的高效催化剂提供参考。  相似文献   
84.
A wave of recent cross-national research has pointed to the positive consequences for countries with high levels of “quality of government” (QoG), broadly defined, such as corruption, impartiality, and quality of public services. Yet the question of how QoG varies at the sub-national level is still widely overlooked, in particular with measures that are available over time. To address it, we present the third round of data from the regional European Quality of Government Index (EQI) survey corruption (D73), Europe (N44) governance (H11); sub-national (R50), time series (C22), collected in 2017 and built upon the opinions of 78,000 respondents in 193 regions from 21 European countries. The data provides several contributions to the literature. First, while the majority of QoG-type indices rely on expert assessments, the EQI relies on the assessments of citizens, who are the on-the-ground consumers of public services. Second, the data begins to show trends on QoG variation over time, as well as across European regions. Consequently, this data is the most comprehensive sub-national data to date; mapping of QoG within and across EU countries over the past decade. Building on previous rounds of data collected in 2010 and 2013, the 2017 EQI, which is published free for scholarly use, builds on both perceptions and experiences of citizens in public service areas such as health care, education, and law enforcement. This paper presents the results of the latest survey, improved with respect to the previous ones, discussion of trends across space and over time, as well as interesting avenues for future research that we detect across European regions.  相似文献   
85.
Social movement-initiated co-production has been increasingly described as an approach that enables urban poor communities in the South to gain wider access to urban governance. However, with a predominant focus on project-level interventions, the case studies in which movements truly affect governance matters in a metro scale are rare. One of the examples involving such an achievement is the activism of civil society organisations and urban poor groups in Metro Manila, Philippines, which have succeeded to have a major impact on the housing and resettlement programme; the Oplan LIKAS. This article analyses how the civil society was able to gain such a position and the way it utilised it. The documentation of the challenges experienced by the civil society reflects the nature of co-productive engagement in the South and shows that it may easily reach its limits in an exclusionary governance setting.  相似文献   
86.
Public authorities that seek to transfer the cost of managing green spaces to the private sector face apprehension about the extent of community input in managing of public green spaces in cities. In practice, the governance arrangements for managing public green spaces are neither a purely private or public sector responsibility. They are part of complex and contested governance schemas that involve multiple stakeholder groups with varying interests and responsibilities. This paper proposes a simple framework to support different modes of governance appropriate for the management of public green spaces in cities. The framework classifies stakeholders’ desires for engagement based on ecosystem service characteristics defined on a spectrum of excludability and rivalry. The framework is applied to case studies in Australia and Canada. Finally, we discuss the new insights for governance arrangements for public green space management in cities.  相似文献   
87.
现阶段,EPC 模式在我国工程领域得到日益广泛应用。针对 EPC 模式下如何从业主与总承包商关系治理角度改善项目管理绩效的问题,采用结构方程模型,通过对 309 个 EPC 项目有关数据进行检验,以关系行为中“合作”作为中介变量,探讨并验证了关系治理多因素对项目管理绩效的影响程度和改善机理。研究表明,关系治理中信任、承诺、沟通和惯例4 个关键要素可有效促进双方合作,从而改善 EPC 项目管理绩效。进一步明确了 EPC 模式下“关系治理—合作—项目管理绩效”的关联路径。关系治理理论及方法在 EPC 项目中合理使用,将对我国工程领域大力推广 EPC 模式具有现实意义。  相似文献   
88.
采用CoFlame程序模拟研究了高压下H2/CO稀释剂对乙烷/空气层流扩散火焰中碳烟形成的影响。结果表明:H2和CO添加之后,火焰温度均略有增加,且碳烟体积分数随着H2/CO稀释比的增加而降低。H2的添加使得碳烟表面生长区域的H自由基浓度增加,减少了初始碳烟颗粒成核及表面生长的活性位点数,导致脱氢加乙炔(HACA)反应中氢提取速率减缓以及碳烟颗粒表面生长速率减缓。CO的添加使得苯(A1)和芘(A4)摩尔分数减少,减缓了碳烟成核速率,导致碳烟的生成受到抑制。  相似文献   
89.
The aim of this work is to make progress towards the development of 3D reconstruction as a legitimate alternative to traditional 2D characterization of soot. Time constraints are the greatest opposition to its implementation, as currently reconstruction of a single soot particle takes around 5–6 h to complete. As such, the accuracy and detail gains are currently insufficient to challenge 2D characterization of a representative sample (e.g. 200 particles). This work is a consideration of the optimization of the steps included within the computational reconstruction and manual segmentation of soot particles. Our optimal process reduced the time required by over 70% in comparison to a typical procedure, whilst producing models with no appreciable decrease in quality.  相似文献   
90.
针对东庞矿21217工作面瓦斯涌出量大,影响矿井高产高效采掘工作,且紧靠风排不能解决瓦斯超限问题。针对该工作面实际情况,对工作面实施采前预抽、边采边抽,高位钻孔对采空区瓦斯抽放,风筒对隅角瓦斯抽放,成功解决了高瓦斯矿井瓦斯治理问题,为类似矿井瓦斯治理提供技术经验借鉴。  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