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   128篇
  免费   8篇
  2024年   1篇
  2023年   1篇
  2022年   4篇
  2021年   3篇
  2020年   5篇
  2019年   9篇
  2018年   7篇
  2017年   7篇
  2016年   5篇
  2015年   7篇
  2014年   3篇
  2013年   24篇
  2012年   7篇
  2011年   4篇
  2010年   8篇
  2009年   4篇
  2008年   5篇
  2007年   4篇
  2006年   6篇
  2005年   5篇
  2004年   2篇
  2003年   2篇
  2002年   4篇
  2001年   1篇
  2000年   2篇
  1999年   1篇
  1998年   2篇
  1997年   1篇
  1996年   1篇
  1984年   1篇
排序方式: 共有136条查询结果,搜索用时 31 毫秒
21.
深圳工业化过程中同全国各省区建立起了资金、技术、市场以及人才(包括劳动力)方面的广泛联系。本文基于外来人口指标,构建了深圳户籍人口迁移模型,并加以测度及分析,从人口迁移角度得出以下结论:首先,深圳同全国各省区经济联系强度与两地的人口规模成正比;其次,与两地的交通距离成反比;第三,深圳与全国的经济联系呈辐射状的圈层结构;第四,外来户籍人口数与两地收入差距相关性不明显。进而分析了形成这种联系格局的其他影响因素,并对深圳加强与全国区域经济联系提出政策建议。  相似文献   
22.
东北地区经济空间极化及其驱动因子的定量研究   总被引:2,自引:0,他引:2  
在对区域经济空间极化相关文献研究综述的基础上,借鉴有关研究方法,遵循从过程到格局、机理,从整体到局部的研究思路,首先以人均GDP为测度指标,综合分析东北三省及其内部各区域经济差异与空间极化的过程与空间格局,接着以人均GDP的极化水平为应变量,以工业总产值、当年实际直接利用外资额、社会商品零售总额、全社会固定资产投资、全员劳动生产率和复合流量的极化水平为自变量,建立多元线性回归模型,分析区域经济空间极化的内在机理。结果表明:①区域经济发展存在空间极化现象,且整体呈现出南强北弱的态势;②哈长经济区和辽中南经济区已初步形成,其中哈长经济区处于明显的集聚阶段,而辽中南经济区扩散效应已开始发挥作用;③地区经济发展的位序排名及其变化表明区域经济发展中心逐步南移;④区域差异和空间极化总体变化趋势基本一致,呈现出先升后降,但总体水平呈上升的变化态势;⑤多元线性回归模型表明各动力因子的作用程度和作用趋势不尽相同,但工业总产值和全员劳动生产率是东北三省及其内部区域经济空间极化演变所共有的主导驱动因子,说明其区域经济发展是一个内生增长过程,并提出应强化市场体制转轨、国有企业改组改革、产业结构升级换代和政府政策的导向作用。  相似文献   
23.
易溶盐富集是陕西西安大雁塔砖体表面风化、结构破坏、强度衰减的主要原因。为分析盐害对大雁塔砖体结构、强度的影响机理,采用以饱和硫酸钠溶液为介质,对大雁塔砖体进行易溶盐结晶循环模拟劣化试验。在Na2SO4反复结晶、溶解过程中,测定试样的质量、波速及单轴抗压强度等指标,分析其变化规律。结果表明,在盐害作用下,试验砖体表现出与塔体表面类似的风化破坏现象;Na2SO4晶体在试样孔隙内不断发育,晶体挤压效应导致孔隙率增大,内部结构破损;质量、波速、单轴抗压强度随循环的次数呈先增加后减小的变化规律。砖体对盐害耐受力约为砖体质量的0.5%。  相似文献   
24.
旅游目的地文化变迁量化评价方法及实证研究   总被引:4,自引:0,他引:4  
为评价旅游目的地文化变迁的内容、方向、程度并掌握其变迁原因,本文设计了旅游目的地文化变迁评价指标体系,提出采用德尔菲法和AHP法确定各项指标的权重,并对青岛啤酒文化的变迁进行了实证研究,详细说明了旅游目的地文化变迁量化评价的方法。  相似文献   
25.
26.
When it comes to existing buildings, the estimation of the structural residual bearing capacity is required to evaluate the potential for reuse/conversion. The level of detail and accuracy of surveys dramatically affect structural diagnostics. In order to optimise the experimental survey process, a simulation of the structural life-cycle may be useful.

Based on a previously developed approach of Monte Carlo simulation implemented with a damage law for the life-cycle analysis of newly designed constructions, this paper presents the method application to a historic roof steel structure. It aims to identify critical situations, assess the residual life of the system, and plan possible retrofit strategies for the building conversion.

The case study is a steel frame roof structure of the ex pig abattoir within the complex of the municipal slaughterhouse in Monza (close to Milan, Northern Italy) and protected from the Cultural Heritage Authority. The life-cycle of the structure is here investigated over different stages of the building lifespan along with the damages caused by aging and negligence. The construction was built in 1902, and abandoned in 1984. Therefore, the periods analysed are: from construction to disuse and from disuse to today. The second phase of life, still on going, has significantly sped up the degradation.

The probabilistic evaluation of failure times is discussed and the possible interventions scenarios in terms of costs, and after-maintenance reliability and safety are investigated.  相似文献   

27.
The adsorption onto other minerals of charged gold nanoparticles, carried by gas ascending from the Earth’s interior, is an important component of their transport and deposition in surficial cover such as alluvial, aeolian, and glacial sediments. To simulate the adsorption of these particles, an experiment was conducted in which a flow of air that contained gold nanoparticles was passed upward through a sample of alluvium from the middle–lower reaches of the Yangtze River. These experiments showed that gold nanoparticles are adsorbed on kaolinite, halloysite, goethite, and hematite in the alluvial cover. Both the gold nanoparticles and minerals (i.e., kaolinite, halloysite, goethite, and hematite) carry surface charges that provide them with excellent adsorption properties. This study showed that the specific mineral composition of surficial alluvial cover affects the concentration of gold nanoparticles in the ascending gas. This phenomenon may plausibly be used in exploration for concealed gold, copper–gold, and silver–gold deposits in areas of thick alluvial cover. Geofluids (2010) 10 , 438–446  相似文献   
28.
Geomorphology in Canada, as elsewhere, has evolved into an essentially bipartite discipline focusing either on ‘process’ or broader ‘historical’ (Quaternary) landscape interpretation. A growing emphasis on process‐oriented research that relies increasingly on instrumentation and computational technologies has occurred. Critics of such research note limited applicability for landscape evolution, fashionability of methods and limited societal relevance. Indeed, some say we are not seeing the landscape for the processes. This article discusses the changing nature of geomorphology since the Quantitative Revolution of the 1950s including new advances, recent trends and challenges. Publication trends and recent advances suggest that the discipline is very healthy (following a slump in the early 1990s) and continues to evolve, which may reflect increasing research infrastructure and/or funding opportunities and new publications spotlighting Canadian research. Unfortunately, fundamental (less applied) research is threatened by funding program shifts, changing institutional pressures and a decline in research capacity from retirement attrition, and student recruitment challenges. Three research priorities are recommended: (1) continued fundamental research, (2) more integrated modelling to link micro scale processes to macro scale landform behaviour and (3) improvements in profiling our discipline amongst students and related professionals.  相似文献   
29.
The extraordinary record of prehistoric rock art depicting tens of thousands of animal images in the Coso Range of eastern California provides an opportunity to study the relationship between aboriginal hunting, forager ecology, bighorn prey population levels, and the production of rock art. We review archaeofaunal evidence that the Coso desert bighorn sheep population was strongly depleted during the Newberry era after 1500 B.C. We discuss the dating of the rock art and show a correlation between bighorn depletion and increased rock art production. These data are consistent with the arrival of Numic foragers ca. A.D. 600 who competed with the Coso Pre-Numics and eventually terminated the Coso rock art tradition. An ecological predator-prey computer simulation of the human populations (Numic and Pre-Numics), the sheep population, and the rock art “population”, demonstrates these proposed interconnections and gives a reasonable fit to the observed rock art production rate.  相似文献   
30.
This paper considers the potential contribution of secondary quantitative analyses of large scale surveys to the investigation of ‘other’ childhoods. Exploring other childhoods involves investigating the experience of young people who are unequally positioned in relation to multiple, embodied, identity locations, such as (dis)ability, ‘class’, gender, sexuality, ethnicity and race. Despite some possible advantages of utilising extensive databases, the paper outlines a number of methodological problems with existing surveys which tend to reinforce adultist and broader hierarchical social relations. It is contended that scholars of children's geographies could overcome some of these problematic aspects of secondary data sources by endeavouring to transform the research relations of large scale surveys. Such endeavours would present new theoretical, ethical and methodological complexities, which are briefly considered.  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