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   818篇
  免费   46篇
  2024年   1篇
  2023年   15篇
  2022年   21篇
  2021年   21篇
  2020年   51篇
  2019年   48篇
  2018年   53篇
  2017年   60篇
  2016年   52篇
  2015年   33篇
  2014年   42篇
  2013年   105篇
  2012年   41篇
  2011年   53篇
  2010年   42篇
  2009年   36篇
  2008年   21篇
  2007年   35篇
  2006年   24篇
  2005年   21篇
  2004年   21篇
  2003年   14篇
  2002年   19篇
  2001年   11篇
  2000年   13篇
  1999年   5篇
  1998年   3篇
  1997年   1篇
  1996年   2篇
排序方式: 共有864条查询结果,搜索用时 15 毫秒
61.
Inner Scandinavia is one of the Swedish‐Norwegian INTERREG‐A three sub‐programmes, and has been working in operationalizing cross‐border projects in the border area since 1994. To date, several cross‐border strategies have been implemented, one for each programming period of the INTERREG‐A programme. This article investigates whether these strategies can be regarded as a type of cross‐border planning mechanism in promoting territorial development of the border region. It does so by developing a typology, which captures the essentials of spatial planning, against the background of which the article also analyses Inner Scandinavia governance structures, which involves a whole set of interconnected territorial partnerships between five border counties: Hedmark, Østfold, Akershus (Norway), Värmland and Dalarna (Sweden). Here, the main goal is to see if the Inner Scandinavia governance structure, which was recently altered by the inclusion of the Hedmark–Dalarna cross‐border committee, also known as TRUST, is favourable to the implementation of a genuine and long‐term cross‐border spatial plan, with the ultimate goal of reducing the barrier effect and improving the territorial capital along the cross‐border region. Project dokuments and interviews indicate that the existing cross‐border governance model in Inner Scandinavia, led by the INTERREG‐A Steering Committee, produced substantial progresses in reducing the barrier effect, in all its dimensions, and in supporting the territorial development across the border area. Consequently, the role of other cross‐border governance structures should be confined to promoting the active involvement and mobilization of local and regional actors in the cross‐border cooperation process, and in implementing several cross‐border projects with local/regional significance.  相似文献   
62.
63.
64.
This work concerns the stability of unreinforced masonry slender circular cross-sectional columns subjected to their own weight and eccentric vertical load. Cantilever columns are examined, considering that the material has infinitely linear elastic behavior in compression and has no tensile strength. For the analysis, an existing numerical model and solution procedure developed for the stability analysis of masonry elements with rectangular cross-section are utilized and adapted to the circular columns. For the instability of the columns, an appropriate criterion that relates the top lateral deflection to the intensity of the applied eccentric vertical load is employed. By considering a reference column, critical buckling load is obtained, behavior of the column interpreted and efficiency of the numerical model emphasized. Performing a nonlinear buckling analysis using a general purpose software on this reference column, obtained results are compared with those of the adapted procedure of the present study. Implementing parametric analyses on reference column, effects of the column slenderness, eccentricity of vertical load, elastic modulus, and self-weight on the buckling load are investigated. Presented calculation procedure provides a useful tool in order to calculate the critical loads or to check the stability of masonry circular columns.  相似文献   
65.
F. Wendler  A. Okamoto  P. Blum 《Geofluids》2016,16(2):211-230
Mineral precipitation in an open fracture plays a crucial role in the evolution of fracture permeability in rocks, and the microstructural development and precipitation rates are closely linked to fluid composition, the kind of host rock as well as temperature and pressure. In this study, we develop a continuum thermodynamic model to understand polycrystalline growth of quartz aggregates from the rock surface. The adapted multiphase‐field model takes into consideration both the absolute growth rate as a function of the driving force of the reaction (free energy differences between solid and liquid phases), and the equilibrium crystal shape (Wulff shape). In addition, we realize the anisotropic shape of the quartz crystal by introducing relative growth rates of the facets. The missing parameters of the model, including surface energy and relative growth rates, are determined by detailed analysis of the crystal shapes and crystallographic orientation of polycrystalline quartz aggregates in veins synthesized in previous hydrothermal experiments. The growth simulations were carried out for a single crystal and for grain aggregates from a rock surface. The single crystal simulation reveals the importance of crystal facetting on the growth rate; for example, growth velocity in the c‐axis direction drops by a factor of ~9 when the faceting is complete. The textures produced by the polycrystal simulations are similar to those observed in the hydrothermal experiments, including the number of surviving grains and crystallographic preferred orientations as a function of the distance from the rock wall. Our model and the methods to define its parameters provide a basis for further investigation of fracture sealing under varying conditions.  相似文献   
66.
本文从三个方面论述了东亚经济发展模式。首先,从历史的角度分析了东亚经济发展模式的产生、特点及其局限性。然后,进一步指出在经济全球化和信息化加速发展新的历史条件下,东亚发展模式已不能适应时代发展的要求,东亚发展模式与这次东亚经济危机存在着内在的必然的联系。最后,对东亚经济发展模式的发展与变革提出了自己的观点。  相似文献   
67.
如何实现有效治理是旅游目的地可持续发展中的重要议题。以阳朔遇龙河景区为个案,归纳其治理模式空间分异的类型与特征,解读不同模式对旅游发展的影响效应,发现:①村企共治模式中,各治理主体形成互助依赖的伙伴关系,资本互补、信任互惠、层级协同、信息对称、相互监督,能够兼顾效益、秩序与公平,游客满意度最高,呈现良性可持续发展态势;②社区主导模式中,治理主体权力失衡、信息不对称、短期工具理性、监管机制难以发挥持续实效,导致旅游秩序最差,游客满意度最低,不利于长远可持续发展;③政府主导模式中,政府公司治理能力不足,缺乏有效激励机制,导致商业效益较差,未能实现资源最优配置。  相似文献   
68.
以广东省五华县为例,以行政村为单元,在政策指标测算法的基础上,从自然环境状况、经济保障能力和社会因素等3方面构建理论潜力修正模型,将理论潜力修正为可实现潜力,并根据土地适宜性评价估算增加耕地潜力,以期为科学编制农村土地整治规划提供依据。研究表明,五华县农村居民点用地布局分散、规模小、空间差异显著,呈现出沿河谷、沿交通线路分布的典型特征。到2020年,农村居民点整治理论潜力为5683.91 hm2,北部村庄的整治潜力较大;可实现潜力修正系数为0.54,与理论潜力相差较大,各行政村之间差异明显;新增耕地潜力系数介于0.32-0.94,预计新增耕地1943.41 hm2,琴江、五华河沿线村庄的新增耕地潜力较大。建议实施差别化的农村居民点整治对策,推进五华县农村土地整治。  相似文献   
69.
张鹏丽  李育 《人文地理》2015,30(5):65-70
以兰州市为例,使用ASTER 30米分辨率的数字高程模型DEM并提取了兰州市周边所有地名信息;通过收集、整理地名,主要地名类型有:滩、坪、台、山、沟、湾、屲(洼)、岭、岘、梁、岗、咀等;通过地名与地貌分析,发现兰州地名命名及分布在很大程度上能够反映兰州市的地形地貌,且兰州地名类型的分布随高程呈现出一定规律;每一高程面上的地名数量与该高程面上兰州市的面积变化并没形成对应关系,在1800-1900 m、2100-2800 m高程,地名数量与面积对应较好;通过分析进一步证明了我国地名命名系统和地貌之间的关系,说明在我国文化地理及自然地理等学科的发展中具有融合现象。  相似文献   
70.
张勇  何深静 《人文地理》2015,30(2):65-71
借助对城市企业主义的简明定义,即以"企业化表述"和"企业化方式"来实施"企业化战略",通过考察中部小城河南省济源市20年来的发展历程,发现其城市企业主义经历了由萌芽到深化的"全球城市化"进程。进一步分析表明:在中国,城市企业主义是多重尺度共同作用的产物;市场化和全球化构成相互交织的推动力量;城市体系中的位置直接影响城市企业主义的战略与行动内容。  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