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   255篇
  免费   5篇
  国内免费   6篇
林业   18篇
农学   8篇
基础科学   15篇
  11篇
综合类   193篇
农作物   8篇
水产渔业   1篇
畜牧兽医   7篇
园艺   5篇
  2023年   1篇
  2022年   4篇
  2021年   2篇
  2020年   5篇
  2019年   5篇
  2018年   3篇
  2017年   13篇
  2016年   10篇
  2015年   4篇
  2014年   9篇
  2013年   16篇
  2012年   25篇
  2011年   50篇
  2010年   20篇
  2009年   17篇
  2008年   16篇
  2007年   32篇
  2006年   5篇
  2005年   7篇
  2004年   3篇
  2003年   4篇
  2002年   2篇
  2001年   4篇
  2000年   1篇
  1999年   4篇
  1998年   1篇
  1996年   2篇
  1990年   1篇
排序方式: 共有266条查询结果,搜索用时 62 毫秒
261.
徐霞 《安徽农业科学》2007,35(16):4980-4981
分析了城市土地供求的现状和城市土地与粮食安全之间的矛盾,并指出了城市土地集约利用是解决这一矛盾的根本途径,最后分析了城市土地的集约利用对城市土地的供给与需求的影响。  相似文献   
262.
刘卫华  赵潘 《安徽农业科学》2007,35(26):8361-8362
介绍了用于解决多人合作对策问题的Shapley值法,并将之应用于供应链伙伴企业的利益分配,建立了利益分配模型。  相似文献   
263.
Large amounts of urban wood resources are generated through tree removals in urban areas. Therefore, there is a growing interest to improve the environmental performance of the urban wood supply chain by quantifying the environmental impacts of creating high-value products from urban tree removals to enhance its utilization. By surveying existing urban wood utilization operations for primary data in two major cities: Baltimore, Maryland, and Milwaukee, Wisconsin, a new life cycle inventory (LCI) dataset per m3 of dry urban hardwood lumber and live edge slabs was created. Incorporating the new LCI data into life cycle assessment method, the total global warming (GW) impact of converting urban trees to kiln-dried lumber was estimated to be 122 kg CO2 eq and 336 kg CO2eq per m3 of lumber produced for Baltimore and Milwaukee, respectively. In both cases, the total environmental impact of the product was dominated by the conversion of urban trees to kiln dried lumber at the sawmill processing stage. Using scenario analysis for the source of heat generation used in kiln (force) drying wood, substituting wood fuel from coproducts for natural gas in a boiler for Milwaukee resulted in a substantial reduction in fossil-derived GW impact. Urban and traditional hardwood lumber production follow similar GW impact trajectories over their life-cycle stages with the lumber processing stage having the highest environmental impacts for both. Increasing the overall lumber yield and decreasing kiln (force) drying would substantially improve the environmental performance of urban hardwood lumber and help make it comparable to traditional lumber.  相似文献   
264.
构建园林材料信息平台,即通过电子化和信息化手段,打造一个面向园林行业的供应链电子商务平台。系统包括浏览、查询、统计、发布、数据管理等功能,通过web端和APP客户端等多途径信息化工具,为全国的园林采购商、供应商、设计、工程人员等提供询价、报价、在线交易、数据分析等一系列服务。  相似文献   
265.
Small-size green spaces contain convenient service capabilities for urban residents and satisfy the daily needs of citizens for high-quality ecological products. A greenway is a kind of linear green space, which can create a beautiful and livable environment in a high-density urban area. This study explored whether the services provided by the greenway can meet the daily needs of urban residents for green space in Guangzhou, a mega city in south China. Based on the Analytic Hierarchy Process (AHP) method and the entropy weight (EW) method, both the coupling coordination degree model and spatial autocorrelation analysis were adopted to quantify and determine the coordination degree of greenway service supply and public demand in Guangzhou. The results showed that the comprehensive score of the greenway service supply (GSS) subsystem and the public demand (PD) subsystem in Guangzhou was 0.3865 ± 0.08 and 0.3778 ± 0.03 (mean±s.e., n = 11), respectively. The GSS subsystem score was slightly higher than that of PD subsystem (P > 0.05), indicating that the two subsystems had no significant differences. The supply and demand subsystem of ten districts (excluding Conghua) in Guangzhou achieved different levels of coordination, and the average coupling coordination degree was 0.5885, suggesting that the districts were barely balanced at the city level. The Moran's I value was 0.580, indicating that the coupling coordination degree had significant positive global spatial autocorrelation and showed a spatial agglomeration effect. Furthermore, the local Moran’s I spatial autocorrelation showed that three districts (i.e., Yuexiu, Haizhu and Liwan) formed a high supply-high demand cluster and a spatial difference was detected when coupling the GSS and PD in Guangzhou. Therefore, we proposed the differentiated optimization strategies based on the results of the coupling coordination degree and the development status of each district and the entire city. This knowledge can better guide the subsequent construction and development of greenway in Guangzhou and may be useful for adjacent cities in Asia-Pacific region.  相似文献   
266.
Several studies from the Nordic countries show that cemeteries not only fulfil an important societal function as places for the disposal of bodily remains; they are also recreational landscapes that people visit to reflect, experience nature or perhaps go for a walk with the dog. In this comparative study, based on PPGIS data collected between 2018 and 2020 from residents in Copenhagen (Denmark) and Helsinki (Finland), we explored the extent to which residents use urban cemeteries as everyday recreational landscapes. We also assessed users’ characteristics and the values they attached to the cemeteries. The results show that several of Copenhagen’s cemeteries were actively used for recreation, while those in Helsinki were used much less frequently for this purpose. Of the total 7276 mapped visiting points in Copenhagen, 16.5% were located within cemeteries, compared with 1.9% of the 4298 mapped visiting points in Helsinki, hence conclusions from Helsinki should be drawn with caution. Physical activity and experiencing nature were the most common values attached to cemeteries in Copenhagen, whereas social interaction, spirituality and tranquillity were most common for Helsinki cemeteries. The results also revealed that younger Danes were particularly inclined to use cemeteries for social interactions, physical activity and spirituality and tranquillity. In the discussion, we elaborate on spatial differences between the cases, such as the availability of other green spaces, the size of cemeteries or people living in proximity to a cemetery, as well as on differences in policies and practices, including how Copenhagen stands out in actively promoting municipal cemeteries as recreational landscapes.  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