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   177篇
  免费   22篇
  国内免费   10篇
安全科学   61篇
废物处理   1篇
环保管理   23篇
综合类   44篇
基础理论   32篇
污染及防治   2篇
评价与监测   6篇
社会与环境   17篇
灾害及防治   23篇
  2023年   1篇
  2022年   7篇
  2021年   9篇
  2020年   12篇
  2019年   11篇
  2018年   6篇
  2017年   10篇
  2016年   8篇
  2015年   7篇
  2014年   3篇
  2013年   12篇
  2012年   8篇
  2011年   16篇
  2010年   16篇
  2009年   10篇
  2008年   8篇
  2007年   5篇
  2006年   11篇
  2005年   10篇
  2004年   11篇
  2003年   4篇
  2002年   3篇
  2001年   2篇
  2000年   4篇
  1999年   1篇
  1998年   1篇
  1997年   2篇
  1996年   2篇
  1995年   2篇
  1994年   3篇
  1993年   1篇
  1989年   1篇
  1983年   2篇
排序方式: 共有209条查询结果,搜索用时 31 毫秒
51.
濮阳旅游资源评价与可持续开发思路   总被引:4,自引:0,他引:4  
濮阳旅游资源以醇厚的历史文化资源为主 ,具有潜在性和开发难度大的特点。资源现状开发初具规模 ,但缺乏系统性和独特性 ,可持续的开发思路是历史文化资源的保护性开发 ,文化生态旅游式开发 ,多层次立体开发和区域联合式开发  相似文献   
52.
2005年陕西秋淋特征分析   总被引:3,自引:0,他引:3  
通过对2005年陕西秋淋特征分析认为,2005年陕西秋淋明显且偏晚,降水强度大,落区广且地区较集中;秋淋造成渭河下游、汉江干流分别出现了1981年、1983年以来最大的洪峰.西太平洋副热带高压强盛稳定及适当的副高脊线位置和西伸脊点位置是秋淋期间强降水集中的主要原因,而2005年的台风活动也为陕西秋淋天气提供了有利的气候背景.  相似文献   
53.
ABSTRACT: We compared watershed land‐use and fish community data between the 1970s and 1990s in 47 small streams in southeastern Wisconsin. Our goal was to quantify effects of increasing urbanization on stream fishes in what had been a predominantly agricultural region. In the 43 test watersheds, mean surface coverage by agricultural lands decreased from 54 percent to 43 percent and urban lands increased from 24 percent to 31 percent between 1970 and 1990. Agriculture dominated the four reference watersheds, but neither agriculture (65–59 percent) nor urban (4.4–4.8 percent) land‐uses changed significantly in those watersheds during the study period. From the 1970s to the 1990s the mean number of fish species for the test stream sites decreased 15 percent, fish density decreased 41 percent, and the index of biotic integrity (IBI) score dropped 32 percent. Fish community attributes at the four reference sites did not change significantly during the same period, although density was substantially lower in the 1990s. For both the 1970s and 1990s test sites, numbers of fish species and IBI scores were positively correlated with watershed percent agricultural land coverage and negatively correlated with watershed urban land uses, as indexed by percent effective connected imperviousness. Numbers of fish species per site and IBI scores were highly variable below 10 percent imperviousness, but consistently low above 10 percent. Sites that had less than 10 percent imperviousness and fewer than 10 fish species in the 1970s suffered the greatest relative increase in imperviousness and decline in species number over the study period. Our findings are consistent with previous studies that have found strong negative effects of urban land uses on stream ecosystems and a threshold of environmental damage at about 10 percent imperviousness. We conclude that although agricultural land uses often degrade stream fish communities, agricultural land impacts are generally less severe than those from urbanization on a per‐unit‐area basis.  相似文献   
54.
Desert fishes are some of the most imperiled vertebrates worldwide due to their low economic worth and because they compete with humans for water. An ecological complex of fishes, 2 suckers (Catostomus latipinnis, Catostomus discobolus) and a chub (Gila robusta) (collectively managed as the so‐called three species) are endemic to the U.S. Colorado River Basin, are affected by multiple stressors, and have allegedly declined dramatically. We built a series of occupancy models to determine relationships between trends in occupancy, local extinction, and local colonization rates, identify potential limiting factors, and evaluate the suitability of managing the 3 species collectively. For a historical period (1889–2011), top performing models (AICc) included a positive time trend in local extinction probability and a negative trend in local colonization probability. As flood frequency decreased post‐development local extinction probability increased. By the end of the time series, 47% (95% CI 34‐61) and 15% (95% CI 6‐33) of sites remained occupied by the suckers and the chub, respectively, and models with the 2 species of sucker as one group and the chub as the other performed best. For a contemporary period (2001?2011), top performing (based on AICc) models included peak annual discharge. As peak discharge increased, local extinction probability decreased and local colonization probability increased. For the contemporary period, results of models that split all 3 species into separate groups were similar to results of models that combined the 2 suckers but not the chub. Collectively, these results confirmed that declines in these fishes were strongly associated with water development and that relative to their historic distribution all 3 species have declined dramatically. Further, the chub was distinct in that it declined the most dramatically and therefore may need to be managed separately. Our modeling approach may be useful in other situations in which targeted data are sparse and conservation status and best management approach for multiple species are uncertain.  相似文献   
55.
历史时期黄河流域城市空间格局演变与影响因素   总被引:1,自引:0,他引:1  
研究历史时期黄河流域城市的空间格局演变,能够更好地理解人居环境的特点和发展脉络,对当今黄河流域生态保护、城镇发展有重要的现实价值。采用哈佛大学CHGIS数据库中城市时间序列数据,以及历史人口数据、流域和高程数据,通过实证分析,梳理黄河流域城市时空格局演变过程与影响因素。研究发现:(1)城市数量变化可划分为五个阶段。(2)一级延续稳定区,以今安阳为中心的河南北部城市高密集区和以今西安为中心的关中城市高密集区;以今济南、太原、洛阳为中心的次高密集区。二级延续稳定区分为五条重要的城市带,即渭河城市带、汾河城市带、鲁中山地北麓城市带、太行山东麓城市带及运河城市带。(3)城市重心迁移的平均距离为32 km,人口重心迁移的平均距离为95.78 km,城市和人口的分布有着较密切的联系。(4)气温、降水、高程、与河流的距离、黄河下游河道的变迁等自然因素,以及战争、都城转移和人工运河等人文因素共同影响了历史时期黄河流域城市的时空格局。  相似文献   
56.
考古文献是历史地理研究中一个重要的数据来源,在互联网时代对纸质文本进行数字化并根据考古遗址的时空特点建立信息系统,具有重要的意义.针对考古遗址的空间位置不明确,考古遗址信息系统注重空间特性但缺乏对原始文献的重视,基于WebGIS、关系型数据库技术以及MVC系统架构,设计并实现了南京考古遗址信息系统.从考古文献中提取考古遗址各种属性信息,构建考古遗址时空数据库,基于WebGIS信息系统发布南京考古遗址,实现考古遗址的时空可视化以及各个遗址点相关文献的原文阅读.提出了一种将考古遗址信息从单一的文本展示到融合时空信息的多维信息展示的技术流程,并为研究南京的历史地理学者提供了便捷的考古遗址资料共享平台.  相似文献   
57.
危险源理论研究及在事故预防中的应用   总被引:2,自引:2,他引:0  
为提高事故预防和控制水平,以现代安全科学的观点及事故致因理论为基础,运用事故案例分析研究方法,从危险源概念辨析入手,认为,危险源是指一切可能导致事故发生的能量、能量载体或危险物质,而不具有能量的隐患不是危险源。进一步探讨危险源的分类、层次结构及基于危险源理论的事故预防控制模型;同时,分析各类危险源在事故预防控制模型中的地位,指出事故的原因及防范对策。结果表明,事故是由直接危险源、第一触发危险源和初始触发危险源等不同种类的危险源的相互作用的结果,加强对不同危险源的研究,采取有针对性措施可有效提高生产安全管理水平及事故控制水平。  相似文献   
58.
利用福建省近岸海域1959—2018年的赤潮历史记录数据资料,在地理信息系统(Geographical Information System,GIS)平台下采用核密度估计函数(kernel density estimation)对赤潮历史记录数据中的赤潮发生频次、赤潮发生持续时间、赤潮面积和赤潮藻类毒性等参数进行了空间...  相似文献   
59.
In this paper, a comprehensive review of the concepts of occupational injury and accident causation and prevention is presented. Starting with hazard identification, the issues on risk assessment, accident causation, and intervention strategies are discussed progressively. The distinctiveness and overlaps in accident and injury research are highlighted. Both empirical research in terms of hypotheses tested and theoretical research such as accident causation models are compared and contrasted. Finally, based on the critical appraisal of the comprehensive review, future research directions on occupational injury research are delineated.  相似文献   
60.
为建立新的事故模型,首先以马克思主义的唯物辩证法为指导,针对事故内因、外因确定5对连锁因果关系,引入生产、事故、物质、能量、作业场所、安全管理、企业、政府和社会等安全要素,与故障树分析方法密切结合,建立缺陷塔模型(FTM)。然后,借鉴计算机科学面向对象编程的理念,定义塔体、塔段、塔壁、缺陷缝、管道、阀门共6种对象,规定了对象的主要属性,实现模型的三维可视化。  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