全文获取类型
收费全文 | 2871篇 |
免费 | 234篇 |
国内免费 | 306篇 |
专业分类
安全科学 | 259篇 |
废物处理 | 21篇 |
环保管理 | 469篇 |
综合类 | 1308篇 |
基础理论 | 608篇 |
环境理论 | 2篇 |
污染及防治 | 150篇 |
评价与监测 | 115篇 |
社会与环境 | 371篇 |
灾害及防治 | 108篇 |
出版年
2024年 | 2篇 |
2023年 | 30篇 |
2022年 | 70篇 |
2021年 | 76篇 |
2020年 | 87篇 |
2019年 | 79篇 |
2018年 | 78篇 |
2017年 | 114篇 |
2016年 | 137篇 |
2015年 | 108篇 |
2014年 | 125篇 |
2013年 | 192篇 |
2012年 | 151篇 |
2011年 | 232篇 |
2010年 | 175篇 |
2009年 | 153篇 |
2008年 | 129篇 |
2007年 | 201篇 |
2006年 | 212篇 |
2005年 | 157篇 |
2004年 | 143篇 |
2003年 | 128篇 |
2002年 | 96篇 |
2001年 | 75篇 |
2000年 | 70篇 |
1999年 | 56篇 |
1998年 | 51篇 |
1997年 | 48篇 |
1996年 | 45篇 |
1995年 | 30篇 |
1994年 | 25篇 |
1993年 | 31篇 |
1992年 | 17篇 |
1991年 | 10篇 |
1990年 | 13篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 10篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有3411条查询结果,搜索用时 15 毫秒
1.
利用1985、2000、2013年遥感影像提取的土地覆盖数据,通过景观格局指数、动态度计算、转移矩阵等,分析1985—2013年我国典型地区各类型生态系统景观格局及其动态变化特征、生态系统相互转化时空变化特征等,揭示1985—2013年生态环境格局变化的特点和规律:一级分类生态系统综合变化率,赣江、闽江、白龙江和岷江上游流域分别为4.7%、3.9%、3.3%和1.7%,生态系统变化强度1985—2000年较缓,2000—2013年更剧烈。1985—2013年典型区生态系统的主要转化方向具有持续性和双向性特征,岷江、白龙江和赣江上游流域退耕还林还草政策效果明显,出现较高比例的耕地转为森林和草地;面积占67.4%生态系统类型变化与耕地生态系统和人工表面生态系统变化有关;生态系统变化具有明显的区域差异,生态变化主要表现为沿主要河流谷地的线状延伸,主要城镇居民点附近生态系统类型变化较为突出,人类活动是典型地区生态系统类型格局变化的主要驱动力;典型区尤其是敏感区应加大退耕还林还草政策,减少人类经济活动,降低洪水泥石流灾害发生的概率和程度。 相似文献
2.
Lucas Ferrante Augusto Getirana Fabricio Beggiato Baccaro Jochen Schöngart Ana Cristina Monteiro Leonel Renato Gaiga Michel Varajão Garey Philip Martin Fearnside 《Conservation biology》2023,37(3):e14033
Given the speed at which humans are changing the climate, species with high degrees of endemism may not have time to avoid extinction through adaptation. We investigated through teleconnection analysis the origin of rainfall that determines the phylogenetic diversity of rainforest frogs and the effects of microclimate differences in shaping the morphological traits of isolated populations (which contribute to greater phylogenetic diversity and speciation). We also investigated through teleconnection analysis how deforestation in Amazonia can affect ecosystem services that are fundamental to maintaining the climate of the Atlantic rainforest biodiversity hotspot. Seasonal winds known as flying rivers carry water vapor from Amazonia to the Atlantic Forest, and the breaking of this ecosystem service could lead Atlantic Forest species to population decline and extinction in the short term. Our results suggest that the selection of morphological traits that shape Atlantic Forest frog diversity and their population dynamics are influenced by the Amazonian flying rivers. Our results also suggest that the increases of temperature anomalies in the Atlantic Ocean due to global warming and in the Amazon forest due to deforestation are already breaking this cycle and threaten the biodiversity of the Atlantic Forest hotspot. 相似文献
3.
目前国内关于海洋修复工程的考核研究多为修复工程的生态效果考核,极少包含成本效益考核,以致无法比较和分析不同类型、不同规模的海洋修复工程的生态绩效,不利于海洋修复工程的考核和验收管理。根据当前自然资源部实施“蓝色海湾”等整治修复工程的检查验收管理的新需求,本文构建了基于海洋生态系统健康恢复、生态系统服务价值增长和单位成本生态效益等理论的海洋修复工程生态绩效考核指标体系。此外,本文以温州海域2014—2016年海洋修复的生态绩效的考核为例,结合考核结果以及直接相关性、独立性、可测量性和业务化等指标选取原则,对指标体系进行了改进。结果表明本指标体系可以在海洋修复工程的检查验收中被用于生态绩效考核,管理部门可根据海洋修复工程的类型和管理需求,有选择性地采纳部分或全部指标进行考核。 相似文献
4.
地表水环境遥感监测关键技术与系统 总被引:1,自引:0,他引:1
介绍了地表水环境遥感监测的关键技术与系统及其典型应用,其代表性机理模型和应用示范成果主要来自于中国科学院遥感与数字地球研究所的高光谱遥感团队在最近几年中取得的一些研究进展,主要包括建立了基于改进双峰法的水体分布自动化遥感提取方法,实现了简单、高效和高精度的水体提取;提出了大型湖泊长时序水量估算方法,并以青藏高原湖区为例,重建了典型湖泊面积、水位和水量序列;发展了基于“软分类”的典型内陆水体叶绿素a浓度反演方法,构建了基于生物光学模型的高度浑浊水体悬浮物浓度遥感反演半解析方法,提高了反演方法的区域和季节适用性;构建了基于水色指数的大范围湖库营养状态和透明度遥感监测方法,实现了全球大型湖库营养状态遥感监测,以及全国大型湖库透明度遥感监测;在此基础上,开发了地表水环境遥感监测系统,提高了水环境遥感监测效率,促进了卫星遥感在水环境监测中的高精度业务化应用。 相似文献
5.
Phoebe J. Stewart-Sinclair Carissa J. Klein Ian J. Bateman Catherine E. Lovelock 《Conservation biology》2021,35(6):1850-1860
Marine coastal ecosystems, commonly referred to as blue ecosystems, provide valuable services to society but are under increasing threat worldwide due to a variety of drivers, including eutrophication, development, land-use change, land reclamation, and climate change. Ecological restoration is sometimes necessary to facilitate recovery in coastal ecosystems. Blue restoration (i.e., in marine coastal systems) is a developing field, and projects to date have been small scale and expensive, leading to the perception that restoration may not be economically viable. We conducted a global cost–benefit analysis to determine the net benefits of restoring coral reef, mangrove, saltmarsh, and seagrass ecosystems, where the benefit is defined as the monetary value of ecosystem services. We estimated costs from published restoration case studies and used an adjusted-value-transfer method to assign benefit values to these case studies. Benefit values were estimated as the monetary value provided by ecosystem services of the restored habitats. Benefits outweighed costs (i.e., there were positive net benefits) for restoration of all blue ecosystems. Mean benefit:cost ratios for ecosystem restoration were eight to 10 times higher than prior studies of coral reef and seagrass restoration, most likely due to the more recent lower cost estimates we used. Among ecosystems, saltmarsh had the greatest net benefits followed by mangrove; coral reef and seagrass ecosystems had lower net benefits. In general, restoration in nations with middle incomes had higher (eight times higher in coral reefs and 40 times higher in mangroves) net benefits than those with high incomes. Within an ecosystem type, net benefit varied with restoration technique (coral reef and saltmarsh), ecosystem service produced (mangrove and saltmarsh), and project duration (seagrass). These results challenge the perceptions of the low economic viability of blue restoration and should encourage further targeted investment in this field. 相似文献
6.
While factors influencing perceptions of drinking water have been well studied, those of aquatic ecosystems have been to lesser extent. We conducted a review to improve awareness of these factors. Environmental factors found to influence public perceptions of aquatic ecosystems were presence/absence of water plants and algae, presence/absence of floating debris, the odor, movement (for flowing waters) and clarity/turbidity of the water, and the type, condition, setting, naturalness, and overall aesthetic appeal of the ecosystem. Sociocultural factors found to influence public perceptions of aquatic ecosystems included age, education, gender, and place-based knowledge. We provide perspectives of how managers can better meet the diverse social demands placed on aquatic ecosystems. The importance and benefits of considering these perspectives may be especially beneficial where significant multi-generational and culturally relevant place-based knowledge exist. 相似文献
7.
Background: Inconsistent use of seat belts in an ambulance may increase the risk of injury for emergency medical services (EMS) professionals and their patients. Our objectives were to: (1) describe the prevalence of seat belt usage based on patient acuity and seat location, and (2) assess the association between EMS-related characteristics and consistent use of a seat belt. Methods: We administered a cross-sectional electronic questionnaire to a random sample of 20,000 nationally-certified EMS professionals, measuring seat belt use in each seating location of an ambulance during transport of stable, critical, or no patients. We included practicing, non-military, emergency medical technicians or higher who reported working in ambulances. We used multivariable logistic regression models to estimate the odds of consistent (≥50% of the time) use of seat belts for the rear-facing jump seat and right-sided crew bench during transport of stable and critical patients. Results: A total of 1431 respondents were included in the analysis. Patient compartment seat belt use varied with the highest use in forward-facing seats when no patient was being transported (59.8%) and lowest use in the left-side “CPR” seat with a critical patient (9.4%). Only 40.2% of respondents reported an agency policy regarding seat belt use while riding in the patient compartment. In all multivariable logistic regression models, advanced life support level certification and fewer years of experience were associated with decreased odds of consistent seat belt use. An agency seat belt policy was strongly associated with increased odds of seat belt use in the patient compartment. Conclusions: Seat belt use was low and varied by seating location and patient acuity in the patient compartment of an ambulance. Practical Applications: EMS organizations should consider primary prevention approaches of provider education, improved ambulance designs, enactment and enforcement of policies to improve seat belt compliance and provider safety. 相似文献
8.
ABSTRACTThe Longmen Shan fault area in southwest China is one of the world’s most active earthquake zones. The epicenters of the two most recent earthquakes, the 2008 Wenchuan earthquake (8.0?Ms) and the 2013 Lushan earthquake (7.0?Ms), both of which caused serious losses, were only 85?km apart. Community-based disaster risk reduction is the foundation of the disaster management system pyramid and is critical to the success of ‘sustainable hazard mitigation’. Based on multiple collaborative stakeholder perspectives, this paper examines public participation in an NGO-oriented Community for Disaster Prevention and Mitigation (N-CDPM) in the period between the two earthquakes as a multi-stage problem; N-CDPM establishment, normal operations, disaster testing, and continuous improvement. Multi-stage field research was conducted in the affected areas in the Longmen Shan fault area to examine the collaboration in each stage, after which the differences were compared across the four stages based on eight key indices; scales, core stakeholders, core network stability, mean number of lines, mean collaborative level, governments, and individual and public organization participation. The government participation, individual participation, and public organization participation are then discussed. This paper provides a novel research approach to CDPM in multiple earthquake regions and gives rich insights into the collaboration between the government and the public for N-CDPM. 相似文献
9.
松花江流域水生态环境质量评价研究 总被引:5,自引:2,他引:3
采用生物完整性指数(IBI)法评价松花江流域的水生态环境质量。对25个候选生物参数进行敏感度分析、Pearson相关性分析,最终筛选出由总分类单元数、EPT分类单元数、EPT密度、敏感种分类单元比例、敏感物种数量、Hilsenhoff生物指数(HBI)6个核心参数构成的IBI评价指标。采用95%分位数法建立了IBI评价标准,将IBI评价结果划分为5个等级:大于35.84为优,26.88~35.84为良好,17.92~26.88为一般,8.96~17.92为较差,小于8.96为很差。结果表明,建立的IBI评价方法适用于松花江流域水生态环境质量评价,松花江流域各位点30.0%生物状况为优和良好,23.3%为一般;46.7%为较差和很差,说明流域内近一半区域的水生态质量存在不同程度的受损。流域生境质量主要处于一般-良好的状态;水质处于轻度污染。 相似文献
10.
基于生态系统服务供需的雄安新区生态安全格局构建 总被引:2,自引:0,他引:2
生态安全格局构建是保障区域生态安全的关键。沿用“源地识别—阻力面构建—廊道提取”的生态安全格局构建模式,选取粮食供给、产水量、土壤保持、固碳释氧和生境维持5项生态系统服务供给指标,以及人口密度、地均GDP和土地利用程度3项生态系统服务需求指标,综合生态系统服务供需2方面识别重要生态源地,利用夜间灯光强度进行基本阻力面修正,采用最小累积阻力模型进行生态廊道提取,构建出雄安新区生态安全格局。研究表明:新区生态源地总面积约48433 km2,占新区土地总面积的313%,主要分布于新区西北部旱地和东南部水域;新区生态阻力系数空间分布较为破碎,大部分区域阻力值较低,间或分布高阻力值;新区生态廊道总长度18586 km,呈“Y”字型沿建设用地和水系分布,所处地类主要为旱地。基于生态系统服务供需的生态安全格局构建可为新区规划建设提供参考和借鉴。 相似文献