全文获取类型
收费全文 | 36384篇 |
免费 | 2746篇 |
国内免费 | 5932篇 |
专业分类
安全科学 | 4559篇 |
废物处理 | 515篇 |
环保管理 | 7330篇 |
综合类 | 19596篇 |
基础理论 | 4068篇 |
环境理论 | 20篇 |
污染及防治 | 2266篇 |
评价与监测 | 2403篇 |
社会与环境 | 2824篇 |
灾害及防治 | 1481篇 |
出版年
2024年 | 122篇 |
2023年 | 470篇 |
2022年 | 790篇 |
2021年 | 1031篇 |
2020年 | 1093篇 |
2019年 | 920篇 |
2018年 | 806篇 |
2017年 | 1231篇 |
2016年 | 1471篇 |
2015年 | 1557篇 |
2014年 | 1624篇 |
2013年 | 2244篇 |
2012年 | 2589篇 |
2011年 | 2804篇 |
2010年 | 2046篇 |
2009年 | 2022篇 |
2008年 | 1596篇 |
2007年 | 2492篇 |
2006年 | 2476篇 |
2005年 | 1953篇 |
2004年 | 1670篇 |
2003年 | 1746篇 |
2002年 | 1462篇 |
2001年 | 1194篇 |
2000年 | 1168篇 |
1999年 | 1040篇 |
1998年 | 753篇 |
1997年 | 671篇 |
1996年 | 564篇 |
1995年 | 540篇 |
1994年 | 460篇 |
1993年 | 423篇 |
1992年 | 308篇 |
1991年 | 240篇 |
1990年 | 175篇 |
1989年 | 137篇 |
1988年 | 117篇 |
1987年 | 90篇 |
1986年 | 61篇 |
1985年 | 63篇 |
1984年 | 64篇 |
1983年 | 75篇 |
1982年 | 68篇 |
1981年 | 84篇 |
1980年 | 87篇 |
1979年 | 82篇 |
1978年 | 53篇 |
1977年 | 54篇 |
1973年 | 49篇 |
1971年 | 64篇 |
排序方式: 共有10000条查询结果,搜索用时 515 毫秒
1.
Progress and challenges in consolidating the management of Amazonian protected areas and indigenous territories
下载免费PDF全文
![点击此处可从《Conservation biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Effective management refers to the ability of a protected area or indigenous territory to meet its objectives, particularly as they relate to the protection of biodiversity and forest cover. Effective management is achieved through a process of consolidation, which among other things requires legally protecting sites, integrating sites into land‐use planning, developing and implementing management and resource‐use plans, and securing long‐term funding to pay for recurrent costs. Effectively managing all protected areas and indigenous territories in the Amazon may be needed to avoid a deforestation tipping point beyond which regional climatic feedbacks and global climate change interact to catalyze irreversible drying and savannization of large areas. At present, protected areas and indigenous territories cover 45.5% (3.55 million km2) of the Amazon, most of the 60–70% forest cover required to maintain hydrologic and climatic function. Three independent evaluations of a long‐term large‐scale philanthropic initiative in the Amazon yielded insights into the challenges and advances toward achieving effective management of protected areas and indigenous territories. Over the life of the initiative, management of sites has improved considerably, particularly with respect to management planning and capacity building, but few sites are effectively managed and many lack sufficient long‐term financing, adequate governance, support of nongovernmental organizations, and the means to withstand economic pressures. The time and money required to complete consolidation is still poorly understood, but it is clear that philanthropic funding is critical so long as essential funding needs are not met by governments and other sources, which could be on the order of decades. Despite challenges, it is encouraging that legal protection has expanded greatly and management of sites is improving steadily. Management of protected areas in other developing countries could be informed by improvements that have occurred in Amazonian countries. 相似文献
2.
简要叙述了电捕焦油器开工以来存在的问题,对电捕捕焦油器不能安全稳定运行的原因进行了分析,并采取改进措施。实践证明,改进工艺技术合理,方法可行,电捕焦油器运行效果达到指标要求。 相似文献
3.
4.
Performance evaluation of Health, Safety and Environment (HSE) is the measurement of a company's achievement in HSE management. In order to receive a comprehensive and objective evaluation result, it is necessary to consider all evaluation factors and experts at different levels when HSE performance assessment is conducted. To improve conventional HSE performance evaluation, where weighted average method was used, a Fuzzy Comprehensive Evaluation (FCE) method is used in this study by taking experts' weights into account. Further, an HSE operating performance assessment system is designed to simplify manual and complex assessment process and generate charts and analysis reports automatically. Finally, a case of petrochemical enterprise is used to illustrate the effectiveness of the method and system. 相似文献
5.
Bodhipaksha Krishna Geethani Thilakarathne Stephen Schensul Sujithra K. Weeragoda Rohan Weerasooriya Ng Wun Jern 《环境质量管理》2023,32(4):371-378
Fifty percent of the dry zone areas in Sri Lanka have fluoride levels above 1 ppm. This paper discusses the ground conditions and recommends an appropriate range of fluoride in drinking water which can support preventive practices for improving the oral health of children 8-years old and younger. In efforts to address the Chronic Kidney Disease of Unknown etiology (CKDU), water treatment to reduce contaminant level in potable water has been implemented. Such treatment would also remove fluoride and has resulted in potable water with various fluoride levels, depending on concentrations in the raw water. While it is important to reduce fluoride levels, it is important to have appropriate residual levels for prevention of dental caries. It needs, however, to be noted fluoride in excess can cause dental fluorosis. In Sri Lanka's dry zone areas increasing prevalence of dental fluorosis with decreasing prevalence of dental caries has been noted. Consumption of tea and powdered milk could increase total intake of fluoride. Fluoridated toothpaste, when used properly, may, however, result in negligible intake of fluoride. Sri Lanka's hot tropical climate which results in substantial intake of fluids reinforces the need to consider reduction in water fluoride. Consideration of local studies and international standards indicate fluoride levels should be in the range of 0.225–0.500 ppm. In the range of 0.225–0.500 ppm, the prevalence of dental fluorosis and caries was only 14% and 8%, respectively, in an endemic district. When fluoride levels are above 0.500 ppm, the issue of dental fluorosis shall need to be addressed. When levels are below 0.225 ppm, oral health care services shall need to be directed at preventing dental caries. 相似文献
6.
Waste accumulation is a grave concern and becoming a transboundary challenge for environment. During Covid-19 pandemic, diverse type of waste were collected due to different practices employed in order to fight back the transmission rate of the virus. Covid-19 was proved to be capricious catastrophe of this 20th century and even not completely eradicated from the world. The havoc created by this imperceptible quick witted, pleomorphic deadly virus can't be ignored. Though a number of vaccines have been developed by the scientists but there is a fear of getting this virus again in our life. Medical studies prove that immunity drinks will help to reduce its reoccurrences. Coconut water is widely used among all drinks available globally. Its massive consumption created an incalculable pile of green coconut shells around the different corners of the world. This practice generating enormous problem of space acquisition for the environment. Both the environment and public health will benefit from an evaluation of quantity of coconut waste that is being thrown and its potential to generate value added products. With this context, present article has been planned to study different aspects like, coconut waste generation, its biological properties and environmental hazards associated with its accumulation. Additionally, this review illustrates, green technologies for production of different value added products from coconut waste. 相似文献
7.
Amirhossein Moosavi Adel Nikfarjam 《International Journal of Sustainable Engineering》2019,12(3):174-188
In this paper, the inventory-routing problem is studied for a closed-loop supply chain. This closed-loop supply chain considers suppliers, manufacturers, whole-sellers, and disposal centers. To formulate this problem, a mixed integer linear programming model is proposed. This mathematical model minimizes the total costs of the supply chain, including the fixed and variable costs of vehicles, and holding inventory costs of final products and scraps. The proposed model considers the road roughness degree, multi-path setting and the heterogeneous fleet of vehicles, which increases its flexibility and the quality of solutions. Then, two symmetry-breaking constraints are proposed to reduce the complexity of the mathematical model. In order to evaluate the integrity of the proposed model, 20 instances of different sizes are randomly generated and solved. Finally, a comprehensive sensitivity analysis is conducted with respect to five key features of the problem, such as the impact of the symmetry-breaking constraints on the CPU time, multi-path setting, fixed cost of vehicles, heterogeneous fleet of vehicles, and lost sales. The results indicate that the consideration of multi-path setting and the heterogeneous fleet of vehicles improves the quality of solutions significantly. 相似文献
8.
Quantitative methods have been applied to the study of floristic structure and diversity in Samarskaya Luka. The results show that Samarskaya Luka is a floristically heterogeneous area in which six elementary floras can be distinguished. This area has been assessed as a floristically autonomous formation, and its floristic representativeness was estimated. 相似文献
9.
基于复杂系统建模的水管理政策研究进展 总被引:3,自引:0,他引:3
基于Agent的建模方法(ABSS)通过自下而上的方式,考察系统中主体的不同状态和行为特征、主体与环境的作用、主体之间的作用,来表征系统的宏观特征,是进行复杂社会环境系统分析和政策研究的重要手段,在水资源、水环境管理系统中得到了有效的应用。本文在大量文献调研的基础上,讨论了ABSS建模方法的基本原理、主要特征、系统构成、分类方法和开发工具等特征,总结了其供水系统发展、水资源分配和流域水资源管理、农业土地和水资源利用、居民用水行为、农业污染控制及人类活动的水环境影响等方面的应用,分析了其在研究内容、研究方法、研究结果等方面的发展趋势,讨论了利用该方法研究我国水资源管理和水污染控制政策的必要性和重要性。 相似文献
10.