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   1370篇
  免费   106篇
  国内免费   218篇
安全科学   154篇
废物处理   17篇
环保管理   245篇
综合类   774篇
基础理论   152篇
污染及防治   86篇
评价与监测   77篇
社会与环境   128篇
灾害及防治   61篇
  2024年   4篇
  2023年   20篇
  2022年   35篇
  2021年   39篇
  2020年   36篇
  2019年   35篇
  2018年   34篇
  2017年   52篇
  2016年   59篇
  2015年   64篇
  2014年   55篇
  2013年   79篇
  2012年   102篇
  2011年   112篇
  2010年   78篇
  2009年   83篇
  2008年   76篇
  2007年   83篇
  2006年   87篇
  2005年   73篇
  2004年   64篇
  2003年   68篇
  2002年   44篇
  2001年   34篇
  2000年   44篇
  1999年   32篇
  1998年   25篇
  1997年   35篇
  1996年   20篇
  1995年   18篇
  1994年   13篇
  1993年   14篇
  1992年   16篇
  1991年   11篇
  1990年   11篇
  1989年   7篇
  1988年   6篇
  1987年   3篇
  1986年   4篇
  1985年   3篇
  1984年   3篇
  1982年   2篇
  1981年   2篇
  1980年   1篇
  1979年   2篇
  1977年   4篇
  1975年   1篇
  1973年   1篇
排序方式: 共有1694条查询结果,搜索用时 125 毫秒
401.
大型水利水电工程扰动区植被的生态恢复   总被引:1,自引:0,他引:1  
大型水利水电工程具有防洪、发电、航运等综合效益,是开发治理江河的骨干工程.水利水电工程建设常对项目区自然生态环境带来影响,施工中所产生的岩质边坡、土质边坡、弃土和弃渣等扰动可能导致项目区的生态系统退化、生物多样性丧失、水土流失和地质灾害加剧.扰动区植被生态恢复关系到工程安全运行和其所在区域的可持续发展.以向家坝水电工程为例,研究了大型水利水电工程扰动区植被生态恢复的目标、原则及方法.按生产、生态和社会功能,向家坝水电工程扰动区可划分为工程核心区、服务区和过渡区等3个功能区来系统规划其生态恢复.结合各自的功能需求和干扰特征,各功能区可采取相应的生态恢复技术和配置适宜物种来构建植物群落,形成结构稳定、多样性丰富、具有复合功能的植被景观.还简要评价了向家坝水电工程植被恢复现状,提出一些完善其生态恢复的建议.  相似文献   
402.
采用2种生物法/人工湿地工艺(水解酸化/好氧/人工湿地工艺和水解酸化/人工湿地(进水区强化曝气)工艺)处理胜利油田某联合处理站经隔油、混凝处理的采油废水,并运用发光细菌技术研究采油废水在处理过程中的生态毒性削减规律.研究结果表明,在水解酸化段水力停留时间(HRT)为20 h,好氧段HRT为10 h,人工湿地HRT为2 d的工况下,水解酸化/好氧/人工湿地工艺与水解酸化/人工湿地(进水区强化曝气)工艺的出水水质均能满足COD≤80 mg/L、NH_4~+-N≤15 mg/L的处理要求.发光细菌法试验结果表明,经隔油、混凝处理后的采油废水属高毒性废水,再经水解酸化/人工湿地(进水区强化曝气)工艺处理后生态毒性大幅削减,出水生态毒性降至低毒.  相似文献   
403.
A group of 26 European ports was interviewed to understand their requirements for environmental information and to establish how widespread the use of Earth Observation (EO) data was amongst them. Aspects covered by the research included port profile characterisation, environmental management activities, environmental needs and current monitoring practices. The study reflected the diversity amongst European ports and their environmental performances. Most of the ports were publicly owned and located in estuaries and rivers. General cargo was the most popular commodity handled. Practically all the ports had an environmental policy in place and half of them had been accredited by an external body. The main environmental parameters that ports required to be monitored were marine related issues (currents, waves and tide), water quality, meteorological parameters, turbidity and sediment processes. The principal driver for monitoring was maintaining key port operations, followed by legislation, and local responsibilities. Ports in general collected their own data in situ and only one-third had used remotely sensed data (data from Earth Observation satellites or from airplane mounted sensors) for environmental purposes. Half of them used computer modelling. This study was conducted within the framework of the European funded port environmental information collector project (PEARL).  相似文献   
404.
This paper describes and applies EDEN-E, an operational method for the environmental evaluation of dairy farms based on the life cycle assessment (LCA) conceptual framework. EDEN-E requires a modest amount of data readily available on-farm, and thus can be used to assess a large number of farms at a reasonable cost. EDEN-E estimates farm resource use and pollutant emissions mostly at the farm scale, based on-farm-gate balances, amongst others. Resource use and emissions are interpreted in terms of potential impacts: eutrophication, acidification, climate change, terrestrial toxicity, non-renewable energy use and land occupation. The method distinguishes for each total impact a direct component (impacts on the farm site) and an indirect component (impacts associated with production and supply of inputs used). A group of 47 dairy farms (41 conventional and six organic) was evaluated. Expressed per 1000 kg of fat-and-protein-corrected milk, total land occupation was significantly larger for organic than for conventional farms, while total impacts for eutrophication, acidification, climate change, terrestrial toxicity, and non-renewable energy use were not significantly different for the two production modes. When expressed per ha of land occupied all total impacts were significantly larger for conventional than organic farms. This study largely confirms previously published findings concerning the effect of production mode on impacts of dairy farms. However, it strikingly reveals that, for the set of farms examined, the contribution of production mode to overall inter-farm variability of impacts was minor relative to inter-farm variability within each of the two production modes examined. The mapping of impact variability through EDEN-E opens promising perspectives to move towards sustainable farming systems by identifying the structural and management characteristics of the farms presenting the lowest impacts.  相似文献   
405.
The assessment of human-induced pressures on the coastal area is essential to target management plans effectively, and moreover is required by the EU Water Framework Directive. A simple and cost-effective assessment of human-induced pressures on the coastal zone is applied using two methodologies: a qualitative visual assessment which uses satellite images; and a quantitative assessment based on governmental census data. These methods are applied to defined areas (23 areas) of four Italian regions: Liguria, Tuscany, Latium and Sardinia. The results show a high agreement (83%) between these two methods, in which only four of the 23 areas are classified differently. These differences may mainly be ascribed to the qualitative or quantitative properties of the methods, and to the different geographical units adopted. These characteristics however provide complementary information, which suggests that the application of both proposed methods confirms reliability and allows fine-tuning of the assessment. The pressure assessment proposed is simple, time and cost-effective, and repeatable over time and space. It therefore can be applied in different contexts to respond to legislative requirements or to target management plans and remedial actions effectively.  相似文献   
406.
有风条件下室内火灾自然排烟模型试验研究   总被引:2,自引:2,他引:0  
采用缩尺度试验方法对有风条件下室内火灾自然排烟过程准稳态进行研究,分析不同补气口、排烟口位置和风向对排烟效果的影响。试验结果表明:将补气口设在迎风面,排烟口设在背风面或侧风面时将获得比没有环境风时更好的自然排烟效果;而在其他情况下,环境风将通过减小排烟口处内外压差以及对室内烟气层产生扰动来降低自然排烟效果。在设置建筑自然排烟系统时,应综合考虑火灾具体情况以及当地风速条件,选择对自然排烟有利的排烟口与补气口位置组合,以提高自然排烟的效果。  相似文献   
407.
北方沙尘暴对杭州大气环境的影响及应对措施   总被引:1,自引:0,他引:1  
简述了我国沙尘天气的形成与分级情况。分析了我国沙尘天气的发展趋势与原因及其对杭州大气环境的影响情况。指出我国沙尘天气的发展有越演越烈的趋势 ,对杭州大气环境的影响时间延长 ,频次增加 ,危害程度加重 ,范围扩大。对防治沙尘天气污染大气环境提出了应对措施。  相似文献   
408.
Simulating Nitrate Leaching Profiles in a Highly Permeable Vadose Zone   总被引:2,自引:0,他引:2  
An approach is developed to simulate leaching of a dissolved chemical constituent in the vadose zone of an aquifer. Specifically, nitrate loading at the water table for different water table depths, for a range of aquifer permeability values, and for different cases of heterogeneity of the aquifer, are considered. Models from the literature are first used to derive soil–water characteristic curves (water retention and hydraulic conductivity) from a grain size distribution curve for unsaturated conditions. Given infiltration from the surface, the initial conditions for the chemical concentration, and the water content profile, leaching of the chemical in the vadose zone is simulated as a function of both time and depth. The methodology is illustrated for a permeable aquifer. Simulations are undertaken using a finite element code for saturated and unsaturated flow. Different scenarios are simulated depending on the heterogeneity of the aquifer and the depth of the water table. Modeling results show that in the example case studied, nitrate concentration loading at the water table does not depend strongly on the position of the water table, but rather on the material properties of the aquifer. The contribution of this endeavor resides in the methodology which allows a prediction of nitrate leaching using only the grain size property of the aquifer. It allows practitioners to obtain a first assessment of leaching with limited data.  相似文献   
409.
An essential step in the development of products based on biotechnology is an assessment of their potential economic impacts and safety, including an evaluation of the potential impact of transgenic crops and practices related to their cultivation on the environment and human or animal health. The purpose of this paper is to provide an assessment method to evaluate the impact of biotechnologies that uses quantifiable parameters and allows a comparative analysis between conventional technology and technologies using GMOs. This paper introduces a method to perform an impact analysis associated with the commercial release and use of genetically modified plants, the Assessment System GMP Method. The assessment is performed through indicators that are arranged according to their dimension criterion likewise: environmental, economic, social, capability and institutional approach. To perform an accurate evaluation of the GMP specific indicators related to genetic modification are grouped in common fields: genetic insert features, GM plant features, gene flow, food/feed field, introduction of the GMP, unexpected occurrences and specific indicators. The novelty is the possibility to include specific parameters to the biotechnology under assessment. In this case by case analysis the factors of moderation and the indexes are parameterized to perform an available assessment.  相似文献   
410.
三峡库区消落带富营养化及其危害预测和防治   总被引:2,自引:0,他引:2  
三峡水库蓄水运行后将出现一个落差达30 m的永久消落带。消落带是水域生态系统与岸上陆地生态系统的交替控制地带,该地带具有生物的多样性、人类活动的频繁性和生态的脆弱性,随着人类活动的影响,已成为湖岸带中生态最脆弱的地带。由于工业和生活用水污染以及水体自净能力下降,消落区富营养化相关物质(如氮和磷)污染会进一步加剧。因此,必须针对库区消落带地区的特殊情况,选择适当的模式对消落带进行超前环境整治和保护,实现三峡库区生态系统的恢复和重建。  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