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   13315篇
  免费   100篇
  国内免费   1443篇
安全科学   211篇
废物处理   960篇
环保管理   1506篇
综合类   2790篇
基础理论   3754篇
环境理论   1篇
污染及防治   3320篇
评价与监测   1142篇
社会与环境   1013篇
灾害及防治   161篇
  2024年   2篇
  2023年   63篇
  2022年   184篇
  2021年   127篇
  2020年   95篇
  2019年   88篇
  2018年   1593篇
  2017年   1504篇
  2016年   1380篇
  2015年   370篇
  2014年   317篇
  2013年   371篇
  2012年   780篇
  2011年   1634篇
  2010年   911篇
  2009年   862篇
  2008年   1139篇
  2007年   1439篇
  2006年   210篇
  2005年   168篇
  2004年   146篇
  2003年   204篇
  2002年   225篇
  2001年   123篇
  2000年   130篇
  1999年   132篇
  1998年   151篇
  1997年   84篇
  1996年   77篇
  1995年   74篇
  1994年   59篇
  1993年   55篇
  1992年   48篇
  1991年   15篇
  1990年   19篇
  1989年   11篇
  1988年   12篇
  1987年   5篇
  1986年   6篇
  1985年   2篇
  1984年   13篇
  1983年   10篇
  1982年   2篇
  1981年   7篇
  1979年   2篇
  1977年   2篇
  1974年   1篇
  1972年   1篇
  1971年   2篇
  1935年   2篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
971.
Indentifying common priorities in shared natural resource systems constitutes an important platform for implementing adaptation and a major step in sharing a common responsibility in addressing climate change. Predominated by discourses on REDD + (Reduced Emissions from Deforestation and Forest Degradation and conservation, sustainable management of forests and enhancement of forest carbon stocks in developing countries) with little emphasis on adaptation there is a risk of lack of policy measures in addressing climate change in the Congo Basin. Forest products and ecosystem services provide security portfolios for the predominantly rural communities, and play major roles in national development programmes in both revenue and employment opportunities. Thus, raising the profile of forests in the policy arena especially in the twin roles of addressing climate change in mitigation and adaptation and achieving resilient development is crucial. Within the framework of the Congo Basin Forests and Climate Change Adaptation project (COFCCA) project, science policy dialogue was conducted to identify and prioritize forest based sectors vulnerable to climate change but important to household livelihoods and national development. The goal of the prioritization process was for the development of intervention in forest as measures for climate change adaptation in Central Africa. Participants constituted a wide range of stakeholders (government, Non Governmental Organizations, research institutions, universities, community leaders, private sectors etc.) as representatives from three countries directly involved in the project: Cameroon, Central African Republic and Democratic Republic of Congo. Building on national priorities, four forest related sectors were identified as common priorities at the regional level for focus on climate change adaptation. These sectors included: (1) energy with emphasis on fuel wood and Charcoal; (2) Water principally quality, quantity, accessibility, etc.; (3) Food with emphasis on Non Timber Forest Products, and (4) Health linked to healthcare products (medicinal plants). Using these prioritized sectors, the project focused on addressing the impacts of climate change on local communities and the development of adaptation strategies in the three pilot countries of the Congo Basin region. The four sectors constitute the key for development in the region and equally considered as priority sectors in the poverty reduction papers. Focused research on these sectors can help to inject the role of forests in national and local development and their potentials contributions to climate change adaptation in national and public discourses. Mainstreaming forest for climate change adaptation into national development planning is the key to improve policy coherence and effectiveness in forest management in the region.  相似文献   
972.
喀喇昆仑-昆仑山昆虫区系   总被引:3,自引:0,他引:3  
喀喇昆仑-昆仑山昆虫区系属于典型的古北区性质,古北种占53.93%,中亚成分占16.85%,北坡受中亚成分影响大,南坡占有多数的高山成分。这一地域昆虫区系的形成和演替与其地质历史密切相关。由于印度板块不断向北挤压,喀喇昆仑-昆仑山强烈抬升,随着塔里木盆地的形成,地域性的昆虫区系便产生了,并有其特有成分的分化:亚种级的分化,种级的分化甚至属级的分化  相似文献   
973.
利用底栖动物评价图们江污染的研究   总被引:16,自引:1,他引:16  
作者于1977年8月至1979年8月在图们江上中游的9个采样点上,主要使用人工基质采样器采集底栖无脊椎动物。结果证明图们江底栖动物比较丰富,出现的主要种类属于襀翅目、蜉蝣目的稚虫,毛翅目幼虫,摇蚊科幼虫和水栖寡毛类。其中崇善江段种类多,表现出明显的多样性。根据三年来所收集到的资料,计算了Trent生物指数,Chandler记分制以及Shannon多样性指数,并对图们江的污染状况作出生物学评价,上游地段属于清洁水到中污染;中游地段在污染源以下至图们站属于重污染;自河东站开始,水质又明显好转,属于轻污染。  相似文献   
974.
经模拟酸雨处理植物的试验表明,酸雨对植物叶片的直接损害是由于酸雨水滴滞留在叶面引起的。若在雨后2h内喷水(pH7.0±0.2)以驱除滞留在叶面的水滴,叶片则无受害症状,叶绿素含量、生物产量和经济产量所受的影响也将减轻甚至完全不受影响。  相似文献   
975.
A study has been made on elements organic constituents, TSP, SO2,NO2 of atmospheric pollutants in Beijing. 17 elements, and some PAHs, e. g. B(a)P, B(b, j, k)P, and B(g, h, i)P, in airborne particles by X-ray fluorescence spectroscopy and HPLC, GC/MS, have been determined respectively. It has been shown that the elements Pb, Zn, S and Cu were more enriched in fine particles and different valence states of sulfur at various sites. It was found that the concentrations of S6+ and S2-were more than 85% and less than 15% of the total sulfur respectively. Concentrations of major PAHs and sulfur-containing compounds increased in winter and in urban area. High values for Pb and Zn in city, Fe and Mn at industrial area and Cu, Al rural sites were obtained respectively. This implies the functions of different elemental sources of various sites. Thus, elements can be from distingushed anthropogenic and natural sources.The main contribution of SO2 was found of to have same seasonal variation as the anthropogenic el  相似文献   
976.
本文通过对呼和浩特市创建国家环保模范城市面临的困难、采取的措施以及取得的效果进行分析,对北方地区创建国家环保模范城市提供借鉴.  相似文献   
977.
WAHMO model was used to simulate the distribution of pollutants in Dalian Bay, China as to predict well as the growth and control of alga. The observed and predicted values of main pollutants showed a good trend at all study locations and the different between them can be ignored. Simulation results illustrated that phosphate was one of limited factors to control algal growth at the location near the sewage outfall, meanwhile, away from the sewage outfall, the synergy of ammonium nitrogen and phosphate was the limited factor.  相似文献   
978.
Estuaries have been described as one of the most difficult environments on Earth. It is difficult to know how to treat the combined wastewater in tidal rivers at the estuary, where the situation is very different from ordinary fresh water rivers. Waste oyster shell was used as the active filler in this study in a bio-contact oxidation tank to treat the combined wastewater at the Fengtang Tidal River. With a middle-experimental scale of 360 ma/day, the average removal efficiency of COD, BOD, NH3-N, TP and TSS was 80.05%, 85.02%, 86.59%, 50.58% and 85.32%, respectively, in this bio-contact oxidation process. The living microbes in the biofilms on the waste oyster shell in this bio-contact oxidation tank, which were mainly composed of zoogloea, protozoa and micro-metazoa species, revealed that waste oyster shell as the filler was suitable material for combined wastewater degradation. This treatment method using waste oyster shell as active filler was then applied in a mangrove demonstration area for water quality improvement near the experiment area, with a treatment volume of 5 × 10^3 m^3/day. Another project was also successfully applied in a constructed wetland, with a wastewater treatment volume of 1 ×10^3 m^3/day. This technology is therefore feasible and can easily be applied on a larger scale,  相似文献   
979.
文章通过对利水电站坝上、坝下布设监测断面,进行为期近一个月的枯水期水质监测,分析上下游水质的变化以期对梯级电站的建设与运营对北溪下游水质的影响进行研究,认为梯级电站的建设运行,形成梯级水库,流速变缓,大气覆氧能力降低,水中溶解氧下降,导致水体自净能力减弱,使水环境容量降低,对污染物的稀释、混合和降解能力减弱,湖库富营养化是水库的主要生态环境问题。为此,提出污染防治对策,并提出当上游污染水团下泄时,作为补救和改善水质时电站应采取的运行方式,为今后河流的突发污染防治、水质保护与改善提供经验借鉴。  相似文献   
980.
大多数传统的重金属污染治理技术成本高,会引起土壤肥力下降,对各类生态系统造成负面影响。植物修复技术是一种成本低、环境友好的方法,不会对土壤性质和生态系统产生不利影响。文章综述了植物修复治理重金属污染土壤的研究进展,探讨如何通过采取物理、化学、生物技术及农艺措施等方法提高修复植物的生物量和重金属积累量并展望了今后的研究方向。  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