全文获取类型
收费全文 | 320篇 |
免费 | 9篇 |
国内免费 | 34篇 |
专业分类
安全科学 | 4篇 |
环保管理 | 141篇 |
综合类 | 143篇 |
基础理论 | 35篇 |
污染及防治 | 20篇 |
评价与监测 | 9篇 |
社会与环境 | 10篇 |
灾害及防治 | 1篇 |
出版年
2023年 | 4篇 |
2021年 | 6篇 |
2020年 | 6篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 9篇 |
2016年 | 8篇 |
2015年 | 10篇 |
2014年 | 12篇 |
2013年 | 12篇 |
2012年 | 22篇 |
2011年 | 28篇 |
2010年 | 20篇 |
2009年 | 20篇 |
2008年 | 20篇 |
2007年 | 15篇 |
2006年 | 11篇 |
2005年 | 9篇 |
2004年 | 19篇 |
2003年 | 19篇 |
2002年 | 13篇 |
2001年 | 11篇 |
2000年 | 8篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 6篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有363条查询结果,搜索用时 547 毫秒
51.
Ping ZHONG Zhifeng YANG Baoshan CUI Jingling LIU 《Frontiers of Environmental Science & Engineering in China》2008,2(1):73-80
In recent years, the hydrological characters of Baiyangdian Wetland have changed greatly, which, in turn, influence the biotic
component, the structure and function of the wetland ecosystem. In order to determine the demands for water resources of ecological
wetland system, a method of ecological water level coefficient was suggested to calculate the water resources demands for
wetland environment use. This research showed that the minimum coefficient is 0.94 and the optimal coefficient is more than
1.10. According to these two coefficients, the ecological water level and water quantity can be estimated. The results indicate
that the amount of the minimal and optimal eco-environmental water requirements are 0.87 × 108 and 2.78 × 108 m3 in average monthly, respectively, with the maximum eco-environmental water requirement in summer and the minimum in winter.
The annual change of eco-environment water demand is in according with the climate change and hydrological characters. The
method of ecological water level emphasizes that wetland ecosystem adapts to the hydrological conditions, so it can be used
in practice well.
__________
Translated from Acta Scientiae Circumstantiae, 2005, 25(8): 1,119–1,126 [译自: 环境科学学报] 相似文献
52.
Optimizing model for land use/land cover retrieval from remote sensing imagery based on variable precision rough sets 总被引:2,自引:0,他引:2
The suitable spectral mode in remote sensing is often desirable to facilitate the inversion of ecological environment and landscape. This paper put forward an optimizing model based on variable precision rough sets (VPRS) for the land cover discrimination in wetland inventory. In the case study of Lake Baiyangdian which has important ecological functions to the northern China, this model is established successfully according to the domain-experts knowledge. The procedure is as follows. First step is data collection, including remote-sensing data (e.g., Landsat-5 TM bands), the digitized relief maps, and statistical yearbooks. Second, the remote sensing imagery (RSI) and relief maps are co-registered into the same resolution. Third, a condition set, including various attributes is derived from spectral bands, band math or ratio indices based on previous studies, at the same time, the decision set is derived from true land types after investigation and validation. Then, the remote sensing decision table (RSDT) is constructed by linking condition set with decision set according to the sequential pixels in RSI. Fourth, we create one forward greedy searching algorithm based on VPRS to handle this RSDT. After adjusting parameters such as β and knowledge granularity diameter (KGD), we obtain the stable optimized results. Comparative experiments and evaluation show that the discrimination or retrieval accuracy of VPRS model is satisfying (overall accuracy: 87.32% and KHAT: 0.84) and better than original data. Moreover, data dimension has been decreased dramatically (from 12 to 3) and key attributes found by the model may be useful for specific retrieval in wetland inventories. 相似文献
53.
As a major ecosystem type, wetland provides invaluable ecological services. Environmental pollution, especially pesticides pollution should be paid more attention to keep wetlands healthy. Based on the risk quotient method, coupled with a probabilistic risk assessment model, this paper proposed a methodology suitable for ecological risk assessment of pesticide residues for wetland ecosystems. As an important industrializing and ecologically vulnerable area in China, the Taihu Lake wetland was chosen for the case study. The risks of eight pesticides in Taihu Lake wetland were assessed, as single substances and in mixtures. The assessment indicates that risks of the representative species are not significant. In general, the herbicide is found to be more toxic for algae, whereas insecticides pose more risks to zooplankton, insect and fish. For each pesticide in the wetland, the ecological risk it poses is acceptable. But the combined ecological risk posed by mixture can harm more than 10% of species of the wetland ecosystem, mainly dominated by dichlorvos, dimethoate and malathion contributions. These results imply that pesticide residues have been posing pressures on the ecosystem of the Taihu Lake wetland. It is recommended that proper countermeasures should be implemented to reduce the risks. 相似文献
54.
相思湖湿地公园是南宁市打造"中国水城"品牌的重要建设项目,既保护了湿地资源,也发挥了巨大的生态环境、经济及社会效益.就已完成景观绿化亮化提升工程的相思湖湿地公园展开相关调查,对其生态多样性进行分析及按照相关标准计算湿地景观特征指数,评价了其现状并提出保护对策.相思湖湿地公园具有丰富的动植物资源,从水域、林地、草地、沼泽、滩涂五种景观类型的数据可以看出:水域面积占到了52.74%,说明湿地功能显著;破碎度最大的是草地跟林地,分别达到了1.29和0.81,说明南宁市生态恢复工程和绿色提升工程效果明显.相思湖湿地公园是保护和利用当地湿地资源的有效措施. 相似文献
55.
基于RS/GIS的大辽河口湿地景观格局时空变化研究 总被引:2,自引:0,他引:2
基于1988、1995、2001和2007年的四期TM数据,应用GIS/RS技术与景观格局分析软件FRAGSTATS,定量分析大辽河口地区湿地景观格局的动态变化。结果表明,自1988年以来,大辽河口地区的湿地面积逐年增加,湿地景观多样性指数和均匀度指数呈现先降后升的趋势,景观破碎化程度增强。湿地类型变化主要表现在大量的自然湿地转化为人工湿地或人工景观,具体表现在转化为建筑用地、水稻田、养殖区。1988~1995年期间,大辽河口地区的环境质量下降,该地区生物生活环境的多样性降低,造成了一些物种种群数量的减少甚至消失;但是自1995年以后,该地区的景观多样性和均匀性升高,抗干扰能力增强,环境质量有所提高。研究区湿地景观格局的动态变化主要是受自然条件和人为活动干扰共同作用的结果。 相似文献
56.
Jan Peters Niko E.C. Verhoest Roeland Samson Marc Van Meirvenne Liesbet Cockx Bernard De Baets 《Ecological modelling》2009
Ensemble learning techniques are increasingly applied for species and vegetation distribution modelling, often resulting in more accurate predictions. At the same time, uncertainty assessment of distribution models is gaining attention. In this study, Random Forests, an ensemble learning technique, is selected for vegetation distribution modelling based on environmental variables. The impact of two important sources of uncertainty, that is the uncertainty on spatial interpolation of environmental variables and the uncertainty on species clustering into vegetation types, is quantified based on sequential Gaussian simulation and pseudo-randomization tests, respectively. An empirical assessment of the uncertainty propagation to the distribution modelling results indicated a gradual decrease in performance with increasing input uncertainty. The test set error ranged from 30.83% to 52.63% and from 30.83% to 83.62%, when the uncertainty ranges on spatial interpolation and on vegetation clustering, respectively, were fully covered. Shannon’s entropy, which is proposed as a measure for uncertainty of ensemble predictions, revealed a similar increasing trend in prediction uncertainty. The implications of these results in an empirical distribution modelling framework are further discussed with respect to monitoring setup, spatial interpolation and species clustering. 相似文献
57.
Víctor H. Marín Antonio Tironi Luisa E. Delgado Manuel Contreras Fernando Novoa Marcela Torres-Gómez René Garreaud Irma Vila Italo Serey 《Ecological modelling》2009
Contemporary shallow lakes theory proposes that these ecosystems may experience abrupt regime shifts due to small changes in controlling variables or triggers. So far, these triggers have been related mostly to nutrients as the immediate driver. During May 2004 the río Cruces wetland, a Ramsar site located in Southern Chile, underwent a major regime shift, from a clear water state, vastly dominated by the invasive macrophyte Egeria densa, to a turbid water state. In this article we show, through the analysis of long-term meteorological data that late fall 2004 was anomalous due to the presence of a high-pressure cell that persisted most of the month of May over Southern Chile. This climatic event caused an almost complete absence of precipitations and lower temperatures during this period, including several freezing nights. Eco-physiological experiments showed that 6 h exposure to desiccation kill the macrophyte. We developed a simple-biology dynamic model, under Stella Research 9.1, to show that the climatic anomaly of May 2004, plus the increased sedimentation of the wetland's floodplains, and the associated response of E. densa, explains its sudden disappearance from río Cruces wetland. 相似文献
58.
湿地自然保护区与当地居民 总被引:1,自引:1,他引:0
本文介绍了我国湿地保护区与当地居民的关系对保护区管理情况的影响,并提出了一些合理化建议,其中强调了通过政策和经济杠杆让当地居民在保护环境中受益,保护区才可能持续发展。 相似文献
59.
Wetland use by waterbirds is highly dependent on water depth, and depth requirements generally vary among species. Furthermore, water depth within wetlands often varies greatly over time due to unpredictable hydrological events, making comparisons of waterbird abundance among wetlands difficult as effects of habitat variables and water depth are confounded. Species-specific relationships between bird abundance and water depth necessarily are non-linear; thus, we developed a methodology to correct waterbird abundance for variation in water depth, based on the non-parametric regression of these two variables. Accordingly, we used the difference between observed and predicted abundances from non-parametric regression (analogous to parametric residuals) as an estimate of bird abundance at equivalent water depths. We scaled this difference to levels of observed and predicted abundances using the formula: ((observed − predicted abundance)/(observed + predicted abundance)) × 100. This estimate also corresponds to the observed:predicted abundance ratio, which allows easy interpretation of results. We illustrated this methodology using two hypothetical species that differed in water depth and wetland preferences. Comparisons of wetlands, using both observed and relative corrected abundances, indicated that relative corrected abundance adequately separates the effect of water depth from the effect of wetlands. 相似文献
60.