全文获取类型
收费全文 | 801篇 |
免费 | 68篇 |
国内免费 | 248篇 |
专业分类
安全科学 | 10篇 |
废物处理 | 7篇 |
环保管理 | 244篇 |
综合类 | 398篇 |
基础理论 | 237篇 |
污染及防治 | 81篇 |
评价与监测 | 72篇 |
社会与环境 | 67篇 |
灾害及防治 | 1篇 |
出版年
2023年 | 11篇 |
2022年 | 15篇 |
2021年 | 15篇 |
2020年 | 18篇 |
2019年 | 20篇 |
2018年 | 25篇 |
2017年 | 32篇 |
2016年 | 36篇 |
2015年 | 51篇 |
2014年 | 47篇 |
2013年 | 61篇 |
2012年 | 45篇 |
2011年 | 68篇 |
2010年 | 51篇 |
2009年 | 58篇 |
2008年 | 39篇 |
2007年 | 58篇 |
2006年 | 62篇 |
2005年 | 37篇 |
2004年 | 39篇 |
2003年 | 38篇 |
2002年 | 31篇 |
2001年 | 37篇 |
2000年 | 21篇 |
1999年 | 21篇 |
1998年 | 26篇 |
1997年 | 21篇 |
1996年 | 23篇 |
1995年 | 16篇 |
1994年 | 13篇 |
1993年 | 11篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 10篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有1117条查询结果,搜索用时 15 毫秒
841.
珠江河口水生生物中多溴联苯醚的分布 总被引:24,自引:7,他引:17
对珠江河口生物样品中多溴联苯醚(PBDEs)的含量进行了检测.所采集的鱼类(鱼、大黄鱼、银鲳、舌鳎、龙头鱼),虾类(刀额新对虾、近缘新对虾)及虾蛄类生物样品肌肉组织中10种PBDEs(BDE28,47,66,100,99,85,154,153,138,183)的含量分别为37.8~407.1 ng·g-1(脂肪归一化浓度)、49.0~239.1 ng·g-1和142~444.5 ng·g-1.所有样品中,BDE47相对含量最高,其相对于∑< 相似文献
842.
843.
844.
Peter A. Cott Paul K. Sibley W. Murray Somers Michael R. Lilly Andrew M. Gordon 《Journal of the American Water Resources Association》2008,44(2):343-359
Abstract: The effects of water level fluctuations on fish and other aquatic biota, with an emphasis on winter water withdrawal in northern regions is reviewed. Water demands for population growth and development are adding pressure on water reserves, particularly when coupled with changing climatic conditions. Water level fluctuations can have adverse effects on the environment, most notably to hydrologic and biotic processes ranging in magnitude from the micro‐scale to landscape level. Water level management of lakes and reservoirs can affect all forms of aquatic biota. The severity of effect is dependant on the magnitude, duration and timing of the fluctuation, and the species exposed. In northwestern Canada and northern Alaska, water is withdrawn from water bodies to construct ice‐roads and other winter based developments. Biota in small, isolated water bodies are particularly sensitive to reductions in winter water levels. Water withdrawals can reduce the oxygen available to overwintering fish, while reduced water levels can reduce habitat for fish and furbearers, and freeze littoral areas killing plants, invertebrates, and fish eggs. Regulatory winter water withdrawal thresholds have been developed in the Northwest Territories and Alaska and continue to be refined as new data becomes available. The use of thresholds can help minimize or avoid negative impacts to the environment, particularly fish, from winter water withdrawal activities. Many different factors may influence the effect that winter water withdrawal has on a water body, such as basin shape, substrate and location. More research is warranted to better understand the linkages between anthropogenic and natural water level fluctuations and their combined effect on aquatic ecosystems. A general decision support system is proposed for minimizing risk to aquatic life from winter water withdrawal activities. 相似文献
845.
Geoffrey E Petts 《Journal of the American Water Resources Association》2009,45(5):1071-1086
Abstract: Concerns for water resources have inspired research developments to determine the ecological effects of water withdrawals from rivers and flow regulation below dams, and to advance tools for determining the flows required to sustain healthy riverine ecosystems. This paper reviews the advances of this environmental flows science over the past 30 years since the introduction of the Instream Flow Incremental Methodology. Its central component, Physical HABitat SIMulation, has had a global impact, internationalizing the e‐flows agenda and promoting new science. A global imperative to set e‐flows, including an emerging trend to set standards at the regional scale, has led to developments of hydrological and hydraulic approaches but expert judgment remains a critical element of the complex decision‐making process around water allocations. It is widely accepted that river ecosystems are dependent upon the natural variability of flow (the flow regime) that is typical of each hydro‐climatic region and upon the range of habitats found within each channel type within each region. But as the sophistication of physical (hydrological and hydraulic) models has advanced emerging biological evidence to support those assumptions has been limited. Empirical studies have been important to validate instream flow recommendations but they have not generated transferable relationships because of the complex nature of biological responses to hydrological change that must be evaluated over decadal time‐scales. New models are needed to incorporate our evolving knowledge of climate cycles and morphological sequences of channel development but most importantly we need long‐term research involving both physical scientists and biologists to develop new models of population dynamics that will advance the biological basis for 21st Century e‐flow science. 相似文献
846.
847.
水生植物群落在湖泊生态修复过程中作用显著,但目前人工重建的水生植物群落抗外界干扰能力弱,群落稳定性差,这就需要我们对人工重建的水生植物群落结构及其演替的生态学过程进行研究,从而探索受损群落的修复途径。于2003年在富营养化水体中采用物理生态工程进行了水生植物群落的重建研究,对群落演替动态变化过程进行了持续3年的观测。结果表明:水生植物之间发生生态位重叠时,其结果往往是以一个物种取代另一个物种,随着生态位重叠程度下降,种间关系和群落结构趋于稳定;而当物种空间位置错开时,生长期相近的物种共存则变为可能,因此在群落的构建过程中应当避免同时引入生态位重叠较高的物种,应注意植物间时间序列及空间结构的分离;此外还通过物种间的竞争表现,对几种常见水生植物构建的群落稳定性做了初步探讨. 相似文献
848.
北京北运河河流生态系统健康评价 总被引:22,自引:8,他引:22
随着城市化的不断推进,北京河流生态系统面临着巨大挑战.以北京市北运河水系为例,于2015年7月对25个样点进行了野外调查,采集了浮游植物、底栖动物、水环境因子和栖息地环境质量数据.选取涵盖水生生物、水文、水质和栖息地的22个候选评价指标,采用主成分分析(principal component analysis,PCA)和相关分析进行筛选,并用熵权法确定各评价指标权重,构建了北运河河流生态系统健康评价指标体系,通过河流生态健康综合指数对其健康状况进行了评价.结果表明,北运河河流生态系统健康评价指标体系包含浮游植物Shannon-Wiener多样性指数、底栖动物Shannon-Wiener多样性指数、水温、生化需氧量、氨氮、氟化物、锌、石油类和栖息地环境质量评价指标(qualitative habitat evaluation index,QHEI)9项指标;全流域25个样点中,有12%为Ⅰ级和Ⅱ级,36%为Ⅲ级,超过50%为Ⅳ级和Ⅴ级.北运河河流生态系统的健康状况总体较差,其中,上游地区普遍较好,中下游地区相对较差,且呈现出较强的空间异质性.南沙河、清河中游、通惠河干流的健康状况普遍较差,相对较好的凉水河上游地区和温榆河支流交错镶嵌其中,形成了北运河水系复杂的河流生态系统现状. 相似文献
849.
通过分析国内外水生态分区、水环境功能分区现状,研究了各种分区指标选取依据及指标体系特点。通过对比三峡库区已有的生态功能分区依据及指标体系特点,提出了已有分区指标体系的不足之处,即尚未充分考虑水生要素。在三峡库区流域自然要素及水生态特征的分析的基础上,建立了三峡库区流域水生态分区体系.明确了各级分区的主要内容与分区依据,提出了各级分区的特征指标,从而建立了流域水生态分区的指标与方法体系。结果表明,三峡库区流域包括2级水生态区。该研究在GIS技术支持下,采用多指标叠加分析和专家判断方法,将三峡库区流域划分为6个一级区,对不同分区的水生态系统特征及其所面临的生态环境问题进行了总结,为基于水生态区的环境管理提供了技术支撑。 相似文献
850.