全文获取类型
收费全文 | 211篇 |
免费 | 28篇 |
国内免费 | 26篇 |
专业分类
安全科学 | 22篇 |
废物处理 | 11篇 |
环保管理 | 33篇 |
综合类 | 74篇 |
基础理论 | 38篇 |
污染及防治 | 34篇 |
评价与监测 | 30篇 |
社会与环境 | 12篇 |
灾害及防治 | 11篇 |
出版年
2023年 | 3篇 |
2022年 | 1篇 |
2021年 | 6篇 |
2020年 | 6篇 |
2019年 | 11篇 |
2018年 | 5篇 |
2017年 | 9篇 |
2016年 | 6篇 |
2015年 | 5篇 |
2014年 | 10篇 |
2013年 | 15篇 |
2012年 | 10篇 |
2011年 | 15篇 |
2010年 | 11篇 |
2009年 | 18篇 |
2008年 | 21篇 |
2007年 | 14篇 |
2006年 | 15篇 |
2005年 | 13篇 |
2004年 | 7篇 |
2003年 | 7篇 |
2002年 | 11篇 |
2001年 | 8篇 |
2000年 | 5篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1990年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1980年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有265条查询结果,搜索用时 15 毫秒
51.
GENTILE FRANCESCO FICETOLA†‡ EMILIO PADOA-SCHIOPPA† FIORENZA DE BERNARDI 《Conservation biology》2009,23(1):114-123
Abstract: Studies on riparian buffers have usually focused on the amount of land needed as habitat for the terrestrial life stages of semiaquatic species. Nevertheless, the landscape surrounding wetlands is also important for other key processes, such as dispersal and the dynamics of metapopulations. Multiple elements that influence these processes should therefore be considered in the delineation of buffers. We analyzed landscape elements (forest cover, density of roads, and hydrographic network) in concentric buffers to evaluate the scale at which they influence stream amphibians in 77 distinct landscapes. To evaluate whether our results could be generalized to other contexts, we determined whether they were consistent across the study areas. Amphibians required buffers of 100–400 m of suitable terrestrial habitat, but interspecific differences in the amount of habitat were large. The presence of amphibians was related to roads and the hydrographic network at larger spatial scales (300–1500 m), which suggests that wider buffers are needed with these elements. This pattern probably arose because these elements influence dispersal and metapopulation persistence, processes that occur at large spatial scales. Furthermore, in some cases, analyses performed on different sets of landscapes provided different results, which suggests caution should be used when conservation recommendations are applied to disparate areas. Establishment of riparian buffers should not be focused only on riparian habitat, but should take a landscape perspective because semiaquatic species use multiple elements for different functions. This approach can be complex because different landscape elements require different spatial extents. Nevertheless, a shift of attention toward the management of different elements at multiple spatial scales is necessary for the long-term persistence of populations. 相似文献
52.
和田河年径流变化规律研究 总被引:15,自引:1,他引:14
根据和田河实测年径流资料,应用小波分析、R/S分析等多种方法,探讨了在气候变化和人类活动影响下,和田河年径流变化规律及其成因。结果表明,和田河年径流存在减少趋势,且具有一定的持续性。通过径流变化的影响因素分析表明,上游出山口处两支流的径流变化主要受气温升高的影响,下游入塔里木河处除受降水减少的影响外,主要是由于人类对水土资源开发进程的加快,人类活动是其径流变化的主要原因。 相似文献
53.
54.
研究了钛酸四丁酯水解制备TiO2粉末的两大影响因素R值(R是水和钛酸四丁酯的摩尔比)和烧结温度。通过光催化氧化五氯苯酚钠实验,结合对催化剂晶型结构、比表面积的表征分析,综合评价所制备的催化剂。实验结果表明,当R=100、烧结温度为650℃、烧结时间为1h,钛酸四丁酯水解所制备的T iO2半导体光催化剂催化活性和使用寿命均比较理想。从晶型结构分析,当催化剂中锐钛矿和金红石胺一定比例共存时,其催化活性较单-金红石或锐钛矿高,实难认为锐钛矿与金红石的最佳比约为2:1。 相似文献
55.
56.
57.
三维电极对水中染料降解脱色处理 总被引:5,自引:0,他引:5
研究了在传统二维电解槽的铁板电极之间填充锰砂并鼓气搅拌,得到三相三维电极流化床反应器,对比两种反应器对酸性大红3R染色模拟废水降解脱色作用,考察了槽电压、支持电解质质量浓度、反应时间等因素对两种反应器处理染料脱色率的影响。实验表明,这些因素对酸性大红3R的降解脱色均有不同程度的影响,在相同条件下,三相三维电极流化床反应器比二维电极电解槽的处理脱色速度快和处理效率高,在不同处理时间内,脱色率可提高30%~50%。紫外-可见光吸收光谱分析表明,该方法不仅能对酸性大红3R的生色基团进行降解脱色,且对萘环不饱和共轭体系也具有破坏降解作用。 相似文献
58.
Further studies on the influence of zeolite type A on metal transfer in the activated sludge process
Investigations were carried out to determine the effect of zeolite type A on metal removal by activated sludge using laboratory activated sludge simulations. They were operated at constant aerator sludge age and settler surface loading. Different concentrations of raw zeolite and zeolite extracted from washing powder (0, 15, 30, 60, 120 mgl?1) were introduced into the simulations. The zeolite was added at two degrees of calcium exchanged for sodium, 25 and 75% of the maximum exchange capacity. Metals were added at concentrations typical of mixed domestic-industrial waste waters. The results show that there was no adverse effect on metal removal by the laboratory activated sludge simulations in the presence of zeolite type A. 相似文献
59.
中国雨日变化趋势的分形研究 总被引:3,自引:0,他引:3
利用1951-2002年中国752个台站的雨日资料,运用分形理论和R/S分析法,研究并预测了中国五大降水区年雨日的气候变化趋势.研究表明:中国五大降水区未来的年雨日变化趋势与过去50a的变化有着很好的自相似性.为了更深入研究雨日的未来的变化,设计了两项Hurst指数试验,用两项试验结果与年雨日年际变化趋势的对应关系来推断未来的变化趋势及其转折与突变.结果表明:中国五大降水区年雨日有着一致的减少趋势,但其变化呈现显著的地域分异特征.依照五大降水区的气候倾向率,西北区、西南区、青藏高原区、东部北方区、东部南方区未来平均每10a雨日减少分别为4.1d,11.4d,3.7d,6.8d和5.9d,其中西南区年雨日减少最多.期间,中国五大降水区虽有气候变化的转折,但不存在雨日气候变化的突变点. 相似文献
60.
For a complete cost-benefit analysis of durable infrastructures, it is important to understand how the value of non-market goods such as transit time and environmental quality changes as incomes rise in the long-run. We use difference-in-differences and spatial differencing to estimate the land price capitalization effects of metro rail in Berlin, Germany today and a century ago. Over this period, the negative implicit hedonic price of rail noise tripled. Our results imply income elasticities of the value of noise reduction and transport access of 2.2 and 1.4, substantially exceeding cross-sectional contingent valuation estimates. 相似文献