全文获取类型
收费全文 | 787篇 |
免费 | 33篇 |
国内免费 | 34篇 |
专业分类
安全科学 | 95篇 |
废物处理 | 18篇 |
环保管理 | 86篇 |
综合类 | 183篇 |
基础理论 | 389篇 |
污染及防治 | 24篇 |
评价与监测 | 23篇 |
社会与环境 | 30篇 |
灾害及防治 | 6篇 |
出版年
2023年 | 3篇 |
2022年 | 7篇 |
2021年 | 12篇 |
2020年 | 13篇 |
2019年 | 8篇 |
2018年 | 8篇 |
2017年 | 16篇 |
2016年 | 22篇 |
2015年 | 15篇 |
2014年 | 17篇 |
2013年 | 29篇 |
2012年 | 34篇 |
2011年 | 49篇 |
2010年 | 45篇 |
2009年 | 48篇 |
2008年 | 69篇 |
2007年 | 70篇 |
2006年 | 70篇 |
2005年 | 51篇 |
2004年 | 40篇 |
2003年 | 29篇 |
2002年 | 17篇 |
2001年 | 18篇 |
2000年 | 24篇 |
1999年 | 30篇 |
1998年 | 19篇 |
1997年 | 20篇 |
1996年 | 20篇 |
1995年 | 18篇 |
1994年 | 12篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1975年 | 1篇 |
排序方式: 共有854条查询结果,搜索用时 364 毫秒
291.
292.
Aggregation via pheromone signalling is essential for tree-killing bark beetles to overcome tree defenses and reproduce within hosts. Pheromone production is a trait that is linked to fitness, so high individual variation is paradoxical. One explanation is that the technique of measuring static pheromone pools overestimates true variation among individuals. An alternative hypothesis is that aggregation behaviour dilutes the contribution of individuals to the trait under selection and reduces the efficacy of natural selection on pheromone production by individuals. We compared pheromone measurements from traditional hindgut extractions of female southern pine beetles with those obtained by aerating individuals till they died. Aerations showed greater total pheromone production than hindgut extractions, but coefficients of variation (CV) remained high (60-182%) regardless of collection technique. This leaves the puzzle of high variation unresolved. A novel but simple explanation emerges from considering bark beetle aggregation behaviour. The phenotype visible to natural selection is the collective pheromone plume from hundreds of colonisers. The influence of a single beetle on this plume is enhanced by high variation among individuals but constrained by large group sizes. We estimated the average contribution of an individual to the pheromone plume across a range of aggregation sizes and showed that large aggregation sizes typical in mass attacks limit the potential of natural selection because each individual has so little effect on the overall plume. Genetic variation in pheromone production could accumulate via mutation and recombination, despite strong effects of the pheromone plume on the fitness of individuals within the aggregation. Thus, aggregation behaviour, by limiting the efficacy of natural selection, can allow the persistence of extreme phenotypes in nature. 相似文献
293.
Animal colour signals serve important functions in intraspecific interactions, including species recognition, mate choice and agonistic behaviour. An increasing interest concerns ultraviolet (UV) wavelengths, for instance studies on the effect of UV in mating decisions. More recently, some studies also established that UV signals affect intrasexual interactions. We studied the role of UV during aggressive encounters between male three-spined sticklebacks (Gasterosteus aculeatus), a species in which UV has an effect on female and male mate choice and shoaling behaviour. To that aim, we compared the aggressive response of a territorial male to male intruders, either seen in UV-including (UV+) or UV-lacking (UV-) conditions. Our prediction was that, if UV wavelengths are used in male-male competition, a territorial male should show less competitive behaviour towards an intruder representing a lower threat, i.e. the one presented without UV light. Male sticklebacks showed significantly lower levels of aggression towards male opponents lacking an UV component to their coloration than male opponents possessing this colour component. Discrimination was not influenced by a difference in brightness between the UV+ and UV- stimuli. Finally, we present some reflectance-spectrophotometrical data of two skin regions (cheek and abdomen) of the experimental males and analysed relationships between colorimetric variables, body variables and behaviour. Our study emphasises that UV visual cues are of importance in different communicational tasks in the three-spined stickleback. 相似文献
294.
苏南模式固有的弊端所导致的"村村点火、乡乡冒烟"的经济格局导致了严重的环境问题。随着新苏南模式的诞生,环境问题有所改善,但仍然存在着固有的路径依赖。通过对原因的分析,可以发现,政府、企业与公众的共同参与是解决问题的关键,具体而言:一是转换政府角色,引入市场机制;二是公众主动参与,发展第三组织;三是企业积极参与,发展生态产业。 相似文献
295.
为有效提高水雾综合除尘性能,基于水雾捕尘过程及抑尘作用机理,从复合抑尘剂润湿、吸湿、黏结作用组分出发,讨论不同性质粉尘与抑尘剂各组分间匹配协同关系,进而研究复合型水雾抑尘剂优选方法。结果表明:湿润组分优选疏水端含有碳碳双键、醚基或链间存在氢键的表面活性剂;通过改变疏水基链长、不饱和度和支链数等方法,使湿润组分亲水、亲油性与粉尘相匹配。吸湿组分优选体心立方晶胞结构、溶解度相对较小的无机盐或混合配方无机盐,或者含极性强、能形成氢键的基团且空间结构复杂的有机吸湿剂。黏结组分优选溶液黏度高、交联网状、结构复杂的高分子聚合物。在上述组分优选的基础上,通过抑尘剂复配性能实验合理确定各组分的最优配比。 相似文献
296.
297.
298.
组合赋权法在线性工程线路方案环境比选中的应用 总被引:1,自引:0,他引:1
线性工程中线路方案的环境比选是减缓环境影响的重要手段。为了提高环境比选工作的效率和准确性,提出主观赋权和客观赋权相结合的组合赋权法用于线路方案的环境比选。构建了线路方案环境影响评价的层次结构模型,采用层次分析法实现环境因素的主观赋权,采用标准离差法实现环境影响评价指标的客观赋权,进而得到各环境影响评价指标相对总体环境影响评价目标的权重用于计算总的环境评价结果。通过实例验证了该方法的有效性和实用性。 相似文献
299.
脱硝在线连续监测系统与脱硫在线监测系统相比,脱硝装置在电除尘(或布袋除尘)装置之前,而脱硫装置在除尘装置之后。由于安装位置的前移,脱硝CEMS系统运行环境将比脱硫CEMS系统更为恶劣,脱硝装置将面临着高温、高粉尘、高负压等一系列问题。本文结合脱硝装置工况、HJ562-2010和HJ563-2010环保标准提出脱硝CEMS系统对设备的要求以及设备维护难点。 相似文献
300.
《International Journal of Sustainable Engineering》2013,6(1):37-56
This paper presents a generic framework integrating environmental and social criteria leading to a comprehensive selection process of green suppliers. Traditionally, price, quality, lead time and flexibility are considered for the supplier selection. With the increase in awareness of environmental and social responsibility issues, many companies are tending towards adopting green concepts and sourcing green suppliers. This study proposes a framework consisting of environmental (E), green (G) and organisational (O) factors that are required for the green supplier selection process. These factors are further classified as criteria for which attributes are presented. A hierarchy is constructed to facilitate in evaluating the importance of the selected criteria and alternatives of green suppliers. To cater to the multi-criteria decision-making approach with both quantitative and qualitative attributes, we applied the multiple attribute utility theory, which is a decision support that helps managers formulating viable sourcing strategies. A hypothetical example is presented to illustrate the applicability of the approach. 相似文献