全文获取类型
收费全文 | 62篇 |
免费 | 7篇 |
国内免费 | 5篇 |
专业分类
林业 | 4篇 |
基础科学 | 11篇 |
10篇 | |
综合类 | 25篇 |
水产渔业 | 22篇 |
植物保护 | 2篇 |
出版年
2024年 | 2篇 |
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 2篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 4篇 |
2017年 | 5篇 |
2016年 | 1篇 |
2015年 | 3篇 |
2014年 | 2篇 |
2013年 | 3篇 |
2012年 | 10篇 |
2011年 | 3篇 |
2010年 | 4篇 |
2008年 | 2篇 |
2007年 | 2篇 |
2006年 | 1篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2003年 | 4篇 |
2002年 | 1篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1996年 | 1篇 |
排序方式: 共有74条查询结果,搜索用时 15 毫秒
31.
32.
从满足河道的基本功能出发,结合丽水市农村河道的现状,因地制宜提出农村河道在生态化治理建设中应采取的综合措施,充分发挥农村河流生态系统在生态、亲水、景观等方面的功能,促进资源和社会的可持续发展。 相似文献
33.
- One of the major challenges to ensure effective restoration of estuarine habitats is to establish success criteria to determine whether the goals of restoration are met.
- The aim of this work is to propose and test an approach to identify reference conditions and assess the recovery of nekton (fish, decapods and cephalopods) assemblages at seagrass restoration sites.
- Nekton sampling took place from 2014 to 2017 in the northern Venice lagoon (northern Adriatic Sea, Italy) during spring at eight sites subjected to seagrass (Zostera marina and Zostera noltei) transplantation. In spring 2016, five natural seagrass sites in the same area were additionally sampled, and physico‐chemical water parameters and habitat structure were also recorded.
- A multivariate generalized linear model approach was adopted in order to disentangle the relative effect of water quality and seagrass habitat structure on nekton assemblages of natural habitats. Models were subsequently employed to predict species composition of nekton fauna at each transplantation site, to identify the reference assemblage expected under site‐specific abiotic and habitat characteristics.
- The average distance of the observed assemblage from reference conditions was used to track temporal trajectories of nekton colonization at transplantation sites, and to ultimately evaluate the recovery rate towards restoration goals.
- This study highlights how a predictive approach could serve management purposes in ecological restoration, providing a concise tool to assess the functionality of restored habitats for associated fauna.
34.
针对菊芋收获作业要求,研制了大挖深菊芋收获机。该机由外倾整体式条形挖掘铲、两级抖动链式输送分离器及机架、地轮构成,可一次性完成菊芋挖掘、芋土分离、输送、铺放。田间试验表明:该机能在250~500 mm挖掘深度,初霜冻、菊芋团块根系发达地块,克服冻土块、砾石卡塞导致的土壤拥堵,实现持续稳定作业; 对菊芋收获质量好,芋土分离效果良好,损失率、伤薯率、含杂率分别小于1.75%、4.8%、4.5%, 满足菊芋收获作业要求。 相似文献
35.
底泥能有效改善土壤的理化性质,并且为植物的生长提供良好的环境。除此之外,底泥还能用作人造土壤,可用于园林绿化的客土更换,从而避免因土壤置换造成采土地区的水土流失现象的产生。由于底泥的质量容易控制,创新底泥在城市绿化中的应用模式具有巨大潜力。
相似文献
36.
环保清淤是为改善水质和水生态环境而进行的清淤,也是黑臭河道综合治理中的重要环节.本文总结了在珠三角感潮河道底泥环保清淤的工程实践中,较常采用的两个方案:抓斗式挖泥船+泥驳运输方案、绞吸式挖泥船+输泥管输送方案,并由此形成的管道搅拌脱水固结一体化技术、带式机脱水固结一体化技术、板框机脱水固化一体化技术等系列的成熟技术,在环保清淤的处理处置过程中不造成"二次污染",并实现了退水达标排放、固化淤泥资源化利用的目标. 相似文献
37.
38.
In this study, the results of investigations of organic matter decomposition in natural and dredged areas of the inner Puck Bay (Baltic Sea) are presented. The dredging of relatively deep pits causes environmental problems. Researched post-dredging pits are sediment traps in which 3 times more organic carbon (Corg), 3.5 times more total nitrogen (Ntot), about 1.5 times more organic phosphorus (Porg) and 1.7 times more total phosphorus (Ptot) accumulate as compared to the non-dredged regions; they are also characterized by very intensive decomposition of organic matter. About 42, 44, 95 and 50% of the annual load of, respectively, Corg, Ntot, Porg and Ptot undergo decomposition in the dredged area, whereas the respective values for natural seabed are ca. 11, 44, 41 and 21%. Reduction of nitrogen in the pit occurs mainly through ammonification, while in the natural areas of seabed denitrification prevails. In non-dredged sediments, 84% of the released nitrogen comes from denitrification whereas in the pit, it is only 18%. Organic matter degradation in the pit sediments manifests itself by a 7-fold increase in the phosphate flux into near-bottom water as compared to natural seabed. The observed phosphate flux originated from the organic matter as well as from the decomposition of inorganic phosphorus compounds. Periodically, sulphate reduction in the pit sediments resulted in hydrogen sulfide occurrence. 相似文献
39.
污染底泥修复技术进展 总被引:11,自引:0,他引:11
综述污染底泥的修复技术,探讨其发展状况及存在的问题。目前主要有疏浚、掩蔽等物理修复技术和生物修复技术。物理修复效果明显,但工程量大,投入大;生物修复具有投入低,处理量大,但速度慢,且难以达标。从经费投入和处理效果来看,底泥修复应发展疏浚和生物处理相结合,实现底泥的资源化再利用。在做好污染底泥处理的同时,关键要控制污染源的排放。 相似文献
40.
模拟与分析白洋淀试点区域水质改善工程前后的水质变化情况,探索水质改善效果,为白洋淀水质改善提供思路与经验。基于实测地形、气象数据、水质监测数据、现状污染源、大气沉降、风扰底泥释放等数据资料,运用MIKE软件构建了白洋淀二维水动力和水质数学模型,选取现状水量未清淤(方案一)、增加补水流量1.5倍+未清淤(方案二)、增加补水流量2.0倍+清淤0.1 m(方案三)、增加补水流量2.0倍+清淤0.2 m(方案四)4种优化方案,模拟了典型时刻下白洋淀区域内的流场分布形态和主要污染物迁移扩散规律。结果表明:白洋淀淀区内水体流动速度普遍较小,在增大补水流量和清淤的情况下,流场的改变集中于入淀河流的下游,几乎不改变主淀中的流场分布。随着清淤深度的增大,底泥的污染物释放作用进一步削弱,但削弱的幅度较小。由此确定对白洋淀底泥厚度较大、水质污染较为严重的区域开展清淤工作,建议清淤厚度0.2 m左右。在清淤的基础上,对淀区进行合理补水,入口河流选用常年水质较好的河段,建议补水体积不超过现状补水方案的2倍。 相似文献