全文获取类型
收费全文 | 955篇 |
免费 | 91篇 |
国内免费 | 194篇 |
专业分类
安全科学 | 18篇 |
废物处理 | 15篇 |
环保管理 | 301篇 |
综合类 | 535篇 |
基础理论 | 227篇 |
污染及防治 | 41篇 |
评价与监测 | 32篇 |
社会与环境 | 59篇 |
灾害及防治 | 12篇 |
出版年
2024年 | 4篇 |
2023年 | 23篇 |
2022年 | 43篇 |
2021年 | 50篇 |
2020年 | 43篇 |
2019年 | 19篇 |
2018年 | 21篇 |
2017年 | 39篇 |
2016年 | 44篇 |
2015年 | 41篇 |
2014年 | 53篇 |
2013年 | 54篇 |
2012年 | 59篇 |
2011年 | 71篇 |
2010年 | 62篇 |
2009年 | 65篇 |
2008年 | 52篇 |
2007年 | 81篇 |
2006年 | 84篇 |
2005年 | 42篇 |
2004年 | 53篇 |
2003年 | 38篇 |
2002年 | 50篇 |
2001年 | 17篇 |
2000年 | 25篇 |
1999年 | 15篇 |
1998年 | 14篇 |
1997年 | 12篇 |
1996年 | 14篇 |
1995年 | 9篇 |
1994年 | 8篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 4篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有1240条查询结果,搜索用时 62 毫秒
511.
Restoring habitat corridors in fragmented landscapes using optimization and percolation models 总被引:2,自引:0,他引:2
Justin?C.?WilliamsEmail author Stephanie?A.?Snyder 《Environmental Modeling and Assessment》2005,10(3):239-250
Landscape fragmentation and habitat loss are significant threats to the conservation of biological diversity. Creating and
restoring corridors between isolated habitat patches can help mitigate or reverse the impacts of fragmentation. It is important
that restoration and protection efforts be undertaken in the most efficient and effective way possible because conservation
budgets are often severely limited. We address the question of where restoration should take place to efficiently reconnect
habitat with a landscape-spanning corridor. Building upon findings in percolation theory, we develop a shortest-path optimization
methodology for assessing the minimum amount of restoration needed to establish such corridors. This methodology is applied
to large numbers of simulated fragmented landscapes to generate mean and variance statistics for the amount of restoration
needed. The results provide new information about the expected level of resources needed to realize different corridor configurations
under different degrees of fragmentation and different characterizations of habitat connectivity (“neighbor rules”). These
results are expected to be of interest to conservation planners and managers in the allocation of conservation resources to
restoration projects. 相似文献
512.
The Great Basin Desert lies between the Sierra Nevada Mountains to the west and the Rocky Mountains to the east. Nearly 60%
of the area’s deserts and mountains (roughly 30 million ha) are managed by the U. S. Department of Interior’s Bureau of Land
Management. This area is characterized by low annual precipitation, diverse desert plant communities, and local economies
that depend on the products (livestock grazing, recreation, mining, etc.) produced by these lands. The ecological and economic
stability of the Great Basin is increasingly at risk due to the expansion of fire-prone invasive species and increase in wildfires.
To stem this loss of productivity and diversity in the Great Basin, the BLM initiated the “Great Basin Restoration Initiative”
in 1999 after nearly 0.7 million ha of the Great Basin burned in wildfires. The objective of the Great Basin Restoration Initiative
is to restore plant community diversity and structure by improving resiliency to disturbance and resistance to invasive species
over the long-term. To accomplish this objective, a strategic plan has been developed that emphasizes local participation
and reliance on appropriate science to ensure that restoration is accomplished in an economical and ecologically appropriate
manner. If restoration in the Great Basin is not successful, desertification and the associated loss of economic stability
and ecological integrity will continue to threaten the sustainability of natural resources and people in the Great Basin. 相似文献
513.
黄土高塬沟壑区植被恢复对不同地貌部位土壤可蚀性的影响 总被引:4,自引:0,他引:4
通过采集不同地貌部位(塬面、塬坡和沟坡)各土地利用(农地、草地、灌木地和林地)坡面土壤和根系样品,采用综合土壤可蚀性指数(CSEI)评价了植被恢复对土壤可蚀性的影响。结果表明:(1)不同地貌部位的CSEI差异显著,沟坡CSEI较塬坡和塬面分别增加8.1%和77.7%。(2)塬面草地、灌木地和林地的CSEI较农地分别降低21.1%、29.2%和28.8%;而塬坡和沟坡林地CSEI均低于其他土地利用。(3)CSEI与粘粒含量、砂粒含量、毛管孔隙度、根重密度、根平均直径、根长密度及根表面积密度均呈极显著负相关,而与粉粒含量和土壤容重呈显著正相关关系;粉粒含量、土壤容重和根重密度是影响CSEI的关键因素,其中粉粒含量对CSEI的直接影响最大,而根重密度通过直接或间接作用对CSEI产生负相关影响。建议在塬面上以灌木作为植被恢复模式的首选,而在塬坡和沟坡上选择以乔木为优势群落的恢复模式对水土流失的控制更为有效。 相似文献
514.
国土生态修复研究的演进脉络与前沿进展 总被引:4,自引:2,他引:2
国土生态修复是推进生态保护修复、服务生态文明建设和加速现代化发展的重大举措,对于人类生存和社会进步具有重要意义。采用文献计量和网络分析方法,以Web of Science数据库中1196篇文献作为研究对象,剖析国土生态修复研究动态趋势、合作关系和研究热点,进一步辨析演进脉络和前沿进展。研究表明:(1)国土生态修复问题受到学术界广泛关注,研究文献主要集中在生态学和环境学领域;(2)美国等发达国家的学者和机构在该领域影响力突出,中国显现出强劲的发展潜力,是新兴合作团体核心成员,中国科学院已成为全球最具影响力的机构;(3)以生态为核心的水、土壤和人口等要素是该领域主要研究对象,人文和自然学科交叉下的综合性研究是该领域未来发展趋势。 相似文献
515.
516.
517.
518.
519.
Historical and Future Stream Temperature Change Predicted by a Lidar‐Based Assessment of Riparian Condition and Channel Width 下载免费PDF全文
Gustav B. Seixas Timothy J. Beechie Caleb Fogel Peter M. Kiffney 《Journal of the American Water Resources Association》2018,54(4):974-991
Riparian forests attenuate solar radiation, thereby mediating an important component of the thermal budget of streams. Here, we investigate the relationship between riparian degradation, stream temperature, and channel width in the Chehalis River Basin, Washington State. We used lidar data to measure canopy opening angle, the angle formed between the channel center and trees on both banks; we assumed historical tree heights and calculated the change in canopy angle relative to historical conditions. We then developed an empirical relationship between canopy angle and water temperature using existing data, and simulated temperatures between 2002 and 2080 by combining a tree growth model with climate change scenarios from the NorWeST regional prediction. The greatest change between historical and current conditions (~7°C) occurred in developed portions of the river network, with the highest values of change predicted at channel widths less than ~40 m. Tree growth lessened climate change increases in maximum temperature and the length of river exceeding biologically critical thresholds by ~50%–60%. Moreover, the maximum temperature of channels with bankfull widths less than ~50 m remained similar to current conditions, despite climate change increases. Our findings are consistent with a possible role for the riparian landscape in explaining the low sensitivity of stream temperatures to air temperatures observed in some small mountain streams. 相似文献
520.