全文获取类型
收费全文 | 1659篇 |
免费 | 86篇 |
国内免费 | 169篇 |
专业分类
安全科学 | 132篇 |
废物处理 | 33篇 |
环保管理 | 344篇 |
综合类 | 538篇 |
基础理论 | 581篇 |
污染及防治 | 58篇 |
评价与监测 | 65篇 |
社会与环境 | 128篇 |
灾害及防治 | 35篇 |
出版年
2024年 | 5篇 |
2023年 | 35篇 |
2022年 | 57篇 |
2021年 | 40篇 |
2020年 | 47篇 |
2019年 | 38篇 |
2018年 | 31篇 |
2017年 | 45篇 |
2016年 | 58篇 |
2015年 | 58篇 |
2014年 | 73篇 |
2013年 | 120篇 |
2012年 | 66篇 |
2011年 | 103篇 |
2010年 | 95篇 |
2009年 | 77篇 |
2008年 | 77篇 |
2007年 | 83篇 |
2006年 | 104篇 |
2005年 | 87篇 |
2004年 | 97篇 |
2003年 | 70篇 |
2002年 | 59篇 |
2001年 | 80篇 |
2000年 | 46篇 |
1999年 | 42篇 |
1998年 | 33篇 |
1997年 | 27篇 |
1996年 | 29篇 |
1995年 | 19篇 |
1994年 | 13篇 |
1993年 | 21篇 |
1992年 | 9篇 |
1991年 | 20篇 |
1990年 | 9篇 |
1989年 | 3篇 |
1988年 | 12篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1972年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有1914条查询结果,搜索用时 0 毫秒
711.
Building future scenarios and uncovering persisting challenges of participatory forest management in Chilimo Forest, Central Ethiopia 总被引:1,自引:0,他引:1
Kassa H Campbell B Sandewall M Kebede M Tesfaye Y Dessie G Seifu A Tadesse M Garedew E Sandewall K 《Journal of environmental management》2009,90(2):1004-1013
We examined the changes in forest status and people's livelihoods through building future scenarios for Chilimo Forest in Central Ethiopia where participatory forest management (PFM) is being implemented. Participatory methods were employed to collect data, and a dynamic modeling technique was applied to explore trends over time. By integrating the more quantitative model outputs with qualitative insights, information on forests and livelihoods was summarized and returned to users, both to inform them and get feedback. A scenario of open access without PFM provides higher income benefits in the short term but not over the longer term, as compared to a scenario with PFM. Follow up meetings were organized with national decision makers to explore the possibility of new provisions in the national forest proclamation related to joint community-state ownership of forests. Project implementers must constantly work towards improving short term incentives from PFM, as these may be insufficient to garner support for PFM. Other necessary elements for PFM to succeed include: ensuring active participation of the communities in the process; and, clarifying and harmonizing the rules and regulations at different levels. 相似文献
712.
Paolo C. Campo Guillermo A. Mendoza Philippe Guizol Teodoro R. Villanueva Franois Bousquet 《Journal of environmental management》2009,90(11):3607-3615
This paper describes the experiences and lessons learned in applying a multi-agent systems (MAS) model to study the dynamics and complex interactions among stakeholders in the management of community-based forests. The MAS model is developed using the companion modelling (ComMod) approach, which allows for a collaborative development of the model between the stakeholders and researchers. This approach involves the development and application of role-playing games (RPGs) and computer simulation as learning tools and to validate the model. Inferences are drawn from the learning and negotiation processes that the stakeholders and researchers underwent in the collaborative development of the MAS model. These processes ultimately led to the development of a collaborative resource management plan. The approach and the MAS model were applied to a case study involving a community-based forest managed by three villages in the island of Palawan, Philippines. 相似文献
713.
Saproxylic (dead-wood-associated) and old-growth species are among the most threatened species in European forest ecosystems,
as they are susceptible to intensive forest management. Identifying areas with particular relevant features of biodiversity
is of prime concern when developing species conservation and habitat restoration strategies and in optimizing resource investments.
We present an approach to identify regional conservation and restoration priorities even if knowledge on species distribution
is weak, such as for saproxylic and old-growth species in Switzerland. Habitat suitability maps were modeled for an expert-based
selection of 55 focal species, using an ecological niche factor analyses (ENFA). All the maps were then overlaid, in order
to identify potential species’ hotspots for different species groups of the 55 focal species (e.g., birds, fungi, red-listed
species). We found that hotspots for various species groups did not correspond. Our results indicate that an approach based
on “richness hotspots” may fail to conserve specific species groups. We hence recommend defining a biodiversity conservation
strategy prior to implementing conservation/restoration efforts in specific regions. The conservation priority setting of
the five biogeographical regions in Switzerland, however, did not differ when different hotspot definitions were applied.
This observation emphasizes that the chosen method is robust. Since the ENFA needs only presence data, this species prediction
method seems to be useful for any situation where the species distribution is poorly known and/or absence data are lacking.
In order to identify priorities for either conservation or restoration efforts, we recommend a method based on presence data
only, because absence data may reflect factors unrelated to species presence. 相似文献
714.
恐怖袭击事件通常会造成严重的人员伤亡、财产损失和社会影响,针对在不同场景下发生恐怖袭击所造成的后果进行预测是目前应对恐怖袭击事件急需解决的问题之一。利用多源数据,首先基于随机森林算法对恐怖袭击事件是否造成死伤进行分类预测,进而基于岭回归算法预测事件造成的具体死伤人数。研究结果表明:随机森林在测试集上对有死伤事件的召回率达到0.85,岭回归预测死亡和受伤人数的平均绝对误差分别小于1人和2人。研究结果可为反恐资源配置优化、预防恐怖袭击事件和减少其造成的损害提供辅助决策支持。 相似文献
716.
本文创造性地提出了国有林场“三工”合同管理的新模式,走法制化的道路,首先必须理顺国有林场与“三工”与“三工”组织的劳动关系,依照《劳动法》与《合同法》,分清各自的权利和义务,然后逐步由“三工”组织劳动合同向经济承揽合同过渡,依法解决合同管理中存在的问题。 相似文献
717.
利用美国陆地资源卫星TM5遥感信息,调查分析了鞍山市森林资源现状。结果表明,鞍山市共有森林资源466933.52hm^2,占全市土地面积的50.32%,其中灌木林占森林面积的81.11%。在此基础上,分析了存在的主要问题,并提出了恢复途径及生态建设模式。 相似文献
718.
Magdalena Gucia Grażyna Jarzyńska Anna K. Kojta Jerzy Falandysz 《Journal of environmental science and health. Part. B》2013,48(2):81-88
Mature specimens of Parasol Mushroom were collected annually in the outskirts of the Siemiany (2000–2003) and Rafa (2001–2003) sites in the northern part of Poland to examine temporal variations and similarities in the composition of 20 chemical elements. Analysis was done under the same condition and using well-validated analytical methods. Elements were determined by inductively coupled plasma–atomic emission spectroscopy and cold vapour–atomic absorption spectroscopy (Hg). The ranges of Ag, Al, Ba, Ca, Cd, Co, Cu, Cr, Fe, Hg, K, Mg, Mn, Na, Ni, P, Pb, Rb, Sr and Zn concentrations in the caps of fruiting bodies were similar (p > 0.05; Mann-Whitney U test) for both geographically distant sites, and these specimens from Rafa were more contaminated with Pb (p < 0.05; Mann-Whitney U test). The annual collections of caps in the Siemiany site varied in Ag, Al, Ba, Ca, Cd, Co, Cu, Fe, Hg, Na, Rb and Sr and contents (0.05 < p < 0.001), while they were similar in Cr, K, Mg, Mn, Ni, P, Pb and Zn (p > 0.05; Mann-Whitney U test). The annual collections of specimens from the Rafa site varied in contents of Ag, Al, Ba, Ca, Fe, Hg, K, Mg, Mn, P, Rb and Zn (p > 0.05), while they were similar in Cd, Co, Cr, Cu, Na, Ni, Pb and Sr (p < 0.05). The results of this study imply that metallic elements content of Parasol Mushroom collected at the same undisrupted sites, and hence keeping the same geochemical condition for mushroom development and fructification (the same stands and probably the same mycelia), can fluctuate over the years or the life-span of mycelium. Hence, when assessing the nutritional value of essential metallic elements and status of non-essential or toxic metallic elements in Parasol's Mushroom caps (and probably also of other mushrooms species) to man, the possible fluctuation in contents over time have to be taken into account. 相似文献
719.
The study focuses on understorey-overstorey plant community dynamics in a dry tropical forest to facilitate appropriate management decisions. We compare community composition and species diversity of the understorey vegetation among five dry tropical forest sites in northern India. A total of 1500 quadrats distributed over 15 one-ha permanent plots in five sites differing in the degree of disturbance, were used to enumerate the understorey tree species and the results were compared with overstorey tree layer. The non-metric multidimensional scaling (NMS) ordination revealed that human disturbance intensity, as well as the overall disturbance regimes, and soil water holding capacity controlled the organisation of dry tropical forest understorey composition through effects on soil organic matter. The alpha-diversity and its components decreased with increasing human disturbance intensity, reflecting utilisation pressure and decreased soil fertility, as also revealed by the analysis of overstorey tree layer. There was a significant positive relationship between overstorey and understorey diversity. Results suggest that in the future, the existing understorey tree communities may replace the current dry tropical forest communities under prevailing environmental conditions. The study also asserts that the rate of species accumulation will be greater in more disturbed sites as well as at small spatial scale within each disturbance level. 相似文献
720.
Seth Payton Greg Lindsey Jeff Wilson John R. Ottensmann Joyce Man 《Journal of Environmental Planning and Management》2008,51(6):717-736
This paper measures the benefits of the urban forest by examining its effect on housing prices. A Geographic Information System is used to develop a measure of the urban forest, the Normalised Difference Vegetation Index, from satellite imagery and to construct other variables from a variety of sources. Spatial hedonic housing price models for the Indianapolis/Marion County area are estimated. The models indicate that greener vegetation around a property has a positive, significant effect on housing price, holding everything else constant. This effect is dominated by measures at the neighborhood level. These findings indicate that property owners value the urban forest, at least in part, by the premium they pay to live in neighborhoods with greener, denser vegetation. These findings also indicate that public action to maintain and enhance the urban forest may be warranted. Planners and urban foresters can use these findings to inform public and policy debates over urban forestry programs and proposals. 相似文献