全文获取类型
收费全文 | 23985篇 |
免费 | 539篇 |
国内免费 | 5760篇 |
专业分类
安全科学 | 917篇 |
废物处理 | 1667篇 |
环保管理 | 2354篇 |
综合类 | 9030篇 |
基础理论 | 5544篇 |
环境理论 | 2篇 |
污染及防治 | 7278篇 |
评价与监测 | 1501篇 |
社会与环境 | 1375篇 |
灾害及防治 | 616篇 |
出版年
2024年 | 3篇 |
2023年 | 224篇 |
2022年 | 681篇 |
2021年 | 544篇 |
2020年 | 408篇 |
2019年 | 430篇 |
2018年 | 1905篇 |
2017年 | 1924篇 |
2016年 | 1924篇 |
2015年 | 1123篇 |
2014年 | 1173篇 |
2013年 | 1621篇 |
2012年 | 1704篇 |
2011年 | 2642篇 |
2010年 | 1619篇 |
2009年 | 1538篇 |
2008年 | 1879篇 |
2007年 | 2123篇 |
2006年 | 826篇 |
2005年 | 621篇 |
2004年 | 452篇 |
2003年 | 610篇 |
2002年 | 579篇 |
2001年 | 420篇 |
2000年 | 442篇 |
1999年 | 475篇 |
1998年 | 431篇 |
1997年 | 351篇 |
1996年 | 333篇 |
1995年 | 284篇 |
1994年 | 235篇 |
1993年 | 188篇 |
1992年 | 151篇 |
1991年 | 88篇 |
1990年 | 69篇 |
1989年 | 54篇 |
1988年 | 47篇 |
1987年 | 30篇 |
1986年 | 25篇 |
1985年 | 13篇 |
1984年 | 26篇 |
1983年 | 26篇 |
1982年 | 11篇 |
1981年 | 12篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1935年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 13 毫秒
991.
With globalization, virtual exchanges of natural resources embodied in traded commodities redistribute geographically land use and its environmental impacts. Benefits of national forest protection may be undermined at the global-scale by leakage through international trade. We studied land use displacement associated with national policies to protect forests in Bhutan. This case study provides a simple situation: a dominant forest cover almost unaffected by agricultural expansion, a rural economy dominated by the primary sector, centralized forest conservation policies, and a dominant trading partner. We assessed the net effects at the international level of the Bhutanese forest protection policies by accounting for trade in wood products with India. Our results show that these policies have been effective in maintaining a high forest cover, but have been accompanied by an increasing displacement of forest use to India. In 1996–2011, the difference between the total volume of wood imported from India and the total volume exported from Bhutan—i.e., the net displacement—corresponds to 27 % of the total volume consumed in Bhutan. In 2011, 68 % of the total forest area required to produce the wood consumed in Bhutan was located in India. The wood imported by Bhutan was likely originating from tree plantations in the northeastern Indian states. Since Bhutan has few tree plantations and very valuable natural forests, the net international-level ecological impacts of this land use displacement is arguably positive. Most of the wood imports of Bhutan were wood charcoal for its emerging chemical industries. This case of displacement reflects functional upgrading in the value-chain rather than an externalization of consumption-based environmental costs. Through its government policies, Bhutan has managed to support its economic development while protecting its forests and leapfrogging the negative impacts on forests generally associated with the early stages of modernization. 相似文献
992.
Md. Sarwar Hossain John A. Dearing M. M. Rahman M. Salehin 《Regional Environmental Change》2016,16(2):429-443
This study takes an historical approach in order to establish how the form and function of the social-ecological system that represents the Bangladesh south-western coastal zone has changed over recent decades. Time series data for a range of ecosystem services and drivers are analysed to define the range of trends, the presence of change points, slow and fast variables and the significant drivers of change. Since the 1980s, increasing gross domestic product and per capita income mirror rising levels of food and inland fish production. As a result, the size of population below the poverty line has reduced by ~17 %. In contrast, non-food ecosystem services such as water availability, water quality and land stability have deteriorated. Conversion of rice fields to shrimp farms is almost certainly a factor in increasing soil and surface water salinity. Most of the services experienced statistically significant change points between 1975 and 1980, and among the services, water availability, shrimp farming and maintenance of biodiversity appear to have passed tipping points. An environmental Kuznets curve analysis suggests that the point at which growing economic wealth feeds back into effective environmental protection has not yet been reached for water resources. Trends in indicators of ecosystem services and human well-being point to widespread non-stationary dynamics governed by slowly changing variables with an increased likelihood of systemic threshold changes/tipping points in the near future. The results will feed into simulation models and strategies that can define alternative and sustainable paths for land management. 相似文献
993.
Viacheslav I. Kharuk Mariya L. Dvinskaya Ilya A. Petrov Sergei T. Im Kenneth J. Ranson 《Regional Environmental Change》2016,16(8):2389-2397
Fire history within the northern larch forests of Central Siberia was studied (65 + °N). Fires within this area are predominantly caused by lightning strikes rather than human activity. Mean fire return intervals (FRIs) were found to be 112 ± 49 years (based on firescars) and 106 ± 36 years (based on firescars and tree natality dates). FRIs were increased with latitude increase and observed to be about 80 years at 64°N, about 200 years near the Arctic Circle and about 300 years nearby the northern range limit of larch stands (~71° + N). Northward FRIs increase correlated with incoming solar radiation (r = ?0.95). Post-Little Ice Age (LIA) warming (after 1850) caused approximately a doubling of fire events (in comparison with a similar period during LIA). The data obtained support a hypothesis of climate-induced fire frequency increase. 相似文献
994.
Hoang Huu Nguyen Paul Dargusch Patrick Moss Da Binh Tran 《Regional Environmental Change》2016,16(8):2303-2315
This paper examines the anthropogenic factors that have contributed to wetland loss and degradation in the Mekong Delta, Vietnam from 1816 AD to present. Our analysis is framed over five historical periods and highlights the role that seven drivers of wetland degradation have played in the Mekong Delta, including: resettlement and economic development policies; population growth and urbanization; demand for food and reclaiming wetland for agriculture; construction of canals construction of dykes flood protection systems; expansion of travel systems (waterway and roads); and exploitation of wetland natural resources. Of these, government policies for resettlement and economic development seem to have had the greatest impact on wetland loss and degradation in the Mekong Delta throughout the course of history. As a result of these factors, only 0.068 million hectares of the original 4.0 million hectares of the Mekong Delta currently remains as primary swamp forest ecosystem. History suggests that future management of the Mekong Delta should take a holistic approach that includes a better understanding of the implications of past decisions on wetland loss. 相似文献
995.
Antoine Sambou Ida Theilade Rasmus Fensholt Anders Ræbild 《Regional Environmental Change》2016,16(6):1765-1777
Several studies have documented that vegetation in the Sahel is highly dynamic and is affected by the prevailing climatic conditions, as well as by human use of the areas. However, little is known about vegetation dynamics in the large saline areas bordering the rivers of West Africa. Combining satellite imagery, the perception of local people and botanical information, this study investigated the vegetation dynamics and the drivers of vegetation changes in Fatick Province, Senegal. Satellite images showed a change in vegetation composition, i.e., a loss of tree cover and an increase in shrub cover, herbaceous cover and tans (highly saline areas with sparse vegetation). Although the trend was the same, the three villages had different vegetation histories. A survey of the woody vegetation showed that shrubs and young trees were dominating with relatively few large trees. Local people perceived a general decline of woody plants from 1993 to 2013. Among 60 species mentioned by local people, 90 % were declining and 10 % increasing. Together the three methods documented a decrease in density and diversity of the woody vegetation, mainly influenced by salinity and land use. The large numbers of young trees indicate a potential for regeneration of some, but not all, tree species. As many tree species appreciated by local people were reported to be declining, local communities have experienced a reduction of their natural resources. Based on villagers’ recommendations for improved vegetation management, we discuss possible contributions including reforestation, desalinization and environmental protection for restoration of the vegetation. 相似文献
996.
Karl S. Zimmerer 《Regional Environmental Change》2016,16(8):2199-2214
Our research addresses the gap in scientific research on the fine-grain spatial patterns and social–ecological interactions of land use and agrobiodiversity. The spatial dimension of agrobiodiversity dynamics potentially strengthens the social–ecological resilience and food security of smallholders by buffering risk and vulnerability. Our research integrates the scientific theories, concepts, and methods of spatial externalities, social–ecological interactions, geospatial land and global change sciences, and political ecology. We designed a case study of the Arbieto-Tarata landscape in the Bolivian Andes that comprises a globally significant agrobiodiversity hot spot of Andean maize. The Arbieto-Tarata landscape, which contains nearly 8000 fields at 2500–2800 masl, is representative of mixed-use smallholder agri-food systems amid global changes. Our research predicts spatial spillover and edge effects of combined social and environmental factors leading to the clustering of same-crop fields. Findings reveal significant levels of the predicted clustering between 2006 and 2012. The degree of this clustering is found to differ among geographic and environmental sub-areas reflecting fine-grain variation of local causal linkages. Extra-local causal linkages include high levels of migration, water resource shortages, and urbanization. Results show the influences of informal and formal coordination in the spatial clustering of same-crop fields. This field-level coordination improves the efficiency of resource allocations and lowers costs of production. It enables the viability of high-agrobiodiversity Andean maize in smallholder land use and agri-food systems amid global changes. The article discusses the broader policy and scientific implications of these findings including scaling up and support of the social–ecological resilience of agrobiodiversity globally. 相似文献
997.
John N. Kittinger Trisann M. Bambico Dwayne Minton Alyssa Miller Manuel Mejia Nahaku Kalei Bradley Wong Edward W. Glazier 《Regional Environmental Change》2016,16(2):301-313
Environmental restoration projects are commonly touted for their ecological positives, but such projects can also provide significant socioeconomic and cultural benefits to local communities. We assessed the social dimensions of a large-scale coral reef restoration project in Maunalua Bay, O‘ahu, where >1.32 million kg of invasive marine macroalgae was removed from 11 hectares (90,000 m2; 23 acres) of impacted coral reef in an urbanized setting. We interviewed 131 community stakeholders and analyzed both quantitative and qualitative data to assess human uses of the environment, assess perceptions of environmental health, and characterize social dimensions (+/?) associated with the invasive algae removal effort. Results indicate substantial direct economic benefits, including the creation of more than 60+ jobs, benefiting more than 250 individuals and 81 households. The project helped develop a skilled workforce in a local business dedicated to environmental restoration and increased the capacity of community organizations to address other threats to reefs and watersheds. Other major benefits include revitalization of Native Hawaiian cultural practices and traditions and the successful use of harvested invasive algae as compost by local farmers. Our results show the project heightened community awareness and a broader sense of stewardship in the area, creating enabling conditions for collective community action. Our findings show that restoration projects that explicitly incorporate efforts to build community awareness, involvement, and a shared responsibility for a site may ultimately create the long-term capacity for sustainable stewardship programs. We conclude by discussing lessons learned for engaging productively with communities in environmental restoration and stewardship, which remains a central focus in conservation worldwide. 相似文献
998.
Trishna Dutta Sandeep Sharma Brad H. McRae Parth Sarathi Roy Ruth DeFries 《Regional Environmental Change》2016,16(1):53-67
Large connected landscapes are paramount to maintain top predator populations. Across their range, tiger (Panthera tigris) populations occur in small fragmented patches of habitat, often isolated by large distances in human-dominated landscapes. We assessed connectivity between 16 protected areas (PAs) in central India, a global priority landscape for tiger conservation, using data on land use and land cover, human population density, and transportation infrastructure. We identified and prioritized movement routes using a combination of least-cost corridor modeling and circuit theory. Our analyses suggest that there are several opportunities to maintain connectivity in this landscape. We mapped a total of thirty-five linkages in the region and calculated metrics to estimate their quality and importance. The highest quality linkages as measured by the ratio of cost-weighted distance to Euclidean distance are Kanha–Phen/Bandhavgarh–SanjayGhasidas/Melghat–Satpura, and cost-weighted distance to least-cost path length are Nawegaon–Tadoba/Achanakmar–SanjayGhasidas/Kanha–Phen. We used current flow centrality to evaluate the contribution of each PA and linkage toward facilitating animal movement. Values are highest for Kanha and Pench tiger reserves, and the linkages between Kanha–Phen, Kanha–Pench, and Pench–Satpura, suggesting that these PAs and linkages play a critical role in maintaining connectivity in central India. In addition, smaller areas such as Bor, Nawegaon, and Phen have high centrality scores relative to their areas and thus may act as important stepping stones. We mapped pinch points, which are sections of the linkages where tiger movement is restricted due to unfavorable habitat, transportation networks, human habitation, or a combination of factors. Currently, very limited data exist on tiger movement outside of PAs to validate model results. Regional-scale connectivity mapping efforts can assist managers and policy makers to develop strategic plans for balancing wildlife conservation and other land uses in the landscape. 相似文献
999.
1000.
Zhen Wang Xindong Ma Guangshui Na Zhongsheng Lin Qian Ding Ziwei Yao 《Environmental pollution (Barking, Essex : 1987)》2009,157(11):3132-3136
Concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) in soil, moss and reindeer dung collected at Ny-Ålesund of the Arctic were measured to investigate their accumulation trends and distribution in the three compartments. Compared with the other regions, the proportions of 2 + 3 ring PAHs to the total PAHs were higher, whereas the proportions of 5 + 6 ring PAHs were lower in the three compartments at Ny-Ålesund. Significant log/log-linear relationship was observed between the sub-cooled liquid vapor pressure and the soil/moss quotient (QSM). The relation was similar to the relationship between the gas/particle partition coefficient (KP) and of PAHs, implying QSM would be a “mirror image” of KP. Excellent log/log-linear relationships were observed between QSM and KOA as well as between the moss/dung quotient (QMD) and KOW. The results presented here indicate the physicochemical properties are suitable for characterizing the distribution of PAHs in soil, moss and reindeer dung. 相似文献