首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   9667篇
  免费   3篇
安全科学   3篇
废物处理   765篇
环保管理   1214篇
综合类   943篇
基础理论   3115篇
污染及防治   1730篇
评价与监测   1004篇
社会与环境   896篇
  2023年   1篇
  2022年   3篇
  2021年   4篇
  2019年   2篇
  2018年   1477篇
  2017年   1374篇
  2016年   1196篇
  2015年   128篇
  2014年   16篇
  2013年   9篇
  2012年   460篇
  2011年   1338篇
  2010年   690篇
  2009年   597篇
  2008年   877篇
  2007年   1226篇
  2006年   3篇
  2005年   19篇
  2004年   33篇
  2003年   61篇
  2002年   97篇
  2001年   15篇
  2000年   10篇
  1999年   3篇
  1998年   10篇
  1984年   11篇
  1983年   8篇
  1935年   2篇
排序方式: 共有9670条查询结果,搜索用时 0 毫秒
971.
Making Capacity Building Meaningful: A Framework for Strategic Action   总被引:1,自引:0,他引:1  
This paper aims to give practical meaning to ‘capacity building’ through (a) identifying a suite of practical measures, such as mentoring or best practice guidelines, that have been shown to or are considered to build human, social, institutional, and economic capital; (b) placing these measures within a broader systems framework; and (c) exploring stakeholder feedback on specific measures to inform framework implementation. The 29 measures described provide actors, whether government or nongovernment, with a suite of practical investment choices for building capacity. These measures are then clustered into eight groups according to their primary purpose and placed within a systems framework. The framework provides a tool for actors with responsibilities for or an interest in capacity building to inform more holistic and strategic targeting of effort and investment. Stakeholder feedback gathered through surveys and workshops is subsequently reported to further inform implementation of specific measures within the framework’s eight groupings. The framework presented may be built upon through the identification and inclusion of further capacity building measures. The research is conducted within the context of decentralized governance arrangements for natural resource management (NRM), with specific focus on Australia’s recently formalized 56 NRM regions and their community-based governing boards as an informative arena of learning. Application of the framework is explored in the Australian setting through the identification and comparison of measures supported and most preferred by four major stakeholder groups, namely board members, regional NRM organization staff, policy/research interests, and Indigenous interests. The research also examines stakeholder perceptions of capacity issues, and whether these issues are likely to be addressed through implementing their preferred measures.
Lisa RobinsEmail:
  相似文献   
972.
The National Park Service (NPS) is increasingly focusing on alternative transportation systems in national parks to address environmental and social problems arising from a historical reliance on personal automobiles as the primary means of visitor access. Despite the potential advantages, alternative transportation may require a reorientation in the way that Americans have experienced national parks since the advent of auto-tourism in the early twentieth century. Little research exists, however, on visitor perspectives towards alternative transportation or the rationale underlying their perspectives. It remains unclear how transportation systems affect visitors’ experiences of the park landscape or the factors influencing their travel behavior in the parks. This report presents an interpretive study of visitor perspectives toward transportation management in the Yosemite Valley area of Yosemite National Park, California. Qualitative analysis of 160 semi-structured interviews identified individual psychological factors as well as situational influences that affect visitors’ behavior and perspectives. Individual psychological factors include perceived freedom, environmental values and beliefs, prior experience with Yosemite National Park and other national parks, prior experience with alternative transportation in national parks, and sensitivity to subjective perceptions of crowding. Situational factors included convenience, access, and flexibility of travel modes, as well as type of visit, type of group, and park use level. Interpretive communication designed to encourage voluntary visitor use of alternative transportation should focus on these psychological and situational factors. Although challenges remain, the results of this study suggest approaches for shaping the way Americans visit and experience their national parks to encourage environmental sustainability.  相似文献   
973.
The Patagonian coast is considered a relatively pristine environment. However, studies conducted along coastal Patagonia have showed hydrocarbon pollution mostly concentrated at ports that have fishing, oil loading, general merchant, and/or tourist activities. A high value of total aliphatic hydrocarbons (TAH) was found at the Rawson fishing port (741 μg/g dw). In other ports with and without petroleum-related activities, hydrocarbon values were approximately 100 μg/g dw. The highest values for TAH and total aromatic hydrocarbons (TArH) were found in Faro Aristizábal, north of San Jorge gulf (1304 and 737 μg/g dw, respectively). This is very likely the result of petroleum-related activities at the Comodoro Rivadavia, Caleta Cordova, and Caleta Olivia ports located within this gulf. In other coastal areas away from potential anthropogenic sources, hydrocarbon values were less than 2 and 3 μg/g dw for TAH and TArH, respectively. This review of published and unpublished information suggests that ports are important oil pollution sources in the Patagonian coast. More detailed studies are needed to evaluate the area affected by port activities, to understand the mechanisms of hydrocarbon distribution in surrounding environments, and to assess bioaccumulation in marine organisms. Despite that some regulations exist to control oil pollution derived from port and docked vessel activities, new and stricter management guidelines should be implemented.  相似文献   
974.
This study presents an integrated analysis of the evolution of the marine environment and the human uses in Cape Creus, a Mediterranean coastal area where intense commercial fisheries and recreational uses have coexisted over the last fifty years. The investigation synthesizes the documented impacts of human activities on the marine environment of Cap de Creus and integrates them with new data. In particular, the evolution of vulnerable, exploited species is used to evaluate the fishing impacts. The effects of area protection through the establishment of a marine reserve in the late 1990s and the potential climate change impacts are also considered. The evolution of the human uses is marked by the increasing socioeconomic importance of recreational activities (which affect species and habitats) in detriment to artisanal and red coral fisheries (which principally affect at a species level). Overall, populations of sedentary, vulnerable exploited species, hard sessile benthic invertebrates, and ecologically fragile habitats, such as seagrass meadows, the coralligenous and infralittoral algal assemblages have been the most negatively impacted by anthropogenic activities. Albeit human uses currently constitute the largest negative impact on the marine environment of Cap de Creus, climate change is emerging as a key factor that could have considerable implications for the marine environment and tourism activities. The establishment of the marine reserve appears to have had little socioeconomic impact, but there is some evidence that it had some positive biological effects on sedentary, littoral fishes. Results demonstrate that the declaration of a marine reserve alone does not guarantee the sustainability of marine resources and habitats but should be accompanied with an integrated coastal management plan.  相似文献   
975.
Whereas past research has treated co-management of common pool resources as if villagers and project implementing authorities were the only relevant actors, numerous external factors beyond the control of these two partners create barriers to successful co-management. This paper draws on discussions with Forest Department officials to examine the influence of these forces on the outcomes of Joint Forest Management (JFM) in Tamil Nadu, India. An empirical inquiry into the operational aspects of JFM indicates the important roles of political parties, powerful people, and other state institutions and functionaries as well as the flow of foreign funding. Further, the strong demand by local people for socio-economic development interventions as opposed to improvement of degraded forests belittles the role of the Forest Department relative to other departments. Numerous other conditioning factors and relationships are explored. The authors call for reforms in public governance to allow better participation of all the actors involved for this participatory management approach to succeed and sustain.  相似文献   
976.
Ash produced from the combustion of livestock manure contains large amounts of phosphorus (P), which is an important resource as a fertilizer. Some studies have extracted and recovered P from incinerated biomass ash using inorganic acid or alkaline agents, which produce wastewater that requires treatment and is expensive due to the cost of chemicals. Livestock manure ash contains not only P, but also water soluble salts, which could be a negative influence on plant growth and shall be preferably removed from the recovered fertilizer. In this study, we removed salinity from cattle manure incineration ash by simple aqueous leaching, while retaining the P content. The optimal condition was a 20 min leaching time at a liquid/solid (L/S) ratio of 10 mL g-ash?1. Under this condition, over 90 % of Cl and 20 % of Na in the original ash was removed, while over 99 % of the P was retained in the leached residue. The leached residue met the fertilizer standard in Japan in terms of citrate soluble fertilizer components and contained few heavy metals. X-ray analyses of the ash indicated that Cl was mainly present as KCl in the original ash, while P was mainly present as Ca compounds in the ash.  相似文献   
977.
Poly(butylene succinate) (PBS) was melt blended with glycerol based polyesters (PGS) synthesized from pure and technical glycerol aiming to improve the impact strength of PBS. It was found that after addition of 30 wt% PGS to PBS its impact strength was significantly increased by 344% (from 31.9 to 110 J/m) and its elongation at break was maintained at 220%. Infrared spectra of the blends showed the presence of hydroxyl groups from the PGS phase suggesting that hydrogen bonding between the phases could be responsible for a good stress transfer and an efficient toughening in the PBS/PGS blends. Scanning electron microscopy imaging showed a good dispersion of PGS phase into PBS with a PGS particle size of 10 μm and less and no agglomeration. Addition of PGS to PBS was shown to be an effective strategy for improvement of PBS impact resistance without serious detrimental effects on its thermal and rheological properties.  相似文献   
978.
A total of 285 water samples were collected from 71 roof harvested rainwater tanks from four villages in different provinces over a two-year (2013–2014) period during the early (October to December) and late (January to March) rainy season. Water quality was evaluated based on Escherichia coli, faecal coliforms and Enterococcus spp. prevalence using the IDEXX Quanti-Tray quantification system. Real-Time PCR was used to analyse a subset of 168 samples for the presence of Shigella spp., Salmonella spp. and E. coli virulence genes (stx1, stx2 and eaeA). Escherichia coli were detected in 44.1% of the samples, Enterococcus spp. in 57.9% and faecal coliforms in 95.7%. The most prevalent E. coli concentrations in harvested rainwater were observed in 29.1% of samples and 22.5% for Enterococcus spp. and, were within 1–10 cfu/100 ml and 10–100 cfu/100 ml, respectively, whereas those for faecal coliforms (36.6%) were within 100–1000 cfu/100 ml. On average 16.8% of the samples had neither E. coli nor Enterococcus spp. detected, while 33.9% had only Enterococcus spp. and 23.7% had only E. coli. E. coli and Enterococcus spp. were detected together in 25.5% of the samples. Evaluation of samples for potential pathogenic bacteria showed all tested samples to be negative for the Shigella spp. ipaH gene, while five tested positive for Salmonella ipaB gene. None of the samples tested positive for the stx1 and stx2 genes, and only two tested positive for the eaeA gene. These findings are potentially useful in the development of a simplified risk assessment strategy based on the concentrations of indicator bacteria.  相似文献   
979.
The objective of the present work was to study the preparation of a novel bio-based product from gelatin (GT) and natural rubber (NR) using potassium persulphate (KPS) as an initiator. The GT and NR composites (GT/NR composites) containing KPS were formed in an aqueous latex solution. The chemical structure of the GT/NR composite was characterized by ATR-FTIR, and XRD. The highest tensile strength was observed in a 9/1 GT/NR composite and the elongation at break of this composite was improved by the addition of both NR and glycerol. In addition, the swelling ratio increased as a function of increasing GT content in the composite. The thermal stability of the GT was improved after the formation of the chemical interaction between the NR and GT helped by the KPS. The best ratio of the GT/NR composite was 3/7 GT/NR. This environmentally friendly composite easily decomposed in natural soil within 30 days. The novel biopolymer showed high mechanical properties, water resistance and was produced in an environmentally compatible process. The NR was able to improve some of the physical and mechanical properties of GT biofilms produced from the composite. Possible future applications of this composite are for medical materials, and the packaging and life extension of food products.  相似文献   
980.
Biodegradable and ecologically friendly polymer materials attract great attention of many scientific groups in the world as they fit well in the sustainable development policy and are considered to be “a right thing to do” by the general public. Such polymers can be modified by the addition of different fillers, favorably of natural origin. In the paper we provide a comparison between composites based on two biodegradable polymers: poly(lactic acid)—biodegradable, natural stock polymer and poly(butylene succinate)—biodegradable polymer produced from fossil based materials. For each polymer we have prepared a series of composites with different fibres (natural: hemp and flax, and manmade: Cordenka) and different filler loadings. To fully characterize obtained materials thermal, mechanical and surface free energy measurements were performed, completed with morphology observations and an attempt to compare the experimental data for tensile measurements with values obtained using the modified rule of mixtures. The tensile results calculated using the modified rule of mixture for below 30% fibre loading are found to be fitting the experimental data. Composites mechanical properties and morphology were strongly affected by the type of fibre used and its loading, however thermal properties remained almost unchanged. In specific, Cordenka fibres tend to form bunches which presence greatly influences the mechanical properties but still our studies have shown clear advantage of manmade Cordenka fibres over the hemp and flax fibres when considering distribution and fibre–polymer interaction.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号