全文获取类型
收费全文 | 68篇 |
免费 | 0篇 |
专业分类
环保管理 | 11篇 |
综合类 | 27篇 |
基础理论 | 8篇 |
污染及防治 | 11篇 |
评价与监测 | 2篇 |
社会与环境 | 6篇 |
灾害及防治 | 3篇 |
出版年
2021年 | 1篇 |
2020年 | 1篇 |
2018年 | 5篇 |
2017年 | 1篇 |
2014年 | 3篇 |
2013年 | 3篇 |
2011年 | 6篇 |
2010年 | 1篇 |
2009年 | 3篇 |
2008年 | 3篇 |
2007年 | 5篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2002年 | 10篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1963年 | 1篇 |
1962年 | 1篇 |
1955年 | 1篇 |
1954年 | 1篇 |
1949年 | 1篇 |
1946年 | 1篇 |
1932年 | 1篇 |
1931年 | 1篇 |
1930年 | 3篇 |
1928年 | 1篇 |
1926年 | 3篇 |
1925年 | 1篇 |
1913年 | 1篇 |
排序方式: 共有68条查询结果,搜索用时 15 毫秒
41.
42.
43.
44.
Indices based on network theory are often used to describe food web functioning. These indices take as input food web flows that are estimated based on merging of (scarce) data with linear inverse methods (LIMs). Due to under sampling, most food webs are highly uncertain and can only be quantified within a specific uncertainty range. The linear inverse method (LIM) can estimate food web flows using a variety of techniques, e.g. the parsimonious or minimum norm (MN) solution, which selects one food web, based on a quadratic minimization technique or the Monte Carlo solution where a finitely many random solutions are generated which are then averaged. We use the Monte Carlo approach (MCA) to estimate the values of several indices from four published food webs, the Gulf of Riga for the autumn, summer and spring seasons, and the Takapoto atoll system. We first show that network indices are much better constrained than the uncertain food webs from which they are calculated. Therefore, even in the face of food web uncertainty, they are robust estimators of food web functioning. We then use the MCA-derived network indices to generate cumulative density functions for each index. These serve to compute the probabilities of the MN indices estimates being an extreme solution as compared to the median values. Our findings show that 82% of the MN solutions are smaller than the MCA solutions, and 63% of the network indices are significantly under-estimated. 相似文献
45.
Nahomi Isogai Jonathan N. Hogarh Nobuyasu Seike Yuso Kobara Femi Oyediran Mengnjo J. Wirmvem Samuel N. Ayonghe Julius Fobil Shigeki Masunaga 《Environmental science and pollution research international》2018,25(32):31828-31835
Most African countries have ratified the Stockholm Convention on persistent organic pollutants (POPs) and are expected to reduce emissions of POPs such as organochlorine pesticides (OCPs) to the atmosphere. Emerging evidence, however, suggests that there are contemporary sources of OCPs in African countries despite the global ban on these products. This study investigated the atmospheric contamination from OCPs in four West African countries—Togo, Benin, Nigeria, and Cameroon—to ascertain the emission levels of OCPs and the characteristic signatures of contamination. Polyurethane foam (PUF) disk passive air samplers (PAS) were deployed in each country for ca. 55 days in 2012 and analyzed for 25 OCPs. Hexachlorocyclohexanes (HCHs) and DDTs constituted the highest burden of atmospheric OCPs in the target countries, at average concentrations of 441 pg m?3 (range 23–2718) and 403 pg m?3 (range 91–1880), respectively. Mirex had the lowest concentration, ranged between 0.1 and 3.3 pg m?3. The concentration of OCPs in rainy season was higher than in dry season in Cameroon, and presupposed inputs from agriculture during the rainy season. The concentrations of ∑25 OCPs in each country were in the following order: Cameroon > Nigeria > Benin > Togo. There was significant evidence, based on chemical signatures of the contamination that DDT, aldrin, chlordane, and endosulfan were recently applied at certain sites in the respective countries. 相似文献
46.
Chia Poh Wai Lim Ban Soon Yong Fu Siong Julius Poh Seng-Chee Kan Su-Yin 《Environmental Chemistry Letters》2018,16(4):1493-1499
Environmental Chemistry Letters - Bisenols and its derivatives are attractive heterocyclic compounds exhibiting a wide range of biological properties, including anticancer, antipyretic and... 相似文献
47.
Ariane Zingiro Julius Juma Okello Paul Maina Guthiga 《Environment, Development and Sustainability》2014,16(6):1281-1298
Rainwater harvesting is increasingly viewed as a major strategy for enhancing agricultural productivity and boosting farm income in many drought-prone areas. While this technology is being promoted in many developing countries, there is conflicting evidence in the literature about its impact on welfare of farm households. This study uses propensity score matching and discrete choice regression techniques to assess the impact of rainwater harvesting ponds on farm household income and factors that influence adoption of such technologies in Rwanda. It finds that households with rainwater harvesting ponds have significantly higher income than their counterparts of comparable observable characteristics. It further finds evidence that increase in farm income occurs via increased input use and that household size, asset endowments and participation in farmer organizations condition adoption of rainwater harvesting ponds. The study concludes that adoption of rainwater harvesting technologies has positive benefits on farm households. It discusses the policy implications that adoption of rainwater harvesting ponds presents a pathway for reducing rural poverty. 相似文献
48.
49.
Nsajig wa E.Mbije Gregory M.Wagner Julius Francis Marcus C.Ohman Kajsa Garpe 《Ambio-人类环境杂志》2002,31(7):609-611
东非珊瑚礁的特点是它位于一个离散的动物地理学分区[1],具有经由赤道流接纳和重新分配偏远的种属物质的潜在重要性[2].尽管如此,该地区仍然是世界上研究最少的地区之一.例如,在坦桑尼亚,尽管珊瑚礁是众多的人赖以为生的重要自然资源,却没有受到应有的重视和研究[3~5].为数不多的研究定量分析过坦桑尼亚的珊瑚礁结构[6~13],而且大部分只是限于对一些礁砰进行基线研究. 相似文献
50.
Adoption and adaptation of natural resource management innovations in smallholder agriculture: reflections on key lessons and best practices 总被引:2,自引:0,他引:2
Bekele A. Shiferaw Julius Okello Ratna V. Reddy 《Environment, Development and Sustainability》2009,11(3):601-619
Many smallholder farmers in vulnerable areas continue to face complex challenges in adoption and adaptation of resource management
and conservation strategies. Although much has been learned from diverse experiences in sustainable resource management, there
is still inadequate understanding of the market, policy and institutional failures that shape and structure farmer incentives
and investment decisions. The policy and institutional failures exacerbate market failures, locking smallholder resource users
into a low level equilibrium that perpetuates poverty and land degradation. Improved market access that raises the returns
to land and labor is often the driving force for adoption of new practices in agriculture. Market linkages, access to credit
and availability of pro-poor options for beneficial conservation are critical factors in stimulating livelihood and sustainability-enhancing
investments. Future interventions need to promote joint innovations that ensure farmer experimentation and adaptation of new
technologies and careful consideration of market, policy and institutional factors that stimulate widespread smallholder investments.
Future projects should act as ‘toolboxes’, giving essential support to farmers to devise complementary solutions based on
available options. Addressing the externalities and institutional failures that prevent private and joint investments for
management of agricultural landscapes will require new kinds of institutional mechanisms for empowering communities through
local collective action that would ensure broad participation and equitable distributions of the gains from joint conservation
investments.
Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue. 相似文献