全文获取类型
收费全文 | 4056篇 |
免费 | 69篇 |
国内免费 | 41篇 |
专业分类
安全科学 | 187篇 |
废物处理 | 155篇 |
环保管理 | 706篇 |
综合类 | 688篇 |
基础理论 | 932篇 |
环境理论 | 3篇 |
污染及防治 | 1020篇 |
评价与监测 | 240篇 |
社会与环境 | 189篇 |
灾害及防治 | 46篇 |
出版年
2023年 | 33篇 |
2022年 | 41篇 |
2021年 | 51篇 |
2020年 | 50篇 |
2019年 | 50篇 |
2018年 | 98篇 |
2017年 | 118篇 |
2016年 | 133篇 |
2015年 | 136篇 |
2014年 | 142篇 |
2013年 | 226篇 |
2012年 | 175篇 |
2011年 | 296篇 |
2010年 | 221篇 |
2009年 | 228篇 |
2008年 | 235篇 |
2007年 | 243篇 |
2006年 | 209篇 |
2005年 | 137篇 |
2004年 | 164篇 |
2003年 | 133篇 |
2002年 | 134篇 |
2001年 | 113篇 |
2000年 | 68篇 |
1999年 | 48篇 |
1998年 | 49篇 |
1997年 | 43篇 |
1996年 | 48篇 |
1995年 | 50篇 |
1994年 | 45篇 |
1993年 | 25篇 |
1992年 | 36篇 |
1991年 | 36篇 |
1990年 | 25篇 |
1989年 | 24篇 |
1988年 | 17篇 |
1987年 | 20篇 |
1986年 | 12篇 |
1985年 | 11篇 |
1984年 | 17篇 |
1983年 | 10篇 |
1982年 | 23篇 |
1981年 | 14篇 |
1980年 | 10篇 |
1979年 | 17篇 |
1970年 | 11篇 |
1969年 | 7篇 |
1967年 | 7篇 |
1965年 | 9篇 |
1960年 | 6篇 |
排序方式: 共有4166条查询结果,搜索用时 970 毫秒
431.
432.
433.
434.
435.
Sung Kim Chen Zhao Allan T. Bombard Charles Cantor Dirk van den Boom Cosmin Deciu 《黑龙江环境通报》2013,33(13):1310-1313
436.
M. Graziano Ceddia Mark Bartlett Charles Perrings 《Agriculture, ecosystems & environment》2009,129(1-3):65-72
The development of genetically modified (GM) crops has led the European Union (EU) to put forward the concept of ‘coexistence’ to give farmers the freedom to plant both conventional and GM varieties. Should a premium for non-GM varieties emerge in the market, ‘contamination’ by GM pollen would generate a negative externality to conventional growers. It is therefore important to assess the effect of different ‘policy variables’ on the magnitude of the externality to identify suitable policies to manage coexistence. In this paper, taking GM herbicide tolerant oilseed rape as a model crop, we start from the model developed in Ceddia et al. [Ceddia, M.G., Bartlett, M., Perrings, C., 2007. Landscape gene flow, coexistence and threshold effect: the case of genetically modified herbicide tolerant oilseed rape (Brassica napus). Ecol. Modell. 205, pp. 169–180] use a Monte Carlo experiment to generate data and then estimate the effect of the number of GM and conventional fields, width of buffer areas and the degree of spatial aggregation (i.e. the ‘policy variables’) on the magnitude of the externality at the landscape level. To represent realistic conditions in agricultural production, we assume that detection of GM material in conventional produce might occur at the field level (no grain mixing occurs) or at the silos level (where grain mixing from different fields in the landscape occurs). In the former case, the magnitude of the externality will depend on the number of conventional fields with average transgenic presence above a certain threshold. In the latter case, the magnitude of the externality will depend on whether the average transgenic presence across all conventional fields exceeds the threshold. In order to quantify the effect of the relevant ‘policy variables’, we compute the marginal effects and the elasticities. Our results show that when relying on marginal effects to assess the impact of the different ‘policy variables’, spatial aggregation is far more important when transgenic material is detected at field level, corroborating previous research. However, when elasticity is used, the effectiveness of spatial aggregation in reducing the externality is almost identical whether detection occurs at field level or at silos level. Our results show also that the area planted with GM is the most important ‘policy variable’ in affecting the externality to conventional growers and that buffer areas on conventional fields are more effective than those on GM fields. The implications of the results for the coexistence policies in the EU are discussed. 相似文献
437.
Helvi Heinonen-Tanski Mariëlle SNEL Christine van Wijk-Sijbesma Avizit Reaz Quazi Kochurani Mathew Induka Werellagama Mujibur Rahman S.M.A. Rashid Palitha Jayaweera Helen Judith 《Environment, Development and Sustainability》2007,9(4):355-368
Environmental quality for environmental health has been examined visually by describing general conditions and drinking water
supply, sanitation and solid waste treatment conditions and practices in six South-East Asian villages with a dense population.
The environmental review was supplemented by discussions with local people and political and administrative decision makers.
Some drinking water analyses were done in order to show the water quality to the local people. The quality of the general
conditions and the conditions and practices of drinking water supply, excreta disposal and solid waste treatment practices
have been graded with the grading system presented below. The grading could be done in 1 or 2 days in each area by two persons,
of which one was an environmental scientist and the other a social scientist, who also knew the local culture and worked as
a translator. 相似文献
438.
Mark E. Churchwell Robert L. Livingston Donald L. Sgontz Jerry D. Messman 《Environment international》1987,13(6)
The current U.S. Environmental Protection Agency (U.S. EPA) protocols for mercury determinations in aqueous and solid waste samples (SW-846 Methods 7470 and 7471) using recirculating cold-vapor atomic absorption spectrometry (CV-AAS) have been evaluated. The U.S. EPA methods are not sufficiently flexible to permit special quality control (QC) measures, have limited detectability for low-level mercury concentrations, and are plagued by spectral interferences caused by the nonspecific absorption of primary mercury radiation by volatile organic vapors. The U.S. EPA protocols have been modified in a single-laboratory study to facilitate additional QC measures, to enhance detectability for low-level mercury concentrations, and to eliminate nonspecific vapor absorption interferences. Volumetric manipulations for additional QC measures, if required, are facilitated by performing the sample digestions in Erlenmeyer flasks rather than in the current Biochemical Oxygen Demand (BOD) reduction-aeration bottles. Typical manipulations for additional QC measures that are now feasible include dilution of concentrated samples and multiple aliquot sampling for post-digestion spike and replicate analyses. Instrument detectability is improved 10-fold by using a gas sparging bottle as a dedicated reduction-aeration vessel and a silver wool-amalgamation CV-AAS system operated in an open configuration. The on-line amalgamation/thermal desorption process of the modified CV-AAS system eliminates interfering water and organic matrix vapors prior to the mercury absorption measurement. Good accuracy and precision have been obtained with the amalgamation CV-AAS system for the analyses of four reference sediment materials. The amalgamation CV-AAS measurements on the reference sediment digests have been successfully performed at absolute mercury concentration levels that are only 1 to 4 times above the instrumental detection limit of the U.S. EPA recirculating CV-AAS method. 相似文献
439.
This paper focuses on the diversity of engine technologies for low emission vehicles (LEVs) that are developed by car manufacturers in order to substitute for the conventional internal combustion engine vehicle (ICEV). Our purpose is to analyse the competition between the various technologies for LEVs as well as the innovative strategy of car manufacturers. We first propose to define and to represent these technological trajectories in order to compare their performances and to identify their strengths and weaknesses. The technological bottlenecks, the barriers to the adoption of these alternative engine technologies as well as the features of this technological competition are underlined. We then use a patent data analysis to study the patent portfolios of the main car manufacturers in these technologies over the period [1990–2005]. The dynamics of patent applications by car manufacturers gives insight on the competition among technologies and on the strategy of firms. This analysis emphasises the progressive diversification of firms' patent portfolios over the whole set of engine technologies and the differentiated strategic positioning of car manufacturers according to countries. 相似文献
440.