全文获取类型
收费全文 | 1824篇 |
免费 | 122篇 |
国内免费 | 427篇 |
专业分类
安全科学 | 41篇 |
废物处理 | 13篇 |
环保管理 | 455篇 |
综合类 | 1075篇 |
基础理论 | 299篇 |
污染及防治 | 130篇 |
评价与监测 | 157篇 |
社会与环境 | 150篇 |
灾害及防治 | 53篇 |
出版年
2024年 | 6篇 |
2023年 | 29篇 |
2022年 | 45篇 |
2021年 | 64篇 |
2020年 | 54篇 |
2019年 | 52篇 |
2018年 | 58篇 |
2017年 | 55篇 |
2016年 | 98篇 |
2015年 | 107篇 |
2014年 | 83篇 |
2013年 | 119篇 |
2012年 | 124篇 |
2011年 | 161篇 |
2010年 | 118篇 |
2009年 | 146篇 |
2008年 | 91篇 |
2007年 | 130篇 |
2006年 | 136篇 |
2005年 | 104篇 |
2004年 | 76篇 |
2003年 | 68篇 |
2002年 | 59篇 |
2001年 | 42篇 |
2000年 | 52篇 |
1999年 | 32篇 |
1998年 | 29篇 |
1997年 | 18篇 |
1996年 | 20篇 |
1995年 | 24篇 |
1994年 | 15篇 |
1993年 | 20篇 |
1992年 | 20篇 |
1991年 | 14篇 |
1990年 | 14篇 |
1989年 | 6篇 |
1988年 | 14篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 9篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1975年 | 3篇 |
1972年 | 6篇 |
1971年 | 3篇 |
排序方式: 共有2373条查询结果,搜索用时 78 毫秒
101.
The increasing pace and scale of landscape changes involve objective measurements in order to estimate the effects of changes on people's landscape preferences in a meaningful way. In the literature, some attempts have been made to provide a more conceptual base related to landscape preferences. These concepts and their indicators need to be tested empirically in different contexts and landscape types. In the present study, different items related to theoretical concepts of both aesthetic preference and cognitive rating were examined. They were combined in an in situ questionnaire, which was conducted among undergraduate students in geography during two different field excursions. Stimuli consisted of 11 landscape vistas selected during the excursions. All vistas represent rather rural landscapes but they vary with regard to relief, degree of urbanisation, and degree of agricultural land use. Statistical analysis of all data yielded significant correlations between aesthetic and cognitive ratings. However, these correlations did not appear to be very strong. When considering landscape vistas separately, the relations between all cognitive ratings seemed to vary. Further, not all cognitive aspects had an equal predicting value for aesthetic preference. Moreover, this predicting value appeared to vary between different landscape vistas. The groups of interrelated cognitive aspects could not be associated consistently with theoretical concepts. The results demonstrated the inconsistencies existing between the contents of the theoretical concepts and the indicators found within the landscape. The findings argued for the necessity to distinguish between different ratings and landscape types instead of using unitary preference measures and generalized data when studying landscape preference. 相似文献
102.
伊犁河伊宁市段水质污染特征分析 总被引:3,自引:1,他引:2
在对伊犁河伊宁市段历年水质状况进行综合评价的基础上,探讨了城市河段水质的变化规律、污染特征和成因。 相似文献
103.
Surface runoff is one of the most important pathways for pesticides to enter surface waters. Mathematical models are employed to characterize its spatio-temporal variability within landscapes, but they must be simple owing to the limited availability and low resolution of data at this scale. This study aimed to validate a simplified spatially-explicit model that is developed for the regional scale to calculate the runoff potential (RP). The RP is a generic indicator of the magnitude of pesticide inputs into streams via runoff. The underlying runoff model considers key environmental factors affecting runoff (precipitation, topography, land use, and soil characteristics), but predicts losses of a generic substance instead of any one pesticide. We predicted and evaluated RP for 20 small streams. RP input data were extracted from governmental databases. Pesticide measurements from a triennial study were used for validation. Measured pesticide concentrations were standardized by the applied mass per catchment and the water solubility of the relevant compounds. The maximum standardized concentration per site and year (runoff loss, RLoss) provided a generalized measure of observed pesticide inputs into the streams. Average RP explained 75% (p < 0.001) of the variance in RLoss. Our results imply that the generic indicator can give an adequate estimate of runoff inputs into small streams, wherever data of similar resolution are available. Therefore, we suggest RP for a first quick and cost-effective location of potential runoff hot spots at the landscape level. 相似文献
104.
关于“四沿”化工安全的战略性思考与探索 总被引:3,自引:1,他引:2
以基本能浓缩中国化工概貌的江苏省沿江、沿河、沿湖、沿海化工企业为背景,依据其形成和发展及基本概况,结合重大化工事故灾难,以安全与环境相耦合,对"四沿"化工安全进行了战略性思考,试图勾画临水化工本质安全的模型,提出在"四沿"地区构建化工本质安全化科技支撑体系的宏观构架,即建设"江苏省四沿区域化工本质安全和化工事故防范及应急系统"的思路、探索与实践。还提出了立法深化研究和技术标准制定、严格区域规划设计与建设的监督、强化监管执法力度等急需关注的问题。以江苏省"四沿"区域的化工安全为背景所提出的思路与对策,应该对整个华东地区乃至全国临水性化工企业安全具有重要的现实和借鉴意义,对我国高危行业的安全生产和环境保护有重大的示范效应。 相似文献
105.
The measurement of the bed shear stress along vegetated river beds is essential for accurately predicting the water level, velocity and solute and sediment transport fluxes in computational hydroenvironmental models. Details are given herein of an experimental and theoretical study to determine the bed boundary shear stress along vegetated river beds introducing a novel field measuring method, namely the FliessWasserStammtisch (FST)-hemispheres. Although investigations have been conducted previously for sedimentary channels using the FST-hemispheres, this preliminary study is thought to be the first time that such hemispheres have been used to investigate the bed shear stresses in vegetated channels. FST-hemispheres were first developed by Statzner and Müller [1989. Standard hemispheres as indicators of flow characteristics in lotic benthos research. Freshwater Biology 21, 445-459] to act as an integrated indicator of the gross hydrodynamic stresses present near the bed. Test and validation data were found to be at least of the same order of magnitude for the stresses predicted from literature for sedimentary channels, with this study establishing the commencement of a database of calibrated FST-hemisphere laboratory data for vegetated channel beds. In a series of experiments, depths ranging from 0.1 to 0.28m were considered, equating directly to comparable conditions in small rivers or streams. The results of this study provide a basis for enabling the FST-hemispheres to be used to evaluate the boundary shear stress for a wider range of applications in the future, including vegetated river beds. 相似文献
106.
This article develops a methodology aimed at generating a systematic social diagnosis of social and natural landscapes. The analytical process is divided into six easily replicable and causatively connected steps. The goal is two-fold: first, to present the inextricable connections between physical landscapes and the communities that occupy them. And second, to provide a fundamental tool to public policy designers that should simultaneously improve social acceptability of conservation policies and policy efficiency and effectiveness. Finally, this methodology is consciously heterogeneous from a theoretical perspective. This article puts together, in fruitful dialogue, contributions from varying places on the social theory spectrum: from political economy to poststructural theory. 相似文献
107.
The provision of green space is increasingly being perceived as an important factor for quality of life. However, green spaces often face high developmental pressure. The main objective of this study is to investigate a prospective approach to green space planning by combining three-dimensional (3D) visualization of green space scenarios and survey techniques to facilitate improved participation of the public. Aside from the ‘Status quo’, scenarios ‘Agriculture’, ‘Recreation’, ‘Nature conservation’ and ‘Wind turbines’ are visualized in three dimensions. In order to test responses, a survey was conducted both in print format and on the Internet. Overall, 49 different visualizations that belong to one of the scenarios were available in the survey and were rated according to the perceived esthetic, recreational and ecological values.The highest rated scenes include vegetation elements such as meadows with orchards, single trees, shrubs or forest. The least attractive scenes are those where buildings are highly dominant or where there are no vegetation elements.Based on the ratings for the individual images and on the corresponding scenarios, our study shows that there is high potential for improving the existing landscape. All suggested changes are either rated about equal to or considerably higher than the status quo, with the scenario ‘Nature conservation’ receiving the highest scores. 相似文献
108.
The authors present the beginnings of a planning support system (PSS) for agri-environmental measures exemplified by a virtual implementation of Colorfields and blooming strips on model farms, based on real-world data. This paper starts with an introduction to the Colorfields, a concept for transdisciplinary and sustainable landscape design of set-aside land. Colorfields comprise of blooming strips of flowering annual or biennial plants, which are designed and drilled in pattern on fallow land creating Land Art. The temporary scenic arrangements of the Colorfields combine the advantages of ecological strips, e.g. providing habitats for insects (especially bees), improving soil fertility through the cultivation of intercrops, with improvements of the social recognition of farmers as producers of pleasant landscapes instead of monoculture fields.The prototype of the PSS uses two software tools of different scientific origin, the bio-economic modeling system MODAM and the landscape visualization system Lenné3D, which are linked based on geo-data. The resulting system helps to assess the economic effects and visualizes the effects of the specific landuse patterns under different scenarios.The economic assessment of blooming strips on arable land and of one Colorfield on fallow land shows that these measures prove to be profitable from an economic viewpoint assuming the current area payments for the obligatory European Union set-aside program. Furthermore, the visualizations enable the design to be tested virtually by exploring the resultant scenery. They provide artists, planners and stakeholders including farmers with a tool to virtually wander through landscape scenarios supporting a collaborative design and a shared vision for the community.The results of the two model farms and previous case studies for Colorfields demonstrate how current policy conditions could be used for the improvement of environmental and scenic qualities. Furthermore, the ability of the tools, MODAM and Lenné3D, suggests to support and promote these activities. 相似文献
109.
黄河水体沉积物对敌百虫和甲拌磷的吸附 总被引:8,自引:0,他引:8
对敌百虫和甲拌磷在黄河水体沉积物中的吸附特性进行了研究,观察了pH值和离子强度等因素对吸附的影响.结果表明,敌百虫的吸附过程为一级动力学规律;敌百虫的吸附符合Langmuir等温式,甲拌磷的吸附可用Freundich等温式较好地描述.ph值降低或离子强度增加使敌百虫和甲拌磷在沉积物中的吸附程度明显减小.敌百虫在黄河水体沉积物中的吸附以表面吸附为主,而甲拌磷则表现为表面吸附和在有机碳中的分配作用两种吸附方式. 相似文献
110.