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   19109篇
  免费   2546篇
  国内免费   730篇
安全科学   606篇
废物处理   1285篇
环保管理   1919篇
综合类   5656篇
基础理论   4780篇
污染及防治   5182篇
评价与监测   1345篇
社会与环境   1257篇
灾害及防治   355篇
  2025年   15篇
  2024年   118篇
  2023年   281篇
  2022年   493篇
  2021年   398篇
  2020年   316篇
  2019年   329篇
  2018年   1742篇
  2017年   1731篇
  2016年   1665篇
  2015年   668篇
  2014年   679篇
  2013年   898篇
  2012年   1175篇
  2011年   2068篇
  2010年   1253篇
  2009年   1108篇
  2008年   1505篇
  2007年   1708篇
  2006年   492篇
  2005年   365篇
  2004年   305篇
  2003年   386篇
  2002年   398篇
  2001年   246篇
  2000年   285篇
  1999年   293篇
  1998年   240篇
  1997年   223篇
  1996年   192篇
  1995年   158篇
  1994年   117篇
  1993年   117篇
  1992年   106篇
  1991年   83篇
  1990年   35篇
  1989年   37篇
  1988年   38篇
  1987年   31篇
  1986年   18篇
  1985年   10篇
  1984年   17篇
  1983年   13篇
  1982年   9篇
  1981年   6篇
  1979年   2篇
  1974年   2篇
  1973年   3篇
  1972年   2篇
  1935年   2篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
701.
本文在综述四川酸性降水范围、发展趋势预测的基础上,根据野外调查、现场考察和有关资料,阐述了酸雨形成的多种污染源及其对农业生态系统的危害。着重分析和论证了酸沉降(含酸雨、酸雾)对农作蔬菜的影响,并对酸沉降形成的主要几种污染影响范围和造成的经济损失采用分项估算法。估算公式为:S农损=D粮损×g×J+E蔬损×g×J+F油损×g×J,式中D、E、F分别代表粮食、蔬菜、油菜受酸沉降污染危害影响面积,g为每亩面积减产数量,J为单位产量价格。根据公式估算,经济损失为059-066亿元/年,取平均值≈S农损,总共为063亿元/年。  相似文献   
702.
本文在剖析绿色技术的概念内涵与特征的基础上,构建了由清洁生产技术、资源化技术、末端治理技术、生态农业技术、绿色食品技术、清洁消费技术与生态恢复技术等为主要内容的我国绿色技术体系,并从行政、经济、法律、教育及科研等五个方面阐述了促进我国可持续发展的绿色技术实施策略。  相似文献   
703.
704.
Forest management can benefit from decision support tools, including GIS-based multicriteria decision-aiding approach. In the Mediterranean region, Pinus pinaster forests play a very important role in biodiversity conservation and offer many socioeconomic benefits. However, the conservation of this species is affected by the increase in forest fires and the expansion of Matsucoccus feytaudi. This paper proposes a methodology based on commonly available data for assessing the values and risks of P. pinaster forests and to generating maps to aid in decisions pertaining to fire and phytosanitary risk management. The criteria for assessing the values (land cover type, legislative tools for biodiversity conservation, environmental tourist sites and access routes, and timber yield) and the risks (fire and phytosanitation) of P. pinaster forests were obtained directly or by considering specific indicators, and they were subsequently aggregated by means of GIS-based multicriteria analysis. This approach was tested on the island of Corsica (France), and maps to aid in decisions pertaining to fire risk and phytosanitary risk (M. feytaudi) were obtained for P. pinaster forest management. Study results are used by the technical offices of the local administration—Corsican Agricultural and Rural Development Agency (ODARC)—for planning the conservation of P. pinaster forests with regard to fire prevention and safety and phytosanitary risks. The decision maker took part in the evaluation criteria study (weight, normalization, and classification of the values). Most suitable locations are given to target the public intervention. The methodology presented in this paper could be applied to other species and in other Mediterranean regions.  相似文献   
705.
Climate change impacts human health in a variety of ways. Variables including the climate-related risk factor, the health outcome and location all determine the nature and extent of the impact. The existence of different pathways and endpoints presents a problem for quantifying and comparing impacts. Disability-adjusted life year (DALY) provides a common scale, whereby the impact of climate change on both acute and chronic health outcomes can be compared. This study presents a methodology to calculate the impact of climate change on human health at a local scale, using cardiovascular disease (CVD) and meteorological disaster-related injuries (DRIs) in Osaka Prefecture, Japan, as applied case studies. An additional very fine scale assessment of CVD conducted at the neighbourhood level to demonstrate the importance of conducting risk assessments at a local level. The comparative results calculated the impact of climate change in 2050 to be 16.866 DALY/100,000 population for CVD and 0.645 DALY/100,000 for meteorological DRIs. The actual impact of climate change by 2050 on CVD is judged to be higher, although the relative risk was projected to be lower (1.006, compared to 1.263 for meteorological DRIs). The fine scale assessment revealed the variations in the projected impact of climate change on CVD for all administrative zones in Osaka Prefecture. The range of impacts varied from 0 to 114.29 DALY/100,000. The results demonstrate the applicability of using DALY to quantify the impact of climate change on different health outcomes, using a transferable methodology, and provide information that enables evidence-based prioritisation of climate change adaptation strategies at a local scale.  相似文献   
706.
The Farm Animal Welfare Council’s concept of a Good Life gives an idea of an animal’s quality of life that is over and above that of a mere life worth living. The concept needs explanation and clarification, in order to be meaningful, particularly for consumers who purchase farm animal produce. The concept could allow assurance schemes to apply the label to assessments of both the potential of each method of production, conceptualised in ways expected to enhance consumers’ engagement such as ‘naturalness’ and ‘freedom’; and the concept of a life worth living as a safeguard threshold below which no animal’s actual welfare should fall, based on each animal’s overall affective states. This may provide a framework for development of the Good Life concept, within scientific and sociological fields, in order to allow reliable and influential use by assessors, consumers and retailers.  相似文献   
707.
研究了一种国产新型铝合金表面防护体系在多因素协同加速试验条件下的表面性能变化规律。涂层在0.01 Hz处的阻抗模值由初始的1.88×10~9 Ω下降为2.04×10~7 Ω。经历5个周期的户内多因素综合加速试验的过程中,2A97铝合金表面涂层体系的防护效果呈持续下降趋势,但5周期后尚未完全失效。  相似文献   
708.
In the present study, three-dimensional numerical simulations are conducted on hydrodynamics and light-intensity distribution of microalgae fluid flow in a helical tubular photobioreactor for CO2 capture. The effect of incident direction of the light illumination is discussed and the light/dark cycle frequency experienced by the microalgae fluid in the cross-section of the photobioreactor is investigated. The simulation results reveal the steadily nonhorizontal and unsymmetrical Dean roll-cells of the microalgae fluid flow in the cross-section of the helical tube. The external light projecting onto the helical tubular photobioreactor from the center is a better way for microalgae cultivation. The light/dark cycle frequency of the microalgae fluid flow is calculated based on the light-intensity distribution inside the photobioreactor. The light/dark cycle frequency keeps constant for the same stream trace of the microalgae flow while varies with different flow regions. Meanwhile, the light/dark cycle frequency increases with the increase in microalgae fluid velocity. The suitable demarcation between the light and the dark zone depends on the shape and the location of the Dean roll-cells.  相似文献   
709.
The favorable Turkish context for environmental legislation is undermined by a lack of public knowledge of the importance of sustainable development, a lack of coordination between experts in different professions and between government institutions, and a lack of the political will to make tough choices such as restricting the freedom of citizens to migrate to cities. This paper examines the specific implications of this context for the Aydin urban area in a rapidly urbanizing part of western Turkey. In the study area, urban and industrial areas both exhibited large proportional increases, largely at the expense of agricultural areas, and agricultural expansion occurred at the expense of natural areas. Compared to other areas of Turkey, the actual area of the increase was small, and the change for the study area as a whole was not striking because of the relatively recent history of urbanization and industrialization in Aydin. Nevertheless, the negative consequences of these changes may accelerate in the future if a strategy to control development and conversion of land use is not developed and implemented.  相似文献   
710.
Baseline assessments and monitoring of protected areas are essential for making management decisions, evaluating the effectiveness of management practices, and tracking the effects of global changes. For these purposes, the analysis of functional attributes of ecosystems (i.e., different aspects of the exchange of matter and energy) has advantages over the traditional use of structural attributes, like a quicker response to disturbances and the fact that they are easily monitored through remote sensing. In this study, we described the spatiotemporal patterns of different aspects of the ecosystem functioning of the Spanish national parks and their response to environmental changes between 1982 and 2006. To do so, we used the NOAA/AVHRR-GIMMS dataset of the Normalized Difference Vegetation Index (NDVI), a linear estimator of the fraction of photosynthetic active radiation intercepted by vegetation, which is the main control of carbon gains. Nearly all parks have significantly changed during the last 25 years: The radiation interception has increased, the contrast between the growing and nongrowing seasons has diminished, and the dates of maximum and minimum interception have advanced. Some parks concentrated more changes than others and the degree of change varied depending on their different environmental conditions, management, and conservation histories. Our approach identified reference conditions and temporal changes for different aspects of ecosystem functioning, which can be used for management purposes of protected areas in response to global changes.  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