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   577篇
  免费   3篇
  国内免费   10篇
安全科学   16篇
废物处理   36篇
环保管理   72篇
综合类   69篇
基础理论   141篇
污染及防治   182篇
评价与监测   38篇
社会与环境   32篇
灾害及防治   4篇
  2024年   6篇
  2023年   9篇
  2022年   17篇
  2021年   19篇
  2020年   12篇
  2019年   9篇
  2018年   12篇
  2017年   16篇
  2016年   28篇
  2015年   19篇
  2014年   26篇
  2013年   45篇
  2012年   37篇
  2011年   40篇
  2010年   35篇
  2009年   37篇
  2008年   34篇
  2007年   25篇
  2006年   34篇
  2005年   24篇
  2004年   23篇
  2003年   13篇
  2002年   15篇
  2001年   7篇
  2000年   5篇
  1999年   1篇
  1998年   3篇
  1997年   3篇
  1996年   5篇
  1995年   4篇
  1994年   3篇
  1993年   4篇
  1992年   2篇
  1991年   2篇
  1990年   1篇
  1989年   2篇
  1986年   3篇
  1985年   1篇
  1982年   1篇
  1981年   1篇
  1966年   1篇
  1964年   1篇
  1962年   1篇
  1960年   1篇
  1959年   1篇
  1958年   2篇
排序方式: 共有590条查询结果,搜索用时 15 毫秒
471.
In the last two centuries, developed nations have had an unprecedented generation of wealth showing a strong economic progress. Unfortunately, such economic development has not been witnessed in all countries and it does not represent the holistic face of the social progress. The main reason stands in the ideological limitations of capitalism itself, often ignoring local communities and environment while focusing exclusively on profit maximization, market share, dividends and bonuses. This failure it is also because of the division between two basic entities: nonprofit and for profit sectors. The segregation created between the economic values and social values, has created a system where the two different entities have failed to capture and integrate the multi-dimensional nature of the human being to satisfy social needs. Because of this increasing tension, the society needs to find a common ground solution, where the social and economic benefits of these two entities are merged together to generate an anti-fragile system. This research is an attempt to determine if the social business (SB) is capable to solve the problems arose from the free market idealogy, nonprofit philosophy, and the consequent social and economic inefficiency. Thus, the boundaries between the private, public and nonprofit sectors need to be changed. In addition, it is aimed to show that SB can solve social, economic, and environmental problems by using the entrepreneurial engine and the profit instrument, proving at the end to be by default a sustainable business model that respects the triple bottom line approach. The investigation method is based on literature review and theory development from three different fields: economics, development studies, and nonprofit management.  相似文献   
472.
对我国生态系统服务研究局限性的思考及建议   总被引:9,自引:1,他引:9  
自1997年生态系统服务的概念引入我国以来,我国学术界关于生态系统服务的研究呈现指数水平上升,但是研究的内容局限于不同区域和不同类型生态系统服务的价值化评估。评估结果的科学性和现实有效性受到质疑。本文结合我国目前的实际需求,我国生态系统服务研究的误区以及对千年生态系统评估(MA)研究成果的思考,认为目前和日后生态系统服务研究可以加强如下几个方面的研究:一是生态系统服务对人类福祉贡献的研究;二是生态系统服务功能退化现状的研究:三是生态系统服务退化原因和对策的研究。以丰富爱国生态系统服务研究的内窑。并为生态系统服务价值评估研究提供基础和补充。  相似文献   
473.
    
The deep, ultraoligotrophic piedmont lakes of Northern Patagonia (Argentina) are located in pristine and barely impacted areas,along a wide latitudinal range. Several studies have reported moderate to high total mercury (Hg) concentrations and contrastingmethylmercury (CH3Hg+) production in di erent lake compartments. Sources of Hg for western Patagonian terrestrial and aquaticecosystems are still not clear; while point sources can be ruled out and atmospheric deposition is a plausible source, along withcontribution from active volcanic areas of the Andes. In this investigation, we reported a noticeably seasonal, spatial (between lakebranches), and vertical (between water column strata) heterogeneity in the total Hg concentrations found in the pelagic zone of LakeMoreno. Sterile water samples taken in a depth profile of the lake showed moderate to high concentrations of CH3Hg+ in autumn witha decreasing trend with depth. Our results indicated that Hg is largely allocated in the plankton fraction between 10–53 m; whichdominated within the euphotic (epilimnetic) zone of the lake due to the high densities attained by two species of the dinoflagellateGymnodinium. The 53–200 m planktonic size fraction (comprising rotifers, ciliates and immature stages of crustaceans) and the > 200 m fraction (calanoid copepods and cladocerans) were found to bear strikingly lower total Hg concentrations, suggesting that themagnification of Hg at the planktonic consumer level is negligible.  相似文献   
474.
In recent times, environmental safety has been on priority in the development of new materials leading to a recycling and reuse approach to conserve the materials resources. This has resulted in more focus on the application of natural materials such as lignocellulosic fibers. This paper presents the characterization of continuous and aligned jute fabrics obtained from new and used sacks as well as the preparation and characterization of their composites incorporated into recycled polyethylene or as isolated pieces up to 40 wt%. These environmentally friendly composites were subjected to bend test and the fracture surface analyzed by SEM. The fabric from new sacks showed greater damage tolerance than that from the used sacks. The flexural stress increased steadily with increasing used fabric content up to 30 wt%, which is explained using fractographic studies on ruptured specimens. Used jute fabric composites are found to be viable alternative materials for low strength conventional materials based on cost–performance comparison with conventional materials.  相似文献   
475.
Journal of Polymers and the Environment - Demand for light-packaging materials for food and beverages is on the rise globally, especially in developing countries where several depend on packaged...  相似文献   
476.
The curculionid beetle Naupactus bipes (Germar, 1824) (Coleoptera: Curculionidae: Brachycerinae) has shown feeding preference for leaves of Piper gaudichaudianum, demonstrating an unexpected specificity for an insect considered to be a generalist. The leaves of P. gaudichaudianum contain the prenylated chromenes gaudichaudianic acid (4, major compound) and its methyl ester (5) in addition to a chromene (3) lacking one prenyl residue. In addition to 4, roots contain the chromone methyl ester (1) and methyl taboganate (2, major compound). Feeding on roots, larvae of N. bipes sequester exclusively the root-specific compounds 1 and 2. Adult beetles sequester the leaf-specific chromenes 3 and 4, but were found to also contain compounds 1 and 2 that are absent in leaves. Therefore, it is suggested that 1 and 2 are sequestered by larvae and can be found in the body of adult insects after long-term storage. In addition, 3 and 4, the major compounds in leaves were found to be associated with the eggs.  相似文献   
477.
An experimental setup is proposed to test the performance of safety devices based on radio frequency technology. The setup specifically tests devices designed for improving safety in dangerous areas of small size, such as those surrounding power press brakes. Tested here is a radio frequency identification (RFID) prototype, whose main objective is to prevent accidents by sending a stop signal to a machine when a worker’s wrist, bearing an RFID tag, gets too close to the dangerous area. An ABB IRB 2400L robot is used as a reference system; this system is capable of providing millimeter accuracy. A plastic hand and a wristband with at least one passive RFID tag are attached to the end of the robot arm, which emulates the behavior of a human arm. With this robotic approach, it is possible to test trajectories with different velocities and orientations and to simulate several risky situations associated with machine use. Several experiments are presented that were conducted with the RFID prototype, and statistics are reported on the distance detection capability of this safety system with respect to the plane that defines the dangerous area. A matrix approach is proposed for analyzing the robustness of safety devices that are designed to automatically prevent a worker entering in dangerous areas. The results show the benefits that development of a radio frequency device of this class could confer towards increasing worker safety.  相似文献   
478.
479.
The results of a geochemical survey carried out on the southern Campania shelf (southern Italy) are illustrated, offering a tempting opportunity to discuss the statement and definition of regional geochemical backgrounds for selected heavy metals. A total of 104 top core sediments, collected on average 1.5 km from one another and covering a shelf area of about 1300 km2, were analysed for grain size, organic carbon content (OC), and heavy-metal (As, Al, Fe, Cd, V, Cr, Zn, Cu, Ni, Hg, and Pb) concentrations. The characteristics of the area, scarcely influenced by industrial activities, and the extensive data set, make this study suitable for an appropriate multivariate and spatial geostatistical methodologies used for i) a reliable definition of large-scale marine sediments' geochemical backgrounds and ii) an accurate discrimination of different geological controls on trace-element distribution patterns. Enrichment factors estimated with respect to both the average shale composition and the weighted average metal concentrations measured in inland soils rule out significant anthropogenic inputs. A spatial-geostatistics approach (kriging of spatial component based on an accurate implementation of variographic surveying) was applied, and this is proposed as an appropriate quantitative methodology to define the geochemical backgrounds for the different heavy metals. Two nested spatial structures were identified for some of the heavy metals, thus allowing clear identification of local and regional geochemical controls related to the different spatial variability of grain size.  相似文献   
480.
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