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   263篇
  免费   10篇
  国内免费   2篇
安全科学   15篇
废物处理   11篇
环保管理   52篇
综合类   39篇
基础理论   82篇
环境理论   1篇
污染及防治   48篇
评价与监测   14篇
社会与环境   12篇
灾害及防治   1篇
  2023年   6篇
  2022年   5篇
  2021年   19篇
  2020年   11篇
  2019年   17篇
  2018年   13篇
  2017年   14篇
  2016年   16篇
  2015年   13篇
  2014年   13篇
  2013年   20篇
  2012年   17篇
  2011年   26篇
  2010年   12篇
  2009年   13篇
  2008年   12篇
  2007年   6篇
  2006年   13篇
  2005年   6篇
  2004年   3篇
  2003年   2篇
  2002年   3篇
  2001年   2篇
  1999年   2篇
  1998年   2篇
  1996年   1篇
  1994年   1篇
  1993年   1篇
  1991年   1篇
  1988年   3篇
  1987年   1篇
  1980年   1篇
排序方式: 共有275条查询结果,搜索用时 796 毫秒
231.
Wrasses are abundant reef fishes and the second most speciose marine fish family, yet little is known of their larval swimming abilities. In August 2010 at Moorea, Society Islands, we measured swimming ability (critical speed, Ucrit) of 80 settlement-stage larvae (11–17 mm) of 5 labrid species (Thalassoma quinquevittatum [n = 67], Novaculichthys taeniourus [n = 6], Coris aygula [n = 5], Halichoeres trimaculatus [n = 1] and H. hortulanus [n = 1]) and 33 new recruits of T. quinquevittatum. Median (mdn) larval Ucrit was 7.6–12.5 cm s−1. In T. quinquevittatum (n = 67), larvae of 12.5–14.5 mm swam faster (mdn 16.9 cm s−1) than smaller or larger larvae (mdn 3.9 and 3.2 cm s−1, respectively). Labrid larvae Ucrit is similar to that of other similar-sized tropical larvae, so labrids and species with comparable settlement sizes should have similar abilities to influence dispersal. Ucrit of T. quinquevittatum recruits decreased to 47–56% of larval Ucrit in 2 days, implying rapid physiological changes at settlement.  相似文献   
232.
Policy development related to marine protected areas (MPAs) occurs at three levels: international, national, and local. Recent developments with MPAs highlight their close links to broader national-level park and protected area policies, which in turn take their lead from initiatives and recommendations initiated, and increasingly dictated, by international organizations. Local-level inputs to MPA policies have tended to be limited to the immediate local area context despite the vital importance of community-level support and knowledge in meeting broader regional goals of marine conservation tied to networked MPAs. In this paper, we highlight the mechanisms to facilitate cooperation and communication among international, national, and local levels of policy and practice needed to address this deficit. These include the creation of a social network of institutions that both internationalizes and localizes MPA policy development, facilitating a more meaningful engagement of local people through their legitimate participation in national and international MPA gatherings. In addition, mechanisms to formalize partnerships, feedback information, resolve conflicts, and report accountabilities are needed. The success of the latter will depend on the level of recognition and support given to community-level institutions as opposed to the suite of technical training and short-term project-based interventions that have characterized local support over recent decades.  相似文献   
233.
234.
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   
235.
236.
Wildlife-vehicle collisions (WVCs) pose a significant safety and conservation concern in areas where high-traffic roads are situated adjacent to wildlife habitat. Improving transportation safety, accurately planning highway mitigation, and identifying key habitat linkage areas may all depend on the quality of WVC data collection. Two common approaches to describe the location of WVCs are spatially accurate data derived from global positioning systems (GPS) or vehicle odometer measurements and less accurate road-marker data derived from reference points (e.g., mile-markers or landmarks) along the roadside. In addition, there are two common variable types used to predict WVC locations: (1) field-derived, site-specific measurements and (2) geographic information system (GIS)-derived information. It is unclear whether these different approaches produce similar results when attempting to identify and explain the location of WVCs. Our first objective was to determine and compare the spatial error found in road-marker data (in our case the closest mile-marker) and landmark-referenced data. Our second objective was to evaluate the performance of models explaining high- and low-probability WVC locations, using congruent, spatially accurate (<3-m) and road-marker (<800-m) response variables in combination with field- and GIS-derived explanatory variables. Our WVC data sets were comprised of ungulate collisions and were located along five major roads in the central Canadian Rocky Mountains. We found that spatial error (mean ± SD) was higher for WVC data referenced to nearby landmarks (516 ± 808 m) than for data referenced to the closest mile-marker data (401 ± 219 m). The top-performing model using the spatially accurate WVC locations contained all explanatory variable types, whereas GIS-derived variables were only influential in the best road-marker model and the spatially accurate reduced model. Our study showed that spatial error and sample size, using road-marker data for ungulate species, are important to consider for model output interpretation, which will impact the appropriate scale on which to apply modeling results. Using road-marker references <1.6 km or GPS-derived data locations may represent an optimal compromise between data acquisition costs and analytical performance. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   
237.
Although theorists have suggested that aquatic environments or “blue space” might have particular restorative potential, to date there is little systematic empirical research on this issue. Indeed the presence of water has, unintentionally, been a confounding factor in research comparing people’s reactions to built and natural environments. Whereas aquatic features (rivers, lakes, coasts) are frequently present in visual stimuli representing natural environments they are rarely incorporated in stimuli portraying built environments. As many towns are, for good reason, located near water this is a potentially significant oversight. The current research collated a set of 120 photographs of natural and built scenes, half of which contained “aquatic” elements. Proportions of “aquatic”/“green”/“built” environments in each scene (e.g. 1/3rd, 2/3rds) were also standardised. Two studies investigated preferences (attractiveness, willingness to visit and willingness to pay for a hotel room with the view), affect and perceived restorativeness ratings for these photographs. As predicted, both natural and built scenes containing water were associated with higher preferences, greater positive affect and higher perceived restorativeness than those without water. Effect sizes were consistently large. Intriguingly, images of “built” environments containing water were generally rated just as positively as natural “green” space. We propose a number of avenues for further research including exploration of the mechanisms underlying these effects.  相似文献   
238.
Direct aerobic biodegradation of vinyl chloride (VC) offers a remedial solution for persistent vinyl chloride plumes that are not amenable to the anaerobic process of reductive dechlorination because of either prevailing geochemical conditions or the absence of active Dehalococcoides ethenogenes. However, tools are needed to evaluate and optimize aerobic VC bioremediation. This article describes the development and testing of two techniques—a microbiological tool and a molecular tool—for this purpose. Both methods are based on detection of bacteria that can use vinyl chloride and ethene as growth substrates in the presence of oxygen. The microbiological tool is an activity assay that indicates whether bacteria capable of degrading ethene under aerobic conditions are present in a groundwater sample. This activity assay gave positive results in the area of active VC degradation of an aerobic VC bioremediation test site. A rapid semiquantitative genetic assay was also developed. This molecular tool, based on polymerase chain reaction (PCR) detection of a gene involved in the metabolism of both ethene and VC, revealed the presence of potential VC degraders in an enrichment culture and site groundwater. These tools could provide a basis for judging the potential of aerobic VC degradation by ethenotrophs at other sites in addition to offering a mechanism for treatment monitoring and system optimization. © 2009 Wiley Periodicals, Inc.  相似文献   
239.
The purpose of this study was to develop a sensitive and specific method for quantifying dermal exposure to the resin acids 7-oxodehydroabietic acid (7-OXO), dehydroabietic acid (DHAA), abietic acid (AA), and pimaric acid (PA). In addition the method was evaluated in occupational settings during production of wood pellets. Tape-strips were spiked with the substances to evaluate the recovery of the acids from the tape. The removal efficiency of the tape was assessed by tape-stripping a specified area on a glass plate spiked with resin acids. The recovery of the acids from human skin in vivo was evaluated by applying acids in methanol onto the skin of volunteers. Occupational dermal exposure to the resin acids was assessed by tape-stripping the skin of workers involved in the production of wood pellets. The resin acids were analyzed by liquid chromatography mass spectrometry (LC-MS). The limit of detection was 15 pg (7-OXO), 150 pg (DHAA), 285 pg (AA) and 471 pg (PA) per injection. The recovery from spiked tapes was in general 100%. The removal efficiency of the tape was 48-101%. Recovery tests from human skin in vivo showed a mean recovery of 27%. Quantifiable amounts of resin acids were observed on four different skin areas with an increase in exposure during a work shift. This study shows that occupational dermal exposure to resin acids can be assessed by tape-stripping and quantified by LC-MS.  相似文献   
240.
A new water sample collection system was developed to improve representation of solids entrained in urban stormwater by integrating water-quality samples from the entire water column, rather than a single, fixed point. The depth-integrated sample arm (DISA) was better able to characterize suspended-sediment concentration and particle size distribution compared to fixed-point methods when tested in a controlled laboratory environment. Median suspended-sediment concentrations overestimated the actual concentration by 49 and 7% when sampling the water column at 3- and 4-points spaced vertically throughout the water column, respectively. Comparatively, sampling only at the bottom of the pipe, the fixed-point overestimated the actual concentration by 96%. The fixed-point sampler also showed a coarser particle size distribution compared to the DISA which was better able to reproduce the average distribution of particles in the water column over a range of hydraulic conditions. These results emphasize the need for a water sample collection system that integrates the entire water column, rather than a single, fixed point to properly characterize the concentration and distribution of particles entrained in stormwater pipe flow.  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