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   763篇
  免费   42篇
  国内免费   21篇
安全科学   44篇
废物处理   37篇
环保管理   185篇
综合类   88篇
基础理论   237篇
环境理论   8篇
污染及防治   139篇
评价与监测   51篇
社会与环境   28篇
灾害及防治   9篇
  2023年   8篇
  2022年   16篇
  2021年   16篇
  2020年   16篇
  2019年   23篇
  2018年   38篇
  2017年   39篇
  2016年   50篇
  2015年   36篇
  2014年   35篇
  2013年   58篇
  2012年   37篇
  2011年   76篇
  2010年   47篇
  2009年   40篇
  2008年   46篇
  2007年   46篇
  2006年   45篇
  2005年   18篇
  2004年   24篇
  2003年   18篇
  2002年   14篇
  2001年   12篇
  2000年   7篇
  1999年   5篇
  1998年   6篇
  1997年   12篇
  1996年   5篇
  1995年   7篇
  1994年   2篇
  1993年   3篇
  1992年   6篇
  1990年   2篇
  1989年   1篇
  1987年   1篇
  1986年   1篇
  1984年   4篇
  1981年   1篇
  1979年   1篇
  1978年   1篇
  1976年   1篇
  1972年   1篇
  1971年   1篇
排序方式: 共有826条查询结果,搜索用时 500 毫秒
311.
The lack of knowledge regarding social diversity in the Wildland Urban Interface (WUI) or an in-depth understanding of the ways people living there interact to address common problems is concerning, perhaps even dangerous, given that community action is necessary for successful wildland fire preparedness and natural resource management activities. In this article, we lay out the knowledge and preliminary case study evidence needed to begin systematically documenting the differing levels and types of adaptive capacity WUI communities have for addressing collective problems such as wildland fire hazard. In order to achieve this end, we draw from two theoretical perspectives encompassing humans' interactions with their environment, including (1) Kenneth Wilkinson's interactional approach to community, (2) and certain elements of place literature. We also present case study research on wildfire protection planning in two drastically different California communities to illustrate how social diversity influences adaptive capacity to deal with hazards such as wildland fire. These perspectives promote an image of the WUI not as a monolithic entity but a complex mosaic of communities with different needs and existing capacities for wildland fire and natural resource management.  相似文献   
312.
Riparian buffers have the potential to improve stream water quality in agricultural landscapes. This potential may vary in response to landscape characteristics such as soils, topography, land use, and human activities, including legacies of historical land management. We built a predictive model to estimate the sediment and phosphorus load reduction that should be achievable following the implementation of riparian buffers; then we estimated load reduction potential for a set of 1598 watersheds (average 54 km2) in Wisconsin. Our results indicate that land cover is generally the most important driver of constituent loads in Wisconsin streams, but its influence varies among pollutants and according to the scale at which it is measured. Physiographic (drainage density) variation also influenced sediment and phosphorus loads. The effect of historical land use on present-day channel erosion and variation in soil texture are the most important sources of phosphorus and sediment that riparian buffers cannot attenuate. However, in most watersheds, a large proportion (approximately 70%) of these pollutants can be eliminated from streams with buffers. Cumulative frequency distributions of load reduction potential indicate that targeting pollution reduction in the highest 10% of Wisconsin watersheds would reduce total phosphorus and sediment loads in the entire state by approximately 20%. These results support our approach of geographically targeting nonpoint source pollution reduction at multiple scales, including the watershed scale.  相似文献   
313.
Agricultural non–point source (NPS) pollution poses a severe threat to water quality and aquatic ecosystems. In response, tremendous efforts have been directed toward reducing these pollution inputs by implementing agricultural conservation practices. Although conservation practices reduce pollution inputs from individual fields, scaling pollution control benefits up to the watershed level (i.e., improvements in stream water quality) has been a difficult challenge. This difficulty highlights the need for NPS reduction programs that focus efforts within target watersheds and at specific locations within target watersheds, with the ultimate goal of improving stream water quality. Fundamental program design features for NPS control programs—i.e., number of watersheds in the program, total watershed area, and level of effort expended within watersheds—have not been considered in any sort of formal analysis. Here, we present an optimization model that explores the programmatic and environmental trade-offs between these design choices. Across a series of annual program budgets ranging from $2 to $200 million, the optimal number of watersheds ranged from 3 to 27; optimal watershed area ranged from 29 to 214 km2; and optimal expenditure ranged from $21,000 to $35,000/km2. The optimal program configuration was highly dependent on total program budget. Based on our general findings, we delineated hydrologically complete and spatially independent watersheds ranging in area from 20 to 100 km2. These watersheds are designed to serve as implementation units for a targeted NPS pollution control program currently being developed in Wisconsin.  相似文献   
314.
For intersexual selection to occur, it is necessary that females choose between males. It is now well appreciated that constraints exist, which preclude females sampling all the available males in a population. These constraints are likely to have caused the evolution of sampling rules (such as the “best-of-n” rule) by which females sample males. Here we investigate the impact of female subsampling of the male population, not on the evolution of sampling behaviour, but on the population-level correlation between a male trait and currencies such as reproductive success. This study is important as it illustrates when population-level correlations can be safely used to infer the presence and strength of sexual selection in the field. We find that the correlation between a male trait and a mate choice variable rises steeply as the number of males sampled by each female increases, flattening above seven to ten males sampled. This shape is found to be remarkably robust, and little affected by, for example, the mate choice variable used, by noise in assessment, by sampling behaviour depending on female quality, or by population size. The only variable found to have a large impact is male clumping according to their “quality”. If females are sampling about four males, the maximum correlation that can be found at the population level is in the range 0.4–0.6, perhaps as little as 0.1 if males are strongly clumped. A recent review of the literature suggests that four is the average number of males that females sample. Thus, the absence of a strong correlation cannot by itself be used to infer that sexual selection is weak, as it may be due to females sampling few males. Received: 18 May 1998 / Accepted after revision: 18 July 1998  相似文献   
315.
Roofing as a source of nonpoint water pollution   总被引:12,自引:0,他引:12  
Sixteen wooden structures with two roofs each were installed to study runoff quality for four commonly used roofing materials (wood shingle, composition shingle, painted aluminum, and galvanized iron) at Nacogdoches, Texas. Each roof, either facing NW or SE, was 1.22 m wide x 3.66 m long with a 25.8% roof slope. Thus, there were 32 alternatively arranged roofs, consisting of four roof types x two aspects x four replicates, in the study. Runoff from the roofs was collected through galvanized gutters, downspouts, and splitters. The roof runoff was compared to rainwater collected by a wet/dry acid rain collector for the concentrations of eight water quality variables, i.e. Cu(2+), Mn(2+), Pb(2+), Zn(2+), Mg(2+), Al(3+), EC and pH. Based on 31 storms collected between October 1997 and December 1998, the results showed: (1) concentrations of pH, Cu, and Zn in rainwater already exceed the EPA freshwater quality standards even without pollutant inputs from roofs, (2) Zn and Cu, the two most serious pollutants in roof runoff, exceeded the EPA national freshwater water quality standards in virtually 100% and more than 60% of the samples, respectively, (3) pH, EC, and Zn were the only three variables significantly affected by roofing materials, (4) differences in Zn concentrations were significant among all roof types and between all roof runoff and rainwater samples, (5) although there were no differences in Cu concentrations among all roof types and between roof runoff and rainwater, all means and medians of runoff and rainwater exceeded the national water quality standards, (6) water quality from wood shingles was the worst among the roof types studied, and (7) although SE is the most frequent and NW the least frequent direction for incoming storms, only EC, Mg, Mn, and Zn in wood shingle runoff from the SE were significantly higher than those from the NW; the two aspects affected no other elements in runoff from the other three roof types. Also, Zn concentrations from new wood-shingle roofs were significantly higher than those from aged roofs of a previous study. The study demonstrated that roofs could be a serious source of nonpoint water pollution. Since Zn is the most serious water pollutant and wood shingle is the worst of the four roof types, using less compounds and materials associated with Zn along with good care and maintenance of roofs are critical in reducing Zn pollution in roof runoff.  相似文献   
316.
总结了美国斯坦福大学和橡树岭国家实验室等在美国能源部田纳西州橡树岭综合试验基地进行的铀污染原位微生物修复阶段性试验结果.本试验利用微生物以乙醇为电子供体还原地下水和沉积物中的六价铀为不溶解的四价铀,使之原位固定化.随后通过加入溶解氧和硝酸盐来试验微生物还原后的地下水层中还原固定态铀的稳定性.通过预处理和长期间隔注入乙醇...  相似文献   
317.
Regional Environmental Change - Small island developing states (SIDS) are among the most vulnerable in the world to the impacts of climate change. SIDS have prioritised adaptation to climate change...  相似文献   
318.
The distribution of mobile species in dynamic systems can vary greatly over time and space. Estimating their population size and geographic range can be problematic and affect the accuracy of conservation assessments. Scarce data on mobile species and the resources they need can also limit the type of analytical approaches available to derive such estimates. We quantified change in availability and use of key ecological resources required for breeding for a critically endangered nomadic habitat specialist, the Swift Parrot (Lathamus discolor). We compared estimates of occupied habitat derived from dynamic presence‐background (i.e., presence‐only data) climatic models with estimates derived from dynamic occupancy models that included a direct measure of food availability. We then compared estimates that incorporate fine‐resolution spatial data on the availability of key ecological resources (i.e., functional habitats) with more common approaches that focus on broader climatic suitability or vegetation cover (due to the absence of fine‐resolution data). The occupancy models produced significantly (P < 0.001) smaller (up to an order of magnitude) and more spatially discrete estimates of the total occupied area than climate‐based models. The spatial location and extent of the total area occupied with the occupancy models was highly variable between years (131 and 1498 km2). Estimates accounting for the area of functional habitats were significantly smaller (2–58% [SD 16]) than estimates based only on the total area occupied. An increase or decrease in the area of one functional habitat (foraging or nesting) did not necessarily correspond to an increase or decrease in the other. Thus, an increase in the extent of occupied area may not equate to improved habitat quality or function. We argue these patterns are typical for mobile resource specialists but often go unnoticed because of limited data over relevant spatial and temporal scales and lack of spatial data on the availability of key resources. Understanding changes in the relative availability of functional habitats is crucial to informing conservation planning and accurately assessing extinction risk for mobile resource specialists.  相似文献   
319.
The sustained decline in marine fisheries worldwide underscores the need to understand and monitor fisheries trends and fisher behavior. Recreational fisheries are unique in that they are not subject to the typical drivers that influence commercial and artisanal fisheries (e.g., markets or food security). Nevertheless, although exposed to a different set of drivers (i.e., interest or relaxation), recreational fisheries can contribute to fishery declines. Recreational fisheries are also difficult to assess due to an absence of past monitoring and traditional fisheries data. Therefore, we utilized a nontraditional data source (a chronology of spearfishing publications) to document historical trends in recreational spearfishing in Australia between 1952 and 2009. We extracted data on reported fish captures, advertising, and spearfisher commentary and used regression models and ordination analyses to assess historical change. The proportion of coastal fish captures reported declined approximately 80%, whereas the proportion of coral reef and pelagic fish reports increased 1750% and 560%, respectively. Catch composition shifted markedly from coastal temperate or subtropical fishes during the 1950s to 1970s to coral reef and pelagic species in the 1990s to 2000s. Advertising data and commentary by spearfishers indicated that pelagic fish species became desired targets. The mean weight of trophy coral reef fishes also declined significantly over the study period (from approximately 30–8 kg). Recreational fishing presents a highly dynamic social–ecological interface and a challenge for management. Our results emphasize the need for regulatory agencies to work closely with recreational fishing bodies to observe fisher behavior, detect shifts in target species or fishing intensity, and adapt regulatory measures. Tendencias Dinámicas de Captura en la Historia de la Pesca Recreativa con Arpón en Australia  相似文献   
320.
Mitigation translocation of nuisance animals is a commonly used management practice aimed at resolution of human–animal conflict by removal and release of an individual animal. Long considered a reasonable undertaking, especially by the general public, it is now known that translocated subjects are negatively affected by the practice. Mitigation translocation is typically undertaken with individual adult organisms and has a much lower success rate than the more widely practiced conservation translocation of threatened and endangered species. Nonetheless, the public and many conservation practitioners believe that because population‐level conservation translocations have been successful that mitigation translocation can be satisfactorily applied to a wide variety of human‐wildlife conflict situations. We reviewed mitigation translocations of reptiles, including our own work with 3 long‐lived species (Gila monsters [Heloderma suspectum], Sonoran desert tortoises [Gopherus morafkai], and western diamond‐backed rattlesnakes [Crotalus atrox]). Overall, mitigation translocation had a low success rate when judged either by effects on individuals (in all studies reviewed they exhibited increased movement or increased mortality) or by the success of the resolution of the human–animal conflict (translocated individuals often returned to the capture site). Careful planning and identification of knowledge gaps are critical to increasing success rates in mitigation translocations in the face of increasing pressure to find solutions for species threatened by diverse anthropogenic factors, including climate change and exurban and energy development. Problemas con la Mitigación por Traslocación de Herpetofauna  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