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   617篇
  免费   4篇
  国内免费   7篇
安全科学   31篇
废物处理   41篇
环保管理   77篇
综合类   89篇
基础理论   132篇
环境理论   3篇
污染及防治   184篇
评价与监测   40篇
社会与环境   26篇
灾害及防治   5篇
  2023年   8篇
  2022年   10篇
  2021年   20篇
  2020年   16篇
  2019年   14篇
  2018年   16篇
  2017年   26篇
  2016年   29篇
  2015年   23篇
  2014年   39篇
  2013年   45篇
  2012年   44篇
  2011年   49篇
  2010年   33篇
  2009年   40篇
  2008年   43篇
  2007年   37篇
  2006年   30篇
  2005年   17篇
  2004年   24篇
  2003年   8篇
  2002年   15篇
  2001年   4篇
  2000年   6篇
  1999年   2篇
  1998年   9篇
  1997年   4篇
  1996年   3篇
  1995年   1篇
  1994年   6篇
  1993年   3篇
  1992年   1篇
  1991年   1篇
  1990年   1篇
  1985年   1篇
排序方式: 共有628条查询结果,搜索用时 15 毫秒
61.
The aim of this study was to determine the relative effects of landscape scale management intensity, agroecosystem type, local management intensity and edges on diversity patterns of functional groups of plants, carabid beetles, spiders and grasshoppers. Nine landscapes were selected differing in percent intensively used agricultural area (IAA), each with a pair of organic and conventional winter wheat fields and a pair of organic and conventional mown meadows. Within fields, plants were surveyed in the edge and in the interior. Carabid beetles and spiders were captured by funnel traps, while grasshoppers were sweep-netted in the meadows. Diversity patterns of study organisms were affected both by local variables (local management, agroecosystem type and within-field position) and by landscape scale management intensity. Species richness of grasses, presumably because of sowing low-diversity mixtures, and hunting spiders decreased with percent cover of IAA. Meadows differed from wheat fields in that they had higher species richness of forbs and grasses, as well as higher densities of hunting spiders. In contrast, more carabid individuals, especially of non-carnivore species, were captured in wheat fields. In field edges with their reduced management intensity and increased immigration, species richness of plants, carabids and spiders was higher than in the interiors regardless of agroecosystem type and management. Organic management enhanced forb richness and cover in both agroecosystem types. Organic management also increased grass cover in wheat fields, but not in meadows, and promoted species richness of non-carnivore carabids and hunting spiders, but not grasshoppers. The results show that agri-environmental management needs to be targeted to the agroecosystem's field size, because higher edge area led to higher species richness. Organic management affected several functional groups positively (forbs, non-carnivore carabids, hunting spiders), while lower landscape scale management intensity only increased species richness of grasses and spiders. The great differences in responses of functional groups to local cereal and grassland as well as landscape management suggest implementing more scale and group specific targets for agri-environmental schemes to improve their efficiency.  相似文献   
62.
The illegal wildlife trade has emerged as a growing and urgent environmental issue. Stakeholders involved in the efforts to curb wildlife trafficking include nongovernmental organizations (NGOs), academia, and state government and enforcement bodies. The extent to which these stakeholders work and communicate among each other is fundamental to effectively combatting illicit trade. Using the United Kingdom as a case study, we used a social network analysis and semistructured interviews of stakeholders to assess communication relationships in the counter wildlife trafficking community. The NGOs consistently occupied 4 of the 5 most central positions in the generated networks, whereas academic institutions routinely occupied 4 of the 5 most peripheral positions. However, NGOs were the least diverse in their communication practices compared with the other stakeholder groups. Stakeholders identified personal relationships as the most important aspect of functioning communication. Participant insights also showed that stakeholder-specific variables (e.g., ethical and confidentiality concerns), competition, and fundraising can have a confounding effect on intercommunication. Evaluating communication networks and intrastakeholder communication trends is essential to creating cohesive, productive, and efficient responses to the challenges of combatting illegal wildlife trade. Article impact statement: Communication among those combatting illegal wildlife trade is confounded by stakeholder variables (ethics, confidentiality), competition, and fundraising.  相似文献   
63.
Several theoretical, analytical, and institutional difficulties have impeded the development and application of the assessment of cumulative environmental impacts. Watershed development on coastal wetlands offers an ideal context for evaluating the land disturbance target approach to cumulative impact assessment. A model land use planning system involving a time series approach was developed for Elkhorn Slough in California. The approach included four major components: evaluation of erosion susceptibility, measurement of land disturbance, establishment of a land disturbance target, and a comparison of existing and target land disturbance values. Further research is needed to test the transferability of the approach in a wide range of coastal watersheds and to verify the applicability of the methods to other cumulative impact problems.  相似文献   
64.
With energy crises looming, conflicts over resource extraction and production are on the rise. For communities lacking voice to participate in these conflicts, community-based organisations and local non-governmental organisations help to unite, communicate, and negotiate with other stakeholders. In this paper we compare two cases that demonstrate the roles of organisations in providing voice to citizenry impacted by environmental justice issues. We use Senecah's concept of Trinity of Voice for the purposes of evaluation. These cases provide contrasting examples of how local/regional organisations chose to either expand their organisation's mission to intervene or stick to a strict reading of their mission thus excluding involvement. In both examples we found that organisational involvement, or lack thereof, influenced how citizens were involved in decision-making with one case leading to legislation protecting property owners from industrial activities, and the other leading to a lack of effective involvement and negatively impacted citizens.  相似文献   
65.
PROBLEM: After decreasing to a historic low in 1997, motorcycle crash-related fatalities are increasing. Although causes remain unclear, motorcycle rider education and licensing play key roles in reducing motorcycle crashes and injuries. Yet, little is known about what constitutes effective rider training and licensing. This study develops a model of best practices in motorcycle rider education and licensing and combines primary and secondary data to identify states that most closely adhere to this model. Evidence on the validity of the model is also examined. METHOD: States were rated along three areas of best practices: (a) program administration; (b) rider education; and (c) licensing based on 2001 data collected for a National Highway Traffic Safety Administration (NHTSA)-sponsored study. RESULTS: Results indicate wide variation in states' adherence to best practices; several states meet most, others very few. When the areas of best practices are considered separately, a state tends to behave similarly on all three. Initial evidence supports the validity of the model, with high best practices states having the lowest rates of motorcycle fatalities. IMPACT ON TRAFFIC SAFETY: As motorcycle-related crashes increase and state and federal support for rider education programs diminishes, it is critical that states identify deficiencies in their program and learn from successful states about efficient, cost-effective strategies for increasing best practices in motorcycle rider education and licensing.  相似文献   
66.
Stream-subsurface exchange results from a complex ensemble of transport mechanisms that require different modeling approaches. Field and laboratory experiments show that advective exchange through the underlying sediments is an important mechanism of solutes transport and storage in riverine systems. Here, Transient Storage Model parameters are obtained for reactive solute exchange driven by bedform-induced advection. Consideration of exchange induced by this single mechanism allows specific relationships between model parameters and system properties like solute reactivity to be identified. This work shows that when a simplified model like the Transient Storage Model is applied to analyze metal storage in river sediments, particular attention must be devoted to the choice of modeling parameters.  相似文献   
67.
68.
Temporal variations in protein, carbohydrate, and lipid levels were studied in a passive suspension feeder, the gorgonian Paramuricea clavata. The samples were collected every month for mature and immature colonies over a three-year period (1997–2000). The relationship between biochemical composition and reproductive output was examined on the basis of the 1998 and 1999 data. In female and male P. clavata colonies, the tissue displayed differences in lipid concentrations only in winter–spring, due to the high lipid levels attained by female colonies in this period. Immature colonies showed significant differences in lipid concentration only with respect to mature females in spring. There were clear seasonal trends in the lipid and carbohydrate levels in P. clavata, with maximum values in winter–spring [male lipid 212±75 SD μg mg−1 of organic matter (OM) and female lipid 274±103 SD μg mg−1 of OM; male and female carbohydrate 68±14 SD μg mg−1 of OM], coinciding with maximum food concentration/quality, and minimum values in summer–autumn (male and female lipid 155±57 SD μg mg−1 of OM; male and female carbohydrate 56±14 SD μg mg−1 of OM), coinciding with low food concentration/quality. The relationship between reproductive output and tissue concentrations of lipids, carbohydrates, and proteins was not straightforward, although there was an evident overlap of the lipid accumulation and the gonadal development. The results of this study show that protein, carbohydrate, and lipid levels may provide a record of episodes in the ecological cycle bearing on the trophic aspects of the target species. The results indicate that information on seasonal biochemical levels may explain benthopelagic coupling processes, provided factors such as natural diet, feeding rates, reproduction, and growth are well understood.  相似文献   
69.
70.
Elodea canadensis has been proposed as a potential biomonitor due to its wide distribution and apparent ability to accumulate pollutants in aquatic ecosystems. We investigated the effects of copper sulfate on growth in E. canadensis to determine its effectiveness as a biomonitor of copper pollution in aquatic systems and whether growth is a suitable index of sub-lethal stress. Copper sulfate significantly slowed or stopped growth at all concentrations (low: 1 ppm, medium: 5 ppm, high: 10 ppm of copper sulfate) used. Final plant drymass was significantly lower in medium and high copper treatments compared with controls. E. canadensis appears to be very sensitive to copper levels, and may be useful as a biomonitor of copper levels in aquatic systems. However, its utility as a bioaccumulator may be limited, because we observed senescence of most leaves in all copper-treated plants following 4 weeks of treatment.  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