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   628篇
  免费   7篇
  国内免费   15篇
安全科学   24篇
废物处理   1篇
环保管理   184篇
综合类   180篇
基础理论   125篇
环境理论   1篇
污染及防治   87篇
评价与监测   24篇
社会与环境   20篇
灾害及防治   4篇
  2022年   13篇
  2021年   21篇
  2020年   6篇
  2019年   8篇
  2018年   2篇
  2017年   26篇
  2016年   40篇
  2015年   18篇
  2014年   23篇
  2013年   24篇
  2012年   12篇
  2011年   57篇
  2010年   40篇
  2009年   54篇
  2008年   46篇
  2007年   35篇
  2006年   23篇
  2005年   13篇
  2004年   15篇
  2003年   23篇
  2002年   14篇
  2001年   16篇
  2000年   15篇
  1999年   17篇
  1998年   8篇
  1997年   9篇
  1996年   14篇
  1995年   10篇
  1994年   5篇
  1993年   5篇
  1992年   7篇
  1991年   4篇
  1990年   6篇
  1989年   1篇
  1988年   2篇
  1987年   4篇
  1986年   1篇
  1985年   4篇
  1984年   2篇
  1983年   1篇
  1982年   2篇
  1981年   1篇
  1978年   1篇
  1977年   1篇
  1973年   1篇
排序方式: 共有650条查询结果,搜索用时 187 毫秒
101.
It is important for humans to live in harmony with ecosystems. Evaluation of ecosystem services (ES) may be helpful in achieving this objective. In Japan, forest ecosystems need to be re-evaluated to prevent their degradation due to lack of forest management.In order to evaluate the effects of forest management on forest ES, we developed a process-based biogeochemical model to estimate water, carbon, and nitrogen cycles in forest ecosystems (BGC-ES). This model consists of four submodels: biomass, water cycle, carbon-nitrogen (CN) cycles, and forest management. The biomass submodel can calculate growth of forest biomass under forest managements.Several parameters of the model were calibrated using data from observations of evapotranspiration flux and quality of stream flow in forests. The model results were compared with observations of runoff water from a dam catchment site and with carbon flux observations.Our model was coupled with a basin-level GIS database of forests. Evaluations under various forest management scenarios were carried out for forests in a basin contained in the Ise Bay basin (Chubu region, Japan), where plantations (artificial forests) seemed to have degraded from poor forest management.Comparing our simulation results with those of forests without management in the basin, we found that the amounts of absorbed carbon and runoff were larger in managed forests. In addition, the volume of harvested timber was larger and its quality (diameter) was better in managed forests. Changes of ES within the various scenarios were estimated for their economic value and were compared with the cost of forest management.  相似文献   
102.
As part of the right of indigenous cultures to self-determination, several international bodies have recognized and addressed the role of indigenous communities in natural resources management, including the conservation of biodiversity. In the United States, disagreements regarding the application of the federal Endangered Species Act to Native American tribes have hindered the relationship between the federal and tribal governments on endangered species recovery. Our research examines the efforts of one Native American tribe, the Nez Perce, and the United States federal government to collaborate on federal gray wolf recovery in central Idaho. We interviewed members of the Nez Perce Tribe and U.S. Fish and Wildlife Service to characterize their relationship and explore the context in which the recovery program was implemented. Respondents attributed the success of the biological aspects of wolf recovery to the robustness of the wolf as a species and to close interagency coordination at the operational level. However, differences of opinion existed between the Tribe and Service concerning program funding, policy planning, and the rights and role of the Tribe in wolf management via co-management and cooperative management regimes. Respondents from both governments noted a clear hierarchical relationship at the strategic level, where policy planning and decision-making rested with the federal government. Lessons drawn from this case study can be applied across the international spectrum to improving partnerships, particularly at the strategic level, between indigenous and non-indigenous governance structures for protecting endangered species.  相似文献   
103.
通过在二类标准适用区进行不同高度的噪声监测试验,利用获得的监测数据进行统计分析,找出不同高度噪声Leq小时值的统计特征,从而确定二类功能区噪声垂直变化规律。  相似文献   
104.
Accounting for the mismanagement of tropical nearshore fisheries   总被引:2,自引:0,他引:2  
The underlying reason for the mismanagement of tropical nearshore fisheries is the implementation of policies and programs based on Western models and approaches, coupled with an inability and/or unwillingness to consider non-Western alternatives of empirically proven value. Such attitudes are embedded in donor and development agency behavior, and are demonstrated by the temperate bias in conventional approaches to fisheries education and management, with a corresponding lack of understanding of tropical milieux, and in the persistence of various prejudices. Adaptive Management, The Ecosystem Approach, Local Knowledge, and Protected Areas are discussed from the perspectives of Western models and pre-existing Pacific Island systems as alternative models. Given the parlous condition of the global environment and resources, the best non-Western pre-existing models and Western approaches must be blended to provide sustainable solutions.
Francis R. HickeyEmail:
  相似文献   
105.
Grasslands provide many ecosystem services required to support human well-being and are home to a diverse fauna and flora. Degradation of grasslands due to agriculture and other forms of land use threaten biodiversity and ecosystem services. Various efforts are underway around the world to stem these declines. The Grassland Programme in South Africa is one such initiative and is aimed at safeguarding both biodiversity and ecosystem services. As part of this developing programme, we identified spatial priority areas for ecosystem services, tested the effect of different target levels of ecosystem services used to identify priority areas, and evaluated whether biodiversity priority areas can be aligned with those for ecosystem services. We mapped five ecosystem services (below ground carbon storage, surface water supply, water flow regulation, soil accumulation and soil retention) and identified priority areas for individual ecosystem services and for all five services at the scale of quaternary catchments. Planning for individual ecosystem services showed that, depending on the ecosystem service of interest, between 4% and 13% of the grassland biome was required to conserve at least 40% of the soil and water services. Thirty-four percent of the biome was needed to conserve 40% of the carbon service in the grassland. Priority areas identified for five ecosystem services under three target levels (20%, 40%, 60% of the total amount) showed that between 17% and 56% of the grassland biome was needed to conserve these ecosystem services. There was moderate to high overlap between priority areas selected for ecosystem services and already-identified terrestrial and freshwater biodiversity priority areas. This level of overlap coupled with low irreplaceability values obtained when planning for individual ecosystem services makes it possible to combine biodiversity and ecosystem services in one plan using systematic conservation planning.  相似文献   
106.
Mass balanced models yield valuable information regarding ecological function and delivery of ecosystem services, but often rely on data collected well before many species were reduced to fractions of their original abundance. Lagoonal systems, such as Great South Bay (GSB), NY, sit on the interface of terrestrial and marine ecosystems and are prone to anthropogenic stressors but proximity to land also makes the presence of data regarding historic populations and structure more likely. To quantify over a century of ecosystem change, Ecopath models were developed for GSB at each of four time periods where commercial and scientific data exist: 1880s, 1930s, 1980s and 2000s. The results indicated that the GSB has experienced a decline in ecosystem maturity, loss of top keystone predators, a decline in connectivity to the ocean though the reduction of migratory species and increasing dominance of low trophic level organisms. These changes undermine the delivery of ecosystem services, increase conflicts over limited resources and suggest that present day restoration targets fail to recognize appropriate baselines. We discuss the role of stochastic events, which result in state changes that could be defined as regime shifts, and ecosystem connectivity to the long-term stability of lagoonal systems.  相似文献   
107.
108.
Area of habitat (AOH) is defined as the “habitat available to a species, that is, habitat within its range” and is calculated by subtracting areas of unsuitable land cover and elevation from the range. The International Union for the Conservation of Nature (IUCN) Habitats Classification Scheme provides information on species habitat associations, and typically unvalidated expert opinion is used to match habitat to land-cover classes, which generates a source of uncertainty in AOH maps. We developed a data-driven method to translate IUCN habitat classes to land cover based on point locality data for 6986 species of terrestrial mammals, birds, amphibians, and reptiles. We extracted the land-cover class at each point locality and matched it to the IUCN habitat class or classes assigned to each species occurring there. Then, we modeled each land-cover class as a function of IUCN habitat with (SSG, using) logistic regression models. The resulting odds ratios were used to assess the strength of the association between each habitat and land-cover class. We then compared the performance of our data-driven model with those from a published translation table based on expert knowledge. We calculated the association between habitat classes and land-cover classes as a continuous variable, but to map AOH as binary presence or absence, it was necessary to apply a threshold of association. This threshold can be chosen by the user according to the required balance between omission and commission errors. Some habitats (e.g., forest and desert) were assigned to land-cover classes with more confidence than others (e.g., wetlands and artificial). The data-driven translation model and expert knowledge performed equally well, but the model provided greater standardization, objectivity, and repeatability. Furthermore, our approach allowed greater flexibility in the use of the results and uncertainty to be quantified. Our model can be modified for regional examinations and different taxonomic groups.  相似文献   
109.
The Reynolds transport theorem (RTT) from mathematics and engineering has a rich history of success in mass transport dynamics and traditional thermodynamics. This paper introduces RTT as a complementary approach to traditional compartmental methods used in ecological modeling and network analysis. A universal system equation for a generic flow quantity is developed into a generic open-system differential expression for conservation of energy. Nonadiabatic systems are defined and incorporated into control volume (CV) and control surface (CS) perspectives of RTT where reductive assumptions in empirical data are then formally introduced, reviewed, and appropriately implemented. Compartment models are abstract, time-dependent systems of simultaneous differential equations describing storage and flow of conservative quantities between interconnected entities (the compartments). As such, they represent a set of flexible and somewhat informal, assumptions, definitions, algebraic manipulations, and graphical depictions subject to influence and selectively parsed expression by the modeler. In comparison, RTT compartment models are more rigorous and formal integro-differential equations and graphics initiated by the RTT universal system equation, forcing an ordered identification of simplifying assumptions, ending with clearly identified depictions of the transfer and transport of conservative substances in physical space and time. They are less abstract in the rigor of their equation development leaving less ambiguity to modeler discretion. They achieve greater consistency with other RTT compartment style models while possibly generating greater conformity with physical reality. Characteristics of the RTT approach are compared with those of a traditional compartment model of energy flow in an intertidal oyster-reef community.  相似文献   
110.
Exotic species invasion is widely considered to affect ecosystem structure and function. Yet, few contemporary approaches can assess the effects of exotic species invasion at such an inclusive level. Our research presents one of the first attempts to examine the effects of an exotic species at the ecosystem level in a quantifiable manner. We used ecological network analysis (ENA) and a social network analysis (SNA) method called cohesion analysis to examine the effect of zebra mussel (Dreissena polymorpha) invasion on the Oneida Lake, New York, USA, food web. We used ENA to quantify ecosystem function through an analysis of food web carbon transfer that explicitly incorporated flow over all food web paths (direct and indirect). The cohesion analysis assessed ecosystem structure through an organization of food web members into subgroups of strongly interacting predators and prey. Our analysis detected effects of zebra mussel invasion throughout the entire Oneida Lake food web, including changes in trophic flow efficiency (i.e., carbon flow among trophic levels) and alterations of food web organization (i.e., paths of carbon flow) and ecosystem activity (i.e., total carbon flow). ENA indicated that zebra mussels altered food web function by shunting carbon from pelagic to benthic pathways, increasing dissipative flow loss, and decreasing ecosystem activity. SNA revealed the strength of zebra mussel perturbation as evidenced by a reorganization of food web subgroup structure, with a decrease in importance of pelagic pathways, a concomitant rise of benthic pathways, and a reorganization of interactions between top predator fish. Together, these analyses allowed for a holistic understanding of the effects of zebra mussel invasion on the Oneida Lake food web.  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