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   5293篇
  免费   112篇
  国内免费   80篇
安全科学   241篇
废物处理   264篇
环保管理   1355篇
综合类   483篇
基础理论   1222篇
环境理论   6篇
污染及防治   1262篇
评价与监测   372篇
社会与环境   215篇
灾害及防治   65篇
  2023年   32篇
  2022年   27篇
  2021年   62篇
  2020年   49篇
  2019年   70篇
  2018年   99篇
  2017年   106篇
  2016年   133篇
  2015年   131篇
  2014年   116篇
  2013年   588篇
  2012年   201篇
  2011年   285篇
  2010年   214篇
  2009年   217篇
  2008年   276篇
  2007年   281篇
  2006年   253篇
  2005年   183篇
  2004年   194篇
  2003年   206篇
  2002年   193篇
  2001年   83篇
  2000年   108篇
  1999年   105篇
  1998年   76篇
  1997年   71篇
  1996年   77篇
  1995年   78篇
  1994年   64篇
  1993年   69篇
  1992年   79篇
  1991年   46篇
  1990年   58篇
  1989年   53篇
  1988年   37篇
  1987年   40篇
  1986年   54篇
  1985年   45篇
  1984年   47篇
  1983年   53篇
  1982年   42篇
  1981年   58篇
  1980年   48篇
  1979年   24篇
  1978年   25篇
  1977年   17篇
  1976年   13篇
  1975年   15篇
  1971年   13篇
排序方式: 共有5485条查询结果,搜索用时 218 毫秒
161.
The prospect of unprecedented environmental change, combined with increasing demand on limited resources, demands adaptive responses at multiple levels. In this article, we analyze different attributes of farm-level capacity in central Arizona, USA, in relation to farmers’ responses to recent dynamism in commodity and land markets, and the institutional and social contexts of farmers’ water and production portfolios. Irrigated agriculture is at the heart of the history and identity of the American Southwest, although the future of agriculture is now threatened by the prospect of “mega-droughts,” urbanization and associated inter-sector and inter-state competition over water in an era of climatic change. We use farm-level survey data, supplemented by in-depth interviews, to explore the cross-level dimensions of capacity in the agriculture–urban nexus of central Arizona. The surveyed farmers demonstrate an interest in learning, capacity for adaptive management and risk-taking attitudes consistent with emerging theory of capacity for land use and livelihood transformation. However, many respondents perceive their self-efficacy in the face of future climatic and hydrological change as uncertain. Our study suggests that the components of transformational capacity will necessarily need to go beyond the objective resources and cognitive capacities of individuals to incorporate “linking” capacities: the political and social attributes necessary for collective strategy formation to shape choice and opportunity in the future.  相似文献   
162.
A promising approach for addressing sustainability problems is to recognize the unique conditions of a particular place, such as problem features and solution capabilities, and adopt and adapt solutions developed at other places around the world. Therefore, research and teaching in international networks becomes critical, as it allows for accelerating learning by sharing problem understandings, successful solutions, and important contextual considerations. This article identifies eight distinct types of research and teaching collaborations in international networks that can support such accelerated learning. The four research types are, with increasing intensity of collaboration: (1) solution adoption; (2) solution consultation; (3) joint research on different problems; and (4) joint research on similar problems. The four teaching types are, with increasing intensity of collaboration: (1) adopted course; (2) course with visiting faculty; (3) joint course with traveling faculty; and (4) joint course with traveling students. The typology is illustrated by extending existing research and teaching projects on urban sustainability in the International Network of Programs in Sustainability, with partner universities from Europe, North America, Asia, and Africa. The article concludes with challenges and strategies for extending individual projects into collaborations in international networks.  相似文献   
163.
This study takes an historical approach in order to establish how the form and function of the social-ecological system that represents the Bangladesh south-western coastal zone has changed over recent decades. Time series data for a range of ecosystem services and drivers are analysed to define the range of trends, the presence of change points, slow and fast variables and the significant drivers of change. Since the 1980s, increasing gross domestic product and per capita income mirror rising levels of food and inland fish production. As a result, the size of population below the poverty line has reduced by ~17 %. In contrast, non-food ecosystem services such as water availability, water quality and land stability have deteriorated. Conversion of rice fields to shrimp farms is almost certainly a factor in increasing soil and surface water salinity. Most of the services experienced statistically significant change points between 1975 and 1980, and among the services, water availability, shrimp farming and maintenance of biodiversity appear to have passed tipping points. An environmental Kuznets curve analysis suggests that the point at which growing economic wealth feeds back into effective environmental protection has not yet been reached for water resources. Trends in indicators of ecosystem services and human well-being point to widespread non-stationary dynamics governed by slowly changing variables with an increased likelihood of systemic threshold changes/tipping points in the near future. The results will feed into simulation models and strategies that can define alternative and sustainable paths for land management.  相似文献   
164.
While methodological choices are critical for solution-oriented adaptation research, the current debate on these is underdeveloped and characterized by simple dichotomies such as bottom-up and top-down as well as vaguely defined concepts such as vulnerability. Adaptation challenges and approaches for addressing them are more diverse than these labels suggest. This paper addresses this deficit by developing a diagnostic framework that helps to identify approaches suitable for addressing a given adaptation challenge. The framework was developed out of the necessity to discuss diverse approaches from natural science, social science and practice in a set of adaptation case studies conducted within the European funded MEDIATION project. Based on these case studies complemented by the literature, we iteratively abstracted typical adaptation challenges researched, typical approaches taken, and empirical, theoretical and normative criteria applied for choosing a particular approach. Our results refine the methodological debate by distinguishing between the three general adaptation challenges of identifying adaptation needs, identifying adaptation measures and appraising adaptation options. Adaptation challenges are further classified according to private and public interest involved, individual or various types of collective action involved, data/model availability, decision-making time horizon, etc. For each type of challenge and approach, we give examples and discuss salient issues. Our results point to the opportunity to apply institutional and behavioural research to support the identification of measures and possibly avoiding barriers in practice. The diagnostic framework also serves as the basis for the forthcoming guidance for assessing vulnerability, impacts and adaptation to be published by the UNEP programme of research on climate change vulnerability, impacts and adaptation.  相似文献   
165.
Environmental restoration projects are commonly touted for their ecological positives, but such projects can also provide significant socioeconomic and cultural benefits to local communities. We assessed the social dimensions of a large-scale coral reef restoration project in Maunalua Bay, O‘ahu, where >1.32 million kg of invasive marine macroalgae was removed from 11 hectares (90,000 m2; 23 acres) of impacted coral reef in an urbanized setting. We interviewed 131 community stakeholders and analyzed both quantitative and qualitative data to assess human uses of the environment, assess perceptions of environmental health, and characterize social dimensions (+/?) associated with the invasive algae removal effort. Results indicate substantial direct economic benefits, including the creation of more than 60+ jobs, benefiting more than 250 individuals and 81 households. The project helped develop a skilled workforce in a local business dedicated to environmental restoration and increased the capacity of community organizations to address other threats to reefs and watersheds. Other major benefits include revitalization of Native Hawaiian cultural practices and traditions and the successful use of harvested invasive algae as compost by local farmers. Our results show the project heightened community awareness and a broader sense of stewardship in the area, creating enabling conditions for collective community action. Our findings show that restoration projects that explicitly incorporate efforts to build community awareness, involvement, and a shared responsibility for a site may ultimately create the long-term capacity for sustainable stewardship programs. We conclude by discussing lessons learned for engaging productively with communities in environmental restoration and stewardship, which remains a central focus in conservation worldwide.  相似文献   
166.
Corridors (variably called landscape linkages, connectors, and gateways) are expanses of a landscape that facilitate the flow or movement of individuals, genes, and ecological processes. Protected areas with their buffer zones and the corridors that connect them are cornerstones of modern conservation actions to maintain the biodiversity we have and restore what we have lost. Policy and governance to guide the establishment and management of protected areas and supporting buffer zones is well established in the Central Indian Highlands. A policy and governance structure to create the context and enabling conditions for corridor maintenance, creation, and recovery is emerging but is constrained by the reigning land-management paradigm that separates conservation from development rather than mainstreaming species and habitat conservation into the rural development agenda. Well-nourished, healthy human populations and healthy ecosystems are inextricably linked. The worsening ecological conditions in the Central Indian Highlands can trigger the emergence of a common agenda for an inclusive, caring, and environment-friendly mode of development. The alternative is the business-as-usual scenario: a continuation of worsening ecological conditions. Entry points through the biodiversity, agriculture production, resource extraction, and economic/social sectors to enable integrated sustainable landscape management are identified. These include deepening what it means to successfully conserve a species combined with explicit threat analysis for at-risk tigers and the landscapes that supports them; landscape scenario modeling to advance communication by synthesizing diverse forms of research and articulating and evaluating alternative socio-economic futures; and the use of the smart green infrastructure process as an approach to development rather than only as a way to mitigate environmental damage. Models are presented to scale up from isolated conservation interventions to collective impact that unites supportive government partners with individuals, NGOs, and economic interests to achieve viable long-term relationships in human and natural systems to value, maintain, and recover landscape connectivity.  相似文献   
167.
Regional Environmental Change - We examined landscape exposure to wildfire potential, insects and disease risk, and urban and exurban development for the conterminous US (CONUS). Our analysis...  相似文献   
168.
The study aims to compare the detection of 16S rRNA gene of Dehalococcoides species and the microcosm study for biotransformation in predicting reductive dechlorination of chlorinated ethenes in ground water at hazardous waste sites. A total of 72 ground water samples were collected from 12 PCE or TCE contaminated sites in the United States. The samples were analyzed and used to construct microcosms in the laboratory. The results showed that the presence of Dehalococcoides DNA was well associated with dechlorination to ethene in the field. Nearly half of the wells where Dehalococcoides DNA was detected had ethene as a dechlorination end product. In comparison, for ground water samples of 16 wells where ethene was detected, ethene was produced in 11 of the corresponding microcosms. For most microcosms, during two years of incubation, dechlorination was less extensive than that observed in the field.  相似文献   
169.
Ozone profiles are often used to investigate day-to-day and year-to-year variability in origins of free tropospheric ozone. With this in mind, more than 50 ozonesonde launches were conducted in Beltsville, MD, during the summers of 2004 through 2007. Budgets of free tropospheric ozone were calculated for each ozone profile in the four summers using a laminar identification (LID) method and unusual episodes were analyzed with respect to meteorological variables. The laminar method showed that stratosphere-to-troposphere transport (ST) accounted for greater than 50% of the free tropospheric ozone column on 17% of days sampled, a more pronounced influence than regional convective and lightning (RCL) sources. The ST origins were confirmed with trajectories, and tracers (water vapor and potential vorticity). The amount of free tropospheric ozone from ST and RCL sources varied from year-to-year (up to 13%) and can be explained by differences in mean meteorological patterns. On average, almost 30% of the free tropospheric column was attributed to ST influence, about twice as much as RCL, although the LID method may not capture weeks-old lightning influences as in a chemical model. The prevalence of ST ozone in summertime Beltsville soundings was similar to six sounding sites in the IONS-04 campaign [Thompson, A.M., et al., 2007b. Intercontinental Transport Experiment Ozonesonde Network Study (IONS, 2004): 1. Summertime upper tropospheric/lower stratosphere ozone over northeastern North America. J. Geophys. Res. 112, D12S12; Thompson, A.M., et al., 2007c. Intercontinental Transport Experiment Ozonesonde Network Study (IONS, 2004): 2. Tropospheric ozone budgets and variability over northeastern North America. J. Geophys. Res. 112, D12S13.] and to statistics from a 30 year climatology of European soundings [Collette, A., Ancellet, G., 2005. Impact of vertical transport processes on the tropospheric ozone layering above Europe. Part II: Climatological analysis of the past 30 years. Atmos. Environ. 39, 5423–5435]. The Beltsville record also demonstrated the value of soundings for air quality forecasting in an urban area. The 22 nighttime soundings collected over Beltsville in 2004–2007 can be divided into distinct polluted and unpolluted subsets, the former 20 ppbv higher in residual layer ozone (1 km) than the latter. These distinctions propagated to daytime differences of 10 ppbv at the surface in the Washington, DC, area, with the high-ozone residual layers leading to non-attainment of the National Ambient Air Quality Standard for ozone. More frequent ozone observations aloft appear essential for better understanding ozone variability and for enabling air quality modelers to achieve more accurate ozone forecasts.  相似文献   
170.
Aircraft emissions affect air quality on scales from local to global. More than 20% of the jet fuel used in the U.S. is consumed by military aircraft, and emissions from this source are facing increasingly stringent environmental regulations, so improved methods for quickly and accurately determining emissions from existing and new engines are needed. This paper reports results of a study to advance the methods used for detailed characterization of military aircraft emissions, and provides emission factors for two aircraft: the F-15 fighter and the C-130 cargo plane. The measurements involved outdoor ground-level sampling downstream behind operational military aircraft. This permits rapid change-out of the aircraft so that engines can be tested quickly on operational aircraft. Measurements were made at throttle settings from idle to afterburner using a simple extractive probe in the dilute exhaust. Emission factors determined using this approach agree very well with those from the traditional method of extractive sampling at the exhaust exit. Emission factors are reported for CO2, CO, NO, NOx, and more than 60 hazardous and/or reactive organic gases. Particle size, mass and composition also were measured and are being reported separately. Comparison of the emissions of nine hazardous air pollutants from these two engines with emissions from nine other aircraft engines is discussed.  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