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   1801篇
  免费   205篇
  国内免费   260篇
安全科学   95篇
废物处理   12篇
环保管理   270篇
综合类   953篇
基础理论   518篇
污染及防治   60篇
评价与监测   85篇
社会与环境   240篇
灾害及防治   33篇
  2024年   6篇
  2023年   30篇
  2022年   65篇
  2021年   66篇
  2020年   66篇
  2019年   64篇
  2018年   63篇
  2017年   84篇
  2016年   78篇
  2015年   93篇
  2014年   88篇
  2013年   125篇
  2012年   106篇
  2011年   167篇
  2010年   123篇
  2009年   105篇
  2008年   79篇
  2007年   130篇
  2006年   145篇
  2005年   97篇
  2004年   92篇
  2003年   84篇
  2002年   48篇
  2001年   44篇
  2000年   38篇
  1999年   30篇
  1998年   26篇
  1997年   18篇
  1996年   23篇
  1995年   18篇
  1994年   14篇
  1993年   15篇
  1992年   6篇
  1991年   6篇
  1990年   7篇
  1989年   2篇
  1988年   4篇
  1987年   1篇
  1986年   2篇
  1981年   1篇
  1980年   2篇
  1979年   2篇
  1977年   2篇
  1975年   1篇
排序方式: 共有2266条查询结果,搜索用时 31 毫秒
991.
Sustainable urban water infrastructure planning is vital for all cities in developing countries, where rapid urbanization has exacerbated the increasingly burdened environment. Water sustainability is a prerequisite for economic growth, social equity, and living quality in urban areas. This paper documents the current challenges and summarizes the solutions adopted in water infrastructure planning and management. Then, case studies of how multilateral financial institutions have promoted sustainable water infrastructure planning through economic appraisal and the novel approaches adopted for sustainable water infrastructure planning and asset management, are presented for the three cities of Jiaozhou, Cixi, and Fangchenggang. Conclusions are made based on the comparison and analysis of the experiences drawn from the case studies of how economic analysis could help promote sustainable water infrastructure planning and management. It is illustrated that economic analysis that considers ecosystem services supply should be employed more in water infrastructure planning, operation, and management in China.  相似文献   
992.
Factors affecting population recovery from depletion are at the focus of wildlife management. Particularly, it has been debated how life‐history characteristics might affect population recovery ability and productivity. Many exploited fish stocks have shown temporal changes towards earlier maturation and reduced adult body size, potentially owing to evolutionary responses to fishing. Whereas such life‐history changes have been widely documented, their potential role on stock's ability to recover from exploitation often remains ignored by traditional fisheries management. We used a marine ecosystem model parameterized for Southeastern Australian ecosystem to explore how changes towards “faster” life histories might affect population per capita growth rate r. We show that for most species changes towards earlier maturation during fishing have a negative effect (3–40% decrease) on r during the recovery phase. Faster juvenile growth and earlier maturation were beneficial early in life, but smaller adult body sizes reduced the lifetime reproductive output and increased adult natural mortality. However, both at intra‐ and inter‐specific level natural mortality and trophic position of the species were as important in determining r as species longevity and age of maturation, suggesting that r cannot be predicted from life‐history traits alone. Our study highlights that factors affecting population recovery ability and productivity should be explored in a multi‐species context, where both age‐specific fecundity and survival schedules are addressed simultaneously. It also suggests that contemporary life‐history changes in harvested species are unlikely to increase their resilience and recovery ability.  相似文献   
993.
Marine protected areas (MPAs) are a commonly applied solution to coral reef degradation, yet coral reefs continue to decline worldwide. We argue that expanding the range of MPAs to include degraded reefs (DR‐MPA) could help reverse this trend. This approach requires new ecological criteria for MPA design, siting, and management. Rather than focusing solely on preserving healthy reefs, our approach focuses on the potential for biodiversity recovery and renewal of ecosystem services. The new criteria would help identify sites with the highest potential for recovery and the greatest resistance to future threats (e.g., increased temperature and acidification) and sites that contribute to MPA connectivity. The DR‐MPA approach is a compliment rather than a substitute for traditional MPA design approaches. We believe that the DR‐MPA approach can enhance the natural, or restoration‐assisted, recovery of DRs and their ecosystem services; increase total reef area available for protection; promote more resilient and better‐connected MPA networks; and improve conditions for human communities dependent on MPA ecosystem services.  相似文献   
994.
In October 1992, the Oceanographic Centre of Málaga of the Spanish Oceanographical Institute (IEO) started a monitoring project,Ecomálaga, which collects physical, chemical, biological and sedimentological data from the Alborán Sea shelf. The project is coordinated with similar projects in the Atlantic and Mediterranean Centres of IEO. The ultimate objective is to, understand the long-term changes of the essential marine-environmental parameters. So far, nine quarterly surveys have been carried out—from October 1992 to December 1994. The following variables were registered:abiotic: location weather, water temperature, salinity, pH, dissolved oxygen, chlorophyll a, nitrate, nitrite, phosphate, silicate,biotic: zooplankton biomass and species composition, and ichthyoplankton. The granulometric composition and organic matter content of sediments are also included. Data are stored in a computerized data base named Ecomálaga Data Base, with contributions from geology, physics, plankton biology and marine chemistry. The data base not only contains separate files for each research topic, but also allows for interchange between these files, resulting in a synoptic data output. It offers the users an output in the form of synthetic records of each station sampled. The analysis of the data indicates seasonal influences and ainshore-offshore gradient, as well as an Atlantic influence on the stations located in the transect closest to the Strait of Gibraltar.  相似文献   
995.
Abstract:  Small-scale, local disturbance of tropical forests, for example from selective logging, is widespread, but its effects on biodiversity and ecosystem function have rarely been studied. In 3 East African tropical rainforests, we investigated the effect of different levels of local forest disturbance on the frugivore community and on tree visitation and fruit removal rates of the small-seeded tree Celtis durandii. We quantified birds and primates in little and heavily disturbed sites, distinguishing between forest specialists, forest generalists, and forest visitors. We quantified frugivorous tree visitors and seed removal rates of C. durandii trees in the same sites. Forest disturbance reduced the species richness and density of the frugivore community and of forest specialists. Frugivorous species and individuals visiting the study trees were reduced significantly, which led to a marginally significant decline in fruit removal by all frugivores and a significant reduction in removal by forest specialists. Reduction in fruit removal by forest specialists was not compensated for by increases in removal by forest generalists or visitors. Results did not differ among the 3 rainforests, which suggests they were consistent at a regional scale. So local forest disturbance led to a loss of frugivores and their seed removal services. This suggests that large-seeded tree species and trees with small fruits are losing seed dispersers. Thus, local forest disturbance appears to have a more general negative impact on frugivores and their seed dispersal services than anticipated previously.  相似文献   
996.
欠发达地区生态旅游开发研究   总被引:1,自引:0,他引:1  
欠发达地区面临着资源短缺、生态退化、经济贫困的三重压力,其问题的核心是没有根据当地的资源找出适合的发展道路;本文通过分析欠发达地区生态系统,找出欠发达地区生态系统脆弱性和生态资源分布的耦合性,并提出了欠发达地区开展生态旅游的具体措施和途径。  相似文献   
997.
Demonstrating and predicting the existence of alternative states in natural communities remains a challenge for ecologists and is essential for resource managers. Positive feedback is often presented as central in maintaining alternative ecosystem states, but no formal approach relates this part of theory to real world applications. Through qualitative modelling of community response to long-term perturbations, we define generic mechanistic links between positive feedback and the occurrence of alternative states. Positive feedback diminishes a system's overall resistance to change, and can create and maintain correlations in the relative abundance of variables that coincide with alternative states.Through specific models of the dynamics of Tasmanian rocky-reef communities, which are affected by climate and fishing and persist within alternative states, we demonstrate the ability of our theoretical framework to predict alternative states in ecosystems and inform management intervention. A qualitative knowledge of community structure permits a thorough analysis of system feedback and an assessment of the potential for an ecosystem to exhibit alternative states. We illustrate the usefulness of the approach to inform management priorities, and to focus monitoring and field research on the key drivers of ecosystem dynamics.  相似文献   
998.
导游是旅游从业一线人员,代表着旅游业的形象,关系着旅游业的良性发展。在游客追求低廉出游价格时,导游因其弱势群体地位最终成为旅游服务利益方的牺牲品,导游生存、发展与管理已成为困扰旅游业的一大难题。SPC理论即服务利益链理论强调顾客与员工的让渡价值,认为企业盈利能力的增强主要源于顾客和员工的企业忠诚度并最终源于企业对内部员工的服务质量。基于SPC理论,探讨了我国服务型导游管理模式的构建,指出旅游服务各利益方应服务导游,创造导游良好的就业和发展环境,以解决导游管理难题。  相似文献   
999.
The importance of large reserves has been long maintained in the scientific literature, often leading to dismissal of the conservation potential of small reserves. However, over half the global protected-area inventory is composed of protected areas that are <100 ha, and the median size of added protected area is decreasing. Studies of the conservation value of small reserves and fragments of natural area are relatively uncommon in the literature. We reviewed SCOPUS and WOK for studies on small reserve and fragment contributions to biodiversity conservation and ecosystem services, and fifty-eight taxon-specific studies were included in the review. Small reserves harbored substantial portions (upward of 50%) of regional species diversity for many taxa (birds, plants, amphibians, and small mammals) and even some endemic, specialist bird species. Unfortunately, small reserves and fragments almost always harbored more generalist and exotic species than large reserves. Community composition depended on habitat quality, surrounding land use (agricultural vs. urban), and reserve and fragment size, which presents opportunities for management and improvement. Small reserves also provided ecosystem services, such as pollination and biological pest control, and cultural services, such as recreation and improved human health. Limitations associated with small reserves, such as extinction debt and support of area-sensitive species, necessitate a complement of larger reserves. However, we argue that small reserves can make viable and significant contributions to conservation goals directly as habitat and indirectly by increasing landscape connectivity and quality to the benefit of large reserves. To effectively conserve biodiversity for future generations in landscapes fragmented by human development, small reserves and fragments must be included in conservation planning.  相似文献   
1000.
The cascading effects of biodiversity loss on ecosystem functioning of forests have become more apparent. However, how edge effects shape these processes has yet to be established. We assessed how edge effects alter arthropod populations and the strength of any resultant trophic cascades on herbivory rate in tropical forests of Brazil. We established 7 paired forest edge and interior sites. Each site had a vertebrate-exclosure, procedural (exclosure framework with open walls), and control plot (total 42 plots). Forest patches were surrounded by pasture. Understory arthropods and leaf damage were sampled every 4 weeks for 11 months. We used path analysis to determine the strength of trophic cascades in the interior and edge sites. In forest interior exclosures, abundance of predaceous and herbivorous arthropods increased by 326% and 180%, respectively, compared with control plots, and there were significant cascading effects on herbivory. Edge-dwelling invertebrates responded weakly to exclusion and there was no evidence of trophic cascade. Our results suggest that the vertebrate community at forest edges controls invertebrate densities to a lesser extent than it does in the interior. Edge areas can support vertebrate communities with a smaller contingent of insectivores. This allows arthropods to flourish and indirectly accounts for higher levels of plant damage at these sites. Increased herbivory rates may have important consequences for floristic community composition and primary productivity, as well as cascading effects on nutrient cycling. By interspersing natural forest patches with agroforests, instead of pasture, abiotic edge effects can be softened and prevented from penetrating deep into the forest. This would ensure a greater proportion of forest remains habitable for sensitive species and could help retain ecosystem functions in edge zones.  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