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   1619篇
  免费   35篇
  国内免费   33篇
安全科学   70篇
废物处理   9篇
环保管理   290篇
综合类   882篇
基础理论   161篇
环境理论   1篇
污染及防治   84篇
评价与监测   128篇
社会与环境   47篇
灾害及防治   15篇
  2024年   3篇
  2023年   12篇
  2022年   13篇
  2021年   30篇
  2020年   66篇
  2019年   15篇
  2018年   15篇
  2017年   38篇
  2016年   45篇
  2015年   36篇
  2014年   63篇
  2013年   63篇
  2012年   52篇
  2011年   93篇
  2010年   57篇
  2009年   111篇
  2008年   74篇
  2007年   88篇
  2006年   80篇
  2005年   67篇
  2004年   62篇
  2003年   89篇
  2002年   83篇
  2001年   60篇
  2000年   75篇
  1999年   61篇
  1998年   46篇
  1997年   40篇
  1996年   19篇
  1995年   32篇
  1994年   19篇
  1993年   25篇
  1992年   19篇
  1991年   9篇
  1990年   6篇
  1989年   4篇
  1988年   3篇
  1987年   2篇
  1986年   4篇
  1985年   1篇
  1983年   1篇
  1982年   1篇
  1981年   3篇
  1977年   1篇
  1975年   1篇
排序方式: 共有1687条查询结果,搜索用时 31 毫秒
151.
抚顺市生态环境现状:(森林覆盖率较高,但生态系统结构不合理,生态功能的发挥受到影响;矿产开发严重破坏生态平衡,矿区生态环境恶劣,历史欠帐大;自然保护区植被覆盖率较高,但生物多样性仍遭受严重威胁;农业生态问题严峻;水土流失严重;建成区布局紊乱,绿地系统缺乏连通性。)指出生态环境建设面临的制约因素为经济建设与生态建设不协调、经济发展模式粗放,生态恶化、缺乏有效的生态经济政策,资金短缺。  相似文献   
152.
本项目以哈尔滨啤酒(沈阳)有限公司啤酒厂为设计对象,其啤酒废水处理规模为1500m3/d,进水CODCr2000~2800mg/L。采用预处理-预酸化-IC反应器-活性污泥法-过滤为主体工艺,出水达到《辽宁省污水与废气排放标准》(DB21-60-89中一级标准)。为啤酒行业废水综合治理提供了较好的工艺途径。  相似文献   
153.
Biomass is one of the renewable energy sources on which policy makers are greatly dependent on since it is a flexible feedstock capable of conversion into electricity, transport liquid fuels and heat by chemical and biological processes on demand. Though numerous publications have examined the relationship of economic growth with renewable energy and other parameters, biomass energy has never been included in these studies. Then, this study examines the causal relationship within a multivariate panel cointegration/error correction framework which combines the cross-section and time series data while allowing for heterogeneity across different provinces. After employing panel data regression model ranging from 2003 through 2012 to examine the relationships of biofuels production with sustainable development in China, the paper concludes that the development of biofuel energy production integrated with the consideration of the improvement of income per capita, and the attraction of more capital investment, does make a significant contribution to economic growth. However, some negative side effects including the increase of greenhouse emissions and the decrease of marginal land still coexist with the economic development. Of course, the importance of these findings lies on their implications and their adoption on strategic policies.  相似文献   
154.
An indicator of the disturbance of natural systems, the landscape development intensity (LDI) index, was used to assess the potential for land-use within watersheds to influence the production/accumulation of methyl-mercury (MeHg) in river sediments. Sediment samples were collected from locations impacted by well-identified land-use types within the Mobile-Alabama River Basin in Southeastern USA. The samples were analyzed for total-Hg (THg) and MeHg concentrations and the obtained values correlated to the calculated LDI indexes of the sampled watersheds to assess the impact of prevalent land use/land cover on MeHg accumulation in sediments. The results show that unlike THg, levels of MeHg found in sediments are impacted by the LDI indexes. Overall, certain combinations of land-use types within a given watershed appear to be more conducive to MeHg accumulation than others, therefore, pointing to the possibility of targeting land-use practices as potential means for reducing MeHg accumulation in sediments, and ultimately, fish contamination.  相似文献   
155.
This paper focuses on comparative review and analysis of the systems of environmental protection, national environmental strategies and fundamentals of environmental legislation in Australia and the Russian Federation. These countries have many socioeconomic similarities, such as low population densities and richness in natural resources which are largely exported. The main disparity between Australia and Russia is in the types of economy. This paper ‘continues’ the sequence of recent scholarly publications on comparison of various features of environmental policies in the countries from all over the world. Comparative analysis in this research has been based on examination of scholarly publications, legislation, government documents, mass media sources and NGO responses. The analysis has revealed a number of differences including top-down implementation of policies in Russia whereas in Australia, each State (Territory) implements policies with significant independence from the Commonwealth Government. At the same time, similarities between the countries have been identified: for example, in deficits in the budget of local environmental authorities and in the presence of contradictions in legislation at national and regional levels of government. Suggestions resulting from this analysis include further integration of sustainable development strategies at all levels of Australian government to encourage further protection of the environment and, for Russia, creating a separate Ministry of Environmental Protection. These approaches should assist facilitation of sustainable development for both nations. Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue.  相似文献   
156.
Between the tenth and twentieth century the population of Paris city increased from a few thousand to near 10 million inhabitants. In response to the growing urban demand during this period, the agrarian systems of the surrounding rural areas tremendously increased their potential for commercial export of agricultural products, made possible by a surplus of agricultural production over local consumption by humans and livestock in these areas. Expressed in terms of nitrogen, the potential for export increased from about 60 kg N/km2/year of rural territory in the Middle Ages, to more than 5,000 kg N/km2/year from modern agriculture. As a result of the balance between urban population growth and rural productivity, the rural area required to supply Paris (i.e. its food-print) did not change substantially for several centuries, remaining at the size of the Seine watershed surrounding the city (around 60,000 km2). The theoretical estimate of the size of the supplying hinterland at the end of the eighteenth century is confirmed by the figures deduced from the analysis of the historical city toll data (octroi). During the second half of the twentieth century, the ‘food-print’ of Paris reduced in size, owing to an unprecedented increase in the potential for commercial export associated with modern agricultural systems based on chemical N fertilization. We argue that analysing the capacity of territories to satisfy the demand for nitrogen-containing food products of local or distant urban population and markets might provide new and useful insights when assessing world food resource allocation in the context of increasing population and urbanization.  相似文献   
157.
The Western Forest Complex (WEFCOM) of Thailand is comprised of many protected areas and has one of the highest wildlife populations in the country. Populations of wildlife in the WEFCOM have decreased dramatically over recent years. Rapid economic development has resulted in the conversion of forest into agricultural and pastoral land, which has directly and indirectly impacted the wildlife community. This research aimed to evaluate populations of domesticated cattle (Bos indicus) and buffalo (Bubalus bubalis) in the WEFCOM and their possible impacts on the wildlife community. Domesticated cattle and buffalo keepers from 1561 (or 3.3%) of houses in and near WEFCOM were interviewed. The average number of animals per household was 15.6 cattle and 8.5 buffalo. Most villagers released domesticated cattle and buffalo to forage in the protected areas. This tended to have a high impact on the wildlife community in Huai Kha Khaeng Wildlife Sanctuary and Tungyai Naresuan Wildlife Sanctuary. The least impacted areas were Luam Khlong Ngu National Park, Thong Pha Phum National Park and Chaleam Ratanakosin National Park. With a high risk to the wildlife community, law enforcement should be used in combination with a certain level of co-management with local communities.  相似文献   
158.
This study investigated the soil nematode community structure along the Yellow River in the Lanzhou area of China, and analyzed the impact of heavy metals (Cd, Pb, Cr, Cu, and Zn) and polycyclic aromatic hydrocarbons (PAHs) on the nematode community. Soil samples from five locations (named A–E), which were chosen for soil analysis, showed significant differences in their heavy metal content (p < 0.01), as well as in the variety of nematodes (up to 41 genera) and families (up to 20) that were present. The different samples also differed significantly in the total PAH content (p < 0.05), as well as the six types of PAH present. Sites A–C showed the most severe contamination with heavy metals and PAHs; these sites had the lowest abundance of fungivores and omnivore/predators, but the proportion of bacteriovores was the highest (p < 0.05). Site E, in contrast, showed only minor pollution with heavy metals and PAHs, and it contained the highest abundance of plant parasites (p < 0.05). Several nematode ecological indicators were found to correlate with concentration of soil pollutants at all the sites tested: the maturity index (MI, in addition to plant parasites), plant parasite index (PPI), ΣMI (including all the soil nematodes), Shannon-Wiener diversity index (H′′), and Wasilewska index (WI). Disturbance to the soil environment was more severe when MI, ΣMI, and H′ values were lower. The results of the study show that the abundance and structure of the soil nematode communities in the sampling locations were strongly influenced by levels of heavy metals and PAHs in the soil. They also show that the diversity index H′ and the maturity index can be valuable tools for assessing the impact of pollutants on nematodes.  相似文献   
159.
Ecoregion delineations have gained increased attention in Europe, especially following the Water Framework Directive 2000/60/EC (WFD), which provides the European Union’s first policy-relevant ecoregion map. However, the WFD’s ecoregions were created through a minor adaptation of Illies’ (Limnofauna Europaea. Gustav Fisher Verlag, Stuttgart, 1967/1978) freshwater zoogeographic regions, and the map’s specific boundaries have not been widely evaluated with respect to the WFD’s uses or their biogeographic accuracy. We examined the WFD ecoregion boundaries in Greece and its neighboring Balkan states by comparing them with the most prominent freshwater biogeographic boundaries as shown by riverine freshwater fish assemblages. Classification and ordination analyses of 23 river basin fish assemblages helped delineate natural faunal break boundaries in freshwater species assemblage distributions depicting major biogeographic barriers to aquatic biota dispersal. However, these biogeographic boundaries differ from those delineated in the WFD map, suggesting boundary errors and inconsistencies in the delineation method of the WFD ecoregions. We reviewed specific boundary disagreements and produced a map showing the region’s most prominent freshwater biogeographic boundaries by charting them on watershed borders among the four biotically dissimilar river basin groups in the southern Balkans. This regional evaluation reveals both a need to reconcile disparate approaches to ecoregion mapping and to promote the development of a new policy-relevant inland waters ecoregion framework that would support broad-scale water management and aquatic conservation.  相似文献   
160.
Despite biological invasions being a worldwide phenomenon causing significant ecological, economic, and human welfare impacts, there is limited understanding regarding how environmental managers perceive the problem and subsequently manage alien species. Spanish environmental managers were surveyed using questionnaires to (1) analyze the extent to which they perceive plant invasions as a problem; (2) identify the status, occurrence, and impacts of noxious alien plant species; (3) assess current effort and expenditure targeting alien plant management; and, finally, (4) identify the criteria they use to set priorities for management. In comparison to other environmental concerns, plant invasions are perceived as only moderately problematic and mechanical control is the most valued and frequently used strategy to cope with plant invasions in Spain. Based on 70 questionnaires received, 193 species are considered noxious, 109 of which have been the subject of management activities. More than 90% of species are found in at least one protected area. According to respondents, the most frequently managed species are the most widespread across administrative regions and the ones perceived as causing the highest impacts. The perception of impact seems to be independent of their invasion status, since only half of the species identified as noxious are believed to be invasive in Spain, while 43% of species thought to only be casual aliens are causing a high impact. Records of management costs are poor and the few data indicate that the total actual expenditure amounted to 50,492,437 € in the last decade. The majority of respondents stated that management measures are insufficient to control alien plants due to limited economic resources, lack of public awareness and support, and an absence of coordination among different public administrations. Managers also expressed their concern about the fact that much scientific research is concerned with the ecology of alien plants rather than with specific cost-efficient strategies to manage alien species.  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