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   3138篇
  免费   2篇
  国内免费   41篇
安全科学   72篇
废物处理   149篇
环保管理   338篇
综合类   435篇
基础理论   1137篇
污染及防治   640篇
评价与监测   211篇
社会与环境   195篇
灾害及防治   4篇
  2023年   9篇
  2022年   15篇
  2021年   24篇
  2020年   9篇
  2019年   7篇
  2018年   117篇
  2017年   126篇
  2016年   187篇
  2015年   58篇
  2014年   23篇
  2013年   55篇
  2012年   431篇
  2011年   222篇
  2010年   35篇
  2009年   42篇
  2008年   57篇
  2007年   77篇
  2006年   80篇
  2005年   403篇
  2004年   533篇
  2003年   415篇
  2002年   46篇
  2001年   40篇
  2000年   21篇
  1999年   32篇
  1998年   8篇
  1997年   11篇
  1996年   7篇
  1995年   11篇
  1994年   9篇
  1993年   5篇
  1992年   6篇
  1991年   8篇
  1990年   8篇
  1989年   8篇
  1986年   5篇
  1982年   3篇
  1975年   2篇
  1974年   2篇
  1973年   3篇
  1972年   2篇
  1966年   2篇
  1961年   1篇
  1957年   1篇
  1955年   1篇
  1938年   1篇
  1933年   1篇
  1931年   2篇
  1926年   1篇
  1920年   1篇
排序方式: 共有3181条查询结果,搜索用时 109 毫秒
851.
Am Beispiel des l?nderübergreifenden Biosph?renreservates Rh?n wurde das Konzept einer ?kosystemaren Umweltbeobachtung konkretisiert. Die Arbeiten dienten der Operationalisierung der hohen fachlichen Anforderungen des Rats von Sachverst?ndigen für Umweltfragen an eine ‘Allgemeine ?kologische Umweltbeobachtung’, die medienund sektorübergreifende sowie m?glichst weitgehend harmonisierte Datenerhebungen und eine integrierte Datenauswertung vorsieht. Es werden die Bausteine einer stufenweisen Harmonisierung der Datenerhebung und Auswertung vorgestellt. Vertiefend behandelt werden Fragen nach methodischen Ans?tzen für eine nachvollziehbare Auswahl von Beobachtungsr?umen und Messtandorten sowie für die r?umliche Verallgemeinerung von Beobachtungsergebnissen. Das Konzept der ?kosystemaren Umweltbeobachtung nutzt hierfür das Instrument der bundesweiten standort?kologischen Raumgliederung sowie geostatistische Verfahren zur r?umlichen Zusammenführung bestehender Beobachtungsprogramme und Messnetze. Ferner werden M?glichkeiten aufgezeigt, wie mit der Durchführung hydrologischer Gebietsanalysen und mit einem ?kosystemarem Wasserhaushaltsmodell auf der Grundlage verfügbarer Daten integrierende Aussagen zur Entwicklung von Wassereinzugsgebieten getroffen werden k?nnen.  相似文献   
852.
853.
Biodiversity Conservation in Traditional Coffee Systems of Mexico   总被引:27,自引:1,他引:26  
In Mexico, coffee is cultivated on the coastal slopes of the central and southern parts of the country in areas where two or more types of vegetation make contact. Based on management level and vegetational and structural complexity, it is possible to distinguish five main coffee production systems in Mexico: two kinds of traditional shaded agroforests (with native trees), one commercially oriented polyspecific shaded system, and two "modern" systems (shaded and unshaded monocultures). Traditional shaded coffee is cultivated principally by small-scale, community-based growers, most of whom belong to some indigenous culture group. Through an exhaustive review of the literature, we found that traditional shaded coffee plantations are important repositories of biological richness for groups such as trees and epiphytes, mammals, birds, reptiles, amphibians, and arthropods. We evaluated the conservation role of these traditional shaded systems by estimating the percentage of the whole coffee area under traditional management, by reviewing the ecological and geographical distribution of coffee areas in Mexico, and by connecting the geographical distribution of these coffee areas with recognized centers of species richness and endemism. The assesment revealed that in Mexico, coffee fields are located in a biogeographically and ecologically strategic elevational belt that is an area of overlap between the tropical and temperate elements and of contact among the four main types of Mexican forests. We also found that between 60% and 70% of these coffee areas are under traditional management and that at least 14 of 155 priority regions selected by experts as having high numbers of species and endemics overlap with or are near traditional coffee-growing areas.  相似文献   
854.
855.
856.
Institutions of Higher Education have to cope with an array of challenges in the 21st century including globalization of teaching, research and outreach activities; additionally there are dramatic increases in competition for students, staff and funding sources. Meanwhile, local and regional involvement in regional sustainable development is increasing in importance as well. This latter process is driven by the mandates from many sources for academic involvement in working on the multi-faceted issues pertaining to Sustainable Development (SD). This requires concerted action not only at the global, but also at the local and regional levels. This article provides an overview of this special issue of the Journal of Cleaner Production on the Roles of Academia in Regional Sustainable Development Initiatives. The essence of the 11 articles contained in this special issue is summarized and contextualized within the rapidly evolving academic efforts on SD. Recommendations are made of ways for academia to help their regions to make more rapid progress toward SD via involvement of their faculty, students and staff in Regional SD programs and processes.  相似文献   
857.
Innovative cities are essential for the economic growth and development of countries. At the same time, however, social and environmental problems related to city growth can be serious threats to the full realisation of the socio-economic contribution that cities can make. City environments thus often provide both new problems and the creative and diverse environments, which make it possible to solve them. The question of whether or not sustainable development is possible largely will be answered in cities. This is also the case for problems related to waste management. Landfills may be located in the countryside, but if a country is to reduce environmental costs, the results will rest on the innovation power of cities. In this paper it is argued that the notion of a 'system of innovation' is helpful in understanding the factors that shape the processes of innovation and that determine the extent to which environmental problems may be solved. In this context, institutional innovation and political innovation as compared to technical innovation are of special importance.  相似文献   
858.
In this study, the prevalence of different enteric viruses in commercial mussels was evaluated at the retail level in three European countries (Finland, Greece and Spain). A total of 153 mussel samples from different origins were analysed for human norovirus (NoV) genogroups I and II, hepatitis A virus (HAV) and hepatitis E virus (HEV). Human adenovirus (HAdV) was also tested as an indicator of human faecal contamination. A full set of controls (such as sample process control, internal amplification controls, and positive and negative controls) were implemented during the process. The use of a sample process control allowed us to calculate the efficiencies of extraction, which ranged from 79 to 0.5?%, with an average value of 10?%. Samples were positive in 41?% of cases, with HAdV being the most prevalent virus detected (36?%), but no significant correlation was found between the presence of HAdV and human NoV, HAV and HEV. The prevalences of human norovirus genogroup II, HEV and human NoV genogroup I were 16, 3 and 0.7?%, respectively, and HAV was not detected. The estimated number of PCR detectable units varied between 24 and 1.4?×?103?g?1 of digestive tract. Interestingly, there appeared to be a significant association between the type of mussel species (M. galloprovincialis) and the positive result of samples, although a complete overlap between country and species examined required this finding to be confirmed including samples of both species from all possible countries of origin.  相似文献   
859.
860.
Anthropogenic impacts on biodiversity can lead to biotic homogenization (BH) and biotic differentiation (BD). BH is a process of increasing similarity in community composition (including taxonomic, functional, and phylogenetic components), whereas BD is a process of decreasing similarity over space and time. Here, we conducted a systematic review of BH and BD in plant communities in tropical and subtropical forests to identify trends and knowledge gaps. Our bibliometric search in the Web of Science returned 1989 papers, of which 151 matched our criteria and were included in the analysis. The Neotropical region had the largest number of articles, and Brazil was the most represented country with 92 studies. Regarding the type of change, homogenization was more frequent than differentiation (noted in 69.6% of publications). The taxonomic diversity component was measured more often than functional and phylogenetic diversity components. Most studies (75.6%) assessed homogenization and differentiation based on a single observation in time; as opposed to few studies that monitored plant community over multiple years. Forest fragmentation was cited as the main determinant of homogenization and differentiation processes (57.2% of articles). Our results highlight the importance of evaluating community composition over time and more than taxonomic components (i.e., functional and phylogenetic) to advance understanding of homogenization and differentiation. Both processes were scale dependent and not mutually exclusive. As such, future research should consider differentiation as a potential transition phase to homogenization and that potential differences in both processes may depend on the spatial and temporal scale adopted. Understanding the complexity and causes of homogenization and differentiation is essential for biodiversity conservation in a world increasingly affected by anthropogenic disturbances.  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