全文获取类型
收费全文 | 1788篇 |
免费 | 64篇 |
国内免费 | 163篇 |
专业分类
安全科学 | 178篇 |
废物处理 | 18篇 |
环保管理 | 310篇 |
综合类 | 831篇 |
基础理论 | 272篇 |
污染及防治 | 74篇 |
评价与监测 | 96篇 |
社会与环境 | 187篇 |
灾害及防治 | 49篇 |
出版年
2024年 | 8篇 |
2023年 | 18篇 |
2022年 | 53篇 |
2021年 | 70篇 |
2020年 | 65篇 |
2019年 | 53篇 |
2018年 | 25篇 |
2017年 | 78篇 |
2016年 | 85篇 |
2015年 | 71篇 |
2014年 | 66篇 |
2013年 | 89篇 |
2012年 | 85篇 |
2011年 | 153篇 |
2010年 | 73篇 |
2009年 | 94篇 |
2008年 | 75篇 |
2007年 | 113篇 |
2006年 | 98篇 |
2005年 | 75篇 |
2004年 | 71篇 |
2003年 | 86篇 |
2002年 | 58篇 |
2001年 | 52篇 |
2000年 | 45篇 |
1999年 | 53篇 |
1998年 | 48篇 |
1997年 | 29篇 |
1996年 | 24篇 |
1995年 | 16篇 |
1994年 | 15篇 |
1993年 | 11篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有2015条查询结果,搜索用时 531 毫秒
401.
分形理论中的计盒维数、信息维数和关联维数能分别从空间占据程度、格局强度和个体空间关联的尺度变化角度,揭示种群分布格局的尺度变化特征.本文应用以上3个分形维数探讨了福建梅花山国家级自然保护区拟赤杨种群分布格局的多尺度分布规律,计算结果表明,拟赤杨种群的分布格局具有分形特征,其计盒维数为1.0298~1.2982,信息维数为0.9728~1.2464,关联维数为0.5089~0.8047.拟赤杨种群的计盒维数、信息维数较高,而关联维数较小,表明该种群的分布格局强度相对较高,结构相对复杂,具有集聚分布的趋势. 相似文献
402.
A. S. KALLIMANIS‡ W. E. KUNIN† J. M. HALLEY S. P. SGARDELIS 《Conservation biology》2005,19(2):534-546
Abstract: Recent extinction models generally show that spatial aggregation of habitat reduces overall extinction risk because sites emptied by local extinction are more rapidly recolonized. We extended such an investigation to include spatial structure in the disturbance regime. A spatially explicit metapopulation model was developed with a wide range of dispersal distances. The degree of aggregation of both habitat and disturbance pattern could be varied from a random distribution, through the intermediate case of a fractal distribution, all the way to complete aggregation (single block). Increasing spatial aggregation of disturbance generally increased extinction risk. The relative risk faced by populations in different landscapes varied greatly, depending on the disturbance regime. With random disturbance, the spatial aggregation of habitat reduced extinction risk, as in earlier studies. Where disturbance was spatially autocorrelated, however, this advantage was eliminated or reversed because populations in aggregated habitats are at risk of mass extinction from coarse-scale disturbance events. The effects of spatial patterns on extinction risk tended to be reduced by long-distance dispersal. Given the high levels of spatial correlation in natural and anthropogenic disturbance processes, population vulnerability may be greatly underestimated both by classical (nonspatial) models and by those that consider spatial structure in habitat alone. 相似文献
403.
A fully non-linear analysis of forcing influences on temperatures is performed in the climate system by means of neural network modelling. Two case studies are investigated, in order to establish the main factors that drove the temperature behaviour at both global and regional scales in the last 140 years. In particular, our neural network model shows the ability to catch non-linear relationships among these variables and to reconstruct temperature records with a high degree of accuracy. In this framework, we clearly show the need of including anthropogenic inputs for explaining the temperature behaviour at global scale and recognise the role of El Niño southern oscillation for catching the inter-annual variability of temperature data. Furthermore, we analyse the relative influence of global forcing and a regional circulation pattern in determining the winter temperatures in Central England, showing that the North Atlantic oscillation represents the driven element in this case study. Our modelling activity and results can be very useful for simple assessments of relationships in the complex climate system and for identifying the fundamental elements leading to a successful downscaling of atmosphere–ocean general circulation models. 相似文献
404.
405.
Patrik L. Andersson Peter Haglund Mats Tysklind 《Environmental science and pollution research international》1997,4(2):75-81
The internal barrier of rotation (Erot) was calculated for all 209 polychlorinated biphenyls (PCBs) by using a semi-empirical
method, viz. the Austin Model 1 (AMI) Hamiltonian. The difference in total energy between a forced planar state and an optimised
twisted structure was defined as Erot. The Erot values were in the range of 8.33 to 483 kj/mol, and were significantly influenced
by the number of chlorine atoms inortho position. An additional structural characteristic of the PCBs influencing Erot ofortho substituted congeners was substitution by chlorine atoms in vicinalmeta positions, which is assumed to prevent outward bending ofortho substituents. This so-called buttressing effect contributed with 4 to 31 kj/mol per added chlorine atom. In conclusion, the
internal barrier of rotation, calculated for all 209 PCBs, provides an important structure dependent physico-chemical parameter
for multivariate modelling of future quantitative structure-activity and structure-property relationships (QSARs/QSPRs). 相似文献
406.
阐述了资源循环型农业的基本概念及其特征,根据循环经济的相关理论和国内外农业发展的实际情况,指出中国农业应在生态农业的基础上,朝着资源循环型农业的目标发展。 相似文献
407.
Burkhard O. Wagner 《Umweltwissenschaften und Schadstoff-Forschung》1998,10(4):245-253
Zusammenfassung UNEP International Register of Potentially Toxic Chemicals (IRPTC) wurde von der ersten VN-Umweltkonferenz 1972 geschaffen.
Sein Einfu? und Zusammenwirken in den 80ziger Jahren mit anderen internationalen Programmen der WHO, FAO, OECD und EG in der
Chemikalienkontrolle wird beschrieben. Nach dem Erdgipfel von Rio 1992 werden im VN-Rahmen drei neue Gremien gebildet, die
das Fachprogramm des Kapitels 19 der Agenda 21 (umweltfreundliches Chemikalienmanagement) umsetzen sollen: die United nations
Commission of Sustainable Development, das Intergovernmental Forum on Chemical Safety und das Interorganization Programme
for the Sound Management of Chemicals. Der Erdgipfel brachte auch für IRPTC eine Neuorientierung. Seit 1996 hat UNEP Chemicals,
wie sich IRPTC nunmehr nennt, drei Aufgaben in sein Arbeitsprogramm aufgenommen, die beschrieben werden: das internationale
übereinkommen zum Prior Informed Consent, das internationale übereinkommen zur Kontrolle der Persistent Organic Pollutants,
und schlie?lich sein traditionelles Arbeitsgebiet des Informations-austausches über Stoffe wird weitergeführt.
Die Aussagen dieses Beitrages sind die Meinung des Autors. Sie müssen nicht mit der Auffassung des Umweitbundesamtes oder von UNEP Chemicals übereinstimmen. 相似文献
Die Aussagen dieses Beitrages sind die Meinung des Autors. Sie müssen nicht mit der Auffassung des Umweitbundesamtes oder von UNEP Chemicals übereinstimmen. 相似文献
408.
宁波市危险废物管理、处置现状和对策 总被引:1,自引:0,他引:1
对宁波市危险废物现状进行了调查,分析了危险废物的来源、产量、特征及存在的主要问题.在此基础上,提出了宁波市危险废物管理处置对策,具体包括:加强危险废物申报登记工作;健全宁波市危险废物管理法律体系和监督管理机构;建立合理的危险废物收费制度;源头控制危险废物污染和建设危险废物集中处置场等. 相似文献
409.
Litter at beaches can come from more than one source and determining the proportions to assign pollution to different sources
is very complex. There is no widely accepted methodology at present that links litter items to their source. The aim of this
study was to create a method of assigning a source to litter found on beaches of the Bristol Channel but which could equally
be used on any beach. Various methods that attempt to establish the source of beach litter were evaluated; their strengths,
weaknesses, applicability and reliability for use on Bristol Channel, UK beaches were considered. Elements of existing methods
coupled with new ideas were utilized in the production of a ‘refined’ methodology: consequently a new method of assigning
a source to beach litter was developed. The developed ‘Matrix Scoring Technique’ was applied to data collected at Minehead
beach on the Bristol Channel, UK. Several numerical and nomenclature variations were used to produce a system that reflected
the various sources and eliminated as much bias as possible. This cross-tabulated matrix scoring system can produce an insight
into the contribution of different source groups to litter found on beaches. This novel approach requires further testing
with emphasis on a control data set. 相似文献
410.