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   5283篇
  免费   42篇
  国内免费   25篇
安全科学   84篇
废物处理   338篇
环保管理   392篇
综合类   776篇
基础理论   1103篇
环境理论   4篇
污染及防治   1821篇
评价与监测   490篇
社会与环境   330篇
灾害及防治   12篇
  2023年   54篇
  2022年   162篇
  2021年   147篇
  2020年   62篇
  2019年   74篇
  2018年   183篇
  2017年   135篇
  2016年   245篇
  2015年   148篇
  2014年   283篇
  2013年   474篇
  2012年   315篇
  2011年   350篇
  2010年   258篇
  2009年   211篇
  2008年   297篇
  2007年   302篇
  2006年   264篇
  2005年   196篇
  2004年   162篇
  2003年   142篇
  2002年   129篇
  2001年   103篇
  2000年   69篇
  1999年   48篇
  1998年   26篇
  1997年   20篇
  1996年   12篇
  1995年   37篇
  1994年   30篇
  1993年   15篇
  1992年   19篇
  1991年   12篇
  1990年   12篇
  1989年   12篇
  1988年   10篇
  1985年   8篇
  1967年   8篇
  1966年   13篇
  1965年   15篇
  1964年   30篇
  1963年   12篇
  1962年   18篇
  1961年   13篇
  1960年   10篇
  1959年   26篇
  1958年   28篇
  1957年   19篇
  1956年   13篇
  1955年   19篇
排序方式: 共有5350条查询结果,搜索用时 281 毫秒
271.
We record the distribution of 137Cs, K, Rb and Cs within individual Sphagnum plants (down to 20 cm depth) as well as 137Cs in vascular plants growing on a peatland in eastern central Sweden. In Calluna vulgaris137Cs was mainly located within the green parts, whereas Andromeda polifolia, Eriophorum vaginatum and Vaccinium oxycoccos showed higher 137Cs activity in roots. Carex rostrata and Menyanthes trifoliata showed variable distribution of 137Cs within the plants. The patterns of 137Cs activity concentration distribution as well as K, Rb and Cs concentrations within individual Sphagnum plants were rather similar and were usually highest in the capitula and/or in the subapical segments and lowest in the lower dead segments, which suggests continuous relocation of those elements to the actively growing apical part. The 137Cs and K showed relatively weak correlations, especially in capitula and living green segments (0-10 cm) of the plant (r = 0.50). The strongest correlations were revealed between 137Cs and Rb (r = 0.89), and between 137Cs and stable Cs (r = 0.84). This suggests similarities between 137Cs and Rb in uptake and relocation within the Sphagnum, but that 137Cs differs from K.  相似文献   
272.
Southern Chile encompasses one of the most extensive fjord regions of the world, the Patagonia, currently exposed to natural and anthropogenic perturbations. These fjord ecosystems provide important services to humans, which have not been adequately measured and valued. As a consequence, ecosystem services are commonly ignored in public policy design and in the evaluation of development projects. Here we tackle questions that are highly relevant for the nation’s development, namely (1) understanding fjord functioning, and (2) developing management strategies based on ecosystem services, in order to secure simultaneous and adequate use of these ecosystems which area influenced by ecological (e.g., biogeochemical) and productive (e.g., aquaculture, fisheries) processes. We also seek to strengthen the analysis of fjord ecosystem value from the economical (including coastal zoning), socio-cultural, institutional, and governmental points of view. In addition, the investigation of current and future effects of climate change on this large region offers a unique opportunity to understand the social and economic consequences of a global phenomenon at local to regional scales. Biogeochemical and socio-economic models will be used to simulate future scenarios under a gamut of management options.  相似文献   
273.
274.
In order to evaluate the extraction of pesticide residues that are transferred to the brew during mate drinking process of P.U.1 yerba mate leaves (Ilex paraguariensis), a special device to simulate the way in which mate is drunk in Uruguay was developed. The transfer to the brew of 12 organophosphates, 5 synthethic pyrethroids and one organochlorine pesticide from spiked samples was studied. The relationship between the transfer data thus obtained and physicochemical properties like water solubility (Ws), octanol-water coefficient (Kow) and Henry's constant (H) was evaluated. The extractability of the pesticide residues from yerba mate can be correlated with log Ws and log Kow. These transfer values allowed the calculation of ARLs (acceptable residue level) for the pesticides following Food and Agriculture Organization (FAO), World Health Organizaion (WHO) guidelines. These results can help the future establishment of maximum residue levels (MRLs).  相似文献   
275.

Background, aim, and scope  

The high consumption of blood lipid regulators is leading to frequent reports of the occurrence of fibrates in natural streams and wastewater effluents. This paper describes a study undertaken to evaluate the acute toxicity of bezafibrate, clofibric acid, gemfibrozil, and fenofibric acid, a metabolite of fenofibrate whose ecotoxicity has not been previously reported.  相似文献   
276.

Background, aim and scope  

Weathering patinas in rocks are the result of interaction processes between rock surfaces and atmosphere, biosphere and soil. Therefore, their textural and mineral composition is strongly related to environmental and bioactivity conditions. Whereas the development of weathering patinas in atmospheric conditions is well documented (e.g. typical Mediterranean patina), only very few studies focus on their formation in a burial environment. Our study of patinas developed on the tumular structure of Reguers de Seró deals with the knowledge of burial patinas from a textural and mineralogical point of view. The aims of this study include: (1) the characterisation of the rock used in this megalithic monument as well as inferences regarding the origin of the raw material; (2) the evaluation of the patinas developed on the surface of the carved steles; and (3) the discussion of the environmental conditions (atmospheric or burial) that favoured the development of the patinas.  相似文献   
277.
Place identity and place attachment have been related to several environmental variables such as appropriation, residential satisfaction, physical care taken of the neighbourhood, restorativeness, environmental attitudes and, especially, pro-environmental behaviour. However, the role of place identity and place attachment has not been analyzed in relation to anti-ecological behaviours such as transgressions of environmental protection laws. The aim of this study is to analyze the relationship of place identity, place attachment and environmental attitudes to the personal and social norms that explain the likelihood of illegal behaviours against the environment. The sample was composed of men and women, aged from 19 to 70 years, who were resident in rural, urban or tourist areas of a territory under high environmental protection. The strongest predictor of environmental transgression is personal norms, whereas place identity and place attachment have no direct relation with future transgression or personal norms. Place identity influences environmental attitudes and social norms, which are both antecedents of personal norms. The results led us to reconsider the efficacy of interventions aimed at encouraging compliance with environmental laws by only emphasizing individuals' bonds with the environment, and the need to extend the study of the role of personal and social norms in environmental protection.  相似文献   
278.
This article investigates the effects of stone powder sludge on the microstructure and strength development of alkali-activated fly ash and blast furnace slag mixes. Stone powder sludge produced from a crushed aggregate factory was used to replace fly ash and granulated blast furnace slag at replacement ratios of 0%, 10%, 20%, and 30% by mass. The unit weight and compressive strength of the samples were measured, and scanning electron microscopy/energy dispersive spectroscopy and X-ray diffraction (XRD) analyses were performed. The test results indicated that the compressive strength of alkali-activated blast furnace slag mixes using stone powder sludge was higher than that of the alkali-activated blast furnace slag control mix, but the compressive strength of alkali-activated fly ash mixes decreased with increasing replacement ratio of stone powder sludge. Microscopy results indicated that for alkaliactivated blast furnace slag samples, broken surfaces were more evident than for the alkali-activated fly ash samples. For all XRD diagrams, broad and diffuse peaks were observed around 2θ = 35° (d = 2.96–3.03 Å), implying amorphous or short-ordering structure phases.  相似文献   
279.
Wood is commonly used in residential combustion for heating purposes; however, it can be a major source of air pollutants, namely fine particles, volatile organic compounds and carbon monoxide. Since 2004, the PM10 daily limit value has been surpassed in Portugal, and the European Commission has stated that plans and programs must be designed in order to reduce these levels. In Portugal, 18% of PM10 emissions are due to residential wood combustion, which may deeply impact the PM10 levels in the atmosphere. The main aim of this study is to investigate the impact of residential wood combustion on the air quality in Portugal. The air quality modelling system MM5/CHIMERE was applied over Portugal for a winter month, for the following three scenarios: the reference scenario, considering the actual emissions of PM10; scenario 1, where residential wood combustion emissions are not considered; and scenario 2, which takes into account a complete conversion from traditional fireplaces to certified appliances (with a 90% reduction in PM emissions). The residential wood combustion contribution to PM10 air quality concentration values during January 2007 ranges from 0 to 14 μg m?3, with a mean contribution of 10 μg m?3 in the Lisboa area and 6 μg m?3 in the Porto region. Concerning the legislated values, the area where the daily average limit value (50 μg m?3) is exceeded decreases by 46% in the simulation when residential combustion is not considered. The modelling results for scenario 2 are not significantly different from those for scenario 1. In summary, the regulation of the residential wood combustion sector is as an effective way to reduce the PM10 levels in the atmosphere as regards air quality plans and programs.  相似文献   
280.
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