全文获取类型
收费全文 | 19496篇 |
免费 | 1558篇 |
国内免费 | 4577篇 |
专业分类
安全科学 | 2693篇 |
废物处理 | 461篇 |
环保管理 | 3085篇 |
综合类 | 12720篇 |
基础理论 | 2020篇 |
环境理论 | 9篇 |
污染及防治 | 1645篇 |
评价与监测 | 996篇 |
社会与环境 | 1157篇 |
灾害及防治 | 845篇 |
出版年
2024年 | 61篇 |
2023年 | 309篇 |
2022年 | 608篇 |
2021年 | 788篇 |
2020年 | 783篇 |
2019年 | 659篇 |
2018年 | 564篇 |
2017年 | 723篇 |
2016年 | 871篇 |
2015年 | 913篇 |
2014年 | 1077篇 |
2013年 | 1261篇 |
2012年 | 1501篇 |
2011年 | 1630篇 |
2010年 | 1133篇 |
2009年 | 1234篇 |
2008年 | 926篇 |
2007年 | 1401篇 |
2006年 | 1380篇 |
2005年 | 1178篇 |
2004年 | 1015篇 |
2003年 | 950篇 |
2002年 | 815篇 |
2001年 | 695篇 |
2000年 | 606篇 |
1999年 | 585篇 |
1998年 | 380篇 |
1997年 | 321篇 |
1996年 | 216篇 |
1995年 | 208篇 |
1994年 | 179篇 |
1993年 | 162篇 |
1992年 | 107篇 |
1991年 | 67篇 |
1990年 | 45篇 |
1989年 | 24篇 |
1988年 | 33篇 |
1987年 | 22篇 |
1986年 | 17篇 |
1985年 | 13篇 |
1984年 | 25篇 |
1983年 | 18篇 |
1982年 | 22篇 |
1981年 | 14篇 |
1980年 | 20篇 |
1979年 | 18篇 |
1978年 | 7篇 |
1974年 | 8篇 |
1973年 | 9篇 |
1971年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
111.
Using improved neural network model to analyze RSP,NOx and NO2 levels in urban air in Mong Kok,Hong Kong 总被引:4,自引:0,他引:4
As the health impact of air pollutants existing in ambient addresses much attention in recent years, forecasting of airpollutant parameters becomes an important and popular topic inenvironmental science. Airborne pollution is a serious, and willbe a major problem in Hong Kong within the next few years. InHong Kong, Respirable Suspended Particulate (RSP) and NitrogenOxides NOx and NO2 are major air pollutants due to thedominant diesel fuel usage by public transportation and heavyvehicles. Hence, the investigation and prediction of the influence and the tendency of these pollutants are ofsignificance to public and the city image. The multi-layerperceptron (MLP) neural network is regarded as a reliable andcost-effective method to achieve such tasks. The works presentedhere involve developing an improved neural network model, whichcombines the principal component analysis (PCA) technique and theradial basis function (RBF) network, and forecasting thepollutant levels and tendencies based in the recorded data. Inthe study, the PCA is firstly used to reduce and orthogonalizethe original input variables (data), these treated variables arethen used as new input vectors in RBF neural network modelestablished for forecasting the pollutant tendencies. Comparingwith the general neural network models, the proposed modelpossesses simpler network architecture, faster training speed,and more satisfactory predicting performance. This improvedmodel is evaluated by using hourly time series of RSP, NOx and NO2 concentrations collected at Mong Kok Roadside Gaseous Monitory Station in Hong Kong during the year 2000. By comparing the predicted RSP, NOx and NO2 concentrationswith the actual data of these pollutants recorded at the monitorystation, the effectiveness of the proposed model has been proven.Therefore, in authors' opinion, the model presented in the paper is a potential tool in forecasting air quality parameters and hasadvantages over the traditional neural network methods. 相似文献
112.
The Prairie Adaptation Research Collaborative (PARC) has implemented an Internet Map Server (IMS) at the PARC web site (www.parc.ca) to 1) disseminate the geo-referenced results of PARC sponsored research on climate change impacts and adaptation, and 2) address data, information and knowledge management within the PARC network of researchers and partners. PARC facilitates interdisciplinary research on adaptation to the impacts of climate change in the Canadian Prairie Provinces. The web site is intended as a platform for sharing information and encouraging discussion of climate change impacts and adaptation. The IMS enables scientists and stakeholders to apply simple climate change scenarios to geo-referenced biophysical and social data, and dynamically create maps that display the geographic distribution of potential impacts of climate change. With a limited capacity for spatial analysis, most geo-processing and the climate impact modeling is done offline within a GIS environment. The IMS will serve the output from climate impact models, such that the model results can be customized by the web site user and be most readily applied to the planning and analysis of adaptation strategies. 相似文献
113.
114.
对室内装饰装修材料检测中甲醛分析方法的研究 总被引:2,自引:0,他引:2
目前室内装饰装修材料中甲醛含量的检测有六个类别,分析方法不统一,且没有一定的质量控制措施.文章对分析方法进行了改进,并且研究用水中的甲醛标样来对检测过程进行质量控制,结果较好. 相似文献
115.
116.
Gałuszka A 《Environmental monitoring and assessment》2005,110(1-3):55-70
In June of 2000, biogeochemical study was carried out in three ecosystems of the Holy Cross Mountains (south-central Poland).
This paper presents element concentrations and stable sulfur (and in one site lead) isotope ratios in rocks, detailed soil
profiles, and plant bioindicators including epiphytic lichen Hypogymnia physodes (L.) Nyl., mosses (Pleurozium schreberi (Brid.) Mitt., Hypnum cupressiforme Hedw. S. Str., Hylocomium splendens (Hedw.) B.S.G.), Scots pine (Pinus sylvestris L.), common birch (Betula pendula Roth.), aspen (Populus tremula L.) and English oak (Quercus robur L.). Chemical analyses were performed with ICP-AES and AAS methods in the accredited laboratory (Central Chemical Laboratory
of the Polish Geological Institute in Warsaw). The principal objective of this study was to compare the chemical composition
of rocks, soils and selected plant bioindicators between investigation sites using the same methods of sample collection,
preparation and analyses. The results of this study have shown that there is a high variability in concentrations of elements
in plant bioindicators from the same sites that can not be explained only by soil properties or anthropogenic influence. This
conclusion indicates that for biomonitoring purposes (especially with vascular plants) we cannot neglect individual features
of the species examined. 相似文献
117.
The province of Huelva in the SW of Spain presents high environmental contrasts: together with the great abundance of natural spaces, it shows the impacts of historical natural resources exploitation processes. In the Ria of Huelva, the effluents of the chemical industries must be added to the contaminating inputs of the Tinto and Odiel rivers, coming from the acid drainage of the mines located in the Iberian Pyrite Belt. This forced the Environmental Agency (AMA) to elaborate in 1987 an Effluent Remediation Plan in order to negate unacceptable environmental impacts. The application of a grey box systemic analysis to the AMD pollution, undergone by the Tinto and Odiel rivers has allowed to set a conclusive explanation of the sampling results observed for a period of 11 years, thus making available an overall view of the polluting process and, above all, an explanation of its partial aspects. 相似文献
118.
Selecting Socio-Economic Metrics for Watershed Management 总被引:1,自引:0,他引:1
The selection of social and economic metrics to document baseline conditions and analyze the dynamic relationships between
ecosystems and human communities are important decisions for scientists, managers, and watershed citizens. A large variety
of social and economic data is available but these have limited use without theoretical frameworks. In this paper, several
frameworks for reviewing social-ecosystem relations are offered, namely social sanctions, sense of place, civic structure,
and cultural differences. Underlying all of these frameworks are attitudes, beliefs, values, and norms that affect which questions
are asked and which indicators are chosen. Much work and significant challenges remain in developing a standard set of spatially
based socio-economic metrics for watershed management. 相似文献
119.
A simple, sensitive, convenient and low cost spectrofluorometric technique for determination of quinalphos is described. Quinalphos is decomposed with sodium ethoxide. Resultant sodium diethyl thiophosphate (Na-DETP) is extracted with a cationic fluorescein as ion pair complex into 1-chloro-2-nitrobenzene. The fluorescence of the ion pair, fluorescein-DETP is measured at 530 nm after excitation at 490 nm. This technique is applicable for the determination of quinalphos in water, food grains and vegetable samples up to ng level with Amberlite XAD-4. 相似文献
120.