全文获取类型
收费全文 | 7654篇 |
免费 | 938篇 |
国内免费 | 1744篇 |
专业分类
安全科学 | 1632篇 |
废物处理 | 116篇 |
环保管理 | 1027篇 |
综合类 | 4308篇 |
基础理论 | 1182篇 |
污染及防治 | 635篇 |
评价与监测 | 337篇 |
社会与环境 | 665篇 |
灾害及防治 | 434篇 |
出版年
2024年 | 74篇 |
2023年 | 226篇 |
2022年 | 370篇 |
2021年 | 399篇 |
2020年 | 387篇 |
2019年 | 308篇 |
2018年 | 266篇 |
2017年 | 404篇 |
2016年 | 421篇 |
2015年 | 428篇 |
2014年 | 357篇 |
2013年 | 421篇 |
2012年 | 625篇 |
2011年 | 673篇 |
2010年 | 527篇 |
2009年 | 563篇 |
2008年 | 392篇 |
2007年 | 481篇 |
2006年 | 477篇 |
2005年 | 341篇 |
2004年 | 264篇 |
2003年 | 248篇 |
2002年 | 256篇 |
2001年 | 187篇 |
2000年 | 186篇 |
1999年 | 147篇 |
1998年 | 143篇 |
1997年 | 128篇 |
1996年 | 101篇 |
1995年 | 95篇 |
1994年 | 81篇 |
1993年 | 65篇 |
1992年 | 58篇 |
1991年 | 31篇 |
1990年 | 22篇 |
1989年 | 26篇 |
1988年 | 23篇 |
1987年 | 18篇 |
1986年 | 19篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1981年 | 11篇 |
1980年 | 13篇 |
1979年 | 12篇 |
1978年 | 10篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1972年 | 4篇 |
1971年 | 9篇 |
1970年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
31.
考虑边界条件不确定性的地下水污染风险分析 总被引:1,自引:0,他引:1
为分析边界条件不确定性对地下水污染质运移数值模拟模型输出结果的影响,运用Monte Carlo方法对一算例进行阐明,并从污染风险预报方面对模拟结果进行分析.为减少重复调用模拟模型产生的大量计算负荷,将边界条件(第一类边界条件-水头值)作为随机变量,建立地下水污染质运移数值模拟模型的Kriging替代模型,在保证较高精度的同时,实现了Monte Carlo模拟.结果表明:边界条件的不确定性,对地下水污染质运移数值模拟模型预报的结果有很大影响,考虑与未考虑边界条件不确定性得到的研究区污染羽分布差别较大.对地下水污染质运移数值模拟模型的Monte Carlo模拟结果进行统计与分析,可以评估研究区观测井1,2,3污染物浓度预报结果的可靠程度,并且可以预报出研究区观测井1,2,3遭受不同程度污染的风险. 相似文献
32.
典型铅锌矿化区不同土地利用类型土壤重金属污染特征与评价 总被引:1,自引:0,他引:1
选取云南者海典型铅锌矿区周边冶炼区(A)、粮食主产区(B)、保护区(C)三个区域土壤为研究对象,分析三个区域内林地(LD)和耕地(GD)土壤pH、总碳(TC)、总氮(TN)、总磷(TP)和5种重金属(Hg、Cd、Pb、Zn、Cu)含量,利用典范对应分析(CCA)研究不同土地利用类型下它们之间的关系,基于系统熵值与重金属生物毒性改进灰色聚类评价法对研究区重金属污染程度进行评价。结果表明,A、B、C三区土壤的5种重金属均超过云南省土壤背景值,且含量A区 > B区 > C区,所有土壤样品Hg、Cd、Pb、Zn、Cu平均含量分别为7.24、1.53、1 794、2 892、210 mg/kg;LD土壤重金属含量普遍高于GD。研究区土壤pH总体呈弱酸性,但A区土壤受矿业活动影响呈弱碱性。TC、TN含量和C/N值均表现出LD大于GD,但TP含量表现为GD显著大于LD (P<0.05)。CCA分析表明LD和GD土壤pH与Cd和Cu呈负相关,与Zn和Pb呈正相关,且pH对重金属含量的影响最大;TC、TP与重金属Cd和Cu在LD土壤中呈正相关,在GD土壤中呈负相关。改进灰色聚类评价结果表明重金属污染程度均表现为LD大于GD;A区污染最严重且均呈重度污染,B区次之,C区污染程度最轻。经比较本文改进的灰色聚类评价法在准确性和灵敏度方面优于传统方法。 相似文献
33.
Economic development and environmental protection: an ecological economics perspective 总被引:5,自引:0,他引:5
Rees WE 《Environmental monitoring and assessment》2003,86(1-2):29-45
This paper argues on both theoretical and empirical grounds that, beyond a certain point, there is an unavoidable conflictbetween economic development (generally taken to mean 'materialeconomic growth') and environmental protection. Think for a moment of natural forests, grasslands, marine estuaries, salt marshes, and coral reefs; and of arable soils, aquifers, mineraldeposits, petroleum, and coal. These are all forms of 'natural capital' that represent highly-ordered self-producing ecosystemsor rich accumulations of energy/matter with high use potential (low entropy). Now contemplate despoiled landscapes, eroding farmlands, depleted fisheries, anthropogenic greenhouse gases,acid rain, poisonous mine tailings and toxic synthetic compounds.These all represent disordered systems or degraded forms of energy and matter with little use potential (high entropy). The main thing connecting these two states is human economic activity. Ecological economics interprets the environment-economyrelationship in terms of the second law of thermodynamics. The second law sees economic activity as a dissipative process. Fromthis perspective, the production of economic goods andservices invariably requires the consumption of available energy and matter. To grow and develop, the economynecessarily 'feeds' on sources of high-quality energy/matter first produced by nature. This tends to disorder and homogenizethe ecosphere, The ascendance of humankind has consistently been accompanied by an accelerating rate of ecological degradation, particularly biodiversity loss, the simplificationof natural systems and pollution. In short, contemporary political rhetoric to the contrary, the prevailing growth-oriented global development paradigm is fundamentally incompatible with long-term ecological and social sustainability. Unsustainability is not a technical nor economic problem as usually conceived, but rather a state of systemic incompatibilitybetween a economy that is a fully-contained, growing, dependent sub-system of a non-growing ecosphere. Potential solutions fly inthe face of contemporary development trends and cultural values. 相似文献
34.
A modular approach to Integrated Assessment modeling 总被引:1,自引:0,他引:1
In this paper, we present a new approach to model coupling that probably forms the methodological basis of a new generation of Integrated Assessment models. This approach respects the knowledge and expertise that is embodied in existing models and encourages their gradual evolution. Modularity is the guiding principle. Our approach is distinguished by the way modules are coupled which is based on an interplay of a job control module, a numerical coupling module, and a couple of stand-alone functional modules. The numerical coupling module - the core component - serves to treat the feedbacks between the functional modules. A first implemented example that couples an economic and a climate module by means of a two-phase meta-optimization is presented here. The algorithm and mathematical structure behind are discussed as well as important features such as convergence behavior and reliability. 相似文献
35.
Aerosol Scavenging: Model Application and Sensitivity Analysis in the Indian Context 总被引:1,自引:0,他引:1
Sulfate aerosols have been found to bethe major contributors to precipitation acidity. Thus,in view of the long-term ecological repercussions theyhave on aquatic ecosystems and their acidity-potential,the present analysis focuses on a case study applicationof the layer-averaged aerosol-scavenging model (Okita et al., 1996) for predicting values of the wet scavengingcoefficient and sulfate concentrations in precipitationsamples on the basis of the information available forsome selected Indian cities. Through sensitivityanalysis (Pandey et al., 1997) the scavengingcoefficient has been found to be very strongly dependenton precipitation intensity. Comparison of modelpredictions has been done with the measured values forDelhi, Mumbai, Calcutta and Chennai in India. 相似文献
36.
Kimpo metropolitan landfill has received various kinds of wastessince January 1992. The leachate level was measured to be 10.3 m in May 1995 and the level increased to 12.2 m in August 1996. Therefore, to prove the reason for the increasing leachate level, we calibrated hydraulic conductivity of each waste andintermediate layer using the HELP (Hydrologic Evaluation ofLandfill Performance) model. The leachate generation data measured from February 1993 to October 1995 was used in the model calibration. As a result of a model calibration, we obtained anaverage infiltration ratio and used this in analysis of the total water balance to predict elevation of leachate level. Main causes of the elevation of the leachate level were the high water content of the waste and the degradation of the leachate-drainage system caused by the subsidence of a naturalbarrier layer. 相似文献
37.
Georgios D. Gikas Trisevgeni Yiannakopoulou Vassilios A. Tsihrintzis 《Environmental Modeling and Assessment》2006,11(3):219-233
SWAT ver. 2000 was used to predict hydrographs, and sediment, nitrate and total phosphorus loadings from a 1349 km2 mountainous/agricultural watershed in Northern Greece. The model was calibrated and verified using continuous meteorological
data from eight stations within the drainage area, and runoff, sediment and nutrient concentrations measured at nine stations
located within the main tributaries of the watershed, for the time period from May 1st, 1998 to January 31st, 2000. Model
validation methodology and resulting input parameters appropriate for Mediterranean drainage basins are presented. Predicted
by the model hydrographs, sedimentographs and pollutographs are plotted against observed values and show good agreement. Model
performance is evaluated using the root mean square error computation and scattergrams of predicted versus observed data.
The validated model is also used to test the effectiveness of three alternative cropping scenarios in reducing nutrient loadings
from the agricultural part of the watershed. The study showed that this model, if properly validated, can be used effectively
in testing management scenarios in Mediterranean drainage basins. 相似文献
38.
A study on the orbit of air temperature movement 总被引:1,自引:0,他引:1
Zong-Chang Yang 《Environmental Modeling and Assessment》2007,12(2):131-143
In this paper, we describe an air temperature movement by mapping its time series to the polar coordinates: the value of the
time series is plotted on the radial coordinate and the time on the angular coordinate. In this way, both the yearly and daily
air temperature movements from five different locations of China are used to demonstrate that, in an intuitionistic view,
air temperature movement is neither random nor chaotic, but has its own orbit. We then propose an elliptic orbit model for
the air temperature movement. Our proposed model provides quite good results when it is applied to the evaluation of yearly
air temperature movements in eight locations in various parts of the world, and the evaluation of daily air temperature movements
in five locations in Hunan Province of China on December 17, 2005. Results show that our approach provides a concise and helpful
model for air temperature analysis. 相似文献
39.
Land use change is an important topic in the field of global environmental change and sustainable development. Land use change
modeling has attracted substantial attention because it helps researchers understand the mechanisms of land use change and
assists regulatory bodies in formulating relevant policies. Maotiao River Basin is located in the province of Guizhou, China,
which has a developed agricultural industry in the karst mountain areas. This paper selected biophysical and social–economic
factors as independent variables, and constructed a multiple logistic regression of farmland spatial distribution probability
by random sampling. Then, by using GIS technology and integrating the 2000 data, this study predicted the farmland spatial
pattern. When the predicted map was compared with the actual farmland map for 2000, we noted that 71% of the simulation is
in accordance with the 2000 farmland pattern. The result satisfactorily proves the reasonability and applicability of our
model. 相似文献
40.
博斯腾湖水质矿化度模型及预测研究 总被引:6,自引:0,他引:6
根据博斯腾湖1985~1995年水质监测数据和出入湖水量等水文数据观测值,采用水质扩散模型和盐量平衡关系推导出博斯腾湖大湖区(简称博湖)水质矿化度模型,并预测了几种情况下博湖水质矿化度及近几年变化趋势,分析了影响博湖水质矿化度的主要因素,为博湖的近期和远期环境保护规划、环境管理等提供科学依据. 相似文献