全文获取类型
收费全文 | 774篇 |
免费 | 62篇 |
国内免费 | 88篇 |
专业分类
安全科学 | 85篇 |
废物处理 | 10篇 |
环保管理 | 201篇 |
综合类 | 309篇 |
基础理论 | 128篇 |
污染及防治 | 44篇 |
评价与监测 | 86篇 |
社会与环境 | 41篇 |
灾害及防治 | 20篇 |
出版年
2024年 | 3篇 |
2023年 | 15篇 |
2022年 | 14篇 |
2021年 | 28篇 |
2020年 | 30篇 |
2019年 | 28篇 |
2018年 | 26篇 |
2017年 | 26篇 |
2016年 | 40篇 |
2015年 | 30篇 |
2014年 | 50篇 |
2013年 | 58篇 |
2012年 | 58篇 |
2011年 | 65篇 |
2010年 | 44篇 |
2009年 | 37篇 |
2008年 | 35篇 |
2007年 | 50篇 |
2006年 | 49篇 |
2005年 | 35篇 |
2004年 | 24篇 |
2003年 | 20篇 |
2002年 | 21篇 |
2001年 | 20篇 |
2000年 | 21篇 |
1999年 | 10篇 |
1998年 | 10篇 |
1997年 | 12篇 |
1996年 | 12篇 |
1995年 | 10篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1972年 | 1篇 |
排序方式: 共有924条查询结果,搜索用时 203 毫秒
611.
The uncertainty of reported greenhouse gases emission inventories obtained by the aggregation of partial emissions from all
sources and estimated to date for several countries is very high in comparison with the countries’ emissions limitation and
reduction commitments under the Kyoto Protocol. Independent calculation of the estimates could confirm or question the undertainty
estimates values obtained thus far. One of the aims of this paper is to propose statistical signal processing methods to enable
calculation of the inventory variances. The annual reported emissions are used and temporal smoothness of the emissions curve
is assumed. The methods considered are: a spline-function-smoothing procedure; a time-varying parameter model; and the geometric
Brownian motion model. These are validated on historical observations of the CO2 emissions from fossil fuel combustion. The estimates of variances obtained are in a similar range to those obtained from
national inventories using TIER1 or TIER2. Additionally, some regularities in the observed curves were noticed. 相似文献
612.
Optimization of the Resources Management in Fighting Wildfires 总被引:1,自引:0,他引:1
Wildfires lead to important economic, social, and environmental losses, especially in areas of Mediterranean climate where
they are of a high intensity and frequency. Over the past 30 years there has been a dramatic surge in the development and
use of fire spread models. However, given the chaotic nature of environmental systems, it is very difficult to develop real-time
fire-extinguishing models. This article proposes a method of optimizing the performance of wildfire fighting resources such
that losses are kept to a minimum. The optimization procedure includes discrete simulation algorithms and Bayesian optimization
methods for discrete and continuous problems (simulated annealing and Bayesian global optimization). Fast calculus algorithms
are applied to provide optimization outcomes in short periods of time such that the predictions of the model and the real
behavior of the fire, combat resources, and meteorological conditions are similar. In addition, adaptive algorithms take into
account the chaotic behavior of wildfire so that the system can be updated with data corresponding to the real situation to
obtain a new optimum solution. The application of this method to the Northwest Forest of Madrid (Spain) is also described.
This application allowed us to check that it is a helpful tool in the decision-making process. 相似文献
613.
Sewage discharge from an ocean outfall is subject to water quality standards, which are often stated in probabilistic terms.
Monte Carlo simulation (MCS) has been used in the past to evaluate the ability of a designed outfall to meet water quality
standards or compliance guidelines associated with sewage discharges. In this study, simpler and less computer-intensive probabilistic
methods are considered. The probabilistic methods evaluated are the popular mean first-order second-moment (MFOSM) and the
advance first-order second-moment (AFOSM) methods. Available data from the Spaniard's Bay Outfall located on the east coast
of Newfoundland, Canada, were used as inputs for a case study. Both methods were compared with results given by MCS. It was
found that AFOSM gave a good approximation of the failure probability for total coliform concentration at points remote from
the outfall. However, MFOSM was found to be better when considering only the initial dilutions between the discharge point
and the surface. Reasons for the different results may be the difference in complexity of the performance function in both
cases. This study does not recommend the use of AFOSM for failure analysis in ocean outfall design and analysis because the
analysis requires computational efforts similar to MCS. With the advancement of computer technology, simulation techniques,
available software, and its flexibility in handling complex situations, MCS is still the best choice for failure analysis
of ocean outfalls when data or estimates on the parameters involved are available or can be assumed. 相似文献
614.
Soil pollution data is also strongly scattering at small scale. Sampling of composite samples, therefore, is recommended for pollution assessment. Different statistical methods are available to provide information about the accuracy of the sampling process. Autocorrelation and variogram analysis can be applied to investigate spatial relationships. Analysis of variance is a useful method for homogeneity testing. The main source of the total measurement uncertainty is the uncertainty arising from sampling. The sample mass required for analysis can also be estimated using an analysis of variance. The number of increments to be taken for a composite sample can be estimated by means of simple statistical formulae. Analytical results of composite samples obtained from different fusion procedures of increments can be compared by means of multiple mean comparison. The applicability of statistical methods and their advantages are demonstrated for a case study investigating metals in soil at a very small spatial scale. The paper describes important statistical tools for the quantitative assessment of the sampling process. Detailed results clearly depend on the purpose of sampling, the spatial scale of the object under investigation and the specific case study, and have to be determined for each particular case. 相似文献
615.
616.
Bruce W. Lium W. Thomas Shoaf 《Journal of the American Water Resources Association》1980,16(2):359-360
ABSTRACT: Nine samples, each with different kinds and numbers of algae, were filtered at five pressures from 5 to 75 pounds per square inch and the amounts of chlorophylls a and b were measured. Pressures in the range tested had no effect on the measured amounts. 相似文献
617.
Water quality criteria were developed for delivery waters to Everglades National Park. The park receives a minimum of 12.34 m3/sec (315,000 acre-ft/yr) of water from controlled sources external to its boundary. These waters often originate from areas that are or potentially are impacted from urban and agricultural developments. When, in 1970, the U.S. Congress guaranteed minimum water deliveries to Everglades National Park, it also required that these waters be of good quality.The Everglades National Park water quality data base was analyzed from 1970 to 1978 at both in-park and water delivery sites to determine the current level of delivery water quality and to select representative delivery sites. It was found that current delivery water quality was sufficiently high to be adopted as criteria against which future water quality could be compared. From the delivery sites S-12C and L-67A all data were combined from 1970–1978 for 36 parameters including macronutrients, heavy metals, and field parameters such as DO, pH, and specific conductance. Mean concentrations and upper limits were computed and tabulated for comparison during future monitoring programs. These criteria were subsequently adopted through a joint memorandum of agreement between the U.S. Army Corps of Engineers, South Florida Water Management District and the U.S. National Park Service. 相似文献
618.
过硫酸盐具有强氧化性、易溶于水、较稳定、易运输等特点,活化后的过硫酸盐可以产生具有强氧化性的SO-4·,适用于氧化降解各种有机污染物,在污染土壤修复、地下水修复处理等环境污染修复治理领域具有广阔的应用前景。分析了光、热、过渡金属离子、强碱以及强氧化剂等不同条件下活化过硫酸盐的国内外研究进展,并就活化方式的选择与有机物结构特点之间的关系进行探讨,对其在土壤污染修复治理领域的应用进行了展望。 相似文献
619.
土壤中重金属生物有效性研究 总被引:1,自引:0,他引:1
土壤重金属污染问题是当前主要的环境问题,结合中国人多耕地少的国情,中国面临的土壤环境安全问题更加严峻.已有大量实验研究表明,土壤环境中能被生物吸收利用的重金属才是衡量重金属元素对生态环境影响的关键参数.文章在分析国内外土壤重金属生物有效性相关文献的基础上,介绍了生物有效性的定义以及影响土壤重金属生物有效性的因素,讨论了两种常用研究土壤有效态重金属方法(化学提取法和生物学评价法)的原理和优缺点,在此基础上,提出今后的研究方向,以供研究者参考. 相似文献
620.
政府和民众对于城市环境事件的关注越来越高,树立典型是激励良性发展的有效手段。为了提高年度城市环境事件评选的科学性和合理性,本文提出定量和定性相结合的评选方法,包含事件收集、事件筛选、事件评定三个阶段。在此基础上,对2016年度中国城市环境保护十大事件进行了评选,无锡、贵溪、三亚、珠海的案例分别代表了水、土、气、生4个专项领域环境治理和保护的先进典型;杭州、深圳、三沙的案例分别体现了以大型赛事活动为契机开展城市综合环境整治的先进经验,以及市场化的治理手段和生态技术对于城市综合治理的重要性;上海(崇明)、重庆、鄂尔多斯(库布齐地区)代表了因地制宜的区域生态文明发展模式。通过案例分析,得出如下启示:提升环境治理成效应该兼顾责任制、市场化、民主化的管理模式创新和各种技术创新;生态环境要素应该被视为城市发展的新兴增长点;城市环境保护行为具有发展和再分配双重属性,环保行为的发展属性仍有待于继续普及,而先行城市应该借鉴典型经验,积极探索通过环境保护实现经济发展的新模式。 相似文献