全文获取类型
收费全文 | 1025篇 |
免费 | 97篇 |
国内免费 | 209篇 |
专业分类
安全科学 | 178篇 |
废物处理 | 15篇 |
环保管理 | 115篇 |
综合类 | 410篇 |
基础理论 | 364篇 |
环境理论 | 1篇 |
污染及防治 | 91篇 |
评价与监测 | 17篇 |
社会与环境 | 115篇 |
灾害及防治 | 25篇 |
出版年
2024年 | 1篇 |
2023年 | 19篇 |
2022年 | 31篇 |
2021年 | 38篇 |
2020年 | 44篇 |
2019年 | 40篇 |
2018年 | 32篇 |
2017年 | 34篇 |
2016年 | 49篇 |
2015年 | 52篇 |
2014年 | 43篇 |
2013年 | 79篇 |
2012年 | 88篇 |
2011年 | 106篇 |
2010年 | 60篇 |
2009年 | 80篇 |
2008年 | 55篇 |
2007年 | 73篇 |
2006年 | 74篇 |
2005年 | 48篇 |
2004年 | 47篇 |
2003年 | 34篇 |
2002年 | 39篇 |
2001年 | 27篇 |
2000年 | 25篇 |
1999年 | 17篇 |
1998年 | 14篇 |
1997年 | 12篇 |
1996年 | 19篇 |
1995年 | 18篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1992年 | 8篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1984年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有1331条查询结果,搜索用时 685 毫秒
941.
水合电子(e-aq)是已知活性最强的还原物种之一.基于SO_3~(2-)受紫外光激发活化会释放e-aq的性质,提出了SO_3~(2-)/UV高级还原体系,用于降解稳定污染物.以7种卤乙酸为目标物,从卤素取代种类、卤代程度、实际水质本底影响等角度,考察了该体系对毒性卤代有机物(HOCs)的降解及脱卤效能,并探讨了相关机理.结果表明:HOCs的降解至少有直接光解和e-aq还原两条途径.卤素取代种类与卤化程度决定了HOCs的直接光解特性,其速率随氯、溴、碘取代顺序及卤化程度的增加而加快.SO_3~(2-)/UV体系显著提高了HOCs的降解及脱卤效率;对于直接光解慢的HOCs,其降解与脱卤主要由e-aq还原引起.SO_3~(2-)/UV体系在两种地表水质本底下仍具有较高的脱卤效能. 相似文献
942.
Aniek Hebinck Francesca Galli Sabrina Arcuri Brídín Carroll Deirdre O’Connor Henk Oostindie 《Local Environment》2018,23(4):398-413
The food system’s decreasing ability to deliver food security has led to the emergence of food assistance initiatives. Food assistance is highly contested; as some argue, it is a “failure of the state”, while others regard food assistance to be an “extension of the welfare state”. Either way, research suggests that actors within food assistance are rethinking their role in the food system. In this paper, we study three food assistance initiatives, in the Netherlands, Italy and Ireland, that perform new food assistance practices while embedded in specific institutional contexts, and analyse their potential to transform the food system, drawing on Transformative Social Innovation theory. Building on transition and social innovation theory, this recently developed theory distinguishes different levels within systems, named “shades of change”, that are associated with societal transformation. By exploring these “shades” of change in the analysis, we describe aspects of the initiatives’ novel practices, and in relation to the initiative and institutional relations their motivations and expectations. We compare the three cases and discuss how food assistance practices relate to and change (or do not change) the food system. In particular, we elaborate on how these three food assistance initiatives contribute in various ways to local food and welfare system innovation. In doing so, we offer a novel perspective on food assistance initiatives. We argue that they show dynamics that have the potential for more substantial transformation towards food security over time, by building momentum through “small wins”. 相似文献
943.
本研究采用便携式温室气体分析仪连接通量箱在线监测杭州西溪湿地CH_4、CO_2通量日变化及季节变化,同时也对包括有机碳含量、湿度、孔隙度、比重、p H、Eh在内的潜在影响因子进行了研究。结果表明,通常情况下,CH_4、CO_2通量的变化分别为-0.001 9~0.035 3mg/(m~2·h)和-109.76~442.55mg/(m~2·h);CH_4、CO_2通量的变化存在明显正相关关系。CH_4通量的季节变化表现为夏季秋季春季冬季;CO_2通量的季节变化表现为夏季春季冬季秋季。土壤湿度是影响CH_4通量变化的重要因子,通常湿度越大,CH_4通量越大;在生长季维管植物有助于CH_4的氧化;西溪湿地土质差异也使CH_4、CO_2通量排放有所差异,具体表现在土壤有机碳含量相差较大,而土壤中有机碳的含量与CH_4产生潜力呈显著正相关。 相似文献
944.
945.
重大事故动力学演化 总被引:2,自引:13,他引:2
刘铁民 《中国安全生产科学技术》2006,2(6):3-6
为进一步研究重大事故发生演化机理,在对典型重特大事故比较研究的基础上,应用系统动力学理论分析重大事故孕育、发生、发展和激变的动力学特征,认识重大事故行为过程及其主要影响因素,探讨重大事故闭环反馈系统的调控规律。作者建议应用系统动力学理论与方法建立决策实验室,以提高对重大事故风险控制水平。 相似文献
946.
Chao‐Hsien Liaw Liang‐Ching Chen Li‐Mei Chan 《Journal of the American Water Resources Association》2006,42(3):593-601
ABSTRACT: This work establishes an industrial water demand (IWD) model for a short term estimate, which considers water reuse technologies and discharge regulations, for the integrated circuit (IC) industry in northern Taiwan. Based on the optimization of an industrial water cost system, a computerized system dynamics model (SD model) is developed to generate individual firm IWD using data from year 2000. A market IWD is further constructed for 25 1C firms in the study area and is approximated by an inverse logistic curve. Analytical results demonstrate that price elasticity varies with water price in cases involving water reuse. 相似文献
947.
K.B McGrattan 《Spill Science & Technology Bulletin》2003,8(4):367-372
A combination of numerical modeling and large-scale experimentation has yielded a tremendous amount of information about the structure, trajectory and composition of smoke plumes from large crude oil fires. A numerical model, a large outdoor fire plume trajectory (ALOFT), has been developed at NIST to predict the downwind concentration of smoke and other combustion products. The model is based on the fundamental conservation equations that govern the introduction of hot gases and particulate matter from a large fire into the atmosphere. The model has been used to estimate distances from fires under of variety of meteorological and topographic conditions where ground level concentrations of smoke and combustion products fall below regulatory threshold levels. 相似文献
948.
949.
a production in the central, south central, and the south segments of the lagoon. In a system as large and complex as the lagoon,
N and P limitations are potentially subject to significant spatial and temporal variability. Total Kjeldahl nitrogen (TN)
was higher in the north (1.25 mg/liter) and lower in the south (0.89 mg/liter). The reverse pattern was observed for total
P (TP), i.e., lowest in the north (0.03 mg/liter) and highest at the south (0.14 mg/liter) ends of the IRL. This increased
P concentration in the SIRL appears to have a significantly large effect on chlorophyll a production compared with the other segments, as indicated by stepwise regression statistics. This relationship can be expressed
as follows: South IRL [chlorophyll a] =−8.52 + 162.41 [orthophosphate] + 7.86 [total nitrogen] + 0.38 [turbidity]; R
2= 0.98**. 相似文献
950.
Microbial population dynamics and changes in main nutrients during the
acidification process of pig manures 总被引:1,自引:1,他引:0
Dongdong Zhang Xufeng Yuan Peng Guo Yali Suo Xiaofen Wang Weidong Wang Zongjun Cui 《环境科学学报(英文版)》2011,23(3):497-505
This study evaluated the impact of pig manure acidification on anaerobic treatment and composition of the fecal microbial community.According to the different chemical oxygen demand (COD) in the anaerobic treatment processes,pig manure was diluted 4 times (×4),16 times (×16),or 64 times (×64) and subjected to acidification.During the acidification process,pH,soluble chemical oxygen demand (SCOD),volatile fatty acids (VFAs),nitrogen (N),phosphorus (P) and potassium (K) were determined along with microbial po... 相似文献