全文获取类型
收费全文 | 641篇 |
免费 | 95篇 |
国内免费 | 133篇 |
专业分类
安全科学 | 133篇 |
废物处理 | 22篇 |
环保管理 | 55篇 |
综合类 | 420篇 |
基础理论 | 101篇 |
污染及防治 | 51篇 |
评价与监测 | 22篇 |
社会与环境 | 23篇 |
灾害及防治 | 42篇 |
出版年
2024年 | 4篇 |
2023年 | 13篇 |
2022年 | 24篇 |
2021年 | 42篇 |
2020年 | 31篇 |
2019年 | 40篇 |
2018年 | 31篇 |
2017年 | 29篇 |
2016年 | 33篇 |
2015年 | 31篇 |
2014年 | 32篇 |
2013年 | 43篇 |
2012年 | 44篇 |
2011年 | 48篇 |
2010年 | 38篇 |
2009年 | 43篇 |
2008年 | 31篇 |
2007年 | 50篇 |
2006年 | 37篇 |
2005年 | 51篇 |
2004年 | 14篇 |
2003年 | 28篇 |
2002年 | 20篇 |
2001年 | 20篇 |
2000年 | 19篇 |
1999年 | 11篇 |
1998年 | 9篇 |
1997年 | 8篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有869条查询结果,搜索用时 15 毫秒
391.
The results of comprehensive morphophysiological and population studies on Ajuga reptansL., a species of the nemoral floristic complex, at the northern boundary of its range (in the middle taiga subzone of the Komi Republic) are reviewed. Adaptations at the cell, organism, and biocenotic levels are revealed. The maintenance and survival of the species at the boundary of its range are provided for by its physiological plasticity, resistance to low temperatures, and multiple variants of ontogeny. Prognosis of Ajuga reptansfuture status under conditions of global climate change and expansion of anthropogenically disturbed areas is favorable. 相似文献
392.
In order to evaluate the flame-retardant capacity of KHCO3 and ABC on the ignition of PMMA dust layer accumulation on hot surfaces, the ignition time and critical heating temperature of PMMA/KHCO3 and PMMA/ABC dust layer were experimentally investigated. The thermal stability of the mixed dust, the condensed phase products and gas phase products of the mixed dust combustion were analyzed to reveal the flame-retardant mechanism. The ignition time of 30 μm PMMA was obviously longer than that of 5 μm PMMA, and the critical heating temperature was close to that of 5 μm PMMA. KHCO3 and ABC could greatly extend the ignition time of the PMMA dust layer and increase the critical heating temperature of the dust layer. ABC was more effective than KHCO3. The decomposition of KHCO3 and ABC absorbed the heat and inhibits the pyrolysis of PMMA. The HPO3 and P2O5 generated by the decomposition of ABC would cover the surface of PMMA aggregates or particles and act as a physical barrier. The main light combustible gas produced by PMMA pyrolysis were CO and C2H4. The CO2 generated during the decomposition of KHCO3 could dilute the combustible gas in the ambient to inhibit the combustion of PMMA. 相似文献
393.
Ivan Dolezal Kausik Bal 《International journal of occupational safety and ergonomics》2019,25(4):562-567
Measurement of thermal resistance of polymer sheets and fibrous layers is important in various applications including those within the engineering, ergonomics, clothing design and personal protective equipment fields. Standard methods for measurement of thermal resistance of plain materials are generally time consuming, expensive and often require the sample to be cut. Moreover, the temperature difference between the surfaces of both plates surrounding the sample must be known, as well as the sample thickness. This article describes a new measuring device named the Thermoscope. The Thermoscope is not limited by the aforementioned requirements and is able to evaluate the thermal resistance of polymer sheets and textiles by touching the sample on one surface alone. Simultaneously, the other surface is kept in thermal contact with the supporting base. The accuracy of this device was compared with the Alambeta thermal insulation tester. Effects of various base materials on measurement precision were also studied. 相似文献
394.
本文通过对KZ1床层、KZ2床层、KZ1和KZ2复合床层在不同床层厚度条件下,对氯化氰蒸气的动活性进行对比试验,并对试验结果进行分析,得出了后者并非前两者之和,而有了大幅提高的结论。 相似文献
395.
396.
渤海西部局地大雾变化趋势及成因分析 总被引:1,自引:0,他引:1
利用2002-2012年秦皇岛地区4个气象站大雾监测及Micaps 3.0常规资料,对比分析卢龙与沿海站大雾的时空尺度分布特征,对大雾持续时间、日数进行跨月、跨年统计,从中筛选出189个样本个例进行变化趋势分析。对典型17个过程个例按能见度大小进行3级设定,对应其同步天气背景,分析大雾偏多的成因。 相似文献
397.
通过分析秦皇岛地区水资源及人均占有率、气候干旱化之现状及秦皇岛地区降水的特点,发现秦皇岛降水有明显日变化特征(凌晨1~2时和傍晚17~18时降水量较大)。从化学制剂的选择、碘化银成核环境确定、积云增雨的高度判断三个方面提出了人工增雨作业条件,在作业实践中取得了良好效果。 相似文献
398.
Ilaria Salvadori 《Local Environment》2013,18(1):87-91
There are now numerous sustainable development evaluation methods to evaluate sustainable development progress. Which one to use will depend on the resources, the goals and the stakeholders. Ideally the method selected and its indicators would themselves indicate how to achieve sustainable development. Such a choice can be difficult without a framework to help ensure the representation of the essential elements of sustainable development. This paper presents such a framework by drawing on ecological terminology to define aspects of sustainable development as manifested in the natural world. Examples of how these can be measured are provided along with an explanation of how the components of the framework contribute to achieving sustainable development in social systems. 相似文献
399.
400.
A. Dandou E. Bosioli M. Tombrou N. Sifakis D. Paronis N. Soulakellis D. Sarigiannis 《Water, Air, & Soil Pollution: Focus》2002,2(5-6):17-28
In the present study the horizontal distribution of columnar aerosol optical thicknessderived at high spatial resolution from Earth observation satellite data in the Lombardy area (Italy) was converted to the horizontal distribution of optically effective aerosols concentration at the ground level. This was achieved by incorporating information on atmosphere's mixing height, at which pollutants released at ground level are vertically dispersed by convection or mechanical turbulence. The resulted fields compared favourably to pollutant concentration measurements provided by the ground stations. These results show that it is possible to calculate mean concentration fields by using the spatial distribution of aerosol optical thickness (AOT) measured by satellite normalized by the atmospheric mixing height. The advantage of satellites in measuring AOT is that they can capture all actual emissions compared to the models, which are based on inventoried data. 相似文献