全文获取类型
收费全文 | 824篇 |
免费 | 73篇 |
国内免费 | 185篇 |
专业分类
安全科学 | 127篇 |
废物处理 | 23篇 |
环保管理 | 121篇 |
综合类 | 433篇 |
基础理论 | 170篇 |
污染及防治 | 70篇 |
评价与监测 | 36篇 |
社会与环境 | 69篇 |
灾害及防治 | 33篇 |
出版年
2024年 | 3篇 |
2023年 | 6篇 |
2022年 | 28篇 |
2021年 | 24篇 |
2020年 | 31篇 |
2019年 | 25篇 |
2018年 | 33篇 |
2017年 | 35篇 |
2016年 | 38篇 |
2015年 | 47篇 |
2014年 | 49篇 |
2013年 | 72篇 |
2012年 | 71篇 |
2011年 | 86篇 |
2010年 | 57篇 |
2009年 | 75篇 |
2008年 | 50篇 |
2007年 | 67篇 |
2006年 | 45篇 |
2005年 | 37篇 |
2004年 | 27篇 |
2003年 | 12篇 |
2002年 | 26篇 |
2001年 | 16篇 |
2000年 | 23篇 |
1999年 | 26篇 |
1998年 | 18篇 |
1997年 | 9篇 |
1996年 | 8篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1987年 | 2篇 |
1985年 | 1篇 |
1982年 | 2篇 |
1981年 | 7篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1975年 | 2篇 |
排序方式: 共有1082条查询结果,搜索用时 484 毫秒
61.
Critical review of Integrated Water Resources Management: Moving beyond polarised discourse 总被引:1,自引:0,他引:1
Integrated Water Resource Management (IWRM) emerged as a popular concept in the water sector in the 20th century. From a highly techno-centric approach in the past, it has taken a new turn embracing Habermasian communicative rationality as a place-based nexus for multiple actors to consensually and communicatively integrate decisions in a hydrological unit. The 'how to integrate' approach had remarkable appeal worldwide in promoting authentic participation of all stakeholders. However, critics argue that the domain of water resource management is a political process of contestation and negotiation; the emphasis is on complexities, contextuality, power dynamics and the importance of analysing real world situations. They demonstrate 'how integration cannot be achieved' given the power dynamics in social interactions. These apparently contradictory discourses draw on different theoretical paradigms and polarise the discourse on IWRM, without offering constructive alternatives. To this end, this paper offers an option to complement this polarised discourse by examining 'how integration actually does take place' in a strategic context thereby facilitating consensual decisions to integrate water management for a sustainable future. 相似文献
62.
氰化物测定机理的研究 总被引:1,自引:0,他引:1
研究了酒石酸-硝酸锌法提取易释放氰化物,磷酸-EDTA提取总氰的机理;对异烟酸-吡唑啉酮光度法测定氰化物的条件作了探讨。 相似文献
63.
64.
Hans Preusting Jaap Kingma Gjalt Huisman Alexander Steinbüchel Bernard Witholt 《Journal of Polymers and the Environment》1993,1(1):11-21
WhenPseudomonas oleovorans (GPo1) is grown on sodium octanoate under ammonium limiting conditions, it is able to accumulate a copolyester consisting of medium chain length 3-hydroxyalkanoic acids (PHAm). 3-Hydroxybutyrate is only incorporated in trace amounts. WhenP. oleovorans is equipped with the PHB biosynthetic genes ofAlcaligenes eutrophus (GPo1[pVK101::PP1]), it forms a polyester containing major amounts of 3-hydroxybutyrate. The resulting polymer however is a blend of PHAm and PHB, rather than a copolymer of 3-hydroxybutyrate and medium chain length 3-hydroxyalkanoic acids [11]. To establish whether PHAm and PHB molecules are stored in the same or separate granules by this recombinantP. oleovorans strain, we studied polymer forming cells by freeze-fracture electron microscopy. This approach is possible because previous freeze-fracture electron microscopy studies on PHAm and PHB accumulating strains have shown that PHAm and PHB granules can be distinguished from each other: PHAm granules from mushroom-like structures, whereas PHB granules from needle structures during freeze-fracturing. In this paper we show that stationary phase cells of GPo1[pVK101::PP1] contained both mushroom and needle-like structures, indicating that PHAm and PHB chains were stored in separate granules. To be able to determine whether the separation of PHAm and PHB is complete, the respective granules were separated on sucrose gradients. A total cell extract of GPo1[pVK101::PP1] which was subjected to sucrose gradient centrifugation revealed two white bands of different densities: the upper band with a density of 1.05 g/mL consisted exclusively of PHAm granules, while the lower band with a density of 1.19 g/mL consisted of PHB granules only. Thus, when bacteria synthesize both PHAm and PHB, the resulting polymer chains are segregated completely and stored in separate granules. 相似文献
65.
揭开武汉东湖蓝藻水华消失之谜 总被引:115,自引:3,他引:112
水华(亦称湖靛)是湖泊富营养化最恶劣的表征之一。武汉东湖70年代至1984年间每年夏季出现蓝藻水华,1985年起突然消失,至今已有14年没有重现,原因何在?通过三次设在湖里的围隔试验,证明鲢鳙的大量放养,是水华消失的决定性因素。 相似文献
66.
Investigation of sustainable energy alternatives for powering remote communities in northern Ontario
ABSTRACT Remote communities in the North of Ontario survive in isolation as their proximity to the southern industrial sector of the province limits their accessibility to the major grid. The lack of grid connection has led to antiquated methods of power generation which pollute the environment and deplete the planet of its natural resources. Aside from the primary means of electricity generation being by diesel generators, generation infrastructure is deteriorating due to age and the stagnation of the power supply has led to communities facing load restrictions. These challenges may be resolved by introducing clean energy alternatives and providing a fuel blend option. The primary energy sources investigated in this research are solar, wind, and hydrogen. To assess the viability of these energy production methods in Northern communities, an exergy analysis is employed as it utilizes both the first and second law of thermodynamics to determine systems’ efficiency and performance in the surroundings. Local weather patterns were used to determine the viability of using wind turbines, solar panels and/or hydrogen fuel cells in a remote community. Through analysis of the resources available at the community, it was determined that the hydrogen fuel cell was best suited to provide clean energy to the community. Wind resulted in low efficiency in the range of 2–3% while solar efficiencies resulted in ranges of 18 – 19%, as the seasonal variations between the three years is not very great. Due to the higher operating efficiencies observed of the PV panels it would also be an attractive alternative to diesel generators however, the lack of consistent operation above 30% efficiency throughout the year, resulted in hydrogen fuel cells being a better alternative. 相似文献
67.
Anderson AB 《Environmental management》2002,29(3):428-436
The Land Condition Trend Analysis (LCTA) program is the US Army's standard for land inventory and monitoring, employing standardized
methods of natural resources data collection, analyses, and reporting designed to meet multiple goals and objectives. Critical
to using LCTA data in natural resources management decisions is the ability of the LCTA protocols to detect changes in natural
resources. To quantify the ability of LCTA protocols to detect resource changes, power analysis techniques were used to estimate
minimum detectable effect sizes (MDES) for selected primary and secondary management variables for three Army installations.
MDES for a subset of primary variables were estimated using data from 27 installation LCTA programs. MDES for primary and
secondary variables varied widely. However, LCTA programs implemented at larger installations with lower sampling intensities
detected changes in installation resources as well as programs implemented at smaller more intensively sampled installations.
As a national monitoring program that is implemented at individual installations, LCTA protocols provide relatively consistent
monitoring data to detect changes in resources despite diverse resource characteristics and implementation constraints. 相似文献
68.
川中丘陵区村级景观土壤有机碳密度和储量分析 总被引:1,自引:0,他引:1
本文综合运用了地理信息系统(GIS)、遥感(RS)和全球卫星定位系统(GPS)等技术手段,分析了人口密集的川中丘陵乡村区域土壤有机碳密度(SOCD)和储量(SOCS)的空间分布及影响因素。结果表明,区域内SOCD和SOCS平均值分别为5.58kg/m2和75.77×105g,SOCD随丘体高度的降低向四周逐渐增大,SOCS主要分布于旱地、水田等土地利用类型中。0~30cm土层和土体深度内,SOCD以冬水田最高,裸岩最低;SOCS则以丘脚旱地和轮作水田最高,裸岩最低。地形、土地利用和土地覆盖对SOCD、SOCS影响明显。 相似文献
69.
70.
以市售无机膨胀型AB牌防火涂料为研究基础,复合了膨胀阻燃剂(APP-MEL-PER阻燃体系)、抑烟剂和助剂,进行了新型防火涂料的制备,当膨胀阻燃体系(APP-MEL-PER阻燃体系)以17∶6∶6的配比混合于该涂料中,其所占质量百分比为19%的时,防火性能最好。测试表明,该新型防火涂料烟密度等级6.77,指数下降了10,接近于国家标准1级。在248℃~400℃期间失重仅为12%,在390℃,有强烈的吸收峰,也表现了优异的阻燃性能。实现了APP-MEL-PER膨胀阻燃剂和AB牌涂料优配的目的。 相似文献