全文获取类型
收费全文 | 551篇 |
免费 | 43篇 |
国内免费 | 181篇 |
专业分类
安全科学 | 58篇 |
废物处理 | 11篇 |
环保管理 | 90篇 |
综合类 | 364篇 |
基础理论 | 127篇 |
污染及防治 | 52篇 |
评价与监测 | 25篇 |
社会与环境 | 21篇 |
灾害及防治 | 27篇 |
出版年
2024年 | 3篇 |
2023年 | 13篇 |
2022年 | 26篇 |
2021年 | 28篇 |
2020年 | 33篇 |
2019年 | 26篇 |
2018年 | 29篇 |
2017年 | 23篇 |
2016年 | 34篇 |
2015年 | 31篇 |
2014年 | 31篇 |
2013年 | 42篇 |
2012年 | 43篇 |
2011年 | 55篇 |
2010年 | 29篇 |
2009年 | 28篇 |
2008年 | 20篇 |
2007年 | 25篇 |
2006年 | 29篇 |
2005年 | 25篇 |
2004年 | 13篇 |
2003年 | 30篇 |
2002年 | 22篇 |
2001年 | 18篇 |
2000年 | 14篇 |
1999年 | 16篇 |
1998年 | 13篇 |
1997年 | 13篇 |
1996年 | 15篇 |
1995年 | 8篇 |
1994年 | 8篇 |
1993年 | 3篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1975年 | 1篇 |
排序方式: 共有775条查询结果,搜索用时 15 毫秒
621.
利用生产模拟对青藏高原小麦高产原因的分析 总被引:1,自引:0,他引:1
在大量的实测资料基础上,通过模拟计算得到了在当前气候条件下、水肥适宜的青藏高原冬小麦干物质累积动态曲线。模拟计算表明:青藏高原夏季气候温凉,小麦生育期延长,因而干物质累积时间长,高原小麦高产主要以干物质累积时间长取胜,有利的夏季温度条件是高原小麦高产的最主要原因;青藏高原冬小麦干物质潜在产量可达32t/hm2·a,籽粒潜在产量可达144t/hm2·a,为平原的145倍。 相似文献
622.
电厂燃煤锅炉同时脱硫脱氮技术与分析 总被引:6,自引:0,他引:6
详细介绍几种典型电厂燃煤锅炉同时脱硫脱氮技术 ,并对其进行技术和经济比较。认为活性焦吸附法属于干法处理技术 ,最具有竞争力。 相似文献
623.
垃圾焚烧厂是一类对环境有重大影响的建设项目,在建设焚烧厂之前,必须进行环境影响评价.在借鉴国外相关资料的基础上,结合国内的实际情况,探讨了垃圾焚烧厂环境影响评价的主要步骤和主要内容. 相似文献
624.
本文探讨了灌溉水源限定条件下,农田灌溉时量优化计算方法,并以河北省运东地区3种主要作物为例进行了系统演算。从计算结果及其分析看,时量优化的经济效益明显,时量优化模型作为一种计算方法亦具有一定的实用意义。 相似文献
625.
苯并(a)芘(Bap)是强致癌物之一,主要来源为煤、石油等矿物性燃料及其他有机物的不完全燃烧。本文通过对包头市1991~2000年大气苯并芘监测结果的统计分析,揭示了其污染状况及变化趋势,从而说明包头市大气环境中Bap主要来源于燃煤。 相似文献
626.
Fabian P Kohlpaintner M Rollenbeck R 《Environmental science and pollution research international》2005,12(5):290-296
Background Biomass burning is a source of carbon, sulfur and nitrogen compounds which, along with their photochemically generated reaction
products, can be transported over very long distances, even traversing oceans. Chemical analyses of rain and fogwater samples
collected in the mountaineous rain forest of south Ecuador show frequent episodes of high sulfate and nitrate concentration,
from which annual deposition rates are derived comparable to those found in polluted central Europe. As significant anthropogenic
sources are lacking at the research site it is suspected that biomass burning upwind in the Amazon basin is the major source
of the enhanced sulfate and nitrate imput.
Methods Regular rain and fogwater sampling along an altitude profile between 1800 and 3185 m has been carried out in the Podocarpus
National Park close to the Rio SanFrancisco (3°58'S, 79°5'W) in southern Ecuador. pH values, electrical conductivity and chemical
ion composition were measured at the TUM-WZW using standard methods.
Results and Discussion Results reported cover over one year from March 2002 until May 2003. Annual deposition rates of sulfate were calculated ranging
between 4 and 13 kg S/ha year, almost as high as in polluted central Europe. Nitrogen deposition via ammonia (1.5–4.4 kg N/ha
year) and nitrate (0.5–0.8 kg N/ha year) was found to be lower but still much higher than to be expected in such pristine
natural forest environment. By means of back trajectory analyses it can be shown that most of the enhanced sulfur and nitrogen
deposition is most likely due to forest fires far upwind of the Ecuadorian sampling site, showing a seasonal variation, with
sources predominantly found in the East/NorthEast during January–March (Colombia, Venezuela, Northern Brazil) and East/SouthEast
during July–September (Peru, Brazil).
Conclusion Our results show that biomass burning in the Amazon basin is the predominant source of sulfur and nitrogen compounds that
fertilize the mountaineous rain forest in south Ecuador.
Recommendation and Outlook The mountaineous rain forest in south Ecuador has developed on poor and acid soils, with low nutrient availability. The additional
fertilization resulting from anthropogenic biomass burning constitutes a significant disturbance of this ecosystem, its functioning
and biodiversity. Thus it is planned to employ isotope analyses for quantifying the pathways of nitrate and sulfate deposition
in these natural forests. 相似文献
627.
628.
针对目前抗除草剂转基因作物基因流及其安全性评估方法存在的问题,提出了以亲和性为依据的抗性基因流的评估方法;同时以时间关系序列、空间关系序列和种群数量关系序列为原则,探讨了近缘种选择的标准。 相似文献
629.
Dieter Lietze 《Journal of Loss Prevention in the Process Industries》1995,8(6):319-324
This paper describes the results of extensive research to determine the limit of safety against flame transmission for sintered metal flame arrester elements when stressed by a flashback in a fuel-gas/oxygen mixture and when stressed through a stabilized burning of a flowing mixture of fuel-gas and air and of fuel-gas and oxygen at the sintered metal element. On the basis of the results of these investigations, the limit of safety against flame transmission for sintered metal flame arrester elements can be estimated and the conditions for testing can be specified. An analysis of the protection of gas outlets on gas distribution lines for welding, cutting and allied processes has been carried out, resulting in recommendations for necessary changes to the regulations for testing of safety devices with sintered metal flame arrester elements, which should be made in the next revision of the corresponding technical regulations for acetylene installations and calcium carbide stores (TRAC), and the standards DIN 8521, EN 730 and ISO 5175. 相似文献
630.