首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   528篇
  免费   48篇
  国内免费   182篇
安全科学   47篇
废物处理   19篇
环保管理   110篇
综合类   315篇
基础理论   94篇
污染及防治   104篇
评价与监测   31篇
社会与环境   36篇
灾害及防治   2篇
  2024年   6篇
  2023年   17篇
  2022年   24篇
  2021年   39篇
  2020年   24篇
  2019年   14篇
  2018年   26篇
  2017年   25篇
  2016年   29篇
  2015年   28篇
  2014年   40篇
  2013年   81篇
  2012年   46篇
  2011年   47篇
  2010年   30篇
  2009年   32篇
  2008年   27篇
  2007年   38篇
  2006年   30篇
  2005年   20篇
  2004年   24篇
  2003年   21篇
  2002年   17篇
  2001年   16篇
  2000年   11篇
  1999年   4篇
  1998年   7篇
  1997年   9篇
  1996年   7篇
  1995年   5篇
  1994年   2篇
  1993年   3篇
  1992年   5篇
  1991年   1篇
  1990年   2篇
  1979年   1篇
排序方式: 共有758条查询结果,搜索用时 953 毫秒
491.
The study was conducted to investigate people’s forest dependency and contributions of forests to the livelihoods in the three hill districts of Chittagong Hill Tracts (CHT), Bangladesh. The study revealed that forest resources contribute significantly to rural community’s livelihoods and economic well-being. Using generalized logistic regressions, this study has also investigated the socioeconomic factors that affect people’s dependency on forest resources of CHT. The study revealed that people’s income from forest and forest-related occupation was positively aligned with their forest dependency. However, their education level significantly reduced their dependency on forest resources. Thus, educating the forest-dependent people and supporting alternative income generation activities should be appreciated for effective forest management in CHT. This study will be helpful to forest and environmental policy makers for CHT.  相似文献   
492.
对激发粉煤灰活性的方法(物理活化和化学活化)进行了探讨,提出了一种能够大幅度提高粉煤灰活性的有效方法——细磨和化学激发复合方法。用此法活化粉煤灰制得的诺砂制品,其早期强度显著提高。同时对其活化机理进行了分析。  相似文献   
493.
The results of a co-ordinated monitoring programme for pesticide residues in the European Union and Norway carried out in 1996 and 1997 are presented. The aim of this programme is to work towards a system, which makes it possible to estimate actual dietary pesticide intake for the population of the European Union. Based on a statistically dérived sampling plan and within the limited number of pesticides/commodities analysed, the most critical pesticides (benomyl group and dithiocarbamates) and commodities (mandarine and lettuce) were identified. In case of detected non-compliances, repeated sampling and, if necessary, enforcement actions are to be taken by national authorities. The programme will be continued in the next years.  相似文献   
494.
Consumer products are important sources of human exposure to certain chemicals. Recent regulatory requirements for assessing human exposure to three glycol ethers, namely 2-methoxyethanol (ME), 2-ethoxyethanol (EE) and 2-butoxyethanol (BE), have prompted the investigation of these chemicals in consumer products and their emission characteristics. Thirteen products were selected for investigation based on their potential of containing the chemicals. Headspace results indicated that ME and EE were not present in any of the 13 selected products, while BE was detected in the headspace samples of seven products, of which five were household cleaning agents. Other related compounds such as 2-hexyloxyethanol (HE) and 2-(2-butoxyethoxy)ethanol (BEE) were also detected in the headspace samples of some products. BE emissions from five cleaning related products were measured using a field and laboratory emission cell (FLEC) with its subunit to provide emission data for inhalation exposure assessment purposes. These products had initial emission factors ranging from 145 to 938 mg m(-2) h(-1) under the experimental conditions. It was found that the emission factor of BE was inversely proportional to the dilution factor of the products. A good relationship was established between the emission factor of BE and its concentrations in water-based products. Based on product use scenarios developed by US EPA and an assumed "standard room," average daily inhalation exposure levels of a resident as a result of performing cleaning tasks were estimated to be 0.075 and 0.186 mg (kg b.w.)(-1) day(-1) for two all-purpose spray cleaners, and 0.004 and 0.006 mg (kg b.w.)(-1) day(-1) for two-spray glass cleaners, respectively.  相似文献   
495.
21世纪以来 ,我国的肉制品产销量一直保持着强劲的增长势头 ,将成为居民的肉类消费主流。现阶段 ,国内肉制品物流的每一个环节都可能因温度变化、微生物侵蚀、有害物质污染等使肉制品对人体产生毒害 ,特别是肉制品销售物流安全直接关系广大消费者的利益。为此 ,在肉制品加工企业销售物流现场调研基础上 ,重点分析了肉制品销售物流过程中的安全隐患 ,并根据肉制品的产品特性和销售物流特性研究成果 ,提出肉制品销售物流的安全管理对策。  相似文献   
496.
The increasing production of computers, the progress in their performance, and the shorter time between innovation and production has led to increasing numbers of obsolete products. It has thus become necessary to recover some materials from old computers and to protect the environment from a new type of pollution. Such recycling is difficult because of the diversity of polymeric materials used, e.g., thermoplastics (polystyrene or acrylonitrile-butadiene-styrene) and thermosets (epoxy resins), and the relatively high levels of flame retardants (halogen- and nitrogen-containing compounds) added during production. Pyrolysis seems to be a suitable way to recover materials and energy from such waste without component separation if an efficient method for reducing toxic compounds can be applied. In this study, the pyrolysis of plastic and thermoset fractions (keyboards, casings, printed circuit boards, and mixtures thereof) of used computers was studied by thermogravimetry and batch reactor pyrolysis. The degradation products were separated into three fractions, solid, liquid, and gaseous, each of them being characterized by suitable methods such as gas chromatography (GC-MSD, gas chromatography-mass spectrometry detection; GC-AED, gas chromatography-atomic emission detection), infrared (FT-IR) and 1H-NMR (nuclear magnetic resonanace) spectroscopy, and elemental analysis. It has been established that most of the halogens, nitrogen, and sulfur is concentrated in the residue. However, the elimination of hazardous toxic compounds, mainly those containing bromine, is necessary before being able to safely use the pyrolysis oils as fuels or in refinery or petrochemical industry flows.  相似文献   
497.
农产品物流组织形式及其发展趋势   总被引:1,自引:0,他引:1  
阐述了农产品物流组织的内涵和组织形式,提出了农产品物流组织发展的主流方向是第三方物流企业,发展的切入重点是农产品配送中心组织,发展的新趋势是农产品虚拟物流组织,并对不同农产品物流组织形式的发展等方面进行了分析。  相似文献   
498.
安全产品的供求特性及其与行业安全形势的关系初探   总被引:1,自引:0,他引:1  
基于安全经济学的基本原理,通过对不同行业的自动安全水平和法定安全水平之间的关系的分析,论述了不同行业安全产品的需求特性,以及与此相适应的安全产品供给特性;并对安全产品的特殊供求机制与特定行业的安全形势之间的关系进行了初步的探讨,提出了提高行业安全水平的对策。  相似文献   
499.
This paper examines the modified patterns of utilizing non-timber forest products (NTFP) and associated behavioral changes around tropical forest areas in the context of conservation-related objectives and other commercially driven objectives. Our study introduces a conceptual framework based on the household production theory and tests empirically the hypotheses drawn at Sinharaja World Heritage in Sri Lanka. The results show that conditions introduced by forest conservation programs and the spread of small-scale commercial tea cultivation are transforming the economy around Sinharaja. The process is an economically rational one where resident communities decide upon their actions based on the opportunity cost of time involved with NTFP in the absence of observable prices. Although the process, overall, has led to a decline in the role of NTFP in the household economy, its impact over different NTFP are not uniform, leaving sustained demand for certain NTFP. This situation calls for a multifaceted approach in forest management programs to address the various household needs fulfilled by NTFP-based activities.  相似文献   
500.
文中论述了新疆地区乡镇企业发展与生态环境有关的产业结构特点和分布,分地区、分行业计算了乡镇工业1985—1988年的“三废”污染和生态破坏状况,并对1995年和2000年“三废”污染控制数量及生态—经济规划指标作了综合评述。提出了新疆乡镇企业经济与生态环境保护协调发展战略的主要对策和建议。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号