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   3535篇
  免费   179篇
  国内免费   272篇
安全科学   141篇
废物处理   15篇
环保管理   952篇
综合类   1747篇
基础理论   327篇
环境理论   1篇
污染及防治   145篇
评价与监测   223篇
社会与环境   340篇
灾害及防治   95篇
  2024年   6篇
  2023年   38篇
  2022年   52篇
  2021年   79篇
  2020年   119篇
  2019年   80篇
  2018年   73篇
  2017年   105篇
  2016年   134篇
  2015年   116篇
  2014年   151篇
  2013年   181篇
  2012年   193篇
  2011年   259篇
  2010年   166篇
  2009年   233篇
  2008年   205篇
  2007年   242篇
  2006年   197篇
  2005年   149篇
  2004年   129篇
  2003年   153篇
  2002年   137篇
  2001年   102篇
  2000年   143篇
  1999年   118篇
  1998年   95篇
  1997年   59篇
  1996年   32篇
  1995年   59篇
  1994年   23篇
  1993年   36篇
  1992年   27篇
  1991年   14篇
  1990年   11篇
  1989年   11篇
  1988年   7篇
  1987年   8篇
  1986年   10篇
  1985年   9篇
  1984年   5篇
  1983年   4篇
  1982年   8篇
  1981年   3篇
  1980年   1篇
  1977年   1篇
  1974年   2篇
  1968年   1篇
排序方式: 共有3986条查询结果,搜索用时 593 毫秒
911.
This paper analyzes how sustained yield (SY) forestry is defined and implemented in Sweden and Russia, two countries with different forest-industrial regimes. We first compare definitions of SY forestry in national legislation and policies. Then we study forest management planning in two large forest management units with respect to: delivered forest products and values, how the harvest level of timber is defined, where the harvest takes place, and what treatments are used to sustain desired forest products and values. In Sweden SY forestry is maximum yield based on high-input forest management, and in Russia it is forestry based on natural regeneration with minimum investments in silviculture. We conclude that how SY forestry contributes to SFM depends on the context. Finally, we discuss the consequences of SY forestry as performed in Sweden and Russia related to its ability to support diverse forest functions, as envisioned in sustainable forest management policy.  相似文献   
912.
利用2021—2022年Sentinel-2卫星搭载的多光谱成像仪(MSI)遥感数据,通过SNAP遥感软件提供的植被生物物理参数处理模块(Biophysical Processor),反演了苏州消夏湾生态安全缓冲区的5种植被生物物理参数,包括植被吸收光合有效辐射比例(FAPAR)、植被覆盖度(FVC)、叶面积指数(LAI)、冠层叶绿素含量(CCC)和冠层含水量(CWC),开展植被生态环境监测评估研究。结果表明,该生态安全缓冲区2021年建成并投入运行后,植被覆盖度和生物量有所增加,区域植被冠层结构有所改善,植被生物物理参数从一定的角度反映了消夏湾生态安全缓冲区发挥了生态涵养成效。该研究方法能在大尺度上快捷、高效地反演植被生物物理参数,可为通过植被遥感动态监测评估生态安全缓冲区的生态功能提供有益的借鉴。  相似文献   
913.
Much quantitative research examining the determinants of the ecological footprint has been conducted cross-nationally, where data on cross-boundary flows have been readily available. While local-level studies of the footprint do exist for specific localities, most quantitative research at this scale has examined direct environmental impacts attributed to the internal activities of the locality, for instance, carbon emissions. Our analysis builds on this previous work by exploiting a local-level carbon footprint dataset with coverage for 28,321 zip codes across the United States. Following prior research, we focus on the effect of local affluence, measured in terms of median household income. In spatial regression models, we regress the per capita carbon footprint on local affluence, controlling for a variety of other factors. Consistent with previous work, we find that affluence is positively correlated the carbon footprint and there is no evidence of an environmental Kuznets curve. In the conclusion, we review the results of the study and discuss their implications for policy, specifically in terms of cross-boundary environmental problems.  相似文献   
914.
● Blackwater is the main source of organics and nutrients in domestic wastewater. ● Various treatment methods can be applied for resource recovery from blackwater. ● Blackwater treatment systems of high integration and efficiency are the future trend. ● More research is needed for the practical use of blackwater treatment systems. Blackwater (BW), consisting of feces, urine, flushing water and toilet paper, makes up an important portion of domestic wastewater. The improper disposal of BW may lead to environmental pollution and disease transmission, threatening the sustainable development of the world. Rich in nutrients and organic matter, BW could be treated for resource recovery and reuse through various approaches. Aimed at providing guidance for the future development of BW treatment and resource recovery, this paper presented a literature review of BWs produced in different countries and types of toilets, including their physiochemical characteristics, and current treatment and resource recovery strategies. The degradation and utilization of carbon (C), nitrogen (N) and phosphorus (P) within BW are underlined. The performance of different systems was classified and summarized. Among all the treating systems, biological and ecological systems have been long and widely applied for BW treatment, showing their universality and operability in nutrients and energy recovery, but they are either slow or ineffective in removal of some refractory pollutants. Novel processes, especially advanced oxidation processes (AOPs), are becoming increasingly extensively studied in BW treatment because of their high efficiency, especially for the removal of micropollutants and pathogens. This review could serve as an instructive guidance for the design and optimization of BW treatment technologies, aiming to help in the fulfilment of sustainable human excreta management.  相似文献   
915.
地下水是西部干旱地区重要的供水水源,随着西部大开发战略的深入,工业化和城市化发展加大了西宁市对地下水资源量的需求,不合理的开发利用已引起地下水环境发生变化,探明地下水化学演化特征及形成机制,对防止其恶化,确保可持续利用至关重要.运用水化学和多元统计技术相结合的方法,分析了西宁市地下水化学特征,探讨了地下水的形成机制和不同因子的影响程度.结果表明,西宁市浅层地下水化学类型多达36种,以HCO3-Ca(Mg)(占比60.00%)和HCO3·SO4-Ca(Mg)(占比11.81%)为主,草地、林地和裸地中地下水化学类型5~6种,建设用地和耕地中地下水化学类型复杂,多达21种,表明受到人类活动影响较强.研究区地下水化学演化过程主要受岩石风化溶滤、蒸发结晶和阳离子交换作用综合影响,主要控制因素分别是水-岩相互作用(贡献率为27.56%)、工业废水排放(贡献率为16.16%)、酸碱环境(贡献率为16.00%)、化肥、农药的过量施用(贡献率为13.11%)和生活污水(贡献率为8.82%).针对西宁市地下水化学特征及其人类活动影响,提出...  相似文献   
916.
Agroforestry is often an economically viable land-use option for the environmental rehabilitation of salinized cropping areas in irrigated drylands, but afforestation initiative at the farm level is subject to various socio-political constraints. We analyzed the factors that affect farmer decisions with respect to the agroforestry adoption using an ex ante approach through Ethnographic Decision Tree Modeling (EDTM). Constraints on agroforestry adoption were identified via a review of legal documents, focus-group discussions, and a farm survey in northwest Uzbekistan. The findings highlighted the importance of farmer perceptions of risk with respect to decision making surrounding the adoption of alternative land uses. The EDTM analysis allowed determining those policy incentives for afforestation that could directly influence the decision-making process of potential participants. In particular, there is a need for increased land-use flexibility, improved land tenure and tree plantation proprietorship security, increased awareness raising and training in agroforestry practices, and greater institutional support.  相似文献   
917.
Cathode ray tube (CRT) glass is considered a hazardous material due to its lead toxicity. In addition, current disposal practices are being phased out due to their adverse environmental impacts. In this project, CRT glass was used as a fine aggregate replacement in concrete. Life-cycle material characterization was conducted by evaluating the durability and strength of the CRT-Concrete. Leaching tests were also conducted to investigate whether the material meets drinking water limits for Pb. Test results show that the plastic state of the CRT-Concrete was affected by the angularity of the glass particles. Moreover, the compressive strength of CRT-Concrete met and exceeded that of the control specimen. However, CRT-Concrete was susceptible to expansive alkali-silica reactions when more than 10% CRT replacement was used. Environmental leaching results show that lead concentrations from CRT-Concrete are below the drinking water limits depending on the CRT volume replacement and if biopolymers are used.  相似文献   
918.
This paper highlights current trends in consumption and production patterns in Asian developing countries and emerging economies. It describes the main challenges and opportunities for Asian countries making the transition towards sustainable consumption and production patterns. The main challenge for Asian economies is to address the unsustainable consumption patterns of urban consumers, which entails a policy shift from the current focus on pollution and inefficient industrial production. In view of future consumption trends and the global convergence of consumption patterns, the characteristics of the emerging 'global consumer class' are examined, with particular focus on urban ecological footprints and carbon emissions. Furthermore, the difference between urban and rural consumption is discussed, together with opportunities for low-carbon urban development in the megacities of Asian developing countries. To conclude, the paper presents an overview of current policy measures taken in Asian countries to green economic development and realise sustainable consumption and production patterns.  相似文献   
919.
湖北省的经济发展水平与全国其它地区存在着较大的差异,从全国范围看,湖北省多年一直处在中等偏下的水平,而在长江流域,近年湖北省一下游省市的差距在迅速扩大;在中心地区各省中,湖北则相对领先。  相似文献   
920.
Energy efficiency policies have a special importance within carbon emission reduction policies to mitigate the climate change effects. However, potential reductions of energy consumption and, consequently, its resulting emissions, can be offset through the so called “rebound effect”. The concept of “rebound effect” refers to a set of mechanisms whereby the improvement of efficiency reduces the cost of the energy service and this results in the household energy consumption rising and totally or partially negating the reduction achieved by the energy efficiency improvement. This paper provides a methodology to estimate the static direct plus indirect rebound effect of energy efficiency improvements in the use of energy in households. It is based on the combination of econometric estimations of energy demand functions, re-spending modelling and generalised intput-output of energy modelling. It also provides estimations for Catalonia.  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