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   814篇
  免费   24篇
  国内免费   70篇
安全科学   45篇
废物处理   38篇
环保管理   76篇
综合类   235篇
基础理论   174篇
环境理论   4篇
污染及防治   235篇
评价与监测   41篇
社会与环境   50篇
灾害及防治   10篇
  2024年   3篇
  2023年   13篇
  2022年   20篇
  2021年   20篇
  2020年   19篇
  2019年   13篇
  2018年   35篇
  2017年   28篇
  2016年   28篇
  2015年   26篇
  2014年   30篇
  2013年   49篇
  2012年   34篇
  2011年   57篇
  2010年   41篇
  2009年   43篇
  2008年   40篇
  2007年   52篇
  2006年   39篇
  2005年   26篇
  2004年   38篇
  2003年   27篇
  2002年   31篇
  2001年   12篇
  2000年   11篇
  1999年   8篇
  1998年   16篇
  1997年   18篇
  1996年   9篇
  1995年   9篇
  1994年   15篇
  1993年   7篇
  1992年   7篇
  1991年   5篇
  1990年   6篇
  1980年   3篇
  1976年   3篇
  1966年   3篇
  1964年   3篇
  1963年   3篇
  1962年   2篇
  1961年   3篇
  1960年   3篇
  1959年   2篇
  1957年   5篇
  1956年   6篇
  1955年   4篇
  1954年   2篇
  1951年   3篇
  1922年   3篇
排序方式: 共有908条查询结果,搜索用时 406 毫秒
681.
镇江斜发沸石对氨氮的吸附动力学及热力学研究   总被引:2,自引:1,他引:1  
采用静态平衡法,开展了镇江斜发沸石对水中氨氮的吸附动力学和热力学研究.结果表明,吸附量随反应温度升高而增加,斜发沸石对氨氮吸附符合Freundlich等温线方程,对氨氮吸附实验数据与准二级动力学模型拟合更好(R2>0.998),热力学参数吸附焓变△H=18.26 kJ/mol,熵变△S=0.0632 kJ/kmol,对...  相似文献   
682.
Due to historic reasons, there are several human settlements in nature reserves and national parks, which may constitute a threat to biodiversity. Establishment of nature reserves may however generate constraints for development of local communities residing in these reserves. The village ecosystem of Zhuanjinglou Village in Wolong Nature Reserve includes population, farming and livestock (domestic and alpine) and forest ecosystem. An emergy analysis of agro-ecosystem (including the farming and livestock ecosystem) and energy consumption in Zhuanjinglou Village indicates that livestock ecosystem plays an important role in village ecosystem, which may be the source of great pressure on the state of the local environment. The increasing ratio of electricity in energy consumption may play a positive role for environmental conservation. Despite some successful experiences, there are some remaining issues that need to be addressed in the ecological rehabilitation of the village ecosystem.  相似文献   
683.
Brominated flame retardants (BFRs) are used in a variety of consumer products and several of those are produced in large quantities. These compounds have been detected in environmental samples, which can be attributed to the anthropogenic uses of these compounds. Brominated flame retardants are produced via direct bromination of organic molecules or via addition of bromine to alkenes; hence, an overview of the production and usage of bromine over the past three decades is covered. Production, application, and environmental occurrence of high production brominated flame retardants including Tetrabromobisphenol A, polybrominated biphenyls, Penta-, Octa-, Deca-brominated diphenyl ether (oxide) formulation and hexabromocyclododecane are discussed.  相似文献   
684.
水域生态系统是温室气体的重要来源,静态浮箱法(SFC)是目前广泛采用估算水-气界面气体通量的方法之一,然而在利用线性回归(LR)拟合模型估算水-气界面气体通量时存在低估问题。采用密闭式静态浮箱-温室气体分析仪系统,观测了在三峡库区香溪河库湾水-气界面之上通量箱内甲烷和二氧化碳气体浓度的变化,对监测得到的数据进行拟合分析。对比分析了线性回归(LR)、二次回归(QR)和指数回归(ER)三种模型的拟合效果,结果表明非线性回归模型可以更好地拟合静态浮箱内气体浓度随时间的变化情况,从而得到更接近真实值的水-气界面气体通量。认为采用线性回归(LR)模型拟合水-气界面气体通量得到的结果在很大程度上被低估了,该方法得到甲烷和二氧化碳气体通量估算值平均约占实测值的77%和80%。此外,大多数情况下指数拟合模型的效果要优于二次回归拟合模型,而二次回归模型拟合系数没有物理意义,从理论上不适用于气体通量的估算。 关键词: 静态浮箱法;气体通量;线性拟合;非线性拟合  相似文献   
685.
环境—经济系统协调度模型及其指标体系   总被引:46,自引:2,他引:46  
本文以可持续发展理论为核心,借助系统工程多目标优化的思想,建立了新型环境—经济系统协调度模型。模型分为三个部分:功效函数、协调度函数和环境系统指标体系。  相似文献   
686.
Peat-based growing media are not ecologically sustainable and peat extraction threatens sensitive peatland ecosystem. In this study, olive-stone waste (OSW) and paper waste (PW) were used in different ratios—as growing media—for ornamental crop production, as peat (P) substitutes. Marigold (Calendula officinalis L.), petunia (Petunia x hybrita L.) and matthiola (Matthiola incana L.) plants were grown in (1) P (100%), (2) P:OSW (90%:10%), (3) P:OSW (70%:30%), and (4) P:OSW:PW (60%:20%:20%). The physicochemical properties of these substrates and the effects on plant growth were determined. The addition of 10–30% OSW into the substrate increased marigold height compared to plants grown in 100% peat. No differences in plant size, plant biomass (leaves and flowers), and dry matter content were found. Adding PW, in combination with OSW, maintained marigold height and total number of flowers produced to similar levels as in plants grown in 100% peat. In matthiola, adding 30% OSW into the substrate reduced plant size and fresh weight, but not plant height. No differences were observed when plants grew in lower OSW (i.e., 10%) content. Petunia’s height, its total number of flowers and flower earliness (flower opening) were increased in the presence of OSW compared to the plants grown in 100% peat. The addition of OSW did not affect petunia’s size and fresh weight among treatments. The addition of PW suppressed several plant growth-related parameters for both matthiola and petunia. The insertion of OSW did not change leaf chlorophyll content whereas the presence of PW decreased chlorophylls for marigold, petunia, and matthiola. Both OSW and PW altered the content of total phenolics and antioxidant capacity of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) in leaves and flowers for marigold and petunia. Both 30% OSW and PW increased antioxidative enzyme metabolism due to the increased damage index and lipid peroxidation observed in plants. Leaf N and P content decreased in PW-based media, while matthiola displayed visual phytotoxicity symptoms when PW was added into the substrate. The present work indicates that up to 30% of OSW can replace peat for marigold and petunia growing and only up to 10% of OSW for matthiola, while the addition of PW on top of OSW is not recommended, so further research is needed.  相似文献   
687.
The idea of sustainability is intrinsically normative. Thus, understanding the role of normativity in sustainability discourses is crucial for further developing sustainability science. In this article, we analyze three important documents that aim to advance sustainability and explore how they organize norms in relation to sustainability. The three documents are: the Pope’s Encyclical Laudato Si’, the Sustainable Development Goals and the Paris Agreement. We show that understanding the role of different types of norms in the three documents can help understand normative features of both scientific and non-scientific sustainability discourses. We present the diverse system of norms in a model that interrelates three different levels: macro, meso, and micro. Our model highlights how several processes affect the normative orientation of nations and societies at the meso-level in different ways. For instance, individual ethical norms at the micro-level, such as personal responsibility, may help decelerate unsustainable consumerism at the aggregate meso-level. We also show that techno-scientific norms at the macro-level representing global indicators for sustainability may accelerate innovations. We suggest that our model can help better organize normative features of sustainability discourses and, therefore, to contribute to the further development of sustainability science.  相似文献   
688.
Galvanized or “chromium-plated” plastics are well known to the consumer from the automotive sector and sanitary area. Polymers such as acrylonitrile butadiene styrene (ABS) are typically coated with a layer system of chromium, nickel and copper to obtain the characteristic optical surface and resistance properties. Due to the complex manufacturing process and high quality requirements, the production of these plastic metal composites generates 10–30% of rejects. We, therefore, developed an innovative process cascade for the recovery of both components (metal and polymer) applying established technologies (mechanical pre-treatment, classification, melt filtration, CreaSolv® Process) and were able to obtain ABS regranulate having excellent properties regarding the characteristic values for strength but slight compromises in impact characteristics. Blends with different amounts of virgin ABS, virgin PC and recycled ABS material as well as the pure cases were successfully re-metallized, all of them passing adhesion test, thermal shock resistance and CASS test. The high purity of the recovered materials led to increased redemption prices for metal and polymer by a factor of 6 and 2.5, respectively. Thus, the value added of metallized plastic waste is maximized, revealing a highly positive economic prognosis of a commercial implementation of the developed process—even at moderate scale.  相似文献   
689.
三峡库区是长江上游生态环境集敏感、脆弱、复杂为一体的地区,其生态安全格局的构建对维护区域生态安全、实现区域可持续发展具有重要作用.以三峡库区重庆段为研究区,采用2018年土地利用现状数据和遥感数据,构建生态服务重要性与生态敏感性评价体系,综合确定生态源地;以坡度、起伏度、土地利用类型确定阻力值,采用最小累积阻力模型构建生态廊道,最终形成三峡库区重庆段生态安全格局.研究结果表明:三峡库区重庆段生态源地面积13660.80 km2,占研究区总面积的29.61%,主要分布于巫溪、奉节、石柱、开州等区县;生态廊道连接生态源地,共81条,总长度为3069.29 km,廊道呈树状辐射分布,呈现"东北-西南"树状分布的空间格局;生态源地与生态廊道共同形成三峡库区东北生态城镇圈、三峡库区西南都市生态圈以及连接两圈的三峡库区中部走廊的"一廊两圈"生态安全格局.研究结果对保障三峡库区生态安全具有重要意义,可为三峡库区生态环境环境保护提供科学依据.  相似文献   
690.
Climate-induced changes in vegetation phenology at northern latitudes are still poorly understood. Continued monitoring and research are therefore needed to improve the understanding of abiotic drivers. Here we used 14 years of time lapse imagery and climate data from high-Arctic Northeast Greenland to assess the seasonal response of a dwarf shrub heath, grassland, and fen, to inter-annual variation in snow-cover, soil moisture, and air and soil temperatures. A late snow melt and start of growing season is counterbalanced by a fast greenup and a tendency to higher peak greenness values. Snow water equivalents and soil moisture explained up to 77 % of growing season duration and senescence phase, highlighting that water availability is a prominent driver in the heath site, rather than temperatures. We found a significant advance in the start of spring by 10 days and in the end of fall by 11 days, resulting in an unchanged growing season length. Vegetation greenness, derived from the imagery, was correlated to primary productivity, showing that the imagery holds valuable information on vegetation productivity.  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