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   570篇
  免费   41篇
  国内免费   227篇
安全科学   37篇
废物处理   30篇
环保管理   60篇
综合类   368篇
基础理论   101篇
污染及防治   159篇
评价与监测   21篇
社会与环境   29篇
灾害及防治   33篇
  2024年   1篇
  2023年   15篇
  2022年   43篇
  2021年   29篇
  2020年   31篇
  2019年   15篇
  2018年   26篇
  2017年   42篇
  2016年   38篇
  2015年   43篇
  2014年   50篇
  2013年   65篇
  2012年   43篇
  2011年   44篇
  2010年   55篇
  2009年   39篇
  2008年   43篇
  2007年   25篇
  2006年   34篇
  2005年   20篇
  2004年   12篇
  2003年   12篇
  2002年   16篇
  2001年   14篇
  2000年   16篇
  1999年   13篇
  1998年   14篇
  1997年   11篇
  1996年   13篇
  1995年   5篇
  1994年   1篇
  1993年   3篇
  1992年   3篇
  1990年   1篇
  1989年   1篇
  1985年   1篇
  1982年   1篇
排序方式: 共有838条查询结果,搜索用时 312 毫秒
781.
资源是区域经济发展的基础,资源结构是区域产业结构赖以形成的重要条件。区域产业是经济发展的载体,它不仅支持着区域的增长,而且在很大程度上决策着经济增长的能力与潜力。据此,在分析湖南省资源及产业结构优化标准的基础上,提出了充分与合理利用资源的产业对策建议。  相似文献   
782.
分析了圆管压入扩径时内径变化的规律和影响因素.理论分析和实验结果相一致,对实际生产中产品质量的控制有参考价值.  相似文献   
783.
Selecting guidelines to evaluate elevated metals in urban brownfields is hindered by the lack of information for these sites on ecosystem structure and function. A study was performed to compare three trace metal-contaminated sites in the metropolitan Montreal area. The goal was to obtain an idea of the organisms that may be present on urban brownfields and to measure if elevated metals alter the presence and activity of the indigenous biota. Field and laboratory studies were conducted using simple methodologies to determine the extent to which microbial activity affected by trace metal content, to assess diversity of plant and soil invertebrate communities and to measure phytoaccumulation of trace metals. It was found that microbial activity, as measured by substrate-induced respiration (SIR) and nitrification, was not affected by the levels of soil Cd, Cu, Ni, Pb and Zn recorded on the sites. Seven of the 12 invertebrate groups collected were sampled on soils with similar Cd, Cu, Ni, Pb and Zn concentrations. Diversity of plant species increased as a function of the length of time the sites had been inactive. Levels of metals in plant tissue were influenced by soil characteristics and not by total soil Cd, Cu, Ni, Pb and Zn.  相似文献   
784.
针对煤矿排出的大量含重金属离子的酸性矿山废水污染问题,采用自制膨润土-白云石复合颗粒吸附剂对含Fe2+和Mn2+的酸性矿山废水进行吸附试验研究。结果表明:膨润土-白云石复合颗粒吸附剂释放总碱度达118.39mg/g(以CaCO3计),可中和酸性矿山废水;随着废水中Fe2+和Mn2+浓度增加,膨润土复合颗粒吸附剂的吸附量在不断增加,且大于原膨润土颗粒吸附剂;建立了膨润土复合颗粒吸附剂对Fe2+和Mn2+的吸附等温式和吸附动力学方程式:膨润土复合颗粒吸附剂对Fe2+的吸附符合BET吸附,对Mn2+的吸附符合Freundlich吸附,对Fe2+、Mn2+的吸附动力学均符合准二级动力学。膨润土-白云石复合颗粒吸附剂既能释放碱度、又对Fe2+和Mn2+具有优良的吸附性能,可作为处理含重金属离子酸性矿山废水的绿色环保矿物材料应用于实际。  相似文献   
785.
Adsorptionanddesorptionareimportantprocessesthataffectatrazinetransport,transformation,andbioavailabilityinsoils.Inthisstudy,theadsorption–desorptioncharacteristicsofatrazinein three soils (laterite, paddy soil and alluvial soil) were evaluated using the batch equilibrium method. The results showed that the kinetics of atrazine in soils was completed in two steps: a “fast” adsorption and a “slow” adsorption and could be well described by pseudo-second-order model.In addition,the adsorption equilibrium isotherms were nonlinear and were well fitted by Freundlich and Langmuir models. It was found that the adsorption data on laterite, and paddy soil were better fitted by the Freundlich model;as for alluvial soil,the Langmuir model described it better. The maximum atrazine sorption capacities ranked as follows: paddy soil > alluvial soil > laterite. Results of thermodynamic calculations indicated that atrazine adsorption on three tested soils was spontaneous and endothermic. The desorption data showed that negative hysteresis occurred. Furthermore, lower solution pH value was conducive to the adsorptionofatrazineinsoils.Theatrazineadsorptioninthesethreetestedsoilswascontrolled by physical adsorption, including partition and surface adsorption. At lower equilibrium concentration, the atrazine adsorption process in soils was dominated by surface adsorption;while with the increase of equilibrium concentration, partition was predominant.  相似文献   
786.
An instantaneous emission model was developed to model and predict the real driving emissions of the low-speed vehicles. The emission database used in the model was measured by using portable emission measurement system (PEMS) under actual traffic conditions in the rural area, and the characteristics of the emission data were determined in relation to the driving kinematics (speed and acceleration) of the low-speed vehicle. The input of the emission model is driving cycle, and the model requires instantaneous vehicle speed and acceleration levels as input variables and uses them to interpolate the pollutant emission rate maps to calculate the transient pollutant emission rates, which will be accumulated to calculate the total emissions released during the whole driving cycle. And the vehicle fuel consumption was determined through the carbon balance method. The model predicted the emissions and fuel consumption of an in-use low-speed vehicle type model, which agreed well with the measured data.  相似文献   
787.
我国农耕土壤Cd污染与植物修复现状   总被引:1,自引:0,他引:1  
中国人均耕地面积不足,农耕土壤的Cd污染问题对土壤资源的可持续利用和农作物的安全构成了巨大的潜在威胁。通过简述中国农耕土壤Cd污染现状和造成农耕土壤Cd污染的原因,并结合中原地区农耕土壤Cd污染调查情况,概述了中国近5年农耕土壤和农作物受到Cd污染的程度。总结近年来国家在济源开展植物修复土壤Cd污染试点工程及湖南启动长株潭耕地重金属污染修复以及农作物种植结构调整试点工程的修复效果,并简述了目前中国土壤的治理措施。最后,通过试点工程期间遇到的问题探究中国农耕土壤Cd污染的修复之路,展望未来Cd污染土壤修复工作的重点和预防措施。  相似文献   
788.
Rice (Oryza) is a staple food in China, and rice yield is inherently sensitive to climate change. It is of great regional and global importance to understand how and to what degree climate change will impact rice yields and to determine the adaptation options effectiveness for mitigating possible adverse impacts or for taking advantage of beneficial changes. The objectives of this study are to assess the climate change impact, the carbon dioxide (CO2) fertilization effect, and the adaptation strategy effectiveness on rice yields during future periods (2011–2099) under the newly released Representative Concentration Pathway (RCP) 4.5 scenario in the Sichuan Basin, one of the most important rice production areas of China. For this purpose, the Crop Estimation through Resource and Environment Synthesis (CERES)-Rice model was applied to conduct simulation, based on high-quality meteorological, soil and agricultural experimental data. The modeling results indicated a continuing rice reduction in the future periods. Compared to that without incorporating of increased CO2 concentration, a CO2 fertilization effect could mitigate but still not totally offset the negative climate change impacts on rice yields. Three adaptive measures, including advancing planting dates, switching to current high temperature tolerant varieties, and breeding new varieties, could effectively offset the negative climate change impacts with various degrees. Our results will not only contribute to inform regional future agricultural adaptation decisions in the Sichuan Basin but also gain insight into the mechanism of regional rice yield response to global climate change and the effectiveness of widely practiced global thereby assisting with appropriate adaptive strategies.  相似文献   
789.
选择三户典型城市家庭作为研究对象,对其家庭生活污水进行调查与分析.结果表明:城市家庭生活用水类型较多,主要分为洗澡水、洗衣水、淘米水、洗漱水、洗莱水、洗碗水、厕所用水和其它用水八个类型.所调查城市家庭人均用水量为217.84L/人·d,其范围在151.51~264.00L/人·d.所调查城市家庭生活污水的pH值的范围为6.14—7.43;浊度范周为13-221.6度;TP浓度的范围为0.69—3.18mg/L;COD浓度范围为5.9—1368.8mg/L。  相似文献   
790.
在城市环境目益恶化的今天,景观生态设计问题越来越受到人们的重视。此文从环境和生态的观点出发分析现代景观设计,并以中山岐江公园为例探讨景观设计与环境保护和生态主义之议题,提出景观设计创作之初应先进行环境评估,立足于环境保护和生态主义的景观设计才更具生命力。  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