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   1562篇
  免费   145篇
  国内免费   316篇
安全科学   130篇
废物处理   12篇
环保管理   259篇
综合类   934篇
基础理论   250篇
环境理论   1篇
污染及防治   82篇
评价与监测   91篇
社会与环境   158篇
灾害及防治   106篇
  2024年   6篇
  2023年   31篇
  2022年   57篇
  2021年   58篇
  2020年   47篇
  2019年   53篇
  2018年   49篇
  2017年   68篇
  2016年   78篇
  2015年   86篇
  2014年   63篇
  2013年   107篇
  2012年   130篇
  2011年   139篇
  2010年   100篇
  2009年   78篇
  2008年   71篇
  2007年   86篇
  2006年   106篇
  2005年   81篇
  2004年   67篇
  2003年   75篇
  2002年   48篇
  2001年   35篇
  2000年   51篇
  1999年   44篇
  1998年   29篇
  1997年   34篇
  1996年   34篇
  1995年   19篇
  1994年   14篇
  1993年   14篇
  1992年   14篇
  1991年   9篇
  1990年   7篇
  1989年   5篇
  1988年   6篇
  1987年   3篇
  1986年   1篇
  1985年   3篇
  1984年   3篇
  1983年   1篇
  1982年   1篇
  1981年   1篇
  1980年   3篇
  1979年   1篇
  1977年   3篇
  1975年   2篇
  1973年   1篇
  1972年   1篇
排序方式: 共有2023条查询结果,搜索用时 15 毫秒
881.
新疆阿勒泰地区主要风景旅游区水环境与可持续发展   总被引:1,自引:0,他引:1  
潘旭  刘开华  谢碧海 《干旱环境监测》2003,17(4):215-217,238
对阿勒泰地区主要风景旅游区水环境保护与可持续发展进行了探讨。  相似文献   
882.
This work was conducted to analyse pressing and competingdemands of water in Northeast Sicily, Italy. In thisarea, looking at the Ionian Sea, freshwaters and coastalseawaters have been studied on the quality and on thetransport processes of pollutants. Attention has beenfocused on chemical and microbial parameters proposed byEuropean Directives for drinking freshwaters and bathingseawaters. The findings show that the ground freshwaters areof good quality but the surface ones, particularly torrentsand correlated under-river aquifers, are clearly polluted.The characteristics of the coastal seawaters are accordingwith those of the closely bound up estuarine waters.Contamination is due essentially to discharge of raw sewagein the watercourses by public and private pipes. The impactis usually less evident during the wet season because rainand seastorms dilute the polluting load, but in dry periodsthis pollution causes loss of habitat and deleterious effectson environment. A database has been developed to provide agraphic and mapping display interface of the area studied andto assist the management of the studied fluvial basins.  相似文献   
883.
Sea-level rise involves increases in the coastal processes of inundation and erosion which are affected by a complex interplay of physical environmental parameters at the coast. Many assessments of coastal vulnerability to sea-level rise have been detailed and localised in extent. There is a need for regional assessment techniques which identify areas vulnerable to sea-level rise. Four physical environmental parameters – elevation, exposure, aspect and slope, are modeled on a regional scale for the Northern Spencer Gulf (NSG) study area using commonly available low-resolution elevation data of 10 m contour interval and GIS-based spatial modeling techniques. For comparison, the same parameters are modeled on a fine-scale for the False Bay area within the NSG using high-resolution elevation data. Physical environmental parameters on the two scales are statistically compared to coastal vulnerability classes as identified by Harvey et al. [1] using the Spearman rank-correlation test and stepwise linear regression. Coastal vulnerability is strongly correlated with elevation and exposure at both scales and this relationship is only slightly stronger for the high resolution False Bay data. The results of this study suggest that regional scale distributed coastal process modeling may be suitable as a first cut in assessing coastal vulnerability to sea-level rise in tide-dominated, sedimentary coastal regions. Distributed coastal process modeling provides a suitable basis for the assessment of coastal vulnerability to sea-level rise of sufficient accuracy for on-ground management and priority-setting on a regional scale.  相似文献   
884.
A long-term study of temperature, pH, turbidity, suspended solid, salinity, dissolved oxygen, biochemical oxygen demand and ammonia nitrogen has been performed in a port and harbour region in India for four years from December 1996 to November 2000. Marine water quality results showed no regular trend. The mean monthly values of temperature, pH, turbidity, suspended solid, salinity, dissolved oxygen, biochemical oxygen demand and ammonia nitrogen were in the range of 22.64 ± 0.4 to 29.05 ± 1.37 °C; 7.65 ± 0.04 to 7.81 ± 0.13; 28.8 ± 14.7 to 64.2 ± 32.0 NTU; 283.5 ± 81.8 to 356.0 ± 159.7 mg/L; 29.78 ± 7.18 to 29.78 ± 1.04 ppt; 4.67 ± 0.50 to 6.01 ± 1.02 mg/L; 5.41 ± 1.92 to 7.56 ± 2.1 mg/L; and 0.25 ± 0.07 to 0.63 ± 0.49 mg/L, respectively. The results of correlation analysis showed that biochemical oxygen demand (BOD) was inversely correlated dissolved oxygen (DO) and poorly correlated with all other parameters. Turbidity and suspended solid were moderately correlated with each other while salinity was moderately correlated with other water quality parameters. In factor analysis, four factors were drawn out of the eight variables, which represented 74% of the variance of the original data. Factor I was related to suspended solid and turbidity. Factor II represented mainly temperature and DO showing inverse relation between these two. Factor III implied the degree of pollution at any monitoring station. Factor IV included pH and salinity. It could be concluded that the factor model represented almost all the variables.  相似文献   
885.
卢雪梅  苏华 《环境科学学报》2020,40(8):2819-2827
悬浮物(TSM)是评估水质的重要指标,也是水色遥感反演的核心参数之一.海陆色度仪(OLCI)是新一代海洋水色传感器,具有良好的光谱及时空分辨率.为有效监测福建近海悬浮物浓度的时空变化,本文结合OLCI遥感数据和现场实测悬浮物浓度数据,使用CatBoost、随机森林和多元回归方法,分别构建悬浮物浓度反演模型,最后使用验证集对比分析不同模型的反演精度.结果表明,CatBoost模型估算精度最高,均方根误差(RMSE)为2.76 mg·L-1,平均绝对百分比误差(MAPE)为23.67%,决定系数R2为0.89.使用CatBoost模型对2017—2018年多时相OLCI影像进行TSM浓度遥感反演,结果发现,福建近海TSM浓度变化显著,但总体呈现近岸高于远岸、北部高于南部、江河入海口和港湾处高于周围其他海域、春季高于夏季的时空分布特征.本研究可为福建近海的悬浮物浓度监测提供一种有效的方法,也进一步证明了OLCI影像良好的水色反演能力,可作为水质监测的有效遥感数据源.  相似文献   
886.
Despite the advances in climate change modeling, extreme events pose a challenge to develop approaches that are relevant for urban stormwater infrastructure designs and best management practices. The study first investigates the statistical methods applied to the land‐based daily precipitation series acquired from the Global Historical Climatology Network‐Daily (GHCN‐D). Additional analysis was carried out on the simulated Multivariate Adaptive Constructed Analogs (MACA)‐based downscaled daily extreme precipitation of 15 General Circulation Models and Weather Research and Forecasting‐based hourly extreme precipitation of North American Regional Reanalysis to discern the return period of 24‐hr and 48‐hr events. We infer that the GHCN‐D and MACA‐based precipitation reveals increasing trends in annual and seasonal extreme daily precipitation. Both BCC‐CSM1‐1‐m and GFDL‐ESM2M models revealed that the magnitude and frequency of extreme precipitation events are projected to increase between 2016 and 2099. We conclude that the future scenarios show an increase in magnitudes of extreme precipitation up to three times across southeastern Virginia resulting in increased discharge rates at selected gauge locations. The depth‐duration‐frequency curve predicted an increase of 2–3 times in 24‐ and 48‐h precipitation intensity, higher peaks, and indicated an increase of up to 50% in flood magnitude in future scenarios.  相似文献   
887.
Planning for hazard mitigation is frequently detached from other planning activities that influence development patterns in hazardous areas. Consistent integration of mitigation reduces hazard vulnerability for people and the built environment. We apply a plan integration for resilience scorecard in six US coastal cities to evaluate the integration of local networks of plans and the degree to which they target areas most vulnerable to flooding hazards. We find that plan integration scores vary widely across the six cities, and that some plans actually increase vulnerability in hazard zones. Policies also frequently support mitigation in areas with low vulnerability, rather than in areas with high vulnerability. The plan integration for resilience scorecard can generate information to improve hazard planning by allowing planners to identify conflicts between plans, assess whether plans target areas that are most vulnerable, and better inform decision makers about opportunities to mainstream mitigation into multiple sectors of planning.  相似文献   
888.
为了研究典型长廊型高层建筑中走廊-前室缓冲区不同参数设置对烟气控制的影响,利用FDS软件建立长廊型高建筑火灾烟气运动模型。利用空气幕配合正压送风在前室门前形成防烟缓冲区,运用正交设计的方法分析流量比、空气幕射流速度以及空气幕射流角度对缓冲区防烟能力的影响,得出防烟缓冲区最佳模式为空气幕送风量与前室加压送风量之比为2∶1,空气幕射流速度为8 m/s,空气幕射流角度为30°。与传统正压送风防烟模式相比,防烟缓冲区最佳模式下,前室的平均CO浓度降低了99.99%,平均温度降低了98.47%,防烟缓冲最佳模式使前室加压送风量减少了1/3,楼梯间加压风量减少22.56%,节约了送竖井的地面积,减少了进入走廊和火场区的送风量,使排烟效率提高了8.76%。  相似文献   
889.
刘永叶  陈鲁  乔亚华  杨阳  曹亮 《环境工程》2016,34(11):60-63
随着我国电力事业的快速发展,电厂循环冷却水(温排水)的余热排放对受纳水体生态环境造成的负面热影响(即热污染)已日益引起社会关注。基于国内现有的温排水排放控制标准可执行性不强的现状,对我国电厂温排水的热污染控制标准的基础技术要素——温排水混合区边缘温升限值进行了研究。以我国北方某典型滨海核电厂址邻近海域的代表性海洋生物为研究对象,以各季节不同受试物种最大临界温度(CTM)的统计分析结果,作为确定该厂址温排水混合区边缘温升限值的主要依据。并结合法规调研法,最终确定该典型滨海核电厂址温排水混合区边缘温升限值的推荐值为3.6℃。  相似文献   
890.
在盐城国家级自然保护区内选择研究断面,进行野外监测,运用统计分析的方法,分析了盐城海滨湿土壤水分与植被的关系.结果表明:(1)自然条件下,从芦苇沼泽到米草沼泽,土壤水分呈明显的增加趋势,0~10 cm土层平均含水量从35.98%增加到46.10%;10~20 cm土层平均含水量从37.93%增加到44.80%;20~30 cm土层平均含水量从38.12%增加到46.84%.(2)人为影响下,土壤含水量在整体上表现出从陆地到海洋,先降低后增加的趋势.(3)在植被交错带,米草土壤含水量与斑块大小密切相关,随着斑块面积的增加而增加;芦苇土壤含水量与距海堤距离密切相关,对着距离的增加而增加.  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