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   12259篇
  免费   1162篇
  国内免费   2243篇
安全科学   2413篇
废物处理   297篇
环保管理   2106篇
综合类   6179篇
基础理论   1476篇
环境理论   17篇
污染及防治   876篇
评价与监测   816篇
社会与环境   880篇
灾害及防治   604篇
  2024年   75篇
  2023年   319篇
  2022年   504篇
  2021年   548篇
  2020年   526篇
  2019年   515篇
  2018年   423篇
  2017年   539篇
  2016年   635篇
  2015年   626篇
  2014年   667篇
  2013年   931篇
  2012年   966篇
  2011年   1090篇
  2010年   691篇
  2009年   728篇
  2008年   613篇
  2007年   775篇
  2006年   672篇
  2005年   556篇
  2004年   412篇
  2003年   422篇
  2002年   357篇
  2001年   290篇
  2000年   226篇
  1999年   229篇
  1998年   157篇
  1997年   166篇
  1996年   149篇
  1995年   112篇
  1994年   129篇
  1993年   90篇
  1992年   69篇
  1991年   56篇
  1990年   48篇
  1989年   39篇
  1988年   42篇
  1987年   24篇
  1986年   15篇
  1985年   21篇
  1984年   14篇
  1983年   13篇
  1982年   26篇
  1981年   21篇
  1980年   19篇
  1979年   23篇
  1978年   17篇
  1977年   10篇
  1972年   18篇
  1971年   20篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
影响马尾松毛虫虫灾发生类型因素的重要性分析   总被引:4,自引:1,他引:3  
运用列联表分析方法探讨了小班的林地起源、优势树种、地理、生长等因素对小班的马尾松毛虫虫灾发生类型的影响。分析结果表明:小班的海拔高度和坡度是决定小班的马尾松虫灾发生类型的关键因素。小班的优势种结构、平均树高及郁闭度对小班的马尾松毛虫虫灾发生类型也有较大的影响。图12表1参2  相似文献   
972.
环境气体标准样品量值的计算及不确定度分析   总被引:1,自引:1,他引:0  
依据《气体分析校准气体混合物的制备重量法》(1SO6142—2001)和《气体分析气体标准样品组成的测定和校验比较法》(ISO6143—2001),阐述了环境气体标准样品不同定值方法的量值计算及不确定度来源,并比较了同一气体标准样品采用不同定值方法得到的不同量值结果及不确定度:  相似文献   
973.
In this study, an interval-fuzzy two-stage chance-constrained integer programming (IFTCIP) method is developed for supporting environmental management under uncertainty. The IFTCIP improves upon the existing interval, fuzzy, and two-stage programming approaches by allowing uncertainties expressed as probability distributions, fuzzy sets, and discrete intervals to be directly incorporated within a general mixed integer linear programming framework. It has advantages in uncertainty reflection, policy investigation, risk assessment, and capacity-expansion analysis in comparison to the other optimization methods. Moreover, it can help examine the risk of violating system constraints and the associated consequences. The developed method is applied to the planning for facility expansion and waste-flow allocation within a municipal solid waste management system. Violations of capacity constraints are allowed under a range of significance levels, which reflects tradeoffs between the system cost and the constraint-violation risk. The results indicate that reasonable solutions for both binary and continuous variables have been generated under different risk levels. They are useful for generating desired decision alternatives with minimized system cost and constraint-violation risk under various environmental, economic, and system-reliability conditions. Generally, willingness to take a higher risk of constraint violation will guarantee a lower system cost; a strong desire to acquire a lower risk will run into a higher system cost.  相似文献   
974.
高效液相色谱-原子荧光光谱联用分析土壤中形态砷   总被引:4,自引:0,他引:4  
采用高效液相色谱(HPLC)-原子荧光光谱(AFS)联用技术分析土壤中亚砷酸盐[As(Ⅲ)]、二甲基砷(DMA)、一甲基砷(MMA)和砷酸盐[As(Ⅴ)]等4种形态砷,以磷酸为提取剂、抗坏血酸为还原剂,优化了水浴提取条件。As(Ⅲ)、DMA、MMA和As(Ⅴ)在7 min之内实现了完全分离,在1.00μg/L~100μg/L范围内线性良好,实验室检出限分别为0.25μg/L、0.36μg/L、0.39μg/L和0.51μg/L,土壤标准样品平行测定的RSD≤7.4%,加标回收率为79.5%~95.0%,提取率为74.6%~90.4%。  相似文献   
975.
按照江苏省辐射环境质量监测实施方案,徐州市对大气、水、土壤进行了布点监测,通过分析2007—2011年辐射环境监测数据,得出结论为:徐州市辐射环境整体质量为良好,且相对稳定,在未来几年内,仍将保持良好的状态。  相似文献   
976.
李沫 《干旱环境监测》2012,26(3):162-166,F0004
运用GIS、RS技术及景观生态学理论和方法,基于乌鲁木齐市2006年和2010年遥感影像解译数据,对乌鲁木齐市5年间土地利用景观格局变化特征进行分析,分别从斑块类型和景观水平2个方面对研究区土地利用景观类型进行动态分析。揭示其变化原因和内在规律,为研究区生态治理提供数据支撑,对景观的规划与管理、资源的有效利用和生物多样性保护具有重要意义。  相似文献   
977.
Errors in environmental resource management over the years have created pollution problems in some areas which are difficult to handle, regardless of the development of knowledge and technologies. This is particularly true in the case of soil pollution. The negative effects of persistent pollutants have been observed for a long time. For instance, lead and cadmium remain in the soil for centuries, during which time they are absorbed by plants and simultaneously cause secondary air pollution. The authors made an attempt to describe and assess the possible options of dealing with the problem of contaminated land in Katowice District. Considering the necessity of a multilateral approach, a pairwise comparison technique has been chosen as the most suitable to show the complexity of the problem. The different variants of actions aimed at preventing the pollutants from getting into the food chain were analyzed against a set of criteria, consisting of the following issues: time, cost, effectiveness, social acceptance, feasibility. The relative importance of actions were judged by the team of experts using the Saaty method. Also, a two-perspective assessment (the two different stakeholders), which involves considering the perspective of an owner of a piece of contaminated land and an ecologist has been performed. The results of comparative, multicriteria and multi-perspective assessment indicate the following:- the best method for contaminated agricultural land management is willful and controlled cultivation,- other recommended actions are deep ploughing and phytoremediation,- there is not much acceptance for the other methods.  相似文献   
978.
Decision–support systems in the field of integrated water management could benefit considerably from social science knowledge, as many environmental changes are human-induced. Unfortunately the adequate incorporation of qualitative social science concepts in a quantitative modeling framework is not straightforward. The applicability of fuzzy set theory and fuzzy cognitive maps for the integration of qualitative scenarios in a decision–support system was examined for the urbanization of the coastal city of Ujung Pandang, Indonesia. The results indicate that both techniques are useful tools for the design of integrated models based on a combination of concepts from the natural and social sciences. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
979.
地下饮用水中痕量NO2-的催化动力学法测定   总被引:3,自引:0,他引:3  
报道了一种新的测定NO2-的高选择性和高灵敏度的催化光度分析法.基于H3PO4介质中,碘绿与溴酸钾的氧化还原反应受亚硝酸盐的催化使碘绿褪色.据此建立了测定NO2-的新方法.本方法检出限为0.29μg/L,该方法用于地下饮用水、环境标样的测定,相对标准偏差为1.05%~4.80%,加标回收率为95%~117%.  相似文献   
980.
Waters and sediments of Subin River, which flows through the industrial and commercial areas of Kumasi in the Ashanti region of Ghana, were geochemically investigated to ascertain heavy metal pollution levels due to anthropogenic activities. The study shows preoccupying pollution levels that constitute a threat to public and ecological systems. The waters of Subin River are neutral to slightly basic, inferred from pH values of 6.89–7.65). Electric conductivity (EC) of the waters ranges from 822 to 1,821 μs/cm and the range of total dissolved solids (TDS) is from 409 to 913 mg/l. Toxic elements contents of sediments and waters from 10 sites along the river were analysed by instrumental neutron activation analysis (INAA), and Al, As, Cd, Cr, Cu and Zn were determined. The concentrations of Al, As, Cd, Cr, Cu and Zn in the waters range between 4.02–15.18, 0.007–0.16, 0.002–0.05, 0.001–0.019, 1.32–7.04 and 4.28–10.2 mg/l, respectively. The contamination factors (CF) computed for the elements indicate that with the exception of sampling site S10, the sediments are polluted with Cd. Chromium contamination in the sediments is observed at S6 and S7, where the CF values were 1.39 and 1.52, respectively. The pollution load indices (PLI) were low (<1) and ranged from 0.14 to 0.75, suggesting that the overall sediment column of the river is not polluted.  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