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   5381篇
  免费   681篇
  国内免费   1664篇
安全科学   872篇
废物处理   179篇
环保管理   526篇
综合类   3783篇
基础理论   692篇
污染及防治   690篇
评价与监测   740篇
社会与环境   159篇
灾害及防治   85篇
  2024年   17篇
  2023年   86篇
  2022年   173篇
  2021年   229篇
  2020年   233篇
  2019年   230篇
  2018年   252篇
  2017年   281篇
  2016年   314篇
  2015年   347篇
  2014年   367篇
  2013年   460篇
  2012年   460篇
  2011年   479篇
  2010年   323篇
  2009年   323篇
  2008年   277篇
  2007年   397篇
  2006年   383篇
  2005年   305篇
  2004年   256篇
  2003年   294篇
  2002年   233篇
  2001年   196篇
  2000年   178篇
  1999年   126篇
  1998年   82篇
  1997年   80篇
  1996年   68篇
  1995年   60篇
  1994年   57篇
  1993年   32篇
  1992年   25篇
  1991年   24篇
  1990年   23篇
  1989年   8篇
  1988年   8篇
  1987年   10篇
  1986年   6篇
  1985年   2篇
  1984年   2篇
  1983年   3篇
  1981年   3篇
  1980年   2篇
  1979年   2篇
  1974年   1篇
  1973年   2篇
  1972年   3篇
  1971年   1篇
  1970年   1篇
排序方式: 共有7726条查询结果,搜索用时 828 毫秒
511.
模拟退火算法在大气环境质量综合评价中的应用   总被引:2,自引:0,他引:2  
为了建立一种对多项指标都能普遍使用的大气环境质量综合评价模式,利用模拟退火算法对幂函数加和型指数评价中参数进行优化,并用优化后的综合评价指数公式对大气环境进行综合评价。该公式应用于大量实例的分析评价结果与其他多种评价方法评价结果比较表明:该公式不受污染物种类和数目多少的限制,计算简便,具有可行性、实用性和通用性。  相似文献   
512.
本文根据20^#钢板镀铬材料在我国海洋环境的暴露结果,对20^#钢板镀铬材料在我国海洋环境条件下的腐蚀速度及腐蚀原因进行分析。  相似文献   
513.
对外开放度是测量一个地区经济发展国际化程度的一个重要标志。以SPSS12.0为分析工具,运用回归分析方法,对安徽省四大区域对外开放度差异进行了测定和分析。2000年以来,安徽省四大经济区域对外开放度有了明显提高,但基础设施、区位条件、产业结构等方面的差异导致四大区域之间、区域内部以及地市之间的对外开放度存在明显差异。回归分析显示,对外开放度与安徽区域经济增长有着显著的相关性。  相似文献   
514.
Abstract: Storm‐flow transients (i.e., hydrograph rise and fall dynamics) may represent an important aspect of understanding streamflow dynamics. However, little is known about how temporal resolution of transient data and climate variability may color these potential indicators of hydrologic pattern or condition. Warm‐season stream stage and rainfall were monitored continuously (5 min) during the 2002 water year in eight tributaries of the Little Miami River (Ohio), which drain 17‐58 km2 catchments. Rise rates generated using 5‐min data were different than those generated with mean daily data [calculated with the Indicators of Hydrologic Alteration (IHA) software], though fall rates were similar for fine and coarse temporal data. This result suggests that data with low temporal resolution may not be adequate to fully represent the dynamics of storm rise rates. Conversely, fall rates based on daily stage data (via IHA) were similar to those based on the 5‐min data, and so daily mean data may be appropriate for characterizing fall rates. We next analyzed the possible correlations between rainfall variability and storm‐flow stage dynamics. We derived rise and recession rates from storm stage hydrographs by assuming exponential rise and decay of a runoff peak. We found that raw rise rates (Rraw) were correlated with both the maximum rainfall rate and the time to the centroid of a rain event. We subsequently removed the trend based on these rainfall characteristics, which yielded new representations of rise rates abbreviated as Rrate and Rtcent, respectively, and that had lower variability than the uncorrected (raw) data. Fall rates were found to be independent of rainfall characteristics. Due to the predominant influence of stream hydrology upon aquatic biota and nutrient fluxes, our work suggests that these stage data analysis protocols can refine or otherwise reduce variability in these indices by accounting for relevant factors such as rainfall forcing. These protocols for derivation of transient indices should be tested for their potential to improve correlations between stream hydrology and temporally aligned biotic data and dissolved nutrient fluxes in streams.  相似文献   
515.
根据内抽外压式集烟尘器专利研制了一个内抽外压式集尘器,并在井下进行实验。经过3种方法测试均收到预期的的效果,司机工作区达到了国家卫生要求,由于采用外筒压风,防止了瓦斯积聚避免瓦斯爆炸。应用离散颗粒模型模拟了内抽外压式集尘器内气相流场和粉尘颗粒的运动,该集尘器不仅把矿井巷道中细微可呼吸粉尘吸收到除尘器中,又能防止了瓦斯积聚。数值模拟与实验结果的一致性表明:把内抽外压式集尘器放置在掘进机前方,由于粉尘在气流的携带下运动使掘进机司机在矿井巷道中的工作环境得到改善,减少矿工患尘肺病的概率,开发了井下集尘的新工艺、新设备。  相似文献   
516.
出口角度对防烟空气幕防烟效果影响的数值模拟   总被引:1,自引:0,他引:1  
利用火灾动力学模拟软件FDS,以四川消防研究所高层实验塔二层为原型,模拟在不同防烟空气幕出口角度情况下高层建筑前室烟气运动情况,获得在其他条件不变情况下,空气幕运行时的最佳出口角度。试验结果表明:空气幕角度为5°及20°时,模拟试验后期烟气基本突破了空气幕蔓延至前室内,而当出口角度为10°和15°时防烟效果较好,且15°时防烟效果优于10°,故推荐空气幕运行时的最佳出口角度为15°。  相似文献   
517.
吴淞工业区大气降尘变化规律及趋势   总被引:2,自引:1,他引:1  
吴淞工业区是重工业聚集区,烟(粉)尘的排放量非常大,造成该地区空气污染严重.为了解降尘的污染特征、变化规律及趋势,以近10 a监测数据为依据,运用方差分析等数理统计方法对工业区降尘量进行分析,检验不同季节降尘的差异并简要分析原因,使用秩相关系数法对其进行趋势分析.结果表明,工业区降尘量较混合区与清洁区明显不同; 工业区与混合区的降尘受本地源的影响较大,4季的降尘量没有明显差异,相反清洁区的4季降尘呈显著差异.10 a来工业区及其周边地区的降尘量下降了56%,说明环境综合整治取得了显著效果,使区域环境空气质量得到改善.  相似文献   
518.
本文介绍了一种新型正压空气呼吸器面罩的结构设计。分别从数据采集、曲面重构及实体建模等方面对面罩的数字化设计步骤进行了详细阐述,并对面罩视野进行了初步校核。  相似文献   
519.
Malaysia is in dire need of alternatives to landfilling for solid waste management. Recently, landfills have faced the problems of overfilling, overflowing of leachates leading to pollution of water resources, and uncontrolled dust emissions adversely affecting the local environment. With the rising cost of urbanization coupled with the high rate of waste generation, one possible method of waste treatment that is receiving particular attention by the government is incineration. Incineration of solid waste is rather new in Malaysia, with limited usage in handling small sources of waste generation such as the municipal solid waste (MSW) of resort islands; however, its potential in ameliorating the problems associated with solid waste treatment may make it an attractive alternative to landfill. This article presents the results of test runs conducted to investigate the performance of a locally designed and manufactured rotary kiln incinerator (RKI). The test runs were conducted using MSW collected from the Shah Alam municipality. The combustion efficiency was analyzed by looking at the temperature profiles and chemical species concentrations. To complement the combustion characteristics measurements, predictions of the air flow in the incinerator during the process were also investigated. The overall performance of the RKI suggests that it is suitable for treating MSW.  相似文献   
520.
An air quality monitoring network (AQMN) usually performs the basic function of assessment of regional air quality and demonstration of compliance with ambient air quality standards in an urban area. Different pollutants, however, may present different characteristic variabilities due to their specific emission patterns, rates of diffusion, and transport and transformation behaviors. But the costs of siting in a pollutant-specific monitoring network would be higher than that for a common network with respect to several pollutants monitored simultaneously. This paper presents a survey of multi-pollutant design principles and optimal searches for siting patterns of an AQMN using both simulation and optimization models as a combined tool. While conservative, quasi-stable, and reactive pollutants are considered in the design principles, cost, coverage effectiveness, and spatial correlation characteristics are included in the multi-criteria decision making process. For illustrative purpose, a series of technical settings and two types of objectives were examined in the case study for the city of Kaohsiung in Taiwan.  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