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   147篇
  免费   15篇
  国内免费   55篇
安全科学   8篇
废物处理   4篇
环保管理   14篇
综合类   95篇
基础理论   33篇
污染及防治   27篇
评价与监测   11篇
社会与环境   6篇
灾害及防治   19篇
  2023年   2篇
  2022年   3篇
  2021年   8篇
  2020年   5篇
  2019年   6篇
  2018年   8篇
  2017年   10篇
  2016年   11篇
  2015年   8篇
  2014年   5篇
  2013年   13篇
  2012年   9篇
  2011年   5篇
  2010年   15篇
  2009年   15篇
  2008年   6篇
  2007年   10篇
  2006年   13篇
  2005年   7篇
  2004年   11篇
  2003年   9篇
  2002年   6篇
  2001年   7篇
  2000年   3篇
  1999年   4篇
  1998年   4篇
  1997年   6篇
  1996年   2篇
  1994年   1篇
  1993年   1篇
  1992年   2篇
  1990年   1篇
  1985年   1篇
排序方式: 共有217条查询结果,搜索用时 31 毫秒
141.
研究了酢浆草提取液(OX)、猪粪提取液(PM)以及味精厂废水(MGW)对土壤中Ni、Co的作用。结果表明,OX提取液原液对土壤中的Ni、Co有较好的活化作用,其活化比例分别达到4.8%和14.6%,但稀释后效果大幅度下降;MGW原液可活化土壤中的1.6%的Ni,但对Co的活化效果较差;PM提取液则对土壤中的重金属起到一定的固定作用。OX提取液的pH值与Ni、Co总活化比例之间呈显著幂相关,可能是由于受到多种酸性活性成分的影响所致。  相似文献   
142.
在水稻幼苗25叶期,分别用浓度为C10.01%、C20.03%和C30.04%(W/V)的Ni(NO3)2溶液(含0.05%Tween20)喷雾处理,以05%(W/V)Tween20作对照.在4 h、24 h、48 h、72 h、96 h分别测定叶片中的过氧化氢酶(CAT)活性.结果表明,Ni(NO3)2对过氧化氢酶活性有抑制作用且随其浓度的升高,抑制作用越明显,在72 h抑制作用最强,过氧化氢酶活性比对照分别下降了21.7%、28.3%、55.8%.  相似文献   
143.
We examined the response of demographic, morphological, and chemical parameters of turtle grass (Thalassia testudinum), to much-higher-than-normal rainfall associated with an El Niño event in the winter of 1997–1998. Up to 20 inches of added rain fell between December 1997 and March 1998, triggering widespread and persistent phytoplankton blooms along the west coast of Florida. Water-column chlorophyll concentrations estimated from serial SeaWiFS imagery were much higher during the El Niño event than in the previous or following years, although the timing and magnitude of phytoplankton blooms varied among sites. Seagrass samples collected in 1997, 1998, and 1999 provided an excellent opportunity to test the responsiveness of Thalassia to decline and subsequent improvement of water quality and clarity in four estuaries. Using a scoring technique based on temporal responsiveness, spatial consistency, and statistical strength of indicators, we found that several morphological parameters (Thalassia shoot density, blade width, blade number, and shoot-specific leaf area) were responsive and consistent measures of light stress. Some morphological parameters, such as rhizome apex density, responded to declines and subsequent improvement in water clarity, but lacked the statistical discriminating power necessary to be useful indicators. However, rhizome sugar, starch, and the total carbohydrate concentrations also exhibited spatially and temporally consistent variation as well as statistical strength. Because changes in shoot density, as well as water clarity, affect rhizome carbohydrate levels, a composite metric based on Thalassia shoot density and rhizome carbohydrate levels together is probably more useful than either parameter alone as an indicator of seagrass health.  相似文献   
144.
冯利华 《灾害学》1998,13(2):71-74
根据大量洪水和有关资料,从太阳活动、行星运行和地球系统等方面,分析了形成浙江洪水的物理因素,为洪水预测提供了一定的理论依据.  相似文献   
145.
Numerical modelling of fire-related smoke haze episodes in Southeast Asia is important for both prediction and assessment of atmospheric impacts, especially when observational data are fragmentary, as is the case in Indonesia. This work describes the atmospheric fate of smoke particles emitted during the 1997 Indonesian fires modelled with a regional atmospheric chemistry model. We established a new fire emission inventory and calculate that 55 teragram (Tg) of particulate matter and 1098 Tg of carbon were released during this fire episode. Our emission estimate is an intermediate value compared with other studies. Utilising different scenarios, we demonstrate the variable atmospheric impacts of surface vegetation fires and peat soil fires separately and also investigate the sensitivity of smoke dispersion to the differing meteorological conditions of an El Niño and a normal year. When peat fires are included in the emission inventory, modelled ambient particle concentrations exceed the ambient air quality standard across transboundary scales. In a scenario including only surface vegetation fires, ambient air quality standards are exceeded only in areas close to the main fires. This scenario demonstrates the prominent role of fires in peat areas in causing regional air pollution episodes. In years with normal meteorological conditions, intermittent precipitation and associated wet deposition during the dry season are predicted to remove most of the particulate emissions close to the sources. Strongly reduced rainfall and generally stronger southeasterly winds during El Niño years provide favourable conditions for larger scale smoke haze pollution.  相似文献   
146.
铁氧体法处理含Zn~(2+)、Ni~(2+)废水研究   总被引:11,自引:0,他引:11  
实验研究了铁氧体法处理含锌、镍混合废水的工艺条件。在 p H=8.0~ 1 0 .0 ,2≤ Fe2 + :M2 +≤ 8(M2 +以废水中总离子含量计 ) ,外加磁场强度为 2 0 0 T的条件下 ,锌、镍离子能够同时去除 ,其去除率可达 99%以上 ,沉渣沉降时间可缩短为1 0 mi  相似文献   
147.
研究了不同浓度镍、锌、铝对常见绿藻羊角月芽藻(S.capricornutum)生长速度、蛋白质含量、ATP水平、葡萄糖-6-磷酸脱氢酶(G6PDH)、酸性磷酸酶及硝酸还原酶活性的影响.结果表明3种金属离子在所试浓度范围内对羊角月芽藻的生长速度均有抑制作用,但单位藻培养物中蛋白质含量却随着金属离子浓度的增加而增加;高浓度金属离子对酶活性有明显抑制作用;藻细胞中ATP水平随着金属离子浓度的增加而下降.提出金属离子对藻类生物产生影响的机理可能是:高浓度金属离子的存在,打破了生物最佳的各种营养元素生物可利用性的平衡.并讨论了藻类生长及生化活性对金属离子反应的相关性.  相似文献   
148.
In order to enhance Ni-EDTA decomplexation and Ni recovery via photoelectrocatalytic (PEC) process, TiO2/Ni-Sb-SnO2 bifunctional electrode was fabricated as the photoanode and activated carbon fiber (ACF) was introduced as the cathode. At a cell voltage of 3.5 V and initial solution pH of 6.3, the TiO2/Ni-Sb-SnO2 bifunctional photoanode exhibited a synergetic effect on the decomplexation of Ni-EDTA with the pseudo-first-order rate constant of 0.01068 min−1 with 180 min by using stainless steel (SS) cathode, which was 1.5 and 2.4 times higher than that of TiO2 photoanode and Ni-Sb-SnO2 anode, respectively. Moreover, both the efficiencies of Ni-EDTA decomplexation and Ni recovery were improved to 98% from 86% and 73% from 41% after replacing SS cathode with ACF cathode, respectively. Influencing factors on Ni-EDTA decomplexation and Ni recovery were investigated and the efficiencies were favored at acidic condition, higher cell voltage and lower initial Ni-EDTA concentration. Ni-EDTA was mainly decomposed via ·OH radicals which generated via the interaction of O3, H2O2, and UV irradiation in the contrasted PEC system. Then, the liberated Ni2+ ions which liberated from Ni-EDTA decomplexation were eventually reduced to metallic Ni on the ACF cathode surface. Finally, the stability of the constructed PEC system on Ni-EDTA decomplexation and Ni recovery was exhibited.  相似文献   
149.
2015年强厄尔尼诺引起东南亚干旱少雨与活跃火加剧,但目前有关活跃火时空特征、发生类型与强度及其对人口—社会经济影响仍分析不足。利用美国国家航空航天局火灾信息资源管理系统(FIRMS)VIIRS V1活跃火位置矢量产品,通过月际、地形、土地覆被类型等GIS分析确定东南亚主要国家活跃火主要类型,并评价各国活跃火对人口分布的影响范围与国别差异。结果表明:(1)东南亚2015年活跃火发生频次达81.40×105次,中南半岛与马来群岛各占69.60%与30.40%,分别集中发生在2-4月与8-10月,各国活跃火频次与发生时间差异很大。(2)中南半岛五国活跃火地形差异明显,缅甸和越南活跃火集中分布于25 m以下;老挝(85~105 m、140~200 m)、泰国(5~15 m、70~110 m)和柬埔寨(5~15 m、70~110 m)活跃火随海拔呈双峰特征;马来群岛国家(印度尼西亚、马来西亚与菲律宾)活跃火集中分布于60 m以下的平原地带;且东南亚35%以上的活跃火均集中分布5~15°的斜坡。(3)东南亚森林、农田活跃火发生率为76%,其中森林活跃火发生率由柬埔寨的52.00%到老挝的74.27%不等,农田活跃火由老挝的13.18%到泰国的42.68%不等。(4)综合活跃火发生月份、海拔、坡度与覆被特征,可从山区刀耕火种农业与平原秸秆焚烧界定东南亚主要国家活跃火发生类型。(5)东南亚活跃火随人口密度增加呈先增后减至平稳变化的趋势,且多集中于人口稀少的乡村和原始森林,其中缅甸、泰国、越南三国有10%以上的活跃火发生在人口密度为72~91人/km2的区域,而马来西亚、老挝、柬埔寨、印度尼西亚30%以上的活跃火集中发生于人口密度在20人/km2以下的区域。  相似文献   
150.
目的研究35Cr2Ni4MoA材料镀硬铬表面的腐蚀行为特点。方法开展35Cr2Ni4MoA材料在实验室湿热环境和盐雾环境的加速腐蚀环境试验,分析腐蚀环境对35Cr2Ni4MoA材料镀硬铬表面腐蚀行为的影响,加速腐蚀试验共8个周期,通过蚀坑深度、蚀坑面积、单面面积腐蚀数量描述材料表面腐蚀情况。结果35Cr2Ni4MoA在实验室腐蚀环境下蚀坑深度随时间变化满足幂函数关系,蚀坑半径随时间满足线性关系。实验前期单位面积内点蚀数量较多,腐蚀程度轻,在试验中后期点蚀扩展相连,腐蚀面积变大,腐蚀数量减少,腐蚀程度加重。结论提高35Cr2Ni4MoA材料镀硬铬表面处理质量,减少材料表面处理孔隙,能有效提高35Cr2Ni4MoA材料的腐蚀防护能力。  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