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   758篇
  免费   131篇
  国内免费   69篇
安全科学   5篇
废物处理   7篇
环保管理   60篇
综合类   430篇
基础理论   216篇
污染及防治   122篇
评价与监测   42篇
社会与环境   35篇
灾害及防治   41篇
  2023年   3篇
  2022年   12篇
  2021年   27篇
  2020年   20篇
  2019年   25篇
  2018年   19篇
  2017年   19篇
  2016年   22篇
  2015年   19篇
  2014年   45篇
  2013年   107篇
  2012年   64篇
  2011年   79篇
  2010年   44篇
  2009年   54篇
  2008年   47篇
  2007年   56篇
  2006年   41篇
  2005年   42篇
  2004年   24篇
  2003年   29篇
  2002年   29篇
  2001年   20篇
  2000年   19篇
  1999年   16篇
  1998年   15篇
  1997年   9篇
  1996年   16篇
  1995年   5篇
  1994年   6篇
  1993年   6篇
  1992年   7篇
  1991年   4篇
  1990年   2篇
  1989年   1篇
  1988年   1篇
  1987年   1篇
  1985年   1篇
  1983年   2篇
排序方式: 共有958条查询结果,搜索用时 31 毫秒
1.
Riverine nutrient loads are among the major causes of eutrophication of the Baltic Sea. This study applied the Soil & Water Assessment Tool (SWAT) in three catchments flowing to the Baltic Sea, namely Vantaanjoki (Finland), Fyrisån (Sweden), and Słupia (Poland), to simulate the effectiveness of nutrient control measures included in the EU’s Water Framework Directive River Basin Management Plans (RBMPs). Moreover, we identified similar, coastal, middle-sized catchments to which conclusions from this study could be applicable. The first modelling scenario based on extrapolation of the existing trends affected the modelled nutrient loads by less than 5%. In the second scenario, measures included in RBMPs showed variable effectiveness, ranging from negligible for Słupia to 28% total P load reduction in Vantaanjoki. Adding spatially targeted measures to RBMPs (third scenario) would considerably improve their effectiveness in all three catchments for both total N and P, suggesting a need to adopt targeting more widely in the Baltic Sea countries.Electronic supplementary materialThe online version of this article (10.1007/s13280-020-01393-x) contains supplementary material, which is available to authorized users.  相似文献   
2.
Dense blooms of diazotrophic filamentous cyanobacteria are formed every summer in the Baltic Sea. We estimated their contribution to nitrogen fixation by combining two decades of cyanobacterial biovolume monitoring data with recently measured genera-specific nitrogen fixation rates. In the Bothnian Sea, estimated nitrogen fixation rates were 80 kt N year−1, which has doubled during recent decades and now exceeds external loading from rivers and atmospheric deposition of 69 kt year−1. The estimated contribution to the Baltic Proper was 399 kt N year−1, which agrees well with previous estimates using other approaches and is greater than the external input of 374 kt N year−1. Our approach can potentially be applied to continuously estimate nitrogen loads via nitrogen fixation. Those estimates are crucial for ecosystem adaptive management since internal nitrogen loading may counteract the positive effects of decreased external nutrient loading.  相似文献   
3.
渤海湾入海溶解无机氮总量控制研究   总被引:1,自引:0,他引:1  
基于渤海湾近岸海域的实际调查结果,采取生态物理耦合模型,对渤海湾的主要污染物-溶解无机氮(DIN)的基准环境容量和极小剩余海洋环境容量进行了计算。结果表明,渤海湾DIN的极小剩余海洋环境容量在Ⅰ类和Ⅱ类水质标准下均为负值,渤海湾的DIN已经超标。结合实际的海水功能区水质管理目标,应重点控制非点源的排放,加强上游携带入境污染物的处理,从总量上控制DIN入海污染通量,改善渤海湾水质。  相似文献   
4.
Dissolved iron (Fe) distribution and speciation was determined in water samples (0–200?m) collected in a coastal area near Terra Nova Bay during the austral summer of 2014. Nutrients, dissolved oxygen, chlorophyll-a, phytoplankton composition and prokaryotic biomass distribution were investigated in combination with measurements of the physical properties of the water columns and its dynamics. The dFe value was above the limiting growth concentration, ranging from 0.52 to 4.51?nM, and it showed a spatial variability with a horizontal length scale of about 10?km, according to the variability of the water column physical properties and to iron sources. The organic ligands (L) maintained the concentrations of dFe at levels much higher than the inorganic solubility of Fe, keeping it available for phytoplankton and the log K’FeL values found (from 22.1 to 23.6) highlighted the presence of complexes of differing stabilities.  相似文献   
5.
南黄海2007—2017年浮游植物群落结构及多样性变化   总被引:3,自引:0,他引:3  
在2007-2017年秋季,利用专业海洋调查船对整个南黄海海域开展了5个航次的浮游植物调查。结果发现:调查海域共有浮游植物371种,隶属4门108属。其中硅藻门有56属237种,甲藻门有24属98种,硅藻和甲藻是组成南黄海海域浮游植物最主要的两大类群。主要优势种有裸甲藻(Gymnodinium sp.)、柔弱拟菱形藻(Nitz.delicatissima)、蓝隐藻(Chroomonas sp.)、菱形海线藻(Thalassionema nitzschioides)、锥状施克里普藻(Scrippsiella trochoidea)和环沟藻(Gyrodinium spp.)等。2007年以来,南黄海浮游植物种类数呈明显上升趋势。浮游植物细胞密度平均为1.96×104个/L,年际变化较大。将调查结果与众多文献比对,共发现9种藻类为中国新记录藻种,其中有4种硅藻和5种甲藻。  相似文献   
6.
Coastal areas of Iran are heavily affected by urbanisation, industrialisation, and maritime activities. One consequence of this environmental pressure is the contaminants accumulation, as heavy metals, into the marine ecosystem. In this review, the coastal areas in the north and south of the country were assessed for lead (Pb) contamination of, one of the most toxic metals found in the environment. All studies conducted during 2006–2016 with at least 10 specimens that reported the mean and standard deviation of Pb were considered in this review. Heterogeneity between studies was assessed using the Q and I2 statistics. The Pb mean concentration overall studies was estimated to be 21.88?µg/g (95% CIs: 16.25–27.50). Random effect model showed no statistical difference in mean Pb concentration levels between south and north coasts. However, the variability in Pb mean concentrations within southern coasts was considerable and statistically significant. Moreover, the Pb concentrations in the northern coasts of Persian Gulf and Oman Sea, in south of Iran, decreased in the following order Hormozgan > Khuzestan > Sistan-VA-Balluchestan > Bushehr while in the southern coasts of Caspian Sea, in north of Iran, decreased in the order Guilan > Mazandaran > Golestan.  相似文献   
7.
长江口及邻近海域富营养化趋势分析及与环境因子关系   总被引:1,自引:0,他引:1  
依据2007-2009年春、夏季在长江口及邻近海域(包括长江口、杭州湾和舟山渔场)的调查监测资料,采用富营养指数法、潜在性富营养化法和有机污染指数法对该海域的富营养化状况、时空分布特征及与环境因子的关系进行了分析评价。富营养指数法计算结果表明:富营养化覆盖比例很高,达到70%以上;在春季,该海域的富营养化程度呈现上升趋势,所占比例从2007年的77.0%上升到2009年的89.8%,在夏季最低达到89.3%,最高到100.0%。3年来,富营养化在春、夏2季基本上处于逐年增加趋势,富营养化趋势越来越明显。在春季富营养指数平面分布呈由近岸向远海逐渐递减的趋势,梯度分布明显,其中,杭州湾富营养化情况较严重;夏季其平面分布与春季类似,但长江口和杭州湾两个水域的富营养指数的等值线都比较密集,夏季的富营养化情况较为严重。潜在性富营养化法计算结果表明:该海域富营养级主要集中在III级(富营养)和V P级(磷中等限制潜在性富营养);春、夏2季时,长江口V P级所占比例均从0.0%增加到66.7%,受磷限制性富营养化程度越来越高。另外,营养盐结构显示,N/P比值从9.1到50.9,营养盐比例明显不平衡,势必影响浮游生物的生长。有机污染指数法计算结果表明:该海域有机污染指数主要处于5级(重污染),水质污染严重;长江口春、夏2季5级的比例均从50.0%分别上升到83.3%和100.0%,杭州湾分别从60.0%和80.0%均上升到100.0%;舟山渔场分别从22.2%和66.7上升到66.7%和77.7%,说明受污染程度逐年上升。另外,3年来春、夏2季长江口有机污染指数达5级的占50%以上,杭州湾60%以上,舟山渔场20%以上,杭州湾受污染情况最为严重,其次是长江口,舟山渔场最小。在春、夏2季有机污染平面分布表现为污染程度从西向东、从北向南逐渐降低?  相似文献   
8.
对渤海4个重点监测排污口(北塘、大蒲河、弥河和虞河)邻近海域异养细菌的组成和分布进行了调查研究。结果表明,分离到的各排污口邻近海域的细菌隶属于变形菌门(Proteobacteria)、厚壁菌门(Firmicutes)、放线菌门(Acti-nobacteria)和拟杆菌门(Bacteroidetes)4个细菌类群,其中变形菌门的细菌最丰富。各排污口的优势菌有所不同,北塘、弥河2个采样点的优势菌分别为Bacillus sp.、Pseudoalteromonas sp.,大蒲河采样点的优势菌为Vibrio sp.和Oceanospirillum sp.,虞河采样点的优势菌为 Shewanella sp.和 Bacillus sp.。多维尺度分析表明,北塘和虞河采样点的细菌种群特征较相近,细菌种群分布特征可能与排污口的海洋环境有一定的相关性。  相似文献   
9.
PM10作为大气污染物监测的主要指标之一,探究大气PM10浓度对大气环境质量和人体健康评价具有重要意义。黄、渤海滨海带包括京、津和辽、冀、鲁、苏等工、农业大省,区域大气PM10污染的时空分布和来源特征具有复杂性和典型性。在锦州、北京、天津、烟台、青岛、连云港和盐城7个城市布设10个采样点,含7个城市点和3个农村点,开展为期一年的大气颗粒物的采样;同时,于冬季1月和夏季7月在锦州、天津和烟台进行合计60 d的加密采样,藉以确定研究区域大气PM10的时空分布和来源特征。结果表明,黄、渤海滨海带大气年均PM10总浓度为(129’18)"g·m~(-3),单月最低值出现在2015年7月盐城农村样点15"g·m~(-3),最高值为2015年3月北京城市点307"g·m~(-3)。盐城大气PM10浓度(城市点(85’27)"g·m~(-3)和农村点(66’35)"g·m~(-3))显著低于其他样点大气PM10浓度。渤海滨海带中西部的京(140’68"g·m~(-3))、津(169’60"g·m~(-3))两市大气PM10年均浓度显著高于东部的锦州(125’41"g·m~(-3))和烟台(109’31"g·m~(-3));而且黄海滨海带大气PM10年均浓度(114"g·m~(-3))显著低于渤海滨海带年均浓度(136"g·m~(-3)),总体上表现出西高东低、北高南低的特征。黄、渤海滨海带城市点和农村点年均浓度分别为(129’18)"g·m~(-3)和(112’30)"g·m~(-3);农村点春冬季大气PM10浓度和城市点浓度相当,无显著差异,夏秋季大气PM10浓度略低于城市浓度,表明农村地区大气颗粒物污染情况也较为严重,需受到关注。区域内PM10浓度季节变化整体表现为春冬高、夏秋低。利用多元回归分析初步判断黄、渤海滨海带PM10属于复合来源,大气PM10浓度约30%的变化与降水、人均能耗和沙尘天气相关。黄、渤海滨海带大气PM10浓度的昼夜变化不大,大气PM10浓度与气温呈现正相关,与风速和降水呈现负相关,表现为受各种气象因素综合作用的影响。  相似文献   
10.
While scholars have showed a long-standing interest for how to design effective environmental treaties and other international agreements, less interest has been paid to implementation phases of these agreements. This article takes the Eutrophication Segment in the Baltic Sea Action Plan as an example of a regional effort to reduce nutrient leakages, where national reporting of adopted strategies has been a key mechanism to improve implementation effectiveness. It is shown that although transnational collective action theory is a powerful tool to analyse underlying drivers and priorities in state implementation policies, a deeper analysis of domestic and external constraints can shed additional light on observed implementation gaps. Varying views among countries on, for example, the role of stakeholder participation, legitimacy and top-down governing versus multi-stakeholder governance approaches may comprise domestic constraints that make effective and efficient implementation problematic. In terms of external constraints, states’ balancing of action plan objectives versus other international commitments, such as other environmental treaties and EU Directives, is shown to potentially reduce implementation efficiency as well.  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