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   924篇
  免费   71篇
  国内免费   157篇
安全科学   95篇
废物处理   20篇
环保管理   172篇
综合类   402篇
基础理论   214篇
环境理论   1篇
污染及防治   93篇
评价与监测   36篇
社会与环境   66篇
灾害及防治   53篇
  2024年   2篇
  2023年   16篇
  2022年   25篇
  2021年   31篇
  2020年   28篇
  2019年   20篇
  2018年   27篇
  2017年   27篇
  2016年   35篇
  2015年   34篇
  2014年   30篇
  2013年   54篇
  2012年   55篇
  2011年   66篇
  2010年   57篇
  2009年   51篇
  2008年   66篇
  2007年   63篇
  2006年   45篇
  2005年   41篇
  2004年   51篇
  2003年   37篇
  2002年   27篇
  2001年   34篇
  2000年   38篇
  1999年   30篇
  1998年   31篇
  1997年   18篇
  1996年   25篇
  1995年   13篇
  1994年   11篇
  1993年   3篇
  1992年   11篇
  1991年   7篇
  1990年   10篇
  1989年   2篇
  1988年   8篇
  1987年   5篇
  1986年   3篇
  1985年   1篇
  1984年   3篇
  1982年   1篇
  1981年   2篇
  1979年   2篇
  1978年   1篇
  1977年   3篇
  1974年   1篇
  1971年   1篇
排序方式: 共有1152条查询结果,搜索用时 15 毫秒
331.
根据浙江省舟山海洋生态环境监测站多年资料,对浙江省近岸海域环境功能区达标趋势及影响因素进行分析。结果表明,2009年浙江近岸海域环境功能区平水期、丰水期、枯水期达标面积分别为9541、10715、842km2,全年达标面积7333km2,占所监测海域面积的16.4%。浙江省近岸海域环境功能区水质达标的主要超标指标为无机氮和活性磷酸盐,另有部分区域溶解氧、化学需氧量、pH指标超标。整个杭州湾水体处于严重富营养化水平,象山湾和泗礁-大衢-岱山岛以西的舟山海域处于中度富营养化水平。东经122度以东的舟山海域及浙中南近岸海域处于轻度富营养或贫营养水平,2002年以来浙江近岸海域水体的富营养化程度逐步下降。2001—2004年近岸海域环境功能区达标率均低于3%,达标区主要分布在舟山海域,2005年开始达标区域扩展到温州海域,"十一五"以来浙江省近岸海域环境功能区水质达标率呈增加趋势。  相似文献   
332.
The vulnerability of low-lying coastal areas in Turkey to inundation was quantified based on the sea-level rise scenarios of 1, 2, and 3 m by 2205. Through digital elevation model (DEM) acquired by the shuttle radar topography mission (SRTM), the extent and distribution of the high to low-risk coastal plains were identified. The spatio-temporal analysis revealed the inundated coastal areas of 545, 1,286, and 2,125 km2 at average rates of 5, 10, and 15 mm yr−1 for 200 years, respectively. This is equivalent to minimum and maximum land losses by 2205 of 0.1–0.3% of the total area and of 1.3–5.2% of the coastal areas with elevations of less than 100 m in the country, respectively. This study provides an initial assessment of vulnerability to sea-level rise to help decision-makers, and other concerned stakeholders to develop appropriate public policies and land-use planning measures.  相似文献   
333.
颗粒物激光雷达在大气复合污染立体监测中的应用   总被引:4,自引:4,他引:0  
针对由于局地污染、沙尘输入、外源性输入与局地污染物相互叠加所导致的3种灰霾污染发生过程,分别选取3个典型案例,采用颗粒物激光雷达对污染物的时空分布特征进行解析。研究发现,在局地污染发生时,污染物从地面开始垂直向上扩散,扩散高度约1 km。重度污染过程中,气溶胶的日均垂直消光系数随高度的变化背离指数衰减特征,800 m高度处出现消光系数的极大值层,极大值超过2.5 km-1,800 m以下消光系数近乎常数,约为0.3 km-1。这说明,重污染过程中,有一层较厚重的颗粒物分布,使近地面污染物在垂直方向的扩散能力减弱,形成积累效应,造成大面积空气混浊。当有外源性沙尘输入时,激光雷达能够清晰地监测到污染团输入的全过程。沙团突然出现在高空2~3 km。污染团退偏振度较大,超过0.3。随着沙尘粒子的重力沉降,沙团的轮廓在垂直方向上不断地增大。沙团的输入,导致近地面粗颗粒质量浓度的增加幅度明显大于细颗粒。在第3个案例中,激光雷达清晰地监测到高空1.8~3 km突然出现含有大量球形细颗粒的污染团,同时还发现此污染团与近地面的污染物有不同的演化特征。近地面污染物随时间垂直向上扩散,12:00左右扩散高度超过1.8 km。而高空的污染团逐渐沉降进入边界层内,与近地面扩散的污染物相互混合,共同导致本地的灰霾天气。综上所述,激光雷达可以清晰地捕获污染物的垂直结构特征,对不同的致霾过程进行立体解析,实现对大气复合污染的监测和机理研判。  相似文献   
334.
基于突变级数法的中国低碳经济复杂系统综合评价   总被引:2,自引:0,他引:2  
低碳经济是人类社会实现可持续发展的内在要求和重要途径,是应对气候变化的必然选择。首先界定了低碳经济SREE复杂系统,该系统由社会、资源、经济和环境4个相互独立又相互联系的子系统构成的复杂巨系统。以此为基础,构建了包括经济系统、资源环境系统和社会系统在内的低碳经济复杂系统综合评价指标体系。考虑到运用突变级数法对指标体系进行评价的需要,指标体系全部由定量指标构成,避免了人为确定定性指标权重的主观性。其次,运用突变级数评价方法对2005~2009年的中国低碳经济复杂系统进行了评价。从评价结果来看,我国低碳经济复杂系统按照波浪型曲线运行,这是国际金融危机和国内经济结构调整双重因素导致的结果,同时也是复杂系统内部子系统相互影响、相互作用的结果。最后,提出了当前中国低碳经济复杂系统可持续发展的相应战略  相似文献   
335.
The chlorophenoxy herbicide MCPA (4-chloro-2-methylphenoxyacetic acid), widely used for the control of broad-leaf weeds primarily in cereal and grass seed crops, still remains one of the most often used herbicides in Portugal. As the formation of inclusion complexes with cyclodextrins can improve its solubility properties, the interaction between the herbicide MCPA and β-cyclodextrin was investigated. The stability constants describing the extent of formation of the complexes have been determined by phase-solubility studies. Different analytical techniques [ultraviolet-visible spectroscopy (UV-Vis), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (1H NMR)] were employed for a thorough investigation of the structural characteristics of the obtained complexes, which exhibited distinct features and properties from both “guest” and “host” molecules. FTIR and 1H NMR data obtained for the MCPA/β-CD complexes gave information about the interaction between MCPA and the nonpolar cyclodextrin cavity. The dramatic change observed in band frequency and proton displacements of OCH2 group and H6 aromatic proton confirmed the inclusion of MCPA in β-CD.

The formation of an inclusion complex between MCPA and β-CD increased the aqueous solubility of this herbicide which could be a particularly advantageous property for some specific applications, namely to improve commercial formulation and for environmental protection.  相似文献   
336.
采用硅藻土对聚合硫酸铁(PFS)、聚合氯化铝(PAC)的混凝能力进行强化,并用于线路板含络合铜废水中铜的去除。考察了硅藻土加入量、混凝剂加入量、pH、快速搅拌速率和沉淀时间等因素对除铜效果的影响,并与目前常用的硫化钠破络方法进行了对比。实验结果表明:硅藻土强化混凝的除铜效果明显好于单独投加PAC或PFS;PFS-硅藻土除铜效果好于PAC-硅藻土;在pH为8.0~9.0、硅藻土加入量为120 mg/L、PFS加入量为60 mg/L、快速搅拌速率为250 r/min的条件下,沉淀40 min后可使出水铜质量浓度低于0.30 mg/L,比传统破络工艺出水水质更稳定,成本更低。  相似文献   
337.
G?ran Sundblad  Ulf Bergstr?m 《Ambio》2014,43(8):1020-1028
Coastal development has severely affected habitats and biodiversity during the last century, but quantitative estimates of the impacts are usually lacking. We utilize predictive habitat modeling and mapping of human pressures to estimate the cumulative long-term effects of coastal development in relation to fish habitats. Based on aerial photographs since the 1960s, shoreline development rates were estimated in the Stockholm archipelago in the Baltic Sea. By combining shoreline development rates with spatial predictions of fish reproduction habitats, we estimated annual habitat degradation rates for three of the most common coastal fish species, northern pike (Esox lucius), Eurasian perch (Perca fluviatilis) and roach (Rutilus rutilus). The results showed that shoreline constructions were concentrated to the reproduction habitats of these species. The estimated degradation rates, where a degraded habitat was defined as having ≥3 constructions per 100 m shoreline, were on average 0.5 % of available habitats per year and about 1 % in areas close to larger population centers. Approximately 40 % of available habitats were already degraded in 2005. These results provide an example of how many small construction projects over time may have a vast impact on coastal fish populations.

Electronic supplementary material

The online version of this article (doi:10.1007/s13280-014-0522-y) contains supplementary material, which is available to authorized users.  相似文献   
338.
Zhu FD  Choo KH  Chang HS  Lee B 《Chemosphere》2012,87(8):857-864
The fate of endocrine disrupting chemicals (EDCs) in natural and engineered systems is complicated due to their interactions with various water constituents. This study investigated the interaction of bisphenol A (BPA) with dissolved organic matter (DOM) and colloids present in surface water and secondary effluent as well as its adsorptive removal by powdered activated carbons. The solid phase micro-extraction (SPME) method followed by thermal desorption and gas chromatography-mass spectrometry (GC-MS) was utilized for determining the distribution of BPA molecules in water. The BPA removal by SPME decreased with the increased DOM content, where the formation of BPA-DOM complexes in an aqueous matrix was responsible for the reduced extraction of BPA. Colloidal particles in water samples sorbed BPA leading to the marked reduction of liquid phase BPA. BPA-DOM complexes had a negative impact on the adsorptive removal of BPA by powered activated carbons. The complex formation was characterized based on Fourier transform infrared (FTIR) and ultraviolet-visible (UV-Vis) spectroscopy, along with the calculation of molecular interactions between BPA and functional groups in DOM. It was found that the hydrogen bonding between DOM and BPA would be preferred over aromatic interactions. A pseudo-equilibrium molecular coordination model for the complexation between a BPA molecule and a hydroxyl group of the DOM was developed, which enabled estimation of the maximum sorption site and complex formation constant as well as prediction of organic complexes at various DOM levels.  相似文献   
339.
对大型燃煤电站电一袋复合除尘技术进行了较全面的分析研究,如气流组织最优方案确定、脉冲喷吹系统选型及参数优化、粉尘荷电对滤料阻力的影响及高压电源的优选等。研究表明对电袋复合除尘器来说,袋式除尘区采用阶梯式布置是一种较为理想的气流组织方式,活塞式脉冲阀具有更好的清灰性能,粉尘的荷电有助于减小除尘设备的阻力,三相电源的性能优于单相电源。  相似文献   
340.
采用不同的破络合剂处理化学镀镍废水,探讨了CaO、CaCl2和BaCl2 3种破络合剂处理化学镀镍废水时,对Ni2+去除率的影响,同时对CaO联合BaCl2处理化学镀镍废水进行了研究。实验结果表明,CaO、CaCl2和BaCl2的使用量分别为3.0、6.0和4.5 g/L时,Ni2+去除率分别为32%、19%和99.9...  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