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   1720篇
  免费   96篇
  国内免费   678篇
安全科学   84篇
废物处理   124篇
环保管理   125篇
综合类   997篇
基础理论   300篇
环境理论   2篇
污染及防治   591篇
评价与监测   85篇
社会与环境   64篇
灾害及防治   122篇
  2023年   26篇
  2022年   92篇
  2021年   86篇
  2020年   53篇
  2019年   56篇
  2018年   61篇
  2017年   67篇
  2016年   84篇
  2015年   97篇
  2014年   126篇
  2013年   132篇
  2012年   136篇
  2011年   164篇
  2010年   132篇
  2009年   111篇
  2008年   113篇
  2007年   85篇
  2006年   96篇
  2005年   59篇
  2004年   67篇
  2003年   51篇
  2002年   61篇
  2001年   52篇
  2000年   57篇
  1999年   58篇
  1998年   57篇
  1997年   63篇
  1996年   49篇
  1995年   48篇
  1994年   29篇
  1993年   38篇
  1992年   21篇
  1991年   13篇
  1990年   12篇
  1989年   5篇
  1988年   8篇
  1987年   11篇
  1986年   3篇
  1985年   4篇
  1984年   3篇
  1983年   1篇
  1982年   1篇
  1981年   5篇
  1930年   1篇
排序方式: 共有2494条查询结果,搜索用时 15 毫秒
141.
壳聚糖三元接枝共聚物的合成及其阻垢性能   总被引:1,自引:1,他引:0  
以壳聚糖(CTS)、衣康酸(IA)和马来酸酐(MA)为原料,以醋酸为溶剂、(NH_4)_2S_2O_8为引发剂,合成了CTS-IA-MA三元接枝共聚物。聚合反应的最佳条件为:反应温度90℃,n(CTS):n(IA):n(MA)=1:1.5:1.0,引发剂质量分数0.35%,反应时间5 h。通过傅立叶变换红外光谱(FTIR)表征,所得产物为CTS-IA-MA接枝共聚物。三元接枝共聚物质量浓度为50 mg/L、水样pH为中性或弱酸性时三元接枝共聚物对CaCO_3的阻垢效果较好。  相似文献   
142.
采用含固定化微生物的曝气生物滤池(G-BAF)处理炼油厂高浓度废水。当G-BAF池进水COD为298~11 278 mg/L时,出水COD为33.0~94.3 mg/L,COD平均去除率为97%;当G-BAF池进水ρ(NH_3-N)为12.1~188.0 mg/L时,出水ρ(NH_3-N)为0.9~49.4 mg/L,NH_3-N平均去除率为83%。经G-BAF处理后出水水质完全达到GB8978—1996《污水综合排放标准》第二类污染物的二级排放标准。  相似文献   
143.
Carbonaceous aerosols were studied at three background sites in south and southwest China. Hok Tsui in Hong Kong had the highest concentrations of carbonaceous aerosols (OC = 8.7 ± 4.5 μg/m3, EC = 2.5 ± 1.9 μg/m3) among the three sites, and Jianfeng Mountains in Hainan Island (OC = 5.8 ± 2.6 μg/m3, EC = 0.8 ± 0.4 μg/m3) and Tengchong mountain over the east edge of the Tibetan Plateau (OC = 4.8 ± 4.0 μg/m3, EC = 0.5 ± 0.4 μg/m3) showed similar concentration levels. Distinct seasonal patterns with higher concentrations during the winter, and lower concentrations during the summertime were observed, which may be caused by the changes of the regional emissions, and monsoon effects. The industrial and vehicular emissions in East, Southeast and South China, and the regional open biomass burning in the Indo-Myanmar region of Asia were probably the two major potential sources for carbonaceous matters in this region.  相似文献   
144.
采用自行研制的生物转鼓过滤器(RDB)反硝化净化NO。结果表明,在实验温度为25~30℃、pH为7.0~7.5、转鼓转速为1.0r/min、空床停留时间(EBRT)为86.40s、营养液用量为5.0L、营养液更换频率为0.2L/d的条件下,RDB在30d内完成挂膜;RDB稳定运行期间,当NO进气质量浓度为90~433mg/m3时,NO去除率维持在42.9%~85.2%,平均去除负荷为10.40g/(m3.h);转鼓转速决定了生物膜表面的更新速率和液膜厚度,当转速为0.5r/min时,NO去除率达到最大值(75.0%);将营养液用量控制在1.3~3.0L较为合理;EBRT是决定反硝化效率的重要因素,当EBRT为345.60s时,NO去除率不受其进气浓度的影响,且去除率高达95%以上,当EBRT为43.20s、NO进气质量浓度从98mg/m3增加到1095mg/m3时,NO去除率从62.5%下降到30.7%,当进气负荷为50.00g/(m3.h)时,NO去除负荷达到最大值(27.50g/(m3.h))。  相似文献   
145.
In urban cities in Southern China, the tissue S/N ratios of epilithic mosses (Haplocladium microphyllum), varied widely from 0.11 to 0.19, are strongly related to some atmospheric chemical parameters (e.g. rainwater SO42−/NH4+ ratios, each people SO2 emission). If tissue S/N ratios in the healthy moss species tend to maintain a constant ratio of 0.15 in unpolluted area, our study cities can be divided into two classes: class I (S/N > 0.15, S excess) and class II (S/N < 0.15, N excess), possibly indicative of stronger industrial activity and higher density of population, respectively. Mosses in all these cities obtained S and N from rainwater at a similar ratio. Sulphur and N isotope ratios in mosses are found significantly linearly correlated with local coal δ34S and NH4+-N wet deposition, respectively, indicating that local coal and animal NH3 are the major atmospheric S and N sources.  相似文献   
146.

Purpose

The environmental issues caused by the municipal solid waste disposal are becoming a worldwide concern.

Methods

We studied the situations both domestically and abroad by the strategic environmental assessment (SEA) approach and also conducted comprehensive evaluations of garbage disposal in Changchun City.

Results

On the basis of this study, we found that SEA is of great importance in the municipal solid waste disposal. Moreover, with the rapid socioeconomic development of Changchun City, municipal solid waste production increases on an annual basis, and thus, good waste management planning is of great significance.

Conclusions

Considering the situation of the economic development of Changchun City, garbage disposal was handled mainly in the major sanitary landfills with appropriate use of incineration technology. This plan is environmentally friendly at a relatively high degree and has met the requirements of minimum investment. It also takes into account the requirements of the development of incineration technology. Regarding environmental pollution in terms of groundwater pollution and atmospheric pollution, this plan is a feasible one by meeting various requirements with low environmental impact among the three plans discussed in this study.  相似文献   
147.
Based on environmental monitoring data in 93 major cities and meteorological records at 398 weather stations in China from 1981 to 2007, total suspended particle (TSP) concentration, the intensity of dustfall, and sand and dust storm frequency (Fd) were analysed. During the past 27 years, the annual average TSP concentration (CTSP) in 93 cities was 402 μg m?3. Annual average CTSP decreased from the north to the south and from inland to the coast areas with a peak value of 628.8 μg m?3 in Lanzhou. In the 1980s, 1990s and 2000s, annual average CTSP was 628.7, 319.2, and 250.1 μg m?3, respectively. Annual average intensity of dustfall (Id) was 240.5 t km?2 a?1, decreased from northern to southern China and from inland to the coast areas with the maximum value of 717.2 t km?2 a?1 in Baotou. In the 1980s, 1990s and 2000s, annual average Id was 334.8, 220.9, 146 t km?2 a?1 respectively. Annual average Id in the Loess Plateau region was commonly higher than 200 t km?2 a?1. The annual average Fd decreased from arid regions in northwestern China to humid areas in southeastern China with two sand and sand storm centers existing in Xinjiang Taklamakan Desert and western Inner Mongolia. The annual average Fd in the 1980s, 1990s, 2000s was 16, 8, 6 days respectively, decreased steadily from 18 days in 1981–5 days in 2007. Annual average Id had a positive linear relation to annual average CTSP (R2 = 0.96). Annual average Fd had a positive relation with annual average CTSP (R2 = 0.97) as well as annual average Id (R2 = 0.94). TSP was the chief pollutant influencing Air Pollution Index (API) in northern China in spring and winter seasons. Sand and dust storm might be a major factor affecting the temporal variability and spatial distribution of TSP and dustfall in China.  相似文献   
148.
Polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/PCDF) were overall measured and compared in ambient air, water, soils, and sediments along the upper reaches of the Haihe River of North China, so as to evaluate their concentrations, profiles, and to understand the processes of gas–particle partitioning and air–water/soil exchange. The following results were obtained: (1) The average concentrations (toxic equivalents, TEQs) of 2,3,7,8-PCDD/PCDF in air, water, sediment, and soil samples were 4,855 fg/m3, 9.5 pg/L, 99.2 pg/g dry weight (dw), and 56.4 pg/g (203 fg TEQ/m3, 0.46 pg TEQ/L, 2.2 pg TEQ/g dw, and 1.3 pg TEQ/g, respectively), respectively. (2) Although OCDF, 1,2,3,4,6,7,8-HpCDF, OCDD, and 1,2,3,4,6,7,8-HpCDD were the dominant congeners among four environmental sinks, obvious discrepancies of these congener and homologue patterns of PCDD/PCDF were observed still. (3) Significant linear correlations for PCDD/PCDF were observed between the gas–particle partition coefficient (K p) and the subcooled liquid vapor pressure (P L 0) and octanol–air partition coefficient (K oa). (4) Fugacity fraction values of air–water exchange indicated that most of PCDD/PCDF homologues were dominated by net volatilization from water into air. The low-chlorinated PCDD/PCDF (tetra- to hexa-) presented a strong net volatilization from the soil into air, while high-chlorinated PCDD/PCDF (hepta- to octa-) were mainly close to equilibrium for air–soil exchange.  相似文献   
149.
低温选择性催化还原(SCR)脱硝是国内外脱硝技术研发的热点,但目前主要集中在实验室小试范围,无法完全反映催化剂在实际烟气中的运行状况。在30 t/h循环流化床燃煤锅炉脱硫除尘装置后建设了2 000~5 000 m3/h的SCR脱硝中试装置,经系统研究发现,中试使用的蜂窝式催化剂对SO2和NO具有很强的吸附能力,且反应温度、喷氨速率和气体空速均会影响催化脱硝效率。为期5 d的连续运行实验结果表明,催化剂的脱硝效率一直稳定在30%~50%,并未发现明显的失活,这证明设计除雾除尘器、较大的混合器、混合器与反应器间较长的管路均有利于缓解催化剂因SO2、H2O和飞灰中的碱性金属导致的失活。  相似文献   
150.
为了研究表面分子印迹聚合物对基质复杂的环境样品中的土霉素的吸附分离效果,以应用最为广泛的土霉素(OTC)为研究对象,利用甲基丙烯酸和甲基丙烯酸甲酯为双功能单体、在二氧化硅基质上制备了表面分子印迹聚合物,并对其吸附鸡粪中的四环素类抗生素进行了研究。以聚合物的吸附容量和印迹因子为考核指标,对两种单体的投加比例和二氧化硅的用量进行了优化,确定其合成最佳条件:二氧化硅用量为15 mmol、单体总量一定时各物质的摩尔比为OTC∶MAA∶MMA∶EGDMA=0.08∶2.0∶2.0∶8.0。在此条件下合成的表面印迹聚合物对鸡粪基质中的OTC的最大吸附量可达到9.67 mg/g,印迹因子4.69,可见该表面印迹聚合物对复杂环境样品中的OTC也有良好的吸附性能和识别性能。  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