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   2008篇
  免费   162篇
  国内免费   290篇
安全科学   324篇
废物处理   144篇
环保管理   409篇
综合类   1050篇
基础理论   177篇
环境理论   4篇
污染及防治   207篇
评价与监测   68篇
社会与环境   57篇
灾害及防治   20篇
  2024年   2篇
  2023年   16篇
  2022年   24篇
  2021年   48篇
  2020年   67篇
  2019年   60篇
  2018年   38篇
  2017年   57篇
  2016年   84篇
  2015年   74篇
  2014年   88篇
  2013年   159篇
  2012年   181篇
  2011年   169篇
  2010年   111篇
  2009年   150篇
  2008年   84篇
  2007年   125篇
  2006年   121篇
  2005年   101篇
  2004年   94篇
  2003年   102篇
  2002年   106篇
  2001年   70篇
  2000年   71篇
  1999年   55篇
  1998年   46篇
  1997年   57篇
  1996年   33篇
  1995年   32篇
  1994年   8篇
  1993年   7篇
  1992年   5篇
  1990年   1篇
  1988年   1篇
  1987年   3篇
  1986年   3篇
  1985年   1篇
  1984年   1篇
  1981年   1篇
  1979年   3篇
  1970年   1篇
排序方式: 共有2460条查询结果,搜索用时 187 毫秒
521.
以石油酸为主要原料的重油乳化剂的研制   总被引:1,自引:0,他引:1  
采用石油酸与三乙醇胺,非离子型表面活性剂复配制备了一种廉价的重油乳化剂,最佳配方为石油酸500mg,三乙醇胺25mg,非离子表面活性剂2为25mg,乳化助剂H20mg,pH11(共占乳化油总质量的0.57%),可使油水质量比为70:30的油包水型乳化重油在80℃下稳定36h,实验过程中采用均匀设计与调优软件进行实验方案的设计和实验结果的优化,考察了乳化剂中石油酸与三乙醇胺和非离子表面活性剂量的协同作用以及PH的影响。结果表明,组分间交互作用明显,在不同的配方下,组分的作用会有很大变化,有时甚至会是相反的。  相似文献   
522.
废塑料裂解生产原料油的研究   总被引:1,自引:0,他引:1  
本文对聚乙烯和聚丙烯的混合物裂解成原料油进行了研究 ,在 44 0℃条件下 ,不同比例的聚乙烯和聚丙烯被裂解。结果发现 ,聚丙烯有最高的液体回收率。几种催化剂被应用到聚丙烯的裂解过程中。裂解产品组分的构成及催化剂的选择是本研究的主要内容。通过比较几种不同催化剂的催化结果发现 ,复合催化剂有更好的催化效果。本研究为将来的废塑料综合利用提供了一种新的有用方法  相似文献   
523.
The leakage of fluid leaving a puncture in a pressurized vessel immersed in a quiescent, miscible medium is studied under steady flow conditions. This problem has engineering applications in submerged pipelines and hazardous gas lines. The leakage rate for the puncture is characterized as functions of various hydrodynamic and geometric conditions. Dimensional analysis shows that the leakage percent, Q*, is a function of the Reynolds number, the pressure ratio between the center of the tube and the external hydrostatic pressure, P*, and the hole-to-main tube diameter ratio, D*. The effect of puncture shape is also examined, rectangular and circular. A 3-D finite volume computational model is constructed for laminar flow of a Newtonian fluid under steady conditions and validated with supporting experiments. The results show that the fractional leakage rate Q* increases with P* and approaches a constant value at high P* for a fixed Reynolds number. In addition, it is found that the leakage rate increases with decreasing Reynolds number at a fixed pressure ratio. The geometric effect of the diameter ratio is shown to have a more pronounced effect near a pressure ratio of two with more fluid exiting the puncture for larger diameter ratios. The results of the shape analysis show that the circular puncture has the largest fractional leakage when compared to a rectangle with an equivalent cross-sectional area.  相似文献   
524.
Oil spill contingency plans are available for most coastlines but the amount of useful environmental data is variable. The information should be held on a GIS base. High risk areas should be identified and the pre-existing store of environmental knowledge should be commensurately extensive and should be available in considerable spatial detail. Contingency plans still depend on basic lists of coastal types as defined by static, sediment based shoreline characteristics. There is a lack of dynamic, process information. TheBraer oil spill of 1993 provides a case study of the application of sound coastal geomorphological and ecological data to impact assessment. Monitoring of the ecological effects of this massive oil spill reinforces other research which indicates that most coastlines can recover naturally from oil spills, and that oil spill clean up techniques may not necessarily benefit rapid shoreline recovery. Although pre-existing environmental informations is important, the key decisions must be taken quickly and are frequently judgmental and, therefore, place a premium on gathering appropriate scientific expertise to the site of the spill as soon as possible and with sufficient powers to affect both the oil spill response, to initiate early surveys of damage and to facilitate the initial monitoring programme.  相似文献   
525.
应用假单胞菌进行防蜡作用的研究   总被引:1,自引:0,他引:1  
假单胞菌L-11菌体与其胞外产物可以作为一种很好的防蜡剂,对L-11的发酵条件进行了优化,确定了最适发酵培养基的配方,发酵培养基以葡萄糖、蛋白胨为其最适碳、氮源,防蜡剂生产的发酵条件为:前16h的发酵温度为35℃,后期将温度降至20℃,发酵液的pH=4.5为发酵终点,此时发酵液在内条件下的防蜡率为78%,将上述所得菌液在大庆油田做了防蜡实验,结果表明,注入L-11的油井洗井周期有所延长,实验证明了L-11的发酵液可以作为一种经济、有效的蜡剂。  相似文献   
526.
二硫代氨基甲酸盐型除油剂的性能研究   总被引:3,自引:0,他引:3  
葛际江  赵福麟  冷强 《环境化学》2002,21(2):162-166
分别用二乙胺、乙二胺、三乙烯四胺与CS2 反应 ,合成了三种二硫代氨基甲酸盐 ,试验了其除油性能 .结果表明 ,三 ( 1 ,2 亚乙基 )四氨基四 (二硫代甲酸钠 )对含有一定量Fe2 + 的油田污水有较好的除油效果 .每升污水中加入 1 0mg除油剂 ,就能在1 5min内将污水中的油含量降至 1 0mg·l- 1.通过改变二硫代氨基甲酸盐的浓度、污水中Fe2 + 的浓度、搅拌速度、氨基的结构 ,发现多官能团的二硫代氨基甲酸盐 ,在较低的搅拌速度下 ,除油效果较好 .  相似文献   
527.
Summary. Many species of insects sabotage the pressurized defense vessels of their host plants prior to feeding. This behavior, however, does not render leaves indefinitely suitable, as some species employing this behavior eventually abandon uneaten portions of sabotaged leaves. In this study, we examined whether and to what degree wild parsnip, Pastinaca sativa, is capable of restoring its pressurized defenses and whether cabbage loopers, Trichoplusa ni, which normally trench parsnip leaflets, benefit from their trenching behavior. The pressurized oil tubes of parsnip leaves are rich in toxic terpenoids and furanocoumarins. A disruption of the integrity of the tubes (via razor blade nicks) in leaflets revealed that that some of their contents were expelled at the break and that some movement of oil from outside the leaflet (i.e., the midvein) occurred, bolstering furanocoumarin levels in the leaflet within minutes. Pressure and chemical content in a leaflet’s oil tubes were also shown to be restored within 24 hours of depressurization. This recovery ability allowed parsnip leaflets to respond to daily depressurizations by mechanical damage for up to at least 5 assaults, cumulatively causing an approximate ten-fold increase in furanocoumarins. Cabbage loopers fed parsnip leaflets that were artificially trenched accumulated twice as much body mass as larvae fed leaflets augmented with furanocoumarins equivalent to the quantity that would be avoided through trenching, indicating that trenching does benefit the herbivore. Although parsnip recovers from trenching rapidly, it does not do so within the time that cabbage loopers consume trenched leaflets  相似文献   
528.
表面活性剂对柴油在土壤中吸附的影响   总被引:2,自引:0,他引:2  
张景环  曾溅辉 《环境化学》2007,26(5):610-613
通过静态吸附实验,研究土壤对十二烷基苯磺酸钠(LAS)和十六烷基三甲基溴化铵(CTAB)的吸附行为,探讨表面活性剂对柴油吸附的影响.结果表明,土壤对LAS和CTAB的吸附等温线均为非线性,其吸附能力的大小顺序为:轻壤土>轻粘土>中壤土>砂壤土>重壤土>紧砂土.同一土壤中,CTAB的吸附量大于LAS的吸附量.LAS和CTAB均利于柴油在土壤表面的解吸,且LAS的解吸效果更好.柴油的吸附量随LAS浓度的升高而降低.当CTAB的浓度小于临界胶束浓度CMC时,吸附量随CTAB浓度的升高而升高,当CTAB的浓度等于或大于临界胶束浓度(CMC)时,吸附量随CTAB浓度的升高而降低.  相似文献   
529.
泥炭净化含油污水的技术和方法   总被引:3,自引:0,他引:3  
泥炭比重小,重量轻,富含有机质,是一种吸附能力很强的吸油。本文通过大量试验论述了泥炭净化含油污水的实验条件和方法。结果表明,泥炭经热加工处理后,由原来的亲水性变成疏水性,在含油污水中实现吸油而不吸水;采用不同的净化方式效果不同,静态方式泥炭可吸附其自身重量的5-10倍的油,动态吸油高达10倍以上。藓类泥炭,草本泥炭及木本泥炭对油的吸附效果不同,分别可吸附油6L/kg-9.5L/kg,4L/kg-8  相似文献   
530.
Impacts of Roads and Hunting on Central African Rainforest Mammals   总被引:7,自引:0,他引:7  
Abstract:  Road expansion and associated increases in hunting pressure are a rapidly growing threat to African tropical wildlife. In the rainforests of southern Gabon, we compared abundances of larger (>1 kg) mammal species at varying distances from forest roads and between hunted and unhunted treatments (comparing a 130-km2 oil concession that was almost entirely protected from hunting with nearby areas outside the concession that had moderate hunting pressure). At each of 12 study sites that were evenly divided between hunted and unhunted areas, we established standardized 1-km transects at five distances (50, 300, 600, 900, and 1200 m) from an unpaved road, and then repeatedly surveyed mammals during the 2004 dry and wet seasons. Hunting had the greatest impact on duikers ( Cephalophus spp. ), forest buffalo ( Syncerus caffer nanus ), and red river hogs ( Potamochoerus porcus ), which declined in abundance outside the oil concession, and lesser effects on lowland gorillas ( Gorilla gorilla gorilla ) and carnivores. Roads depressed abundances of duikers, sitatungas ( Tragelaphus spekei gratus ), and forest elephants ( Loxondonta africana cyclotis ), with avoidance of roads being stronger outside than inside the concession. Five monkey species showed little response to roads or hunting, whereas some rodents and pangolins increased in abundance outside the concession, possibly in response to greater forest disturbance. Our findings suggest that even moderate hunting pressure can markedly alter the structure of mammal communities in central Africa. Roads had the greatest impacts on large and small ungulates, with the magnitude of road avoidance increasing with local hunting pressure.  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