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   11583篇
  免费   86篇
  国内免费   52篇
安全科学   246篇
废物处理   503篇
环保管理   906篇
综合类   1772篇
基础理论   2619篇
环境理论   9篇
污染及防治   3242篇
评价与监测   934篇
社会与环境   1447篇
灾害及防治   43篇
  2023年   78篇
  2022年   192篇
  2021年   226篇
  2020年   110篇
  2019年   138篇
  2018年   297篇
  2017年   326篇
  2016年   429篇
  2015年   281篇
  2014年   485篇
  2013年   928篇
  2012年   527篇
  2011年   608篇
  2010年   445篇
  2009年   455篇
  2008年   626篇
  2007年   631篇
  2006年   501篇
  2005年   436篇
  2004年   409篇
  2003年   367篇
  2002年   328篇
  2001年   323篇
  2000年   237篇
  1999年   130篇
  1998年   91篇
  1997年   94篇
  1996年   83篇
  1995年   115篇
  1994年   96篇
  1993年   67篇
  1992年   77篇
  1991年   79篇
  1990年   90篇
  1989年   69篇
  1988年   58篇
  1987年   48篇
  1986年   71篇
  1985年   59篇
  1984年   63篇
  1983年   49篇
  1982年   66篇
  1981年   45篇
  1980年   57篇
  1979年   53篇
  1978年   36篇
  1975年   39篇
  1973年   37篇
  1972年   47篇
  1969年   37篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
Wastewater treatment works effluent is often considered to be one of the most important point sources of a wide range of anthropogenic contaminants to aquatic systems, however, this paper discusses other potential sources. With the aim of establishing the important sources of UV filters, insect repellent and biocides to the aquatic environment, samples were collected from sites with direct (bathing areas and marinas) and indirect (sites receiving wastewater effluent) human influences. Sunscreens containing UV filters are used in large volumes during the summer months and often applied shortly before a person enters the water for swimming activities. The results presented here demonstrate that washing directly from the skin is an important point source of 4 UV filters to the Oslofjord. The insect repellent, diethyl toluamide, was also measured and it was concluded that washing from the skin was not such an important point source into the fjord. Concentrations of the biocide Irgarol 1051 were also measured and were elevated in the small boat marina and surrounding enclosed area. This work demonstrates that man recreational water-based activities are a diffuse source of some contaminants into coastal and fjord environments and this study provides an initial assessment of the levels being released.  相似文献   
42.
Fraser syndrome (MIM 219000) is a rare disorder of autosomal recessive inheritance, characterized by the association of cryptophthalmos, syndactyly and genital abnormalities. Here we report on two cases of Fraser syndrome (cryptophthalmos syndrome) in a non-consanguineous couple, with variable expression in echographic, clinical and autopsy findings. Furthermore, we highlight the difficulties in prenatal diagnosis of Fraser syndrome. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
43.
This paper describes a closed-chamber method for measuring CO2 fluxes in intertidal soft sediments during periods of emersion. The method relies on closed-circuit incubations of undisturbed sediment and measurement of CO2 exchanges using an infrared gas analyser. The method was assessed during field experiments, both in light and dark conditions, on an exposed sandy beach and in an estuary. The rates of gross community production measured under moderate irradiance (4.2 mg C m-2 h-1 on the exposed sandy beach and 35 mg C m-2 h-1 in the estuary) are in good agreement with rates reported in the literature. In conjunction with appropriate sampling strategies, this method can be useful for estimating and comparing production of intertidal areas or for assessing factors that influence production.  相似文献   
44.
The several established criteria to define a hyperaccumulator plant were applied to a rare and endangered species, Plantago almogravensis, and to the 3rd most abundant element in the earth crust, Al. Using the most common criteria, P. almogravensis undoubtedly is an Al hyperaccumulator plant. If the recent proposed requirements were considered, most of them matching those for a plant to be used in phytoextraction, it can only be considered an unusual accumulator of Al. A discussion is made concerning the several criteria of a hyperaccumulator plant in order to include rare and endemic ones and abundant elements. In ecological terms, the enrichment in Al and Fe observed may account for the differences in the vegetation pattern. Due to the rarity and endangered nature of this plant, the contribution of this work is also relevant for the ecological understanding and the development of conservation options of this endemic species.  相似文献   
45.
46.
Laboratory studies were conducted to evaluate the effects of temperature and water pressure head on the degradation of the diketonitrile metabolite (DKN) of isoxaflutole during 84 d in samples collected in a loamy soil under conventional (CT) and conservation (MT) tillage systems. Soil temperature was the major factor controlling DKN degradation in the two tillage systems. The shortest half-lives (T1/2) were measured in the seedbed samples under MT at 25 °C and −33 cm water pressure head. We found that mouldboard ploughing under CT was responsible for the spatial variability of herbicide degradation properties, whereas under MT herbicide degradation was associated to the vertical distribution of organic matter.  相似文献   
47.
Lobes of the lichen Pseudevernia furfuracea (L.) Zopf and shoots of the moss Hypnum cupressiforme Hedw. were subjected to different treatments (water washing, oven drying, HNO3 washing, NH4-oxalate extraction) to assess the influence of vitality on accumulation efficiency, during a 6-week exposure in bags in two Italian cities, Trieste and Naples. No trend emerged between treatments, in terms of accumulation ability, for major and trace elements. Only water-washed lichens showed an increased C and N content after exposure in both cities. Element concentrations generally reached higher values in mosses than in lichens, especially for Al, Fe, and Zn (both cities), and for Cu, Mg and Na (Naples). Surface development strongly influenced accumulation capacity of the biomonitors. Quartzose and cation exchange filters revealed, on a weight basis, a poor performance. In urban environments, surface interception of atmospheric particulate seems to play a major role in accumulation, irrespective of organism vitality.  相似文献   
48.
Occurrence and fate of 45 pesticides and 40 pesticide degradates were investigated in four contrasting agricultural settings--in Maryland, Nebraska, California, and Washington. Primary crops included corn at all sites, soybeans in Maryland, orchards in California and Washington, and vineyards in Washington. Pesticides and pesticide degradates detected in water samples from all four areas were predominantly from two classes of herbicides--triazines and chloroacetanilides; insecticides and fungicides were not present in the shallow ground water. In most samples, pesticide degradates greatly exceeded the concentrations of parent pesticide. In samples from Nebraska, the parent pesticide atrazine [6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine] was about the same concentration as the degradate, but in samples from Maryland and California atrazine concentrations were substantially smaller than its degradate. Simazine [6-chloro-N,N'-diethyl-1,3,5-triazine-2,4-diamine], the second most detected triazine, was detected in ground water from Maryland, California, and Washington. Metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] rarely was detected without its degradates, and when they were detected in the same sample metolachlor always had smaller concentrations. The Root-Zone Water-Quality Model was used to examine the occurrence and fate of metolachlor at the Maryland site. Simulations accurately predicted which metolachlor degradate would be predominant in the unsaturated zone. In analyses of relations among redox indicators and pesticide variance, apparent age, concentrations of dissolved oxygen, and excess nitrogen gas (from denitrification) were important indicators of the presence and concentration of pesticides in these ground water systems.  相似文献   
49.
Residential, industrial, commercial, institutional and recreational activities discharge degradable and non-degradable wastes that reach the coastal water through rivers and cause coastal pollution. In the present study, mass transport of pollutants by Adyar and Cooum Rivers to the coastal water as a result of land-based discharges was estimated during low tide. The lowest and the highest flow recorded in Adyar varied from 514.59 to 2,585.08×106 litres/day. Similarly, the flow in Cooum River fluctuated between 266.45 and 709.34×106 litres/day. The present study revealed that the Adyar River transported 53.89–454.11 t/d of suspended solids, 0.06–19.64 t/d of ammonia, 15.95–123.24 t/d of nitrate and 0.4–17.86 t/d of phosphate, 0.004–0.09 kg/d of cadmium, 0.15–1.29 kg/d of lead and 3.03–17.58 kg/d of zinc to the coastal water owing to its high discharge. Similarly, the Cooum River transported 11.87–120.06 t/d of suspended solids, 0.08–58.7 t/d of ammonia, 6.11–29.25 t/d of nitrate and 0.66–10.73 t/d of phosphate, 0.003–0.021 kg/d of cadmium, 0.02–0.44 kg/d of lead and 1.36–3.87 kg/d of zinc. A higher concentration of suspended solids was noticed in post monsoon and summer months. An increase in the mass transport of ammonia, nitrate, phosphate in summer months (April and May) and an increase in the mass transport of cadmium, lead and zinc were observed in monsoon months (October–December) in both the rivers. Thus mass transport of pollutants study reveal that Cooum and Adyar Rivers in Chennai contribute to coastal pollution by transporting inorganic and trace metals significantly through land drainage.  相似文献   
50.
固定化混合菌修复油污染地表水的研究   总被引:5,自引:0,他引:5  
从辽河油田受石油污染的河床底泥中筛选出一株芽孢杆菌(Bacillus sp.)和一株黄杆菌(Flavobacterium sp.),采用二次交联化学方法对2株细菌单独及混合固定,分别进行了不同接种量的固定化细菌对油的降解,以及固定化混合菌对环境的耐受性和在自然地表水中对油的降解进行研究,结果表明,在相同时间内固定化混合菌对油的降解效果明显优于固定化单株菌,而且都优于游离菌。固定化混合菌pH在6~10、温度在20~40℃范围内能保持较好的活性。在120 h时,固定化混合菌对自然地表水中油的降解率达94.5%,对地表水中COD的去除率达89.6%。扫描电子显微镜分析显示,固定化载体的微观结构适合细菌的生长,固定化混合菌在载体内部形成高密度的菌群。以上的研究为固定化微生物应用于油污染地表水的生物修复提供了一定的理论基础。  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