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   16118篇
  免费   72篇
  国内免费   55篇
安全科学   255篇
废物处理   804篇
环保管理   1693篇
综合类   2206篇
基础理论   4490篇
环境理论   4篇
污染及防治   3388篇
评价与监测   1266篇
社会与环境   2083篇
灾害及防治   56篇
  2023年   62篇
  2022年   136篇
  2021年   129篇
  2020年   63篇
  2019年   91篇
  2018年   681篇
  2017年   669篇
  2016年   674篇
  2015年   223篇
  2014年   347篇
  2013年   905篇
  2012年   556篇
  2011年   1182篇
  2010年   779篇
  2009年   866篇
  2008年   1087篇
  2007年   1316篇
  2006年   487篇
  2005年   479篇
  2004年   443篇
  2003年   498篇
  2002年   486篇
  2001年   482篇
  2000年   342篇
  1999年   188篇
  1998年   126篇
  1997年   130篇
  1996年   112篇
  1995年   133篇
  1994年   128篇
  1993年   112篇
  1992年   111篇
  1991年   116篇
  1990年   131篇
  1989年   104篇
  1988年   93篇
  1987年   90篇
  1986年   96篇
  1985年   86篇
  1984年   107篇
  1983年   83篇
  1982年   91篇
  1981年   58篇
  1980年   73篇
  1979年   75篇
  1978年   55篇
  1977年   56篇
  1974年   61篇
  1973年   60篇
  1972年   66篇
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
991.
992.
993.
Development of new economically feasible ecofriendly products from agricultural wastes or byproducts for shrimp farm wastewater treatment is the objective of our continued research. Ammonia is a nitrogenous toxicant, which is commonly found in wastewater from shrimp farms. In the present study, we explored the possibility of the use of simply and inexpensively prepared bagasse products so that this abundant crop byproduct could be used to remove ammonia from shrimp farm wastewater. Bagasse, a natural highly fibrous lignocellulosic byproduct of sugarcane, was converted into five different products. Experimental results have shown that ammonia is efficiently removed from wastewater by four bagasse products with a dose of 1 to 6 g/L within 24 hours. The effect of bagasse products on other water quality parameters and growth kinetics of biofilm bacteria onto bagasse fiber have also been studied. Efficacies of products were compared by using statistical analysis. Products developed from bagasse are useful and economical.  相似文献   
994.
Lists of macrolepidopterans inhabiting the Southern, Middle, and Polar Urals have been used for analyzing the relationship between the species richness of these insects with that of the families of plants on which their larvae feed. The results have shown that this factor in the Southern Urals accounts for approximately 75% and 65% of variation in the species richness of lepidopterans on woody and herbaceous plants, respectively. In the Polar Urals, this correlation is markedly weaker. Latitudinal trends in trophic preferences of individual lepidopteran taxa have been revealed. Probable causes of changes in the relative abundance of lepidopterans north of the forest zone are discussed.  相似文献   
995.
New principles of the assessment of soil cover degradation and desertification, the scale and intensity of destructive processes manifestation are determined.  相似文献   
996.
The effects of the aeration, seeding, and agitation on the composting of vegetable waste were studied in a laboratory-scale reactor. Experimental results showed that the final product at the end of a 4-day composting period met multiple maturity indices suggested by many researchers. The evolution of carbon dioxide during the composting process could be modelled with a modified Gompertz equation that described the bacteria growth successfully. Multivariate regression analysis was used to study the effects of operating parameters on the carbon conversion. The response surface contour plots were constructed using the regression equation for the examination of the dependence of carbon conversion on operating parameters. The maximum carbon conversion of 14.54% was obtained when the percentage of seeding was set at 14.5%, the air suction rate was set at 2.6 L kg(-1) dry-solid min(-1), and the agitator operated half of the time, alternating on and off for every 5 min. Future work will focus on the application of the data and the experience gained in this work to composters of pilot and semi-commercial scales.  相似文献   
997.
998.
999.
1000.
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