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   41868篇
  免费   359篇
  国内免费   241篇
安全科学   884篇
废物处理   2071篇
环保管理   5596篇
综合类   6262篇
基础理论   11972篇
环境理论   14篇
污染及防治   10106篇
评价与监测   2968篇
社会与环境   2370篇
灾害及防治   225篇
  2022年   218篇
  2021年   242篇
  2019年   250篇
  2018年   1789篇
  2017年   1689篇
  2016年   1776篇
  2015年   601篇
  2014年   756篇
  2013年   2586篇
  2012年   1331篇
  2011年   2485篇
  2010年   1711篇
  2009年   1568篇
  2008年   2130篇
  2007年   2469篇
  2006年   1286篇
  2005年   1074篇
  2004年   1117篇
  2003年   1083篇
  2002年   1070篇
  2001年   1291篇
  2000年   920篇
  1999年   551篇
  1998年   447篇
  1997年   437篇
  1996年   452篇
  1995年   519篇
  1994年   512篇
  1993年   447篇
  1992年   464篇
  1991年   443篇
  1990年   482篇
  1989年   461篇
  1988年   403篇
  1987年   375篇
  1986年   338篇
  1985年   329篇
  1984年   410篇
  1983年   363篇
  1982年   403篇
  1981年   361篇
  1980年   294篇
  1979年   324篇
  1978年   281篇
  1977年   233篇
  1975年   230篇
  1974年   250篇
  1973年   239篇
  1972年   247篇
  1971年   214篇
排序方式: 共有10000条查询结果,搜索用时 241 毫秒
281.
2000年4月期间坦桑尼亚霞水母章鱼(1849)个体渔业的初步结果到2001年6月才被提供.对在坦噶、马菲亚岛和姆特瓦拉三地的2546个单个渔获物和15 473个样品进行了分析.  相似文献   
282.
283.
Becker  E. W.  Bier  W.  Ehrfeld  W.  Schubert  K.  Schütte  R.  Seidel  D. 《Die Naturwissenschaften》1976,63(9):407-411
The Science of Nature - The development of reliable manufacturing methods for commercial separation elements, the successful operation of separative stages, and extensive tests performed on plant...  相似文献   
284.
The distribution of actinomycetes in oil contaminated sandy loam ultisols of the Niger Delta region of Nigeria was studied to aid in understanding the effect of hydrocarbons on indigenous microbial population in tropical soils. The average total counts of actinomycetes in all the oil samples analysed was 103 cfu/g. Higher counts of actinomycetes were observed during the dry season than during the wet season. The counts of hydrocarbonoclastic actinomycetes correlated positively with the total count of actinomycetes.The actinomycetes were generally restricted to the top soil(0-10 cm soil depth) although a seemingly deeper(down to 40 cm soil depth) distribution was noticed in the dry season. The isolates included oil degrading species of Actinoplanes, Norcadia,Streptomyces and Streptosporangium. Their high oil utilization ability indicates their positive potential and role in the bioremediation of oil-spilled soils.  相似文献   
285.
Supplementing the nutrient requirement of crops through organic manures plays a key role in sustaining soil fertility, and crop productivity and reducing use of fossil fuels. Field experiments were conducted for 2 years at two different locations (i.e. Lucknow and Pantnagar) in Uttar Pradesh, India. The objectives of the study were to assess the herb and essential oil yields of Japanese mint (Mentha arvensis cv. Hy 77), and its nutrient accumulation under single and combined applications of organic manures and inorganic fertilizers (NPK). Changes in physical and chemical characteristics of the soils (Fluvisols, Mollisols) were also determined. Eight treatments comprising different combinations of NPK through inorganic fertilizers and farm yard manure (FYM) were compared. The distilled waste of mint after extraction of essential oil was recycled to soils in the plots to supplement the nutritional requirement of the succeeding mustard crop (Brassica juncea cv. Pusa Bold). Herb and essential oil yield of mint were significantly higher with combined application of organic and inorganic sources of nutrients as compared to single applications. Accumulation of N and P was at par under full inorganic and combined supply whereas, K accumulation was higher with the former. Soil organic C and pH after harvest of mint did not significantly differ among the treatments, but the level of mineralizable N, Olsen-P and NH4OAc extractable K were higher in soil with integrated supply of nutrients. Significant increase in soil water stable aggregates, organic C, available NPK and microbial biomass, and decrease in soil bulk density were observed with waste recycling over fertilizer application. These benefits were reflected in the seed and stubble yield of mustard which succeeded mint. This study indicates that combined application of inorganic fertilizers with organics helps in increasing the availability of nutrients and crop yield and provides a significant effect to the succeeding crop. Similarly, recycling crop residues reduces the need for fossil fuel based fertilizer, and helps in sustaining and restoring soil fertility in terms of available nutrients and major physical and chemical characteristics of the soil.  相似文献   
286.
287.
288.
289.
290.
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