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   43420篇
  免费   390篇
  国内免费   487篇
安全科学   1070篇
废物处理   2334篇
环保管理   5102篇
综合类   6643篇
基础理论   11698篇
环境理论   24篇
污染及防治   11067篇
评价与监测   3326篇
社会与环境   2837篇
灾害及防治   196篇
  2023年   195篇
  2022年   472篇
  2021年   466篇
  2020年   311篇
  2019年   376篇
  2018年   1923篇
  2017年   1876篇
  2016年   2012篇
  2015年   848篇
  2014年   1170篇
  2013年   2807篇
  2012年   1755篇
  2011年   2900篇
  2010年   1992篇
  2009年   1863篇
  2008年   2440篇
  2007年   2762篇
  2006年   1474篇
  2005年   1282篇
  2004年   1188篇
  2003年   1258篇
  2002年   1137篇
  2001年   1312篇
  2000年   898篇
  1999年   554篇
  1998年   372篇
  1997年   379篇
  1996年   371篇
  1995年   447篇
  1994年   467篇
  1993年   364篇
  1992年   391篇
  1991年   368篇
  1990年   399篇
  1989年   353篇
  1988年   306篇
  1987年   283篇
  1986年   238篇
  1985年   260篇
  1984年   286篇
  1983年   271篇
  1982年   254篇
  1981年   227篇
  1980年   183篇
  1979年   199篇
  1978年   181篇
  1976年   123篇
  1975年   144篇
  1972年   138篇
  1971年   133篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
271.
One method for recovering degraded soils in semiarid regions is to add organic matter to improve soil characteristics, thereby enhancing biogeochemical nutrient cycling. In this paper, we studied the changes in soil biological properties as a result of adding a crushed cotton gin compost (CCGC) and a poultry manure (PM) for 4 yr to restore a Xerollic Calciorthid located near Seville (Guadalquivir Valley, Andalusia, Spain). Organic wastes were applied at rates of 5, 7.5, and 10 Mg organic matter ha(-1). One year after the assay began, spontaneous vegetation had appeared in the treated plots, particularly in that receiving a high PM and CCGC dose. After 4 yr, the plant cover in these treated plots was around 88 and 79%, respectively, compared with 5% for the control. The effects on soil microbial biomass and six soil enzymatic activities (dehydrogenase, urease, BBA-protease, beta-glucosidase, arylsulfatase, and alkaline phosphatase activities) were ascertained. Both added organic wastes had a positive effect on the biological properties of the soil, although at the end of the experimental period and at high dosage, soil microbial biomass and soil enzyme activities were generally higher in the PM-amended soils compared to the CCGC-amended soils. Enzyme activity from the PM-amended soil was 5, 15, 13, 19, 22, 30, and 6% greater than CCGC-amended soil for soil microbial biomass, urease, BBA-protease, beta-glucosidase, alkaline phosphatase, arylsulfatase, and dehydrogenase activities, respectively. After 4 yr, the percentage of plant cover was > 48% in all treated plots and 5% in the control.  相似文献   
272.
Environmental Science and Pollution Research - Aedes aegypti and Culex quinquefasciatus are vectors of diseases that constitute public health problems. The discovery of products capable of...  相似文献   
273.
Russian Journal of Ecology - It has been shown that the main drivers of the dynamics of cladoceran and copepod abundances can be predators (fish), the quantity and/or quality of food in terms of...  相似文献   
274.
Russian Journal of Ecology - Abstract—The study of the effect of mycorrhiza symbiosis on the transformation of carbon and nitrogen compounds in soils is important in view of the necessity to...  相似文献   
275.
Environmental Science and Pollution Research - The rice husk ash (RHA) was used as an alternative source of silica for the synthesis of the functionalized mesoporous material, which was used in the...  相似文献   
276.
Environmental Science and Pollution Research - In this work, it was analyzed the behavior of three commercial activated carbons with different textural and chemical properties to adsorb...  相似文献   
277.

The aim of this study was to determine the bioavailability of metals in field soils contaminated with chromated copper arsenate (CCA) mixtures. The uptake and elimination kinetics of chromium, copper, and arsenic were assessed in the earthworm Eisenia andrei exposed to soils from a gradient of CCA wood preservative contamination near Hartola, Finland. In soils contaminated with 1480–1590 mg Cr/kg dry soil, 642–791 mg Cu/kg dry soil, and 850–2810 mg Ag/kg dry soil, uptake and elimination kinetics patterns were similar for Cr and Cu. Both metals were rapidly taken up and rapidly excreted by Eisenia andrei with equilibrium reached within 1 day. The metalloid As, however, showed very slow uptake and elimination in the earthworms and body concentrations did not reach equilibrium within 21 days. Bioaccumulation factors (BAF) were low for Cu and Cr (< 0.1), but high for As at 0.54–1.8. The potential risk of CCA exposure for the terrestrial ecosystem therefore is mainly due to As.

  相似文献   
278.
Methods for integrated assessment   总被引:4,自引:1,他引:4  
Integrated assessment is an approach that seeks to involve all disciplines in policy-relevant assessment. The process aims to encompass environmental science, technology and policy problems. The aim is to establish an overview of the environmental issue in question that attempts to avoid the mistakes of the past associated with narrow, one-sided or unidimensional approaches. A number of methods are available for such assessments. However, they are also subject to a number of limitations, difficulties and dilemmas. Integrated methods are inherently complicated and the tradition is that only experts are involved. New more inclusionary procedures have to be devised in order to involve all stakeholders. They have to be involved in the framing of the issue and in the value judgements associated with the approach. The dilemmas cannot be solved by integrated approaches, but they can be mitigated via proper identification, analysis and evaluation of the gains and losses involved. In structuring the analysis the existence of ignorance has to be accounted for and communicated to the managers and the political decision makers. The ignorance/uncertainty aspects can be partially accommodated for via an intensification of feasible monitoring and research so as to minimise the risks of unpleasant surprises. Electronic Publication  相似文献   
279.
280.
Wood-pastures are associated with high cultural and biodiversity values in Europe. However, due to their relatively low productivity, large areas of wood-pastures have been lost over the last century. In some areas, incentive schemes have been developed to revive wood-pastures. We investigated the effects of one such scheme in western Estonia. We compared the structure of grazed wood-pastures (old and restored) to those of abandoned wood-pastures and ungrazed forest stands to explore the effects of management, and conducted interviews with 24 farmers to investigate their motivations to carry out the management. We found a positive influence of active management on the semi-open structure of wood-pastures. Financial support was vital for management, but personal values related to tradition also played an important role. The interviewees differed widely in their range of motivations, suggesting that other strategies in addition to financial incentives would further improve the management of wood-pastures in the region.

Electronic supplementary material

The online version of this article (doi:10.1007/s13280-015-0719-8) contains supplementary material, which is available to authorized users.  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