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   874篇
  免费   20篇
  国内免费   65篇
安全科学   15篇
废物处理   6篇
环保管理   291篇
综合类   248篇
基础理论   168篇
污染及防治   26篇
评价与监测   26篇
社会与环境   144篇
灾害及防治   35篇
  2024年   2篇
  2023年   12篇
  2022年   10篇
  2021年   10篇
  2020年   10篇
  2019年   16篇
  2018年   17篇
  2017年   18篇
  2016年   26篇
  2015年   25篇
  2014年   28篇
  2013年   68篇
  2012年   31篇
  2011年   46篇
  2010年   36篇
  2009年   31篇
  2008年   22篇
  2007年   47篇
  2006年   39篇
  2005年   40篇
  2004年   41篇
  2003年   47篇
  2002年   32篇
  2001年   45篇
  2000年   42篇
  1999年   40篇
  1998年   22篇
  1997年   30篇
  1996年   28篇
  1995年   21篇
  1994年   12篇
  1993年   15篇
  1992年   11篇
  1991年   9篇
  1990年   5篇
  1989年   2篇
  1988年   6篇
  1987年   1篇
  1985年   2篇
  1984年   1篇
  1983年   1篇
  1982年   1篇
  1980年   4篇
  1979年   1篇
  1978年   2篇
  1976年   1篇
  1974年   1篇
  1972年   1篇
  1971年   1篇
排序方式: 共有959条查询结果,搜索用时 265 毫秒
391.
论述了当今世界水资源危机的现状,引起水资源危机的主要原因;认为发展节水农业是缓解水资源危机的重要举措,并概述了节水农业的技术现状和节水农业今后的发展趋势.  相似文献   
392.
本文以广东省赤红壤水土流失区为例,综合分析了赤红壤水土流失区发展持续农业的存在问题,在此基础上提出了该区发展持续农业的途径与对策.认为:水土流失区发展持续农业存在的突出问题主要是土壤退化;发展持续农业的根本途径在于走生态农业的道路,建立立体农业生态系统;侵蚀土壤上重建森林植被群落首先要建立先锋群落,然后建立稳定的南亚热带森林植被群落。  相似文献   
393.
阐述了在农业开发中实施战略环境评价(strategicenvironmentalassessment,SEA)的必要性。根据农业开发SEA的介入时机,将其划分为预测性SEA、监控性SEA和回顾性SEA3种类型。初步探讨了农业开发SEA的基本内容,即评价对象、评价原则、评价指标体系集和评价方法,并提出了农业开发SEA的基本工作程序。  相似文献   
394.
本文以西北地区五个生态农业试点县为例,通过对这一地区的生态环境、社会经济基本情况与特点及生态农业建设情况的研究,探讨了在这一地区发展生态农业的模式与前景。  相似文献   
395.
Agricultural adaptation to climate change in China   总被引:4,自引:0,他引:4  
IntroductionAdaptationreferstoeffortstoreducesystem’svulnerabilitiestoclimate.Amongthemostfrequentlycitedhumansystemslikelytobeaffectedbyclimaticchangeisagriculture.Itisespeciallysensitivetotheconsequencesofglobalwarmingasitreliesheavilyontheweatheran…  相似文献   
396.
根据多年的生产实践经验和定位试验结果,提出了江苏省沿江高沙土地区多熟种植制、合理轮耕制、用养结合的培肥制和高产高效的栽培制相结合的种植业可持续发展的一体化技术体系,研究结果对我国中低产土壤地区种植业的持续发展具有重要意义。  相似文献   
397.
The temporal changes and spatial variability of phosphorus andnitrogen losses and concentrations in Finland during the period1981–1997 were studied in 15 small agricultural and forestedcatchments. In addition, four coastal river basins with highagricultural land use located in southern Finland were includedin the study in order to assess the representativeness ofagricultural loss estimates from small agricultural catchments.The mean annual loss specific for agricultural land was estimatedto be on average 110 kg km-2 a-1 for total phosphorusand 1500 kg km-2 a-1 for total nitrogen. The resultsfrom small agricultural catchments were in agreement with thecorresponding loss estimates from rivers, with an average of137 kg km-2 a-1 for total phosphorus and 1800 kg km-2a-1 for total nitrogen. The results from the studiedagricultural catchments and rivers during the period 1981–1997suggest that weather-driven fluctuation in discharge was usuallythe main reason for changes in nutrient losses, and little or noimpact of changes in agricultural production or managementpractises can be observed. In forested areas the total phosphorusloss (average 9 kg km-2 a-1) and total nitrogen loss(average 250 kg km-2 a-1) were lower than inagricultural areas. In forested catchments the impact of forestryoperations, such as clear-cutting and fertilization, and theimpact of atmospheric nitrogen deposition can be seen in changesin nutrient losses.  相似文献   
398.
The advantage of using insurance to help a farmer adopt a best nitrogen management plan (BNMP) that reduces the impact of agricultural production on the environment is analytically and empirically demonstrated. Using an expected value analysis, it is shown that an insurance program can be structured soas to reduce a farmer's cost of bearing the adoption risk associated with changing production practices and, thus, to improve the farmer's certainty equivalent net return thereby promoting the adoption of a BNMP. Using the adoption of growing-season only N fertilizer application in Iowa as a case study, it is illustrated how insurance may be used to promote the adoption of this practice to reduce N fertilizeruse. It is shown that it is possible for a farmer and an insurance company both to have an incentive to develop an insurance adoption program that will benefit both the farmer and the insurance company, increasing net social welfare and improving environmental quality in Iowa.  相似文献   
399.
The Salinas River watershed along the central coast of California, U.S.A., supports rapidly growing urban areas and intensive agricultural operations. The river drains to an estuarine National Wildlife Refuge and a National Marine Sanctuary. The occurrence, spatial patterns, sources and causesof aquatic toxicity in the watershed were investigated by sampling four sites in the main river and four sites in representative tributaries during 15 surveys between September1998 and January 2000. In 96 hr toxicity tests, significant Ceriodaphnia dubia mortality was observed in 11% of the mainriver samples, 87% of the samples from a channel draining anurban/agricultural watershed, 13% of the samples fromchannels conveying agricultural tile drain runoff, and in 100% of the samples from a channel conveying agricultural surface furrow runoff. In six of nine toxicity identificationevaluations (TIEs), the organophosphate pesticides diazinon and/or chlorpyrifos were implicated as causes of observed toxicity, and these compounds were the most probable causes oftoxicity in two of the other three TIEs. Every sample collectedin the watershed that exhibited greater than 50% C. dubia mortality (n = 31) had sufficient diazinon and/or chlorpyrifos concentrations to account for the observed effects.Results are interpreted with respect to potential effects on other ecologically important species.  相似文献   
400.
El Niño‐Southern Oscillation (ENSO), which occurs in the Equatorial Pacific Ocean, has been identified to have significant influence on rainfall variability throughout the world, especially in the tropics. Such variability in rainfall has implications for agrarian economies, such as that in Ghana. This study therefore sought to demonstrate the effect of ENSO‐induced variability in annual and seasonal rainfall on the development of sustainable agriculture in the Ho Municipality of Ghana. Using 61 years of monthly rainfall data (1955–2015) for the Ho Municipality and ENSO indices, this study showed that 15% of the variability in total annual rainfall is explained by the ENSO phenomena. Mean annual rainfall and rainfall in the major rainy season decreased for El Niño years, in addition to a more variable rainfall compared to that received in La Niña years. The major growing season was observed to be longer in La Niña years and shorter in El Niño years. This means that the potential for crop cultivation will be severely hampered in an El Niño year. Farmers within the municipality are therefore encouraged to harness other complementary water sources for farming activities and also employ water management strategies during El Niño years.  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