全文获取类型
收费全文 | 93901篇 |
免费 | 1227篇 |
国内免费 | 1101篇 |
专业分类
安全科学 | 3844篇 |
废物处理 | 3506篇 |
环保管理 | 14377篇 |
综合类 | 21117篇 |
基础理论 | 26742篇 |
环境理论 | 72篇 |
污染及防治 | 16168篇 |
评价与监测 | 5683篇 |
社会与环境 | 4137篇 |
灾害及防治 | 583篇 |
出版年
2022年 | 820篇 |
2021年 | 828篇 |
2020年 | 655篇 |
2019年 | 863篇 |
2018年 | 1224篇 |
2017年 | 1257篇 |
2016年 | 2202篇 |
2015年 | 1836篇 |
2014年 | 2564篇 |
2013年 | 9206篇 |
2012年 | 2366篇 |
2011年 | 2813篇 |
2010年 | 3350篇 |
2009年 | 3497篇 |
2008年 | 2422篇 |
2007年 | 2218篇 |
2006年 | 2537篇 |
2005年 | 2496篇 |
2004年 | 2771篇 |
2003年 | 2611篇 |
2002年 | 2163篇 |
2001年 | 2449篇 |
2000年 | 2041篇 |
1999年 | 1554篇 |
1998年 | 1376篇 |
1997年 | 1370篇 |
1996年 | 1504篇 |
1995年 | 1606篇 |
1994年 | 1486篇 |
1993年 | 1338篇 |
1992年 | 1336篇 |
1991年 | 1310篇 |
1990年 | 1253篇 |
1989年 | 1220篇 |
1988年 | 1065篇 |
1987年 | 1000篇 |
1986年 | 998篇 |
1985年 | 1066篇 |
1984年 | 1163篇 |
1983年 | 1170篇 |
1982年 | 1176篇 |
1981年 | 1099篇 |
1980年 | 938篇 |
1979年 | 935篇 |
1978年 | 830篇 |
1977年 | 721篇 |
1976年 | 639篇 |
1975年 | 610篇 |
1973年 | 652篇 |
1972年 | 648篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
271.
272.
C. K. Jørgensen 《Die Naturwissenschaften》1980,67(4):188-189
273.
Distribution of actinomycetes in oil contaminated ultisols of the Niger Delta (Nigeria) 总被引:1,自引:0,他引:1
J.P.Essien 《环境科学学报》2000,12(3):296-302
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
274.
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
275.
276.
277.
The Science of Nature - 相似文献
278.
The importance of selenium as an essential trace element has progressively emerged during the last years due to the analysis of selenium deficiency diseases and to the identification and characterization of a number of selenoenzymes. Selenium is incorporated in the catalytic site of the enzymes as an integral selenocysteine residue. The pathway of selenocysteine biosynthesis and incorporation has been elucidated recently for Escherichia coli. This article presents an overview on these subjects and describes the mechanisms which confer selenocysteine specificity in the framework of protein biosynthesis. In addition, some considerations concerning the phylogeny of selenocysteine incorporation are presented and a model for the evolution of the selenocysteine pathway is proposed. 相似文献
279.
The Science of Nature - 相似文献
280.
Land use as a mitigation strategy for the water-quality impacts of global warming: a scenario analysis on two watersheds in the Ohio River Basin 总被引:4,自引:0,他引:4
This study uses an integrative approach to study the water-quality impacts of future global climate and land-use changes. In this study, changing land-use types was used as a mitigation strategy to reduce the adverse impacts of global climate change on water resources. The climate scenarios were based on projections made by the Intergovernmental Panel on Climate Change (IPCC) and the United Kingdom Hadley Centre's climate model (HadCM2). The Thornthwaite water-balance model was coupled with a land-use model (L-THIA) to investigate the hydrologic effects of future climate and land-use changes in the Ohio River Basin. The land-use model is based on the Soil Conservation Service's curve-number method. It uses the curve number, an index of land use and soil type, to calculate runoff volume and depth. The ArcView programming language, Avenue, was used to integrate the two models into a geographic information system (GIS). An output of the water-balance model, daily precipitation values adjusted for potential evapotranspiration, served as one of the inputs into the land-use model. Two watersheds were used in the present study: one containing the city of Cincinnati on the main stem of the Ohio River, and one containing the city of Columbus on a tributary of the Ohio River. These cities represent two major metropolitan areas in the Ohio River Basin with different land uses experiencing different rates of population growth. The projected hypothetical land-use changes were based on linear extrapolations of current population data. Results of the analyses indicate that conversion from agricultural land use to low-density residential land use may decrease the amount of surface runoff. The land-use practices which generate the least amount of runoff are forest, low-density residential, and agriculture; whereas high-density residential and commercial land-use types produce the highest runoff. The hydrologic soil type present was also an important factor in determining the amount of runoff and non-point-source pollution. A runoff-depth matrix and total nitrogen matrix were created for Cincinnati and Columbus to describe possible land-use mitigation measures in response to global climate change. The differences in Cincinnati and Columbus were due to differences in geographic location, air temperature, and total runoff. The results of this study may be useful to planners and policy makers for defining the possible impacts of future global climate and land-use changes on water resources. 相似文献