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   11330篇
  免费   79篇
  国内免费   83篇
安全科学   283篇
废物处理   500篇
环保管理   1434篇
综合类   2459篇
基础理论   2557篇
环境理论   5篇
污染及防治   2952篇
评价与监测   684篇
社会与环境   563篇
灾害及防治   55篇
  2022年   91篇
  2021年   96篇
  2019年   69篇
  2018年   149篇
  2017年   131篇
  2016年   222篇
  2015年   172篇
  2014年   243篇
  2013年   820篇
  2012年   304篇
  2011年   428篇
  2010年   337篇
  2009年   395篇
  2008年   431篇
  2007年   491篇
  2006年   430篇
  2005年   352篇
  2004年   367篇
  2003年   373篇
  2002年   333篇
  2001年   428篇
  2000年   312篇
  1999年   205篇
  1998年   115篇
  1997年   123篇
  1996年   108篇
  1995年   154篇
  1994年   148篇
  1993年   123篇
  1992年   130篇
  1991年   149篇
  1990年   119篇
  1989年   127篇
  1988年   132篇
  1987年   114篇
  1986年   83篇
  1985年   99篇
  1984年   124篇
  1983年   125篇
  1982年   123篇
  1981年   97篇
  1980年   93篇
  1979年   106篇
  1978年   89篇
  1977年   84篇
  1976年   78篇
  1975年   90篇
  1974年   101篇
  1972年   69篇
  1965年   74篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
We present data indicating that three species of cerambycid beetles (subfamily Cerambycinae) produce the common cerambycine pheromone component (R)-3-hydroxyhexan-2-one as well as an alkan-2-one component, a possible new motif for cerambycid pheromone components. GC/MS analyses of headspace volatiles produced by male beetles indicated that Cyrtophorus verrucosus (Olivier) produced (R)-3-hydroxyhexan-2-one but also nonan-2-one at ~18 % of the hydroxyketone component, whereas Orwellion gibbulum arizonense (Casey) and Parelaphidion aspersum (Haldeman) produced decan-2-one at ~40 and 7 % of the amount of the hydroxyketone, respectively. In field bioassays, adult C. verrucosus were attracted by (R)-3-hydroxyhexan-2-one alone, but attraction was significantly enhanced by nonan-2-one. This effect was lost if the quantity of nonan-2-one exceeded 100 % of the hydroxyketone, suggesting that beetles could discern ratios of the two chemicals and were most strongly attracted to those approximating the blend produced by males. We suggest that nonan-2-one plays a role in the species specificity of the pheromone signal of C. verrucosus, and that decan-2-one plays a similar role in the semiochemical communication of O. g. arizonense and P. aspersum.  相似文献   
982.
Public opinion and siting solid waste landfills in Kuwait   总被引:1,自引:0,他引:1  
Siting municipal solid waste landfills in Kuwait had not considered public concerns about the location of such facilities. Kuwait Municipality has disposed urban waste in abandoned sand quarries for the past 20 years in an unplanned fashion. Due to this improper siting criteria, environmental and health problems have risen from old landfills that are located in residential areas. In an effort to help responsible decision-makers in assessing public support for siting landfills a structured, yet simple, questionnaire was designed and distributed to a random sample of heads of households. Statistical techniques were employed to examine trends and relationships between the sample public responses concerning landfill siting criteria. The findings of the research indicated that a significant percentage of the responding sample did not know about the various landfill impacts and less than 50% were aware of the negative impacts of landfills on the public health and the environment. The visual appearance of the landfill scored the lowest impact in the opinion of the sample public while the most important aspect in siting a landfill appeared to be its economic consideration. The research findings also directed attention to the important role that the media could play in increasing public awareness. Results from the cross-classification analysis demonstrated the existence of differences in awareness levels according to age, nationality, martial status, education, and occupation of the responding sample. Statistically, these differences were significant at the 95% significance level, as supported by the test of the χ-square.  相似文献   
983.
This paper deals with the use of simplified methods to predict methane generation in tropical landfills. Methane recovery data obtained on site as part of a research program being carried out at the Metropolitan Landfill, Salvador, Brazil, is analyzed and used to obtain field methane generation over time. Laboratory data from MSW samples of different ages are presented and discussed; and simplified procedures to estimate the methane generation potential, Lo, and the constant related to the biodegradation rate, k are applied. The first order decay method is used to fit field and laboratory results. It is demonstrated that despite the assumptions and the simplicity of the adopted laboratory procedures, the values Lo and k obtained are very close to those measured in the field, thus making this kind of analysis very attractive for first approach purposes.  相似文献   
984.
The use of organic municipal wastes as soil amendments is an increasing practice that can divert significant amounts of waste from landfill, and provides a potential source of nutrients and organic matter to ameliorate degraded soils. Due to the high heterogeneity of organic municipal waste streams, it is difficult to rapidly and cost-effectively establish their suitability as soil amendments using a single method. Thermal analysis has been proposed as an evolving technique to assess the stability and composition of the organic matter present in these wastes. In this study, three different organic municipal waste streams (i.e., a municipal waste compost (MC), a composted sewage sludge (CS) and a thermally dried sewage sludge (TS)) were characterized using conventional and thermal methods. The conventional methods used to test organic matter stability included laboratory incubation with measurement of respired C, and spectroscopic methods to characterize chemical composition. Carbon mineralization was measured during a 90-day incubation, and samples before and after incubation were analyzed by chemical (elemental analysis) and spectroscopic (infrared and nuclear magnetic resonance) methods. Results were compared with those obtained by thermogravimetry (TG) and differential scanning calorimetry (DSC) techniques. Total amounts of CO2 respired indicated that the organic matter in the TS was the least stable, while that in the CS was the most stable. This was confirmed by changes detected with the spectroscopic methods in the composition of the organic wastes due to C mineralization. Differences were especially pronounced for TS, which showed a remarkable loss of aliphatic and proteinaceous compounds during the incubation process. TG, and especially DSC analysis, clearly reflected these differences between the three organic wastes before and after the incubation. Furthermore, the calculated energy density, which represents the energy available per unit of organic matter, showed a strong correlation with cumulative respiration. Results obtained support the hypothesis of a potential link between the thermal and biological stability of the studied organic materials, and consequently the ability of thermal analysis to characterize the maturity of municipal organic wastes and composts.  相似文献   
985.
Management of animal manures to provide nutrients for crop growth has generally been based on crop N needs. However, because manures have a lower N/P ratio than most harvested crops, N-based manure management often oversupplies the crop-soil system with P, which can be lost into the environment and contribute to eutrophication of water bodies. We examined the effects of N- vs. P-based manure applications on N and P uptake by alfalfa (Medicago sativa L.), corn (Zea mays L.) for silage, and orchardgrass (Dactylis glomerata L.), leaching below the root zone, and accumulation of P in soil. Treatments included N- and P-based manure rates, with no nutrient input controls and inorganically fertilized plots for comparison. Nitrate concentrations in leachate from inorganic fertilizer or manure treatments averaged 14 mg NO(3)-N L(-1), and did not differ by nutrient treatment. Average annual total P losses in leachate did not exceed 1 kg ha(-1). In the top 5 cm of soil in plots receiving the N-based manure treatment, soil test P increased by 47%, from 85 to 125 mg kg(-1). Nitrogen- and P-based manure applications did not differ in ability to supply nutrients for crop growth, or in losses of nitrate and total P in leachate. However, the N-based manure led to significantly greater accumulation of soil test P in the surface 5 cm of soil. Surface soil P accumulation has implications for increased risk of off-field P movement.  相似文献   
986.
Porteous F  Killham K  Meharg A 《Chemosphere》2000,41(10):1549-1554
The flow of carbon from plant roots into soil supports a range of microbial processes and is therefore critical to ecosystem function and health. Pollution-induced stress, which influences rhizosphere C flow is of considerable potential importance, and therefore needs to be evaluated. This paper reports on a method, based on reporter gene technology, for quantifying pollutant effects on rhizosphere C flow. The method uses the lux-marked rhizobacterium Pseudomonas fluorescens, where bioluminescence output of this biosensor is directly correlated with the metabolic activity and reports on C flow in root exudate. Plantago lanceolata was treated with paraquat (representing a model pollutant stress) in a simple microcosm system. The lux-biosensor response correlated closely with C concentrations in the exudate and demonstrated that the pollutant stress increased the C flow from the plantago roots, 24 h after application of the herbicide. The lux-reporter system therefore potentially offers a technique for use in assessing the impact of pollutant stress on rhizosphere C flow through the soil microbial biomass.  相似文献   
987.
This paper presents preliminary data on polybrominated diphenyl ethers (PBDEs) in the Scottish aquatic environment. Sediment and biota (fish liver, fish muscle and mussels) from a number of locations around Scotland were analysed for PBDEs with samples being from both remote and from potentially contaminated areas such as the former sewage sludge dump site at Garroch Head in the Clyde. PBDEs were measured in both cultivated, rope grown mussels and wild mussels collected from 5 sites around Scotland in 2006. Total PBDE concentrations (sum of tri- to hepta-BDEs) ranged from 相似文献   
988.
989.
The generation of reliable updated information is critical to support the harmonization of socio-economic and environmental issues in a context of sustainable development. The agro-environmental assessment and management of agricultural systems often relies on indicators that are necessary to make sound decisions. This work aims to provide an approach to (a) assess the environmental performance of commercial farms in the Pampas of Argentina, and (b) propose a methodological framework to calculate environmental indicators that can rapidly be applied to practical farming. 120 commercial farms scattered across the Pampas were analyzed in this study during 2002 and 2003. Eleven basic indicators were identified and calculation methods described. Such indicators were fossil energy (FE) use, FE use efficiency, nitrogen (N) balance, phosphorus (P) balance, N contamination risk, P contamination risk, pesticide contamination risk, soil erosion risk, habitat intervention, changes in soil carbon stock, and balance of greenhouse gases. A model named Agro-Eco-Index was developed on a Microsoft-Excel support to incorporate on-farm collected data and facilitate the calculation of indicators by users. Different procedures were applied to validate the model and present the results to the users. Regression models (based on linear and non-linear models) were used to validate the comparative performance of the study farms across the Pampas. An environmental dashboard was provided to represent in a graphical way the behavior of farms. The method provides a tool to discriminate environmentally friendly farms from those that do not pay enough attention to environmental issues. Our procedure might be useful for implementing an ecological certification system to reward a good environmental behavior in society (e.g., through tax benefits) and generate a commercial advantage (e.g., through the allocation of green labels) for committed farmers.  相似文献   
990.
Bottom sediments reflect in general the relative contamination of a sea area. Therefore, a great deal of monitoring work has been dedicated to the analysis of bottom sediments. Izmir Bay is a very important pollution centre in Turkish Aegean coast region due to a densely populated community, industrial complex and maritime transportation, and there are many streams flowing into the bay that pass through a number of industrial and agricultural areas. It had received the majority of domestic and industrial wastewaters until the wastewater treatment plant was constructed. It is well known that sediments play an important role as reservoirs of a fraction of the pollution in aquatic systems. Therefore, sediment samples were collected monthly from three stations which are located in the inner part of the bay during the period January to December 2003. Temporal variations and seasonal changes on their 210Po and 210Pb contents were examined, and the activity concentrations of 210Po and 210Pb were found to vary from 43±6 to 132±12 and 27±5 to 91±9 Bq kg???1 dry wt, respectively. The highest values of those natural radionuclides were measured at Kar??yaka Station because of the current systems of the bay. Seasonally, the 210Pb levels were found to increase during the winter time for all the stations.  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