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621.
野生大豆(Glycine soja)为我国二级濒危保护植物.通过野外调查和室内实验,利用TWINSPAN分类、DCA间接排序和CCA直接排序的数量分析方法,定量研究了野生大豆群落分布与环境之间的关系.结果表明,TWINSPAN分类将106个样方分为4个群丛组,分别代表水库撂荒地、湿河床、较湿石质河床和较干土质河床4种不同的生境类型,不同的群从组在DCA排序轴上的位置基本反映出其分布与环境梯度的关系;进一步的DCA间接排序和CCA直接排序分析显示,土壤含水量和土壤养分是决定各个不同野生大豆群丛组分布的关键因子;最后通过建立野生大豆3个种群特征与DCA排序第一轴的回归关系分析,确定了盖度和重要值在反映野生大豆种群优势度上要优于高度.图4表1参19 相似文献
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Assessment of 2010 air quality in two Alpine valleys from modelling: Weather type and emission scenarios 总被引:1,自引:0,他引:1
G. Brulfert C. Chemel E. Chaxel J.-P. Chollet B. Jouve H. Villard 《Atmospheric environment (Oxford, England : 1994)》2006,40(40):7893-7907
Alpine valleys are sensitive to anthropogenic emissions. Local atmospheric dynamics are a key factor that may lead to an accumulation of pollutants in the bottom of the Chamonix and Maurienne valleys. Assessment of 2010 pollutant concentrations variability needs to take these specificities into account. A meteorological data classification is combined with different emission scenarios in order to run an air quality model. Using simulations of representative scenarios rather than complete years allows for a fine spatial and temporal representation of local atmospheric dynamics and gives access to detailed chemical breakdowns. Results demonstrate the variability of primary and secondary species due to emissions and the predominance of local effects on pollutant concentrations. 相似文献
625.
为更加精准地判定采空区自燃危险区域,对煤自燃极限参数的计算方法进行改进,采用能量守恒微分方程的分析解计算煤自燃所需必要条件的极限值;以内蒙古凯达煤矿为例对该方法进行验证,根据浮煤的物性参数以及采空区环境条件,计算分析46205工作面回风侧采空区煤的自燃危险性;根据采空区漏风条件以及煤自燃所需要的氧浓度值,分析在遗煤较厚... 相似文献
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Mapping wetlands in the Lower Mekong Basin for wetland resource and conservation management using Landsat ETM images and field survey data 总被引:1,自引:0,他引:1
The Mekong River Basin is considered to be the second most species rich river basin in the world. The 795,000 km(2) catchment encompasses several ecoregions, incorporating biodiverse and productive wetland systems. Eighty percent of the rapidly expanding population of the Lower Mekong Basin (LMB), made up in part by Lao PDR, Thailand, Cambodia and Viet Nam, live in rural areas and are heavily reliant on wetland resources. As the populations of Cambodia and Lao PDR will double in the next 20 years, pressure on natural resources and particularly wetlands can only increase. For development planning, resource and conservation management to incorporate wetland issues, information on the distribution and character of Mekong wetlands is essential. The existing but outdated wetland maps were compiled from secondary landuse-landcover data, have limited coverage, poor thematic accuracy and no meta-data. Therefore the Mekong River Commission (MRC) undertook to produce new wetland coverage for the LMB. As resources, funding and regional capacity are limited, it was determined that the method applied should use existing facilities, be easily adaptable, and replicable locally. For the product to be useful it must be accepted by local governments and decision makers. The results must be of acceptable accuracy (>75%) and the methodology should be relatively understandable to non-experts. In the first stage of this exercise, field survey was conducted at five pilot sites covering a range of typical wetland habitats (MRC wetland classification) to supply data for a supervised classification of Landsat ETM images from the existing MRC archive. Images were analysed using ERDAS IMAGINE and applying Maximum Likelihood Classification. Field data were reserved to apply formal accuracy assessment to the final wetland habitat maps, with resulting accuracy ranging from 77 to 94%. The maps produced are now in use at a Provincial and National level in three countries for resource and conservation planning and management applications, including designation of a Ramsar wetland site of international importance. 相似文献
629.
企业职业危害综合评价和风险分级系统及其应用 总被引:4,自引:2,他引:2
我国企业职业危害形势依然十分严峻,2007年共诊断各类职业病14296例,较2006年增加了24.11%。由于国家在一段时期内不太可能大幅度增加监管人员数量,因此,实施企业职业危害分级监管成为职业危害监管工作的一个紧迫需求。本文从提高企业监管信息化水平角度出发,开发企业职业危害综合评价和风险分级系统。系统即可为政府实施职业危害分级监管提供强有力的技术支撑,也可应用在企业的作业场所职业危害管理工作中,从而提高政府和企业职业危害管理工作技术水平和效率。 相似文献
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Brett B. Roper John M. Buffington Eric Archer Chris Moyer Mike Ward 《Journal of the American Water Resources Association》2008,44(2):417-427
Abstract: Consistency in determining Rosgen stream types was evaluated in 12 streams within the John Day Basin, northeastern Oregon. The Rosgen classification system is commonly used in the western United States and is based on the measurement of five stream attributes: entrenchment ratio, width‐to‐depth ratio, sinuosity, slope, and substrate size. Streams were classified from measurements made by three monitoring groups, with each group fielding multiple crews that conducted two to three independent surveys of each stream. In only four streams (33%) did measurements from all crews in all monitoring groups yield the same stream type. Most differences found among field crews and monitoring groups could be attributed to differences in estimates of the entrenchment ratio. Differences in entrenchment ratio were likely due to small discrepancies in determination of maximum bankfull depth, leading to potentially large differences in determination of Rosgen’s flood‐prone width and consequent values of entrenchment. The result was considerable measurement variability among crews within a monitoring group, and because entrenchment ratio is the first discriminator in the Rosgen classification, differences in the assessment of this value often resulted in different determination of primary stream types. In contrast, we found that consistently evaluated attributes, such as channel slope, rarely resulted in any differences in classification. We also found that the Rosgen method can yield nonunique solutions (multiple channel types), with no clear guidance for resolving these situations, and we found that some assigned stream types did not match the appearance of the evaluated stream. Based on these observations we caution the use of Rosgen stream classes for communicating conditions of a single stream or as strata when analyzing many streams due to the reliance of the Rosgen approach on bankfull estimates which are inherently uncertain. 相似文献