全文获取类型
收费全文 | 895篇 |
免费 | 69篇 |
国内免费 | 88篇 |
专业分类
安全科学 | 187篇 |
废物处理 | 19篇 |
环保管理 | 192篇 |
综合类 | 358篇 |
基础理论 | 110篇 |
污染及防治 | 20篇 |
评价与监测 | 51篇 |
社会与环境 | 52篇 |
灾害及防治 | 63篇 |
出版年
2024年 | 4篇 |
2023年 | 16篇 |
2022年 | 34篇 |
2021年 | 41篇 |
2020年 | 32篇 |
2019年 | 27篇 |
2018年 | 21篇 |
2017年 | 24篇 |
2016年 | 30篇 |
2015年 | 36篇 |
2014年 | 34篇 |
2013年 | 44篇 |
2012年 | 49篇 |
2011年 | 69篇 |
2010年 | 45篇 |
2009年 | 46篇 |
2008年 | 58篇 |
2007年 | 47篇 |
2006年 | 51篇 |
2005年 | 46篇 |
2004年 | 38篇 |
2003年 | 33篇 |
2002年 | 27篇 |
2001年 | 28篇 |
2000年 | 21篇 |
1999年 | 12篇 |
1998年 | 14篇 |
1997年 | 18篇 |
1996年 | 23篇 |
1995年 | 15篇 |
1994年 | 12篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1988年 | 3篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有1052条查询结果,搜索用时 671 毫秒
471.
472.
473.
474.
475.
Watershed-Based Survey Designs 总被引:2,自引:0,他引:2
Detenbeck NE Cincotta D Denver JM Greenlee SK Olsen AR Pitchford AM 《Environmental monitoring and assessment》2005,103(1-3):59-81
Watershed-based sampling design and assessment tools help serve the multiple goals for water quality monitoring required under
the Clean Water Act, including assessment of regional conditions to meet Section 305(b), identification of impaired water
bodies or watersheds to meet Section 303(d), and development of empirical relationships between causes or sources of impairment
and biological responses. Creation of GIS databases for hydrography, hydrologically corrected digital elevation models, and
hydrologic derivatives such as watershed boundaries and upstream–downstream topology of subcatchments would provide a consistent
seamless nationwide framework for these designs. The elements of a watershed-based sample framework can be represented either
as a continuous infinite set defined by points along a linear stream network, or as a discrete set of watershed polygons.
Watershed-based designs can be developed with existing probabilistic survey methods, including the use of unequal probability
weighting, stratification, and two-stage frames for sampling. Case studies for monitoring of Atlantic Coastal Plain streams,
West Virginia wadeable streams, and coastal Oregon streams illustrate three different approaches for selecting sites for watershed-based
survey designs. 相似文献
476.
477.
通过科学合理地划分河段实现栖息地分类管理是恢复流域生物完整性的重要内容之一.湖泊流域入湖河流空间尺度小、坡降大、生态学过程差异性显著的特点导致其河段类型复杂多样,与河流流域河段类型的大尺度特征具有明显区别,因此,河流流域河段划分指标及其方法不适用于湖泊流域,亟需发展以栖息地分类管理为目的的湖泊流域河段划分方法.本文通过回顾河流分类的概念、划分依据及划分方法的发展历程,明确了湖泊流域河段划分理论基础,提出了基于保护目标制定的湖泊流域河段划分方法,为恢复湖泊流域生物完整性提供了更为精细的管理单元.同时,以滇池流域为例,通过筛选与大型底栖动物敏感种群和濒危种群显著相关的环境因子,建立了由地貌类型、土地利用方式、河水来源、河道人工化情况及水体营养程度构成的指标划分体系;在实现各划分指标空间化的基础上,利用空间叠加聚类技术手段,将滇池流域入湖河流划分为9个河段类型,为滇池流域水生态系统健康恢复提供了科学依据. 相似文献
478.
按国家关于清洁生产审核的具体环保要求,针对二氧化硫产出量与总量控制的相关标准,提出关于二氧化硫专项清洁生产审核研究的具体思路.根据对哈尔滨某集团有限公司SO2专项清洁生产审核,通过组织筹划、预评估,确定二氧化硫作为清洁生产审核的重点并制定清洁生产目标,评估过程中要依据具体的国家环保要求,对于确定的方案进行环境-经济-社会效益的分析.共提出10个清洁生产方案,其中无/低费方案8个,中/高费方案2个. 相似文献
479.
Integration of Optical and Microwave Remote Sensing Data for Agricultural Land Use Classification 总被引:1,自引:0,他引:1
An agricultural land use classification of Oltrepo' Pavese region (in Northern Italy) is performed through integration of remote sensing data from optical and radar sensors. The source of optical data was a Landsat-TM image acquired on April 1994, while the source of microwave data was a contemporaneous image of the new radar sensor SIR-C/X-SAR which was flown on-board the Space Shuttle during an experimental mission over the chosen test site. Then, they were combined through calculation of the principal components of the multidimensional data sets and a final classification was carried out and compared with the classifications obtained from optical and radar recordings separately. Results showed remarkable improvement in the classification accuracy of seedbeds and uncultivated fields with radar recordings and of herbaceous crop type with integrated data. Potential ability of a multi-sensor classification and limits of a single-temporal approach are discussed. 相似文献
480.
The honeybee Apis mellifera has evolved in different environments and has developed different ecotypes. The objective of the Honeybee Genetic program in Argentina (MeGA) is to select honeybees adapted to different regions in the country using an important number of colonies as base population. In the last years, morphometric analyses are being incorporated into the Program as a tool for characterization of genetic materials; this fact has motivated the present work. A random sample of honeybee workers (250) was taken from 30 colonies situated in different regions in the country. The proboscis, right hind leg, right forewing and hind wing were placed on a slide and the following variables were measured: length and width of forewing and hind wing, different angles and length of wing veins, the length of the tibia, femur and metatarsi, the width of the metatarsi and the length of the proboscis. Thirty morphometrical variables were analyzed and the distribution and relation between them were recorded. 相似文献