全文获取类型
收费全文 | 27265篇 |
免费 | 1864篇 |
国内免费 | 3118篇 |
专业分类
安全科学 | 4194篇 |
废物处理 | 842篇 |
环保管理 | 5878篇 |
综合类 | 12458篇 |
基础理论 | 2722篇 |
环境理论 | 23篇 |
污染及防治 | 1595篇 |
评价与监测 | 1393篇 |
社会与环境 | 1849篇 |
灾害及防治 | 1293篇 |
出版年
2024年 | 45篇 |
2023年 | 281篇 |
2022年 | 502篇 |
2021年 | 699篇 |
2020年 | 765篇 |
2019年 | 638篇 |
2018年 | 577篇 |
2017年 | 770篇 |
2016年 | 1005篇 |
2015年 | 999篇 |
2014年 | 1254篇 |
2013年 | 1531篇 |
2012年 | 1792篇 |
2011年 | 2036篇 |
2010年 | 1443篇 |
2009年 | 1593篇 |
2008年 | 1247篇 |
2007年 | 1770篇 |
2006年 | 1823篇 |
2005年 | 1451篇 |
2004年 | 1269篇 |
2003年 | 1314篇 |
2002年 | 1086篇 |
2001年 | 947篇 |
2000年 | 895篇 |
1999年 | 804篇 |
1998年 | 599篇 |
1997年 | 489篇 |
1996年 | 417篇 |
1995年 | 388篇 |
1994年 | 317篇 |
1993年 | 282篇 |
1992年 | 228篇 |
1991年 | 171篇 |
1990年 | 120篇 |
1989年 | 77篇 |
1988年 | 78篇 |
1987年 | 57篇 |
1986年 | 48篇 |
1985年 | 53篇 |
1984年 | 44篇 |
1983年 | 38篇 |
1982年 | 35篇 |
1981年 | 30篇 |
1980年 | 36篇 |
1979年 | 45篇 |
1978年 | 24篇 |
1977年 | 22篇 |
1973年 | 24篇 |
1971年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 984 毫秒
111.
Llansó RJ Dauer DM Vølstad JH Scott LC 《Environmental monitoring and assessment》2003,81(1-3):163-174
The Chesapeake Bay benthic index of biotic integrity (B-IBI) was developed to assess benthic community health and environmental quality in Chesapeake Bay. The B-IBI provides Chesapeake Bay monitoring programs with a uniform tool with which to characterize bay-wide benthic community condition and assess the health of the Bay. A probability-based design permits unbiased annual estimates of areal degradation within the Chesapeake Bay and its tributaries with quantifiable precision. However, of greatest interest to managers is the identification of problem areas most in need of restoration. Here we apply the B-IBI to benthic data collected in the Bay since 1994 to assess benthic community degradation by Chesapeake Bay Program segment and water depth. We used a new B-IBI classification system that improves the reliability of the estimates of degradation. Estimates were produced for 67 Chesapeake Bay Program segments. Greatest degradation was found in areas that are known to experience hypoxia or show toxic contamination, such as the mesohaline portion of the Potomac River, the Patapsco River, and the Maryland mainstem. Logistic regression models revealed increased probability of degraded benthos with depth for the lower Potomac River, Patapsco River, Nanticoke River, lower York River, and the Maryland mainstem. Our assessment of degradation by segment and water depth provided greater resolution of relative condition than previously available, and helped define the extent of degradation in Chesapeake Bay. 相似文献
112.
The emission of the dioxin-like compounds from on-site waste incinerators of seven schools in Kyonggi Province of Korea was evaluated by determination of the cytochrome P4501A(CYP1A) catalytic activity and antiestrogenic activity using cell culturemicrobioassay. The residue samples were extracted in a Soxhlet apparatus using toluene for 20 hr. The concentrated crude extractswere fractionated with a basic alumina column. Dioxin-like compounds were then extracted. Induction of CYP1A activity in a rat(H4IIE) hepatoma cell line was used as indicator of biologicaleffect of incinerator residues and measured as 7-ethoxyresorufin-O-deethylase(EROD) activities. The EROD activities of fraction II extracts (one of the two extracts) in the H4IIE cells were from 0.044±0.002 to 4.424±0.351 ng-TEQ g-1 (TCDD Toxicity equivalent), showing relatively high inducing capacity. Antisetrogenicity of the extracts was measured as decrease in E2-induced cell proliferation. Most of the extracts showed antiestrogenic activity in MCF7-BUS cell.The TEQ levels of the incinerator residues and the antiestrogenicactivities were in good correlation, strongly suggesting that thepotent toxic emissions were indeed produced from the on-site school waste semi-incinerators and could cause the antiestrogenicity. 相似文献
113.
114.
115.
116.
Selecting Socio-Economic Metrics for Watershed Management 总被引:1,自引:0,他引:1
The selection of social and economic metrics to document baseline conditions and analyze the dynamic relationships between
ecosystems and human communities are important decisions for scientists, managers, and watershed citizens. A large variety
of social and economic data is available but these have limited use without theoretical frameworks. In this paper, several
frameworks for reviewing social-ecosystem relations are offered, namely social sanctions, sense of place, civic structure,
and cultural differences. Underlying all of these frameworks are attitudes, beliefs, values, and norms that affect which questions
are asked and which indicators are chosen. Much work and significant challenges remain in developing a standard set of spatially
based socio-economic metrics for watershed management. 相似文献
117.
The increasing use of the landscape by humans has led to important diminutions of natural surfaces. The remaining patches
of wild habitat are small and isolated from each other among a matrix of inhospitable land-uses. This habitat fragmentation,
by disabling population movements and stopping their spread to new habitats, is a major threat to the survival of numerous
plant and animal species. We developed a general model, adaptable for specific species, capable of identifying suitable habitat
patches within fragmented landscapes and investigating the capacity of populations to move between these patches. This approach
combines GIS analysis of a landscape, with spatial dynamic modeling. Suitable habitat is identified using a threshold area
to perimeter ratio. Potential movement pathways of species between habitat patches are modeled using a cellular automaton.
Habitat connectivity is estimated by overlaying habitat patches with movement pathways. The maximum potential population is
calculated within and between connected habitat patches and potential risk of inbreeding within meta-populations is considered.
The model was tested on a sample map and applied to scenario maps of predicted land-use change in the Peoria Tri-county region
(IL). It (1) showed area of natural area alone was insufficient to estimate the consequences on animal populations; (2) underscored
the necessity to use approaches investigating the effect of land-use change spatially through the landscape and the importance
of considering species-specific life history characteristics; and (3) highlighted the model's potential utility as an indicator
of species likelihood to be affected negatively by land-use scenarios and therefore requiring detailed investigation. 相似文献
118.
Wiersma YF 《Environmental monitoring and assessment》2005,100(1-3):1-9
Environmental benchmarks are widely used in Canadian environmental assessment as a standard against which to monitor air or water quality in response to human activities in the environment. Recent work in Canada has developed the concept of ecological benchmarks as a complement to environmental benchmarks. However, implementation of ecological benchmarks may be challenging. This paper presents an analogy between ecological benchmarks and the more commonly used environmental benchmarks, as an attempt to increase understanding and use of ecological benchmarks in resource management, assessment, and monitoring. Ecological benchmarks, and their corresponding indicators, will be challenging to identify and use. However, through the use of the principles of adaptive management, effective ecological indicators and benchmarks can be established. Although it is essential that ecological benchmarks are site-specific, the analogy and general principles outlined here are applicable to assessment and monitoring in any part of the world. 相似文献
119.
120.