全文获取类型
收费全文 | 912篇 |
免费 | 74篇 |
国内免费 | 290篇 |
专业分类
安全科学 | 15篇 |
废物处理 | 7篇 |
环保管理 | 292篇 |
综合类 | 474篇 |
基础理论 | 279篇 |
污染及防治 | 86篇 |
评价与监测 | 69篇 |
社会与环境 | 48篇 |
灾害及防治 | 6篇 |
出版年
2024年 | 3篇 |
2023年 | 16篇 |
2022年 | 20篇 |
2021年 | 22篇 |
2020年 | 24篇 |
2019年 | 31篇 |
2018年 | 31篇 |
2017年 | 39篇 |
2016年 | 45篇 |
2015年 | 52篇 |
2014年 | 52篇 |
2013年 | 82篇 |
2012年 | 47篇 |
2011年 | 68篇 |
2010年 | 47篇 |
2009年 | 58篇 |
2008年 | 39篇 |
2007年 | 58篇 |
2006年 | 77篇 |
2005年 | 50篇 |
2004年 | 43篇 |
2003年 | 49篇 |
2002年 | 30篇 |
2001年 | 47篇 |
2000年 | 27篇 |
1999年 | 31篇 |
1998年 | 31篇 |
1997年 | 22篇 |
1996年 | 23篇 |
1995年 | 21篇 |
1994年 | 16篇 |
1993年 | 13篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1983年 | 5篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有1276条查询结果,搜索用时 15 毫秒
931.
本文总结了近年来有毒物质对水生态系统的生态效应研究现状及发展趋势,提出了今后测定有毒物质生态效应应该注意的问题。 相似文献
932.
Kristy M. Ferraro Anthony L. Ferraro A. Z. Andis Arietta Nathalie R. Sommer 《Conservation biology》2023,37(4):e14101
Conservation science is a morally motivated field, with implicit and explicit values built into its practice. As such, conservationists must engage with conservation ethics to interrogate underlying values. We examine cutting-edge ecological science and contemporary ethics to revisit two conservation norms that have become dogmatic in the field: ecological collectives, but not individual animals, are valuable and anthropomorphism should be staunchly avoided. Emerging studies demonstrate that individuals and their intraspecific variation can be instrumentally valuable for conservation science, and there is an emerging consensus within environmental philosophy around the moral worth of individuals. Thus, we suggest conservation science should explicitly recognize the value of individuals. We also argue that avoiding anthropomorphism is detrimental to conservation because critical anthropomorphism enables a more nuanced scientific approach—allowing conservationists to ask enlightened questions with creativity and compassion. We provide evidence that both dogmatic norms are scientifically and morally outdated and propose new normative values to push conservation towards more robust science and ethical practice. 相似文献
933.
Centner TJ 《Environmental management》2006,37(6):745-752
As point sources of pollution in the United States, concentrated animal feeding operations (CAFOs) are subject to the National
Pollution Discharge Elimination System permitting system requirements. Changes to federal regulations in 2003 and a 2005 court
decision have increased the governmental oversight of CAFOs. Manure application to fields from “large CAFOs” that results
in unpermitted discharges can be regulated under the Clean Water Act. The U.S. Environmental Protection Agency’s interpretation
of agricultural stormwater discharges was approved so that unpermitted discharges may arise if an owner or operator of a CAFO
fails to apply manure correctly. Owners and operators do not, however, have a duty to secure governmental permits in the absence
of a discharge. Turning to the federal provisions regarding nutrient management plans, a court found that they were deficient.
Moreover, the federal government needs to reconsider requirements that would reduce pathogens from entering surface waters.
Although these developments should assist in reducing the impairment of U.S. waters, concern still exists. Greater oversight
of nutrient management plans and enhanced enforcement efforts offer opportunities to provide greater assurance that CAFO owners
and operators will not allow a discharge of pollutants to enter surface waters. 相似文献
934.
猪场废弃物强制通风静态仓堆肥系统的试验研究 总被引:1,自引:0,他引:1
通过组织5个猪场废弃物堆肥试验,度量温度、表观性状、体积、重量损失、全氮、全磷、大肠杆菌值、蛔虫卵杀灭率和发芽指数等指标,检验了开发的强制通风静态仓堆肥系统的性能.结果表明,除起始含水率为80%试验堆体因起始含水率过高导致发生厌氧反应外,其余4个堆体均实现堆肥无害化、减量化、稳定化和资源化的处理目标;堆肥温度维持50℃以上5~7 d,或55℃以上3 d是大肠杆菌值达到国家粪便无害化卫生标准的必要条件;堆肥过程能有效脱除堆料的生物毒性,后腐熟阶段是必需阶段;氮、磷、钾等主要营养元素在堆肥前后呈现"浓缩效应".因此,堆肥化能提高猪场废弃物肥效和利用价值. 相似文献
935.
936.
苯乙烯对水生生物的急性毒性效应研究 总被引:3,自引:0,他引:3
选择标准实验动物大型蚤(Daphina magna)和斑马鱼(Brachydanio rerio),探讨苯乙烯对水生生物的急性毒性效应和苯乙烯对水生生物的安全浓度。试验结果表明:大型蚤和斑马鱼随增加在含苯乙烯溶液中的暴露时间,半致死浓度呈下降趋势,反映大型蚤和斑马鱼对苯乙烯毒性的耐受程度随时间降低。苯乙烯对大型蚤和斑马鱼的96h-LC50值分别为11.35mg/L和121.04 mg/L。本试验分别通过每6h和每4h换水一次获得各时间段的大型蚤和斑马鱼的LC50值,由于在6h和4h内各浓度组中苯乙烯还存在较强的挥发,因此实际的致死浓度小于试验获得的大型蚤和斑马鱼LC50值。根据苯乙烯的毒性和遵循最敏感的原则,苯乙烯对水生生物的安全浓度应低于0.11 mg/L。 相似文献
937.
938.
Mapping Invasive Aquatic Vegetation in the Sacramento-San Joaquin Delta using Hyperspectral Imagery 总被引:5,自引:0,他引:5
Underwood EC Mulitsch MJ Greenberg JA Whiting ML Ustin SL Kefauver SC 《Environmental monitoring and assessment》2006,121(1-3):47-64
The ecological and economic impacts associated with invasive species are of critical concern to land managers. The ability to map the extent and severity of invasions would be a valuable contribution to management decisions relating to control and monitoring efforts. We investigated the use of hyperspectral imagery for mapping invasive aquatic plant species in the Sacramento-San Joaquin Delta in the Central Valley of California, at two spatial scales. Sixty-four flightlines of HyMap hyperspectral imagery were acquired over the study region covering an area of 2,139 km2 and field work was conducted to acquire GPS locations of target invasive species. We used spectral mixture analysis to classify two target invasive species; Brazilian waterweed (Egeria densa), a submerged invasive, and water hyacinth (Eichhornia crassipes), a floating emergent invasive. At the relatively fine spatial scale for five sites within the Delta (average size 51 ha) average classification accuracies were 93% for Brazilian waterweed and 73% for water hyacinth. However, at the coarser, Delta-wide scale (177,000 ha) these accuracy results were 29% for Brazilian waterweed and 65% for water hyacinth. The difference in accuracy is likely accounted for by the broad range in water turbidity and tide heights encountered across the Delta. These findings illustrate that hyperspectral imagery is a promising tool for discriminating target invasive species within the Sacramento-San Joaquin Delta waterways although more work is needed to develop classification tools that function under changing environmental conditions. 相似文献
939.
Spatial and Temporal Trends of Physicochemical Parameters in the Water of the Reconquista River (Buenos Aires, Argentina) 总被引:1,自引:0,他引:1
Castañé PM Rovedatti MG Topalián ML Salibián A 《Environmental monitoring and assessment》2006,117(1-3):135-144
The Reconquista river is one of the most polluted watercourses in Argentina. More than 3 million people and over 10,000 industries
are settled on its basin. The available data show that pollution is mainly related to the discharge of domestic and industrial
liquid wastes that are poured into the river almost untreated. At present no site of the river can be characterized as free
of pollutants. Samples were taken monthly from 5 sites of the river; some 18–20 physicochemical parameters were determined
in each sample. Analyses revealed significant differences in the degree of deterioration between sites. Two of them, close
to the source of the river (Cascallares-S1 and Paso del Rey-S2) resulted less polluted than the two points located close to the mouth of the river (San Martin-S4 and Bancalari-S5). The worsening of the water quality in S4–S5 was attributed to the discharges of the Moron stream, a tributary that flows into the main course of the river a complex
mixture of non treated waste waters. PCA was used in the ordination of samples (sites, season and physicochemical parameters).
In the PCA performed using all variables, the first principal component showed positive correlation with N-NH4
+, conductivity, orthophosphate, BOD5, COD and alkalinity, and negative correlation with DO. The second principal component was positively correlated with pH,
temperature and chlorophyll a and negatively with phenols and hardness. In respect to the spatial distribution, the plot of the scores for the first two
components of samples taken in each sampling station showed S1 and S2 values displayed farthest at the left side of the X axis with high DO. In contrast, S4 and S5 values stayed at the right side of this axis with high N-NH4
+, conductivity, orthophosphate, BOD5, COD and alkalinity; data of S3 were “intermediate". In order to identify seasonal trends in the concentration of contaminants scores of cases labeled by
season were plotted. The line drawn on the ordination plane showed that summer samples tended to converge to the upper right
portion of the graph where pollution variables had more importance on the first axis, and along the second axis with high
correlation with pH, temperature and chlorophyll a. Winter scores were settled in the left lower part of the plot with minor contribution of pollution parameters and more importance
of DO on the first axis. Samples of autumn and spring did not fit a clear cut pattern.
Deceased 相似文献
940.
Screening-level ecological risk assessments of di(2-ethylhexyl)phthalate (DEHP) for aquatic organisms in Japan were conducted using estimated statistical values based on surface water and sediment monitoring data and effect threshold values based on a large aquatic toxicity database. An alternative method is proposed to handle monitoring data that contain nondetects including multiple detection limits and to determine the statistical values of DEHP concentrations in Japanese surface waters. The No-Observed-Effect-Concentration (NOECwater) of DEHP for aquatic life of 77 μ g/L was determined giving equal importance to both physical effects probably caused by undissolved DEHP and to the intrinsic toxicity potentially caused by DEHP. The NOECsediment of 615,000 μg/kg was determined by the Equilibrium Partitioning (EqP) theory, conservatively assuming a threshold effect level in the water column as the water solubility of 3 μ g/L. The potential risks of DEHP in Japanese water environments were characterized simply by comparing the margin of exposure (MOE) with a specified uncertainty multiplier (UM). The MOE is expressed as the ratio of NOECwater or NOECsediment to the expected environmental concentrations such as the 95th percentiles of the estimated DEHP concentration distributions for surface water or sediment. The results of risk characterization show that all MOE values calculated using the statistical values of DEHP concentrations in Japanese surface waters and sediments are above 10, indicating minimal risk. Although the DEHP concentrations of some surface water samples showed MOE values of less than 10, considering environmental chemistry such as bioavailable fractions and the form of existence of DEHP in a water environment, we conclude that the current levels of DEHP are of little concern to aquatic life in the majority of Japanese surface waters and sediments. 相似文献