全文获取类型
收费全文 | 16673篇 |
免费 | 183篇 |
国内免费 | 145篇 |
专业分类
安全科学 | 462篇 |
废物处理 | 642篇 |
环保管理 | 2363篇 |
综合类 | 2602篇 |
基础理论 | 4573篇 |
环境理论 | 5篇 |
污染及防治 | 4355篇 |
评价与监测 | 1030篇 |
社会与环境 | 866篇 |
灾害及防治 | 103篇 |
出版年
2022年 | 113篇 |
2021年 | 132篇 |
2020年 | 108篇 |
2019年 | 152篇 |
2018年 | 233篇 |
2017年 | 226篇 |
2016年 | 366篇 |
2015年 | 252篇 |
2014年 | 367篇 |
2013年 | 1289篇 |
2012年 | 458篇 |
2011年 | 657篇 |
2010年 | 552篇 |
2009年 | 535篇 |
2008年 | 706篇 |
2007年 | 716篇 |
2006年 | 681篇 |
2005年 | 512篇 |
2004年 | 602篇 |
2003年 | 532篇 |
2002年 | 489篇 |
2001年 | 713篇 |
2000年 | 474篇 |
1999年 | 290篇 |
1998年 | 248篇 |
1997年 | 220篇 |
1996年 | 233篇 |
1995年 | 249篇 |
1994年 | 275篇 |
1993年 | 223篇 |
1992年 | 251篇 |
1991年 | 228篇 |
1990年 | 256篇 |
1989年 | 240篇 |
1988年 | 194篇 |
1987年 | 173篇 |
1986年 | 160篇 |
1985年 | 171篇 |
1984年 | 193篇 |
1983年 | 181篇 |
1982年 | 186篇 |
1981年 | 182篇 |
1980年 | 143篇 |
1979年 | 156篇 |
1978年 | 135篇 |
1977年 | 117篇 |
1975年 | 118篇 |
1974年 | 116篇 |
1973年 | 111篇 |
1972年 | 133篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Mercury and trace elements in cloud water and precipitation collected on Mt. Mansfield,Vermont 总被引:1,自引:0,他引:1
Malcolm EG Keeler GJ Lawson ST Sherbatskoy TD 《Journal of environmental monitoring : JEM》2003,5(4):584-590
The lack of high quality measurements of Hg and trace elements in cloud and fog water led to the design of a new collector for clean sequential sampling of cloud and fog water. Cloud water was collected during nine non-precipitating cloud events on Mt. Mansfield, VT in the northeastern USA between August 1 and October 31, 1998. Sequential samples were collected during six of these events. Mercury cloud water concentrations ranged from 7.5 to 71.8 ng l(-1), with a mean of 24.8 ng l(-1). Liquid water content explained about 60% of the variability in Hg cloud concentrations. Highest Hg cloud water concentrations were found to be associated with transport from the Mid-Atlantic and Ohio River Valley, and lowest concentrations with transport from the north of Mt. Mansfield out of Canada. Twenty-nine event precipitation samples were collected during the ten-week cloud sampling period near the base of Mt. Mansfield as part of a long-term deposition study. The Hg concentrations of cloud water were similar to, but higher on average (median of 12.5 ng l(-1)) than Hg precipitation concentrations (median of 10.5 ng l(-1)). Cloud and precipitation samples were analyzed for fifteen trace elements including Mg, Cu, Zn, As, Cd and Pb by ICP-MS. Mean concentrations were higher in cloud water than precipitation for elements with predominately anthropogenic, but not crustal origin in samples from the same source region. One possible explanation is greater in-cloud scavenging of crustal elements in precipitating than non-precipitating clouds, and greater below-cloud scavenging of crustal than anthropogenic aerosols. 相似文献
82.
Kristina?D.?RothleyEmail author Charlene?Rae 《Environmental Modeling and Assessment》2005,10(2):107-113
In this paper we apply graph theory in a reserve selection exercise to explore the tradeoffs between maintaining connectivity and minimizing the total area of a protected area network. Rather than focus on a single organism, we used a multi-species approach and looked at the tradeoff curves for organisms with varying dispersal abilities. We first generated the tradeoff curves using a graph-based metric to determine the importance of individual patches for maintaining connectivity. We then performed an analogous set of analyses using patch size as a surrogate measure of importance. 相似文献
83.
During the last decades, considerable research on methane production in the rumen and its inhibition has been carried out. Initially, as methane production represents a significant loss of gross energy in the feed (2–15%), the ultimate goal of such intervention in rumen fermentation was an increase in feed efficiency. A second reason favouring research on methane inhibition is its role in the global warming phenomenon and in the destruction of the ozone layer. In this review, the authors describe briefly several interventions for reducing methane emission by ruminants. The objective can be reached by intervention at the dietary level by ration manipulation (composition, feeding level) or by the use of additives or supplements. Examples of additives are polyhalogenated compounds, ionophores and other antibiotics. Supplementation of the ration with lipids also lowered methanogenesis. More biotechnological interventions, e.g., defaunation, probiotics and introduction of reductive acetogenesis in the rumen, are also mentioned. It can be concluded that drastic inhibition of methane production is not unequivocally successful as a result of several factors, such as: instantaneous inhibition often followed by restoration of methanogenesis due to adaptation of the microbes or degradation of the additive, toxicity for the host animal, negative effects on overall digestion and productive performance. Therefore, methanogenesis and its inhibition cannot be considered as a separate part of rumen fermentation and its consequences on the animal should be taken into account. 相似文献
84.
Methods derived from time-series analysis are proposed for processing monitoring data. The necessity for the use of these methods is demonstrated. In a case study time-series analysis was applied to assess the impact of the closure of the Grevelingen estuary (S. W. Netherlands) in 1971 on a local wintering population of Oystercatchers (Haematopus ostralegus) in the adjacent Oosterschelde estuary.Communication No. 328 of the Delta Institute for Hydrobiological Research. 相似文献
85.
86.
87.
Effects of Roadway Crossings on Leaf Litter Processing and Invertebrate Assemblages in Small Streams
The effects of the Maine Turnpike (Interstate 95) on leaf litter processing were examined in five first- and second-order coastal plain streams in southern Maine, U.S.A. Invertebrate assemblages and red maple leaf softening and loss rates were compared at 53 stations arrayed upstream and downstream of the turnpike. Litter softening rate was not affected by the roadway. Litter loss rate was significantly faster at downstream stations (-0.0024 degree-day(-1)) than at upstream stations or at stations nearest the roadway, which were not different from each other (-0.0022 degree-day(-1)). Litter softening and loss rates were more strongly related to physical and chemical habitat variables than to shredder assemblage characteristics. Significant among-stream differences were observed in most community structural metrics and in biomass of important shredder taxa, but effects of the roadway were rarely consistent among streams. This is attributed in part to habitat variation, which was greater among streams than within streams. This study suggests that while the presence of the Maine Turnpike may influence stream water quality and habitat structure, the relatively subtle effects of roadway runoff and associated habitat modifications on stream ecosystem processes are masked by within- and among-stream variability in litter processing and leaf pack invertebrate assemblage structure. 相似文献
88.
Yafa C Farmer JG Graham MC Bacon JR Barbante C Cairns WR Bindler R Renberg I Cheburkin A Emons H Handley MJ Norton SA Krachler M Shotyk W Li XD Martinez-Cortizas A Pulford ID MacIver V Schweyer J Steinnes E Sjøbakk TE Weiss D Dolgopolova A Kylander M 《Journal of environmental monitoring : JEM》2004,6(5):493-501
Given the increasing interest in using peat bogs as archives of atmospheric metal deposition, the lack of validated sample preparation methods and suitable certified reference materials has hindered not only the quality assurance of the generated analytical data but also the interpretation and comparison of peat core metal profiles from different laboratories in the international community. Reference materials play an important role in the evaluation of the accuracy of analytical results and are essential parts of good laboratory practice. An ombrotrophic peat bog reference material has been developed by 14 laboratories from nine countries in an inter-laboratory comparison between February and October 2002. The material has been characterised for both acid-extractable and total concentrations of a range of elements, including Al, As, Ca, Cd, Cr, Cu, Fe, Hg, Mg, Mn, Na, Ni, P, Pb, Ti, V and Zn. The steps involved in the production of the reference material (i.e. collection and preparation, homogeneity and stability studies, and certification) are described in detail. 相似文献
89.
A pilot project to detect and forecast harmful algal blooms in the northern Gulf of Mexico 总被引:1,自引:0,他引:1
More timely access to data and information on the initiation, evolution and effects of harmful algal blooms can reduce adverse impacts on valued natural resources and human health. To achieve this in the northern Gulf of Mexico, a pilot project was initiated to develop a user-driven, end-to-end (measurements to applications) observing system. A key strategy of the project is to coordinate existing state, federal and academic programs at an unprecedented level of collaboration and partnership. Resource managers charged with protection of public health and aquatic resources require immediate notice of algal events and a forecast of when, where and what adverse effects will likely occur. Further, managers require integrated analyses and interpretations, rather than raw data, to make effective decisions. Consequently, a functional observing system must collect and transform diverse measurements into usable forecasts. Data needed to support development of forecasts will include such properties as sea surface temperature, winds, currents and waves; precipitation and freshwater flows with related discharges of sediment and nutrients; salinity, dissolved oxygen, and chlorophyll concentrations (in vivo fluorescence); and remotely-sensed spatial images of sea surface chlorophyll concentrations. These data will be provided via a mixture of discrete and autonomous in situ sensing with near real-time data telemetry, and remote sensing from space (SeaWiFS), aircraft (hyperspectral imagery) or land (high-frequency radar). With calibration across these platforms, the project will ultimately provide a 4-dimensional visualization of harmful algae events in a time frame suitable to resource managers. 相似文献
90.
Tansy CL Senthilkumar K Pastva SD Kannan K Bowerman WW Masunaga S Giesy JP 《Environmental monitoring and assessment》2003,83(1):17-33
In South Carolina, U.S.A., mink have been reintroduced from two apparently healthy populations to areas where populations haveexisted in the past but have been extirpated. High mortality wasobserved during transport of mink from the source populations. Inorder to elucidate the potential effects of dioxin-like compoundson the survival and reproduction of mink, concentrations of totalpolychlorinated biphenyls (PCBs), p,p-DDE, dioxin-likePCBs, polychlorinated dibenzo-p-dioxins (PCDDs), anddibenzofurans (PCDFs) were measured in livers of mink collectedfrom the source populations in South Carolina and Louisiana. Concentrations of total 2,3,7,8-tetrachlorodibenzo-p-dioxinequivalents (TEQs) for the South Carolina and Louisiana mink were21 and 14 pg g-1, wet wt., respectively. PCB and TEQ concentrations were close to the threshold values that can, under laboratory conditions, elicit toxic effects in ranchmink. Therefore, any additional exposures of these populations toTEQs might adversely affect their populations. 相似文献