全文获取类型
收费全文 | 86538篇 |
免费 | 1219篇 |
国内免费 | 1063篇 |
专业分类
安全科学 | 3656篇 |
废物处理 | 3101篇 |
环保管理 | 13339篇 |
综合类 | 20927篇 |
基础理论 | 25690篇 |
环境理论 | 72篇 |
污染及防治 | 12687篇 |
评价与监测 | 5196篇 |
社会与环境 | 3655篇 |
灾害及防治 | 497篇 |
出版年
2022年 | 778篇 |
2021年 | 785篇 |
2020年 | 641篇 |
2019年 | 854篇 |
2018年 | 1105篇 |
2017年 | 1155篇 |
2016年 | 2118篇 |
2015年 | 1828篇 |
2014年 | 2576篇 |
2013年 | 9220篇 |
2012年 | 2022篇 |
2011年 | 2136篇 |
2010年 | 3202篇 |
2009年 | 3329篇 |
2008年 | 1652篇 |
2007年 | 1492篇 |
2006年 | 1954篇 |
2005年 | 2078篇 |
2004年 | 2346篇 |
2003年 | 2155篇 |
2002年 | 1729篇 |
2001年 | 1919篇 |
2000年 | 1810篇 |
1999年 | 1424篇 |
1998年 | 1351篇 |
1997年 | 1328篇 |
1996年 | 1456篇 |
1995年 | 1546篇 |
1994年 | 1446篇 |
1993年 | 1298篇 |
1992年 | 1283篇 |
1991年 | 1262篇 |
1990年 | 1210篇 |
1989年 | 1179篇 |
1988年 | 1017篇 |
1987年 | 954篇 |
1986年 | 982篇 |
1985年 | 1049篇 |
1984年 | 1143篇 |
1983年 | 1158篇 |
1982年 | 1167篇 |
1981年 | 1091篇 |
1980年 | 937篇 |
1979年 | 909篇 |
1978年 | 813篇 |
1977年 | 710篇 |
1976年 | 632篇 |
1975年 | 592篇 |
1973年 | 615篇 |
1972年 | 619篇 |
排序方式: 共有10000条查询结果,搜索用时 437 毫秒
481.
482.
483.
In the present study, the influence of aluminium on the regeneration potential of leaf and stem-cuttings of Portulaca oleracea was studied in order to identify a terrestrial plant species as an alternate biomonitoring toolof fresh water environment. The leaves and stem cuttings of theterrestrial plant, P. oleracea grew well in the distilled water producing adventitious and lateral roots. The aluminium treated leaves and stem cuttings showed a reduction in the growthof the adventitious and lateral roots and increase in the decay of leaves and stem cuttings with increasing aluminium concentration. The tolerance index calculated for the leaves and the stem cuttings showed that the leaves were more sensitivethan stems to aluminium. Since all the parameters studied showedconcentration dependent changes, the terrestrial plant, P. oleracea can be considered a suitable biomonitoring tool of fresh water environment besides its usage in the Al toxicity testing. 相似文献
484.
The Variability of Estimates of Variance, and Its Effect on Power Analysis in Monitoring Design 总被引:1,自引:0,他引:1
Power analysis can be a valuable aid in the design of monitoringprograms. It requires an estimate of variance, which may come from a pilot study or an existing study in a similar habitat. For marine benthic infauna, natural variation in abundances canbe considerable, raising the question of reliability of varianceestimates. We used two existing monitoring programs to generatemultiple estimates of variance. These estimates were found to differ from nominated best estimates by 50% or more in 43% of cases, in turn leading to under or over-estimation of samplesize in the design of a notional monitoring program. The twostudies, from the same general area, using the same samplingmethods and spanning a similar time scale, gave estimatesvarying by more than an order of magnitude for 25% of taxa.We suggest that pilot studies for ecological monitoring programsof marine infauna should include at least two sampling times. 相似文献
485.
Aerosol Scavenging: Model Application and Sensitivity Analysis in the Indian Context 总被引:1,自引:0,他引:1
Sulfate aerosols have been found to bethe major contributors to precipitation acidity. Thus,in view of the long-term ecological repercussions theyhave on aquatic ecosystems and their acidity-potential,the present analysis focuses on a case study applicationof the layer-averaged aerosol-scavenging model (Okita et al., 1996) for predicting values of the wet scavengingcoefficient and sulfate concentrations in precipitationsamples on the basis of the information available forsome selected Indian cities. Through sensitivityanalysis (Pandey et al., 1997) the scavengingcoefficient has been found to be very strongly dependenton precipitation intensity. Comparison of modelpredictions has been done with the measured values forDelhi, Mumbai, Calcutta and Chennai in India. 相似文献
486.
Wong MY Sauser KR Chung KT Wong TY Liu JK 《Environmental monitoring and assessment》2001,67(3):361-378
The green alga Selenastrum capricornutum expresses a uniqueascorbate peroxidase, that responds to copper and lead. Attemptswere made to test if this peroxidase could be used to monitor thelevels of copper and lead in natural waters. When S.capricornutum was exposed to a stormwater sample, the specificactivity of the peroxidase in the cell extract was commensuratewith the combined copper and lead contents in the sample. Theperoxidase responses were also correlated with the 96 hr biomasstoxicity assay of S. capricornutum. However, unlike thebiomass toxicity assay, the peroxidase activity was not affectedby the anions in the samples. The use of this peroxidase can beused as a marker for testing heavy metal toxicity in the water. 相似文献
487.
Osborn LV Kurek JT Kriech AJ Fehsenfeld FM 《Journal of environmental monitoring : JEM》2001,3(2):185-190
A subset of polycyclic aromatic compounds (PACs), which contain 4-6 annulated rings, has been documented as the source of carcinogenicity in animal skin painting studies of petroleum products and asphalt fumes (M. L. Machado, P. W. Beatty, J. C. Fetzer, A. H. Glickman and E. L. McGinnis, Fundam. Appl. Toxicol., 1993, 21, 492; T. A. Roy, S. W. Johnson, G. R. Blackburn and C. R. Mackerer, Fundam. Appl. Toxicol., 1988, 10, 466). Because of the chemical complexity of these materials, it has been difficult to identify the specific compounds within this broad range of PACs responsible for their carcinogenicity. An alternative approach using luminescence spectroscopy was taken in this study to quantify, without identification, a subset of these compounds that appears to cause cancer. The fluorescence response at a specific wavelength pair was obtained for 39 laboratory asphalt fume condensates from animal skin painting studies, yielding a linear correlation coefficient of R2 = 0.96 between the fluorescence response in these materials and the carcinogenicity found in animal studies. In the absence of other asphalt fume condensates from animal studies, 17 petroleum oils were also evaluated using this method and compared with the available animal skin painting data. The details of the method include a clean-up step that removes the highly polar compounds and spectral subtraction of two- and three-ring PAC interference, both of which add to the fluorescence response, yet were not found to contribute to a carcinogenic response from skin painting studies. Full scan fluorescence plots also produce a fingerprint which can be used to assess contamination, such as coal tar products or mixtures of materials, that are not defined as asphalt, yet may be present in the working environment. 相似文献
488.
B. Beck-Friis M. Pell U. Sonesson H. Jönsson H. Kirchmann 《Environmental monitoring and assessment》2000,62(3):317-331
Composting can be a source of N2O andCH4 production. In this investigation, differentcompost heaps of organic household waste weremonitored with the focus on potential formation ofCH4 and N2O in the heaps and emission ofthese gases from the heaps. The studied compost heapshad different compost ages, turning intervals andcompost sizes. The analysed compost gases containedbetween 1–3421 L of N2O-N L-1 and 0–470 mL of CH4 L-1. The emission rates ofN2O and CH4 from the compost heaps werebetween 1–1464 mg N2O m-2 day-1 and0–119 000 mg CH4 m-2 day-1. These verylarge differences in compost gas composition andemission indicate the importance of compostmanagement. The results also give an understanding ofwhere in the composting process an increasing emissionof N2O and CH4 can occur. 相似文献
489.
A multi-year programme was performed to assess the effects of atmospheric ethylene on potato (Solanum tuberosum L.) in the vicinity of polyethylene manufacturing plants. There was a strong temporal variation of the hourly ethylene concentrations measured close to the sources from 1982 through 1991. Growing seasonal means exceeded 12 g m–3 ethylene, the threshold for phytotoxic effects under laboratory conditions. Young test plants of potato showed an epinastic response to enhanced levels of ethylene. This response was reversible and did not occur when atmospheric ethylene was not detected. Based on hourly observations for the growing seasons of 1984 through 1991, epinasty occurred on average during circa 5% of the growing season and varied from circa 1% in 1985 to circa 18% in 1991. At night, ethylene concentrations were higher and epinasty was more frequent than during daylight hours. The intermittent exposures to ethylene did not affect tuber yield for the growing seasons of 1982 through 1990. The occurrence of epinasty indicated that ethylene exposure levels in the vicinity of the industrial sources might be sufficiently high to affect sensitive plants. 相似文献
490.
This study determined the spatial distribution of soiland of sediment-associated lead in Iqaluit, Nunavut.Samples were collected from the following areas:outside the built-up area of the town to reflectbackground concentrations; known or potential pointsources of lead, such as the Upper Base, the SylviaGrinnell Dump and the Metal Dump (North 40); andresidential and commercial areas of Iqaluit and Apex,a satellite community. In the laboratory, the <63 m sample fraction was analyzed for total lead andbioavailable lead, estimated by non-residual acidextractable lead content. The research findings revealthat elevated levels of bioavailable lead are presentin the study area. Total lead concentrations generallydo not exceed environmental guidelines. However, leadconcentrations in the Sylvia Grinnell Dump, and Apexand Iqaluit grid areas exceed health-based guidelines.The research concludes that there is not a serioushealth hazard posed by lead levels in the soil andsediment in the study area. However, severalenvironmental (elevated lead levels, bioavailableforms of lead and bare soil surfaces) and behaviouralfactors (vigorous and unsupervised play outside) maycreate a risk of lead exposure. 相似文献