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351.
352.
A comparative analysis was performed on eleven coal tars obtained from former manufactured gas plant sites in the eastern United States. Bulk properties analyzed included percent ash, Karl Fisher water content, viscosity and average molecular weight. Chemical properties included monocyclic- and polycyclic-aromatic hydrocarbon (PAH) concentrations, alkylated aromatic concentrations, and concentrations of aliphatic and aromatic fractions. It was found that there was at least an order-of-magnitude variation in all properties measured between the eleven coal tars. Additionally, two coal tars obtained from the same manufactured gas plant site had very different properties, highlighting that there can be wide variations in coal tar properties from different samples obtained from the same site. Similarities were also observed between the coal tars. The relative chemical distributions were similar for all coal tars, and the coal tars predominantly consisted of PAHs, with naphthalene being the single-most prevalent compound. The C(9-22) aromatic fraction, an indicator of all PAHs up to a molecular weight of approximately 276 gmole(-1), showed a strong power-law relationship with the coal tar average molecular weight (MW (ct)). And the concentrations of individual PAHs decreased linearly as MW (ct) increased up to ca. 1000 gmole(-1), above which they remained low and variable. Implications of these properties and their variation with MW (ct) on groundwater quality are discussed. Ultimately, while these similarities do allow generalities to be made about coal tars, the wide range of coal tar bulk and chemical properties reported here highlights the complex nature of coal tars. 相似文献
353.
Negri A Burns K Boyle S Brinkman D Webster N 《Environmental pollution (Barking, Essex : 1987)》2006,143(3):456-467
This study examined the concentrations of total hydrocarbons (THC), polychlorinated biphenyls (PCB), polyaromatic hydrocarbons (PAH), and trace metals (Cu, Zn, Cd, Pb, Hg and As) in marine sediments off Scott Base (NZ) and compared them with sediments near the highly polluted McMurdo Station (US) as well as less impacted sites including Turtle Rock and Cape Evans. The Antarctic mollusc, Laternula elliptica and three common sponge species were also analysed for trace metals. The mean THC concentration in sediments from Scott Base was 3 fold higher than the pristine site, Turtle Rock, but 10 fold lower than samples from McMurdo Station. McMurdo Station sediments also contained the highest concentrations of PAHs, PCBs and the trace metals, Cu, Zn, Pb, Cd and Hg. Copper was significantly higher in bivalves from McMurdo Station than other sites. Trace metal concentrations in sponges were generally consistent within sites but no spatial patterns were apparent. 相似文献
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Chadwick D. Rittenhouse Joshua J. Millspaugh Andrew B. Cooper Michael W. Hubbard Steven L. Sheriff Robert A. Gitzen 《Environmental and Ecological Statistics》2008,15(1):39-47
Wildlife resource selection studies typically compare used to available resources; selection or avoidance occurs when use
is disproportionately greater or less than availability. Comparing used to available resources is problematic because results
are often greatly influenced by what is considered available to the animal. Moreover, placing relocation points within resource
units is often difficult due to radiotelemetry and mapping errors. Given these problems, we suggest that an animal’s resource
use be summarized at the scale of the home range (i.e., the spatial distribution of all point locations of an animal) rather
than by individual points that are considered used or available. To account for differences in use-intensity throughout an
animal’s home range, we model resource selection using kernel density estimates and polytomous logistic regression. We present
a case study of elk (Cervus elaphus) resource selection in South Dakota to illustrate the procedure. There are several advantages of our proposed approach. First,
resource availability goes undefined by the investigator, which is a difficult and often arbitrary decision. Instead, the
technique compares the intensity of animal use throughout the home range. This technique also avoids problems with classifying
locations rigidly as used or unused. Second, location coordinates do not need to be placed within mapped resource units, which
is problematic given mapping and telemetry error. Finally, resource use is considered at an appropriate scale for management
because most wildlife resource decisions are made at the level of the patch. Despite the advantages of this use-intensity
procedure, future research should address spatial autocorrelation and develop spatial models for ordered categorical variables. 相似文献
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Andrew Carlin Caroline Kadji Mieke M. Cannie Serena Resta Xin Kang Jacques C. Jani 《黑龙江环境通报》2020,40(1):125-135
Extremes of fetal growth can increase adverse pregnancy outcomes, and this is equally applicable to single and multiple gestations. Traditionally, these cases have been identified using simple two-dimensional ultrasound which is quite limited by its low precision. Magnetic resonance imaging (MRI) has now been used for many years in obstetrics, mainly as an adjunct to ultrasound for congenital abnormalities and increasingly as part of the post-mortem examination. However, MRI can also be used to accurately assess fetal weight as first demonstrated by Baker et al in 1994, using body volumes rather than standard biometric measurements. This publication was followed by several others, all of which confirmed the superiority of MRI; however, despite this initial promise, the technique has never been successfully integrated into clinical practice. In this review, we provide an overview of the literature, detail the various techniques and formulas currently available, discuss the applicability to specific high-risk groups and present our vision for the future of MRI within clinical obstetrics. 相似文献
359.
Susannah Grice John Stedman Andrew Kent Melanie Hobson John Norris John Abbott Sally Cooke 《Atmospheric environment (Oxford, England : 1994)》2009,43(13):2154-2167
An assessment of recent trends in primary NO2 emissions has been carried out for ten case study locations across the European Union. Estimates of the percentage of NOx from road traffic emitted as primary NO2 (f-NO2) have been derived for 1995, 2000 and 2005 by combining the results of a literature survey of primary NO2 emission factors for different vehicle types and technologies with an emission inventory. Estimates of f-NO2 have also been derived from ambient monitoring data at roadside sites in each case study location using a model.The results of the analysis of trends show that f-NO2 has increased in recent years and that the rate of increase has been greatest since 2000. f-NO2 has increased from 8.6% in 2000 to 12.4% in 2004 as an average across the monitoring sites and from an average of 6.3% in 2000 to 10.6% in 2005 as an average of the emission inventory based calculations for the case study countries. f-NO2 is predicted to increase further to an average of 19.6% in 2010 and 32.0% in 2020 as a result of the further penetration of exhaust after treatment technologies for diesel vehicles in the fleets. This increase is expected to be offset by the large reduction in NOx emissions over this period, resulting in an increase in NO2 emissions from road traffic to 2015, followed by a decline to close to 2004 levels by 2020. Estimates of future ambient NO2 concentrations have also been calculated for the roadside monitoring sites included in the study. At 29 out of 45 of these sites the annual mean NO2 limit value is predicted to be exceeded in 2010. At 22 of these sites, the annual mean concentration is expected to remain above the limit value until 2020 and beyond. 相似文献
360.
Andrew Turner Heather Pollock Murray T. Brown 《Environmental pollution (Barking, Essex : 1987)》2009,157(8-9):2314-2319
The marine macroalga, Ulva lactuca, has been exposed to different concentrations of antifouling paint particles (4–200 mg L?1) in the presence of a fixed quantity of clean estuarine sediment and its photosynthetic response and accumulation of Cu and Zn monitored over a period of 2 days. An immediate (<2 h) toxic effect was elicited under all experimental conditions that was quantitatively related to the concentration of contaminated particles present. Likewise, the rate of leaching of both Cu and Zn was correlated with the concentration of paint particles added. Copper accumulation by the alga increased linearly with aqueous Cu concentration, largely through adsorption to the cell surface, but significant accumulation of Zn was not observed. Thus, in coastal environments where boat maintenance is practiced, discarded antifouling paint particles are an important source of Cu, but not Zn, to U. lactuca. 相似文献