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411.
To study the biodegradation rate of pyrene dissolved in liquid medium supplemented with mineral salts, a synchronous fluorimetry (SF) method was established. The limit of detection for pyrene dissolved in mineral salts medium (MSM) was determined as 0.19 ng/ml with a relative standard deviation of less than 1.3% (n = 9). The pyrene degrading rates of four bacterial strains were investigated using this method under the same experimental conditions. The degradation rates of the three active strains ranged from 76% to 87% after a 14-h incubation. The results were confirmed by the gas chromatography with a flame ionized detector (GC/FID) method. This implies that pyrene degradation can be directly monitored by the SF method without the solvent extraction of samples. The advantages of SF are that it is less laborious, faster, and less expensive than the GC/FID determination method with solvent extraction. The SF method provides a new tool for studying the degradation of polynuclear aromatic hydrocarbons (PAHs) in the natural environment and under experimental conditions. 相似文献
412.
The acute toxicity test is described in this experiment where the Collembola species Proisotoma minuta was exposed to herbicides in an artificial sea salt solution for seven days. The salt solution did not prohibit the insects' reproduction system. The seven day LD50 values for trifluralin, pendimethalin, metolachlor, prometryn, paraquat, atrazine, fluometuron, and diuron were 3.48, 10.4, 12.4, 13.0, 23.1, 33.4, 250, and 711 mg L(-1), respectively. A good correlation between toxicity of the compounds and their lipophilicity and vapor pressure was recorded in this study. 相似文献
413.
Characteristics of styrene degradation by Rhodococcus pyridinovorans isolated from a biofilter 总被引:1,自引:0,他引:1
A novel strain (PYJ-1) of Rhodococcus pyridinovorans that was isolated from a biofilter was able to degrade styrene at a maximum rate of 0.16 mg (mg protein)(-1) h(-1) in batch culture at 97 mg l(-1) of initial styrene gas concentration. The optimum pH and temperature for styrene degradation were 7 and 32 degrees C, respectively. The degradation kinetic constants were obtained using substrate inhibition kinetics. In a perlite-packed biofilter the maximum styrene removal rate by the strain was 279 gm(-3)h(-1). Styrene removal in the biofilter was more sensitive to the temperature than in the batch culture. 相似文献
414.
This study estimated the appropriate pollutant load reduction from point sources in Kwangyang Bay, Korea, using an eco-hydrodynamic model. The total chemical oxygen demand (COD), nitrogen (TN), and phosphorus (TP) loads from rivers and ditches that provide input to the bay were approximately 2.8x10(4), 2.5x10(4), and 5.9x10(2) kg day-1, respectively. Wastewater discharge from industrial complexes was the greatest contributor to pollutant loads in the inner part of the bay. COD values in the inner part of the bay were greater than 3.0 mg l-1, and exceeded Korean seawater quality grade III limits. A residual current was simulated, using a hydrodynamic model, to have a slightly complicated pattern in the inner part of the bay, ranging from 0.001 to 8 cm s-1. In the outer part of the bay, the simulated current flowed out to the South Sea with a southward flow at a maximum of 15 cm s-1. The results of the ecological model simulation of COD levels showed high concentrations, exceeding 4 mg l-1, in the southwest of the Myodo, an area of wastewater discharge, and lower levels, approaching less than 1 mg l-1, closer to the outer part of the bay. Engineering countermeasures to reduce the organic and inorganic material loads from point sources by more than 45% were required to keep the COD levels below 2 mg l-1. 相似文献
415.
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417.
Y. P. Kartavtsev T.-J. Park K. A. Vinnikov V. N. Ivankov S. N. Sharina J.-S. Lee 《Marine Biology》2007,152(4):757-773
Mitochondrial DNA (mtDNA) at Cyt-b gene region was sequenced for six flatfish species (in total nine sequences of at least 1,117 bp) from the Far East of Russia
and compared with other sequences of Pleuronectiformes comprising altogether 34 species and 3 outgroup species (Perciformes).
Analysis of the protein-coding Cyt-b gene revealed a statistically substantiated bias in (T + C):(A + G) content, supporting earlier findings. Values of P-distances, as summarized for different scales of the evolutionary history at Cyt-b gene, revealed a clear pattern of increased nucleotide diversity at four different phylogenetic levels: (1) intraspecies,
(2) intragenus, (3) intrafamily, and (4) intraorder. Scores of average P-distances of the four categories of comparison in flatfishes were (1) 0.46 ± 0.19%, (2) 11.74 ± 2.26%, (3) 17.51 ± 3.13%,
and (4) 25.60 ± 0.42%, respectively (mean ± SE). These data support the concept that speciation in the order Pleuronectiformes,
in most cases, follows a geographic mode through the accumulation of numerous small genetic changes over a long period of
time. A phylogenetic tree for 64 sequences of flatfishes and 3 other fishes belonging to ray-finned fishes (Actinopterigii)
was developed using Cyt-b gene and four different analytical approaches: neighbour-joining (NJ), Bayesian (BA), maximum parsimony (MP), and maximum
likelihood (ML). The analysis revealed a monophyletic origin for the representatives of Pleuronectidae, which is the principal
flatfish family investigated (99% repetition level in our BA analysis). A well supported property of the phylogenetic tree
was the monophyletic placement of all the five flatfish families and the order Pleuronectiformes among other representatives
of ray-finned fishes of the class Actinopterigii. Species identification on per individual basis (barcoding tagging) was generally
high. However, there were taxonomic complications that arose during analysis, and they are discussed. Major outcomes of this
discussion are the necessity of synonymy acceptance for Hippoglossoides elassodon, and H. robustus, and for Pseudopleuronectes yokohamae and P. schrenki. Priority considerations suggest H. elassodon and P. yokohamae as valid species names. 相似文献
418.
The mineralogical and chemical characteristics of As solid phases in arsenic-rich mine tailings from the Nakdong As–Bi mine
in Korea was investigated. The tailings generated from the ore roasting process contained 4.36% of As whereas the concentration
was up to 20.2% in some tailings from the cyanidation process for the Au extraction. Thin indurated layers and other secondary
precipitates had formed at the surfaces of the tailings piles and the As contents of the hardened layers varied from 2.87
to 16.0%. Scorodite and iron arsenate (Fe3AsO7) were the primary As-bearing crystalline minerals. Others such as arsenolamprite, bernardite and titanium oxide arsenate
were also found. The amorphous As–Fe phases often showed framboidal aggregates and gel type textures with desiccation cracks.
Sequential extraction results also showed that 55.7–91.1% of the As in tailings were NH4-oxalate extractable As, further confirmed the predominance of amorphous As–Fe solid phases. When the tailings were equilibrated
with de-ionized water, the solution exhibited extremely acidic conditions (pH 2.01–3.10) and high concentrations of dissolved
As (up to 29.5 mg L−1), indicating high potentials for As to be released during rainfall events. The downstream water was affected by drainage
from tailings and contained 12.7–522 μg L−1 of As. The amorphous As–Fe phases in tailings have not entirely been stabilized through the long term natural weathering
processes. To remediate the environmental harms they had caused, anthropogenic interventions to stabilize or immobilize As
in the tailings pile should be explored. 相似文献
419.
Despite several decades of operations and the increasing importance of water quality monitoring networks, the authorities still rely on experiential insights and subjective judgments in siting water quality monitoring stations. This study proposes an integrated technique which uses a genetic algorithm (GA) and a geographic information system (GIS) for the design of an effective water quality monitoring network in a large river system. In order to develop a design scheme, planning objectives were identified for water quality monitoring networks and corresponding fitness functions were defined using linear combinations of five selection criteria that are critical for developing a monitoring system. The criteria include the representativeness of a river system, compliance with water quality standards, supervision of water use, surveillance of pollution sources and examination of water quality changes. The fitness levels were obtained through a series of calculations of the fitness functions using GIS data. A sensitivity analysis was performed for major parameters such as the numbers of generations, population sizes and probability of crossover and mutation, in order to determine a good fitness level and convergence for optimum solutions. The proposed methodology was applied to the design of water quality monitoring networks in the Nakdong River system, in Korea. The results showed that only 35 out of 110 stations currently in operation coincide with those in the new network design, therefore indicating that the effectiveness of the current monitoring network should be carefully re-examined. From this study, it was concluded that the proposed methodology could be a useful decision support tool for the optimized design of water quality monitoring networks. 相似文献
420.
Identifying the major sources contributing to air pollution is a problem of fundamental importance in developing effective air quality management plans. Multivariate receptor modeling aims to achieve this goal by unfolding the air pollution data into components associated with different sources based on factor analysis models. We analyze the PM10 data obtained from 17 monitoring sites in Seoul to locate the major source regions using multivariate receptor modeling. The model uncertainty caused by the unknown number of sources and identifiability conditions is assessed by posterior probability of each model. The estimated source spatial profiles seem to be consistent with our prior expectation about the PM10 sources in Seoul. 相似文献