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701.
Pei ZG Shan XQ Liu T Xie YN Wen B Zhang S Khan SU 《Environmental pollution (Barking, Essex : 1987)》2007,147(3):764-770
The effect of lead on the sorption of 2,4,6-trichlorophenol (2,4,6-TCP) on soil and peat was investigated using a batch equilibration method. Lead markedly diminished the sorption of 2,4,6-TCP, and 2,4,6-TCP had little effect on lead sorption. Peat was a more effective adsorbent for 2,4,6-TCP than soil. The desorption hysteresis of 2,4,6-TCP verified the presence of high-energy sorption sites. Mechanisms of lead suppression effect on the 2,4,6-TCP sorption included the following: Firstly, lead accelerated the aggregation of colloids, the aggregates covered the surface in part and shrunk the pore sizes of the adsorbents, hence decreased the sorption of 2,4,6-TCP. Secondly, X-ray absorption and Fourier transform infrared spectroscopy study suggested that lead competed with 2,4,6-TCP for carboxylic, phenolic and Si-OH groups of organic matter and clay minerals. Such competition was partly responsible for the overall suppression effect of lead on the sorption of 2,4,6-TCP. 相似文献
702.
The accurate predictions of ground ozone concentrations are required for proper management, control, and making public warning strategies. Due to the difficulties in handling phenomenological models that are based on complex chemical reactions of ozone production, neural network models gained popularity in the last decade. These models also have some limitations due to problems of overfitting, local minima, and tuning of network parameters. In this study, the predictions of daily maximum ozone concentrations are attempted using support vector machines (SVMs). The comparison between the accuracy of SVM and neural network predictions is performed to evaluate their performance. For this, the daily maximum ozone concentration data observed during 2002–2004 at a site in Delhi is utilized. The models are developed using the available meteorological parameters. The results indicated the promising performance of SVM over neural networks in predicting daily maximum ozone concentrations. 相似文献
703.
Monitoring results for organochlorine pesticides in soil and water from selected obsolete pesticide stores in Pakistan 总被引:1,自引:0,他引:1
Karam Ahad Ashiq Mohammad Hizbullah Khan Iftikhar Ahmad Yousaf Hayat 《Environmental monitoring and assessment》2010,162(1-4):191-199
Seasonal changes in micromineral and macromineral concentrations in tissues of shrimp (Parapenaus longirostris) from Marmara Sea were measured for a 1-year period by using inductively coupled plasma mass spectrometer. The contents of investigated minerals in shrimp were found to be in the range of 0.374–0.716 mg/kg for Hg, 0.526–1.286 mg/kg for Se, 0.007–0.098 mg/kg for Cd, 0.197–0.230 mg/kg for Pb, 5.194–7.600 mg/kg for Cu, 11.090–17.707 mg/kg for Zn, 22.128–38.850 mg/kg for Al, 61.769–88.437 mg/kg for Fe, 0.262–0.368 mg/kg for As, 0.081–0.249 mg/kg for Co, 0.850–1.459 mg/kg for Mn, 0.316–0.507 mg/kg for Ni, 0.032–0.107 mg/kg for Sn, 1.262–1.502 mg/kg for Cr, 2,813.770–3,317.819 mg/kg for Na, 3,702.230–4,479.648 mg/kg for K, 495.782–650.280 mg/kg for Mg, 790.407–1,016.112 mg/kg for Ca, 2,685.873–3,657.658 mg/kg for P, and 0.454–0.942 mg/kg for I. The levels of Hg found in autumn were higher than maximum levels proposed by the European legislation. 相似文献
704.
Different multivariate statistical analysis such as, cluster analysis, principal component analysis, and multidimensional
scale plot were employed to evaluate the trophic status of water quality for four monitoring stations. The present study was
carried out to determine the physicochemical parameters of water and sediment characteristics of Pondicherry mangroves—southeast
coast of India, during September 2008–December 2010. Seasonal variations of different parameters investigated were as follows:
salinity (10.26–35.20 psu), dissolved oxygen (3.71–5.33 mg/L), pH (7.05–8.36), electrical conductivity (26.41–41.33 ms−1), sulfide (1.98–40.43 mg/L), sediment texture sand (39.54–87.31%), silt (9.89–32.97%), clay (3.06–31.20%), and organic matter
(0.94–4.64%). pH, temperature, salinity, sand, silt, clay, and organic matter indicated a correlation at P < 0.01. CA grouped the four seasons in to four groups (pre-monsoon, monsoon, post-monsoon, summer) and the sampling sites
in to three groups. PCA identified the spatial and temporal characteristics of trophic stations and showed that the water
quality was worse in stations 3 and 4 in the Pondicherry mangroves. 相似文献
705.
The oxidation of sulphidic mine tailings and consequent acid generation poses challenges for the environment. Accurate and
precise analysis of sulphur content is necessary for impact assessment and management of mine tailings. Here, the authors
aim at developing a rapid and easy digestion procedure, which may analyse and measure the total amount of sulphur in mine
tailings by using inductively coupled plasma. For evaluating effects of several variables, the researchers used a univariate
(analysis of variance (ANOVA)) strategy and considered factors such as composition of the acid mixture, heating time, and
refluxing device to optimize the performance. To do the experiment, the researchers have used two certified reference materials
(KZK-1 and RTS-2) and samples of tailings from Musselwhite mine. ANOVA result shows that heating time is the most influencing
factor on acid digestion of the reference materials whereas in case of a digestion of tailings sample, hydrochloric acid proved
to be the most significant parameter. Satisfactory results between the measured and referenced values are found for all experiments.
It is found that the aqua regia (1 ml HNO3 + 3 ml HCl) digestion of 0.1 g of samples after only 40 min of heating at 95°C produced fast, safe, and accurate analytical
results with a recovery of 97% for the selected reference materials. 相似文献
706.
Shabnam Shahida Akbar Ali Muhammad Haleem Khan Muhammad Mufazzal Saeed 《Environmental monitoring and assessment》2013,185(2):1613-1626
In this work, spectrophotometer was used as a detector for the determination of uranium from water, biological, and ore samples with a flow injection system coupled with solid phase extraction. In order to promote the online preconcentration of uranium, a minicolumn packed with XAD-4 resin impregnated with nalidixic acid was utilized. The system operation was based on U(VI) ion retention at pH 6 in the minicolumn at flow rate of 15.2 mL min?1. The uranium complex was removed from the resin by 0.1 mol dm?3 HCl at flow rate of 3.2 mL min?1 and was mixed with arsenazo III solution (0.05 % solution in 0.1 mol dm?3 HCl, 3.2 mL min?1) and driven to flow through cell of spectrophotometer where its absorbance was measured at 651 nm. The influence of chemical (pH and HCl (as eluent and reagent medium) concentration) and flow (sample and eluent flow rate and preconcentration time) parameters that could affect the performance of the system as well as the possible interferents was investigated. At the optimum conditions for 60 s preconcentration time (15.2 mL of sample volume), the method presented a detection limit of 1.1 μg L?1, a relative standard deviation (RSD) of 0.8 % at 100 μg L?1, enrichment factor of 30, and a sample throughput of 42 h?1, whereas for 300 s of the preconcentration time (76 mL of sample volume), a detection limit of 0.22 μg L?1, a RSD of 1.32 % at 10 μg L?1, enrichment factor of 150, and a sampling frequency of 11 h?1 were reported. 相似文献
707.
Raquibul Alam Julie Q. Shang Adnan Hossain Khan 《Environmental monitoring and assessment》2017,189(4):193
The performance of electroflotation (EF) is strongly influenced by the size of O2 and H2 bubbles. Therefore, in this study, the bubble sizes are measured in a lab-scale EF cell using a high-speed camera. The mean bubble size is found to vary in the range of 32.7–68.6 μm under different operating conditions. This study shows that the electrode material, current density, water pH, ionic strength, and frother (Tennafroth 250) concentration are important factors in controlling the bubble size. Furthermore, four mathematical distributions (normal, log-normal, Weibull, and gamma distributions) are fitted to the experimental data, among which the log-normal distribution is found to be the best fit based on the lower Anderson-Darling (AD) value. 相似文献
708.
Amin U. Khan 《Environmental monitoring and assessment》2010,168(1-4):121-131
This paper provides a framework for the managers to devise means to protect, restore, and maintain the remaining bi-species groves for sustainable management of fragile arid land ecosystem. At the moment, there is no information available about the structural and functional ecology of these dwindling remnants. The selection criteria for the classification of the groves are based on understanding the positive association between the two species, Prosopis cineraria and Salvadora oleoides, in terms of spatial pattern and morphological features. It was achieved by highlighting the attributes of the benchmark grove and classification of other groves in reference to it. The results clearly show that positive association in the groves is due to differences in the growth strategies of the two species in terms of above- and belowground biomass allocation and architecture. Most of the groves are in various stages of degradation, and anthropogenic interferences are the major determinant linked with the declining status of the groves. These activities affect the complimentary attributes of the bi-species groves, thus disturbing the characteristic structural features which contributed to the stability of this fragile landscape. 相似文献
709.
An assessment of air quality in the vicinity of a selected school has been carried out by monitoring the concentrations of primary pollutants. The results has shown that during the school hours, the measured pollutants emitted from the cars next to the selected school, such as CO and NO(2), are always under the allowable limits for Kuwaiti air quality standards. On the other hand, the concentrations of non methane hydrocarbon pollutant (nm-HC), some of which are considered to be cancergenic, are found to be above the Kuwaiti standard most of the times. A traffic counter is used to record the number of cars in the main road next to the school in 15 min intervals for 10 days during the monitoring period for air quality. Statistical analysis is performed to develop a relation for prediction of the necessary reduction in traffic, based on CO concentrations, during morning and afternoon periods on working days. A computer dispersion model (CALINE4) is also used to assess the CO concentrations based on recorded flow of traffic and emission inventory with the prevailing meteorological conditions existed at the specified time. After the validation of model, different scenarios have been evaluated to provide an acceptable solution to resolve the traffic congestion problem near the schools in the early morning hours with substantial reduction in pollution levels. The optimal solution for CO concentration reduction by managing smooth traffic flow is to reduce the traffic intensity by half in early morning and afternoon rush hours. The results of the predicted CO concentration in the vicinity of the school for the model and the statistical analysis has shown reduction of 30% and 42% respectively, for approximately 50% decrease in the car use. On the other hand the predicted CO concentration for the model and the statistics reached 24% and 33% respectively when 50% of students opted for buses instead of using private cars. 相似文献
710.
Organic matter content of sediments in continental shelf area of southeast coast of India 总被引:1,自引:0,他引:1
Syed Ajmal Khan K. G. Mohamed Thameemul Ansari P. Somasundharanair Lyla 《Environmental monitoring and assessment》2012,184(12):7247-7256
Total organic matter (TOM) content of sediment samples collected from various depths of continental shelf region of the southeast coast of India varied from 0.19% to 7.73%. Higher TOM content and lower median particle diameter could be attributed to the influence of higher riverine flow. Higher values were observed at 100?m depth and above (average 5.29%) and lower values in shallower depths below 100?m (average 3.07%). In the Principal Coordinate Analysis (PCO), the first two axes explained about 83.1% of the total variability. The direction of the vector representing total organic matter was towards 150?m depth. In the Canonical Analysis of Principal Coordinates (CAP) done to confirm the above pattern, the canonical correlation value obtained for the first axis was high (0.9999). The same for the second axis was 0.9995. The direction of the axis representing TOM in this analysis was towards the 100?m depth truly reflecting higher TOM level recorded here (average TOM at 100?m depth—5.81% and at 150?m depth—5.33%). The percentage of samples allocated to the correct group in CAP was 91.67% (33 out of the 36 samples). As the allocation success of samples is substantially greater around 92%, the CAP is explaining greater percentage of variability of TOM than PCO and was found to be quite useful for studies of this nature. 相似文献