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991.
Distribution and availability of potentially toxic metals in soil in central area of Belgrade,Serbia 总被引:1,自引:0,他引:1
Rabia Ahmed Ghariani Ivan Gržetić Mališa Antić Snežana Nikolić Mandić 《Environmental Chemistry Letters》2010,8(3):261-269
Belgrade, capital city of Serbia, has over 1,600,000 inhabitants and over 400,000 vehicles trafficking every day on its streets.
The investigation of soil pollution was performed by sequential extraction analysis to investigate the availability of potentially
toxic metals (Zn, Cd, Pb, Co, Ni, Cu, Cr and Mn) under different oxidation and pH conditions. All investigated metals were
mainly extracted from soils with neutral or acidic extractants. Serious pollution was observed along roads and streets with
high traffic frequency, but Pb and Ni pollution was the highest since their concentrations exceed both soil Serbian standard
and Canadian guidance values and is characteristic for all investigated sites. Cd, Cu, Cr and Zn concentrations are moderately
high since they are between Canadian guideline and Serbian standard. 相似文献
992.
Photochemical reaction of nitro-polycyclic aromatic hydrocarbons: effect by solvent and structure 总被引:1,自引:0,他引:1
Stewart G Smith K Chornes A Harris T Honeysucker T Dasary SR Yu H 《Environmental Chemistry Letters》2010,8(4):301-306
Photochemical degradation of 1-nitropyrene, 2-nitrofluorene, 2,7-dinitrofluorene, 6-nitrochrysene, 3-nitrofluoranthene, 5-nitroacenaphthene,
and 9-nitroanthracene was examined in CHCl3, CH2Cl2, DMF, DMF/H2O (80/20), CH3CN, or CH3CN/H2O (80/20). The degradation mostly follows the first order kinetics; but a few follow second order kinetics or undergo self-catalysis.
The photodegradation rates follow the order: CHCl3 > CH2Cl2 > DMF > DMF/H2O > CH3CN > CH3CN/H2O. DMF is an exceptional solvent because three of the seven compounds undergo self-catalytic reaction. 9-Nitroanthracene,
which has a perpendicular nitro group, is the fastest, while the more compact 1-nitropyrene and 3-nitrofluoranthene are the
slowest degrading compounds. 相似文献
993.
J. Carneiro L. M. Cardenas D. J. Hatch H. Trindade D. Scholefield C. D. Clegg P. Hobbs 《Environmental Chemistry Letters》2010,8(3):237-246
Nitrous oxide (N2O) affects climate change as a greenhouse gas and indirectly contributes to stratospheric ozone depletion. The main source
of N2O in soils is denitrification which requires high soil moisture, carbon and nitrate. Nitrification inhibitors can be used
to mitigate emissions of N2O from soils. In Portugal, fertilisers are often applied when soils are still relatively warm and moist conditions conducive
to denitrification. A Portuguese arable soil was inhibited with dicyandiamide, a nitrification inhibitor and the effect on
soil microbiological activity and composition was determined after 46 days. Soils were then incubated and received carbon
and ammonium under high soil water conditions and mineral N and N2O fluxes were measured during 22 days. We found that dicyandiamide decreased microbial populations and activity, but did not
alter composition. Pre-conditioning of the soil with dicyandiamide was 80% more effective in reducing fluxes of N2O than simultaneous application with fertiliser. 相似文献
994.
Caio F. Gromboni George L. Donati Wladiana O. Matos Eduardo F. A. Neves Ana Rita A. Nogueira Joaquim A. Nóbrega 《Environmental Chemistry Letters》2010,8(1):73-77
Efficiency of metabisulfite and a commercial steel wool as reducing agents in the removal of Cr(VI) from wastewaters was evaluated.
Chromium(VI) was converted to Cr(III), precipitated with NaOH, and removed by filtration. A reduction of more than 1.0 × 105 and 4.0 × 105 fold in total Cr and the Cr(VI) concentrations, respectively, was observed by employing steel wool masses as low as 0.4420 g
to 30-mL solutions of wastewater. Chromium(III) hydroxide obtained after the treatment was recycled and used as marker in
cattle nutrition studies. The liquid residue obtained after the treatment was reused as precipitation agent replacing NaOH. 相似文献
995.
A surfactant mediated cloud point extraction (CPE) procedure has been developed to remove color from wastewater containing
malachite green using Triton X-100 as non-ionic surfactant. The effects of the concentration of the surfactant, temperature
and salt concentration on the different concentrations of dye have been studied and optimum conditions were obtained for the
removal of malachite green. The concentration of malachite green in the dilute phase was measured using UV–Vis spectrophotometer.
It was found that the separation of phases was complete and the recovery of malachite green was very effective in the presence
of NaCl as an electrolyte. The results showed that up to 500 ppm of malachite green can quantitatively be removed (>95%) by
CPE procedure in a single extraction using optimum conditions. 相似文献
996.
Davide Vione Daniele Bagnus Valter Maurino Claudio Minero 《Environmental Chemistry Letters》2010,8(2):193-198
We measured the formation rate and the steady-state concentration of hydroxyl radicals and of singlet oxygen upon irradiation
of lake water. There is controversy about the importance of singlet oxygen in the environmental photochemistry, but here we
show that the steady-state concentration of 1O2 under irradiation can be higher by about two orders of magnitude compared to the hydroxyl radical. The higher occurrence
of singlet oxygen in surface waters is mainly due to a higher rate of formation, because the transformation rate constants
of 1O2 (collision with the solvent) and of ·OH (reaction with dissolved compounds) are comparable. 相似文献
997.
We studied the removal mechanism and affecting factors of Fe2+-based replacement–precipitation process for treating CuEDTA-containing wastewaters. Since Fe2+ was easily oxidized to Fe3+ in the presence of oxygen, the chelated copper was removed by the synergetic effect of Fe3+ replacement and NaOH precipitation. Our experiments showed that the copper removal efficiency was considerably dependant
on pH conditions of the solution and molar ratio of Fe2+/Cu2+. 相似文献
998.
Alžbeta Jarošová Jiří Harazim Lenka Krátká Doubravka Kolenčíková 《Environmental Chemistry Letters》2010,8(4):387-391
Phthalates are animal carcinogens and may cause death or tissue deformities. Samples of feedstuffs collected in 2005 and 2006
from industrial feed manufacturers in the Czech Republic were analysed for contamination with phthalic acid esters (PAEs),
specifically di-2-ethylhexyl phthalate (DEHP) and di-n-butyl phthalate (DBP). Samples of feed additives, premixes and raw materials were collected (year 2005, n = 26). For soybean oil, the total volume of phthalates measured (DBP + DEHP) reached a level of 131.42 mg kg−1; for rapeseed oil, fish meal and animal fats, the levels measured were 15.00, 7.96 and 58.87 mg kg−1, respectively. The lowest level of DBP + DEHP was found in corn (2.03 mg kg−1). Since phthalates were detected, samples of feed additives (n = 28) and raw materials (n = 28) were collected again in 2006. The highest levels of DBP + DEHP were found in raw materials containing fat. Phthalate
levels in rapeseed oil samples ranged from 1.38 to 32.40 mg kg−1 DBP + DEHP. For feed additives, contamination levels in vitamins and amino acids ranged from 0.06 to 3.15 and 1.76 to 4.52 mg kg−1 DBP + DEHP, respectively. Here, we show that the levels of PAEs found in cereals such as wheat, barley and corn may be regarded
as being alarmingly high, because cereals make up the largest proportion of compound feed of farm animals. 相似文献
999.
Marco Ghisalberti 《Environmental Fluid Mechanics》2010,10(3):329-343
Obstructed shear flows (i.e. those over permeable media) are common in the environment. An archetypal example, flow over a
submerged vegetation canopy, is investigated here. Like any flow through complex geometry, canopy flows are characterised
by strong spatial gradients. The focus of this experimental study is the three-dimensionality of aquatic canopy flow, in particular
that of the coherent interfacial vortices that govern mixing into and out of the canopy. It is shown here that the vortices
have a finite lateral scale that is comparable to their vertical scale; both are of the order of the drag length scale of
the canopy, (C
D
a)−1, where a is the frontal area density and C
D
is a bulk drag coefficient. The finite lateral extent of the vortices generates strong lateral hydrodynamic gradients, both
instantaneously and in the long-term. The instantaneous gradients, which can contribute greatly to the dispersion of dissolved
and particulate species, are far more pronounced. Finally, the potential for canopies to generate differential roughness secondary
circulation is examined. In the consideration of vertical scalar transport, this circulation can be of the same order as turbulent
diffusion. 相似文献
1000.
Photo-polymerization of triclosan in aqueous solution induced by ultraviolet radiation 总被引:1,自引:0,他引:1
The formation of 2,8-dichlorodibenzo-p-dioxin and other harmful degradation products in the photo-degradation process of triclosan is of increasing concern. Here we worked on the identification of polymerized products at high triclosan concentration and on the mechanism of photoreaction. Five dimmers and two trimers of triclosan were detected by liquid chromatography-mass spectrum analysis. 2,8-dichlorodibenzo-p-dioxin was also identified by comparing with an authentic standard. Relatively low pH and high concentration favored the polymerization of triclosan. Three main routes of photoreaction were postulated, namely dechlorination, ring closure and polymerization. 相似文献