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961.
To check the effect of possible deposition of organic contaminants in northern regions of the Earth due to atmospheric transport snow samples were collected in early March in 6 places in Russia and 4 in Finland including arctic territories. GC‐MS was used as an analytical tool to identify and quantify individual organic compounds belonging to the various classes. As a result more than 250 compounds were detected. The possible presence of more than 100 other priority pollutants from the US EPA list was also screened. 相似文献
962.
Lucina
pectinata is a large tropical clam living deeply burrowed in the black, reducing mud of mangrove swamps. It is known to possess hemoglobin
in the cytoplasmic areas of its bacteriocytes, which harbor sulfide-oxidizing bacteria. The bacteriocytes also possess lysosome-like
microbodies containing either membrane whorls or electron-dense granules in which free heme compounds have been identified.
The cytochemical detection of acid phosphatase and arylsulphatase through EDX (energy-dispersive X-ray) microanalysis strongly
suggests that the bacteriocytes of L.
pectinata contain, in fact, two different types of microbodies. Some of these (devoid of dense granules) possess a variable amount
of lysosomal enzymes and occasionally a limited quantity of iron, which may result from a recycling process of hemoglobin.
Their main function seems to be the digestion of a limited proportion of symbiotic bacteria. They represent genuine secondary
lysosomes with a functionally acidic pH. The second type of microbodies is characterized by dense granules containing sulfur
and iron hemes but no lysosomal enzymes. Their sulfide-oxidizing activity was substantiated by benzyl viologen assay, with
Na2S as a substrate. These microbodies appear to be similar to the sulfide-oxidizing bodies (SOBs) described in the bacteriocytes
of other bivalve species with symbiotic thioautotrophic bacteria; however, their sulfide-oxidizing activity appears to be
non-enzymatic. They are discrete organelles, characterized by a functionally basic pH and pseudoperoxidasic activity, and
have been termed SOBs. Therefore, the bacteriocytes of L.
pectinata possess at the same time functional lysosomes and functional SOBs.
Received: 17 August 2000 / Accepted: 20 December 2000 相似文献
963.
The effects of interactions between coconut products and caffeine on the induction of drug-metabolizing enzyme in Wistar albino rats were studied. Twenty rats were randomly divided into four groups: (Group 1) control received via oral route a placebo (4 mL distilled water). Groups 2–4 were treated for a 14-day period, respectively, with 50 mg caffeine/kg body weight (BW), 50 mg caffeine/kg plus 50 mg coconut water/kg, or 50 mg caffeine/kg plus 50 mg coconut milk/kg in a 4 mL volume via gastric intubation. One day after the after the final exposure, the animals were euthanized by inhalation of an overdose of chloroform. The blood of each rat was collected by cardiac puncture, and the liver of each was harvested and processed to examine several biochemical parameters, including total protein and RNA levels, protein/RNA ratios, and the activities of alanine and aspartate aminotransferases (ALT and AST, respectively). Results showed that while ingestion of coconut milk and coconut water increased the values of protein and protein/RNA ratios, there was a decrease in ALT and AST activities. These effects were opposite to those produced by caffeine alone and may prevent the adverse effects attributed to caffeine. 相似文献
964.
We have developed a new version of the MERGE model, called MERGE-ETL, to analyse the dynamics of endogenous technological learning (ETL) in the energy system. This paper describes the basic formulation of MERGE-ETL, the solving techniques used for this model and some first numerical results in the context of policies designed to mitigate global climate changes. 相似文献
965.
Effects of initial iron corrosion rate on long-term performance of iron permeable reactive barriers: Column experiments and numerical simulation 总被引:2,自引:1,他引:2
Jin suk O Sung-Wook Jeen Robert W. Gillham Lai Gui 《Journal of contaminant hydrology》2009,103(3-4):145-156
Column experiments and numerical simulation were conducted to test the hypothesis that iron material having a high corrosion rate is not beneficial for the long-term performance of iron permeable reactive barriers (PRBs) because of faster passivation of iron and greater porosity loss close to the influent face of the PRBs. Four iron materials (Connelly, Gotthart-Maier, Peerless, and ISPAT) were used for the column experiments, and the changes in reactivity toward cis-dichloroethene (cis-DCE) degradation in the presence of dissolved CaCO3 were evaluated. The experimental results showed that the difference in distribution of the accumulated precipitates, resulting from differences in iron corrosion rate, caused a difference in the migration rate of the cis-DCE profiles and a significant difference in the pattern of passivation, indicating a faster passivation in the region close to the influent end for the material having a higher corrosion rate. For the numerical simulation, the accumulation of secondary minerals and reactivity loss of iron were coupled using an empirically-derived relationship that was incorporated into a multi-component reactive transport model. The simulation results provided a reasonable representation of the evolution of iron reactivity toward cis-DCE treatment and the changes in geochemical conditions for each material, consistent with the observed data. The simulations for long-term performance were also conducted to further test the hypothesis and predict the differences in performance over a period of 40 years under typical groundwater conditions. The predictions showed that the cases of higher iron corrosion rates had earlier cis-DCE breakthrough and more reduction in porosity starting from near the influent face, due to more accumulation of carbonate minerals in that region. Therefore, both the experimental and simulation results appear to support the hypothesis and suggest that reactivity changes of iron materials resulting from evolution of geochemical conditions should be considered in the design of iron PRBs. 相似文献
966.
967.
Effects of land clearing techniques and tillage systems on runoff and soil erosion in a tropical rain forest in Nigeria 总被引:2,自引:0,他引:2
This work reports runoff and soil loss from each of 14 sub-watersheds in a secondary rain forest in south-western Nigeria. The impact of methods of land clearing and post-clearing management on runoff and soil erosion under the secondary forest is evaluated. These data were acquired eighteen years after the deforestation of primary vegetation during the ‘ West bank’ project of the International Institute for Tropical Agriculture (IITA). These data are presented separately for each season; however, statistical analyses for replicates were not conducted due to differences in their past management. Soil erosion was affected by land clearing and tillage methods. The maximum soil erosion was observed on sub-watersheds that were mechanically cleared with tree-pusher/root-rake attachments and tilled conventionally. A high rate of erosion was observed even when graded-channel terraces were constructed to minimize soil erosion. In general there was much less soil erosion on manually cleared than on mechanically cleared sub-watersheds (2.5 t ha−1 yr−1 versus 13.8 t ha−1 yr−1) and from the application of no-tillage methods than from conventionally plowed areas (6.5 t ha−1 yr−1 versus 12.1 t ha−1 yr−1). The data indicate that tillage methods and appropriate management of soils and crops play an important role in soil and water conservation and in decreasing the rate of decline of soil quality. 相似文献
968.
969.
I. A. Romanenko V. A. Romanenkov P. Smith J. U. Smith O. D. Sirotenko N. V. Lisovoi L. K. Shevtsova D. I. Rukhovich P. V. Koroleva 《Regional Environmental Change》2007,7(2):63-77
This study estimates the consequences of climate change on cropland with and without implementation of adaptation measures,
paying special attention to the maintenance of soil organic carbon (C) stocks. We examine the possibility for regional sustainable
agricultural management practice that combines both maintenance and gain in soil carbon level with profit maximization. Future
scenarios of Regional Agricultural Production Systems (RAPS) were constructed for 2000–2070 based on linking the effects of
global climate change, predicted change in productivity parameters for the main agricultural crops, land-use and soil database
parameters. The RAPS were used to examine profitability and feasibility of alternative agricultural scenarios, based on an
economic model. A number of recommendations for decision making were proposed based on an assessment of the efficiency of
adaptation in animal husbandry and in the crop production sector, after analysis of current percentage of perennial grass
in rotation in comparison with future economic scenarios.
Figures in color are available at 相似文献
970.
Reproduction and survival of tawny owls in relation to persistent organic pollutants 总被引:1,自引:0,他引:1
The potential effects of organochlorines (OCs) and brominated flame retardants on reproduction and survival were studied in tawny owls (Strix aluco) in Central Norway over a period of 19 years (1986-2004). Concentrations of 14 OCs and five polybrominated diphenyl ethers (PBDEs) were measured in eggs (n=104), and Principal Component Analysis was used to produce composite measurements of pollutants; i.e. PC1 and PC2, which accounted for 85% of the variation in contaminant concentrations. There was no evidence for adverse associations between pollutants (PC scores) and life-history traits such as clutch size, probability of producing fledglings and survival, when controlling for potentially confounding variables. Moreover, there was no evidence for interactions between pollutants and vole abundance suggesting no synergistic effects of food stress and pollutants on these life-history traits. There was, however, some evidence for a non-linear negative association between p,p'-DDE (1,1-dichloro-2,2-bis (p-chlorophenyl) ethylene) and eggshell thickness. This suggests that the concentrations of pollutants in this ecosystem were too low to affect reproduction and survival in an owl predominantly consuming prey at low trophic levels, but may be sufficient to cause eggshell thinning at the highest concentrations. 相似文献