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41.
A 6-month greenhouse pot trial was performed, aimed at screening appropriate Sesbania species for remediation of Pb/Zn and Cu mine tailings. Performances of young seedlings of four Sesbania species (S. cannabina, S. grandiflora, S. rostrata, and S. sesban) were compared with and without inoculation of rhizobia. Seedlings were planted in two types of tailings amended with garden soil or garden soil mixed with river sediment. The results indicated that inoculated plants generally produced a higher biomass than samples without inoculation. Pb/Zn mine tailings containing rather high concentrations of total and water-soluble Cu, Pb, and Zn were toxic to plant growth compared with Cu mine tailings, according to the growth performance of the four species. Sesbania sesban and S. rostrata showed superior growth performance, compared to the other two species. Thus, they can serve as pioneer species to modify the barren environment, by providing organic matter and essential nutrients such as nitrogen, upon decomposition, in a relatively short period of time. This is especially true for S. rostrata, which is an annual plant that forms both stem and root nodules. However, a longer-term field trial should be conducted to investigate if superior species can beneficially modify the habitat for the growth of subsequent plant communities. 相似文献
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Response of Ceriodaphnia dubia to ionic silver: discrepancies among model predictions, measured concentrations and mortality 总被引:1,自引:0,他引:1
Silver thiosulfate, often a waste product of photoprocessing, is less bioavailable or toxic to aquatic organisms than is ionic silver. We conducted duplicate 48-h Ceriodaphnia dubia tests in reconstituted laboratory water using treatments of 92.7 nM Ag+ with various concentrations of thiosulfate. Expected Ag+ concentrations were generated for thiosulfate treatment levels using MINEQL + chemical equilibrium modeling. Ag+ concentrations in treatments were determined using a novel silicon-based sensor. Based on predicted Ag+ and published 48-h LC50 values for C. dubia, we did not expect to observe adverse effects. Yet, 100% mortality was observed at low thiosulfate treatments, whereas > 85% and > 95% survival was observed at higher thiosulfate treatment levels, respectively. Our results indicate that biotic responses match the sensor-based Ag+ concentrations. However, there is a discrepancy between these empirical results and responses expected to occur with Ag+ concentrations as predicted by MINEQL + chemical modeling. By correlating silicon sensor data with toxicity results obtained from our laboratory, our work clearly relates a specific chemical form (Ag+) to toxicity results. 相似文献
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Phylogeographic structure of false clownfish, Amphiprion ocellaris, explained by sea level changes on the Sunda shelf 总被引:3,自引:0,他引:3
The phylogenetic structure of the anemonefish Amphiprion ocellaris was established based on sequence data generated for the 5′ end of the cytochrome b (cytb) gene at 11 sites throughout Southeast Asia. Considerable genetic structuring was observed throughout the range of
A. ocellaris. The region has a complex geography, with the Sunda shelf having been exposed during the lower sea levels associated with
periods of glaciation. The direction of subsequent flooding of the Sunda shelf, as a direct consequence of the retreating
glacial sheets, can be predicted based on the major river drainage systems in the region. Much of the phylogeographic structure,
including levels of intra-site genetic variation, can be explained in terms of the “seeding” of sites on the Sunda shelf,
by those on the shelf rim, as sea levels rose. We often found surface ocean currents in the region, which should influence
larval dispersal, to be poorly correlated with phylogeographic structure. Several geographically close sites, which appear
to be connected by surface currents, showed significant genetic stratification. We hypothesise that the phylogeographic structure
of A. ocellaris is more reminiscent of the Pleistocene sea level changes than surface currents. The high contribution of sea level changes
to the phylogeographic structure was also supported by several missing haplotypes in the generated spanning network. Cytb
DNA sequences generated for recently recruited A. ocellaris individuals sampled from Singapore indicate that, on a local scale, there is a directional inflow of recruits, which is dependent
on the monsoon seasons. The nature of dispersal and genetic structure of reef fish species found on the Sunda shelf is clearly
complex, and should take into consideration past phylogeographic events.
Received: 13 November 1999 / Accepted: 12 July 2000 相似文献
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