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51.
Mixed-species associations have been described in many vertebrate species, but few behavioral studies have investigated associations
between species from different mammalian orders. Cape ground squirrels (Xerus inauris) are highly social rodents that inhabit burrows with two species of mongoose, but the benefits of these interspecific associations
to ground squirrels remain unresolved. We compared the behavior of squirrels while solitary, with conspecifics, and in the
presence of suricates (Suricata suricatta) and yellow mongooses (Cynictis pencillatus). Squirrels spent less time alert and more time feeding when suricates were present, but increased vigilance in the presence
of yellow mongooses. In a series of mobbing trials with a puff adder (Bitis arietans), a common predator of all three species, Cape ground squirrels were the most active in mobbing the snake. Our results suggest
that Cape ground squirrels benefit from associating with suricates, but not necessarily with yellow mongooses. Both mongoose
species benefit from the burrowing activities of the squirrels for thermoregulation and escape from predators, and a suite
of other organisms may similarly benefit from the habitat modifications by Cape ground squirrels, suggesting they could be
considered ecosystem engineers of the arid and semi-arid regions of southern Africa. Thus, the association between Cape ground
squirrels and suricates appears mutually beneficial, whereas yellow mongooses may merely be commensals of the squirrels. 相似文献
52.
The microphytoplankton assemblages were studied from water samples collected at eight discrete depths in the top 120 m at
five central (open ocean) and four western (shelf/slope region) locations in the Bay of Bengal. The Bay is a low-productive
warm pool regime with poor inorganic nutrient inputs to its intensely stratified surface layer despite the very large riverine
influx. In addition, the prolonged cloud cover has an adverse effect on the top 25–40 m, on primary production, chlorophyll
concentration and phytoplankton assemblages. Microphytoplankton were the most abundant in the northern area of the Bay. A
total of 153 phytoplankton species were identified during this study. The most abundant species (at least 1,800 individual
cells belonging to a given species or ≥2% of the total counts of identified specimens) during this study were: Thalassiothrix longissima, Thalassiothrix fauenfeldii, Rhizosolenia styliformis, Nitzschia angularis, Thalassionema nitzschioides, Coscinodiscus radiatus, Chaetoceros eibenii, Skeletonema costatum, Coscinodiscus concinnus and Chaetoceros coarctatus. Similarly, there were 20 moderately abundant (≥0.5 but <2%) species. Thirty-three of the least abundant species (<0.5%)
occurred at one station. Diatom species, T. fauenfeldii and T. longissima were ubiquitous in the study area. The exclusive occurrence of S. costatum in the northernmost stations suggests that it proliferates only in the low-salinity regions with adequate silica from the
land inputs. Abundance of pennate diatoms was higher in the open Bay compared to that of centric diatoms in the more productive
northern locations and the western Bay. There appears to be a basic difference between near shore flora and offshore flora.
This first analysis of phytoplankton assemblages from the offshore Bay suggests that while there is predominance of only a
few species, the Bay harbors very diverse diatom communities that seem to be syntrophic, non-competitive and co-habiting in
the generally low nutrient, stratified surface waters. 相似文献
53.
Mangrove forests and seagrass beds frequently occur as adjacent habitats in the temperate waters of southeastern Australia.
At low tide when fish cannot occupy mangroves they might utilise adjacent habitats, including seagrass. We first sampled small
fish from seagrass beds close to and far from mangroves in the Pittwater estuary, NSW, Australia. Seagrass beds close to mangroves
had a greater density of fish species than beds far from mangroves (close: mean 16.0 species net−1, SE 1.0; far: 13.2, 1.3; P < 0.05). In particular, juvenile fish were in greater densities near to than far from mangroves (close: 5.3, 0.4; far: 3.1,
0.4; P < 0.05). We then sampled the mangrove forests during the high tide and seagrass beds during the low tide, in beds along a
continuum of distances from mangroves. Multivariate analysis showed that fish assemblages differed with distance from mangroves,
and the differences were attributed to the composition of the fish assemblage (i.e. presence/absence of fish species), not
the abundances of individual species. In particular, fish that utilise mangrove forests at high tide were found in greater
species densities and species richness in seagrass nearer to mangroves. A negative relationship was found between the density
of mangrove-utilising fish species and the distance of the bed from mangroves (R
2 = 0.37, P < 0.05). This confirms the important connectivity between mangroves and seagrass for fish in temperate Australian waters. 相似文献
54.
Tagungsakündigungen
Rückst?nde und Kontaminanten in Lebensmitteln 29. und 30. Oktober 2002, Atrium Hotel, Mainz 相似文献55.
Elisabeth Görge Sebastian Brandt Dietrich Werner 《Environmental science and pollution research international》1994,1(4):229-233
The fate of the explosive 2,4,6-TNT in plants is of major interest. Therefore, a method was developed to analyse TNT and derivatives in plant tissue. The method was utilized to investigate the uptake and metabolism of TNT inMedicago sativa andAllium schoenoprasum grown in hydroponic cultures containing TNT levels of 0.1 to 10 mg/1. Detectable concentrations of nitrotoluenes were significantly higher inAllium schoenoprasum than inMedicago sativa. The uptake of TNT in plants was directly related to the initial TNT level. The principal nitroaromatic components in roots and shoots of both plant species were identified as 4-ADNT and 2-ADNT in equal amounts, with substantially less TNT. 相似文献
56.
B. Brandt 《Die Naturwissenschaften》1922,10(28):615-616
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