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991.
992.
Jukka Matinvesi 《Hydrobiologia》1996,335(3):193-202
Total oxygen deficit occurred regularly during stagnation periods in the deepest part of Lake Kallavesi in the period 1973–1986. The sediment was black and anaerobic during the first sampling in 1987. After beginning of artificial lake oxygenation and efficient purification of waste waters of a paper board mill in 1986 the oxygen deficit decreased gradually and a light brown oxidized uppermost sediment layer appeared and began to thicken. The following changes in the sediment composition were observed during 1987–1996: loss on ignition, total nitrogen and BOD7 concentrations decreased in the uppermost sediment layer (0–2 cm) and BOD7 concentration increased in the next sediment layer beneath (2–10 cm). There were no significant change in phosphorus and iron concentrations.Lake oxygen, total phosphorus and suspended solids concentrations fluctuated in a noticeable degree in Lake Huruslahti depending on waste water input and artificial oxygenation during the years 1980–1993. Oxygen condition was good at times of successful waste water elimination and lake oxygenation while deterioration of either resulted oxygen deficiency as well as increase of total phosphorus and suspended solids concentration. Most of the internal load entered with suspended solids during periods of total oxygen deficiency.An explanation for the findings in Lake Huruslahti could be microbiological. Gas formation inside sediment lift organic material towards top of the sediment and into the water, but after the lake recovery the material retain in the sediment. Also in Lake Kallavesi microbiological gas formation resuspended sediment particles with phosphorus into the overlaying water prior to oxygenation. During oxygenation microbiological processes in uppermost sediment utilize the anaerobic metabolic products, organic acids and methane, and block gas formation. Organic substances remain in the top sediment decomposing gradually in the uppermost layer. 相似文献
993.
Meiofauna of the profundal zone of the northern part of Lake Ladoga as an indicator of pollution 总被引:1,自引:0,他引:1
Jukka Särkkä 《Hydrobiologia》1996,322(1-3):29-38
Benthic meiofauna was sampled at 19 stations, mainly in the northern part of Lake Ladoga, from depths between 13 and 199 m and from types of environment ranging from sheltered areas near pollution sources to less polluted open areas. About 80 taxa were identified, of these 70 to the species level. The greatest numbers of species were oligochaetes (24 species) and harpacticoids (8 species). Certain quantitative ratios of meiofauna were shown to be correlated with environmental data. The species of the oligochaete families Lumbriculidae and Aeolosomatidae and the harpacticoids as a collective group, excluding Canthocamptus staphylinus, were most clearly confined to the less eutrophied environments. The oligochaete species Amphichaeta leydigii, Dero digitata and Tubifex tubifex, the resting stages of Cyclopinae, and Eucyclops serrulatus among the Eucyclopinae were most clearly concentrated in the eutrophicated or polluted environments. The groups of Naididae, Cladocera and Eucyclopinae did not have much value as indicators. Shannon diversity index correlated positively with the total phosphorus content of the water, and number of species decreased with increasing depth. In general, it seems that the pollution tolerance of the meiofauna in a very large lake such as Lake Ladoga is high, presumably due to the effective mixing of water masses. 相似文献
994.
Leif Schulman Kalle Ruokolainen Leo Junikka Ilari E. Sääksjärvi Matti Salo Sanna-Kaisa Juvonen Jukka Salo Mark Higgins 《Biodiversity and Conservation》2007,16(11):3011-3051
Protected areas are crucial for Amazonian nature conservation. Many Amazonian reserves have been selected systematically to
achieve biodiversity representativeness. We review the role natural-scientific understanding has played in reserve selection,
and evaluate the theoretical potential of the existing reserves to cover a complete sample of the species diversity of the
Amazonian rainforest biome. In total, 108 reserves (604,832 km2) are treated as strictly protected and Amazonian; 87 of these can be seen as systematically selected to sample species diversity
(75.3% of total area). Because direct knowledge on all species distributions is unavailable, surrogates have been used to
select reserves: direct information on some species distributions (15 reserves, 14.8% of total area); species distribution
patterns predicted on the basis of conceptual models, mainly the Pleistocene refuge hypothesis, (5/10.3%); environmental units
(46/27.3%); or a combination of distribution patterns and environmental units (21/22.9%). None of these surrogates are reliable:
direct information on species distributions is inadequate; the Pleistocene refuge hypothesis is highly controversial; and
environmental classifications do not capture all relevant ecological variation, and their relevance for species distribution
patterns is undocumented. Hence, Amazonian reserves cannot be safely assumed to capture all Amazonian species. To improve
the situation, transparency and an active dialogue with the scientific community should be integral to conservation planning.
We suggest that the best currently available approach for sampling Amazonian species diversity in reserve selection is to
simultaneously inventory indicator plant species and climatic and geological conditions, and to combine field studies with
remote sensing. 相似文献
995.
The use of spectral fluorescence methods to detect changes in the phytoplankton community 总被引:2,自引:0,他引:2
In vivo fluorescence methods are efficient toolsfor studying the seasonal and spatial dynamics ofphytoplankton. Traditionally
the measurements are madeusing single excitation-emission wavelengthcombination. During a cruise in the Gulf of Riga(Baltic
Sea) we supplemented this technique bymeasuring the spectral fluorescence signal (SFS) andfixed wavelength fluorescence intensities
at theexcitation maxima of main accessory pigments. Thesemethods allowed the rapid collection of quantitativefluorescence
data and chemotaxonomic diagnostics ofthe phytoplankton community. The chlorophylla-specific fluorescence intensities (R)
and thespectral fluorescence fingerprints were analysedtogether with concentrations of chlorophyll a indifferent algal size-groups,
phytoplankton biomass andtaxonomic position. The lower level of R in thesouthern gulf was related to the higher proportion
ofcyanobacteria relative to total biomass and the lowerabundance of small algae. The phycoerythrinfluorescence signal was
obviously due to the largecyanobacteria. The basin-wide shift in the shape ofchlorophyll a excitation spectra was caused bythe
variable proportions of differently pigmentedcyanobacteria, diatoms and cryptomonads.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
996.
Parasitism is a potential mechanism initiating or facilitating ecotypic differentiation and speciation in freshwater fish. While recent studies have begun to explore this question, there are no empirical studies of parasitism in evolutionary replicates of ecotype‐pairs at variable stages of speciation. Such comparative studies of parasitism along continuums of host differentiation are needed as a first step towards testing the role of parasites in ecological speciation. We explored parasitism of whitefish Coregonus lavaretus in four pre‐alpine lakes in Switzerland that hold replicate species radiations of whitefish. We sampled shallow and deep‐spawning ecotypes on their breeding grounds. We found significant and consistent differences in infection between the ecotypes so that the shallow‐spawning fish had more trematode infections, whereas the deepspawning fish had more cestodes. The magnitude of these differences correlated positively with the degree of the genetic differentiation among the ecotypes and negatively with the extent of eutrophication of the lakes. Although the overall diversity of infections was low, some parasite species with potential effects on fish showed marked differences in infection between the ecotypes, suggesting that parasitism may have a role in maintaining ecotype differentiation in this system. Our results also indicate previously unknown habitat segregation of the better differentiated ecotypes, i.e. species, along the depth gradient outside the breeding season. Moreover, oligotrophic lakes tended to have higher parasite species richness and higher abundances of infection, than mesotrophic and eutrophic lakes, suggesting that the history of eutrophication affects parasite diversity. 相似文献
997.