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81.
Diatoms from two macro-tidal mudflats in Chignecto Bay,Upper Bay of Fundy,New Brunswick,Canada 总被引:1,自引:1,他引:0
M.?Trites I.?KaczmarskaEmail author J.M.?Ehrman P.W.?Hicklin J.?Ollerhead 《Hydrobiologia》2005,544(1):299-319
Mudflat research is dispersed among several fields (ecology, sedimentology), each with its own focus and methodology. Consequently, although the volume of mudflat literature is considerable, our understanding of mudflat ecology remains fragmented. For example, little is known about the structure of microbial communities outside Western Europe. Here we present the first North American specific composition and densities of live mudflat diatoms and relate them to properties of their environment on two closely located flats. The two flats (Daniel’s and Buck’s) were similar until the mid–1980s. After this time the biological and sedimentary environment on Buck’s Flats began to change and resulted in a precipitous decline of the keystone invertebrate Corophium volutator (Pallas). The specific diatom composition on each of the two flats examined was still very similar. Tychoplanktonic diatoms were numerically dominant on both flats. The flats differed significantly in the relative contribution of epipelic diatoms, which were about an order of magnitude greater on Buck’s Flats. CCA analysis suggests that very few of these species exist within their optimal habitat. Some of the differences appeared small, but were statistically and biologically significant. Daniel’s Flats sediments had a 30% larger mean grain size, less water and organic carbon compared to Buck’s Flats sediments. Buck’s Flats had more variable depths of the oxygenated layer, often with anoxic inclusions throughout. Daniel’s Flats supported more C. volutator, while Buck’s Flats contained greater densities of diatoms. The importance of preserving environmental conditions (sedimentary and biotic) prevailing on flats such as Danielȁ9s Flat in order to foster populations of Corophium at a level necessary to support foraging migratory shorebirds is also discussed. 相似文献
82.
渤海莱州湾表层沉积物中底栖有孔虫分布特征及其环境意义 总被引:2,自引:0,他引:2
对渤海莱州湾海域240个站位表层沉积物中底栖有孔虫群落进行了分析,共鉴定常见的底栖有孔虫42种。结果表明,莱州湾表层沉积物中底栖有孔虫主要以玻璃质壳为主(平均丰度达70.9%),瓷质壳含量次之,胶结壳含量最低;玻璃质壳占有孔虫全群的百分含量,随水深的增加而增加;从黄河口向外海方向,有孔虫分异度和丰度都逐渐增大。该海域底栖有孔虫平面分布的主要控制因素为盐度和底质沉积物类型,大体可分为两个组合分区,I区为Ammonia beccarii-Quinqueloculina spp.组合,代表盐度较低的近岸海陆过渡浅水环境;II区为Cribrononionsub-incertum-Protelphidium tuberculatum组合,代表盐度较高的远岸内陆架环境。 相似文献
83.
Synopsis We surveyed fish communities and corresponding environmental conditions at three broadly similar coastal sites of eastern
Andros Island, The Bahamas over a summer–winter–summer sequence to assess the relationship between detailed environmental
features and fish species patterns. Environmental variables included covers of various benthic flora components, benthic flora
diversity, floral canopy height, micro-crustacean diversity and density, water temperature, extent of destructive land-use
and extent of invasion by human-introduced exotic terrestrial plants. Correspondence analysis (CA) indicated that spatial
(site) differences in environmental characteristics were greater than temporal (seasonal) differences. Detrended canonical
correspondence analysis (DCCA) was used to assess the strength of relationships between the environmental characteristics
and the distribution patterns of 25 fish species. Environmental features deemed to be most important in influencing fish species
patterns included benthic flora canopy height, extent of invasion by exotic terrestrial plants, cover of Batophora oerstedii, cover of Thalassia testudinum, turf cover, water temperature, micro-crustacean diversity, and micro-crustacean density. Based upon similarities in distribution
patterns, fish species formed four clusters which, ultimately, reflected similarities in species’ feeding habits and preferences
for habitats that likely maximize foraging success. We conclude that fish distribution patterns are related to environmental
characteristics, and that anthropogenic coastal activity, by influencing coastal benthic characteristics, may influence the
distribution and abundances of fish species in coastal habitats. 相似文献
84.
The Ecosystem Approach to Fisheries requires that managers take account of the environmental impacts of fishing. We develop
linked state and pressure indicators that show the impact of bottom-trawling on benthic communities. The state indicator measures
the proportion of an area where benthic invertebrate biomass (B) or production (P) is more than 90% of pristine benthic biomass
(B 0.9) or production (P0.9). The pressure indicator measures the proportion of the area where trawling frequency is sufficiently high to prevent reaching
predicted B0.9 or P0.9. Time to recovery to B0.9 and P0.9 after trawling, depending on the habitat, was estimated using a validated size-based model of the benthic community. Based
on trawling intensity in 2003, 53.5% of the southern North Sea was trawled too frequently for biomass to reach B0.9, and 27.1% was trawled too frequently for production to reach P0.9. As a result of bottom-trawling in 2003, in 56% of the southern North Sea benthic biomass was below B0.9, whereas in 27% of the southern North Sea benthic production was below P0.9. Modeled recovery times were comparable to literature estimates (2.5 to more than 6 years). The advantages of using the area
with an ecological impact of trawling as a pressure indicator are that it is conceptually easy to understand, it responds
quickly to changes in management action, it can be implemented at a relevant scale for fisheries management, and the necessary
effort distribution data are centrally collected. One of this approach’s greatest utilities, therefore, will be to communicate
to policy makers and fishing enterprises the expected medium- to long-term ecological benefits that will accrue if the frequency
of trawling in particular parts of fishing grounds is reduced. 相似文献
85.
Thi Thuy Duong Michel Coste Agnès Feurtet-Mazel Dinh Kim Dang Caroline Gold Young Seuk Park Alain Boudou 《Hydrobiologia》2006,563(1):201-216
The effects of urban pollution from Hanoi city on the benthic diatom communities of the Nhue–Tolich river system were studied
during the 2003 dry season. Benthic diatoms were allowed to grow on glass slides suspended in the water flow for 4 weeks.
To reveal the relationship between water quality and diatom communities, Canonical correspondence analysis (CCA) was used
on data concerning relative abundances of diatom species and environmental variables. Two diatom indices, IPS and DAIpo, were
applied to evaluate water quality in the three rivers. A total of 291 diatom taxa were found in the Red, Nhue and Tolich Rivers.
These were mainly cosmopolitan taxa, with some tropical, subtropical and endemic taxa. The most abundant taxa at the Red site
were Aulacoseira granulata, Achnanthidium minutissimum, Encyonema minutum, Navicula recens and other halophilous taxa such as Nitzschia kurzii, Seminavis strigosa, Entomoneis paludosa, Bacillaria paradoxa. Diatom assemblages at the Tolich site consisted mainly of Nitzschia umbonata, Nitzschia palea and Eolimna minima. Diatom density ranged from 660 to 30,000 cells/cm2. Environmental variables and diatom assemblage composition at all sites were significantly correlated. Two diatom indices
gave similar results and indicate the Tolich River with the lowest values as a highly polluted site. 相似文献
86.
R. Jan Stevenson Steven T. Rier Catherine M. Riseng Richard E. Schultz Michael J. Wiley 《Hydrobiologia》2006,561(1):149-165
Responses of stream algal biomass to nutrient enrichment were studied in two regions where differences in hydrologic variability
cause great differences in herbivory. Around northwestern Kentucky (KY) hydrologic variability constrains invertebrate biomass
and their effects on algae, but hydrologic stability in Michigan (MI) streams permits accrual of high herbivore densities
and herbivory of benthic algae. Multiple indicators of algal biomass and nutrient availability were measured in 104 streams
with repeated sampling at each site over a 2−month period. Many measures of algal biomass and nutrient availability were positively
correlated in both regions, however the amount of variation explained varied with measures of biomass and nutrient concentration
and with region. Indicators of diatom biomass were higher in KY than MI, but were not related to nutrient concentrations in
either region. Chl a and % area of substratum covered by Cladophora were positively correlated to nutrient concentrations in both regions. Cladophora responded significantly more to nutrients in MI than KY. Total phosphorus (TP) and total nitrogen (TN) explained similar
amounts of variation in algal biomass, and not significantly more variation in biomass than dissolved nutrient concentrations.
Low N:P ratios in the benthic algae indicated N as well as P may be limiting their accrual. Most observed responses in benthic
algal biomass occurred in nutrient concentrations between 10 and 30 μg TP l−1 and between 400 and 1000 μg TN l−1. 相似文献
87.
To assess potential risks of human visitation to ecological communities, the immediate effects of human trampling were investigated
experimentally on small invertebrates inhabiting mid-upper intertidal hard bottoms covered by algae. Two different experimental
intensities of trampling (60 and 120 footsteps) and controls (with no trampling) were applied to quadrats 20×20 cm in size
(experimental area), within the two ‘no-entry, no-take’ zones of the Asinara Island MPA (Italy, Mediterranean Sea). One day
after trampling ended, samples of benthic fauna were collected and the animals attributed to macrofaunal and meiofaunal components.
Analyses of variance on the nine most common taxa of macrofauna identified significant higher abundance of bivalves, gammarid
amphipods, polychaetes, isopods, oligochaetes in controls than in trampled plots. For nematodes, polychaetes, ostracods, oligochaetes,
bivalves, acari, caprellid amphipods and tanaids a significant higher abundance of meiofaunal animals was found in controls
than in trampled areas. Although no information on recovery is available, these results suggest that macrofaunal and meiofaunal
taxa are vulnerable to this type of disturbance. 相似文献
88.
Here we summarize results of the EU funded research project STAR concerning the suitability of different organism groups (fish,
benthic invertebrates, macrophytes, diatoms) for monitoring European rivers. In a general way, the suitability of the organism
groups is classified by monitoring type, stress type, river type, temporal scale and taxonomic resolution. For example, although
all organism groups are affected by acidification, the relatively low species richness of fish and macrophytes in small mountain
streams makes these two groups less suitable, and, hence, we argue that benthic diatoms and/or invertebrates may be considered
as more robust indicators. Similar, lines of reasoning are given for a number of stressor and stream types. 相似文献
89.
A Feasibility Study to Monitor the Macroinvertebrate Diversity of the River Nile Using Three Sampling Methods 总被引:2,自引:1,他引:1
The River Nile is one of the world’s major rivers. Its’ catchment in Egypt has a population of 75,000,000. River flow is highly
regulated and there are known discharges of pollutants. 1035 km of the river downstream of the Aswan high dam was studied
to test the hypothesis that representative qualitative samples can be used to estimate macroinvertebrate biodiversity. Benthic
macroinvertebrates are difficult to sample in large rivers and a reliable sampling strategy is required to evaluate their
ecological status. Three methods for sampling have been investigated. Ekman Grab, macrophyte sweep netting and Artificial
Substrate Samplers (ASS) were used to sample 15 sites from Aswan to Cairo between September 2001 and June 2002. Organisms
were identified to species level where possible. Taxon accretion curves indicated that the all taxa present at a site should
be collected using either 15 grab samples, 10 macrophyte samples or 5 ASS. The best time to sample was May–June. The biodiversity
of macroinvertebrates in the Nile was recorded as 50 taxa with values of 7–31 at individual bank-side sites. Mid-stream biodiversity
was much lower (0–19). Lowest biodiversity occurred at sites with known pollution inputs whilst highest occurred at sites
with high levels of sedimentation. A regular programme for biomonitoring is recommended which will allow current status to
be confirmed and future changes detected. 相似文献
90.
The classical athecate dinoflagellate genera (Amphidinium, Gymnodinium, Gyrodinium) have long been recognized to be polyphyletic. Amphidinium sensu lato is the most diverse of all marine benthic dinoflagellate genera; however, following the redefinition of this genus ~100 species remain now of uncertain or unknown generic affiliation. In an effort to improve our taxonomic and phylogenetic understanding of one of these species, namely Amphidinium semilunatum, we re‐investigated organisms from several distant sites around the world using light and scanning electron microscopy and molecular phylogenetic methods. Our results enabled us to describe this species within a new heterotrophic genus, Ankistrodinium. Cells of A. semilunatum were strongly laterally flattened, rounded‐quadrangular to oval in lateral view, and possessed a small asymmetrical epicone. The sulcus was wide and characteristically deeply incised on the hypocone running around the antapex and reaching the dorsal side. The straight acrobase with hook‐shaped end started at the sulcal extension and continued onto the epicone. The molecular phylogenetic results clearly showed that A. semilunatum is a distinct taxon and is only distantly related to species within the genus Amphidinium sensu stricto. The nearest sister group to Ankistrodinium could not be reliably determined. 相似文献