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161.
162.
163.
Host-plant specialization by a non-herbivorous amphipod: advantages for the amphipod and costs for the seaweed 总被引:5,自引:0,他引:5
Studies of factors affecting host plant specialization by herbivores commonly highlight the value of the plant as both food
and habitat, but often cannot distinguish the relative importance of these plant traits. A different approach is to study
non-herbivorous animals that specialize on particular plants but do not feed on tissue from these plants. Such animals will
not be affected directly by the nutritional, chemical, or morphological traits that determine the value of the plant as a
food. This study reports on a filter-feeding amphipod, Ericthoniusbrasiliensis, that lives in domiciles it constructs by curling terminal segments of the green, calcified, and chemically defended seaweed
Halimedatuna. We examined the temporal (1850s–1990s) and spatial (Caribbean, Mediterranean, and Pacific regions) scale of the association,
the factors that may select for specialization on H. tuna, and the effect of the amphipod on growth of its host. Sampling along 125 km of coral reefs in the Florida Keys (USA) indicated
that almost all populations of H. tuna had been colonized by this amphipod. Infested plants occurred on nine of ten reefs that supported H. tuna populations, with between 8 and 75% of the plants on those reefs colonized by the amphipod. For infested plants, 2–23% of
all segments on each plant had been curled by the amphipod. Common co-occurring congeners of H. tuna (H. opuntia and H. goreaui) were never used for domicile construction. A survey of 1498 Halimeda specimens collected during the last 140 years and archived in the U.S. National Museum of Natural History (Smithsonian Institution,
Washington, D.C.) indicated that the association has existed for >100 years and occurs throughout the Caribbean region, never
in the Indo-Pacific or Mediterranean, and only on H. tuna. Predation by fishes could select for amphipod specialization on H. tuna. Laboratory experiments demonstrated that amphipods inhabiting curled segments of H. tuna were relatively immune from fish predation while those on the exterior surface of the plant or in open water were rapidly
eaten. Segments of H. tuna are large enough to provide full protection from predators, while those of the co-occurring congeners H. goreaui and H. opuntia are of a size that may provide only partial protection. Experimental addition of E. brasiliensis to H. tuna plants in the field significantly decreased segment accumulation on infested relative to uninfested control plants. Whether
this negative effect was a direct or indirect consequence of amphipod occupancy is unclear. Rolling plant portions into domiciles
could directly decrease host growth by increasing shading and decreasing exposure of plant surface area to water column nutrient
flux. Amphipod occupancy could indirectly slow net host growth if fishes selectively feed on plant sections occupied by amphipods.
Underwater video showed that herbivorous fishes did not graze infested plants more than uninfested plants, but small predatory
fishes did prefer feeding from infested plants. These non-herbivorous fishes may slow host growth by damaging the terminal
meristematic tissues of plants during attacks on amphipods. This study demonstrates that habitat specialists can negatively
impact hosts without consuming them and that specialization on a plant can occur due to its habitat value alone (as opposed
to its value as a food).
Received: 24 March 1998 / Accepted: 1 November 1998 相似文献
164.
The haplochromine cichlid fish communities of the rocky habitats of Lake Malawi are highly diverse; however, many species
live side by side with apparently very similar resource requirements. There is a long-standing debate concerning whether these
species partition their resources on a finer scale than has been previously reported or if species that are truly ecologically
indistinguishable can coexist. A field study of food resource use was conducted to determine whether coexisting species segregate
their diet and foraging sites. Significant differences between species were found, yet considerable inter-specific resource
use overlap was commonplace. The data indicate that these cichlid species coexist both with and without niche differentiation.
We propose that alternatives to niche differentiation should be considered to explain how many species coexist in Lake Malawi
cichlid communities.
Received: 5 October 1998 / Accepted: 30 June 1999 相似文献
165.
We studied genetic drift of mitochondrial DNA (mtDNA) haplotype frequencies in a natural population of red drum (Sciaenops ocellatus) from the northern Gulf of Mexico (Gulf). The amount of genetic drift observed across temporally adjacent year classes (1986–89) was used to estimate variance effective (female) population size (Nef). Nef was estimated to be 14 308 and the ratio of female effective size to adult female census size was approximately 0.004, which is among the lowest value reported for vertebrate animals. Low effective size relative to census size among red drum in the northern Gulf may result from yearly fluctuations in the number of breeding females, high variance in female reproductive success, or both. Despite low genetic effective size relative to census size, the genetic effective population size of red drum in the northern Gulf appears sufficiently large to preclude potentially deleterious effects of inbreeding. 相似文献
166.
167.
T. R. McClanahan V. Hendrick M. J. Rodrigues N. V. C. Polunin 《Coral reefs (Online)》1999,18(3):195-203
The consequences of macroalgal overgrowth on reef fishes and means to reverse this condition have been little explored. An
experimental reduction of macroalgae was conducted at a site in the Watamu Marine National Park in Kenya, where a documented
increase in macroalgal cover has occurred over the last nine years. In four experimental 10 m by 10 m plots, macroalgae were
greatly reduced (fleshy algal cover reduced by 84%) by scrubbing and shearing, while four similar plots acted as controls.
The numerical abundance in all fish groups except wrasses and macroalgal-feeding parrotfishes (species in the genera Calotomus and Leptoscarus) increased in experimental algal reduction plots. Algal (Sargassum) and seagrass (Thalassia) assays, susceptible to scraping and excavating parrotfishes, were bitten more frequently in the algal reduction plots one
month after the manipulation. Further, surgeonfish (Acanthurus leucosternon and A. nigrofuscus) foraging intensity increased in these algal reduction plots. The abundance of triggerfishes increased significantly in experimental
plots relative to control plots, but densities remained low, and an index of sea urchin predation using tethered juvenile
and adult Echinometra mathaei showed no differences between treatments following macroalgal reduction. Dominance of reefs by macrofleshy algae appears
to reduce the abundance of fishes, mostly herbivores and their rates of herbivory, but also other groups such as predators
of invertebrates (triggerfishes, butterflyfishes and angelfishes).
Accepted: 2 February 1999 相似文献
168.
In a study of the fishes of the Euphrates River (Persian Gulf basin) three species of Squalius belonging to the cephalus-group were found: The Tohma population was identified as S. seyhanensis and the Merzimen and Hilvan populations as S. berak. The comparison of 28 metric and 5 meristic parameters and morphological characters showed that the populations of the northern Euphrates River drainages are distinct and belong to a hitherto unnamed species. We describe it here as Squalius semae sp. n.
http://www.zoobank.org/urn:lsid:zoobank.org:pub:D195B69C-C6CB-4DEB-B85D-5B695F917CE5 相似文献
169.
Habitat segregation and cryptic adaptation of species of Periophthalmus (Gobioidei: Gobiidae) 下载免费PDF全文
G. Polgar S. Zaccara M. Babbucci F. Fonzi C. M. Antognazza N. Ishak Z. Sulaiman G. Crosa 《Journal of fish biology》2017,90(5):1926-1943
A study was conducted on the habitat distribution of four sympatric species of Periophthalmus (the silver‐lined mudskipper Periophthalmus argentilineatus, the slender mudskipper Periophthalmus gracilis, the kalolo mudskipper Periophthalmus kalolo and the Malacca mudskipper Periophthalmus malaccensis) from northern Sulawesi. Molecular phylogenetic reconstructions based on one mtDNA marker (16S) were used to validate the morphological taxa, identifying five molecular clades. Periophthalmus argentilineatus includes two molecular species, which are named Periophthalmus argentilineatus clades F and K. Multivariate direct gradient analysis show that these species form three distinct ecological guilds, with the two molecular species occurring in different guilds. Periophthalmus clade F is ecologically eurytypic; Periophthalmus clade K and P. kalolo are prevalent in ecosystems isolated by strong oceanic currents and at shorter distances from the sea; P. gracilis plus P. malaccensis are prevalent in ecosystems connected by shallow coastal waters, in vegetated habitats at larger distances from the sea. This indicates for the first time that mudskipper species exhibit a range of adaptations to semiterrestrialism not only within genera, but even within morphospecies, delineating a much more complex adaptive scenario than previously assumed. 相似文献
170.
The composition of the larval fish assemblage in the sound‐scattering layer of the continental shelf waters off the coast of south‐eastern Brazil (12 and 22° S), a research project that is part of the Brazilian programme Avaliação do Potencial Sustentável de Recursos Vivos na Zona Econômica Exclusiva (REVIZEE), is described. Samples were collected during daylight hours and at dusk at five oceanographic stations in the winter of 1999 using an Isaacs‐Kidd Midwater Trawl (IKMT). The oceanographic stations were chosen based on the detection of plankton layers by acoustic observation. A total of 2192 larval fish were identified, comprising 52 families and 62 species. Maurolicus stehmanni (Sternoptychidae) was the most abundant species found within the study area, comprising 18·5% of all identified larvae, followed by Psilotris celsus (Gobiidae) at 10·9%. 相似文献