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941.
Laura Gangoso José A. Donázar Stephan Scholz César J. Palacios Fernando Hiraldo 《Biodiversity and Conservation》2006,15(7):2231-2248
Introduction of alien herbivores in sensitive island systems has resulted in massive effects on vegetation cover, floristic
richness and composition of communities; some species can be even totally extirpated by grazing pressure. Goats Capra hircus and wild rabbits Oryctolagus cuniculus were introduced in the Canary Islands around 500 B.C. Barbary ground squirrels Atlantoxerus getulus were introduced in 1967. Traditional extensive livestock exploitations have been maintained to the present but in the last
decades the number of goats has sharply increased up to densities of 53 heads/km2. Overgrazing and trampling have heavily affected eleven island endemic plant species. Some populations have been reduced
to less than 10 viable individuals. On the other hand, goat carcasses and wild rabbit and squirrel populations help to maintain
populations of three endangered endemic subspecies of birds. This conflict presents important economic and social ramifications:
whereas public funds (mainly through European LIFE projects) are devoted to conservation of plant and avian endemic taxa,
the number of goats increases rapidly thanks to subventions derived from the European Common Agricultural Policy (CAP). Similar
conflicts are apparent in other Mediterranean Basin insular systems. It is urgently necessary to harmonize farming and conservation
objectives in the Canary Islands. The impact of goats on the vegetation should be minimized through limitation of grazing
in sensitive areas with high degree of endemism. Creation of ‘vulture restaurants’ may reduce the dependence of scavengers
on extensive livestock exploitations. We recommend a careful study of ecological relationships within island communities where
non-native species are susceptible of playing a keystonrole as occurs in the Mediterranean Basin archipelagos. 相似文献
942.
This study was conducted in the islands of Lake Ziway located in the main Ethiopian Rift Valley in south-central Ethiopia. Its main objective was to investigate the diversity, regeneration status, socio-economic importance and the factors that cause degradation of the plant resources in the islands. A total of 73 relevés, measuring 20×20 m, were established along line transects laid from the central part of each island to the lake edge in eight aspects. Herbaceous species were sampled by using a 2×2 m sub-relevé laid within each relevé. In each relevé, the cover/abundance of each species was estimated, woody species were counted, diameter at breast height and height of trees and shrubs and the environmental variables altitude, slope, aspect and position were measured. Participatory Rural Appraisal was employed to generate the socio-economic information. A total of 141 species belonging to 113 genera and 55 families were identified, of which 18.4% were trees, 21.3% trees/shrubs, 12.1% shrubs, 3.5% lianas, 4.3% herbaceous climbers and 40.4% herbs. The overall Shannon diversity and evenness of woody species in the islands were 2.60 and 0.62, respectively. The number of species on the islands correlated with island's size, habitat diversity and degree of human disturbance. The similarity in species composition between the islands was low, indicating that each island has its own unique flora. Nine plant communities were recognized and described. The total density and basal area of the vegetation were 2979 individuals ha−1 and 191 m2 ha−1, respectively. The importance value index and the diameter and height class distribution revealed that some species are threatened and need the highest priority for conservation. The socio-economic survey showed that the island communities are highly dependent on the natural vegetation for various purposes. On the other hand, the islanders have maintained the soil and vegetation resources for centuries through their indigenous resource management systems and practices. Human population growth coupled with farmland expansion, soil erosion, free grazing and cutting trees for various purposes are the major threats to the vegetation resources in the islands. The implications of the results are discussed and recommendations are suggested for conservation, management and sustainable utilization of the fragile island ecosystems. 相似文献
943.
J. L. Sánchez Doreste J. Caujapé-Castells J. A. Reyes-Betancort S. Scholz 《Plant Systematics and Evolution》2006,262(3-4):139-151
Genetic variation at 11 isozyme loci was used to explore the levels and apportionment of genetic variation in the eight known
populations of Matthiola bolleana, an endemic Brassicaceae to the Eastern Canarian islands of Fuerteventura and Lanzarote. Within islands, ecosystem antiquity
and uniformity, lack of evidence for selection or genetic bottlenecks, the high genetic identities between the populations,
and the low values of F
ST
converge to suggest that the high levels of variation detected have been maintained in a context of prolonged environmental
stability through an overall predominance of outbreeding and unrestricted gene flow. Despite the geographical closeness between
Fuerteventura and Lanzarote and the long range dispersal features of the propagules of M. bolleana, we detected a striking qualitative genetic differentiation between the two islands. We suggest that wind direction has made
seed and pollen flow between Fuerteventura and Lanzarote much less likely than expected, and that the lack of inter-island
dispersal has far overriden the influence of stochastic forces and of the reproductive attributes of M. bolleana in shaping the patterns of inter-island genetic differentiation. However, genetic similarity in M. bolleana is within the ranges defined by Canarian taxa for which the extent of genetic differentiation has also been assessed using
the values of isozyme genetic identity. 相似文献
944.
The increasingly common phenomenon of habitat fragmentation raises the probability of pollination failure in a number of species,
as both pollen quantity and quality often decrease as populations become isolated. We experimentally investigated whether
pollen was limiting reproductive success of the endangered shrub Buxus balearica in five populations, two continental and three insular, during 2002 and 2003. Pollen limitation varied among populations
and years, but such variation was not related to density or degree of isolation. All populations showed inbreeding depression
at different phases of the reproductive cycle, although its effects differed greatly among sites. Between-population outcrossing
did not have a consistent effect on several components of fitness. The highest levels of inbreeding depression – detected
at the level of fruit and seed set- occurred at the smallest and least fecund populations from each region. This indicates
that further fragmentation of the populations of this already endangered species could certainly threaten their survival. 相似文献
945.
A recently reestablished and increasing population of Hawaiian monk seals in the main Hawaiian Islands (MHI) is encouraging
for this endangered species. However, seals in the MHI may be exposed to a broad range of human, pet, livestock, and feral
animal pathogens. Our objective was to determine the movement and foraging habitats of Hawaiian monk seals in the MHI relative
to the potential exposure of seals to infectious diseases in near-shore marine habitats. We captured 18 monk seals in the
MHI between January 27, 2004 and November 29, 2005, tested them for various infectious diseases, and then monitored the foraging
movements of 11 of them using satellite-linked radio transmitters for the next 32–167 days. All seals tested negative for
canine adenovirus, calicivirus, four morbilliviruses, phocine herpes virus, Leptospira sp., and feline and canine heartworm antigen/antibody. Six of the seals tested positive on complement fixation for Chlamydophila abortus (formerly Chlamydia psittaci). Four seals demonstrated positive titers to Sarcocystis neurona, two to Neospora caninum, and two to Toxoplasma gondii. Fecal cultures showed approximately half (n = 6) positive for E. coli 0157, no Salmonella sp., and only one with Campylobacter sp. Satellite monitored seals spent considerable time foraging, traveling, and resting in neritic waters close to human population
centers, agricultural activity, and livestock ranges, and sources of land-based water runoff and sewage dispersal. Consequently,
Hawaiian monk seals in the MHI may be at risk of exposure to several infectious disease agents associated with terrestrial
animals that can contaminate marine habitats from runoff along drainages and that are known to cause disease in marine mammals.
Further, some seals overlapped substantially in their use of coastal habitats and several moved among islands while foraging
and were seen on beaches near each other. This suggests that diseased seals could infect healthy conspecifics throughout the
MHI. 相似文献
946.
We describe 10 polymorphic tetranucleotide microsatellite loci from the eastern Canary Island lacertid lizard, Gallotia atlantica. Loci were isolated from a partial genomic library that had been enriched for AAAG repeat sequence. All loci were highly polymorphic (eight alleles or more) with observed heterozygosities from 0.75 to 1.00. At least four loci were successfully amplified and polymorphic in the Gran Canarian lacertid, Gallotia stehlini. These loci will be used to examine correlations between patterns of gene flow and recent volcanism on the island of Lanzarote. 相似文献
947.
库克诺你果汁提取物体外清除自由基及抗氧化活性研究 总被引:10,自引:2,他引:8
本文对诺你果汁多糖、乙醇溶出物和乙酸乙酯萃取物体外对超氧阴离子(O2·)、羟自由基(·OH)、DPPH和脂质过氧化(LPO)的抑制作用进行了研究。超氧阴离子(O2·)由邻苯三酚自氧化产生;羟自由基(·OH)由Fenton反应产生;利用Fe2 诱发卵黄脂蛋白产生丙二醛(MDA),TBA法测定。所有测定均为分光光度法。结果表明,与已知抗氧化剂L抗坏血酸相比,乙醇溶出物和乙酸乙酯萃取物均有明显的捕捉自由基和抗氧化能力,而多糖捕捉自由基和抗氧化能力很低,且对O2·没有抑制作用,反而会增加其生成速度。 相似文献
948.
Shinji Sugiura Yuichi Yamaura Tomoyuki Tsuru Hideaki Goto Motohiro Hasegawa Hiroshi Makihara Shun’ichi Makino 《Biodiversity and Conservation》2009,18(8):2101-2118
Natural forests are often replaced by invasive alien trees on isolated oceanic islands. Adequate eradication of invasive trees
should be conducted with the goal of biodiversity conservation, because islands support many endemic organisms that depend
on native forests. An invasive alien tree, Bischofia javanica Blume (Euphorbiaceae), has invaded and replaced natural forests on the oceanic Ogasawara (Bonin) Islands, Japan, in the northwestern
Pacific Ocean. To determine how the removal of B. javanica trees affects insect diversity, we examined flying beetles captured using Malaise traps in B. javanica forests on Hahajima. The abundance, species density, and species composition of wood-boring beetles (Coleoptera: Cerambycidae,
Elateridae, Mordellidae, and Scolytidae) were compared between closed-canopy sites and gaps created by girdling B. javanica trees in alien forests during two seasons (June–July and October–November 2005). Of the collected beetles, 75.8, 87.5, 90.0,
and 0.0% of cerambycid, elaterid, mordellid, and scolytid beetle species, respectively, were endemic to the Ogasawara Islands.
More cerambycid, elaterid, and mordellid individuals were captured in June–July than in October–November; the number of scolytid
individuals did not differ between seasons. More cerambycid, elaterid, and scolytid individuals were captured in artificial
gaps than on the closed-canopy forest floor. Although fewer mordellid individuals were captured in gaps, more endemic mordellids
were captured in gaps. More cerambycid and scolytid species were captured in artificial gaps than in closed-canopy areas.
The positive responses of beetles to artificial gaps suggest that the removal of B. javanica increases beetle diversity and the abundance of endemic beetles. 相似文献
949.
Ammonoids from the basal beds of the Nerpalakh Formation (Lower Frasnian) of Belkovsky Island (New Siberian Archipelago) are systematically studied. Taxonomically, the assemblage studied (Manticoceras insulare sp. nov., Tornoceras typum (Sandberger, 1851), and T. contractum Glenister, 1958) is similar to the Early Frasnian ammonoid assemblage of South Timan, from which its is distinguished by the absence of the genera Timanites and Komioceras. The same beds contain conodonts of the Palmatolepis transitans Zone (= MN 4 Zone of the Montagne Noire standard succession), which allow the correlation of the beds studied with the Timanites keyserlingi and Komioceras stuckenbergi ammonoid zones of South Timan. The Early Frasnian ammonoids could supposedly have entered the region of the New Siberian Archipelago from the southwest at the time of a major transgression, which facilitated the distribution of the genera Manticoceras and Tornoceras. A new species of the genus Manticoceras is described. 相似文献
950.
Zaida Lorenzo Concetta Burgarella Unai L��pez de Heredia Roselyne Lumaret R��my J. Petit ��lvaro Soto Luis Gil 《Annals of botany》2009,104(6):1069-1076