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81.
Ancient animal migration: a case study of eyeless,dimorphic Devonian trilobites from Poland 下载免费PDF全文
We report evidence of one of the oldest known animal migratory episodes in the form of queues of the eyeless trilobite Trimerocephalus chopini Kin & B?a?ejowski, from the Late Devonian (Famennian) of central Poland. In addition, there is evidence for two morphs in this population, one with nine segments and the other with ten. We infer that these queues represent mass migratory chains coordinated by chemotaxis, comparable to those observed in modern crustaceans such as spiny lobsters, and further suggest that the two forms, which occur in an approximately 1:1 ratio, may be dimorphs. These ancient arthropods may have migrated periodically to shallow marine areas for mass mating and spawning. The sudden death of the trilobites in the queues may have been caused by excess carbon dioxide and hydrogen sulphide introduced into the bottom water by distal storm disturbance of anoxic sediments. This study demonstrates the potential for further research on the evolution and ecology of aggregative behaviour in marine arthropods. 相似文献
82.
Clay Trauernicht Brett P. Murphy Lynda D. Prior Michael J. Lawes David M. J. S. Bowman 《Ecosystems》2016,19(5):896-909
Woody plant demographics provide important insight into ecosystem state-shifts in response to changing fire regimes. In Australian tropical savannas, the switch from patchy landscape burning by Aborigines to unmanaged wildfires within the past century has been implicated in biodiversity declines including the fire-sensitive conifer, Callitris intratropica. C. intratropica commonly forms small, closed-canopy groves that exclude fire and allow recruitment of conspecifics and other fire-sensitive woody plants. C. intratropica groves provide a useful indicator of heterogeneity and fire regime change, but the mechanisms driving the species’ persistence and decline remain poorly understood. We examined the hypothesis that C. intratropica population stability depends upon a regime of frequent, low-intensity fires maintained by Aboriginal management. We combined integral projection models of C. intratropica population behaviour with an environmental state change matrix to examine how vital rates, grove dynamics and the frequency of high- and low-intensity fires contribute to population stability. Closed-canopy C. intratropica groves contributed disproportionately to population growth by promoting recruitment, whereas singleton trees accounted for a larger proportion of adult mortality. Our patch-based population model predicted population declines under current fire frequencies and that the recruitment of new groves plays a critical role in the species’ persistence. Our results also indicated that reducing fire intensity, a key outcome of Aboriginal burning, leads to C. intratropica population persistence even at high fire frequencies. These findings provide insight into the relationship between ecosystem composition and human–fire interactions and the role of fire management in sustaining the mosaics that comprise ‘natural’ systems. 相似文献
83.
Phytophthora capsici homologue of the cell cycle regulator SDA1 is required for sporangial morphology,mycelial growth and plant infection 下载免费PDF全文
SDA1 encodes a highly conserved protein that is widely distributed in eukaryotic organisms. SDA1 is essential for cell cycle progression and organization of the actin cytoskeleton in yeasts and humans. In this study, we identified a Phytophthora capsici orthologue of yeast SDA1, named PcSDA1. In P. capsici, PcSDA1 is strongly expressed in three asexual developmental states (mycelium, sporangia and germinating cysts), as well as late in infection. Silencing or overexpression of PcSDA1 in P. capsici transformants affected the growth of hyphae and sporangiophores, sporangial development, cyst germination and zoospore release. Phalloidin staining confirmed that PcSDA1 is required for organization of the actin cytoskeleton. Moreover, 4′,6‐diamidino‐2‐phenylindole (DAPI) staining and PcSDA1‐green fluorescent protein (GFP) fusions revealed that PcSDA1 is involved in the regulation of nuclear distribution in hyphae and sporangia. Both silenced and overexpression transformants showed severely diminished virulence. Thus, our results suggest that PcSDA1 plays a similar role in the regulation of the actin cytoskeleton and nuclear division in this filamentous organism as in non‐filamentous yeasts and human cells. 相似文献
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Clinkenbeard Erica L. Turpin Courtney Jiang Jieyun Peterson Martha L. Spear Brett T. 《Mammalian genome》2019,30(7-8):226-236
Mammalian Genome - BALB/cJ mice exhibit considerable phenotypic differences with other BALB/c substrains. Some of these traits involve the liver, including persistent postnatal expression of genes... 相似文献
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Hugh F. Davies Willie Rioli Jos Puruntatameri Willie Roberts Colin Kerinaiua Vivian Kerinauia Kim Brooks Womatakimi Graeme R. Gillespie Brett P. Murphy 《Austral ecology》2019,44(5):868-879
Since European settlement, many granivorous birds of northern Australia's savanna landscapes have declined. One such example, the partridge pigeon (Geophaps smithii), has suffered a significant range contraction, disappearing from at least half of its pre‐European range. Multiple factors have been implicated in this decline, including the loss of traditional Aboriginal burning practices, grazing by large exotic herbivores and predation by feral cats (Felis catus). While populations of partridge pigeon on the Tiwi Islands may be particularly important for the long‐term persistence of this species, they too may be at risk of decline. However, as a reliable method to detect this species has not yet been developed and tested, we lack the ability to identify, at an early stage, the species' decline in a given location or region. This severely limits our capacity to make informed management decisions. Here, we demonstrate that the standard camera trapping approach for native mammal monitoring in northern Australia attained an overall probability of detecting partridge pigeon greater than 0.98. We thus provide a robust estimate of partridge pigeon site occupancy (0.30) on Melville Island, the larger of the two main Tiwi Islands. The information presented here for the partridge pigeon represents a critical first step towards the development of optimal monitoring programmes with which to gauge population trajectories, as well as the response to remedial management actions. In the face of ongoing biodiversity loss, such baseline information is vital for management agencies to make informed decisions and should therefore be sought for as many species as possible. 相似文献
88.
Brett R. Addis Bret W. Tobalske Jon M. Davenport Winsor H. Lowe 《Ecology and evolution》2019,9(18):10644-10653
Across taxa, individuals vary in how far they disperse, with most individuals staying close to their origin and fewer dispersing long distances. Costs associated with dispersal (e.g., energy, risk) are widely believed to trade off with benefits (e.g., reduced competition, increased reproductive success) to influence dispersal propensity. However, this framework has not been applied to understand variation in dispersal distance, which is instead generally attributed to extrinsic environmental factors. We alternatively hypothesized that variation in dispersal distances results from trade‐offs associated with other aspects of locomotor performance. We tested this hypothesis in the stream salamander Gyrinophilus porphyriticus and found that salamanders that dispersed farther in the field had longer forelimbs but swam at slower velocities under experimental conditions. The reduced swimming performance of long‐distance dispersers likely results from drag imposed by longer forelimbs. Longer forelimbs may facilitate moving longer distances, but the proximate costs associated with reduced swimming performance may help to explain the rarity of long‐distance dispersal. The historical focus on environmental drivers of dispersal distances misses the importance of individual traits and associated trade‐offs among traits affecting locomotion. 相似文献
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