全文获取类型
收费全文 | 149篇 |
免费 | 7篇 |
出版年
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 5篇 |
2016年 | 5篇 |
2015年 | 6篇 |
2014年 | 3篇 |
2013年 | 3篇 |
2012年 | 5篇 |
2011年 | 2篇 |
2010年 | 5篇 |
2009年 | 1篇 |
2008年 | 6篇 |
2007年 | 6篇 |
2006年 | 5篇 |
2005年 | 11篇 |
2004年 | 9篇 |
2003年 | 3篇 |
2002年 | 6篇 |
2001年 | 7篇 |
2000年 | 6篇 |
1999年 | 9篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1995年 | 1篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1955年 | 1篇 |
排序方式: 共有156条查询结果,搜索用时 15 毫秒
81.
Sabrina B. L. Araujo Mariana Pires Braga Daniel R. Brooks Salvatore J. Agosta Eric P. Hoberg Francisco W. von Hartenthal Walter A. Boeger 《PloS one》2015,10(10)
Despite the fact that parasites are highly specialized with respect to their hosts, empirical evidence demonstrates that host switching rather than co-speciation is the dominant factor influencing the diversification of host-parasite associations. Ecological fitting in sloppy fitness space has been proposed as a mechanism allowing ecological specialists to host-switch readily. That proposal is tested herein using an individual-based model of host switching. The model considers a parasite species exposed to multiple host resources. Through time host range expansion can occur readily without the prior evolution of novel genetic capacities. It also produces non-linear variation in the size of the fitness space. The capacity for host colonization is strongly influenced by propagule pressure early in the process and by the size of the fitness space later. The simulations suggest that co-adaptation may be initiated by the temporary loss of less fit phenotypes. Further, parasites can persist for extended periods in sub-optimal hosts, and thus may colonize distantly related hosts by a "stepping-stone" process. 相似文献
82.
A modified synthesis of 1L-1,2:3,4-di-O-cyclohexylidene-5-O-methyl-chiro-inositol has been accomplished that improves the overall procedure, yield, and environmental aspects of its formation. Several inositol analogues have been prepared from this intermediate for testing as biosynthetic inhibitors of glycosyl-phosphatidylinositol (GPI) anchor formation. 相似文献
83.
The crisis of emerging infectious disease stems from the absence of comprehensive taxonomic inventories of the world's parasites, which includes the world's pathogens. Recent technological developments raise hopes that the global inventory of species, including potential pathogens, can be accomplished in a timely and cost-effective manner. The phylogenetics revolution initiated by systematists provides a means by which information about pathogen transmission dynamics can be placed in a predictive framework. Increasingly, that information is widely available in digital form on the Internet. Systematic biology is well positioned to play a crucial role in efforts to be proactive in the arena of emerging parasitic and infectious diseases. 相似文献
84.
Out of Africa: origins of the Taenia tapeworms in humans 总被引:3,自引:0,他引:3
Hoberg EP Alkire NL de Queiroz A Jones A 《Proceedings. Biological sciences / The Royal Society》2001,268(1469):781-787
Phylogenetic and divergence date analyses indicate that the occurrence of Taenia tapeworms in humans pre-dates the development of agriculture, animal husbandry and domestication of cattle (Bos spp.) or swine (Sus scrofa). Taeniid tapeworms in Africa twice independently colonized hominids and the genus Homo prior to the origin of modern humans. Dietary and behavioural shifts, from herbivory to scavenging and carnivory, as early Homo entered the carnivore guild in the Pliocene/Pleistocene, were drivers for host switching by tapeworms to hominids from carnivores including hyaenids and felids. Parasitological data provide a unique means of elucidating the historical ecology, foraging behaviour and food habits of hominids during the diversification of Homo spp. 相似文献
85.
Santín-Durán M Alunda JM Hoberg EP;Concepción de la Fuente 《The Journal of parasitology》2004,90(6):1378-1386
A survey of abomasal parasites in cervids from Central Spain was conducted at 3 sites, Quintos de Mora (Toledo), Malué?ez de Arriba (Cáceres), and La Herguijuela (Cáceres). Commonly occurring helminths belonged to 3 polymorphic species of the Ostertagiinae: Spiculopteragia asymmetricalS. quadrispiculata, Ostertagia leptospicularis/O. kolchida, and O. drozdzi/O. ryjikovi. Trichostrongylus axei was found in very few cases. Ostertagia drozdzi/O. ryjikovi and the minor male morphotype, S. quadrispiculata, are reported for the first time in red deer from Spain. The 3 ostertagiine species are also reported for the first time in fallow deer from Spain. These 3 species of Ostertagiinae are primarily parasites of cervids, and nematode species characteristic of domestic ruminants were not present. Prevalence of infection by gastrointestinal parasites in cervids was high, ranging from 97.5 to 100%, across the 3 areas sampled. Mean intensity of infection and abundance showed a positive relationship to the population density of red deer. Helminth burdens were higher in fallow deer than in the sympatric red deer and may reflect the gregarious social structure and different foraging patterns of fallow deer. 相似文献
86.
87.
Kutz SJ Hoberg EP Polley L Jenkins EJ 《Proceedings. Biological sciences / The Royal Society》2005,272(1581):2571-2576
Global climate change is altering the ecology of infectious agents and driving the emergence of disease in people, domestic animals, and wildlife. We present a novel, empirically based, predictive model for the impact of climate warming on development rates and availability of an important parasitic nematode of muskoxen in the Canadian Arctic, a region that is particularly vulnerable to climate change. Using this model, we show that warming in the Arctic may have already radically altered the transmission dynamics of this parasite, escalating infection pressure for muskoxen, and that this trend is expected to continue. This work establishes a foundation for understanding responses to climate change of other host-parasite systems, in the Arctic and globally. 相似文献
88.
Burstein E Hoberg JE Wilkinson AS Rumble JM Csomos RA Komarck CM Maine GN Wilkinson JC Mayo MW Duckett CS 《The Journal of biological chemistry》2005,280(23):22222-22232
89.
Monophyly for the Nematodirinae, with 5 genera, Murielus, Rauschia, Nematodiroides, Nematodirus, and Nematodirella was confirmed based on comparative morphology and phylogenetic analysis of structural characters. This concept for the nematodirines excludes the monotypic Lamanema chavezi, but otherwise corroborates generic-level diversity as defined in prior studies. Exhaustive analysis resulted in 1 most parsimonious tree (36 steps; consistency index [CI] = 0.94; retention index [RI] = 0.93; excluding phylogenetically uninformative characters, CI = 0.92). As an inclusive or monophyletic group, Nematodirinae was diagnosed by 8 synapomorphies (7 are unequivocal): (1) large eggs, (2) long filiform spicules, (3) basal division of the dorsal ray, (4) symmetrical membrane enveloping the spicule tips, (5) fused structure of the spicule tips, (6) absence of the gubernaculum, (7) development of the third-stage larva within the egg, and (8) ornamentation in the form of discrete bosses on the bursa. Exclusion of Lamanema will require new assessments of historical biogeography and the evolution of host associations for the nematodirines. 相似文献
90.
Hoberg EP Jenkins EJ Rosenthal B Wong M Erbe EF Kutz SJ Polley L 《The Journal of parasitology》2005,91(6):1318-1325
We demonstrate polymorphism in the structure of the tail among first-stage larvae of Parelaphostrongylus odocoilei (Protostrongylidae). Two distinct larvae, both with a characteristic dorsal spine, include (1) a morphotype with a kinked conical tail marked by 3 distinct transverse folds or joints and a symmetrical terminal tail spike and (2) a morphotype with a digitate terminal region lacking folds or joints and with an asymmetrical, subterminal tail spike. These divergent larval forms had been postulated as perhaps representing distinct species of elaphostrongyline nematodes. Application of a multilocus approach using ITS-2 sequences from the nuclear genome and COX-II sequences from the mitochondrial genome confirmed the identity of these larvae as P. odocoilei. Additionally, based on scanning electron microscopy (low-temperature field emission), the cephalic region of these larvae consisted of a cuticular triradiate stoma surrounded by 6 single circumoral papillae of the inner circle, 10 papillae of the outer circle (4 paired and 2 single), and 2 lateral amphids. Our's is the first demonstration of structural polymorphism among larval conspecifics in the Metastrongyloidea and Strongylida. The basis for this polymorphism remains undetermined, but such phenomena, if discovered to be more widespread, may contribute to continued confusion in discriminating among first-stage larvae for species, genera, and subfamilies within Protostrongylidae. 相似文献