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21.
Traditionally, the field of parasitology has dealt with eukaryoticanimals, to the exclusion of viruses, bacteria, fungi, etc.,which is the way it will be approached here. The focus of thepresent paper will be on certain ecological aspects of the lifecycles and life-history strategies employed by the Digenea,a diverse group of platyhelminths that includes some 25,000species. More specifically, the review will consider the natureof host/parasite interactions within molluscan intermediatehosts and the manner in which these interactions, or lack thereof,function in structuring trematode infracommunities within thesemolluscan intermediate hosts. Literature in this area suggeststhat predation/competition may be a significant structuringforce for infracommunities in certain marine prosobranchs, butnot others, and that temporal/spatial factors may be involvedas structuring mechanisms in at least some freshwater pulmonates. 相似文献
22.
Maternal rank 'inheritance', the process by which juveniles attain positions in the dominance hierarchy adjacent to those of their mothers, occurs in both cercopithecine primates and spotted hyaenas. Maternal rank is acquired in primates through defensive maternal interventions, coalitionary support and unprovoked aggression ('harassment') directed by adult females towards offspring of lower-ranking individuals. Genetic heritability of rank-related traits plays a negligible role in primate rank acquisition. Because the social lives of Crocuta and cercopithecine primates share many common features, we examined whether the same mechanisms might operate in both taxa to promote maternal rank 'inheritance'. We observed a large clan of free-living spotted hyaenas in Kenya to test predictions of four mechanistic hypotheses. Hyaena rank acquisition did not appear to be directly affected by genetic heritability. Unprovoked aggression from adult female hyaenas was not directed preferentially towards low-ranking cubs. However, high-ranking mothers intervened on behalf of their cubs more frequently and more effectively than low-ranking mothers. Maternal interventions and supportive coalitions appeared to reinforce aggression directed at 'appropriate' conspecific targets, whereas coalitionary aggression directed at cubs apparently functioned to extinguish their aggressive behaviour towards 'inappropriate' targets. Young hyaenas and primates thus appear to 'inherit' their mothers' ranks by strikingly similar mechanisms. Copyright 2000 The Association for the Study of Animal Behaviour. 相似文献
23.
Adult Plagioporus sinitsini occur within daughter sporocysts voided with the feces of prosobranch snails Elimia symmetrica in Basin Creek, North Carolina. These worms produced eggs containing active miracidia while still in the snail. Adults in snails and adults in rosyside dace, Clinostomus funduloides, collected from the same stream were indistinguishable morphometrically. Adults in snails develop from cotylocercous cercariae sequestered in daughter sporocysts that pass through the metacercaria stage. These observations, and previous study in Michigan, suggest that the life cycle of P. sinitsini has 3 potential pathways, i.e., a 3-host life cycle involving molluscan, arthropod, and piscine hosts, a 2-host life cycle involving only molluscan and piscine hosts, and a 1-host life cycle involving only the snail host. The truncated life cycles do not appear to be the result of paedomorphosis. 相似文献
24.
Pulmonate snails (Helisoma anceps) of varying sizes were exposed to 2, 4, 8, or 16 eggs of Halipegus occidualis and observed over several months to determine the duration of the prepatent period. Infection probability was positively correlated with number of eggs ingested. The number of eggs ingested did not, however, have a significant effect on the duration of the prepatent period, presumably because low infectivity of the eggs (15%) dictated that most patent infections arose from a single miracidium. There was a significant, positive correlation between snail length (measured at time of exposure) and duration of prepatent period, suggesting that density-dependent effects are, in part, responsible for the initiation of cercariae production in H. occidualis. 相似文献
25.
Maila Giannandrea Maria Lidia Mignogna Salvatore Carrabino Matteo Vecellio Silvia Russo Lidia Larizza Hans-Hilger Ropers Vera Kalscheuer Cindy Skinner Jozef Gecz Hilde Van Esch Jamel Chelly Daniela Toniolo Patrizia D'Adamo 《American journal of human genetics》2010,86(2):185-195
Human Mental Retardation (MR) is a common and highly heterogeneous pediatric disorder affecting around 3% of the general population; at least 215 X-linked MR (XLMR) conditions have been described, and mutations have been identified in 83 different genes, encoding proteins with a variety of function, such as chromatin remodeling, synaptic function, and intracellular trafficking. The small GTPases of the RAB family, which play an essential role in intracellular vesicular trafficking, have been shown to be involved in MR. We report here the identification of mutations in the small GTPase RAB39B gene in two male patients. One mutation in family X (D-23) introduced a stop codon seven amino acids after the start codon (c.21C > A; p.Y7X). A second mutation, in the MRX72 family, altered the 5′ splice site (c.215+1G > A) and normal splicing. Neither instance produced a protein. Mutations segregate with the disease in the families, and in some family members intellectual disabilities were associated with autism spectrum disorder, epileptic seizures, and macrocephaly. We show that RAB39B, a novel RAB GTPase of unknown function, is a neuronal-specific protein that is localized to the Golgi compartment. Its downregulation leads to an alteration in the number and morphology of neurite growth cones and a significant reduction in presynaptic buttons, suggesting that RAB39B is required for synapse formation and maintenance. Our results demonstrate developmental and functional neuronal alteration as a consequence of downregulation of RAB39B and emphasize the critical role of vesicular trafficking in the development of neurons and human intellectual abilities. 相似文献
26.
Froyen G Bauters M Boyle J Van Esch H Govaerts K van Bokhoven H Ropers HH Moraine C Chelly J Fryns JP Marynen P Gecz J Turner G 《Human genetics》2007,121(5):539-547
Using high resolution X chromosome array-CGH we identified an interstitial microdeletion at Xp11.23 in three brothers with
moderate to severe mental retardation (MR) without dysmorphic features. The extent of the deletion was subsequently delineated
to about 50 kb by regular PCR and included only the SLC38A5 and FTSJ1 genes. The loss of the FTSJ1 MR gene in males is expected to result in the observed phenotype but the contribution of the deletion of the solute carrier
SLC38A5 gene is less clear. Their mother also carries the deletion and completely inactivates the aberrant X chromosome. Interestingly,
the distal breakpoint is situated within a 200 kb SSX repeat region that appears to stimulate recombination since subtle copy
number changes often occur at this location and it is frequently involved in translocations in tumours. Since this apparent
SSX unstable structure is flanked proximally by FTSJ1 and PQBP1, subtle deletions or duplications at this location would be expected to cause MR, as in our family. So far, we have screened
a cohort of 300 patients but did not find additional aberrations at the FTSJ1 locus indicating that the frequency is likely to be low. 相似文献
27.
The sea aster, Aster tripolium L., grows naturally in temperate regions, mainly in the salt meadows close to the coast. The species is also found in naturally and anthropogenically salt-contaminated inland habitats, such as potash mine dumps. The genetic relationships among populations from different habitats and correlations of the genotype with physiological and vegetational parameters were investigated. A. tripolium plants from five different sites close to the seashore on the North Sea island Baltrum, from five different potash mine dumps and, as an outgroup, from the seashore in Japan were probed. DNA was extracted from five plants from each of the 11 A. tripolium populations and analyzed for random amplified polymorphic DNA (RAPD). Altogether 35 polymorphic bands in 51 individuals and 45 different detectable genotypes could be identified. For evaluation of the genetic variation using RAPD bands, the neighbor-joining method, the principal coordinate analysis, and the analysis of molecular variance were applied, resulting in the classification into three genetic groups. A. tripolium plants from different ecological habitats on Baltrum were closely related while the plants growing at the deposit dumps showed a higher genetic diversity. The Japanese population was genetically very different from the German populations. Correlations between phytosociological and soil parameters and the respective genotype were not significant. The results argue for a conservation of anthropogenically salt-contaminated habitats to maintain genetic variability not only on the species level, but also within a species. 相似文献
28.
Mala Isrie Martin Breuss Guoling Tian Andi?Harley Hansen Francesca Cristofoli Jasmin Morandell Zachari?A. Kupchinsky Alejandro Sifrim Celia?Maria Rodriguez-Rodriguez Elena?Porta Dapena Kurston Doonanco Norma Leonard Faten Tinsa Stéphanie Moortgat Hakan Ulucan Erkan Koparir Ender Karaca Nicholas Katsanis Valeria Marton Joris?Robert Vermeesch Erica?E. Davis Nicholas?J. Cowan David?Anthony Keays Hilde Van?Esch 《American journal of human genetics》2015,97(6):790-800
Circumferential skin creases Kunze type (CSC-KT) is a specific congenital entity with an unknown genetic cause. The disease phenotype comprises characteristic circumferential skin creases accompanied by intellectual disability, a cleft palate, short stature, and dysmorphic features. Here, we report that mutations in either MAPRE2 or TUBB underlie the genetic origin of this syndrome. MAPRE2 encodes a member of the microtubule end-binding family of proteins that bind to the guanosine triphosphate cap at growing microtubule plus ends, and TUBB encodes a β-tubulin isotype that is expressed abundantly in the developing brain. Functional analyses of the TUBB mutants show multiple defects in the chaperone-dependent tubulin heterodimer folding and assembly pathway that leads to a compromised yield of native heterodimers. The TUBB mutations also have an impact on microtubule dynamics. For MAPRE2, we show that the mutations result in enhanced MAPRE2 binding to microtubules, implying an increased dwell time at microtubule plus ends. Further, in vivo analysis of MAPRE2 mutations in a zebrafish model of craniofacial development shows that the variants most likely perturb the patterning of branchial arches, either through excessive activity (under a recessive paradigm) or through haploinsufficiency (dominant de novo paradigm). Taken together, our data add CSC-KT to the growing list of tubulinopathies and highlight how multiple inheritance paradigms can affect dosage-sensitive biological systems so as to result in the same clinical defect. 相似文献
29.
Marjolein Glas H. Bart van den Berg van Saparoea Stephen H. McLaughlin Winfried Roseboom Fan Liu Gregory M. Koningstein Alexander Fish Tanneke den Blaauwen Albert J. R. Heck Luitzen de Jong Wilbert Bitter Iwan J. P. de Esch Joen Luirink 《The Journal of biological chemistry》2015,290(35):21498-21509
Cell division in Escherichia coli involves a set of essential proteins that assembles at midcell to form the so-called divisome. The divisome regulates the invagination of the inner membrane, cell wall synthesis, and inward growth of the outer membrane. One of the divisome proteins, FtsQ, plays a central but enigmatic role in cell division. This protein associates with FtsB and FtsL, which, like FtsQ, are bitopic inner membrane proteins with a large periplasmic domain (denoted FtsQp, FtsBp, and FtsLp) that is indispensable for the function of each protein. Considering the vital nature and accessible location of the FtsQBL complex, it is an attractive target for protein-protein interaction inhibitors intended to block bacterial cell division. In this study, we expressed FtsQp, FtsBp, and FtsLp individually and in combination. Upon co-expression, FtsQp was co-purified with FtsBp and FtsLp from E. coli extracts as a stable trimeric complex. FtsBp was also shown to interact with FtsQp in the absence of FtsLp albeit with lower affinity. Interactions were mapped at the C terminus of the respective domains by site-specific cross-linking. The binding affinity and 1:1:1 stoichiometry of the FtsQpBpLp complex and the FtsQpBp subcomplex were determined in complementary surface plasmon resonance, analytical ultracentrifugation, and native mass spectrometry experiments. 相似文献