全文获取类型
收费全文 | 83篇 |
免费 | 8篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 8篇 |
2012年 | 4篇 |
2011年 | 6篇 |
2010年 | 6篇 |
2009年 | 3篇 |
2008年 | 2篇 |
2006年 | 7篇 |
2005年 | 4篇 |
2004年 | 4篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1977年 | 2篇 |
排序方式: 共有91条查询结果,搜索用时 31 毫秒
21.
22.
Sehgal A Bettiol S Pypaert M Wenk MR Kaasch A Blader IJ Joiner KA Coppens I 《Traffic (Copenhagen, Denmark)》2005,6(12):1125-1141
The intracellular protozoan Toxoplasma gondii is auxotrophic for low-density lipoprotein (LDL)-derived cholesterol (C). We previously showed that T. gondii scavenges this essential lipid from host endolysosomal compartments and that C delivery to the parasitophorous vacuole (PV) does not require transit through host Golgi or endoplasmic reticulum. In this study, we explore the itinerary of C from the host endolysosomes to the PV. Labeled C incorporated into LDL is rapidly detected in intravacuolar parasites and partially esterified by the parasites. In contrast to diverse mammalian organelles, the post-endolysosomal transfer of C to the PV does not involve the host plasma membrane as an intermediate. Nevertheless, the PV membrane is accessible to extracellular sterol acceptors, suggesting C trafficking from intracellular parasites to host plasma membrane. C movement to the PV requires temperatures permissive for vesicular transport, metabolic energy and functional microtubules. Host caveolae vesicles and the sterol carrier protein-2 do not participate in this process. Proteolytic treatment of purified PV or free parasites abolishes C acquisition by the parasites. Altogether, these results support a vesicular transport system from host endolysosomes to the PV, and a requirement for PV membrane and parasite plasma membrane proteins in C delivery to T. gondii. 相似文献
23.
Clunes MT Lindsay SL Roussa E Quinton PM Bovell DL 《Journal of molecular histology》2004,35(4):339-345
The localisation of the vacuolar proton pump (V-H+ -ATPase) and the enzyme carbonic anhydrase II (CAII) was investigated in the human eccrine sweat gland employing standard immunohistochemical techniques after antigen retrieval using microwave heat treatment and high pressure. The high-pressure antigen retrieval unmasked the presence of V-H+ -ATPase in the clear cells of the secretory coil, with a distribution similar to that previously observed for CAII. However, the dark cells were unreactive to both antibodies. In addition, heat and high-pressure antigen retrieval demonstrated the presence of CAII in the apical zone of luminal cells of the reabsorptive duct, a location not previously reported. The localisation of V-H+ -ATPase and CAII in the secretory coil clear cells suggests that the formation of HCO3- and H+ by carbonic anhydrase II and the transport of H+ by V-H+ -ATPase may play an role in sweat fluid secretion. Their presence at the apex of the duct cells indicates involvement in ductal ion reabsorption. 相似文献
24.
25.
ABSTRACT The acoustic characteristics of an Amazonian lowland rain forest study site in southern Venezuela was analysed to determine environmental constraints upon acoustic communication. Signal degradation was measured by conducting transmission experiments at different heights above ground level. Measurements of ambient noise served to determine possible communication distances for various times of day, heights above ground level and frequencies. “Sound windows” for acoustic long-range communication were found for low frequencies, calling heights in the midstorey and calling in the morning or during the night. Sound attenuation was affected by height and frequency but not by time of day. Background noise varied remarkably with time of day and frequency and had a greater impact on communication distance than signal attenuation. 相似文献
26.
Organismic diversity, as well as distributional and ecological patterns, can be fully understood in an evolutionary framework only. Reliable phylogenetic trees are required to ‘read history’, but are not yet available for most marine invertebrate groups. Molecular systematics offers an enormous potential, but still fails for ‘all‐species approaches’ on groups with species that are rare or occur in remote areas only, simply because there is no easily collectable material available for sequence analyses. Exploring morphologically aberrant corambid nudibranch gastropods as a case study, we assess whether or not morphology‐based phylogenetic analyses can fill this gap and produce a tree that allows a detailed view on evolutionary history. Morphology‐based parsimony analysis of corambids and potential relatives resulted in a well‐resolved and remarkably robust topology. As an offshoot of kelp‐associated onchidoridid ancestors, and obviously driven by the heterochronic shortening of life cycles and morphological juvenilization in an ephemeral habitat, the ancestor of corambids originated in cool northern Pacific coastal waters. A basal clade (the genus Loy) diverged there, adapting to live on soft bottoms under successive reversals of paedomorphic traits. The more speciose Corambe lineage radiated preying upon short‐lived encrusting bryozoa in a high‐energy kelp environment. Selection favoured transformation of the mantle into a cuticle‐covered shield, and successive paedomorphic translocations of dorid anal gills to the protected ventral side of the body, where compensatory, multiple gills evolved. Corambe species probably first colonized tropical American seas, and then radiated in worldwide temperate waters: this is explained by the excellent long‐distance dispersal abilities afforded by rafting on kelp, with the subsequent divergence of colonizers in allopatry. The competitive coexistence of Corambe pacifica MacFarland & O'Donoghue, 1929 and Corambe steinbergae (Lance, 1962) off California is the result of independent colonization events. The closing of the Isthmus of Panama separated the latter species from a flock that have radiated within warm Atlantic waters since then. Our case study shows that morphological structures, if investigated in depth, bear the potential for an efficient phylogenetic analysis of groups that are still elusive to molecular analyses. Tracing character evolution and integrating a wide range of geographic, biological, and ecological background information allowed us to reconstruct an evolutionary scenario for corambids that is detailed and plausible, and can be tested by future molecular approaches. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163 , 585–604. 相似文献
27.
Intracellular pathogens can replicate efficiently only after they manipulate and modify their host cells to create an environment conducive to replication. While diverse cellular pathways are targeted by different pathogens, metabolism, membrane and cytoskeletal architecture formation, and cell death are the three primary cellular processes that are modified by infections. Toxoplasma gondii is an obligate intracellular protozoan that infects ∼30% of the world''s population and causes severe and life-threatening disease in developing fetuses, in immune-comprised patients, and in certain otherwise healthy individuals who are primarily found in South America. The high prevalence of Toxoplasma in humans is in large part a result of its ability to modulate these three host cell processes. Here, we highlight recent work defining the mechanisms by which Toxoplasma interacts with these processes. In addition, we hypothesize why some processes are modified not only in the infected host cell but also in neighboring uninfected cells. 相似文献
28.
Y Deng J Zhao D Sakurai KM Kaufman JC Edberg RP Kimberly DL Kamen GS Gilkeson CO Jacob RH Scofield CD Langefeld JA Kelly ME Alarcón-Riquelme BIOLUPUS GENLES Networks JB Harley TJ Vyse BI Freedman PM Gaffney KM Sivils JA James TB Niewold RM Cantor W Chen BH Hahn EE Brown PROFILE BP Tsao 《Arthritis research & therapy》2012,14(Z3):A5
29.
30.
Horizontal transmission, vertical inactivation, and stochastic loss of mariner-like transposable elements 总被引:13,自引:5,他引:8
Horizontal transmission has been well documented as a major mechanism for
the dissemination of mariner-like elements (MLEs) among species. Less well
understood are mechanisms that limit vertical transmission of MLEs
resulting in the "spotty" or discontinuous distribution observed in closely
related species. In this article we present evidence that the genome of the
common ancestor of the melanogaster species subgroup of Drosophila
contained an MLE related to the mellifera (honey bee) subfamily. Horizontal
transmission, approximately 3-10 MYA, is strongly suggested by the
observation that the sequence of the MLE in Drosophila erecta is 97%
identical in nucleotide sequence with that of an MLE in the cat flea,
Ctenocephalides felis. The D. erecta MLE has a spotty distribution among
species in the melanogaster subgroup. The element has a high copy number in
D. erecta and D. orena, a moderate copy number in D. teissieri and D.
yakuba, and was apparently lost ("stochastic loss") in the lineage leading
to D. melanogaster, D. simulans, D. mauritiana, and D. sechellia. In D.
erecta, most copies are concentrated in the heterochromatin. Two copies
from D. erecta, denoted De12 and De19, were cloned and sequenced, and they
appear to be nonfunctional ("vertical inactivation"). It therefore appears
that the predominant mode of MLE evolution is vertical inactivation and
stochastic loss balanced against occasional reinvasion of lineages by
horizontal transmission.
相似文献