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排序方式: 共有109条查询结果,搜索用时 46 毫秒
1.
David W. Zeh Jeanne A. Zeh 《Evolution; international journal of organic evolution》1994,48(4):1168-1182
Differences in secondary sexual characteristics of males often provide the most conspicuous means of distinguishing between closely related species. Does this therefore imply that the absence of differentiation in exaggerated male traits between allopatric populations provides evidence of a single, genetically cohesive species? We addressed this question with a comprehensive investigation of two populations (French Guiana and Panama) of the harlequin beetle-riding pseudoscorpion, Cordylochernes scorpioides. This highly sexually dimorphic pseudoscorpion is currently described as a single species, ranging throughout the Neotropics. Our morphometric analyses detected minimal differentiation between the two populations in all nine external morphological characters measured, including sexually dimorphic traits in males. Only in traits of the spermatophore was there any appreciable level of differentiation. Behavior differentiation and prezygotic reproductive isolation were also limited: 78.3% of males successfully transferred sperm to “foreign” females, and in 63.9% of these cases, females' eggs were successfully fertilized. By contrast, extensive divergence existed in two of nine electrophoretic loci, including an essentially fixed-allele difference at the Ldh locus. Most significantly, postzygotic reproductive isolation was complete, with heteropopulation zygotes invariably aborting early in development. These results strongly suggest that the two populations are, in fact, sibling species, a conclusion supported by our recently published findings on their marked divergence in minisatellite DNA. How can such interpopulation homogeneity in male sexually dimorphic traits exist in the face of strong genetic divergence? We propose that sexual selection, oscillating between favoring small and then large males, maintains such high levels of male variability within each population that it has obscured a speciation event in which genetic divergence and postzygotic incompatibility have clearly outpaced the evolution of prezygotic reproductive isolation. 相似文献
2.
3.
Jeanne A. Zeh David W. Zeh 《Biological journal of the Linnean Society. Linnean Society of London》2013,108(3):509-520
The evolution of exaggerated male traits is frequently driven by competition between males to control resources critical for female survival and/or reproductive success. For flightless arthropods specializing on patchy habitats, dispersal agents may represent one such critical resource. The Neotropical pseudoscorpion, Semeiochernes armiger, disperses to new habitats by attaching to the giant timber fly, Pantophthalmus tabaninus, as it ecloses from pupal boreholes within decaying Ficus trees. In a study that combined field observations of mating with experimental removal of individuals from a large, pre‐dispersal population, our morphometric analyses revealed that S. armiger is among the most highly sexually dimorphic pseudoscorpions known, with males possessing unusual, triangular‐shaped pedipalpal chelae (hands) and a male‐specific, dimorphic chela peg that exhibits threshold trait expression. Several lines of evidence indicate that extreme sexual dimorphism in S. armiger results from male competition to monopolize pantophthalmid bores as strategic sites for inseminating females on the verge of dispersal. Sexually dimorphic pedipalpal characters were significantly larger in males located in and around pantophthalmid boreholes, compared with males collected at the periphery of the pantophthalmid emergence zone. Removal of pseudoscorpions resulted in a significant decline in pedipalpal size of males associated with pantophthalmid bores, followed by a rebound in size after collected individuals were returned to the tree. Most significantly, field observations of mating indicate that this competition translates into intense selection for exaggerated male traits, with all traits of the sexually dimorphic chelae exhibiting highly significant sexual selection differentials in males. © 2013 The Linnean Society of London 相似文献
4.
Wen Hou Yangchun Xie Xinxin Song Xiaofang Sun Michael T. Lotze Herbert J. Zeh III 《Autophagy》2016,12(8):1425-1428
Macroautophagy/autophagy is an evolutionarily conserved degradation pathway that maintains homeostasis. Ferroptosis, a novel form of regulated cell death, is characterized by a production of reactive oxygen species from accumulated iron and lipid peroxidation. However, the relationship between autophagy and ferroptosis at the genetic level remains unclear. Here, we demonstrated that autophagy contributes to ferroptosis by degradation of ferritin in fibroblasts and cancer cells. Knockout or knockdown of Atg5 (autophagy-related 5) and Atg7 limited erastin-induced ferroptosis with decreased intracellular ferrous iron levels, and lipid peroxidation. Remarkably, NCOA4 (nuclear receptor coactivator 4) was a selective cargo receptor for the selective autophagic turnover of ferritin (namely ferritinophagy) in ferroptosis. Consistently, genetic inhibition of NCOA4 inhibited ferritin degradation and suppressed ferroptosis. In contrast, overexpression of NCOA4 increased ferritin degradation and promoted ferroptosis. These findings provide novel insight into the interplay between autophagy and regulated cell death. 相似文献
5.
Sebastian Vogel Pranav Murthy Xiangdong Cui Michael T. Lotze Herbert J. Zeh Ulka Sachdev 《Biochemical and biophysical research communications》2019,508(2):614-619
Platelets play a critical role in the pathophysiology of peripheral arterial disease (PAD). The mechanisms by which muscle ischemia regulates aggregation of platelets are poorly understood. We have recently identified the Nod-like receptor nucleotide-binding domain leucine rich repeat containing protein 3 (NLRP3) expressed by platelets as a critical regulator of platelet activation and aggregation, which may be triggered by activation of toll-like receptor 4 (TLR4). In this study, we performed femoral artery ligation (FAL) in transgenic mice with platelet-specific ablation of TLR4 (TLR4 PF4) and in NLRP3 knockout (NLRP3?/?) mice. NLRP3 inflammasome activity of circulating platelets, as monitored by activation of caspase-1 and cleavage of interleukin-1β (IL-1β), was upregulated in mice subjected to FAL. Genetic ablation of TLR4 in platelets led to decreased platelet caspase 1 activation and platelet aggregation, which was reversed by the NLRP3 activator Nigericin. Two weeks after the induction of FAL, ischemic limb perfusion was increased in TLR4 PF4 and NLRP3?/? mice as compared to control mice. Hence, activation of platelet TLR4/NLRP3 signaling plays a critical role in upregulating platelet aggregation and interfering with perfusion recovery in muscle ischemia and may represent a therapeutic target to improve limb salvage. 相似文献
6.
Zeh Lilli Limpens Juul Erhagen Björn Bragazza Luca Kalbitz Karsten 《Plant and Soil》2019,439(1-2):19-30
Plant and Soil - During historical yield improvement in soybean, breeders have seldom considered selection for root traits, generally focusing selection on yield traits. Yet, it is not known how... 相似文献
7.
Summary. Plants are able to synthesise all amino acids essential for human and animal nutrition. Because the concentrations of some
of these dietary constituents, especially methionine, lysine, and threonine, are often low in edible plant sources, research
is being performed to understand the physiological, biochemical, and molecular mechanisms that contribute to their transport,
synthesis and accumulation in plants. This knowledge can be used to develop strategies allowing a manipulation of crop plants,
eventually improving their nutritional quality.
This article is intended to serve two purposes. The first is to provide a brief review on the physiology of methionine synthesis
in higher plants. The second is to highlight some recent findings linked to the metabolism of methionine in plants due to
its regulatory influence on the aspartate pathway and its implication in plant growth. This information can be used to develop
strategies to improve methionine content of plants and to provide crops with a higher nutritional value.
Received January 28, 2000 Accepted March 3, 2000 相似文献
8.
Current status of antisense DNA methods in behavioral studies 总被引:4,自引:0,他引:4
The antisense DNA method has been used successfully to block the expression
of specific genes in vivo in neuronal systems. An increasing number of
studies in the last few years have shown that antisense DNA administered
directly into the brain can modify various kinds of behaviors. These
findings strongly suggest that the antisense DNA method can be used as a
powerful tool to study causal relationships between molecular processes in
the brain and behavior. In this article we review the current status of the
antisense method in behavioral studies and discuss its potentials and
problems by focusing on the following four aspects; (i) optimal application
paradigms of antisense DNA methods in behavioral studies; (ii) efficiencies
of different administration methods of antisense DNA used in behavioral
studies; (iii) determination of specificity of behavioral effects of
antisense DNA; and (iv) discrepancies between antisense DNA effects on
behaviors and those on protein levels of the targeted gene.
相似文献
9.
Transgenic mice are increasingly used for gene function and regulation studies of mammalian genes. A major limitation is the necessity to produce a large number of founder animals to obtain one line with the desired expression pattern. We developed a method, the 'double pronuclei injection', that doubles the yield of transgenic mouse lines obtained from each injection session, thereby reducing the time, effort and costs of generating transgenic mice. Three transgenic vectors were microinjected into the male and female pronuclei of zygotes. Approximately half of the resulting born mice were transgenic. This represented a 60% increase in the yield of founders per injected zygote, and a 100% increase in the yield of transgenic mice per born animal, when compared to yields obtained using single pronucleus injection. This method should prove useful for generating large numbers of transgenic mice for gene regulation studies and for conditional gene ablation 相似文献
10.
Collins Odhiambo Boaz Oyaro Richard Odipo Fredrick Otieno George Alemnji John Williamson Clement Zeh 《PloS one》2015,10(4)