全文获取类型
收费全文 | 76篇 |
免费 | 11篇 |
出版年
2017年 | 1篇 |
2016年 | 2篇 |
2015年 | 4篇 |
2014年 | 1篇 |
2013年 | 5篇 |
2012年 | 5篇 |
2011年 | 3篇 |
2010年 | 4篇 |
2009年 | 5篇 |
2008年 | 6篇 |
2007年 | 3篇 |
2006年 | 5篇 |
2005年 | 4篇 |
2003年 | 2篇 |
2002年 | 5篇 |
2001年 | 6篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1988年 | 2篇 |
1985年 | 1篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1978年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有87条查询结果,搜索用时 31 毫秒
71.
72.
MYRIAM GAUDEUL IRÈNE TILL-BOTTRAUD 《Biological journal of the Linnean Society. Linnean Society of London》2008,93(4):667-677
We investigated the genetic structure of Eryngium alpinum (Apiaceae) in an Alpine valley where the plant occurs in patches of various sizes. In a conservation perspective, our goal was to determine whether the valley consists of one or several genetic units. Habitat fragmentation and previous observations of restricted pollen/seed dispersal suggested pronounced genetic structure, but gene dispersal often follows a leptokurtic distribution, which may lead to weak genetic structure. We used nine microsatellite loci and two nested sampling designs (50 × 50 m grid throughout the valley and 2 × 2 m grid in two 50 × 10 m quadrats). Within the overall valley, F -statistics and Bayesian approaches indicated high genetic homogeneity. This result might be explained by: (1) underestimation of long-distance pollen/seed dispersal by in situ experiments and (2) too recent fragmentation events to build up genetic structure. Spatial autocorrelation revealed isolation by distance on the overall valley but this pattern was much more pronounced in the 50 × 10 m quadrats sampled with a 2-m mesh. This was probably associated with limited primary seed dispersal, leading to the spatial clustering of half-sibs around maternal plants. We emphasize the interest of nested sampling designs and of combining several statistical tools. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 667–677. 相似文献
73.
CHRISTOPHER R. TRACY KEITH A. CHRISTIAN NICOLE BURNIP BEAU J. AUSTIN ALYSSA CORNALL SEBASTIAN IGLESIAS STEPHEN J. REYNOLDS THOMAS TIXIER CAMILLE LE NOËNE 《Austral ecology》2013,38(4):476-483
Amphibians are typically intolerant of high temperatures and dehydrating conditions, and small species are particularly susceptible to desiccation. The rockhole frog, Litoria meiriana (Hylidae), is diurnal and is often observed on rocks in the sun near streams in tropical Australia. These hot, desiccating conditions are avoided by most frog species. We measured the microclimate in the areas used by frogs and the activity, body temperatures and hydric state of free‐ranging individuals of this small frog. We also used plaster models to further explore the dynamic nature of hydric state by combining estimates of water loss and water uptake with behavioural observations of activity and microhabitat selection. Both direct measures and estimates of dynamic hydric state indicated that free‐ranging frogs generally maintained a hydric state above 95% of full hydration, but occasionally, particularly during the afternoon, frogs allowed their hydric state to fall as low as 85%. Body temperatures of frogs remained below the critical thermal maximum (CTmax) even when the frogs were in the sun, because this species has no cutaneous resistance to evaporative water loss and so they cool by evaporation. However, during the hotter part of the day, on dry sunny substrates, the hydric state of the frogs could fall to near lethal hydration states (approximately 70% of full hydration) within a short period (approximately 20 min). Thus, the threat of desiccation appears to be more limiting than the threat of overheating. These diurnal frogs rely on frequent bouts of rehydration to support their ability to venture onto hot, dry rocks during the day. 相似文献
74.
Xiaomin Su Yaping Chu Jeffrey H. Kordower Bin Li Hong Cao Liang Huang Maki Nishida Lei Song Difei Wang Howard J. Federoff 《PloS one》2015,10(8)
The etiopathogenesis of sporadic Parkinson’s disease (PD) remains elusive although mitochondrial dysfunction has long been implicated. Recent evidence revealed reduced expression of peroxisome proliferator-activated receptor gamma coactivator−1 α (PGC−1α) and downstream regulated nuclear encoded respiratory complex genes in affected brain tissue from PD patients. We sought to determine whether epigenetic modification of the PGC−1α gene could account for diminished expression. In substantia nigra from PD patients but not control subjects, we show significant promoter-proximal non-canonical cytosine methylation of the PGC−1α gene but not an adjacent gene. As neuroinflammation is a prominent feature of PD and a mediator of epigenetic change, we evaluated whether the pro-inflammatory fatty acid, palmitate, would stimulate PGC−1α promoter methylation in different cell types from the CNS. Indeed, in mouse primary cortical neurons, microglia and astrocytes, palmitate causes PGC−1α gene promoter non-canonical cytosine methylation, reduced expression of the gene and reduced mitochondrial content. Moreover, intracerebroventricular (ICV) injection of palmitate to transgenic human α−synuclein mutant mice resulted in increased PGC−1α promoter methylation, decreased PGC−1α expression and reduced mitochondrial content in substantia nigra. Finally we provide evidence that dysregulation of ER stress and inflammatory signaling is associated with PGC−1α promoter methylation. Together, these data strengthen the connection between saturated fatty acids, neuroflammation, ER stress, epigenetic alteration and bioenergetic compromise in PD. 相似文献
75.
76.
White SM Renda M Nam NY Klimatcheva E Zhu Y Fisk J Halterman M Rimel BJ Federoff H Pandya S Rosenblatt JD Planelles V 《Journal of virology》1999,73(4):2832-2840
Lentivirus vectors based on human immunodeficiency virus (HIV) type 1 (HIV-1) constitute a recent development in the field of gene therapy. A key property of HIV-1-derived vectors is their ability to infect nondividing cells. Although high-titer HIV-1-derived vectors have been produced, concerns regarding safety still exist. Safety concerns arise mainly from the possibility of recombination between transfer and packaging vectors, which may give rise to replication-competent viruses with pathogenic potential. We describe a novel lentivirus vector which is based on HIV, simian immunodeficiency virus (SIV), and vesicular stomatitis virus (VSV) and which we refer to as HIV/SIVpack/G. In this system, an HIV-1-derived genome is encapsidated by SIVmac core particles. These core particles are pseudotyped with VSV glycoprotein G. Because the nucleotide homology between HIV-1 and SIVmac is low, the likelihood of recombination between vector elements should be reduced. In addition, the packaging construct (SIVpack) for this lentivirus system was derived from SIVmac1A11, a nonvirulent SIV strain. Thus, the potential for pathogenicity with this vector system is minimal. The transduction ability of HIV/SIVpack/G was demonstrated with immortalized human lymphocytes, human primary macrophages, human bone marrow-derived CD34(+) cells, and primary mouse neurons. To our knowledge, these experiments constitute the first demonstration that the HIV-1-derived genome can be packaged by an SIVmac capsid. We demonstrate that the lentivirus vector described here recapitulates the biological properties of HIV-1-derived vectors, although with increased potential for safety in humans. 相似文献
77.
In vivo interleukin-2 gene therapy of established tumors with herpes simplex amplicon vectors 总被引:2,自引:0,他引:2
D'Angelica M Karpoff H Halterman M Ellis J Klimstra D Edelstein D Brownlee M Federoff H Fong Y 《Cancer immunology, immunotherapy : CII》1999,47(5):265-271
In vivo cytokine gene transfer may greatly simplify autologous tumor vaccine production. Herpes simplex viral amplicon vectors
(HSV) are efficient gene-transfer vehicles and may overcome many limitations of prior gene-transfer methods. The interleukin-2
(IL-2) and β-galactosidase genes (lac) were inserted into an HSV amplicon vector and tested in a subcutaneous squamous cell carcinoma of lung origin to determine
the efficiency of in vivo gene transfer and the utility of such a direct gene-transfer approach in cancer therapy. Gene transfer
and expression were assessed by histochemical staining and enzyme-linked immunosorbent assay (ELISA). Growth of injected tumors
as well as non-injected tumors remote from the site of injection was assessed. Assessment of lymphocytic infiltrates into
tumors was performed by immunohistochemistry. Survival was recorded. Direct in vivo injection of established tumors with a
HSVil2 resulted in efficient gene transfer and production of IL-2 in the injected tumor but not at tumors remote from the
sites of injection. There was a significant suppression of growth of the tumors injected with HSVil2 (P < 0.01) when compared with tumors injected with HSV without il2. Of note, growth of tumors remote from sites of HSVil2 injection
was also retarded and treatment was associated with a significant (P < 0.05) improvement in survival. Direct intratumoral administration of HSV amplicon vectors can result in efficient transfer
of cytokine genes and have antitumor efficacy. HSV vectors are therefore potentially useful agents in such in vivo gene-therapy
strategies and simplify cytokine antitumor gene-therapy strategies.
Received: 19 June 1998 / Accepted: 25 September 1998 相似文献
78.
黑龙江东部双鸭山、集贤煤田中生代含煤地层研究* 总被引:6,自引:1,他引:5
th Exploring Team NE China-Nei Monggol Coal Corporation Shuangyashan Heilongjiang 《古生物学报》1992,31(2):129-162
本文系统地讨论了黑龙江双鸭山、集贤两煤田的中生代含煤地层序列,综合各门类化石研究结果,认为海相的绥滨组和东荣组属晚侏罗世卡洛夫晚期至伏尔加期,非海相的城子河组和穆棱组属早白垩世尼坎期。文内提供11条详细的钻探剖面的生物地层资料。 相似文献
79.
LAURÉNE GAY PAUL E. EADY RAM VASUDEV DAVID J. HOSKEN TOM TREGENZA 《Physiological Entomology》2009,34(1):86-92
Abstract The optimal number of mating partners for females rarely coincides with that for males, leading to sexual conflict over mating frequency. In the bruchid beetle Callosobruchus maculatus, the fitness consequences to females of engaging in multiple copulations are complex, with studies demonstrating both costs and benefits to multiple mating. However, females kept continuously with males have a lower lifetime egg production compared with females mated only once and then isolated from males. This reduction in fitness may be a result of damage caused by male genitalia, which bear spines that puncture the female’s reproductive tract, and/or toxic elements in the ejaculate. However, male harassment rather than costs of matings themselves could also explain the results. In the present study, the fitness costs of male harassment for female C. maculatus are estimated. The natural refractory period of females immediately after their first mating is used to separate the cost of harassment from the cost of mating. Male harassment results in females laying fewer eggs and this results in a tendency to produce fewer offspring. The results are discussed in the context of mate choice and sexual selection. 相似文献
80.
Yan Li Seung Lim David Hoffman Pontus Aspenstrom Howard J. Federoff David A. Rempe 《The Journal of cell biology》2009,185(6):1065-1081
Mitochondrial transport is critical for maintenance of normal neuronal function. Here, we identify a novel mitochondria protein, hypoxia up-regulated mitochondrial movement regulator (HUMMR), which is expressed in neurons and is markedly induced by hypoxia-inducible factor 1 α (HIF-1α). Interestingly, HUMMR interacts with Miro-1 and Miro-2, mitochondrial proteins that are critical for mediating mitochondrial transport. Interestingly, knockdown of HUMMR or HIF-1 function in neurons exposed to hypoxia markedly reduces mitochondrial content in axons. Because mitochondrial transport and distribution are inextricably linked, the impact of reduced HUMMR function on the direction of mitochondrial transport was also explored. Loss of HUMMR function in hypoxia diminished the percentage of motile mitochondria moving in the anterograde direction and enhanced the percentage moving in the retrograde direction. Thus, HUMMR, a novel mitochondrial protein induced by HIF-1 and hypoxia, biases mitochondria transport in the anterograde direction. These findings have broad implications for maintenance of neuronal viability and function during physiological and pathological states. 相似文献