全文获取类型
收费全文 | 208篇 |
免费 | 13篇 |
出版年
2021年 | 2篇 |
2020年 | 4篇 |
2018年 | 3篇 |
2016年 | 2篇 |
2015年 | 4篇 |
2014年 | 7篇 |
2013年 | 14篇 |
2012年 | 14篇 |
2011年 | 11篇 |
2010年 | 2篇 |
2009年 | 6篇 |
2008年 | 8篇 |
2007年 | 3篇 |
2006年 | 5篇 |
2005年 | 6篇 |
2004年 | 8篇 |
2003年 | 6篇 |
2002年 | 7篇 |
2001年 | 7篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1996年 | 2篇 |
1994年 | 2篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1988年 | 4篇 |
1987年 | 11篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1971年 | 1篇 |
1970年 | 4篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1967年 | 2篇 |
1966年 | 2篇 |
1951年 | 1篇 |
1938年 | 1篇 |
1858年 | 1篇 |
排序方式: 共有221条查询结果,搜索用时 15 毫秒
71.
Jessica K. Leet Casey D. Lindberg Luke A. Bassett Gregory M. Isales Krystle L. Yozzo Tara D. Raftery David C. Volz 《PloS one》2014,9(8)
Using transgenic zebrafish (fli1:egfp) that stably express enhanced green fluorescent protein (eGFP) within vascular endothelial cells, we recently developed and optimized a 384-well high-content screening (HCS) assay that enables us to screen and identify chemicals affecting cardiovascular development and function at non-teratogenic concentrations. Within this assay, automated image acquisition procedures and custom image analysis protocols are used to quantify body length, heart rate, circulation, pericardial area, and intersegmental vessel area within individual live embryos exposed from 5 to 72 hours post-fertilization. After ranking developmental toxicity data generated from the U.S. Environmental Protection Agency''s (EPA''s) zebrafish teratogenesis assay, we screened 26 of the most acutely toxic chemicals within EPA''s ToxCast Phase-I library in concentration-response format (0.05–50 µM) using this HCS assay. Based on this screen, we identified butafenacil as a potent inducer of anemia, as exposure from 0.39 to 3.125 µM butafenacil completely abolished arterial circulation in the absence of effects on all other endpoints evaluated. Butafenacil is an herbicide that inhibits protoporphyrinogen oxidase (PPO) – an enzyme necessary for heme production in vertebrates. Using o-dianisidine staining, we then revealed that severe butafenacil-induced anemia in zebrafish was due to a complete loss of hemoglobin following exposure during early development. Therefore, six additional PPO inhibitors within the ToxCast Phase-I library were screened to determine whether anemia represents a common adverse outcome for these herbicides. Embryonic exposure to only one of these PPO inhibitors – flumioxazin – resulted in a similar phenotype as butafenacil, albeit not as severe as butafenacil. Overall, this study highlights the potential utility of this assay for (1) screening chemicals for cardiovascular toxicity and (2) prioritizing chemicals for future hypothesis-driven and mechanism-focused investigations within zebrafish and mammalian models. 相似文献
72.
Petra van den Doel Asisa Volz Jouke M. Roose Varsha D. Sewbalaksing Gorben P. Pijlman Ingeborg van Middelkoop Vincent Duiverman Eva van de Wetering Gerd Sutter Albert D. M. E. Osterhaus Byron E. E. Martina 《PLoS neglected tropical diseases》2014,8(9)
Chikungunya virus (CHIKV) infection is characterized by rash, acute high fever, chills, headache, nausea, photophobia, vomiting, and severe polyarthralgia. There is evidence that arthralgia can persist for years and result in long-term discomfort. Neurologic disease with fatal outcome has been documented, although at low incidences. The CHIKV RNA genome encodes five structural proteins (C, E1, E2, E3 and 6K). The E1 spike protein drives the fusion process within the cytoplasm, while the E2 protein is believed to interact with cellular receptors and therefore most probably constitutes the target of neutralizing antibodies. We have constructed recombinant Modified Vaccinia Ankara (MVA) expressing E3E2, 6KE1, or the entire CHIKV envelope polyprotein cassette E3E26KE1. MVA is an appropriate platform because of its demonstrated clinical safety and its suitability for expression of various heterologous proteins. After completing the immunization scheme, animals were challenged with CHIV-S27. Immunization of AG129 mice with MVAs expressing E2 or E3E26KE1 elicited neutralizing antibodies in all animals and provided 100% protection against lethal disease. In contrast, 75% of the animals immunized with 6KE1 were protected against lethal infection. In conclusion, MVA expressing the glycoprotein E2 of CHIKV represents as an immunogenic and effective candidate vaccine against CHIKV infections. 相似文献
73.
Volz K 《Structure (London, England : 1993)》2002,10(5):602-603
In this issue of Structure, Blanco et al. describe the first structure of a two-component response regulator effector domain bound to its target DNA, showing novel tandem binding to successive direct repeat sequences of pho boxes from the phoA operon promotor. 相似文献
74.
Angrisano F Riglar DT Sturm A Volz JC Delves MJ Zuccala ES Turnbull L Dekiwadia C Olshina MA Marapana DS Wong W Mollard V Bradin CH Tonkin CJ Gunning PW Ralph SA Whitchurch CB Sinden RE Cowman AF McFadden GI Baum J 《PloS one》2012,7(2):e32188
Actin dynamics have been implicated in a variety of developmental processes during the malaria parasite lifecycle. Parasite motility, in particular, is thought to critically depend on an actomyosin motor located in the outer pellicle of the parasite cell. Efforts to understand the diverse roles actin plays have, however, been hampered by an inability to detect microfilaments under native conditions. To visualise the spatial dynamics of actin we generated a parasite-specific actin antibody that shows preferential recognition of filamentous actin and applied this tool to different lifecycle stages (merozoites, sporozoites and ookinetes) of the human and mouse malaria parasite species Plasmodium falciparum and P. berghei along with tachyzoites from the related apicomplexan parasite Toxoplasma gondii. Actin filament distribution was found associated with three core compartments: the nuclear periphery, pellicular membranes of motile or invasive parasite forms and in a ring-like distribution at the tight junction during merozoite invasion of erythrocytes in both human and mouse malaria parasites. Localisation at the nuclear periphery is consistent with an emerging role of actin in facilitating parasite gene regulation. During invasion, we show that the actin ring at the parasite-host cell tight junction is dependent on dynamic filament turnover. Super-resolution imaging places this ring posterior to, and not concentric with, the junction marker rhoptry neck protein 4. This implies motor force relies on the engagement of dynamic microfilaments at zones of traction, though not necessarily directly through receptor-ligand interactions at sites of adhesion during invasion. Combined, these observations extend current understanding of the diverse roles actin plays in malaria parasite development and apicomplexan cell motility, in particular refining understanding on the linkage of the internal parasite gliding motor with the extra-cellular milieu. 相似文献
75.
76.
77.
Background
There is evidence that interventions aiming at modulation of the motor cortex activity lead to pain reduction. In order to understand further the role of the motor cortex on pain modulation, we aimed to compare the behavioral (pressure pain threshold) and neurophysiological effects (transcranial magnetic stimulation (TMS) induced cortical excitability) across three different motor tasks.Methodology/Principal Findings
Fifteen healthy male subjects were enrolled in this randomized, controlled, blinded, cross-over designed study. Three different tasks were tested including motor learning with and without visual feedback, and simple hand movements. Cortical excitability was assessed using single and paired-pulse TMS measures such as resting motor threshold (RMT), motor-evoked potential (MEP), intracortical facilitation (ICF), short intracortical inhibition (SICI), and cortical silent period (CSP). All tasks showed significant reduction in pain perception represented by an increase in pressure pain threshold compared to the control condition (untrained hand). ANOVA indicated a difference among the three tasks regarding motor cortex excitability change. There was a significant increase in motor cortex excitability (as indexed by MEP increase and CSP shortening) for the simple hand movements.Conclusions/Significance
Although different motor tasks involving motor learning with and without visual feedback and simple hand movements appear to change pain perception similarly, it is likely that the neural mechanisms might not be the same as evidenced by differential effects in motor cortex excitability induced by these tasks. In addition, TMS-indexed motor excitability measures are not likely good markers to index the effects of motor-based tasks on pain perception in healthy subjects as other neural networks besides primary motor cortex might be involved with pain modulation during motor training. 相似文献78.
Summary Four methods based upon the periodic acid—phenylhydrazine—Schiff reaction have been developed for the simultaneous visualization of neutral sugars with periodate oxidizablevicinal diols (hexose, 6-deoxyhexose,N-acetylhexosamine) and either sialic acids or side chainO-acyl sialic acids. In the first of these procedures, the saponification—periodic acid oxidation—2,4-dinitrophenylhydrazine—Azure A—Schiff—saponification (KOH—PA—DNPH—Az—KOH) method, all sialic acids stain Azure blue, neutral sugars with oxidizablevicinal diols stain yellow and mixtures of such components stain in various shades of green. In the second technique, periodic acid oxidation—2,4-dinitrophenylhydrazine—Azure A Schiff—saponification (PA—DNPH—Az—KOH), Azure Blue staining is confined to sialic acids without side chain substituents or which have anO-acyl substituent at position C7, while in the third method, the selective periodate oxidation—borohydride reduction—saponification—periodic acid oxidation—2,4-dinitrophenyl hydrazine—Azure A—Schiff—saponification (PA*—Bh—KOH—PA—DNPH—Az—KOH) technique, only sialic acids withO-acyl substituents at positions C7, C8 or C9 (or which have two or threeO-acyl side chain substituents) stain Azure blue. Finally in the fourth procedure, periodic acid oxidation—2,4-dinitrophenylhydrazine—Azure A—Schiff—saponification—borohydride reduction—periodic acid oxidation—Schiff (PA—DNPH—Az—KOH—Bh—PAS), sialic acids without side chain substituents or which haveO-acyl substituents at C7 stain Azure blue, sialic acids substituted at position C8 or C9 (or which are di- or tri-substituted) stain magenta and neutral sugars stain yellow. Where mixtures of these components are present, a wide range of colours is obtained. 相似文献
79.
Dissemination of yeasts after gastrointestinal inoculation in antibiotic-treated mice 总被引:4,自引:0,他引:4
Mice pretreated with antibiotics were inoculated intragastrically with different yeast isolates to determine whether the resulting disruption of the normal flora ecology would allow certain fungi to colonize and disseminate from the gastrointestinal tract. Antibiotic treatment decreased the total population levels of the indigenous bacterial flora, and predisposed mice to gastrointestinal overgrowth and subsequent dissemination by Candida albicans, C. parapsilosis, C. pseudotropicalis, C. tropicalis, and Torulopsis glabrata. A clinical isolate of Rhodotorula rubra, on the other hand, was unable to maintain a stable population in the gut of similar mice and could not be isolated from systemic organs. Control animals not receiving antibiotic therapy, challenged with C. albicans, showed significantly lower gut population levels of yeasts, and Candida organisms could not be grown from visceral organs. It is suggested that suppression of fungi within the gastrointestinal tract by members of the normal bacterial flora may be an important mechanism whereby fungi are confined to the alimentary tract. 相似文献
80.
Hans-Albert Kolb 《生物化学与生物物理学报:生物膜》1980,600(3):986-992
For pores which can adopt only the open and closed states, the influence of the amplitude distribution of the single-pore conductance (γ, open state) on the covariance function is derived. It is shown that reliable mean values of γ (E(γ)) can be derived from noise analysis only if the variance in the amplitude distribution (σγ2) is known. In the past, σγ2 was set always to zero, leading to an overestimation of E(γ). In the case of gramicidin-doped lipid bilayer membranes, this overestimation amounts to as much as 15% of the true value of E(γ). 相似文献