全文获取类型
收费全文 | 837篇 |
免费 | 65篇 |
出版年
2022年 | 9篇 |
2021年 | 22篇 |
2020年 | 10篇 |
2019年 | 13篇 |
2018年 | 22篇 |
2017年 | 16篇 |
2016年 | 26篇 |
2015年 | 33篇 |
2014年 | 39篇 |
2013年 | 70篇 |
2012年 | 68篇 |
2011年 | 62篇 |
2010年 | 45篇 |
2009年 | 41篇 |
2008年 | 63篇 |
2007年 | 50篇 |
2006年 | 51篇 |
2005年 | 38篇 |
2004年 | 31篇 |
2003年 | 52篇 |
2002年 | 43篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1998年 | 10篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 3篇 |
1970年 | 3篇 |
1969年 | 4篇 |
1968年 | 2篇 |
1967年 | 3篇 |
1954年 | 1篇 |
1951年 | 1篇 |
1943年 | 1篇 |
排序方式: 共有902条查询结果,搜索用时 171 毫秒
891.
892.
Barbara Wicht Nadia Ruggeri-Bernardi Tetsuya Yanagida Minoru Nakao Raffaele Peduzzi Akira Ito 《Parasitology international》2010,59(1):35-39
Human diphyllobothriosis is caused by at least 14 species of cestodes belonging to the genus Diphyllobothrium. Molecular analysis by sequencing of nuclear and mitochondrial targets identifies some species at inter- and intra-specific level, and helps to reconstruct their phylogenetic relationships. Nevertheless, the suitability of further molecular targets deserves to be widened, and the comparison of samples of different geographical origin could allow their intra-specific characterization, which could also be useful for epidemiological purposes. In this study, we investigated inter- and intra-specific variability among tapeworms of the genus Diphyllobothrium, with focus on Diphyllobothrium latum, originated from Switzerland. Samples were analyzed by comparing the sequences of two nuclear and two mitochondrial DNA targets. We analyzed 27 samples belonging to 4 species (D. latum, Diphyllobothrium nihonkaiense, Diphyllobothrium dendriticum and Diphyllobothrium ditremum), 15 of which isolated from clinical cases (adults and eggs), 2 from wild canines, and 2 from fish of Swiss lakes (plerocercoid larvae); 8 samples of homologous species from other geographic origins were also sequenced and compared with the Swiss ones. Sequences of partial small subunit ribosomal RNA (18S rRNA) gene and partial internal transcribed spacers 1 and 2 (ITS1-2) were not useful even in inter-specific identification, whereas sequences of complete cytochrome c oxidase subunit 1 (cox1) and cytochrome b (cob) genes allowed us to assess inter- and intra-specific variations among the samples. Cox1 and cob could differentiate 3 and 5 haplotypes within the species D. latum. The results are discussed in the light of the anamneses provided by part of the patients. 相似文献
893.
894.
Florigio Lista Giovanni Faggioni Samina Valjevac Andrea Ciammaruconi Josée Vaissaire Claudine le Doujet Olivier Gorgé Riccardo De Santis Alessandra Carattoli Alessandra Ciervo Antonio Fasanella Francesco Orsini Raffaele D'Amelio Christine Pourcel Antonio Cassone Gilles Vergnaud 《BMC microbiology》2006,6(1):1-15
Background
There is an increasing interest to better understand endosymbiont capabilities in insects both from an ecological point of view and for pest control. Blochmannia floridanus provides important nutrients for its host, the ant Camponotus, while the bacterium in return is provided with a niche to proliferate. Blochmannia floridanus proteins and metabolites are difficult to study due to its endosymbiontic life style; however, its complete genome sequence became recently available. 相似文献895.
Kévin Drouet Cécile Jauzein Dominique Herviot-Heath Saeed Hariri Aitor Laza-Martinez Cyrielle Lecadet Martin Plus Sergio Seoane Marc Sourisseau Rodolphe Lemée Raffaele Siano 《Environmental microbiology》2021,23(9):4956-4979
In a future scenario of increasing temperatures in North-Atlantic waters, the risk associated with the expansion of the harmful, benthic dinoflagellate Ostreopsis cf. siamensis has to be evaluated and monitored. Microscopy observations and spatio-temporal surveys of environmental DNA (eDNA) were associated with Lagrangian particle dispersal simulations to: (i) establish the current colonization of the species in the Bay of Biscay, (ii) assess the spatial connectivity among sampling zones that explain this distribution, and (iii) identify the sentinel zones to monitor future expansion. Throughout a sampling campaign carried out in August to September 2018, microscope analysis showed that the species develops in the south-east of the bay where optimal temperatures foster blooms. Quantitative PCR analyses revealed its presence across almost the whole bay to the western English Channel. An eDNA time-series collected on plastic samplers showed that the species occurs in the bay from April to September. Due to the water circulation, colonization of the whole bay from the southern blooming zones is explained by inter-site connectivity. Key areas in the middle of the bay permit continuous dispersal connectivity towards the north. These key areas are proposed as sentinel zones to monitor O. cf. siamensis invasions towards the presumably warming water of the North-East Atlantic. 相似文献
896.
Raffaele Saladino Claudia Crestini Fabiana Ciciriello Giovanna Costanzo Ernesto Di Mauro 《Origins of life and evolution of the biosphere》2006,36(5-6):523-531
Formamide NH2CHO chemistry provides a unitary frame into which several pieces of the origin-of-life puzzle may be adjusted. Synthetic processes
were uncovered which, starting from formamide and prebiotically easily available common catalysts, yield all the necessary
nucleic bases precursors, including acyclonucleosides. Formamide allows phosphorylations and trans-phosphorylations, favours
the micellar aggregation of surfactants and, most importantly, determines conditions in which the formation of nucleic polymers
is thermodynamically favoured. In the detected conditions, the phosphoester bonds are more stable in the polymeric than in
the monomeric form, thus allowing formation and survival of informational nucleic polymers.
Presented at: National Workshop on Astrobiology: Search for Life in the Solar System, Capri, Italy, 26 to 28 October, 2005. 相似文献
897.
Raffaele Porta Marina Camardella Vittorio Gentile Antonio De Santis 《Journal of neurochemistry》1984,42(2):321-325
Since a specific inhibition of cerebral spermidine (Spd) synthase activity by alicyclic amines was preliminarily observed in vitro, we examined the in vivo inhibitory effectiveness of dicyclohexylamine (DCHA) on Spd biosynthesis in 21-day-old rat brain. For this purpose a previously reported HPLC procedure (Porta et al., 1981a) was modified to analyze the cerebral levels of DCHA at the time of polyamine determinations. The intraperitoneally injected DCHA was shown to cross the blood-brain barrier easily, reaching high levels in the cerebral tissue (approximately 750 nmol/g brain) within 1 h of its administration. The effect of the drug on the polyamine metabolism resulted in a significant depletion of Spd biosynthesis from the sixth hour after the treatment and in an earlier and prolonged increase of the putrescine (Pt) steady-state levels. Conversely, the spermine (Spm) endogenous pools remained unchanged throughout the 24-h post-DCHA period. Moreover, following the intracerebral administration of [1,4-14C]Pt, significantly lower specific radioactivity (s.r.a.) values for labeled Pt and Spd were recorded in the brains of DCHA-treated animals. Conversely, after intracerebral [14C]Spd injection, the s.r.a. of newly formed [14C]Spm remained unchanged, confirming the specificity of the DCHA effect on the Spd biosynthesis. 相似文献
898.
Silvio Matassa Pascal Boeckx Jos Boere Jan Willem Erisman Miao Guo Raffaele Manzo Francis Meerburg Stefano Papirio Ilje Pikaar Korneel Rabaey Diederik Rousseau Jerald Schnoor Peter Smith Erik Smolders Stefan Wuertz Willy Verstraete 《Microbial biotechnology》2023,16(1):15-27
Nitrogen is the most crucial element in the production of nutritious feeds and foods. The production of reactive nitrogen by means of fossil fuel has thus far been able to guarantee the protein supply for the world population. Yet, the production and massive use of fertilizer nitrogen constitute a major threat in terms of environmental health and sustainability. It is crucial to promote consumer acceptance and awareness towards proteins produced by highly effective microorganisms, and their potential to replace proteins obtained with poor nitrogen efficiencies from plants and animals. The fact that reactive fertilizer nitrogen, produced by the Haber Bosch process, consumes a significant amount of fossil fuel worldwide is of concern. Moreover, recently, the prices of fossil fuels have increased the cost of reactive nitrogen by a factor of 3 to 5 times, while international policies are fostering the transition towards a more sustainable agro-ecology by reducing mineral fertilizers inputs and increasing organic farming. The combination of these pressures and challenges opens opportunities to use the reactive nitrogen nutrient more carefully. Time has come to effectively recover used nitrogen from secondary resources and to upgrade it to a legal status of fertilizer. Organic nitrogen is a slow-release fertilizer, it has a factor of 2.5 or higher economic value per unit nitrogen as fertilizer and thus adequate technologies to produce it, for instance by implementing photobiological processes, are promising. Finally, it appears wise to start the integration in our overall feed and food supply chains of the exceptional potential of biological nitrogen fixation. Nitrogen produced by the nitrogenase enzyme, either in the soil or in novel biotechnology reactor systems, deserves to have a ‘renaissance’ in the context of planetary governance in general and the increasing number of people who desire to be fed in a sustainable way in particular. 相似文献
899.
900.
Raffaele Nicastro Serena Raucci Agns H. Michel Michael Stumpe Guillermo Miguel Garcia Osuna Malika Jaquenoud Benoît Kornmann Claudio De Virgilio 《PLoS genetics》2021,17(3)
Indole-3-acetic acid (IAA) is the most common, naturally occurring phytohormone that regulates cell division, differentiation, and senescence in plants. The capacity to synthesize IAA is also widespread among plant-associated bacterial and fungal species, which may use IAA as an effector molecule to define their relationships with plants or to coordinate their physiological behavior through cell-cell communication. Fungi, including many species that do not entertain a plant-associated life style, are also able to synthesize IAA, but the physiological role of IAA in these fungi has largely remained enigmatic. Interestingly, in this context, growth of the budding yeast Saccharomyces cerevisiae is sensitive to extracellular IAA. Here, we use a combination of various genetic approaches including chemical-genetic profiling, SAturated Transposon Analysis in Yeast (SATAY), and genetic epistasis analyses to identify the mode-of-action by which IAA inhibits growth in yeast. Surprisingly, these analyses pinpointed the target of rapamycin complex 1 (TORC1), a central regulator of eukaryotic cell growth, as the major growth-limiting target of IAA. Our biochemical analyses further demonstrate that IAA inhibits TORC1 both in vivo and in vitro. Intriguingly, we also show that yeast cells are able to synthesize IAA and specifically accumulate IAA upon entry into stationary phase. Our data therefore suggest that IAA contributes to proper entry of yeast cells into a quiescent state by acting as a metabolic inhibitor of TORC1. 相似文献