全文获取类型
收费全文 | 977篇 |
免费 | 70篇 |
专业分类
1047篇 |
出版年
2023年 | 10篇 |
2022年 | 22篇 |
2021年 | 23篇 |
2020年 | 20篇 |
2019年 | 28篇 |
2018年 | 20篇 |
2017年 | 23篇 |
2016年 | 33篇 |
2015年 | 69篇 |
2014年 | 57篇 |
2013年 | 75篇 |
2012年 | 96篇 |
2011年 | 90篇 |
2010年 | 64篇 |
2009年 | 37篇 |
2008年 | 66篇 |
2007年 | 51篇 |
2006年 | 31篇 |
2005年 | 49篇 |
2004年 | 44篇 |
2003年 | 29篇 |
2002年 | 25篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 8篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1989年 | 3篇 |
1984年 | 2篇 |
1982年 | 4篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1969年 | 2篇 |
1967年 | 1篇 |
1966年 | 2篇 |
1965年 | 2篇 |
1963年 | 1篇 |
1958年 | 1篇 |
1954年 | 2篇 |
1944年 | 1篇 |
1935年 | 1篇 |
排序方式: 共有1047条查询结果,搜索用时 15 毫秒
261.
Repellent activity of plant essential oils against bites of Lutzomyia migonei (Diptera: Psychodidae)
Nieves E Fernández Méndez J Lias J Rondón M Briceño B 《Revista de biología tropical》2010,58(4):1549-1560
Natural repellents from plant extracts have demonstrated good efficacy against bites of some insect species. The present study evaluated the repellent effect of essential oils extracted from 8 plants species against bites of Lutzomyia migonei, the Leishmania vector. The essential oils were extracted by steam destillation in Clevenger chamber, from the following plants: Hyptis suaveolens, Pimenta racemosa, Piper marginatum, Monticalia imbricatifolia, Pseudognaphalium caeruleocanum, Espeletia shultzii, Plecthranthus amboinicus and Cinnamomun zeylanicum. Repellency tests were performed under laboratory conditions by the human hand method in cage assays, using female colonies of L. migonei. The more effective oils were tested at variable concentrations on different volunteers. The protection percentage and time were calculated. The results showed what oils of P. caeruleocanum and C. zeylanicum were the most effective. Although P. amboinicus oil also had repellent effect showed an irritant effect. The oils P. marginatum, H. suaveolens and P. racemosa showed no repellent effect, while the rest of oil extracts showed significant repellency in variable degrees. P. caeruleocanum and C. zeylanicum oils provided the 95% protection against bites of L. migonei for 3 h. The P. caeruleocanum oil showed the greatest protection time, with a mean over 4h and 3h at concentrations of 50% and 10% respectively. The results suggest that the P. caeruleocanum oil could represent a potential natural repellent against Leishmania vectors. 相似文献
262.
263.
Noguti EN Leite CQ Malaspina AC Santos AC Hirata RD Hirata MH Mamizuka EM Cardoso RF 《Memórias do Instituto Oswaldo Cruz》2010,105(6):779-785
The purpose of this study was to provide information about the genetic diversity and prevalent genotype of Mycobacterium tuberculosis in a low-endemic setting in northwestern state of Paraná in Southern Brazil. We employed spoligotyping and mycobacterial interspersed repetitive units-variable number tandem repeat (MIRU-VNTR) techniques to genotype M. tuberculos isisolates from patients with pulmonary tuberculosis (TB). The 93 isolates analyzed by spoligotyping were divided into 36 different patterns, 30 of which were described in the SITVIT database. Latin American and Mediterranean, Haarlem and T families were responsible for 26.9%, 17.2% and 11.8% of TB cases, respectively. From the 84 isolates analyzed by MIRU-VNTR, 58 shared a unique pattern and the remaining 26 belonged to nine clusters. The MIRU loci 40, 23, 10 and 16 were the most discriminatory. A combination of MIRU-VNTR and spoligotyping resulted in 85.7% discriminatory power (Hunter-Gaston index = 0.995). Thus, combining spoligotyping and MIRU-VNTR typing proved to be most useful for epidemiological study in this low-endemic setting in Southern Brazil. The current study demonstrated that there is significant diversity in circulating strains in the city of Maringá and the surrounding regions, with no single genotype of M. tuberculosis predominating. 相似文献
264.
Marta Gómez-Domenech Herminia García-Mozo Pura Alcázar Rui Brandao Elsa Caeiro Vinicius Munhoz Carmen Galán 《Aerobiologia》2010,26(2):149-155
The Coriolis δ air sampler is a new volumetric air sampler, dedicated to outdoor monitoring of airborne biological particles,
including pollen and spores. In the present work, the performance of the Coriolis in the collection of pollen grains was evaluated
in comparison with a Hirst spore trap, the most frequently used trap in aerobiological studies, in two cities of South Europe,
Evora (Portugal) and Córdoba (Spain). Both concentration values are compared, and statistical analysis was carried out. The
present study indicated that, in general, pollen counts for all taxa detected with the Hirst trap were higher than those detected
with the Coriolis δ in both cities. In Córdoba, significant differences were detected for all taxa except for Cupressus, Olea and Pinus, while in Evora significant differences were noted for all except Pinus and Poaceae. Differences were particularly marked in species flowering during April and May. In spite of theses differences,
Spearman correlation test results showed that the relationship between Hirst and Coriolis curves was always positive and significant
(p > 0.01). Regards to the number of detected taxa, the results showed greater diversity for the Hirst sampler in both cities. 相似文献
265.
Torres-Duque CA Díaz C Vargas L Serpa EM Mosquera W Garzón MC Mejía G García LM González LA Castro CM Ribón W 《Biomédica : revista del Instituto Nacional de Salud》2010,30(3):332-337
Rapidly growing mycobacteria are non-tuberculous mycobacteria amply present in the environment. Although they are not usually pathogenic for humans, they are opportunistic in that they can cause disease in people with disadvantageous conditions or who are immunocompromised. Mycobacterium peregrinum, an opportunistic, rapidly growing mycobacteria, belongs to the M. fortuitum group and has been reported as responsible for human cases of mycobacteriosis. A case of M. peregrinum type III is herein reported as the first in Colombia. It presented as a disseminated disease involving a prosthetic aortic valve (endocarditis) in a seventeen-year-old girl with a well-established diagnosis of prosthetic aortic valve endocarditis who was referred for a surgical replacement. Due to a congenital heart disease (subaortic stenosis with valve insufficiency), she had two previous aortic valve implantation surgeries. One year after the second implantation, the patient presented with respiratory symptoms and weight lost indicative of lung tuberculosis. A chest X-ray did not show parenchymal compromise but several Ziehl-Neelsen stains were positive. An echocardiography showed a vegetation on the prosthetic aortic valve. In blood and sputum samples, M. peregrinum type III was identified through culture, biochemical tests and hsp65 gene molecular analysis (PRA). The patient underwent a valve replacement and received a multidrug antimycobacterial treatment. Progressive recovery ensued and further samples from respiratory tract and blood were negative for mycobacteria. 相似文献
266.
Marco Schaudt Elsa Locardi Gunther Zischinsky Roland Stragies Jochen R. Pfeifer Christoph Gibson Dirk Scharn Uwe Richter Holger Kalkhof Klaus Dinkel Karsten Schnatbaum 《Bioorganic & medicinal chemistry letters》2010,20(3):1225-1228
The synthesis and SAR of two series of bradykinin B1 receptor antagonists is described. The benzamide moiety proved to be a suitable replacement for the aryl ester functionality of biaryl based antagonists. In addition, it was found that semicarbazides can effectively replace cyclopropyl amino acids. The compounds with the best overall profile were biaryl semicarbazides which display high antagonistic activity, low Caco-2 efflux and high oral bioavailability in the rat. 相似文献
267.
Background
The rate and fitness effects of mutations are key in understanding the evolution of every species. Traditionally, these parameters are estimated in mutation accumulation experiments where replicate lines are propagated in conditions that allow mutations to randomly accumulate without the purging effect of natural selection. These experiments have been performed with many model organisms but we still lack empirical estimates of the rate and effects of mutation in the protists. 相似文献268.
Elsa Lamy Gonçalo Graça Gonçalo da Costa Catarina Franco Fernando Capela e Silva Elvira Sales Baptista Ana Varela Coelho 《Proteome science》2010,8(1):65
Background
Previous studies suggested that dietary tannin ingestion may induce changes in mouse salivary proteins in addition to the primarily studied proline-rich proteins (PRPs). The aim of the present study was to determine the protein expression changes induced by condensed tannin intake on the fraction of mouse whole salivary proteins that are unable to form insoluble tannin-protein complexes. Two-dimensional polyacrylamide gel electrophoresis protein separation was used, followed by protein identification by mass spectrometry. 相似文献269.
Val��rie Vingtdeux Luca Giliberto Haitian Zhao Pallavi Chandakkar Qingli Wu James E. Simon Elsa M. Janle Jessica Lobo Mario G. Ferruzzi Peter Davies Philippe Marambaud 《The Journal of biological chemistry》2010,285(12):9100-9113
Alzheimer disease is an age-related neurodegenerative disorder characterized by amyloid-β (Aβ) peptide deposition into cerebral amyloid plaques. The natural polyphenol resveratrol promotes anti-aging pathways via the activation of several metabolic sensors, including the AMP-activated protein kinase (AMPK). Resveratrol also lowers Aβ levels in cell lines; however, the underlying mechanism responsible for this effect is largely unknown. Moreover, the bioavailability of resveratrol in the brain remains uncertain. Here we show that AMPK signaling controls Aβ metabolism and mediates the anti-amyloidogenic effect of resveratrol in non-neuronal and neuronal cells, including in mouse primary neurons. Resveratrol increased cytosolic calcium levels and promoted AMPK activation by the calcium/calmodulin-dependent protein kinase kinase-β. Direct pharmacological and genetic activation of AMPK lowered extracellular Aβ accumulation, whereas AMPK inhibition reduced the effect of resveratrol on Aβ levels. Furthermore, resveratrol inhibited the AMPK target mTOR (mammalian target of rapamycin) to trigger autophagy and lysosomal degradation of Aβ. Finally, orally administered resveratrol in mice was detected in the brain where it activated AMPK and reduced cerebral Aβ levels and deposition in the cortex. These data suggest that resveratrol and pharmacological activation of AMPK have therapeutic potential against Alzheimer disease. 相似文献
270.