全文获取类型
收费全文 | 631篇 |
免费 | 28篇 |
专业分类
659篇 |
出版年
2022年 | 2篇 |
2021年 | 6篇 |
2020年 | 5篇 |
2019年 | 4篇 |
2018年 | 17篇 |
2017年 | 10篇 |
2016年 | 24篇 |
2015年 | 27篇 |
2014年 | 24篇 |
2013年 | 45篇 |
2012年 | 54篇 |
2011年 | 42篇 |
2010年 | 28篇 |
2009年 | 25篇 |
2008年 | 32篇 |
2007年 | 32篇 |
2006年 | 38篇 |
2005年 | 35篇 |
2004年 | 25篇 |
2003年 | 22篇 |
2002年 | 23篇 |
2001年 | 22篇 |
2000年 | 9篇 |
1999年 | 8篇 |
1998年 | 11篇 |
1997年 | 3篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 7篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 1篇 |
1981年 | 8篇 |
1980年 | 1篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1969年 | 2篇 |
1965年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有659条查询结果,搜索用时 15 毫秒
601.
Beatriz Escudero Daniel Lucas Carmen Albo Suveera Dhup Jeff W. Bacher Aránzazu Sánchez-Mu?oz Margarita Fernández José Rivera-Torres Rosa M. Carmona Encarnación Fuster Candelas Carreiro Raquel Bernad Manuel A. González Vicente Andrés Luis Blanco Enrique Roche Isabel Fabregat Enrique Samper Antonio Bernad 《PloS one》2014,9(4)
602.
Summary A new species of fungus of the genusCoelomomyces, C. ciferrii has been found as endoparasites ofPhlebotomus eggs at Belo Horizonte, Minas Gerais, State in Brazil. It is the first time that the genusCoelomomyces is found in Brasil.The morphological characters of the new species are distinct from other species described. 相似文献
603.
Heidy Peidro-Guzmán Yordanis Pérez-Llano Deborah González-Abradelo Maikel Gilberto Fernández-López Sonia Dávila-Ramos Elisabet Aranda Darío Rafael Olicón Hernández Angélica Ortega García Verónica Lira-Ruan Oscar Ramírez Pliego María Angélica Santana Denhi Schnabel Irina Jiménez-Gómez Rosa R. Mouriño-Pérez Elva T. Aréchiga-Carvajal María del Rayo Sánchez-Carbente Jorge Luis Folch-Mallol Ayixon Sánchez-Reyes Vinoth Kumar Vaidyanathan Hubert Cabana Nina Gunde-Cimerman Ramón Alberto Batista-García 《Environmental microbiology》2021,23(7):3435-3459
604.
605.
Botelho TO Guevara T Marrero A Arêde P Fluxà VS Reymond JL Oliveira DC Gomis-Rüth FX 《The Journal of biological chemistry》2011,286(29):25697-25709
HmrA is an antibiotic resistance factor of methicillin-resistant Staphylococcus aureus. Molecular analysis of this protein revealed that it is not a muramidase or β-lactamase but a nonspecific double-zinc endopeptidase consisting of a catalytic domain and an inserted oligomerization domain, which probably undergo a relative interdomain hinge rotation upon substrate binding. The active-site cleft is located at the domain interface. Four HmrA protomers assemble to a large ∼170-kDa homotetrameric complex of 125 Å. All four active sites are fully accessible and ∼50–70 Å apart, far enough apart to act on a large meshwork substrate independently but simultaneously. In vivo studies with four S. aureus strains of variable resistance levels revealed that the extracellular addition of HmrA protects against loss of viability in the presence of oxacillin and that this protection depends on proteolytic activity. All of these results indicate that HmrA is a peptidase that participates in resistance mechanisms in vivo in the presence of β-lactams. Furthermore, our results have implications for most S. aureus strains of known genomic sequences and several other cocci and bacilli, which harbor close orthologs. This suggests that HmrA may be a new widespread antibiotic resistance factor in bacteria. 相似文献
606.
607.
Cristian Arévalo Juanita Freer Pamela A. Naulin Nelson P. Barrera Eduardo Troncoso Juan Araya Carlos Peña-Farfal Rosario del P. Castillo 《Bioenergy Research》2017,10(3):714-727
Dilute acid hydrolysis (DAH) and auto-hydrolysis (AU) have demonstrated to be optimal pre-treatments for the generation of biofuels from wood. Recent studies have highlighted the importance of ensuring the accessibility of cellulose enzymes during the enzymatic hydrolysis (EH) of pre-treated materials. In this work, the microscopic and nanoscopic structures of Eucalyptus globulus samples pre-treated by AU and DAH were evaluated by different techniques to understand the effect of the ultrastructure of samples on the enzymatic conversion and cellulose accessibility for bioethanol production. Microscopic techniques revealed changes in the physical characteristics of pre-treated fibers, coalescence at microscopic level, and differences in the chemical distribution of lignocellulosic components depending on the severity and type of pre-treatment. The atomic force microscopy-based nanoscopic study of samples showed differences in the effect of the pre-treatments on the ultrastructure of samples, with DAH pre-treatment producing major changes in the secondary cell wall with respect to AU samples at comparable severities, and a positive effect of the DAH ultrastructure changes to increase the EH yield. 相似文献
608.
Deseada Parejo Jesús M. Avilés Aránzazu Pe?a Lourdes Sánchez Francisca Ruano Carmen Zamora-Mu?oz Manuel Martín-Vivaldi 《PloS one》2013,8(7)
Chemical defences against predators are widespread in the animal kingdom although have been seldom reported in birds. Here, we investigate the possibility that the orange liquid that nestlings of an insectivorous bird, the Eurasian roller (Coracias garrulus), expel when scared at their nests acts as a chemical defence against predators. We studied the diet of nestling rollers and vomit origin, its chemical composition and deterrent effect on a mammal generalist predator. We also hypothesized that nestling rollers, as their main prey (i.e. grasshoppers) do from plants, could sequester chemicals from their prey for their use. Grasshoppers, that also regurgitate when facing to a threat, store the harmful substances used by plants to defend themselves against herbivores. We found that nestling rollers only vomit after being grasped and moved. The production of vomit depended on food consumption and the vomit contained two deterrent chemicals (hydroxycinnamic and hydroxybenzoic acids) stored by grasshoppers and used by plants to diminish herbivory, suggesting that they originate from the rollers’ prey. Finally, we showed for the first time that the oral secretion of a vertebrate had a deterrent effect on a model predator because vomit of nestling rollers made meat distasteful to dogs. These results support the idea that the vomit of nestling rollers is a chemical defence against predators. 相似文献
609.
María Luz Zapata Basílico Graciela Pose Vanesa Ludemann Virginia E. Fernández Pinto Elena E. Aríngoli Alberto Ritieni Juan Carlos Basílico 《Mycotoxin Research》2010,26(2):85-91
The Fusarium diversity and the mycobiota associated with moldy wheat kernels from Santa Fe province, Argentine, was assessed. The wheat
cultivated area in Santa Fe province is divided according to agrometeorological conditions into two zones: Zone I (north-central)
and Zone II (south). The natural occurrence of Fusarium toxins BEA, FUP, DON and NIV was also determined. Cladosporium was the most abundant of the 19 genera identified, followed by Fusarium, Phoma and Alternaria. Zone II shows a predominance of F. graminearum and F. culmorum. In Zone I, DON was present in 13/32 samples (range 0.43–3.60 mg kg−1) and NIV in 6/32 samples (range 0.11–0.40 mg kg−1). In zone II, DON was found in 11/21 samples (range 0.57–9.50 mg kg−1) and NIV in 4/21 samples (range 0.10–0.60 mg kg−1). BEA and FP were not detected in both zones. 相似文献
610.
Isui García-Montoya Jose Salazar-Martínez Sigifredo Arévalo-Gallegos Sugey Sinagawa-García Quintin Rascón-Cruz 《Biometals》2013,26(1):113-122
Lactoferrin is a member of the transferrin family of iron-binding proteins with a number of properties, including antibacterial activity against a broad spectrum of Gram-negative and Gram-positive bacteria. bovine lactoferrin cDNA was isolated, cloned and expressed as a fusion protein. The amino acid sequence of the fusion was analyzed and compared with other species. Crystallographic data were used to compare structural differences between bovine and human lactoferrin in 3-D models. A thioredoxin fusion protein was expressed and shown to have a different molecular weight compared with native bLf. After purification using Ni-NTA, the yield of recombinant bovine lactoferrin was 15.3 mg/l with a purity of 90.3 %. Recombinant bLf and pepsin-digested rbLf peptides demonstrated antibacterial activity of 79.8 and 86.9 %, respectively. The successful expression of functional, active and intact rbLf allows us to study the biochemical interactions of antimicrobial proteins and peptides and will facilitate their study as immunomodulators. 相似文献