全文获取类型
收费全文 | 572篇 |
免费 | 35篇 |
国内免费 | 2篇 |
出版年
2023年 | 12篇 |
2022年 | 12篇 |
2021年 | 42篇 |
2020年 | 21篇 |
2019年 | 15篇 |
2018年 | 18篇 |
2017年 | 14篇 |
2016年 | 26篇 |
2015年 | 41篇 |
2014年 | 36篇 |
2013年 | 35篇 |
2012年 | 50篇 |
2011年 | 52篇 |
2010年 | 23篇 |
2009年 | 25篇 |
2008年 | 41篇 |
2007年 | 29篇 |
2006年 | 21篇 |
2005年 | 17篇 |
2004年 | 20篇 |
2003年 | 11篇 |
2002年 | 14篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有609条查询结果,搜索用时 31 毫秒
481.
Nguyen Huu Quan Le Thi Hong Trang Nguyen Thi Ngoc Lan Nguyen Thu Giang Sy Danh Thuong Tu Quang Tan Vu Thi Thu Thuy Le Van Son Chu Hoang Mau Vu Thi Kim Lien 《In vitro cellular & developmental biology. Plant》2020,56(6):842-850
In Vitro Cellular & Developmental Biology - Plant - Isoflavones, which are secondary metabolites synthesised through the phenylpropanoid pathway, play important roles in many essential... 相似文献
482.
Anti-Inflammatory Properties of Longifuran A,a New Benzofuran from the Stems of Amomum longiligulare
Le Thanh Huong Pham Anh Thu Phi Thi Dao Doan Thi Mai Huong Pham Van Cuong Nguyen Hai Dang 《化学与生物多样性》2021,18(12):e2100518
In this study, the following compounds were isolated from the dichloromethane fraction of the stems of Amomum longiligulare and then characterized: a new benzofuran, namely, longifuran A ( 1 ); five other phenolic compounds, namely, 4-methoxycinnamic acid ( 2 ), 2,5-dimethoxyphenol ( 3 ), eudesmic acid ( 4 ), 1,7-bis(4-hydroxyphenyl)-1,4,6-heptatrien-3-one ( 5 ), and 4,4’-dihydroxychalcone ( 6 ); and two triterpenoids, namely, 24-methylcycloartan-3β-ol ( 7 ) and 24-methylencycloartan-3β-ol ( 8 ). They were evaluated in terms of their inhibitory effects on NO production in LPS-stimulated RAW 264.7 macrophages. Results indicated that 1 and 5 exhibited promising inhibitory activities against NO generation with IC50 of 10.47±1.02 μM and 8.51±1.14 μM, respectively. Enzymatic assays demonstrated that they remarkably suppressed the secretion of two pro-inflammatory cytokines (i. e., IL-6 and TNF-α). They also dose-dependently inhibited the expression of inducible nitric oxide synthase and cyclooxygenase-2, two important enzymes modulating inflammation. Therefore, 1 and 5 could be targets for the development of new anti-inflammatory therapeutics 相似文献
483.
Hien Thi Thu Nguyen Rikke Kristiansen Mette Vestergaard Reinhard Wimmer Per Halkj?r Nielsen 《Applied and environmental microbiology》2015,81(14):4809-4818
Dynamic anaerobic-aerobic feast-famine conditions are applied to wastewater treatment plants to select polyphosphate-accumulating organisms to carry out enhanced biological phosphorus removal. Acetate is a well-known substrate to stimulate this process, and here we show that different amino acids also are suitable substrates, with glycine as the most promising. 13C-labeled glycine and nuclear magnetic resonance (NMR) were applied to investigate uptake and potential storage products when activated sludge was fed with glycine under anaerobic conditions. Glycine was consumed by the biomass, and the majority was stored intracellularly as free glycine and fermentation products. Subsequently, in the aerobic phase without addition of external substrate, the stored glycine was consumed. The uptake of glycine and oxidation of intracellular metabolites took place along with a release and uptake of orthophosphate, respectively. Fluorescence in situ hybridization combined with microautoradiography using 3H-labeled glycine revealed uncultured actinobacterial Tetrasphaera as a dominant glycine consumer. Experiments with Tetrasphaera elongata as representative of uncultured Tetrasphaera showed that under anaerobic conditions it was able to take up labeled glycine and accumulate this and other labeled metabolites to an intracellular concentration of approximately 4 mM. All components were consumed under subsequent aerobic conditions. Intracellular accumulation of amino acids seems to be a novel storage strategy for polyphosphate-accumulating bacteria under dynamic anaerobic-aerobic feast-famine conditions. 相似文献
484.
Ichikawa M Bawn S Maw NN Htun LL Thein M Gyi A Sunn K Katakura K Itagaki T 《Parasitology international》2011,60(4):474-479
Fasciola spp. in Myanmar were characterized on the basis of spermatogenesis status and DNA markers of nuclear internal transcribed spacer 1 (ITS1) and mitochondrial NADH dehydrogenase subunit 1 (nad1). We collected 88 adult flukes from Yangon, Lashio, and Myitkyina. Spermatogenesis status was analyzed by the presence of sperm in the seminal vesicles, and 8 aspermic and 80 spermic flukes were detected. The flukes were identified on the basis of spermatogenesis status and ITS1 types which were analyzed by a PCR-RFLP method, and 80 spermic flukes were identified as F. gigantica. A very low detection rate of aspermic Fasciola sp. indicated that they are not established in Myanmar. In phylogenetic analyses, the 7 aspermic Fasciola sp. from Myitkyina displayed a haplotype in nad1 sequence, which was identical to that of aspermic Fasciola sp. from other Asian countries including China. Therefore, they were probably introduced from China through an infected domestic ruminant. On the other hand, 17 nad1 haplotypes detected in F. gigantica belonged to 2 clades unique to Myanmar, each with a distinct founder haplotype in a network analysis. This indicated a unique history of F. gigantica introduction into Myanmar involving ancient artificial movements of domestic ruminants. 相似文献
485.
The influenza A virus is one of the main causes of respiratory infection. Although influenza virus infection alone can result in pneumonia, secondary bacterial infection combined with the virus is the major cause of morbidity and mortality. Interestingly, while influenza infection increases susceptibility to some bacteria, including Streptococcus pneumoniae, Staphylococcus aureus (S. aureus), and Haemophilus influenzae, other bacteria such as Escherichia coli (E. coli) and Klebsiella pneumoniae are not associated with influenza infection. The reason for this discrepancy is not known. In this study, it was found that prior influenza virus infection inhibits murine alveolar macrophage phagocytosis of S. aureus but not of E. coli. Here, the mechanism for this inhibition is elucidated: prior influenza virus infection strongly increases interferon gamma (IFN-γ) production. Furthermore, it was shown that IFN-γ differentially affects alveolar macrophage phagocytosis of S. aureus and E. coli. The findings of the present study explain how influenza virus infection increases susceptibility to some bacteria, such as S. aureus, but not others, and provides evidence that IFN-γ might be a promising target for protecting the human population from secondary bacterial infection by influenza. 相似文献
486.
487.
488.
Ngo TH Tran TB Tran TT Nguyen VD Campbell J Pham HA Huynh HT Nguyen VV Bryant JE Tran TH Farrar J Schultsz C 《PloS one》2011,6(3):e17943
Streptococcus suis is a pathogen of major economic significance to the swine industry and is increasingly recognized as an emerging zoonotic agent in Asia. In Vietnam, S. suis is the leading cause of bacterial meningitis in adult humans. Zoonotic transmission is most frequently associated with serotype 2 strains and occupational exposure to pigs or consumption of infected pork. To gain insight into the role of pigs for human consumption as a reservoir for zoonotic infection in southern Vietnam, we determined the prevalence and diversity of S. suis carriage in healthy slaughterhouse pigs. Nasopharyngeal tonsils were sampled from pigs at slaughterhouses serving six provinces in southern Vietnam and Ho Chi Minh City area from September 2006 to November 2007. Samples were screened by bacterial culture. Isolates of S. suis were serotyped and characterized by multi locus sequence typing (MLST) and pulse field gel electrophoresis (PFGE). Antibiotic susceptibility profiles and associated genetic resistance determinants, and the presence of putative virulence factors were determined. 41% (222/542) of pigs carried S. suis of one or multiple serotypes. 8% (45/542) carried S. suis serotype 2 which was the most common serotype found (45/317 strains, 14%). 80% of serotype 2 strains belonged to the MLST clonal complex 1,which was previously associated with meningitis cases in Vietnam and outbreaks of severe disease in China in 1998 and 2005. These strains clustered with representative strains isolated from patients with meningitis in PFGE analysis, and showed similar antimicrobial resistance and virulence factor profiles. Slaughterhouse pigs are a major reservoir of S. suis serotype 2 capable of causing human infection in southern Vietnam. Strict hygiene at processing facilities, and health education programs addressing food safety and proper handling of pork should be encouraged. 相似文献
489.
Wells DE Gutierrez L Xu Z Krylov V Macha J Blankenburg KP Hitchens M Bellot LJ Spivey M Stemple DL Kowis A Ye Y Pasternak S Owen J Tran T Slavikova R Tumova L Tlapakova T Seifertova E Scherer SE Sater AK 《Developmental biology》2011,(1):1-8
Posttranslational modifications constitute a major field of emerging biological significance as mounting evidence demonstrates their key role in multiple physiological processes. Following in the footsteps of protein phosphorylation studies, new modifications are being shown to regulate protein properties and functions in vivo. Among such modifications, an important role belongs to protein arginylation — posttranslational tRNA-mediated addition of arginine, to proteins by arginyltransferase, ATE1. Recent studies show that arginylation is essential for embryogenesis in many organisms and that it regulates such important processes as heart development, angiogenesis, and tissue morphogenesis in mammals. This review summarizes the key data in the protein arginylation field since its original discovery to date. 相似文献
490.
Kyaw Moe Angelina Sijaona Anjana Shrestha Paivi Kettunen Masahiko Taniguchi Keijo Luukko 《Differentiation; research in biological diversity》2012
Timing and patterning of dental pulp innervation are strictly spatio-temporally regulated but it is still not known how they are controlled at molecular level. We analyzed postnatal innervation of the dental pulp in the mandibular first molar of mice deficient for Semaphorin 3A (Sema3A) axon repellant molecule. Immunohistochemical localization of nerve fibers on serial sections covering the whole tooth germs using anti-peripherin antibody revealed that nerve fibers were prematurely present within the preodontoblast layer next to the inner enamel epithelium already at PN0 in Sema3A−/− mice. In contrast, in the wild-type (Sema3A+/+) mice nerve fibers were seen in the pulp only after enamel formation at PN3. The nerves in Sema3A−/− pulp were notably defasciculated and thinner compared to that of Sema3A+/+ mice. A premature formation of an abnormal, enlarged nerve plexus with a high number of arborizations was apparent in the pulp–dentin border target area in Sema3A−/− already at PN2 whereas in the wild-type mice the first sign of plexus formation was seen at PN7. The expression of mRNAs for Ngf, Gdnf and Ncam neuroregulatory molecules in mandibular molar as well as receptors for neurotrophic factors and class 3 semaphorins including Sema3A (TrkA, p75, TrkB, TrkC, Ret, Npn1, Npn2, PlxA4) in trigeminal ganglia were not altered in the Sema3A−/− mice. Collectively, this data show that Sema3A serves an essential role in molar tooth pulp innervation controlling the timing of nerve fiber penetration into the pulp, their patterning and the formation of nerve plexus at pulp–dentin border area, and provide further support for the hypothesis that tooth innervation is regulated by the coordinated activity of locally expressed neuroregulatory molecules exerting positive and negative influences on growing dental nerve fibers. 相似文献