全文获取类型
收费全文 | 3019篇 |
免费 | 246篇 |
国内免费 | 1篇 |
出版年
2024年 | 6篇 |
2023年 | 35篇 |
2022年 | 61篇 |
2021年 | 108篇 |
2020年 | 51篇 |
2019年 | 73篇 |
2018年 | 85篇 |
2017年 | 84篇 |
2016年 | 91篇 |
2015年 | 160篇 |
2014年 | 172篇 |
2013年 | 202篇 |
2012年 | 277篇 |
2011年 | 273篇 |
2010年 | 156篇 |
2009年 | 132篇 |
2008年 | 155篇 |
2007年 | 147篇 |
2006年 | 114篇 |
2005年 | 125篇 |
2004年 | 119篇 |
2003年 | 89篇 |
2002年 | 78篇 |
2001年 | 70篇 |
2000年 | 56篇 |
1999年 | 57篇 |
1998年 | 24篇 |
1997年 | 17篇 |
1996年 | 9篇 |
1995年 | 11篇 |
1994年 | 12篇 |
1993年 | 13篇 |
1992年 | 17篇 |
1991年 | 14篇 |
1990年 | 16篇 |
1989年 | 22篇 |
1988年 | 12篇 |
1987年 | 10篇 |
1986年 | 12篇 |
1985年 | 12篇 |
1984年 | 7篇 |
1983年 | 14篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1973年 | 4篇 |
1970年 | 4篇 |
1969年 | 4篇 |
排序方式: 共有3266条查询结果,搜索用时 31 毫秒
991.
Le T Le T Doan TH Quyen D Le KX Pham V Nagataki M Nomura H Ikeue Y Watanabe Y Agatsuma T 《Journal of microbiology and biotechnology》2011,21(4):405-411
Avian influenza virus vaccines produced in oil-emulsified inactivated form with antigen content of at least 160 hemagglutinin units (HAU) induced immunity in birds. However, in addition to enhancing the effect of the adjuvant(s), other additional supplemented biological compounds included in inactivated vaccines could produce higher levels of antibody. We examined in chickens, Vietnamese ducks, and muscovy ducks the adjuvant effect of Sophy β-glucan (SBG), a β-1,3-1,6 glucan produced by the black yeast Aureobasidium pollulans strain AF0-202, when administered with an avian influenza H5 subtype vaccine. In Experiment 1, 40 chickens (ISA Brown hybrid), allocated to four groups of ten each, were immunized with Oil-H5N1(VN), Oil-H5N1(CN), Oil-H5N2(CN), and saline (control group), respectively. In Experiment 2, chickens (ISA Brown hybrid), muscovy ducks (French hybrid), and Vietnamese ducks (indigenous Vietnamese) were used to further assess the effect of SBG on immunogenicity of the Oil-H5N1(VN) Vietnamese vaccine. ELISA and hemagglutination inhibition (HI) assays were used to assess the antibody response. The H5 subtype vaccines initiated significantly higher immune responses in the animals dosed with SBG, with 1.0-1.5 log2 higher HI titers and 10-20% ELISA seroconversion, compared with those not dosed with β-glucan. Notably, some of the animals dosed with SBG induced HI titers higher than 9.0 log2 following boosting immunization. Taken together, our serial studies indicated that SBG is a potential effector, such as enhancing the immune response to the H5 vaccines tested. 相似文献
992.
A gene coding for an endoglucanase (EglA), of the glycosyl hydrolase family 12 and derived from Aspergillus niger VTCC-F021, was cloned and sequenced. The cDNA sequence, 717 bp, and its putative endoglucanase, a 238 aa protein with a predicted molecular mass of 26 kDa and a pI of 4.35, exhibited 98.3-98.7% and 98.3-98.6% identities, respectively, with cDNA sequences and their corresponding endoglucanases from Aspergillus niger strains from the GenBank. The cDNA was overexpressed in Pichia pastoris GS115 under the control of an AOX1 promoter with a level of 1.59 U/ml culture supernatant, after 72 h of growth in a YP medium induced with 1% (v/v) of methanol. The molecular mass of the purified EglA, determined by SDS-PAGE, was 33 kDa, with a specific activity of 100.16 and 19.91 U/mg toward 1% (w/v) of beta-glucan and CMC, respectively. Optimal enzymatic activity was noted at a temperature of 55°C and a pH of 5. The recombinant EglA (rEglA) was stable over a temperature range of 30- 37°C and at pH range of 3.5-4.5. Metal ions, detergents, and solvents tested indicated a slightly inhibitory effect on rEglA activity. Kinetic constants (K(m), V(max), k(cat), and k(cat)/ K(m)) determined for rEglA with beta-glucan as a substrate were 4.04 mg/ml, 102.04 U/mg, 2,040.82 min-1, and 505.05, whereas they were 10.17 mg/ml, 28.99 U/mg, 571.71 min-1, and 57.01 with CMC as a substrate, respectively. The results thus indicate that the rEglA obtained in this study is highly specific toward beta-glucan. The biochemical properties of rEglA make it highly valuable for downstream biotechnological applications, including potential use as a feed enzyme. 相似文献
993.
Gehrau R Maluf D Archer K Stravitz R Suh J Le N Mas V 《Molecular medicine (Cambridge, Mass.)》2011,17(7-8):824-833
Acute cellular rejection (ACR) and hepatitis C virus (HCV) recurrence (HCVrec) are common complications after liver transplantation (LT) in HCV patients, who share common clinical and histological features, making a differential diagnosis difficult. Fifty-three liver allograft samples from unique HCV LT recipients were studied using microarrays, including a training set (n = 32) and a validation set (n = 19). Two no-HCV-ACR samples from LT recipients were also included. Probe set intensity values were obtained using the robust multiarray average method (RMA) method. Analysis of variance identified statistically differentially expressed genes (P ≤ 0.005). The limma package was used to fit the mixed-effects models using a restricted maximum likelihood procedure. The last absolute shrinkage and selection operator (LASSO) model was fit with HCVrec versus ACR as the dependent variable predicted. N-fold cross-validation was performed to provide an unbiased estimate of generalization error. A total of 179 probe sets were differentially expressed among groups, with 71 exclusive genes between HCVrec and HCV-ACR. No differences were found within ACR group (HCV-ACR vs. no-HCV-ACR). Supervised clustering analysis displayed two clearly independent groups, and no-HCV-ACR clustered within HCV-ACR. HCVrec-related genes were associated with a cytotoxic T-cell profile, and HCV-ACR-related genes were associated with the inflammatory response. The best-fitting LASSO model classifier accuracy, including 15 genes, has an accuracy of 100% in the training set. N-fold cross-validation accuracy was 78.1%, and sensitivity, specificity and positive and negative predictive values were 50.0%, 90.9%, 71.4% and 80.0%, respectively. Arginase type II (ARG2), ethylmalonic encephalopathy 1 (ETHE1), transmembrane protein 176A (TMEM176A) and TMEM176B genes were significantly confirmed in the validation set. A molecular signature capable of distinguishing HCVrec and ACR in HCV LT recipients was identified and validated. 相似文献
994.
Dickson KE Tran NT Samuelson JL Njeuhmeli E Cherutich P Dick B Farley T Ryan C Hankins CA 《PLoS medicine》2011,8(11):e1001133
Background
Following confirmation of the effectiveness of voluntary medical male circumcision (VMMC) for HIV prevention, the World Health Organization and the Joint United Nations Programme on HIV/AIDS issued recommendations in 2007. Less than 5 y later, priority countries are at different stages of program scale-up. This paper analyzes the progress towards the scale-up of VMMC programs. It analyzes the adoption of VMMC as an additional HIV prevention strategy and explores the factors may have expedited or hindered the adoption of policies and initial program implementation in priority countries to date.Methods and Findings
VMMCs performed in priority countries between 2008 and 2010 were recorded and used to classify countries into five adopter categories according to the Diffusion of Innovations framework. The main predictors of VMMC program adoption were determined and factors influencing subsequent scale-up explored. By the end of 2010, over 550,000 VMMCs had been performed, representing approximately 3% of the target coverage level in priority countries. The “early adopter” countries developed national VMMC policies and initiated VMMC program implementation soon after the release of the WHO recommendations. However, based on modeling using the Decision Makers'' Program Planning Tool (DMPPT), only Kenya appears to be on track towards achievement of the DMPPT-estimated 80% coverage goal by 2015, having already achieved 61.5% of the DMPPT target. None of the other countries appear to be on track to achieve their targets. Potential predicators of early adoption of male circumcision programs include having a VMMC focal person, establishing a national policy, having an operational strategy, and the establishment of a pilot program.Conclusions
Early adoption of VMMC policies did not necessarily result in rapid program scale-up. A key lesson is the importance of not only being ready to adopt a new intervention but also ensuring that factors critical to supporting and accelerating scale-up are incorporated into the program. The most successful program had country ownership and sustained leadership to translate research into a national policy and program. Please see later in the article for the Editors'' Summary 相似文献995.
996.
Le Ngoc Huyen T Queneudec T'kint M Remond C Chabbert B Dheilly RM 《Comptes rendus biologies》2011,334(11):837.e1-837.e11
Given the non competition of miscanthus with food and animal feed, this lignocellulosic species has attracted attention as a possible biofuel resource. However, sustainability of ethanol production from lignocelluloses biomass would imply reduction in the consumption of chemicals and/or energetic means, but also valorization of the lignocellulosic by-product remaining from enzymatic saccharification. Introduction of these by-products into a cementitious matrix could be used in manufacturing a lightweight composite. Miscanthus biomass was submitted to chemical pretreatments followed by saccharification using an enzymatic cocktail. Residues from saccharification were then mixed with a cementitious matrix. Given their mechanical properties and a good adherence between cement and by-product, the hardened materials could be used. However, the delay in the beginning of setting time is too long, which prevents the direct use of by-product into cementitious matrix. Preliminary experiments using a setting accelerator in the cementitious matrix permitted significant reduction in the setting time delay. 相似文献
997.
Jones LH Beal D Selby MD Everson O Burslem GM Dodd P Millbank J Tran TD Wakenhut F Graham EJ Targett-Adams P 《Journal of chemical biology》2011,4(2):49-53
Small molecule fluorometric boron dipyrromethene probes were developed to bind hepatitis C virus-encoded NS5A protein and aid subcellular distribution studies. These molecules did not co-locate with NS5A, therefore alternative ‘silent’ azide reporters were used to obtain a more relevant picture of their distribution. Following pre-incubation with replicon cells, click chemistry was used to append a fluorophore to the azide that confirmed the co-localisation of the small molecule with the NS5A protein, thus providing greater insight into the antiviral mode of action of this chemotype.
Electronic supplementary material
The online version of this article (doi:10.1007/s12154-010-0047-1) contains supplementary material, which is available to authorized users. 相似文献998.
Romero S Grompone G Carayol N Mounier J Guadagnini S Prevost MC Sansonetti PJ Van Nhieu GT 《Cell host & microbe》2011,9(6):508-519
Shigella, the causative agent of bacillary dysentery in?humans, invades epithelial cells, using a type III secretory system (T3SS) to inject bacterial effectors into host cells and remodel the actin cytoskeleton. ATP released through connexin hemichanels on the epithelial membrane stimulates Shigella invasion and dissemination in epithelial cells. Here, we show that prior to contact with the cell body, Shigella is captured by nanometer-thin micropodial extensions (NMEs) at a distance from the cell surface, in a process involving the T3SS tip complex proteins and stimulated by ATP- and connexin-mediated signaling. Upon bacterial contact, NMEs retract, bringing bacteria in contact with the cell body, where invasion occurs. ATP stimulates Erk1/2 activation, which controls actin retrograde flow in NMEs and their retraction. These findings reveal previously unappreciated facets of interaction of an invasive bacterium with host cells and a prominent role for Erk1/2 in the control of filopodial dynamics. 相似文献
999.
Background
Crumbs (Crb), a cell polarity gene, has been shown to provide a positional cue for the apical membrane domain and adherens junction during Drosophila photoreceptor morphogenesis. It has recently been found that stable microtubules in developing Drosophila photoreceptors were linked to Crb localization. Coordinated interactions between microtubule and actin cytoskeletons are involved in many polarized cellular processes. Since Spectraplakin is able to bind both microtubule and actin cytoskeletons, the role of Spectraplakin was analyzed in the regulations of apical Crb domain in developing Drosophila photoreceptors.Methodology/Principal Findings
The localization pattern of Spectraplakin in developing pupal photoreceptors showed a unique intracellular distribution. Spectraplakin localized at rhabdomere terminal web which is at the basal side of the apical Crb or rhabdomere, and in between the adherens junctions. The spectraplakin mutant photoreceptors showed dramatic mislocalizations of Crb, adherens junctions, and the stable microtubules. This role of Spectraplakin in Crb and adherens junction regulation was further supported by spectraplakin''s gain-of-function phenotype. Spectraplakin overexpression in photoreceptors caused a cell polarity defect including dramatic mislocalization of Crb, adherens junctions and the stable microtubules in the developing photoreceptors. Furthermore, a strong genetic interaction between spectraplakin and crb was found using a genetic modifier test.Conclusions/Significance
In summary, we found a unique localization of Spectraplakin in photoreceptors, and identified the role of spectraplakin in the regulation of the apical Crb domain and adherens junctions through genetic mutational analysis. Our data suggest that Spectraplakin, an actin-microtubule cross-linker, is essential in the apical and adherens junction controls during the photoreceptors morphogenesis. 相似文献1000.
Horby P Pham QT Hens N Nguyen TT Le QM Dang DT Nguyen ML Nguyen TH Alexander N Edmunds WJ Tran ND Fox A Nguyen TH 《PloS one》2011,6(2):e16965