全文获取类型
收费全文 | 978篇 |
免费 | 54篇 |
出版年
2023年 | 12篇 |
2022年 | 33篇 |
2021年 | 55篇 |
2020年 | 21篇 |
2019年 | 30篇 |
2018年 | 43篇 |
2017年 | 33篇 |
2016年 | 39篇 |
2015年 | 62篇 |
2014年 | 54篇 |
2013年 | 62篇 |
2012年 | 82篇 |
2011年 | 70篇 |
2010年 | 41篇 |
2009年 | 31篇 |
2008年 | 35篇 |
2007年 | 45篇 |
2006年 | 49篇 |
2005年 | 40篇 |
2004年 | 31篇 |
2003年 | 26篇 |
2002年 | 21篇 |
2001年 | 10篇 |
2000年 | 9篇 |
1999年 | 6篇 |
1998年 | 10篇 |
1997年 | 8篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1988年 | 7篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 1篇 |
排序方式: 共有1032条查询结果,搜索用时 125 毫秒
81.
Direct comparison of antigen production and induction of apoptosis by canarypox virus- and modified vaccinia virus ankara-human immunodeficiency virus vaccine vectors
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Zhang X Cassis-Ghavami F Eller M Currier J Slike BM Chen X Tartaglia J Marovich M Spearman P 《Journal of virology》2007,81(13):7022-7033
Recombinant poxvirus vectors are undergoing intensive evaluation as vaccine candidates for a variety of infectious pathogens. Avipoxviruses, such as canarypox virus, are replication deficient in mammalian cells by virtue of a poorly understood species-specific restriction. Highly attenuated vaccinia virus strains such as modified vaccinia virus Ankara (MVA) are similarly unable to complete replication in most mammalian cells but have an abortive-late phenotype, in that the block to replication occurs post-virus-specific DNA replication. In this study, an identical expression cassette for human immunodeficiency virus gag, pro, and env coding sequences was placed in canarypox virus and MVA vector backbones in order to directly compare vector-borne expression and to analyze differences in vector-host cell interactions. Antigen production by recombinant MVA was shown to be greater than that from recombinant canarypox virus in the mammalian cell lines and in the primary human cells tested. This observation was primarily due to a longer duration of antigen production in recombinant MVA-infected cells. Apoptosis induction was found to be more profound with the empty canarypox virus vector than with MVA. Remarkably, however, the inclusion of a gag/pro/env expression cassette altered the kinetics of apoptosis induction in recombinant MVA-infected cells to levels equal to those found in canarypox virus-infected cells. Antigen production by MVA was noted to be greater in human dendritic cells and resulted in enhanced T-cell stimulation in an in vitro antigen presentation assay. These results reveal differences in poxvirus vector-host cell interactions that should be relevant to their use as immunization vehicles. 相似文献
82.
Farah SM de Souza EM Pedrosa FO Irino K da Silva LR Rigo LU Steffens MB Pigatto CP Fadel-Picheth CM 《Letters in applied microbiology》2007,44(6):607-612
AIMS: To investigate the prevalence and characteristics of Shiga toxin-producing Escherichia coli (STEC) in cattle from Paraná State, southern Brazil. METHODS AND RESULTS: One hundred and seven faeces cattle samples were cultured on Sorbitol-MacConkey agar. Escherichia coli colonies were tested for production of Shiga toxin using Vero-cell assay. A high prevalence (57%) of STEC was found. Sixty-four STEC were serotyped and examined for the presence of stx(1), stx(2), eae, ehxA and saa genes and stx(2) variants. The isolates belonged to 31 different serotypes, of which three (O152:H8, O175:H21 and O176:H18) had not previously been associated with STEC. A high prevalence of stx(2)-type genes was found (62 strains, 97%). Variant forms found were stx(2), stx(2c), stx(2vhb), stx(2vO111v/OX393) and a form nonclassifiable by PCR-RFLP. The commonest genotypes were stx(2)ehxA saa and stx(1)stx(2)ehxA saa. CONCLUSIONS: A high frequency of STEC was observed. Several strains belong to serotypes previously associated with human disease and carry stx(2) and other virulence factors, thus potentially representing a risk to human health. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study of STEC in Paraná State, and its findings emphasize the need for proper cattle handling to prevent human contamination. 相似文献
83.
Al-Hanbali O Onwuzo NM Rutt KJ Dadswell CM Moghimi SM Hunter AC 《Analytical biochemistry》2007,361(2):287-293
Block copolymers are increasingly being applied in areas such as transfection, membrane sealing, site-specific targeting, and bionanoengineering yet there is a relative paucity of assays available for simple, stable and reproducible colorimetric determination of copolymer concentration in solution. We have focused on improving the accuracy and reproducibility of a modified version of the Stewart biphasic colorimetric assay for quantitative determination of Pluronic (poloxamer) and Tetronic (poloxamine) macromolecules. The optimized assay achieved linear response ranges in chloroform for commonly used copolymers such as poloxamine 904 (20-300 microg/ml), poloxamine 908 (10-400 microg/ml), poloxamer 402 (20-400 microg/ml), and poloxamer 407 (10-400 microg/ml). Variation in the type of chlorinated solvent used significantly increased assay sensitivity, presumably through macromolecular reorientation, affording increased access for copolymer-ferrothiocyanate complexation. This was found to be optimally favored by the planar geometry of the solvent cis 1,2-dichloroethylene. For application to biological systems copolymer-protein interactions were for the first time determined and were found to be dependent on the fraction of hydrophobic constituents of the block copolymers and protein type. For instance serum albumin was found to interact with copolymers of low hydrophilic-lipophilic balance values and poly(propylene oxide) contaminants, whereas this interaction was not significant with the relatively hydrophilic IgG. In such systems the colorimetric assay directly determines the fraction of unbound (free) copolymer in the presence of proteins. 相似文献
84.
Identification of major sporulation proteins of Myxococcus xanthus using a proteomic approach
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dahl JL Tengra FK Dutton D Yan J Andacht TM Coyne L Windell V Garza AG 《Journal of bacteriology》2007,189(8):3187-3197
Myxococcus xanthus is a soil-dwelling, gram-negative bacterium that during nutrient deprivation is capable of undergoing morphogenesis from a vegetative rod to a spherical, stress-resistant spore inside a domed-shaped, multicellular fruiting body. To identify proteins required for building stress-resistant M. xanthus spores, we compared the proteome of liquid-grown vegetative cells with the proteome of mature fruiting body spores. Two proteins, protein S and protein S1, were differentially expressed in spores, as has been reported previously. In addition, we identified three previously uncharacterized proteins that are differentially expressed in spores and that exhibit no homology to known proteins. The genes encoding these three novel major spore proteins (mspA, mspB, and mspC) were inactivated by insertion mutagenesis, and the development of the resulting mutant strains was characterized. All three mutants were capable of aggregating, but for two of the strains the resulting fruiting bodies remained flattened mounds of cells. The most pronounced structural defect of spores produced by all three mutants was an altered cortex layer. We found that mspA and mspB mutant spores were more sensitive specifically to heat and sodium dodecyl sulfate than wild-type spores, while mspC mutant spores were more sensitive to all stress treatments examined. Hence, the products of mspA, mspB, and mspC play significant roles in morphogenesis of M. xanthus spores and in the ability of spores to survive environmental stress. 相似文献
85.
Brault S Gobeil F Fortier A Honoré JC Joyal JS Sapieha PS Kooli A Martin E Hardy P Ribeiro-da-Silva A Peri K Lachapelle P Varma D Chemtob S 《American journal of physiology. Regulatory, integrative and comparative physiology》2007,292(3):R1174-R1183
Oxidant stress plays a significant role in hypoxic-ischemic injury to the susceptible microvascular endothelial cells. During oxidant stress, lysophosphatidic acid (LPA) concentrations increase. We explored whether LPA caused cytotoxicity to neuromicrovascular cells and the potential mechanisms thereof. LPA caused a dose-dependent death of porcine cerebral microvascular as well as human umbilical vein endothelial cells; cell death appeared oncotic rather than apoptotic. LPA-induced cell death was mediated via LPA(1) receptor, because the specific LPA(1) receptor antagonist THG1603 fully abrogated LPA's effects. LPA decreased intracellular GSH levels and induced a p38 MAPK/JNK-dependent inducible nitric oxide synthase (NOS) expression. Pretreatment with the antioxidant GSH precursor N-acetyl-cysteine (NAC), as well as with inhibitors of NOS [N(omega)-nitro-l-arginine (l-NNA); 1400W], significantly prevented LPA-induced endothelial cell death (in vitro) to comparable extents; as expected, p38 MAPK (SB203580) and JNK (SP-600125) inhibitors also diminished cell death. LPA did not increase indexes of oxidation (isoprostanes, hydroperoxides, and protein nitration) but did augment protein nitrosylation. Endothelial cytotoxicity by LPA in vitro was reproduced ex vivo in brain and in vivo in retina; THG1603, NAC, l-NNA, and combined SB-203580 and SP600125 prevented the microvascular rarefaction. Data implicate novel properties for LPA as a modulator of the cell redox environment, which partakes in endothelial cell death and ensued neuromicrovascular rarefaction. 相似文献
86.
Puri SC Amna T Khajuria A Gupta A Arora R Spiteller M Qazi GN 《Acta microbiologica et immunologica Hungarica》2007,54(3):237-260
A novel camptothecin-producing endophytic fungus viz., Entrophospora infrequens was isolated from an important Indian medicinal plant Nothapodytes foetida. The present study reports evaluation ofbioactivities of two novel extracts viz., chloroform (CEEI) and methanolic (MEEI) extracts of Entrophospora infrequens with respect to their immunomodulatory potential in vitro and in vivo (in Balb/c mice). The endophyte E. infrequens was found to synthesize camptothecin, which tested positive in CEEI. The immunomodulatory potential of CEEI and MEEI was compared with standard camptothecin (CPT). Doses of the chloroform extract (CEEI) ranging from 12.5-100 mg/kg body weight, significantly (p < 0.05) stimulated the humoral and cell-mediated immune responses in a dose-dependent manner. MEEI on the other hand significantly (p < 0.05) stimulated the delayed type hypersensitivity (DTH) reaction (by nearly 80%), plaque forming cell (PFC) assay (33%), phagocytic response (38%) and haemagglutination antibody (HA) titre [IgM by 79.07% and IgG by 62.05%] at a dose of 12.5 mg/kg body weight. The present study is the first report of the immunomodulatory potential of this neoteric camptothecin-producing endophyte from Nothapodytes foetida. 相似文献
87.
Conserved actin cysteine residues are oxidative stress sensors that can regulate cell death in yeast
下载免费PDF全文
![点击此处可从《Molecular biology of the cell》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Actin's functional complexity makes it a likely target of oxidative stress but also places it in a prime position to coordinate the response to oxidative stress. We have previously shown that the NADPH oxidoreductase Oye2p protects the actin cytoskeleton from oxidative stress. Here we demonstrate that the physiological consequence of actin oxidation is to accelerate cell death in yeast. Loss of Oye2p leads to reactive oxygen species accumulation, activation of the oxidative stress response, nuclear fragmentation and DNA degradation, and premature chronological aging of yeast cells. The oye2Delta phenotype can be completely suppressed by removing the potential for formation of the actin C285-C374 disulfide bond, the likely substrate of the Oye2p enzyme or by treating the cells with the clinically important reductant N-acetylcysteine. Because these two cysteines are coconserved in all actin isoforms, we theorize that we have uncovered a universal mechanism whereby actin helps to coordinate the cellular response to oxidative stress by both sensing and responding to oxidative load. 相似文献
88.
Cicero DO Contessa GM Pertinhez TA Gallo M Katsuyama AM Paci M Farah CS Spisni A 《Proteins》2007,67(2):490-500
ApaG proteins are found in a wide variety of bacterial genomes but their function is as yet unknown. Some eukaryotic proteins involved in protein-protein interactions, such as the human polymerase delta-interacting protein (PDIP38) and the F Box A (FBA) proteins, contain ApaG homology domains. We have used NMR to determine the solution structure of ApaG protein from the plant pathogen Xanthomonas axonopodis pv. citri (ApaG(Xac)) with the aim to shed some light on its molecular function. ApaG(Xac) is characterized by seven antiparallel beta strands forming two beta sheets, one containing three strands (ABE) and the other four strands (GFCC'). Relaxation measurements indicate that the protein has a quite rigid structure. In spite of the presence of a putative GXGXXG pyrophosphate binding motif ApaG(Xac) does not bind ATP or GTP, in vitro. On the other hand, ApaG(Xac) adopts a fibronectin type III (Fn3) fold, which is consistent with the hypothesis that it is involved in mediating protein-protein interactions. The fact that the proteins of ApaG family do not display significant sequence similarity with the Fn3 domains found in other eukaryotic or bacterial proteins suggests that Fn3 domain may have arisen earlier in evolution than previously estimated. 相似文献
89.
Multiple sequence alignment was performed against eight proteases from the Flaviviridae family using ClustalW to illustrate conserved domains. Two sets of prediction approaches were applied and the results compared. Firstly, secondary structure prediction was performed using available structure prediction servers. The second approach made use of the information on the secondary structures extracted from structure prediction servers, threading techniques and DSSP database of some of the templates used in the threading techniques. Consensus on the one-dimensional secondary structure of Den2 protease was obtained from each approach and evaluated against data from the recently crystallised Den2 NS2B/NS3 obtained from the Protein Data Bank (PDB). Results indicated the second approach to show higher accuracy compared to the use of prediction servers only. Thus, it is plausible that this approach is applicable to the initial stage of structural studies of proteins with low amino acid sequence homology against other available proteins in the PDB. 相似文献
90.
Katie L Mickle Sunita Ramanathan Adam Rosebrock Anna Oliva Amna Chaudari Chulee Yompakdee Donna Scott Janet Leatherwood Joel A Huberman 《BMC molecular biology》2007,8(1):1-28