全文获取类型
收费全文 | 131篇 |
免费 | 11篇 |
出版年
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 6篇 |
2014年 | 4篇 |
2013年 | 9篇 |
2012年 | 6篇 |
2011年 | 6篇 |
2010年 | 6篇 |
2009年 | 5篇 |
2008年 | 4篇 |
2007年 | 3篇 |
2006年 | 4篇 |
2005年 | 5篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 9篇 |
2000年 | 2篇 |
1999年 | 8篇 |
1998年 | 8篇 |
1997年 | 4篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1974年 | 2篇 |
1972年 | 1篇 |
1969年 | 4篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1963年 | 1篇 |
1961年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有142条查询结果,搜索用时 78 毫秒
1.
The effects of the trichothecene mycotoxins (acetyl T-2 toxin, T-2 toxin, HT-2 toxin, palmityl T-2 toxin, diacetoxyscirpenol (DAS), deoxynivalenol (DON), and T-2 tetraol) on bovine platelet function were examined in homologous plasma stimulated with platelet activating factor (PAF). The mycotoxins inhibited platelet function with the following order of potency: acetyl T-2 toxin > palmityl T-2 toxin = DAS > HT-2 toxin = T-2 toxin. While T-2 tetraol was completely ineffective as an inhibitor, DON exhibited minimal inhibitory activity at concentrations above 10×10?4M. The stability of the platelet aggregates formed was significantly reduced in all mycotoxin treated platelets compared to that of the untreated PAF controls. It is suggested that the increased sensitivity of PAF stimulated bovine platelets to the more lipophilic mycotoxins may be related to their more efficient partitioning into the platelet membrane compared to the more hydrophilic compounds. 相似文献
2.
Effect of norleucine on mycelial fragmentation in Cephalosporium acremonium. 总被引:2,自引:0,他引:2 下载免费PDF全文
DL-Norleucine, which is known to replace methionine for stimulation of cephalosporin C formation, also mimics methionine's effect on arthrospore formation. Thus, hyphal fragmentation, like antibiotic biosynthesis, is divorced from a sulfur donation role. 相似文献
3.
4.
5.
目的:探讨280例胃食管反流病(GERD)的分布特点及危险因素。方法:对临床诊断和胃镜确诊的280例GERD患者进行临床和风险因子相关性分析。结果:不论汉族还是维族,男性患者比例均明显高于女性;汉族患者高发年龄段早于维族患者(z=-2.939,P=0.003,);汉族和维族患者占反流性食管炎和Barrett食管比例分别为42.4%、81_3%及56.5%、18.8%,其中汉族患者Barrett食管比例较高(X2=14.358,P=0.000);肥胖、习惯性便秘、重体力活动者、饮食习惯不良在维族患者中的比例较高(P〈0.001)。结论:GERD与性别、年龄密切相关,男性多于女性,汉族患者发病年龄高峰旱于维族患者;汉族患者Barrett食管发生比例高于维族患者;肥胖、习惯性便秘、重体力活动、饮食习惯不良可能是GERD尤其是维族人群GERD的危险因素。 相似文献
6.
Extracellular protein profiles were compared for broth-grown cultures of Burkholderia pseudomallei and its avirulent close relative Burkholderia thailandensis. A number of protein bands were present in the B. pseudomallei profile but absent or less abundant in the B. thailandensis profile. Four such prominent secreted proteins were identified by using N-terminal sequencing coupled to searches of the B. pseudomallei genome sequence database. The genes for two proteins with similarity to carbohydrate-binding proteins, and a further protein homologous to known bacterial collagenases, were present in both B. pseudomallei and B. thailandensis. The putative collagenase gene was cloned and expressed as a fusion protein in Escherichia coli. Cell lysates from Escherichia coli containing the recombinant protein exhibited detectable gelatinase and collagenase activities. 相似文献
7.
Jolanda?HM?van Bilsen Josée?PA?Wagenaar-Hilbers Maarten?JF?van der Cammen Mariska?EA?van Dijk Willem?van Eden Marca?HM?WaubenEmail author 《Arthritis research & therapy》2002,4(4):R2
We have recently found that matrix metalloproteinases (MMPs) are targets for T-cell and B-cell reactivity in experimental
arthritis. In the present article, we investigate whether modulation of MMP-specific T-cell responses could influence the
course of adjuvant arthritis (AA). Lewis rats were treated nasally with MMP peptides prior to or after AA induction. Administration
of the MMP-10 or the MMP-16 peptide prior to AA induction reduced the arthritic symptoms. In contrast, administration of the
MMP-10 peptide after AA induction aggravated the arthritic symptoms. The present study shows the possible usefulness of MMP
peptides for immunotherapy. However, a clear understanding of proper timing of peptide administration is crucial for the development
of such therapies. 相似文献
8.
Characterization of terminal NeuNAcalpha2-3Galbeta1-4GlcNAc sequence in lipooligosaccharides of Neisseria meningitidis 总被引:1,自引:0,他引:1
Group B and C Neisseria meningitidis are the major cause of meningococcal
disease in the United States and in Europe. N . meningitidis
lipooligosaccharide (LOS), a major surface antigen, can be divided into 12
immunotypes of which L1 through L8 were found among Group B and C
organisms. Groups B and C but not Group A may sialylate their LOSs with
N-acetylneuraminic acid (NeuNAc) at the nonreducing end because they
synthesize CMP-NeuNAc. Using sialic acid-galactose binding lectins as
probes in an ELISA format, six of the eight LOS immunotypes (L2, L3, L4,
L5, L7, and L8) in Groups B and C bound specifically to Maackia amurensis
leukoagglutinin (MAL), which recognizes NeuNAcalpha2- 3Galbeta1-4GlcNAc/Glc
sequence, but not to Sambucus nigra agglutinin, which binds
NeuNAcalpha2-6Gal sequence. The combination of SDS-PAGE and MAL-blot
analyses revealed that these six LOSs contained only the
NeuNAcalpha2-3Galbeta1-4GlcNAc trisaccharide sequence in their 4.1 kDa LOS
components, which have a common terminal lacto-N-neotetraose (LNnT,
Galbeta1-4GlcNAcbeta1-3Galbeta1-4Glc) structure when nonsialylated as shown
by previous studies. The LOS-lectin binding was abolished when the LOSs
were treated with Newcastle disease viral neuraminidase which cleaves
alpha2-->3 linked sialic acid. Methylation analysis of a representative
LOS (L2) confirmed that NeuNAc is 2-->3 linked to Gal. Thus, these LOSs
structurally mimic certain glycolipids, i.e., paragloboside (LNnT-ceramide)
and sialylparagloboside and some glycoproteins in having LNnT and
N-acetyllactosamine sequences, respectively, with or without alpha2-->3
linked NeuNAc. The molecular mimicry of the LOSs may play a role in the
pathogenesis of N.meningitidis by assisting the organism to evade host
immune defenses in man.
相似文献
9.
10.
N. J. Williams T. R. Jones H. J. Leatherbarrow R. J. Birtles A. Lahuerta-Marin M. Bennett C. Winstanley 《Applied and environmental microbiology》2010,76(21):7318-7321
Campylobacter jejuni can be isolated from different animal hosts. Various studies have used multilocus sequence typing to look for associations between particular clones of C. jejuni and specific hosts. Here, we describe the isolation of a novel clone (sequence type 3704 [ST-3704]) of C. jejuni associated with the bank vole (Myodes glareolus).Campylobacter jejuni is one of the most common causes of gastroenteritis in humans, with food (primarily chicken) believed to be the main vehicle for infection (8). Although high prevalences are found in livestock, C. jejuni has also been isolated from wildlife, including wild birds and wild mammals, and from the farm environment (1, 2, 4, 7, 11, 13). Multilocus sequence typing (MLST) has been used to study the distribution of specific clones among isolates from different hosts and the environment (1, 2, 3, 7, 10, 15, 16, 17). Such molecular epidemiological studies have provided evidence for some host-associated genotypes. For example, some MLST clonal complexes are associated with cattle (sequence type 61 [ST-61] and ST-42 complexes), whereas others are associated with wildlife, such as rabbits and wild birds, and environmental samples (ST-45, ST-177, ST-677, ST-682, and ST-952 complexes) (2, 4, 13). In addition, previously unreported sequence types have been identified in wildlife and environmental samples (4). In this study, we describe the identification of a novel strain of C. jejuni that represents a new sequence type and that is restricted primarily to one wildlife host, namely, bank voles (Myodes glareolus), from which it was isolated over a relatively wide geographic area and time period.We undertook longitudinal studies of feces collected from the sympatric wild rodents bank voles and wood mice (Apodemus sylvaticus) in a private West Cheshire (United Kingdom) woodland habitat. Feces collected from both species were analyzed for the presence of Campylobacter spp. during two sampling periods (May to July 2001 and January 2003). In 2004 (summer/autumn) and 2005 (winter/spring), cross-sectional surveys were conducted on 6 farms (5 dairy and 1 beef farm) in South Cheshire (approximately 30 km away) to investigate the role of wildlife as reservoirs of zoonotic enteric pathogens for livestock. Farms were sampled in summer/autumn on one occasion and in winter/spring on a second occasion; feces were collected from cattle, from wild mammals opportunistically, and from live-trapped rodents. For the isolation of Campylobacter spp., approximately 0.2 ml of fecal homogenate (1:1 feces in brain heart infusion broth) was added to campylobacter enrichment broth containing 5% (vol/vol) lysed horse blood (Southern Group Labs, Corby, United Kingdom), and samples were incubated at 37°C for 24 h under microaerobic conditions in a variable-atmosphere incubator (Don Whitley Scientific Ltd., Shipley, United Kingdom) before being inoculated onto campylobacter blood-free medium containing cefoperazone and amphotericin. These plates were incubated for up to 96 h at 37°C under microaerobic conditions before being examined for the presence of colonies characteristic of Campylobacter spp. All media were obtained from LabM (IDG), Bury, United Kingdom. Suspect isolates were presumptively identified as C. jejuni by Gram staining, no growth in air, and hippurate hydrolysis (6, 18) tests. For further assignment to species, cell lysates were prepared from isolates and subjected to a number of genus- and species-specific PCR assays (5, 14, 19). The whole genome sequence was obtained from bank vole strain C414 by shotgun sequencing.Of the samples obtained from woodland rodents, 23% (10/43) of bank vole samples collected from May to July 2001 and 51% (38/75) collected in January 2003 were positive for Campylobacter spp., whereas Campylobacter spp. were not recovered from any wood mouse samples (40 samples collected from May to July 2001 and 31 samples collected in January 2003). For the farm rodents (samples collected from September 2004 to April 2005), a total of 655 wood mice and 194 bank voles were sampled. In total, 18% (34/194) of bank voles were positive for Campylobacter spp., compared to 1% (6/655) of wood mice (Table (Table1).1). In total, 151 isolates were identified as Campylobacter spp. by using a genus-level 16S rRNA gene PCR assay (14). However, of all of these rodent isolates, only three isolates from wood mice from the farm survey could be identified as C. jejuni by species-specific PCR assays. The remaining rodent isolates from both the woodland and the farm study did not give any amplicons using species-specific PCR assays (5, 14, 19).
Open in a separate windowaNA, not applicable.Two of these PCR assays targeted the hipO gene (14, 19) and used the same gene sequence (GenBank accession no. z36940) for design of the primers, and this gene shares only 90% homology with the hipO gene of bank vole strain C414 (data not shown). Furthermore, the other PCR assay used to identify C. jejuni targeted the ceuE gene (5), and the ceuE gene of C414 shares only 92% homology with the ceuE gene of NCTC11168 (data not shown). The primer binding sites were also divergent for these targets in C414 (5, 19) or were not present at all (14). By use of the method of Karenlampi et al. (9), which involves PCR amplification and sequencing of a groEL fragment, all of the bank vole isolates from the woodland study and one bank vole isolate from the farm study were found to have the same sequence. This sequence (C414, GenBank accession number ) was aligned with partial groEL sequences from other Campylobacter isolates, and phylogenetic trees were inferred from this alignment by using algorithms within the MEGA4 software package ( HQ21385612). In these trees, C414 clustered with C. jejuni strains and not with C. coli strains (Fig. (Fig.1).1). Hence, both hippurate hydrolysis (18) testing and partial groEL sequence analysis suggested that the bank vole-associated isolates were C. jejuni.Open in a separate windowFIG. 1.Evolutionary relationships of strain C414, C. jejuni, C. coli, and C. lari. The evolutionary history was inferred using the minimum evolution (ME) method. The bootstrap consensus tree was inferred from 500 replicates. The percentages of replicate trees in which the associated taxa clustered together in the bootstrap test are shown next to the branches. The tree is drawn to scale, with branch lengths in the same units as those for the evolutionary distances used to infer the phylogenetic tree. The evolutionary distances were computed using the maximum composite likelihood method and are reported in units of the number of base substitutions per site. The ME tree was searched using a close-neighbor-interchange (CNI) algorithm at a search level of 3. A neighbor-joining algorithm was used to generate the initial tree. Codon positions included were first plus second plus third plus noncoding positions. There were a total of 540 positions in the final data set. Phylogenetic analyses were conducted in MEGA4 (12).MLST analysis was carried out on 41 bank vole isolates from the woodland study and 34 bank vole isolates and 6 wood mouse isolates from the farm studies, with each isolate representative of a single sample, using the method of Dingle et al. (3). For each of the seven loci, a new allele was identified (aspA227, glnA297, gltA253, glyA338, pgm-424, tkt-337, and uncA250), generating a new sequence type, ST-3704, for all of the bank vole isolates tested (100% C. jejuni-positive samples). ST-3704 was also identified in 3 wood mouse isolates (3/6 samples), with the remaining isolates representing known sequence types (ST-61 and ST-583). Other C. jejuni isolates (n = 16) from the farm cross-sectional studies were also subjected to MLST analysis, and 15 of these belonged to known sequence types (ST-45, ST-61, ST-257, and ST-403); however, one calf isolate (1/12 C. jejuni-positive samples from cattle) was identified as ST-3704 (Table (Table1).1). Furthermore, more recently (September 2008), we isolated C. jejuni ST-3704, but no other sequence type, from the F1 progeny of a captive colony of bank voles. These animals were fed an artificial diet, which suggests that this clone can be maintained in captive bred animals with no environmental exposure and is therefore strongly associated with the bank vole host. A selection of ST-3704 bank vole isolates (n = 76) from both the woodland and the farm study, the three ST-3704 wood mouse isolates, and other Campylobacter isolates from cattle were subjected to genotyping using macrorestriction pulsed-field gel electrophoresis (PFGE) and analyzed as described previously (11). Remarkably, all 79 of the ST-3704 isolates examined shared similar macrorestriction patterns (<3 bands different) following digestion with SmaI, suggesting that they represent a single clone circulating largely within bank vole populations. Sample macrorestriction patterns for isolates from bank voles from different sources are shown in Fig. Fig.2,2, which also includes examples of other C. jejuni isolates whose banding patterns are more typical of those normally observed for C. jejuni and for C. fetus isolates from cattle.Open in a separate windowFIG. 2.SmaI PFGE analysis of C. jejuni ST-3704, C. jejuni isolates belonging to other sequence types, and C. fetus isolates from bank voles (BV), wood mice (WM), and cows from four Cheshire farms (F1, F2, F3, and F4). Lane λ, lambda ladder PFGE marker (New England Biolabs, Hitchin, United Kingdom).Thus, we report the identification of a new strain of C. jejuni, ST-3704, isolated from different bank vole populations over a relatively wide geographic area with respect to the home range of bank voles, as well as in a captive colony containing F1 individuals, over a period of 7 years. Representatives of this strain could not easily be identified to the species level by using current PCR assays. Isolates of the clone are indistinguishable by MLST and share similar PFGE patterns. Although we have also detected ST-3704 rarely among samples from other animal hosts, including those sharing the same habitat, we isolated ST-3704 largely from the bank vole. Our observations suggest that ST-3704 represents a novel clone of C. jejuni associated with the bank vole host. 相似文献
TABLE 1.
Number of samples from rodents captured in the woodland and farm studies, as well as from cattle in the farm study, positive for Campylobacter jejuni and specifically for ST-3704Animal species | Bacterial species or strain | No. of positive samples/total no. of samples | ||
---|---|---|---|---|
Woodland study | Farm study (2004-2005) | |||
May-July 2001 | January 2003 | |||
Bank voles | C. jejuni | 10/43 | 38/75 | 34/194 |
C. jejuni ST-3704 | 10/43 | 38/75 | 34/194 | |
Wood mice | C. jejuni | 0/40 | 0/31 | 6/655 |
C. jejuni ST-3704 | NAa | NA | 3/655 | |
Cattle | C. jejuni | NA | NA | 12/497 |
C. jejuni ST-3704 | NA | NA | 1/497 |