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排序方式: 共有327条查询结果,搜索用时 31 毫秒
61.
Yasuhiko Horiguchi Takashi Uemura Shunji Kozaki Genji Sakaguchi 《FEMS microbiology letters》1985,28(2):131-135
Abstract The relationship between the cytotoxic effect and binding to different cell lines of Clostridium perfringens enterotoxin was investigated. The enterotoxin released 51 Cr from Vero and MDCK cells labeled with Na2 -51 CrO4 . The effect varied depending upon the dose of enterotoxin and the duration and temperature of the interaction. The enterotoxin gave no effect on FL, KB, or L-929 cells. [125 I]Enterotoxin bound specifically to Vero and MDCK cells via a binding site of distinct nature, but not to FL, KB, or L-929 cells. The number of the binding sites located on one MDCK cell (1.98 × 106 sites/cell) was three times that on one Vero cell (5.64 × 105 sites/cell), although the binding affinity of MDCK cell ( K a / 3.76 × 107 M−1 ) was 0.1 that of Vero cells ( K a / 3.23 × 108 M−1 ). Binding of the enterotoxin to susceptible cells was temperature-independent. 相似文献
62.
探讨了Tecra SEs SET(ELISA法)和Vidas SET2(ELFA法)两种葡萄球菌肠毒素定性检测试剂盒用于定量检测牛奶中葡萄球菌肠毒素A(SEA)的可行性。根据GB/T27404-2008《实验室质量控制规范食品理化检测》的要求,对两种方法应用于定量检测时的检出限、校正曲线范围、相关系数和加标回收率指标进行了分析比较。实验结果显示,Tecra SEs SET对牛奶中SEA的检出限为0.79 ng/mL,校正曲线范围为0.79~10 ng/mL,相关系数r=0.997,SEA加标浓度为0.80、2.5和10 ng/mL时的回收率分别为110%、81%和100%。Vidas SET2的检出限为0.09 ng/mL,校正曲线范围为0.09~1.0 ng/mL,相关系数r=0.998,SEA加标浓度为0.1、0.25和1.0 ng/mL时的回收率分别为90%、95%和104%。上述结果结合对阳性样品的检测表明:这两种定性检测试剂盒能满足牛奶中SEA定量检测的要求。 相似文献
63.
Tatsuo Hase Marti Jett Edward Asafo-Adjei Michael Topper 《In vitro cellular & developmental biology. Animal》1996,32(6):322-328
Summary The release of chromaffin granular content from staphylococcal enterotoxin B (SEB)-treated and-untreated PC12 cells was studied
by electron microscopy. The treatment of the cells with SEB at the concentration of 20 μg/ml caused marked increase of the
chromaffin granules that either bound to the plasma membrane by the characteristic rods, measuring 15 to 20 nm in length and
showing a tubular structure, or budded off at the free cell surface, surrounded by a layer of rod-containing cytoplasm and
enclosed by the plasma membrane. The binding between the granular and plasma membranes by the rods did not lead to membrane
fusion and exocytosis of the granular content. Many of the bound granules showed vesiculation with loss of the electron-dense
core material; at the same time, some of the binding rods contained intraluminal electron-dense material similar to the granular
core material. These findings suggested that the electron-dense material (i.e., norepinephrine) of the bound granules was
released extracellularly through channels within the rods. Although the granules were bound to the plasma membrane with equal
frequency at the free and contiguous cell surfaces, the granular budding occurred only at the free cell surface, indicating
that it occurred incidentally to some granules bound at the free cell surfaces. On the basis of the morphological observations,
it is postulated that the electron-dense material of the bound granule is selectively released extracellularly through the
rods, leaving the vesiculated granules behind in the cytoplasm. The same mode of release of the granular content was observed,
though less frequently, in the untreated control cells. No morphological evidence that indicated that the granular content
was released extracellularly by exocytosis was found in the treated and control cells. The present observations indicated
that the SEB treatment of PC12 cells stimulated the binding of chromaffin granules to the plasma membrane by the rods and
the budding of the bound granules at the free cell surface. 相似文献
64.
给BALB/c小鼠腹腔注射产肠毒素B金黄色葡萄球菌(SEBS)、绿脓杆菌(PA)或葡萄球菌肠毒素B(SEB),均可引起小鼠胸腺萎缩,呈现胸腺重量减轻、胸腺细胞数减少、胸腺细胞存活率降低。实验发现,在这些细菌或毒素作用下,胸腺细胞发生了具有细胞凋亡的特征性形态学和生化学变化。进一步研究表明,小鼠胸腺细胞凋亡的机制可能与这些细菌或毒素诱导宿主产生TNF-α、IFNr和IL-6等细胞因子有关。 相似文献
65.
66.
Nitrate salts suppress sporulation and production of enterotoxin in Clostridium perfringens strain NCTC8239
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Clostridium perfringens type A is a common source of food‐borne illness in humans. Ingested vegetative cells sporulate in the small intestinal tract and in the process produce C. perfringens enterotoxin (CPE). Although sporulation plays a critical role in the pathogenesis of food‐borne illness, the molecules triggering/inhibiting sporulation are still largely unknown. It has previously been reported by our group that sporulation is induced in C. perfringens strain NCTC8239 co‐cultured with Caco‐2 cells in Dulbecco's Modified Eagle Medium (DMEM). In contrast, an equivalent amount of spores was not observed when bacteria were co‐cultured in Roswell Park Memorial Institute‐1640 medium (RPMI). In the present study it was found that, when these two media are mixed, RPMI inhibits sporulation and CPE production induced in DMEM. When a component of RPMI was added to DMEM, it was found that calcium nitrate (Ca[NO3]2) significantly inhibits sporulation and CPE production. The number of spores increased when Ca(NO3)2‐deficient RPMI was used. The other nitrate salts significantly suppressed sporulation, whereas the calcium salts used did not. qPCR revealed that nitrate salts increased expression of bacterial nitrate/nitrite reductase. Furthermore, it was found that nitrite and nitric oxide suppress sporulation. In the sporulation stages, Ca(NO3)2 down‐regulated the genes controlled by Spo0A, a master regulator of sporulation, but not spo0A itself. Collectively, these results indicate that nitrate salts suppress sporulation and CPE production by down‐regulating Spo0A‐regulated genes in C. perfringens strain NCTC8239. Nitrate reduction may be associated with inhibition of sporulation. 相似文献
67.
Tae Takeda Yoshifumi Takeda Saburo Aimoto Toshifumi Takao Haruo Ikemura Yasutsugu Shimonishi Toshio Miwatani 《FEMS microbiology letters》1983,20(3):357-359
Abstract Two distinct heat-stable enterotoxins (ST) produced by enterotoxigenic Escherichia coli , STp and STh , were purified and antisera against the purified STp and STh were prepared by immunizing rabbits with the purified ST's coupled with bovine serum albumin. Neutralizing activity of each antiserum was examined and it was found that both antisera neutralized not only homologous ST but also heterologous St. These data indicate that the two anti-ST antisera are raised against the region of common amino acid sequence of the two ST's. 相似文献
68.
Ann-Mari Svennerholm Marianne Lindblad Bo Svennerholm Jan Holmgren 《FEMS microbiology letters》1988,55(1):23-28
Abstract Modified Escherichia coli heat-stable enterotoxin (STa ) peptides have been synthesized to identify structures that retain the immunological properties of native STa but lack toxicity. Two synthetic peptides, corresponding to the 15 C-terminal amino acid residues of STa (STh ) except for the replacement of one or two Cys residues by Ala, had ≥ 35 000-fold reduced toxicity in infant mice despite almost intact activity as compared to native STa to inhibit monoclonal anti-ST antibody binding to solid phase STa . Three shorter peptides of 6–8 amino acid residues also did not manifest any toxic activity and showed significant but much reduced reactivity with anti-STa antibodies. 相似文献
69.
Cloning and sequencing of the Clostridium perfringens enterotoxin gene 总被引:10,自引:0,他引:10
Marijke van Damme-Jongsten Karel Wernars Servé Notermans 《Antonie van Leeuwenhoek》1989,56(2):181-190
Several gene banks of Clostridium perfringens in E. coli were constructed. Using a mixture of synthetic 29-mer DNA probes clones were selected containing inserts from the C. perfringens gene coding for the enterotoxin. This has allowed sequencing of the complete gene and its flanking regions. The decuded amino acid sequence (320 a.a.) was found to differ at several sites from the sequence published previously by others. Two 40-mer DNA-probes were used to detect the toxin gene in C. perfringens strains isolated from the faeces of different non-symptomatic animals. Only 6% of the strains were found to possess the gene. 相似文献
70.
我们成功地建立了层析等电聚焦的三步程序,分离提纯葡萄球菌D型肠毒素。首先用CG-50树脂吸附由细菌培养液中获得粗毒素,然后在PBE94柱上进行层析等电聚焦,最后经过Sephacryls-200过滤。纯化的SED纯度约98%,回收率89%,分子量为28500,pI 7.6。Western blot,免疫双向琼脂扩散的鉴定试验表明,纯化SED与其相应抗血清是特异性反应。 相似文献