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1.
Asexual development (conidiation) of the filamentous fungus Aspergillus nidulans occurs via balanced activities of multiple positive and negative regulators. For instance, FluG (+) and SfgA (−) govern upstream regulation of the developmental switch, and BrlA (+) and VosA (−) control the progression and completion of conidiation. To identify negative regulators of conidiation downstream of FluG-SfgA, we carried out multicopy genetic screens using sfgA deletion strains. After visually screening >100,000 colonies, we isolated 61 transformants exhibiting reduced conidiation. Responsible genes were identified as AN3152 (nsdD), AN7507, AN2009, AN1652, AN5833, and AN9141. Importantly, nsdD, a key activator of sexual reproduction, was present in 10 independent transformants. Furthermore, deletion, overexpression, and double-mutant analyses of individual genes have led to the conclusion that, of the six genes, only nsdD functions in the FluG-activated conidiation pathway. The deletion of nsdD bypassed the need for fluG and flbAflbE, but not brlA or abaA, in conidiation, and partially restored production of the mycotoxin sterigmatocystin (ST) in the ΔfluG, ΔflbA, and ΔflbB mutants, suggesting that NsdD is positioned between FLBs and BrlA in A. nidulans. Nullifying nsdD caused formation of conidiophores in liquid submerged cultures, where wild-type strains do not develop. Moreover, the removal of both nsdD and vosA resulted in even more abundant development of conidiophores in liquid submerged cultures and high-level accumulation of brlA messenger (m)RNA even at 16 hr of vegetative growth. Collectively, NsdD is a key negative regulator of conidiation and likely exerts its repressive role via downregulating brlA.  相似文献   
2.
《Current biology : CB》2020,30(22):4441-4453.e4
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3.
The flowering time is the most susceptible period for primary infection of wheat heads byFusarium spp. During this period spores can be deposited into the opened wheat florets where they may later cause infections. We quantitatively explored the relationship between variables related to the flowering process and the infection level byFusarium graminearum in single spikelets. We imitated open (chasmogamous) and closed (cleistogamous) flowering by injecting well-defined amounts of spores into and between wheat florets. Applying the spores between the florets resulted in weaker disease symptoms and significantly lower amounts ofFusarium mycotoxins. With larger numbers of spores, the disease symptoms became more pronounced and the mycotoxin amounts per spikelet increased significantly. Our results indicate that the probability of primary infection is approximately proportional to the number of spores reaching the open florets during the flowering process. The breeding of wheat lines which flower partially or completely cleistogamously might reduce theFusarium susceptibility in wheat.  相似文献   
4.
In order to calculate the dietary fumonisin intake of the German consumer, a large survey was carried out on a variety of potentially contaminated products in the period between December 1998 and July 2001. A total of 1960 food samples comprising all known relevant groups of products were analysed for fumonisins. Furthermore, 272 of these samples were also analysed for hydrolysed fumonisins (HFB). For routine analysis enzyme immunoassay was used, confirmatory and control analyses were performed using HPLC-FLD after precolumn derivatisation, or by LC-MS/MS. Daily intake of fumonisins was calculated by combining fumonisin contamination data obtained in this study with available food consumption data for Germany. In a “mean case” scenario, median fumonisin levels in foods and mean food intake values were used. To generate a “bad case” scenario, the 90th percentile of fumonisin levels in foods and mean food intake values were combined. The overall daily fumonisin intake by the German consumer was 1.1 μg in the “mean case” scenario, and 21 μg in the “bad case” scenario. It was concluded that in general there is no increased risk for the German consumer in aspects of exceeding the recommended tolerable daily intake of fumonisins (2 μg/kg body weight). However, certain products (and certain brands of products) were repeatedly found to contain elevated fumonisin levels, which in a “worst case” scenario (“high” food intake of maize-based products) could pose a potential risk for the consumer, in particular concerning foods for infants and young children. High fumonisin levels were found in infant foods in 1999, but contamination levels decreased strongly in the following years. HFBs (mostly HFB1) were frequently found in processed cereals such as corn flakes, but in relatively low concentrations. According to our findings, the new European Union maximum levels for fumonisins are suitable to eliminate peak contamination levels of fumonisins in foods, but would lead to a regular excess of the TDI for infants and young children if these maximum levels would indeed be exhausted. Financial support: This work was financially supported by the German Federal Ministry for Nutrition, Agriculture and Consumer Protection, research grant 415-6080-1/60 (BMG alt).  相似文献   
5.
Tasks such as manual sorting of domestic wastes for recyclable goods and the deposition of various materials may result in inhalation of mycotoxin-containing aerosols. Ochratoxin A (OTA) was analyzed in blood samples from workers employed at waste handling facilities in Southern Germany to assess the potential impact of this mycotoxin, and explore its use as a biomarker of exposure to bioaerosols. Results from this analysis are reported: OTA serum levels (median values) in subgroups of workers involved in waste deposition (n=76 ‘Deponierer’) or in waste sorting (n=60 ‘Wertstoffsortierer’) were 0.36 and 0.53 ng/ml, respectively. Both groups are natives of countries within the European Community (EU). In waste sorters who were born in other European (non-EU) countries (n=72) or elsewhere (n=12 from Asia, Africa), the OTA serum levels were 0.50 and 0.37 ng/ml, respectively. In controls (n=84 office clerks at the facilities; EU citizens) the median OTA value was 0.39 ng/ml. Comparing the different groups, and previously published data on median OTA levels in the general population (0.21 ng/ml) which result from dietary (background) exposure to OTA in Germany, our data point to an additional uptake of this mycotoxin by inhalation in workers with exposure to bioaerosols. The results support the view that apart from the pathogenic and allergological relevance of microbial emissions from garbage, secondary fungal metabolites, and thus toxicological aspects, deserve further attention.
Presented at the 25th Mykotoxin Workshop in Giessen, Germany, May 19–21, 2003  相似文献   
6.
For some foodstuffs, determination of the mycotoxin ochratoxin A (OTA) requires time consuming clean up by means of solid phase extraction (SPE). Therefore a system for automated SPE was tested for cleaning up roasted coffee as a possible way of shortening preparation time. Validation of the method in accordance to the so called “Concept '98” led to a LOD of 0.2 μg/kg and a recovery rate of 92%. By using the described procedure with samples of roasted coffee the OTA contents varied between the LOD and 3.4 μg/kg. This method was also used to determine ochratoxin A in liquorice roots, ginger and valerian.
Presented at the 26th Mykotoxin Workshop in Herrsching, Germany, May 17–19, 2004  相似文献   
7.
Carry-over of deoxynivalenol (DON) into eggs was investigated within the scope of a 16-week experiment with laying hens, in which the birds were fed a maize-based diet containing DON at 11.9 mg/kg dry matter. Eggs were collected during weeks 2, 4, 8, and 16. DON and its metabolite deepoxy-DON were analysed separately in freeze-dried yolk and albumen. Yolk was extracted with water and the extract was purified using an immunoaffinity column (IAC). Albumen was extracted with acetonitrile-water and the extract was pre-cleaned before applying an IAC. All albumen and some yolk samples were incubated with β-glucuronidase prior to extraction. DON and de-epoxy-DON were determined by high performance liquid chromatography (HPLC) with diode array detection (DAD). The detection limits of both toxins were 20 ng/g and 15 ng/g in freezedried yolk and albumen, respectively, corresponding to approximately 10 ng/g and 2 ng/g in fresh samples. The recovery of DON/de-epoxy-DON in spiked samples (50–200 ng/g) was 87/83% (yolk) and 87/77% (albumen) with coefficients of variation of 4–15%. Neither DON nor de-epoxy-DON were detected in any of the samples. In order to achieve lower detection limits, the methods are currently optimized. However, these preliminary results indicate that eggs do not contribute significantly to the dietary DON intake of the consumer. Presented at the 26th Mykotoxin-Workshop in Herrsching, Germany, May 17–19, 2004  相似文献   
8.
9.
高婧  梁志宏 《微生物学报》2022,62(11):4414-4430
【目的】预测并分析赭曲霉(Aspergillus ochraceus)中存在的G蛋白偶联受体(G-protein- coupled receptors,GPCRs)的结构特征和理化性质,探究赭曲霉GPCR超家族蛋白的结构及所接收配体的聚类情况以及与其他同源蛋白的进化关系,为深入开展赭曲霉中GPCRs的定位、功能研究提供理论基础,也有望从G蛋白信号途径角度抑制赭曲霉毒素的产生,进一步控制粮食的真菌毒素污染。【方法】基于已经报道的曲霉属典型GPCRs序列,在赭曲霉全基因组中进行BLASTp比对以获取候选GPCRs蛋白。通过SMART及多种软件进行保守结构域,特别是跨膜结构的分析,进一步分析候选序列的理化性质、信号肽、二级结构及亚细胞定位等特征。最后,利用MEGA构建赭曲霉中GPCRs与同源蛋白的系统发育树进行遗传关系的比较。【结果】明确赭曲霉存在 15个具有典型7次跨膜结构的GPCRs蛋白,不存在信号肽及转运肽,均含有较高比例的α螺旋结构,15个蛋白质中有7个定位在细胞膜。赭曲霉中的GPCRs与黄曲霉等曲霉属中相应的同源序列具有较近的亲缘关系。【结论】本研究首次对赭曲霉的GPCR超蛋白家族进行了预测,分析其结构及理化性质,探讨了其与同源蛋白的聚类情况,为深入开展赭曲霉GPCRs的功能研究提供理论基础。  相似文献   
10.
Four different mycotoxins (patulin, T-2 toxin, diacetoxyscirpenol and roquefortine) were used to study growth inhibitory effects on a melanin precursor overproducer mutant of the ciliateTetrahymena thermophilaThis strain is especially sensitive to diacetoxyscirpenol and T-2 toxin. The secretion capacity of melanin precursors into the culture medium by this mutant and its biosensor capacity are very useful characteristics to elaborate a rapid bioassay to detect some specific mycotoxins.  相似文献   
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