首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   83篇
  免费   20篇
  103篇
  2023年   1篇
  2022年   3篇
  2021年   6篇
  2020年   2篇
  2019年   3篇
  2018年   3篇
  2017年   5篇
  2016年   2篇
  2015年   7篇
  2014年   3篇
  2013年   7篇
  2012年   13篇
  2011年   4篇
  2010年   5篇
  2009年   3篇
  2008年   5篇
  2007年   1篇
  2006年   3篇
  2005年   2篇
  2004年   3篇
  2003年   1篇
  2002年   1篇
  2001年   2篇
  2000年   2篇
  1999年   2篇
  1998年   3篇
  1997年   1篇
  1996年   1篇
  1995年   1篇
  1994年   1篇
  1993年   1篇
  1992年   1篇
  1990年   1篇
  1988年   1篇
  1986年   1篇
  1981年   1篇
  1977年   1篇
排序方式: 共有103条查询结果,搜索用时 13 毫秒
31.
Colchicum luteum is currently a rare and threatened medicinal plant species in the Kashmir Himalaya. Due to the subsequent increase in anthropogenic pressure on medicinal plant species, it is imperative to understand the phytosociological and conservational status of the plant in its natural habitat. The objectives of this study were analysed in year 2018–2019 on the phytosociological data, viz. density, frequency, and abundance, as well as the rhizospheric soil microbial diversity of C. luteum in disturbed and undisturbed areas of the Kashmir Himalaya. We examined the distribution pattern, phytosociological data, and conservation status of C. luteum by analysing ecological features like abundance, frequency, and density in all three selected locations in Kashmir, Northern India and were found maximum values at Undisturbed areas. The highest values of density (3.24 ± 0.69 m2), frequency (57.77 ± 13.55%), and abundance (5.49 m2) were recorded at undisturbed site Harwan. The total bacterial count (CFU) and Vesicular Arbuscular Mycorrhiza (VAM) spore population from the rhizospheric soil of C. luteum were also analysed, with higher bacterial count i.e., Pseudomonas, Azatobacter, Rhizobium and PSB were (26.2 ± 0.648) (21.88 ± 0.675) (30.11 ± 0.576) and (14.11 ± 0.671) and VAM spore population (g−1) of soil recorded 6.36 ± 0.550 at undisturbed areas viz. Harwan. The bacteria and fungi are likely keystone organisms that form an interface between soils and plant roots. Mutualistic associations with host plants have been observed in various natural and agricultural ecosystems. The present findings could be helpful in formulating conservation strategies for C. Luteum threatened and endangered medicinal plant present in North western Himalayan regions. The plant in disturbed areas that are affected by anthropogenic activities like tourism, grazing, deforestation, urbanization, transport etc. impacts on phytosociological and soil microbial patterns in the area. Because of these abiotic pressures, causes a reduction in plant cover in forest regions, soils become exposed, affecting soil microbial health. Therefore, the study shows the necessity for best practices for medicinal plant and forest management that provide effective monitoring and regulation of human activities in the offshore forest regions and avoid the intrusion of existing reserves.  相似文献   
32.
Genotyping methods are essential to understand the transmission dynamics of Acinetobacter baumannii. We examined the representative genotypes of A. baumannii at different time periods in select locations in Ohio, using two rapid automated typing methods: PCR coupled with electrospray ionization mass spectrometry (PCR/ESI-MS), a form of multi-locus sequence typing (MLST), and repetitive-sequence-based-PCR (rep-PCR). Our analysis included 122 isolates from 4 referral hospital systems, in 2 urban areas of Ohio. These isolates were associated with outbreaks at 3 different time periods (1996, 2000 and 2005-2007). Type assignments of PCR/ESI-MS and rep-PCR were compared to each other and to worldwide (WW) clone types. The discriminatory power of each method was determined using the Simpson's index of diversity (DI). We observed that PCR/ESI-MS sequence type (ST) 14, corresponding to WW clone 3, predominated in 1996, whereas ST 12 and 14 co-existed in the intermediate period (2000) and ST 10 and 12, belonging to WW clone 2, predominated more recently in 2007. The shift from WW clone 3 to WW clone 2 was accompanied by an increase in carbapenem resistance. The DI was approximately 0.74 for PCR/ESI-MS, 0.88 for rep-PCR and 0.90 for the combination of both typing methods. We conclude that combining rapid automated typing methods such as PCR/ESI-MS and rep-PCR serves to optimally characterize the regional molecular epidemiology of A. baumannii. Our data also sheds light on the changing sequence types in an 11 year period in Northeast Ohio.  相似文献   
33.
34.
Rather  Gulzar A.  Sharma  Arti  Misra  Prashant  Kumar  Amit  Kaul  Veenu  Lattoo  Surrinder K. 《Protoplasma》2020,257(2):391-405
Protoplasma - Camptothecin is a high-value anti-cancerous compound produced in many taxonomically unrelated species. Its biosynthesis involves a complex network of pathways and a diverse array of...  相似文献   
35.
Using a mini-Tn5lacZ1 reporter transposon, lacZ fusions have been identified in Proteus mirabilis that are activated by the accumulation of self-produced extracellular signals. Genes identified by this approach include putative homologs of pgm, nlpA and two genes of unknown function. The extracellular signal(s) involved in activation were resistant to the effects of acid and alkali. The signal required for activation of (nlpA) cma482::lacZ was sensitive to protease, suggesting the signal is a peptide or small protein. The signals behaved as polar molecules and were not extractable with ethyl acetate. A mini-Tn5Cm insertion was identified in a probable ptsI homolog that blocked activation of the cma134::lacZ fusion by an extracellular signal. The ptsI mutation did not alter extracellular signal production and may have a role in signal response.  相似文献   
36.
Whole cultures of Nocardia sp. NRRL 5646 reduce carboxylic acids, first to aldehydes, then to alcohols and subsequently to the corresponding acetyl esters. This work describes an NADPH-dependent reductase responsible for catalyzing the reduction of aldehyde intermediates, which was purified 3240-fold by a combination of Mono-Q, hydroxyapatite, and ADP-agarose chromatographies. By sodium dodecyl sulfate–polyacrylamide gel electrophoresis, the purified enzyme ran as a single band of 47 kDa. A native molecular mass estimated at 101 kDa indicated that the enzyme was a homodimer in the native, active state. Edman degradation indicated a unique N-terminal sequence as NH2-X-X-Ala-Ala-Ala-Tyr-Ala-Val-Pro-Ala-Pro-Asp-Gly-Cys-Phe-Glu-Lys-Val-Thr-Ile-Glu-Arg-Arg-Glu-Leu-Gly. The enzyme catalyzed reductions of many aryl- and alkyl-aldehyde substrates. Reactions were most favorable in the direction of aldehyde reduction to alcohols. Journal of Industrial Microbiology & Biotechnology (2000) 25, 328–332. Received 08 May 2000/ Accepted in revised form 20 October 2000  相似文献   
37.
A Psychrotolerant alkaline protease producing bacterium IIIM-ST045 was isolated from a soil sample collected from the Thajiwas glacier of Kashmir, India and identified as Stenotrophomonas sp. on the basis of its biochemical properties and 16S ribosomal gene sequencing. The strain could grow well within a temperature range of 4–37°C however, showed optimum growth at 15°C. The strain was found to over-produce proteases when it was grown in media containing lactose as carbon source (157.50 U mg−1). The maximum specific enzyme activity (398 U mg−1) was obtained using soya oil as nitrogen source, however, the inorganic nitrogen sources urea, ammonium chloride and ammonium sulphate showed the lowest production of 38.9, 62.2 and 57.9 U mg−1. The enzyme was purified to 18.45 folds and the molecular weight of the partially purified protease was estimated to be ~55 kDa by SDS-PAGE analysis. The protease activity increased as the increase in enzyme concentration while as the optimum enzyme activity was found when casein (1% w/v) was used as substrate. The enzyme was highly active over a wide range of pH from 6.5 to 12.0 showing optimum activity at pH 10.0. The optimum temperature for the enzyme was 15°C. Proteolytic activity reduced gradually with higher temperatures with a decrease of 56% at 40°C. The purified enzyme was checked for the removal of protein containing tea stains using a silk cloth within a temperature range of 10–60°C. The best washing efficiency results obtained at low temperatures indicate that the enzyme may be used for cold washing purposes of delicate fabrics that otherwise are vulnerable to high temperatures.  相似文献   
38.

Background

The definition of "clinical asthma remission" is based on absence of symptoms and use of medication. However, in the majority of these subjects airway inflammation is still present when measured. In the present study we investigated whether "complete asthma remission", additionally defined by the absence of bronchial hyperresponsiveness (BHR) and the presence of a normal lung function, is associated with the absence of airway inflammation.

Methods

Patients with a former diagnosis of asthma and a positive histamine provocation test were re-examined to identify subjects with complete asthma remission (no asthma symptoms or medication, PC20 histamine > 32 mg/ml, FEV1 > 90% predicted). Patients with PC20 histamine ≤ 32 mg/ml were defined as current asthmatics and were divided in two groups, i.e. asthmatics with and without BHR to adenosine 5'monophoshate (AMP). Sputum induction was performed 1 week before and 1 hour after AMP provocation. Sputum induction and AMP provocation were previously shown to be sensitive markers of airway inflammation.

Results

Seven patients met criteria for complete asthma remission. Twenty-three were current asthmatics, including twelve without hyperresponsiveness to AMP. Subjects with complete asthma remission showed no AMP-induced sputum eosinophilia (median (range) 0.2 (0 - 4.6)% at baseline and 0.2 (0 - 2.6)% after AMP). After AMP, current asthmatics had a significant increase in sputum eosinophils (0.5 (0 - 26.0)% at baseline and 2.6 (0 - 32.0) % after AMP), as had the subgroup of current asthmatics without hyperresponsiveness to AMP (0.2 (0 - 1.8)% at baseline and 1.3 (0 - 6.3)% after AMP).

Conclusions

Subjects with complete asthma remission, in contrast to subjects with current asthma, do not respond with eosinophilic inflammation in sputum after AMP provocations. These data lend support to the usefulness of the definition of complete asthma remission.  相似文献   
39.

Background  

In discriminant analysis of microarray data, usually a small number of samples are expressed by a large number of genes. It is not only difficult but also unnecessary to conduct the discriminant analysis with all the genes. Hence, gene selection is usually performed to select important genes.  相似文献   
40.
The overproduction of reactive oxygen species (ROS) causes oxidative stress, such as Hydrogen peroxide (H2O2). Acute oxidative stress is one of the main reasons for cell death. In this study, the antioxidant properties of vanillic acid- a polyphenolic compound was evaluated. Therefore, this study aims to check the effectiveness of vanillic acid in H2O2-induced oxidative stress in D. Mel-2 cell line. The efficacy was determined by biochemical tests to check the ROS production. The cytotoxicity of H2O2 and vanillic acid was checked by MTT assay. The DNA fragmentation was visualized by gel electrophoresis. Protein biomarkers of oxidative stress were analyzed by western blotting. The results depict a promising antioxidant effect of vanillic acid. The IC50 value of vanillic acid and H2O2 was found 250 μg/ml and 125 μg/ml, respectively. The catalase activity, SOF, GPx, and PC was seen less in H2O2 treated group compared with the control and vanillic acid treated group. However, the TBRAS activity was hight in H2O2 treated group. The effect of H2O2 on DNA fragmentation was high as compared with vanillic acid-treated cells. The protein expression of Hsp70, IL-6 and iNOS was seen significant in a vanillic acid-treated group as compared with H2O2 treated group. These results reinforce that at low concentration, vanillic acid could be used as an antioxidant agent in the food and pharmaceutical industries.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号