全文获取类型
收费全文 | 194篇 |
免费 | 11篇 |
出版年
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 9篇 |
2017年 | 3篇 |
2016年 | 2篇 |
2015年 | 7篇 |
2014年 | 10篇 |
2013年 | 13篇 |
2012年 | 12篇 |
2011年 | 19篇 |
2010年 | 8篇 |
2009年 | 9篇 |
2008年 | 18篇 |
2007年 | 10篇 |
2006年 | 15篇 |
2005年 | 10篇 |
2004年 | 10篇 |
2003年 | 5篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 4篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1987年 | 4篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有205条查询结果,搜索用时 15 毫秒
31.
32.
Two novel bolaamphiphile based dicarboxylic ligands L1H2 and L2H2 are synthesized by desymmetrizing aromatic anhydrides. The corresponding Cu(II) complexes [Cu(L1) · EtOH]2 (1), [Cu(L2) · (CH3CN)]2 (2) are synthesized and characterized. The crystal structure obtained for (1) and (2) indicates that they are new class of tetralactone type macrocyclic Cu(II) chelate complexes with paddle wheel Cu2-acetate cage structure. The 1:1, Cu(II) and ligand ratio leads into formation of a novel binuclear Cu(II) tetracarboxylate complexes. The macrocyclic chelate ring size in compounds 1 and 2 was altered from [15] membered to [19] membered by introducing phthalyl and diphenyl head groups as discussed in detail. The single crystal X-ray structure shows the Cu(II)?Cu(II) distance 2.613(13) Å for 1 and 2.626(13) Å for 2, the corresponding room temperature EPR spectra recorded for powdered polycrystalline samples indicate the existence of Cu(II)?Cu(II) dimeric system. 相似文献
33.
Govindan Selvakumar Piyush Joshi Pankaj K. Mishra Jaideep K. Bisht Hari S. Gupta 《Current microbiology》2009,59(4):432-438
Fourteen cold tolerant phosphate solubilizing bacteria isolated from high altitude representative locations of the two major
mountain aspects of the Uttarakhand Himalayas (cooler north and warmer south facing slopes) were selected for this study.
The tricalcium phosphate (TCP) solubilizing abilities of the isolates were estimated at three different incubation temperatures
viz., 4, 15, and 30°C under in vitro conditions. Irrespective of their geographical origin, all the isolates recorded maximum
P release values at 30°C. At 4°C, the isolates from the north facing slope were found to release significantly higher levels
of P, as compared to the isolates from the south facing slopes. Alternatively at 15°C, the isolates from the south facing
slope were found to release significantly higher levels of P. Initial confirmation of their genus level identity as Pseudomonads
was arrived by amplification of a 990 bp fragment of the 16S rRNA gene using genus specific primers. Further putative species
level identification was arrived by sequencing of the 16S rRNA gene. The diversity among the isolates was determined by rep-PCR
using the primers BOX, ERIC, and ERIC2. A composite dendrogram constructed using the rep-PCR profiles revealed that the isolates
from the north and south mountain aspects formed separate major clusters. The extent of diversity was greater among the isolates
from the south mountain aspect. This study reveals the potential of rep-PCR in determining the genetic diversity among Pseudomonads
selected for a single functional trait, but varying in their geographical origin. 相似文献
34.
Govindan Selvakumar Piyush Joshi Sehar Nazim Pankaj K. Mishra Jaideep K. Bisht Hari S. Gupta 《Biologia》2009,64(2):239-245
Phosphate solubilization and growth promotion by Pseudomonas fragi CS11RH1 (MTCC 8984), a psychrotolerant bacterium isolated from a high altitude garlic rhizosphere from the Indian Himalayas,
are reported here. The identity of the isolate was arrived on the basis of its biochemical features and sequencing of the
16S rRNA gene. The isolate grew and solubilized phosphate at temperatures ranging from 4 to 30°C. Besides solubilizing P it
produced indole acetic acid (IAA) and hydrogen cyanide (HCN). Seed bacterization with the isolate significantly increased
the percent germination, rate of germination, plant biomass and nutrient uptake of wheat seedlings. While Pseudomonas fragi is normally associated with the spoilage of dairy products stored at cold temperatures, this is an early report on the plant
growth promoting ability of the bacterium. 相似文献
35.
Selvakumar N Yadi Reddy B Sunil Kumar G Khera MK Srinivas D Sitaram Kumar M Das J Iqbal J Trehan S 《Bioorganic & medicinal chemistry letters》2006,16(16):4416-4419
A series of conformationally constrained analogues of Linezolid were synthesised by employing a tandem SN(2) and SNAr reaction as the key step and tested for antibacterial activity. While the hexahydroazolo-quinoxaline compounds were inactive, the tetrahydroazolo-benzothiazine compounds exhibited interesting antibacterial activity. The introduction of fluorine in the aromatic ring further made the compounds more potent in acetamide compounds resulting in an interesting analogue 32. However, the introduction of fluorine (analogue 34) on the already potent non-fluorine thiocarbamate 21 did not have any influence on the activity. 相似文献
36.
Takhi M Murugan C Munikumar M Bhaskarreddy KM Singh G Sreenivas K Sitaramkumar M Selvakumar N Das J Trehan S Iqbal J 《Bioorganic & medicinal chemistry letters》2006,16(9):2391-2395
Novel oxazolidinone antibacterials containing N-hydroxyacetamidine moiety are synthesized with the diversity at C-5 terminus. These compounds have been evaluated against a panel of clinically relevant gram-positive and gram-negative pathogens. Most of the analogs in this series displayed activity superior to Linezolid and in vivo efficacies of selected oxazolidinones are also disclosed herein. 相似文献
37.
Das J Sitaram Kumar M Subrahmanyam D Sastry TV Prasad Narasimhulu C Laxman Rao CV Kannan M Roshaiah M Awasthi R Patil SN Sarnaik HM Rao Mamidi NV Selvakumar N Iqbal J 《Bioorganic & medicinal chemistry》2006,14(23):8032-8042
In an effort to discover potent antibacterials based on the entropically favored 'bioactive conformation' approach, a series of novel tricyclic molecules mimicking the conformationally constrained structure of Linezolid is reported. Based on the initial tricyclic molecule 1, the benzazepine derivative 2 was designed where the tricyclic structure had more flexibility around C-N bond compared to 1. While, the molecule 2 was less active, the molecule 3 showed promising antibacterial activity presumably after having obtained rigidity due to pyrrole ring. The syntheses, SAR studies, and evaluation of 3 as a lead compound are reported. 相似文献
38.
39.
Purushotham Selvakumar Nidhi Sharma Prabhat Pratap Singh Tomar Pravindra Kumar Ashwani Kumar Sharma 《Proteins》2014,82(5):830-840
Murraya koenigii miraculin‐like protein (MKMLP) gradually precipitates below pH 7.5. Here, we explore the basis for this aggregation by identifying the aggregation‐prone regions via comparative analysis of crystal structures acquired at several pH values. The prediction of aggregation‐prone regions showed the presence of four short peptides either in beta sheets or loops on surface of the protein. These peptides were distributed in two patches far apart on the surface. Comparison of crystal structures of MKMLP, determined at 2.2 Å resolution in pH 7.0 and 4.6 in the present study and determined at 2.9 Å in pH 8.0 in an earlier reported study, reveal subtle conformational differences resulting in gradual exposure of aggregation‐prone regions. As the pH is lowered, there are alterations in ionic interactions within the protein interactions of the chain with water molecules and exposure of hydrophobic residues. The analysis of symmetry‐related molecular interfaces involving one patch revealed shortening of nonpolar intermolecular contacts as the pH decreased. In particular, a decrease in the intermolecular distance between Trp103 of the aggregation‐prone peptide WFITTG (103–108) unique to MLPs was observed. These results demonstrated that aggregation occurs due to the cumulative effect of the changes in interactions in two aggregation‐prone defined regions. Proteins 2014; 82:830–840. © 2013 Wiley Periodicals, Inc. 相似文献
40.
Philah Lee Subramanian Mohan Raj Shengfang Zhou Somasundar Ashok Selvakumar Edwardraja Sunghoon Park 《Biotechnology and Bioprocess Engineering》2014,19(1):1-7
This study examined the role and physiological relevance of 3-hydroxyisobutyrate dehydrogenase-I (3HIBDHI) of Pseudomonas denitrificans ATCC 13867 in the degradation of 3-hydroxypropionic acid (3-HP) during 3-HP production. The gene encoding 3HIBDH-I of P. denitrificans ATCC 13867 was cloned and expressed in Escherichia coli BL21 (DE3). The recombinant 3HIBDH-I was then purified on a Ni-NTA-HP column and characterized for its choice of substrates, cofactors, metals, reductants, and the optimal temperature and pH. The recombinant 3HIBDH-I showed a high catalytic constant (k cat/K m) of 604.1 ± 71.1 mM/S on (S)-3-hydroxyisobutyrate, but no detectable activity on (R)-3-hydroxyisobutyrate. 3HIBDH-I preferred NAD+ over NADP+ as a cofactor for its catalytic activity. The k cat/K m determined for 3-HP was 15.40 ± 1.43 mM/S in the presence of NAD+ at 37°C and pH 9.0. In addition to (S)-3-hydroxyisobutyrate and 3-HP, 3HIBDH-I utilized l-serine, methyl-d,l-serine, and methyl-(S)-(+)-3-hydroxy-2-methylpropionate; on the other hand, the k cat/K m values determined for these substrates were less than 5.0mM/S. Ethylenediaminetetraacetic acid, 2-mercaptoethanol, dithiothreitol and Mn2+ increased the activity of 3HIBDHI significantly, whereas the presence of Fe2+, Hg2+ and Ag+ in the reaction mixture at 1.0 mM completely inhibited its activity. This study revealed the characteristics of 3HIBDH-I and its significance in 3-HP degradation. 相似文献