全文获取类型
收费全文 | 583篇 |
免费 | 34篇 |
国内免费 | 2篇 |
专业分类
619篇 |
出版年
2023年 | 2篇 |
2022年 | 8篇 |
2021年 | 23篇 |
2020年 | 12篇 |
2019年 | 14篇 |
2018年 | 14篇 |
2017年 | 16篇 |
2016年 | 13篇 |
2015年 | 14篇 |
2014年 | 32篇 |
2013年 | 39篇 |
2012年 | 55篇 |
2011年 | 50篇 |
2010年 | 30篇 |
2009年 | 40篇 |
2008年 | 51篇 |
2007年 | 28篇 |
2006年 | 29篇 |
2005年 | 29篇 |
2004年 | 28篇 |
2003年 | 15篇 |
2002年 | 17篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有619条查询结果,搜索用时 0 毫秒
101.
Akhil Kumar Nishank Goyal Nandhini Saranathan Sonam Dhamija Saurabh Saraswat Manoj B Menon Perumal Vivekanandan 《Molecular biology and evolution》2022,39(3)
Depletion of CpG dinucleotides in severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) genomes has been linked to virus evolution, host-switching, virus replication, and innate immune responses. Temporal variations, if any, in the rate of CpG depletion during virus evolution in the host remain poorly understood. Here, we analyzed the CpG content of over 1.4 million full-length SARS-CoV-2 genomes representing over 170 million documented infections during the first 17 months of the pandemic. Our findings suggest that the extent of CpG depletion in SARS-CoV-2 genomes is modest. Interestingly, the rate of CpG depletion is highest during early evolution in humans and it gradually tapers off, almost reaching an equilibrium; this is consistent with adaptations to the human host. Furthermore, within the coding regions, CpG depletion occurs predominantly at codon positions 2-3 and 3-1. Loss of ZAP (Zinc-finger antiviral protein)-binding motifs in SARS-CoV-2 genomes is primarily driven by the loss of the terminal CpG within the motifs. Nonetheless, majority of the CpG depletion in SARS-CoV-2 genomes occurs outside ZAP-binding motifs. SARS-CoV-2 genomes selectively lose CpGs-motifs from a U-rich context; this may help avoid immune recognition by TLR7. SARS-CoV-2 alpha-, beta-, and delta-variants of concern have reduced CpG content compared to sequences from the beginning of the pandemic. In sum, we provide evidence that the rate of CpG depletion in virus genomes is not uniform and it greatly varies over time and during adaptations to the host. This work highlights how temporal variations in selection pressures during virus adaption may impact the rate and the extent of CpG depletion in virus genomes. 相似文献
102.
Wb14 of Wuchereria bancrofti, an orthologue of Brugia malayiSXP-1 and W. bancrofti SXP-1, was amplified from genomic DNA of W. bancrofti microfilaria collected from four distant geographical locations in India viz., Vellore, Bhubaneshwar, Pondicherry and Sevagram. The gene was sub-cloned in a prokaryotic vector pRSET and expressed in Escherichia coli as a truncated protein (∼23 kDa). The nucleotide sequence of the gene is 98% similar to that of WbSXP-1 and is found to be intron-less. However, the analysis and comparison of the derived amino acid sequence with WbSXP-1 showed that Wb14 is truncated at amino acid position 153. The distribution of the two genes in the studied four geographical locations indicated that WbSXP-1 is prevalent only in parasite samples from Sevagram while Wb14 is present in parasites from all the other locations. Only a limited polymorphism was observed in both the genes among the parasites from different geographical locations. 相似文献
103.
Kezhavituo Vupru Joydip Mukherjee Dipak Banerjee P. Perumal Prabal Ranjan Ghosh 《Biological Rhythm Research》2016,47(6):841-850
The role of lactogenic hormones (prolactin, growth hormone, cortisol and thyroid hormone) on lactation yield in Mithun cows as well as their rhythmicity throughout the lactation cycle were studied in Mizoram (n = 4) and Nagaland (n = 7) strain of mithun (Bos frontalis). Blood samples were collected from all the animals from the day of calving to the complete dry off at an interval of 15 days. All the hormones were estimated in the serum by commercially available ELISA kits. Plasma level of cortisol (μg/dl), growth hormone (GH, in ng/ml), prolactin (PRL, in μIU/ml), triiodothyronine (T3, in nmol/μl) and thyroxin (T4, in ng/ml) were 20.84 ± 0.29, 28.08 ± 0.56, 9.87 ± 0.20, 27.82 ± 0.56 and 51.33 ± 0.48, respectively, in mithun irrespective of strains during the lactation period. Levels of all the hormones varied significantly (p ≤ 0.01) during different days of lactation cycle but, there was no significant difference among strain. Levels of PRL, GH, cortisol and T3 were significantly (p < 0.01) higher around calving and declined sharply. The hormones remained in almost steady state during mid-lactation and declined during late lactation. All the hormones stated above were positively correlated with lactational yield thus their role on lactogenesis and galactopoiesis was established. 相似文献
104.
Abstract— It has been reported that myelin basic protein (MBP) forms a specific complex with S-100 protein in the presence of either Ca2+ or Mn2+, as detected by Immunoelectrophoresis. We have now studied the binding of Ca2+ and Mn2+ to these two proteins. We find that MBP binds 1 mol of Mn2+/mol of protein, and this binding produces an increment in its fluorescence, indicating a conformational change. Ca2+ does not bind to MBP nor does it affect the fluorescence of MBP. S-100 protein, as has been reported, binds about 10 mol of Ca2+/mol and this binding produces a conformational change. S-100 protein also has 25 binding sites for Mn2+, but this binding does not alter fluorescence and does not appear to affect conformation. Competitive binding experiments demonstrate that the binding sites of S-100 protein for Ca2+ and Mn2+ are independent. The alteration of electrophoretic migration in gels of S-100 protein produced by Ca2+ and of MBP produced by Mn2+ are in accord with the observations based on fluorescence. Mn2+ does not affect the electrophoretic mobility of S-100. These results indicate that the formation of the complex between MBP and S-100 protein in the presence of either Ca2+ or Mn2+ is due to the conformational change induced by these ions in S-100 protein, MBP, or both. 相似文献
105.
Stabilization of collagen through bioconversion: An insight in protein–protein interaction 下载免费PDF全文
Nagarajan Usharani Gladstone Christopher Jayakumar Swarna Vinodh Kanth Jonnalagadda Raghava Rao 《Biopolymers》2014,101(8):903-911
Collagen is a natural protein, which is used as a vital biomaterial in tissue engineering. The major concern about native collagen is lack of its thermal stability and weak resistance to proteolytic degradation. In this scenario, the crosslinking compounds used for stabilization of collagen are mostly of chemical nature and exhibit toxicity. The enzyme mediated crosslinking of collagen provides a novel alternative, nontoxic method for stabilization. In this study, aldehyde forming enzyme (AFE) is used in the bioconversion of hydroxylmethyl groups of collagen to formyl groups that results in the formation of peptidyl aldehyde. The resulted peptidyl aldehyde interacts with bipolar ions of basic amino acid residues of collagen. Further interaction leads to the formation of conjugated double bonds (aldol condensation involving the aldehyde group of peptidyl aldehyde) within the collagen. The enzyme modified collagen matrices have shown an increase in the denaturation temperature, when compared with native collagen. Enzyme modified collagen membranes exhibit resistance toward collagenolytic activity. Moreover, they exhibited a nontoxic nature. The catalytic activity of AFE on collagen as a substrate establishes an efficient modification, which enhances the structural stability of collagen. This finds new avenues in the context of protein–protein stabilization and discovers paramount application in tissue engineering. © 2014 Wiley Periodicals, Inc. Biopolymers 101: 903–911, 2014. 相似文献
106.
Zhenxin Hu Senthil K. Perumal Hongjun Yue Stephen J. Benkovic 《The Journal of biological chemistry》2012,287(46):38442-38448
Polymerase δ is widely accepted as the lagging strand replicative DNA polymerase in eukaryotic cells. It forms a replication complex in the presence of replication factor C and proliferating cell nuclear antigen to perform efficient DNA synthesis in vivo. In this study, the human lagging strand holoenzyme was reconstituted in vitro. The rate of DNA synthesis of this holoenzyme, measured with a singly primed ssM13 DNA substrate, is 4.0 ± 0.4 nucleotides. Results from adenosine 5′-(3-thiotriphosphate) tetralithium salt (ATPγS) inhibition experiments revealed the nonprocessive characteristic of the human DNA polymerase (Pol δ) holoenzyme (150 bp for one binding event), consistent with data from chase experiments with catalytically inactive mutant Pol δAA. The ATPase activity of replication factor C was characterized and found to be stimulated ∼10-fold in the presence of both proliferating cell nuclear antigen and DNA, but the activity was not shut down by Pol δ in accord with rapid association/dissociation of the holoenzyme to/from DNA. It is noted that high concentrations of ATP inhibit the holoenzyme DNA synthesis activity, most likely due to its inhibition of the clamp loading process. 相似文献
107.
108.
Dharmarajan Sriram Perumal Yogeeswari Prathiba Dhakla Palaniappan Senthilkumar Debjani Banerjee Thimmappa H. Manjashetty 《Bioorganic & medicinal chemistry letters》2009,19(4):1152-1154
Eighteen 5-nitrofuran-2-yl derivatives were prepared by reacting 5-nitro-2-furfural with various (sub)phenyl/pyridyl thiosemicarbazide using microwave irradiation. The compounds were tested for their in vitro activity against tubercular and various non-tubercular mycobacterium species in log-phase and 6-week-starved cultures. Compound N-(3,5-dibromopyridin-2-yl)-2-((5-nitrofuran-2-yl)methylene)hydrazinecarbothioamide (4r) was found to be the most potent compound (MIC: 0.22 μM) and was 3 times more active than standard isoniazid (INH) and equally active as rifampicin (RIF) in log-phase culture of Mycobacterium tuberculosis H37Rv. In starved M. tuberculosis H37Rv, 4r inhibited with MIC of 13.9 μM and was found to be 50 times more active than INH and slightly more active than RIF. 相似文献
109.
110.
Rajasekaran Ekambaram Akila Kannaiyan Vijayasarathy Marimuthu Vinobha Chinnaiah Swaminathan Senthil Renganathan Ananda Gopu Perumal 《Bioinformation》2014,10(3):138-143
Spatial arrangement of carbon in protein structure is analyzed here. Particularly, the carbon fractions around individual atoms arecompared. It is hoped that it follows the principle of 31.45% carbon around individual atoms. The results reveal that globularprotein''s atoms follow this principle. A comparative study on monomer versus dimer reveal that carbon is better distributed indimeric form than in its monomeric form. Similar study on solid versus liquid structures reveals that the liquid (NMR) structurehas better carbon distribution over the corresponding solid (X-Ray) structure. The carbon fraction distributions in fiber and toxinprotein are compared. Fiber proteins follow the principle of carbon fraction distribution. At the same time it has another broadspectrum of carbon distribution than in globular proteins. The toxin protein follows an abnormal carbon fraction distribution. Thecarbon fraction distribution plays an important role in deciding the structure and shape of proteins. It is hoped to help inunderstanding the protein folding and function. 相似文献