全文获取类型
收费全文 | 635篇 |
免费 | 76篇 |
国内免费 | 2篇 |
专业分类
713篇 |
出版年
2023年 | 5篇 |
2022年 | 12篇 |
2021年 | 19篇 |
2020年 | 8篇 |
2019年 | 9篇 |
2018年 | 13篇 |
2017年 | 14篇 |
2016年 | 18篇 |
2015年 | 23篇 |
2014年 | 31篇 |
2013年 | 51篇 |
2012年 | 47篇 |
2011年 | 58篇 |
2010年 | 33篇 |
2009年 | 31篇 |
2008年 | 25篇 |
2007年 | 40篇 |
2006年 | 36篇 |
2005年 | 23篇 |
2004年 | 12篇 |
2003年 | 16篇 |
2002年 | 13篇 |
2001年 | 11篇 |
2000年 | 14篇 |
1999年 | 7篇 |
1998年 | 8篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1994年 | 5篇 |
1992年 | 8篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1985年 | 6篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1972年 | 4篇 |
1971年 | 3篇 |
1969年 | 6篇 |
1968年 | 3篇 |
排序方式: 共有713条查询结果,搜索用时 0 毫秒
81.
Balasubramanian Radhakrishnan Radha Prasanna Pranita Jaiswal Saswati Nayak Prem Dureja 《Biologia》2009,64(5):881-889
An investigation was undertaken to evaluate a set of cyanobacterial strains in terms of production of biocidal compounds exhibiting
allelochemical and fungicidal properties. Two cyanobacterial strains — Anabaena sp. and Calothrix sp. were selected for further investigation, on the basis of their larger inhibition zones on the lawn of Synechocystis and Synechococcus sp. and two phytopathogenic fungi — Rhizoctonia bataticola and Pythium debaryanum. The diameter of the inhibition zone was largest when extracellular filtrates of the two cultures incubated at high light
intensity (90–100 μmol photons m−2 s−1) and temperature (40 ± 2 °C) or grown in medium containing two-folds higher P (1.4 mg/L, as compared to 0.7 mg/L in BG 11
medium) were taken. A pH of 8 was the most optimal for both strains, in terms of growth and biocidal activity. Partial purification
of ethyl acetate extract using TLC, followed by GLC revealed a single peak. This study highlights the importance of environmental
factors in aggravating or reducing the toxic effects of these harmful cyanobacteria and their potential as a biocontrol agent. 相似文献
82.
Lung cancer is the number one cause of cancer death; however, no specific serum biomarker is available till date for detection of early lung cancer. Despite good initial response to chemotherapy, small-cell lung cancer (SCLC) has a poor prognosis. Therefore, it is important to identify molecular markers that might influence survival and may serve as potential therapeutic targets. The review aims to summarize the current knowledge of serum biomarkers in SCLC to improve diagnostic efficiency in the detection of tumor progression in lung cancer. The current knowledge on the known serum cytokines and tumor biomarkers of SCLC is emphasized. Recent findings in the search for novel diagnostic and therapeutic molecular markers using the emerging genomic technology for detecting lung cancer are also described. It is believed that implementing these new research techniques will facilitate and improve early detection, prognostication and better treatment of SCLC. 相似文献
83.
Nayak GS Kamath S Pai KM Sarkar A Ray S Kurien J D'Almeida L Krishnanand BR Santhosh C Kartha VB Mahato KK 《Biopolymers》2006,82(2):152-166
Pulsed laser-induced autofluorescence spectroscopic studies of pathologically certified normal, premalignant, and malignant oral tissues were carried out at 325 nm excitation. The spectral analysis and classification for discrimination among normal, premalignant, and malignant conditions were performed using principal component analysis (PCA) and artificial neural network (ANN) separately on the same set of spectral data. In case of PCA, spectral residuals, Mahalanobis distance, and scores of factors were used for discrimination among normal, premalignant, and malignant cases. In ANN, parameters like mean, spectral residual, standard deviation, and total energy were used to train the network. The ANN used in this study is a classical multiplayer feed-forward type with a back-propagation algorithm for the training of the network. The specificity and sensitivity were determined in both classification schemes. In the case of PCA, they are 100 and 92.9%, respectively, whereas for ANN they are 100 and 96.5% for the data set considered. 相似文献
84.
Albert K. Dearden Brian Callahan Patrick Van Roey Zhong Li Utsav Kumar Marlene Belfort Saroj K. Nayak 《Protein science : a publication of the Protein Society》2013,22(5):557-563
Protein splicing is an autocatalytic process where an “intein” self‐cleaves from a precursor and ligates the flanking N‐ and C‐“extein” polypeptides. Inteins occur in all domains of life and have myriad uses in biotechnology. Although the reaction steps of protein splicing are known, mechanistic details remain incomplete, particularly the initial peptide rearrangement at the N‐terminal extein/intein junction. Recently, we proposed that this transformation, an N‐S acyl shift, is accelerated by a localized conformational strain, between the intein's catalytic cysteine (Cys1) and the neighboring glycine (Gly‐1) in the N‐extein. That proposal was based on the crystal structure of a catalytically competent trapped precursor. Here, we define the structural origins and mechanistic relevance of the conformational strain using a combination of quantum mechanical simulations, mutational analysis, and X‐ray crystallography. Our results implicate a conserved, but largely unstudied, threonine residue of the Ssp DnaE intein (Thr69) as the mediator of conformational strain through hydrogen bonding. Further, the strain imposed by this residue is shown to position the splice junction in a manner that enhances the rate of the N‐S acyl shift substantially. Taken together, our results not only provide fundamental understanding of the control of the first step of protein splicing but also have important implications in various biotechnological applications that require precursor manipulation. 相似文献
85.
Construction and characterization of a bacterial clone containing the hemagglutinin gene of the WSN strain (HON1) of influenza virus 总被引:12,自引:0,他引:12
A synthetic dodecadeoxynucleotide primer has been used to prepare a double-stranded DNA form of the hemagglutinin (HA) gene of a human influenza virus (WSN strain, HON1). This DNA has been inserted in plasmid pBR322 and cloned in bacterial cells. The insert contains nearly the complete hemagglutinin gene. A restriction map of this insert has been determined and structurally important areas of the HA gene have been sequenced. Amino acid sequences of several regions of the HA protein were deduced from the DNA sequences and compared to the known amino acid sequences of other influenza A viruses. WSN HA shows extensive homology to all influenza A viruses in a few regions, namely the first 17 amino acids of the N-terminus of HA1 (N-terminal polypeptide of HA) and the first 24 amino acids of the N-terminus of HA2 (C-terminal polypeptide of HA). The sequence diverges extensively from other influenza A viruses in most other areas. The sequence of WSN virus HA is similar to that of other HON1 viruses with the exception of the C-terminus of the HA1 peptide. The change in this area may contribute to some of the unique properties of WSN virus among the HON1 viruses. In addition, WSN HA contains a 17-amino-acid precursor before the N-terminus of HA1 and a single amino acid, arginine, connecting HA1 and HA2. 相似文献
86.
Shreyasi Asthana Zaved Hazarika Parth Sarathi Nayak Jyoti Roy Anupam Nath Jha Bibekanand Mallick Suman Jha 《Biochimica et Biophysica Acta (BBA)/General Subjects》2019,1863(1):153-166
Background
Injection localized amyloidosis is one of the most prevalent disorders in type II diabetes mellitus (TIIDM) patients relying on insulin injections. Previous studies have reported that nanoparticles can play a role in the amyloidogenic process of proteins. Hence, the present study deals with the effect of zinc oxide nanoparticles (ZnONP) on the amyloidogenicity and cytotoxicity of insulin.Methods
ZnONP is synthesised and characterized using XRD, Zeta Sizer, UV-Visible spectroscope and TEM. The characterization is followed by ZnONP interaction with insulin, which is studied employing fluorescence spectroscopes, isothermal titration calorimetry and molecular dynamics simulations. The interaction leads insulin conformational rearrangement into amyloid-like fibril, which is studied using thioflavin T dye binding assay, circular dichroism spectroscopy and TEM, followed by cytotoxicity propensity using Alamar Blue dye reduction assay.Results
Insulin has very weak interaction with ZnONP interface. Insulin at studied concentration forms amorphous aggregates at physiological pH, whereas in presence of ZnONP interface amyloid-like fibrils are formed. While the amyloid-like fibrils are cytotoxic to MIN6 and THP-1 cell lines, insulin and ZnONP individual solutions and their fresh mixtures enhance the cells proliferation.Conclusions
The presence of ZnONP interface enhances insulin fibrillation at physiological pH by providing a favourable template for the nucleation and growth of insulin amyloids.General significance
The studied protein-nanoparticle system from protein conformational dynamics point of view throws caution over nanoparticle use in biological applications, especially in vivo applications, considering the amyloidosis a very slow but non-curable degenerative disease. 相似文献87.
P. Nayak 《Journal of Phytopathology》1986,116(2):162-166
Twenty isolates of Xanthomonas campestris pv. oryzae (Ishiyama) Dye each from susceptible and resistant rice cultivars, were inoculated on the susceptible genotype IR-8 and resistant M Sungsong to measure the impact of host selection pressure on virulence change. Isolates virulent on resistant genotype tended to be less adaptive on susceptible cultivars. While isolates from susceptible genotype showed 2.2 times more general virulence (GV) than specific virulence (SV), isolates of resistant host origin had only 1.3 times GV, indicating that the resistant host plant displays considerable increase in virulence. The SV value increased 1.64 times after one cropping with resistants indicated the potential of the pathogen to change to be slow. 相似文献
88.
89.
Ajay P. Nayak Françoise M. Blachere Justin M. Hettick Slawomir Lukomski Detlef Schmechel Donald H. Beezhold 《Mycopathologia》2011,171(1):23-34
Fungal hemolysins are potential virulence factors. Some fungal hemolysins belong to the aegerolysin protein family that includes
cytolysins capable of lysing erythrocytes and other cells. Here, we describe a hemolysin from Aspergillus terreus called terrelysin. We used the genome sequence database to identify the terrelysin sequence based on homology with other
known aegerolysins. Aspergillus terreus mRNA was isolated, transcribed to cDNA and the open reading frame for terrelysin amplified by PCR using specific primers.
Using the pASK-IBA6 cloning vector, we produced recombinant terrelysin (rTerrelysin) as a fusion product in Escherichia coli. The recombinant protein was purified and using MALDI-TOF MS determined to have a mass of 16,428 Da. Circular dichroism analysis
suggests the secondary structure of the protein to be predominantly β-sheet. Results from thermal denaturation of rTerrelysin
show that the protein maintained the β-sheet confirmation up to 65°C. Polyclonal antibody to rTerrelysin recognized a protein
of approximately 16.5 kDa in mycelial extracts from A. terreus. 相似文献
90.
Saswati Nayak Radha Prasanna Boddupalli M. Prasanna Dina B. Sahoo 《World journal of microbiology & biotechnology》2007,23(11):1575-1584
A set of 24 strains belonging to the genus Anabaena (Phylum Cyanobacteria), isolated from diverse geographic locations in India, were evaluated along with three International
type strains of Anabaena (ATCC 29414, ATCC 29208 and ATCC 27899) for their morphological, physiological and biochemical diversity. The morphological
dataset, consisting of 58 variants for 15 characters, and SDS-PAGE protein profiles comprising 17 polymorphic bands were utilized
to differentiate the selected Anabaena strains and explore the patterns of diversity through cluster analysis. Physiological and biochemical characterization with
respect to nitrogen fixation and accumulation of chlorophyll and phycobiliproteins led to the identification of some highly
promising Anabaena strains for use as biofertilizers and source of pigments. The study highlighted the tremendous inter and intraspecific diversity
within the Anabaena isolates and indicated the potential as well as constraints of the morphological and protein profiling datasets for unambiguous
differentiation and analyses of diversity among the Anabaena strains. 相似文献