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41.
The influence of Ca2+ mediators (nifedipine, verapamil and prostaglandin F2α) on fluorescence polarization of l-anilino-8-napthalene-sulphonate in dipalmitoyl phosphatidylcholine and dimyristoyl phosphatidylcholine
liposomes was studied at various temperatures to understand the dynamic behaviour of membrane lipids. We also studied the
effect of change in calcium concentration on the fluorescence polarization of the dye in the liposomes. Our results show increase
in polarization (indicative of stiffening of the membrane) in the presence of Ca2+ ions. In the case of dimyristoyl phosphatidylcholine liposomes, all 3 drugs caused decrease in fluorescence polarization
(increase in fluidity of the membrane) with or without Ca2+ ions in the medium. Contrary to this, in the case of dipalmitoyl phosphatidylcholine liposomes, the fluidization effect is
observed for all the 3 drugs in the absence of Ca2+ ions; in the presence of Ca2+ ions stiffening is observed upon addition of nifedipine and verapamil which are antagonists, and fluidization is observed
upon addition of prostaglandin F2α. The role of drug-induced fluidity changes in membranes in therapy planning is discussed in the paper. 相似文献
42.
Cytotoxic lymphocytes (CTL) have been reported to show a range of motility patterns from rapid long-range tracking to complete arrest, but how and whether these kinematics affect their ability to kill target cells is not known. Many in vitro killing assays utilize cell lines and tumour-derived cells as targets, which may be of limited relevance to the kinetics of CTL-mediated killing of somatic cells. Here, live-cell microscopy is used to examine the interactions of CTL and primary murine skin cells presenting antigens. We developed a qualitative and quantitative killing assay using extended-duration fluorescence time-lapse microscopy coupled with large-volume objective software-based data analysis to obtain population data of cell-to-cell interactions, motility and apoptosis. In vivo and ex vivo activated antigen-specific cytotoxic lymphocytes were added to primary keratinocyte targets in culture with fluorometric detection of caspase-3 activation in targets as an objective determinant of apoptosis. We found that activated CTL achieved contact-dependent apoptosis of non-tumour targets after a period of prolonged attachment – on average 21 hours – which was determined by target cell type, amount of antigen, and activation status of CTL. Activation of CTL even without engagement of the T cell receptor was sufficient to mobilise cells significantly above baseline, while the addition of cognate antigen further enhanced their motility. Highly activated CTL showed markedly increased vector displacement, and velocity, and lead to increased antigen-specific target cell death. These data show that the inherent kinematics of CTL correlate directly with their ability to kill non-tumour cells presenting cognate antigen. 相似文献
43.
44.
We have used a bioinformatics approach for the identification and reconstruction of metabolic pathways associated with amino acid metabolism in human mitochondria. Human mitochondrial proteins determined by experimental and computational methods have been superposed on the reference pathways from the KEGG database to identify mitochondrial pathways. Enzymes at the entry and exit points for each reconstructed pathway were identified, and mitochondrial solute carrier proteins were determined where applicable. Intermediate enzymes in the mitochondrial pathways were identified based on the annotations available from public databases, evidence in current literature, or our MITOPRED program, which predicts the mitochondrial localization of proteins. Through integration of the data derived from experimental, bibliographical, and computational sources, we reconstructed the amino acid metabolic pathways in human mitochondria, which could help better understand the mitochondrial metabolism and its role in human health. 相似文献
45.
Nucleosome positioning is an important mechanism for the regulation of eukaryotic gene expression. Folding of the chromatin fiber can influence nucleosome positioning, whereas similar electrostatic mechanisms govern the nucleosome repeat length and chromatin fiber folding in vitro. The position of the nucleosomes is directed either by the DNA sequence or by the boundaries created due to the binding of certain trans-acting factors to their target sites in the DNA. Increasing ionic strength results in an increase in nucleosome spacing on the chromatin assembled by the S-190 extract of Drosophila embryos. In this study, a mutant lac repressor protein R3 was used to find the mechanisms of nucleosome positioning on a plasmid with three R3-binding sites. With increasing ionic strength in the presence of R3, the number of positioned nucleosomes in the chromatin decreased, whereas the internucleosomal spacings of the positioned nucleosomes in a single register did not change. The number of the positioned nucleosomes in the chromatin assembled in vitro over different plasmid DNAs with 1-3 lac operators changed with the relative position and number of the R3-binding sites. We found that in the presence of R3, nucleosomes were positioned in the salt gradient method of the chromatin assembly, even in the absence of a nucleosome-positioning sequence. Our results show that nucleosome-positioning mechanisms are dominant, as the nucleosomes can be positioned even in the absence of regular spacing mechanisms. The protein-generated boundaries are more effective when more than one binding site is present with a minimum distance of approximately 165 bp, greater than the nucleosome core DNA length, between them. 相似文献
46.
47.
Ashoka Sreedhara Ragnar Flengsrud Thor Langsrud Purnima Kaul Vishweshwaraiah Prakash Gerd Elisabeth Vegarud 《Biometals》2010,23(6):1159-1170
Apo and holo forms of lactoferrin (LF) from caprine and bovine species have been characterized and compared with regard to
the structural stability determined by thermal denaturation temperature values (T
m), at pH 2.0–8.0. The bovine lactoferrin (bLF) showed highest thermal stability with a T
m of 90 ± 1°C at pH 7.0 whereas caprine lactoferrin (cLF) showed a lower T
m value 68 ± 1°C. The holo form was much more stable than the apo form for the bLF as compared to cLF. When pH was gradually
reduced to 3.0, the T
m values of both holo bLF and holo cLF were reduced showing T
m values of 49 ± 1 and 40 ± 1°C, respectively. Both apo and holo forms of cLF and bLF were found to be most stable at pH 7.0.
A significant loss in the iron content of both holo and apo forms of the cLF and bLF was observed when pH was decreased from
7.0 to 2.0. At the same time a gradual unfolding of the apo and holo forms of both cLF and bLF was shown by maximum exposure
of hydrophobic regions at pH 3.0. This was supported with a loss in α-helix structure together with an increase in the content
of unordered (aperiodic) structure, while β structure seemed unchanged at all pH values. Since LF is used today as fortifier
in many products, like infant formulas and exerts many biological functions in human, the structural changes, iron binding
and release affected by pH and thermal denaturation temperature are important factors to be clarified for more than the bovine
species. 相似文献
48.
Radhika Tatineni Kiran Kumar Doddapaneni Sailasree Dalavayi Santosh M. Kulkarni Lakshmi Narasu Mangamoori 《Process Biochemistry》2006,41(12):2464-2467
Artemisinin, a sesquiterpene lactone containing an endoperoxide bridge, isolated from Artemisia annua L. is effective against both drug resistant and cerebral malaria causing strains of Plasmodium falciparum. The relative low yields of artemisinin in plants are a serious limitation to the commercialization of the drug. An alternative approach by microbial bioconversion of arteannuin B to artemisinin was carried out by Microbacterium trichotecenolyticum isolated from soil. Crude enzyme extract from cell free extracts were capable of microbial bioconversion of arteannuin B, the immediate precursor of artemisinin, to artemisinin. Attempts have been made to partially purify the proteins involved in bioconversion by ion exchange chromatography. Detection of artemisinin was done by thin layer chromatography, and quantified by HPLC. 相似文献
49.
50.
Damodara Rao M. Purnima A. Ramesh D.V. Ayyanna C. 《World journal of microbiology & biotechnology》2002,18(6):547-550
A combination of chromatofocusing and gel filtration chromatography resulted in a simple purification of -amylase from Bacillus licheniformis. The purification was approximately 77-fold. Identification of the purity was established by SDS–PAGE. Molecular weight and isoelectric point of the purified enzyme were 58 kDa and 7.18 respectively. Western blot analysis confirms the specificity of antibody raised against purified -amylase. 相似文献