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61.
Cuellar MA Salas C Cortés MJ Morello A Diego Maya J Preite MD 《Bioorganic & medicinal chemistry》2003,11(12):2489-2497
The Diels-Alder reaction between two polygodial-derived dienes and simple quinones to yield substituted naphtho- and anthraquinones, is described. The in vitro trypanocide activity for the series was determined. Two of the new compounds showed an activity ten and two times higher, respectively, than nifurtimox and benznidazole, the medicines of choice for the treatment of the acute Chagas' disease. 相似文献
62.
Dragusin M Gurgui C Schwarzmann G Hoernschemeyer J van Echten-Deckert G 《Journal of lipid research》2003,44(9):1772-1779
We studied the metabolism of radioactively labeled safingol (l-threo-dihydrosphingosine) in primary cultured neurons, B104 neuroblastoma cells, and Swiss 3T3 fibroblasts, and compared it to that of its natural stereoisomer d-erythro-dihydrosphingosine. Both sphingoid bases are used as biosynthetic precursors for complex sphingolipids, albeit to different rates. Whereas a considerable amount of the natural sphingoid base is also directed to the catabolic pathway (20-66%, cell type dependent), only a minor amount of the nonnatural safingol is subjected to catabolic cleavage, most of it being N-acylated to the respective stereochemical variant of dihydroceramide. Interestingly, N-acylation of safingol to l-threo-dihydroceramide is less sensitive to fumonisin B1 than the formation of the natural d-erythro-dihydroceramide. In addition, safingol-derived l-threo-dihydroceramide, unlike its physiologic counterpart, is not desaturated. Most of it either accumulates in the cells (up to 50%) or is used as a biosynthetic precursor of the respective dihydrosphingomyelin (up to 45%). About 5% is, however, glucosylated and channeled into the glycosphingolipid biosynthetic pathway. Our results demonstrate that, despite its nonnatural stereochemistry, safingol is recognized and metabolized preferentially by enzymes of the sphingolipid biosynthetic pathway. Furthermore, our data suggest that the cytotoxic potential of safingol is reduced rather than enhanced via its metabolic conversion. 相似文献
63.
Challenge of Rhodobacter capsulatus cells with the superoxide propagator methyl viologen resulted in the induction of a diaphorase activity identified as a member of the ferredoxin (flavodoxin)-(reduced) nicotinamide adenine dinucleotide phosphate (NADP(H)) reductase (FPR) family by N-terminal sequencing. The gene coding for Rhodobacter FPR was cloned and expressed in Escherichia coli. Both native and recombinant forms of the enzyme were purified to homogeneity rendering monomeric products of approximately 30 kDa with essentially the same spectroscopic and kinetic properties. They were able to bind and reduce Rhodobacter flavodoxin (NifF) and to mediate typical FPR activities such as the NADPH-driven diaphorase and cytochrome c reductase. 相似文献
64.
Recruitment of MinC,an inhibitor of Z-ring formation,to the membrane in Escherichia coli: role of MinD and MinE
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In Escherichia coli, the min system prevents division away from midcell through topological regulation of MinC, an inhibitor of Z-ring formation. The topological regulation involves oscillation of MinC between the poles of the cell under the direction of the MinDE oscillator. Since the mechanism of MinC involvement in the oscillation is unknown, we investigated the interaction of MinC with the other Min proteins. We observed that MinD dimerized in the presence of ATP and interacted with MinC. In the presence of a phospholipid bilayer, MinD bound to the bilayer and recruited MinC in an ATP-dependent manner. Addition of MinE to the MinCD-bilayer complex resulted in release of both MinC and MinD. The release of MinC did not require ATP hydrolysis, indicating that MinE could displace MinC from the MinD-bilayer complex. In contrast, MinC was unable to displace MinE bound to the MinD-bilayer complex. These results suggest that MinE induces a conformational change in MinD bound to the bilayer that results in the release of MinC. Also, it is argued that binding of MinD to the membrane activates MinC. 相似文献
65.
The single superoxide dismutase of Rhodobacter capsulatus is a cambialistic,manganese-containing enzyme
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Tabares LC Bittel C Carrillo N Bortolotti A Cortez N 《Journal of bacteriology》2003,185(10):3223-3227
The phototrophic bacterium Rhodobacter capsulatus contains a single, oxygen-responsive superoxide dismutase (SOD(Rc)) homologous to iron-containing superoxide dismutase enzymes. Recombinant SOD(Rc), however, displayed higher activity after refolding with Mn(2+), especially when the pH of the assay mixture was raised. SOD(Rc) isolated from Rhodobacter cells also preferentially contains manganese, but metal discrimination depends on the culture conditions, with iron fractions increasing from 7% in aerobic cultures up to 40% in photosynthetic cultures. Therefore, SOD(Rc) behaves as a Mn-containing dismutase with cambialistic properties. 相似文献
66.
This research documents the removal of the dye Gris Lanaset G from aqueous solutions by fungal pellets. Adsorption of the dye by dead biomass pellets of Trametes versicolor was determined and compared with dye removal by enzymatic degradation. Six kinetic equations were fitted to the experimental adsorption data obtained. The results indicate that kinetics such as the Elovich equation, which considers that the rate-controlling step is the diffusion of the dye molecules, show the best fit. Nonlinear Langmuir and Freundlich equations were also fitted into the adsorption data, and it can be concluded that the adsorption equilibrium can be interpreted by the Langmuir isotherm. Adsorption plays an important role in the process of the elimination of color from textile wastewater, although not all of the elimination is due to this physical process when the microorganism is active. The removal of color (around 90%) with active microorganisms is greater than that obtained with the adsorption process. 相似文献
67.
Acrylonitrile (AN) is a vinyl monomer used in the production of synthetic fibers, rubber and plastics. AN is acutely toxic but its mechanism of toxicity remains to be established. AN is metabolized to cyanide in vivo but cyanide production alone cannot explain acute AN toxicity. Previous work in our laboratory has shown that AN can alkylate highly reactive cysteine residues in proteins. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a critical enzyme involved in glycolysis, has a catalytically active cysteine 149 in its active site. We report that AN irreversibly inhibits GAPDH with second-order rate constants, at pH 7.4, of 3.7 and 9.2 M−1 s−1 at 25 and 37 °C, respectively. A combination of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF) and electrospray ionization–mass spectrometry–mass spectrometry (ESI–MS–MS) was used to show that AN inactivates GAPDH by covalently binding to cysteine 149 in the active site of the enzyme. Inactivation of GAPDH by AN would be expected to impair glycolytic ATP production and when coupled with the inhibition of mitochondrial ATP synthesis by the AN metabolite cyanide would result in metabolic arrest. The brain can withstand metabolic arrest for only a few minutes thus these combined actions may account for the acute toxicity of AN in vivo. 相似文献
68.
69.
Astrocytic but not neuronal increased expression and redistribution of parkin during unfolded protein stress 总被引:4,自引:0,他引:4
Parkin is a ubiquitin ligase that facilitates proteasomal protein degradation and is involved in a common autosomal recessive form of Parkinson's disease. Its expression is part of the unfolded protein response in cell lines where its overexpression protects against unfolded protein stress. How parkin expression is regulated in brain primary cells under stress situations is however, less well established. Here, the cellular and subcellular localization of parkin under basal conditions and during unfolded protein stress was investigated in primary cultures of rat astrocytes and hippocampal neurons. Immunofluorescense microscopy and biochemical analysis demonstrated that parkin is mainly associated with the endoplasmic reticulum (ER) in hippocampal neurons while it is associated with Golgi membranes, the nuclei and light vesicles in astrocytes. The constitutive parkin expression was high in neurons as compared with astrocytes. However, unfolded protein stress elicited a selective increase in astrocytic parkin expression and a change in distribution, whereas neuronal parkin remained largely unmodified. The cell specific differences argue in favour of different cellular binding sites and substrates for the protein and a pathogenic role for astrocytes in Parkinson's disease caused by parkin dysfunction. 相似文献
70.
Olive oil mill waste waters decoloration and detoxification in a bioreactor by the white rot fungus Phanerochaete flavido-alba 总被引:1,自引:0,他引:1
Olive oil mill wastewater (OMW) is produced as waste in olive oil extraction. With the purpose of treating this highly polluting waste, a number of experiments were conducted in a laboratory-scale bioreactor with the white rot fungus Phanerochaete flavido-alba (P. flavido-alba). It is known that this fungus is capable of decolorizing OMW in static or semistatic cultures at Erlenmeyer scale and at 30 degrees C. The objective of this work was to prove that P. flavido-alba could decolorize OMW in submerged cultures and that it is capable of reducing OMW toxicity at room temperature (25 degrees C) and in a laboratory-scale bioreactor. In the experiments conducted, manganese peroxidase (MnP) and laccase enzymes were detected; however, unlike other studies, lignin peroxidase was not found to be present. Decoloration obtained after treatment was 70%. The reduction of aromatic compounds obtained was 51%, and the toxicity of the culture medium was reduced by up to 70%. We can therefore state that P. flavido-alba is capable of reducing important environmental parameters of industrial effluents and that prospects are positive for the use of this process at a larger scale, even when working at room temperature. 相似文献