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81.
Gunter HE 《Journal of biomechanics》2004,37(7):1119-1124
Vocal fold tissue lesions such as nodules and polyps are thought to develop in response to mechanical stress that occurs during vocal fold collision. Two computational models of vocal fold collision during voice production are used to investigate this hypothesis. A one-dimensional lumped mass model, whose parameters are derived from vocal fold tissue dimensions and material properties, predicts stress perpendicular to the direction of impact (normal stress). A previously published three-dimensional finite element model that incorporates the same dimensions and properties predicts the entire stress tensor. The hypothesis is supported by predictions from the finite element model that three components of normal stress and one component of shear stress are increased during collision in the typical location of lesions (i.e. the center of the superior medial edge of the vocal fold in the middle of the vibrating and contact region). The lumped mass model predicts that mechanical stress is negatively correlated with mucosal thickness (increased by voice warm-up and hydration), is positively correlated with driving force (proportional to voice intensity), and is affected by voice production method. These relationships are consistent with clinical observations of vocal fold lesion risk factors and have implications for improving prevention and treatment of benign vocal fold lesions. 相似文献
82.
Here we describe protocols for preparing and using fluorescent probes that respond to conformational changes by altered Foerster resonance energy transfer (FRET) efficiencies upon phosphorylation or, in principle, other posttranslational modifications (PTMs). The sensor protein, a truncated version of pleckstrin, is sandwiched between short-wavelength-excitation green fluorescent protein (GFP2) and yellow fluorescent protein (EYFP). As a result of complex conformational changes of the protein upon phosphorylation, the introduction of a second PTM consensus sequence bestows sensitivity to a second modification and yields a dual-parameter probe. The first phase of the protocol lays out the cloning strategy for single- and dual-parameter FRET sensors, including the construction of a versatile platform into which different consensus sequences may be inserted to create diverse probes. Protocols for fluorescence microscopy of the probes in living cells and image processing are also described. Probe preparation takes 7 d; microscopy and image processing take 2 h. 相似文献
83.
Lee SY Munerol B Pollard S Youdim KA Pannala AS Kuhnle GG Debnam ES Rice-Evans C Spencer JP 《Free radical biology & medicine》2006,40(2):323-334
Studies have suggested that diets rich in polyphenols such as flavonoids may lead to a reduced risk of gastrointestinal cancers. We demonstrate the ability of monomeric and dimeric flavanols to scavenge reactive nitrogen species derived from nitrous acid. Both epicatechin and dimer B2 (epicatechin dimer) inhibited nitrous acid-induced formation of 3-nitrotyrosine and the formation of the carcinogenic N-nitrosamine, N-nitrosodimethylamine. The reaction of monomeric and dimeric epicatechin with nitrous acid led to the formation of mono- and di-nitroso flavanols, whereas the reaction with hesperetin resulted primarily in the formation of nitrated products. Although, epicatechin was transferred across the jejunum of the small intestine yielding metabolites, its nitroso form was not absorbed. Dimer B2 but not epicatechin monomer inhibited the proliferation of, and triggered apoptosis in, Caco-2 cells. The latter was accompanied by caspase-3 activation and reductions in Akt phosphorylation, suggesting activation of apoptosis via inhibition of prosurvival signaling. Furthermore, the dinitroso derivative of dimer B2, and to a lesser extent the dinitroso-epicatechin, also induced significant toxic effects in Caco-2 cells. The inhibitory effects on cellular proliferation were paralleled by early inhibition of ERK 1/2 phosphorylation and later reductions in cyclin D1 levels, indicating modulation of cell cycle regulation in Caco-2 cells. These effects highlight multiple routes in which dietary derived flavanols may exert beneficial effects in the gastrointestinal tract. 相似文献
84.
We have investigated the distribution of three heterochromatic proteins [SUppressor of UnderReplication (SUUR), heterochromatin protein 1 (HP1), and SU(VAR)3–9] in chromosomes of nurse cells (NCs) and have compared the data obtained with the distribution of the same proteins in salivary gland (SG) chromosomes. In NC chromosomes, the SU(VAR)3–9 protein was found in pericentric heterochromatin and at 223 sites on euchromatic arms, while in SG chromosomes, it was mainly restricted to the chromocenter. In NC chromosomes, the HP1 and SUUR proteins bind to 331 and 256 sites, respectively, which are almost twice the number of sites in SG chromosomes. The distribution of the HP1 and SU(VAR)3–9 proteins depends on the SuUR gene. A mutation in this gene results in a dramatic decrease in the amount of SU(VAR)3–9 binding sites in autosomes. In the X chromosome, these sites are relocated in comparison to the SuUR
+, and their total number only varies slightly. HP1 binding sites are redistributed in chromosomes of SuUR mutants, and their overall number did not change as considerably as SU(VAR)3–9. These data together point to an interaction of these three proteins in Drosophila NC chromosomes.Electronic Supplementary Material Supplementary material is available for this article at. 相似文献
85.
NirD is part of the nitrite reductase complex NirBD that catalyses the reduction of nitrite to NH3 in nitrate assimilation and anaerobic respiration. The crystal structure analysis of NirD from Mycobacterium tuberculosis shows a double β‐sandwich fold. NirD is related in three‐dimensional structure and sequence to the Rieske proteins; however, it does not contain any Fe–S cluster or other cofactors that might be involved in electron transfer. A cysteine residue at the protein surface, conserved in NirD homologues lacking the iron–sulfur cluster might be important for the interaction with NirB and possibly stabilize one of the Fe–S centers in this subunit. Proteins 2012. © 2012 Wiley Periodicals, Inc. 相似文献
86.
Smith JK Patil CN Patlolla S Gunter BW Booz GW Duhé RJ 《Free radical biology & medicine》2012,52(6):1101-1110
Four cysteine residues (Cys866, Cys917, Cys1094, and Cys1105) have direct roles in cooperatively regulating Janus kinase 2 (JAK2) catalytic activity. Additional site-directed mutagenesis experiments now provide evidence that two of these residues (Cys866 and Cys917) act together as a redox-sensitive switch, allowing JAK2's catalytic activity to be directly regulated by the redox state of the cell. We created several variants of the truncated JAK2 (GST/(NΔ661)rJAK2), which incorporated cysteine-to-serine or cysteine-to-alanine mutations. The catalytic activities of these mutant enzymes were evaluated by in vitro autokinase assays and by in situ autophosphorylation and transphosphorylation assays. Cysteine-to-alanine mutagenesis revealed that the mechanistic role of Cys866 and Cys917 is functionally distinct from that of Cys1094 and Cys1105. Most notable is the observation that the robust activity of the CC866,917AA mutant is unaltered by pretreatment with dithiothreitol or o-iodosobenzoate, unlike all other JAK2 variants previously examined. This work provides the first direct evidence for a cysteine-based redox-sensitive switch that regulates JAK2 catalytic activity. The presence of this redox-sensitive switch predicts that reactive oxygen species can impair the cell's response to JAK-coupled cytokines under conditions of oxidative stress, which we confirm in a murine pancreatic β-islet cell line. 相似文献
87.
Velden J Paust HJ Hoxha E Turner JE Steinmetz OM Wolf G Jabs WJ Özcan F Beige J Heering PJ Schröder S Kneißler U Disteldorf E Mittrücker HW Stahl RA Helmchen U Panzer U 《American journal of physiology. Renal physiology》2012,302(12):F1663-F1673
Interleukin-17A (IL-17) promotes inflammatory renal tissue damage in mouse models of crescentic glomerulonephritis, including murine experimental autoimmune anti-myeloperoxidase glomerulonephritis, which most likely depends on IL-17-producing Th17 cells. In human anti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis, however, the cellular sources of IL-17 remain to be elucidated. Therefore, we analyzed human kidney biopsies of active necrotizing and crescentic ANCA-associated glomerulonephritis by immunohistochemistry using an IL-17-specific antibody and by immunofluorescent colocalization with cell type markers. We detected numerous IL-17-expressing (IL-17(+)) cells in the glomeruli and in the tubulointerstitium. Unexpectedly, most of these IL-17(+) cells were polymorphonuclear neutrophilic granulocytes, while IL-17(+) T cells and IL-17(+) mast cells were present at significantly lower frequencies. IL-17 was not detected in other infiltrating or resident kidney cells. In those patients who had not received immunosuppressive treatment before biopsy, serum creatinine levels were positively correlated with tubulointerstitial IL-17(+) neutrophils as well as IL-17(+) T cells. Furthermore, we could demonstrate that purified human blood neutrophils expressed IL-17 protein and released it upon stimulation in vitro. In conclusion, these results support a pathogenic role for IL-17 in human ANCA-associated glomerulonephritis. Our data suggest that in the acute stage of the disease neutrophils may act as an important immediate-early innate source of IL-17 and may thereby initiate and promote ongoing renal inflammation. IL-17 may thus be a target for treating acute ANCA-associated glomerulonephritis. 相似文献
88.
Eckert GP Renner K Eckert SH Eckmann J Hagl S Abdel-Kader RM Kurz C Leuner K Muller WE 《Molecular neurobiology》2012,46(1):136-150
Increasing evidences suggest that mitochondrial dysfunction plays an important role in the pathogenesis of neurodegenerative diseases including Alzheimer's disease (AD). Alterations of mitochondrial efficiency and function are mainly related to alterations in mitochondrial content, amount of respiratory enzymes, or changes in enzyme activities leading to oxidative stress, mitochondrial permeability transition pore opening, and enhanced apoptosis. More recently, structural changes of the network are related to bioenergetic function, and its consequences are a matter of intensive research. Several mitochondria-targeting compounds with potential efficacy in AD including dimebon, methylene blue, piracetam, simvastatin, Ginkgo biloba, curcumin, and omega-3 polyunsaturated fatty acids have been identified. The majority of preclinical data indicate beneficial effects, whereas most controlled clinical trials did not meet the expectations. Since mitochondrial dysfunction represents an early event in disease progression, one reason for the disappointing clinical results could be that pharmacological interventions might came too late. Thus, more studies are needed that focus on therapeutic strategies starting before severe disease progress. 相似文献
89.
Brain Isoprenoids Farnesyl Pyrophosphate and Geranylgeranyl Pyrophosphate are Increased in Aged Mice 总被引:1,自引:0,他引:1
Hooff GP Wood WG Kim JH Igbavboa U Ong WY Muller WE Eckert GP 《Molecular neurobiology》2012,46(1):179-185
The mevalonate/isoprenoids/cholesterol pathway has a fundamental role in the brain. Increasing age could be associated with specific changes in mevalonate downstream products. Other than age differences in brain cholesterol and dolichol levels, there has been little if any evidence on the short-chain isoprenoids farnesylpyrophosphate (FPP) and geranylgeranylpyrophosphate (GGPP), as well as downstream lipid products. The purpose of the present study was to determine whether brain levels of FPP, GGPP and sterol precursors and metabolites would be altered in aged mice (23?months) as compared to middle-aged mice (12?months) and young mice (3?months). FPP and GGPP levels were found to be significantly higher in brain homogenates of 23-months-old mice. The ratio of FPP to GGPP did not differ among the three age groups suggesting that increasing age does not alter the relative distribution of the two isoprenoids. Gene expression of FPP synthase and GGPP synthase did not differ among the three age groups. Gene expression of HMG-CoA reductase was significantly increased with age but in contrast gene expression of squalene synthase was reduced with increasing age. Levels of squalene, lanosterol and lathosterol did not differ among the three age groups. Desmosterol and 7-dehydroxycholesterol, which are direct precursors in the final step of cholesterol biosynthesis were significantly lower in brains of aged mice. Levels of cholesterol and its metabolites 24S- and 25S-hydroxycholesterol were similar in all three age groups. Our novel find ings on increased FPP and GGPP levels in brains of aged mice may impact on protein prenylation and contribute to neuronal dysfunction observed in aging and certain neurodegenerative diseases. 相似文献
90.
Coïc YM Baleux F Poyraz Ö Thibeaux R Labruyere E Chretien F Sobhani I Lazure T Wyplosz B Schneider G Mulard L Sansonetti PJ Marteyn BS 《The Journal of biological chemistry》2012,287(19):15916-15922
Imaging living cells and organs requires innovative, specific, efficient, and well tolerated fluorescent markers targeting cellular components. Such tools will allow proceeding to the dynamic analysis of cells and the adaptation of tissues to environmental cues. In this study, we have identified and synthesized a novel non-toxic fluorescent marker allowing a specific fluorescent staining of the human colonic mucus. Our strategy to identify a molecule able to specifically bind to the human colonic mucus was on the basis of the mucus adhesion properties of commensal bacteria. We identified and characterized the mucus-binding property of a 70-amino acid domain (MUB(70)) expressed on the surface of Lactobacillus strains. The chemical synthesis of MUB(70) was achieved using the human commensal bacterium Lactobacillus reuteri AF120104 protein as a template. The synthesized Cy5-conjugated MUB(70) marker specifically stained the colonic mucus on fixed human, rabbit, and guinea pig tissues. Interestingly, murine tissue was not stained, suggesting significant differences in the composition of the murine colonic mucus. In addition, this marker stained the mucus of living cultured human colonic cells (HT29-MTX) and human colonic tissue explants. Using a biotinylated derivative of MUB(70), we demonstrated that this peptide binds specifically to Muc2, the most abundant secreted mucin, through its glycosylated moieties. Hence, Cy5-MUB(70) is a novel and specific fluorescent marker for mammalian colonic mucus. It may be used for live imaging analysis but also, as demonstrated in this study, as a marker for the diagnosis and the prognosis of colonic mucinous carcinomas. 相似文献