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131.
Streptococcus uberis is an important pathogen that has been implicated in bovine mastitis but the virulence factors associated with pathogenesis are not well understood. The aim of this work was to examine 11 putative and known virulence-associated genes by PCR in 78 S. uberis strains isolated from infected animals in Argentina. Additionally, the distribution of virulence patterns over various herds was determined. Not all genes were present in the strains but all of the detected virulence-associated genes were present in combination. Forty-seven (60.3%) isolates carried seven to 10 virulence-associated genes. Further analysis revealed 58 virulence patterns. Different patterns were found within the same herd and among herds, demonstrating that strains with different virulence patterns were able to cause mastitis. Despite the large number of strains with different virulence patterns, strains with identical patterns was found. Detection of virulence-associated genes in individual S. uberis strains isolated from infected animals revealed one to 10 virulence genes. This may indicate that other virulence factors could be involved. The present study reveals the occurrence and distribution of 11 virulence-associated genes among S. uberis isolates from bovine mastitis in various herds and contributes to a better understanding of the pathogenicity of this bacterium. 相似文献
132.
Platelet activation at sites of vascular injury leads to the formation of a hemostatic plug. Activation of platelets is therefore crucial for normal hemostasis. However, uncontrolled platelet activation may also lead to the formation of occlusive thrombi that can cause ischemic events. Platelets can be activated by soluble molecules including thrombin, TXA2 , adenosine diphosphate (ADP), and serotonin or by adhesive extracellular matrix (ECM) proteins such as von Willebrand factor and collagen. In this article, we review recent advances on the role of galectins in platelet physiology. By acting in either soluble or immobilized form, these glycan-binding proteins trigger platelet activation through modulation of discrete signaling pathways. We also offer new hypotheses and some speculations about the role of platelet-galectin interactions not only in hemostasis and thrombosis but also in inflammation and related diseases such as atherosclerosis and cancer. 相似文献
133.
Takashi Kuriki Hanping Guan Mirta Sivak Jack Preiss 《Journal of Protein Chemistry》1996,15(3):305-313
Analysis of the primary structure of mBEII, with those of other branching and amylolytic enzymes as reference, identifies four highly conserved regions which may be involved in substrate binding and in catalysis. When one of the amino acid residues corresponding to the putative catalytic sites of mBEII, i.e., Asp-386, Glu-441, and Asp-509, was replaced, activity disappeared. These putative catalytic residues are located in three different regions (regions 2–4) of the four highly conserved regions (regions 1–4) which exist in the primary structure of most starch hydrolases and related enzymes, including branching enzymes. Region 3, which contains Glu-441 as one of the putative catalytic residues, was located downstream of the carboxyl-terminal position previously reported. The importance of the carboxyl amino acid residues was also demonstrated by chemical modification of the branching enzyme protein using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide. 相似文献
134.
Achlya robusta sp. nov. was found on litter (floating twigs, leaves, and roots) in an artificial polluted channel, near a petroleum refinery, in Buenos Aires province, Argentina. The species is described, illustrated and compared with other species of the genus. A. robusta produces mainly smooth and papillate, tuberculate or bullate oogonia and monoclinous antheridial branches. It develops spherical and subglobose oogonia, with the oogonial wall yellowish and containing mainly immature oospheres. The oospores are eccentric and ranging from (1) 4-17 (30) per oogonium. 相似文献
135.
Kristina Majsec Petra Cvjetko Sonja Tolić Mirta Tkalec Biljana Balen Mirjana Pavlica 《Acta Physiologiae Plantarum》2016,38(6):142
Heavy metals are generally known to induce oxidative stress, but are rarely strategically studied in an embracive manner, taking into account interplay between their various effects. Furthermore, although metals in the environment are present in mixtures and interact with each other, their combined effects to organisms have been much less studied in comparison to individual effects. Here, we present a complete comprehensive study of cadmium (Cd)/copper (Cu) oxidative stress interactions in Nicotiana tabacum seedlings and adult plants. Plants were treated with Cd (10 and 15 μM), Cu (2.5 and 5 μM) and their combinations; seedlings during 1 month period and adult plants during the period of 7 days. Metal accumulation measurements showed that Cd and Cu influence each other uptake, with Cu reducing Cd translocation to shoots. PCA analysis showed that MDA and carbonyls, biomarkers of oxidative stress, as well as ascorbate peroxidase activity, highly correlated across tissues and with Cd content. Majority of toxic effects were caused by Cd-alone, while addition of Cu often resulted in damage alleviation. However, mixture of high concentrations of both Cd and Cu induced most adverse effects. In conclusion, our results indicate that Cu in lower concentration has antagonistic effect to Cd toxicity, while in higher concentration these metals interact additively in tobacco. 相似文献
136.
Gómez RM Pacienza N Schattner M Habarta A Levander OA Sterin-Borda L 《Biological trace element research》2007,117(1-3):127-138
With the aim to study if selenium (Se) deficiency affects the basal frequency and cardiac response to isoproterenol (ISO),
mice were fed a Se-deficient diet (Se-) or the same diet supplemented with 0.2 ppm Se as sodium selenite (Se+) for 4 wk. Atria
frequency, cyclic AMP (cAMP) accumulation, nitric oxide synthase (NOS) activity, and β-adrenoceptor-binding assay were then
examined. Results showed that Se-mice have both a reduction in atria frequency as well as in cAMP content but higher NOS activity
levels either at basal or after ISO stimulation. These differences were suppressed by feeding Se-mice with a Se-supplemented
diet for 1 wk or by inhibition of inducible nitric oxide synthase (iNOS). Alterations observed after ISO stimulation in atria
of Se-mice were not related to a β-adrenoceptor expression modification because specific radioligand-binding parameters in
cardiac membranes from Se-mice and Se+ mice were similar. The reduced response on rate and cAMP in atria from Se-mice to direct
adenylate cyclase (AC) stimulation by forskolin and the shifted upward levels present in 2-amino-4-methylpyridine-treated
Se-mice is in agreement with a negative crosstalk between iNOS activity and AC activity in Se-mice. 相似文献
137.
Mihovilovic M Robinette JB DeKroon RM Sullivan PM Strittmatter WJ 《Journal of lipid research》2007,48(4):806-815
Withdrawing growth factors or serum from endothelial cells leads to the activation of effector caspases 3 and 7, resulting in apoptotic cell death. HDL protects against caspase induction through sphingosine-1-phosphate (S1P) receptors. This anti-caspase activity of HDL is antagonized by VLDL from apolipoprotein E4 (apoE4) (genotype, APOE4/4; apolipoprotein, apoE) targeted replacement (TR) mice, but not by VLDL from TR APOE3/3 mice, and requires the binding of apoE4-VLDL to an LDL receptor family member. In the absence of HDL, apoE4-VLDL and apoE3-VLDL from TR mice have limited antiapoptotic activity. In contrast, we show here that a high-fat/high-cholesterol/cholate diet (HFD) radically alters this biological activity of VLDL. On HFD, both apoE3-VLDL and apoE4-VLDL (HFD VLDL) inhibit caspase 3/7 activation initiated by serum withdrawal. This activity of HFD VLDL is independent of an LDL receptor family member but requires the activation of S1P(3) receptors, as shown by the ability of pharmacological block of S1P receptors by VPC 23019 and by small interfering RNA-mediated downregulation of S1P(3) receptors to inhibit HFD VLDL anticaspase activity. 相似文献
138.
Extracellular acidosis triggers the maturation of human dendritic cells and the production of IL-12 总被引:3,自引:0,他引:3
Martínez D Vermeulen M von Euw E Sabatté J Maggíni J Ceballos A Trevani A Nahmod K Salamone G Barrio M Giordano M Amigorena S Geffner J 《Journal of immunology (Baltimore, Md. : 1950)》2007,179(3):1950-1959
Although the development of an acidic tissue environment or acidosis is a hallmark of inflammatory processes, few studies analyze the effect of extracellular pH on immune cells. We have previously shown that exposure of murine dendritic cells (DCs) to pH 6.5 stimulates macropinocytosis and cross-presentation of extracellular Ags by MHC class I molecules. We report that the transient exposure of human DCs to pH 6.5 markedly increases the expression of HLA-DR, CD40, CD80, CD86, CD83, and CCR7 and improves the T cell priming ability of DCs. Incubation of DCs at pH 6.5 results in the activation of the PI3K/Akt and the MAPK pathways. Using specific inhibitors, we show that the maturation of DCs induced by acidosis was strictly dependent on the activation of p38 MAPK. DC exposure to pH 6.5 also induces a dramatic increase in their production of IL-12, stimulating the synthesis of IFN-gamma, but not IL-4, by Ag-specific CD4(+) T cells. Interestingly, we find that suboptimal doses of LPS abrogated the ability of pH 6.5 to induce DC maturation, suggesting a cross-talk between the activation pathways triggered by LPS and extracellular protons in DCs. We conclude that extracellular acidosis in peripheral tissues may contribute to the initiation of adaptive immune responses by DCs, favoring the development of Th1 immunity. 相似文献
139.
Mirta E Morales Marta B Santillán Esteban A Jáuregui Gladys M Ciuffo 《Cellular and molecular biology, including cyto-enzymology》2002,48(5):547-555
Nitric oxide (NO) has become an important intracellular and intercellular signal molecule and inhibition of the enzyme which produces NO (NOS, NO synthase) become a major goal for pharmacological researchers. We performed a complete search for the lowest-energy conformations at the AM1 calculation level, for zwitter-ionic species of NOS inhibitors, analogs to L-Arg. The lowest- energy conformations obtained were fully optimized at the ab initio theory levels: HF/3-21G and HF/6-31G*. L-NNA, L-NMA and L-CPA exhibited a conformational behavior quite comparable to that of L-Arg. L-NIL, L-NIO and L-NAME achieved to completely different conformations when compared to L-Arg, L-NIL, highly selective for the inducible isoform of NOS, exhibited conformational as well as charge distribution differences compared to L-Arg. L-NAME and L-NNA are highly selective compounds for the constitutive isoforms. Both compounds share the chain lengths of L-Arg and bear a nitro-substituent over the guanidinium group, which causes changes on the net atomic charges of the N-guanidinium atoms. Moreover, differences were observed on net atomic charges and density distribution analyzed by means of molecular electrostatic potentials (MEPs). These differences might be of great importance at determining the selectivity of the different inhibitors. On the basis of the conformational and molecular properties of the different NOS inhibitors and the selectivity of the analogs studied, we propose the requirements for the different NOS isoforms. 相似文献
140.
Mirta S. de Richard Lucía C. de Figueroa María R. de van Broock 《Current microbiology》1983,8(4):201-203
Petite-like colonies of the petite-negative yeastCandida utilis were obtained after the cells were treated with the mutagenic agent ethidium bromide (Eth-Br) (25 g/ml). The lack of ability to grow on nonfermentable substrates like glycerol, lactate, and ethanol and the tetrazolium assay revealed the respiratory deficiency of two isolated colonies. The mutation frequency was 30 times higher than spontaneous mutation (3×10–5). Doubling time (td) and specific growth rate () of petite-like respiration-deficient mutants were studied in complete medium. A td increase of 1.8 times over that of respiration-sufficient parental cells was attributable to the slower division rate of the petite-like cells. Assimilation and fermentation properties showed the absence of respiratory capacity. Petite-like colonies did not grow on nonfermentable carbon sources that parentalC. utilis readily utilize for growing. 相似文献