首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   178篇
  免费   12篇
  国内免费   1篇
  2023年   3篇
  2022年   3篇
  2021年   7篇
  2020年   5篇
  2019年   9篇
  2018年   16篇
  2017年   7篇
  2016年   8篇
  2015年   10篇
  2014年   10篇
  2013年   16篇
  2012年   14篇
  2011年   8篇
  2010年   9篇
  2009年   9篇
  2008年   8篇
  2007年   9篇
  2006年   9篇
  2005年   1篇
  2004年   3篇
  2003年   5篇
  2002年   3篇
  2001年   4篇
  2000年   1篇
  1999年   2篇
  1998年   1篇
  1996年   1篇
  1991年   2篇
  1990年   4篇
  1988年   1篇
  1987年   1篇
  1985年   1篇
  1969年   1篇
排序方式: 共有191条查询结果,搜索用时 31 毫秒
111.
The senescence is proposed as a defense mechanism against many anticancer drugs. This complication is marked by differences in cell appearance and inner structures underlying the impairment in function. In this experiment, doxorubicin-induced senescence was assessed in mesenchymal stem cells (MSCs) isolated from the bone marrow of different-aged Balb/c mice (1, 8, and 16 months old). In addition, doxorubicin kinetics in culture medium were investigated to compare the drug absorption rate by different-aged MSCs. Several methods were exerted including Sandwich ELISA for NF-κB activation, propidium iodide staining for cell cycle analysis, Flow-fluorescent in-situ hybridization (Flow-FISH) assay for telomere length measurement, and specific staining for evaluation of β-galactosidase. Determination of doxorubicin in a medium was performed by high-performance liquid chromatography technique. Following doxorubicin exposure, cells underwent substantial telomere shortening, cell cycle arresting in G2 phase, and increased β-galactosidase activity. Interestingly, the enhanced level of NF-κB was observed in all age groups. The highest and lowest sensitivity to telomere shortening attributed to 1- and 8-month-old MSCs, respectively. In consistent with Flow-FISH results, the β-galactosidase activity was higher in young-aged MSCs after treatment. Statistical analysis indicated a correlation between the reduction of telomere length and cessation in G2 phase. Regarding the obtained kinetics equations, the rate of doxorubicin absorption by all aged MSCs followed the same trend. In conclusion, the changing of some elements involved in doxorubicin-induced senescence can be affected by the age of the cells significantly in young MSCs than two other age groups. Hereupon, these changing patterns can open new insights to develop anticancer therapeutic strategies.  相似文献   
112.
BACKGROUND: Plasmacytoma of the bladder is an extremely rare tumor, with all information concerning this neoplasm derived from case reports. It can be a major diagnostic pitfall on both histology and urine cytology. CASE: A 95-year-old woman presented with gross hematuria and a large bladder mass detected by ultrasound. The case was initially misdiagnosed as a high grade urothelial carcinoma. Since the urine cytology did not show the classical cytologic features of urothelial carcinoma, the histologic sections were reviewed and immunohistochemical staining performed. The final diagnosis was plasmacytoma of the bladder. Subsequently the patient underwent a skeletal survey and bone scan, which did not reveal any lesion suspicious for multiple myeloma. The patient was scheduled for radiotherapy. CONCLUSION: In this case of bladder plasmacytoma, urine cytology provided a clue to the diagnosis. Urine cytology can be a diagnostic tool to help make this diagnosis in the case of poorly differentiated bladder neoplasm, especially in a patient with a known history of multiple myeloma.  相似文献   
113.
Human pluripotent embryonic stem cells (hESC) have great promise for research into human developmental biology and the development of cell therapies for the treatment of diseases. To meet the increased demand for characterized hESC lines, we present the derivation and characterization of five hESC lines on mouse embryonic fibroblast cells. Our stem cell lines are characterized by morphology, long-term expansion, and expression profiles of a number of specific markers, including TRA-1-60, TRA-1-81, alkaline phosphatase, connexin 43, OCT-4, NANOG, CXCR4, NODAL, LEFTY2, THY-1, TDGF1, PAX6, FOXD3, SOX2, EPHA2, FGF4, TAL1, AC133 and REX-1. The pluripotency of the cell line was confirmed by spontaneous differentiation under in vitro conditions. Whereas all of the cell lines expressed all the characteristics of undifferentiated pluripotent hESC, two of the cell lines carried a triploid karyotype.  相似文献   
114.
The majority of cell adhesion molecules are N-glycosylated, but the role of N-glycans in intercellular adhesion in epithelia remains ill-defined. Reducing N-glycan branching of cellular glycoproteins by swainsonine, the inhibitor of N-glycan processing, tightens and stabilizes cell-cell junctions as detected by a 3-fold decrease in the paracellular permeability and a 2-3-fold increase in the resistance of the adherens junction proteins to extraction by non-ionic detergent. In addition, exposure of cells to swainsonine inhibits motility of MDCK cells. Mutagenic removal of N-glycosylation sites from the Na,K-ATPase beta(1) subunit impairs cell-cell adhesion and decreases the effect of swainsonine on the paracellular permeability of the cell monolayer and also on detergent resistance of adherens junction proteins, indicating that the extent of N-glycan branching of this subunit is important for intercellular adhesion. The N-glycans of the Na,K-ATPase beta(1) subunit and E-cadherin are less complex in tight renal epithelia than in the leakier intestinal epithelium. The complexity of the N-glycans linked to these proteins gradually decreases upon the formation of a tight monolayer from dispersed MDCK cells. This correlates with a cell-cell adhesion-induced increase in expression of GnT-III (stops N-glycan branching) and a decrease in expression of GnTs IVC and V (promote N-glycan branching) as detected by real-time quantitative PCR. Consistent with these results, partial silencing of the gene encoding GnT-III increases branching of N-glycans linked to the Na,K-ATPase beta(1) subunit and other glycoproteins and results in a 2-fold increase in the paracellular permeability of MDCK cell monolayers. These results suggest epithelial cells can regulate tightness of cell junctions via remodeling of N-glycans, including those linked to the Na,K-ATPase beta(1)-subunit.  相似文献   
115.
Jirds (genus Meriones) comprise a group of rodents, of which the biodiversity is still poorly known. Reason for this is that several species of similar morphologies are known to occur sympatrically. In the north‐west of Iran, four such species occur: Meriones tristrami, Meriones persicus, Meriones vinogradovi and Meriones libycus, prone to several issues of taxonomical ambiguity. A proper characterization of morphological distinctiveness between these species, in relation to the variation within species, could provide the required information for species diagnosis and identification. As some cranial characters of M. tristrami, M. persicus and M. vinogradovi are quite similar, demarcations of species‐specific phenotypic variation have proven to be difficult. To tackle this problem, this study involves a geometric morphometric analysis of skull shape and size, incorporating a large representative sample of these four species, originating from most parts of their natural distribution range (especially for M. tristrami). It is first tested whether M. tristrami can be distinguished from the other sympatric species, and if so, to what degree the species shows a geoclimatic pattern in its skull shape and size when comparing different populations. The shape and size analyses show that M. libycus can be distinguished because of its largest skull and the relatively largest tympanic bulla, and that M. tristrami can be distinguished from the other species. At an intraspecific level in M. tristrami, the Iranian groups (Qazvin and west Iran) do not differ in shape among them, but do so in skull size. They could, however, be distinguished in skull shape from the non‐Iranian populations included (Turkey and Jordan). To what degree this continuous data can now be translated into discrete and diagnostic features, useful for taxonomic purposes, remains to be studied.  相似文献   
116.
Project: This study investigated the in vitro and in vivo effectiveness of biogenic selenium nanoparticles (Se NPs), biosynthesized by Bacillus sp. MSh-1, against Leishmania major (MRHO/IR/75/ER). Procedure: The 3-(4,5-dimethylthiozol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay was used to evaluate the cytotoxicity effects of the biogenic Se NPs against both promastigote and amastigote forms of L. major. In a separate in vivo experiment, we also determined the preventive and therapeutic effects of biogenic Se NPs in BALB/c mice following subcutaneous infected with L. major. Results: The MTT assays showed that the highest toxicity occurred after 72 h against both promastigote and amastigote forms of L. major. The cytotoxicity of Se NPs was higher at all incubation times (24, 48, and 72 h) against the promastigote than the amastigote form (p < 0.05). The 50% inhibitory concentrations (IC50) of the Se NPs were 1.62 ± 0.6 and 4.4 ± 0.6 μg ml?1 against the promastigote and amastigote forms, respectively, after a 72-h incubation period. Apoptosis assays showed DNA fragmentation in promastigotes treated with Se NPs. In an animal challenge, prophylactic doses of biogenic Se NPs delayed the development of localized cutaneous lesions. Moreover, daily administration of Se NPs (5 or 10 mg kg?1 day?1) in similarly infected BALB/c mice that had not received prophylactic doses of Se NPs also abolished the localized lesions after 14 days. Conclusion: Based on these in vitro and in vivo studies, biogenic Se NPs can be considered as a novel therapeutic agent for treatment of the localized lesions typical of cutaneous leishmaniasis.  相似文献   
117.
Mutations in the A-type lamin (LMNA) gene are associated with age-associated degenerative disorders of mesenchymal tissues, such as dilated cardiomyopathy, Emery-Dreifuss muscular dystrophy, and limb-girdle muscular dystrophy. The molecular mechanisms that connect mutations in LMNA with different human diseases are poorly understood. Here, we report the identification of a Muscle-enriched A-type Lamin-interacting Protein, MLIP (C6orf142 and 2310046A06rik), a unique single copy gene that is an innovation of amniotes (reptiles, birds, and mammals). MLIP encodes alternatively spliced variants (23-57 kDa) and possesses several novel structural motifs not found in other proteins. MLIP is expressed ubiquitously and most abundantly in heart, skeletal, and smooth muscle. MLIP interacts directly and co-localizes with lamin A and C in the nuclear envelope. MLIP also co-localizes with promyelocytic leukemia (PML) bodies within the nucleus. PML, like MLIP, is only found in amniotes, suggesting that a functional link between the nuclear envelope and PML bodies may exist through MLIP. Down-regulation of lamin A/C expression by shRNA results in the up-regulation and mislocalization of MLIP. Given that MLIP is expressed most highly in striated and smooth muscle, it is likely to contribute to the mesenchymal phenotypes of laminopathies.  相似文献   
118.
DNA methylation patterns are characterized by highly conserved developmental programs, but allow for divergent gene expression resulting from stochastic epigenetic drift or divergent environments. Genome-wide methylation studies in monozygotic (MZ) twins are providing insight into the extent of epigenetic variation that occurs, irrespective of genotype. However, little is known about the variability of DNA methylation patterns in adolescence, a period involving significant and rapid physical, emotional, social, and neurodevelopmental change. Here, we assessed genome-wide DNA methylation using the 450 K Illumina BeadChip in a sample of 37 MZ twin pairs followed longitudinally since birth to investigate: 1) the extent of variation in DNA methylation in identical genetic backgrounds in adolescence and; 2) whether these variations are randomly distributed or enriched in particular functional pathways. We also assessed stability of DNA methylation over 3–6 months to distinguish stable trait-like and variable state-like genes. A pathway analysis found high within-pair variability in genes associated with development, cellular mechanisms, tissue and cell morphology, and various disorders. Test-retest analyses performed in a sub-sample of 8 twin pairs demonstrated enrichment in gene pathways involved in organismal development, cellular growth and proliferation, cell signaling, and particular disorders. The variability found in functional gene pathways may plausibly underlie phenotypic differences in this adolescent MZ twin sample. Furthermore, we assessed stability of methylation over 3–6 months and found that some genes were stable while others were unstable, suggesting that the methylome remains dynamic in adolescence and that dynamic sites tend to be organized in certain gene pathways.  相似文献   
119.

Background

Indian cultural tradition demanding marriage, many MSM howsoever they self-identify are likely to be married or have sex with women. To consolidate India''s HIV prevention gains, it is important to understand and address the interaction between the MSM and heterosexual epidemics in India and create specific interventions for bisexual MSM. The challenge is to identify and intervene this hard to reach population. Data from HIV Sentinel Surveillance 2011 among MSM in four Indian states were analyzed to assess predictors and prevalence of bisexual behaviour in MSM.

Methods

Between March-May 2011, 4682 men (15–49 years) who had anal/oral sex with a male partner in the past month, attending intervention sites and consenting for an un-linked anonymous survey answered an 11- item questionnaire and provided blood for HIV test by finger stick at 19 designated surveillance sites.

Results

Of 4682 MSM tested overall, 5% were illiterate, 51% reported only receptive anal intercourse, 21% only penetrative and 28% both. 36% MSM had ever received money for sex. Overall 6.8% were HIV infected. 44% MSM were bisexual in the last six months. On multivariate analysis, ‘being bisexual’ was found to be independently associated with ‘older age’: 26–30 years [AOR = 3.1, 95% CI(2.7, 3.7)], >30 years [AOR = 6.5, 95% CI(5.5, 7.7)]; ‘reporting penetrative behaviour alone’ with other men [AOR = 5.8, 95% CI(4.8, 7.0), p<0.01] and ‘reporting both penetrative and receptive behaviour’ [AOR = 2.7, 95% CI(2.3, 3.1) p<0.01]. Those who both paid and received money for sex [AOR = 0.49, 95% CI (0.38, 0.62)] were significantly less likely to be bisexual.

Conclusions

A substantial proportion of men receiving services from Targeted Intervention programs are bisexual and the easy opportunity for intervention in this setting should be capitalised upon. Focusing on older MSM, as well as MSM who show penetrative behaviour with other men, could help in reaching this population.  相似文献   
120.
Two new salts based on heterocyclic organic cations and uranyl triacetate anion were obtained via reaction of zinc uranyl acetate with 2-substituted imidazoles in presence of an excess of acetic acid. Uranyl triacetate anion in [2-MeImH]+ [UO2(CH3COO)3] and [2-PhImH]+ [UO2(CH3COO)3] H2O has an expected bipyramidal structure with linear uranyl group and three acetate groups laying in equatorial plane. [2-MeImH]+ [UO2(CH3COO)3] structure analysis reveals H-bonded 1D chains connected through N-H···O hydrogen bonds. 2-phenylimidazolium in [2-PhImH]+ [UO2(CH3COO)3] H2O demonstrate planar geometry without any rotation of its rings, which was not registered before. H-bonds and π-π interactions of phenyl groups in this system lead to complicate 2D “sandwich” layer formation. The main features of IR- and luminescence spectrum of both compounds are also discussed.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号