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   181篇
  免费   10篇
  国内免费   4篇
  195篇
  2023年   1篇
  2022年   6篇
  2021年   15篇
  2020年   6篇
  2019年   10篇
  2018年   10篇
  2017年   6篇
  2016年   9篇
  2015年   18篇
  2014年   19篇
  2013年   16篇
  2012年   20篇
  2011年   12篇
  2010年   6篇
  2009年   1篇
  2008年   5篇
  2007年   7篇
  2006年   7篇
  2005年   6篇
  2004年   4篇
  2003年   5篇
  2002年   3篇
  1995年   1篇
  1994年   2篇
排序方式: 共有195条查询结果,搜索用时 15 毫秒
31.
This paper analyzes data on approximately 30,000 women from a survey in Uttar Pradesh in 1995 together with the data from surveys of public and private providers of healthcare and family planning services. A framework was developed for analyzing the effects of quality of services on utilization, and for understanding the gradual evolution of the healthcare infrastructure. The empirical results from logistic regressions for use of female sterilization and IUD showed significant effects of quality of services in government and private hospitals, and of socioeconomic variables such as education, caste, and an index of household possessions. Secondly, models for infant mortality of children born in the preceding 3-year period showed significant effects of socioeconomic variables, quality of healthcare services and birth spacing. Lastly, analysis of data at a more aggregated (Primary Sampling Unit) level indicated differential effects of economic development on the quality of services available in the public and private facilities.  相似文献   
32.
BACKGROUND: Classification and analysis of congenital heart defects (CHD) in etiologic studies is particularly challenging because of diversity of cardiac phenotypes and underlying developmental mechanisms. We describe an approach to classification for risk assessment of CHD based on developmental and epidemiologic considerations, and apply it to data from the National Birth Defect Prevention Study (NBDPS). METHODS: The classification system incorporated the three dimensions of cardiac phenotype, cardiac complexity, and extracardiac anomalies. The system was designed to facilitate the assessment of simple isolated defects and common associations. A team with cardiologic expertise applied the system to a large sample from the NBDPS. RESULTS: Of the 4,703 cases of CHDs in the NBDPS with birth years 1997 through 2002, 63.6% were simple, isolated cases. Specific associations of CHDs represented the majority of the remainder. The mapping strategy generated relatively large samples for most cardiac phenotypes and provided enough detail to isolate important subgroups of CHDs that may differ by etiology or mechanism. CONCLUSIONS: Classification of CHDs that considers cardiac and extracardiac phenotypes is practically feasible, and yields manageable groups of well-characterized phenotypes. Although best suited for large studies, this approach to classification and analysis can be a flexible and powerful tool in many types of etiologic studies of heart defects.  相似文献   
33.
The nephroprotective effect of coenzyme Q10 and epigallocatechin gallate was investigated in rats with acute renal injury induced by a single nephrotoxic dose of cisplatin. Two days prior to cisplatin administration, epigallocatechin gallate and coenzyme Q10 alone and in four different combinations were given for 6 days. The treatment with antioxidants significantly protected the cisplatin‐induced increase in the levels of blood urea nitrogen and serum creatinine. Both the antioxidants alone or in different combinations significantly compensated the increased malondialdehyde and reduced glutathione levels. Moreover, the decrease in the activities of superoxide dismutase, catalase, and glutathione peroxidase and the concentration of selenium, zinc, and copper ions were significantly attenuated in renal tissue. In conclusion, epigallocatechin gallate and coenzyme Q10 are equally effective against cisplatin‐induced nephrotoxicity, whereas the intervention by combining these two antioxidants was found to be highly effective at low doses in attenuating oxidative stress in rat kidney.  相似文献   
34.
Molecular Biology Reports - The salinity stress tolerance in plants has been studied enormously, reflecting its agronomic relevance. Despite the extensive research, limited success has been...  相似文献   
35.
Human cardiac progenitor cells (hCPC) improve heart function after autologous transfer in heart failure patients. Regenerative potential of hCPCs is severely limited with age, requiring genetic modification to enhance therapeutic potential. A legacy of work from our laboratory with Pim1 kinase reveals effects on proliferation, survival, metabolism, and rejuvenation of hCPCs in vitro and in vivo. We demonstrate that subcellular targeting of Pim1 bolsters the distinct cardioprotective effects of this kinase in hCPCs to increase proliferation and survival, and antagonize cellular senescence. Adult hCPCs isolated from patients undergoing left ventricular assist device implantation were engineered to overexpress Pim1 throughout the cell (PimWT) or targeted to either mitochondrial (Mito-Pim1) or nuclear (Nuc-Pim1) compartments. Nuc-Pim1 enhances stem cell youthfulness associated with decreased senescence-associated β-galactosidase activity, preserved telomere length, reduced expression of p16 and p53, and up-regulation of nucleostemin relative to PimWT hCPCs. Alternately, Mito-Pim1 enhances survival by increasing expression of Bcl-2 and Bcl-XL and decreasing cell death after H2O2 treatment, thereby preserving mitochondrial integrity superior to PimWT. Mito-Pim1 increases the proliferation rate by up-regulation of cell cycle modulators Cyclin D, CDK4, and phospho-Rb. Optimal stem cell traits such as proliferation, survival, and increased youthful properties of aged hCPCs are enhanced after targeted Pim1 localization to mitochondrial or nuclear compartments. Targeted Pim1 overexpression in hCPCs allows for selection of the desired phenotypic properties to overcome patient variability and improve specific stem cell characteristics.  相似文献   
36.
The soybean cyst nematode Heterodera glycines is the most destructive pathogen of soybean in the Unites States. Diversity in the parasitic ability of the nematode allows it to reproduce on nematode-resistant soybean. H. glycines chorismate mutase-1 (Hg-CM-1) is a nematode enzyme with the potential to suppress host plant defense compounds; therefore, it has the potential to enhance the parasitic ability of nematodes expressing the gene. Hg-cm-1 is a member of a gene family where two alleles, Hg-cm-1A and Hg-cm-1B, have been identified. Analysis of the Hg-cm-1 gene copy number revealed that there are multiple copies of Hg-cm-1 alleles in the H. glycines genome. H. glycines inbred lines were crossed to ultimately generate three F2 populations of second-stage juveniles (J2s) segregating for Hg-cm-1A and Hg-cm-1B. Segregation of Hg-cm-1A and 1B approximated a 1:2:1 ratio, which suggested that Hg-cm-1 is organized in a cluster of genes that segregate roughly as a single locus. The F2 H. glycines J2 populations were used to infect nematode-resistant (Hartwig, PI88788, and PI90763) and susceptible (Lee 74) soybean plants. H. glycines grown on Hartwig, Lee 74, and PI90763 showed allelic frequencies similar to Hg-cm-1A/B, but nematodes grown on PI88788 contained predominately Hg-cm-1A allele as a result of a statistically significant drop of Hg-cm-1B in the population. This result suggests that specific Hg-cm-1 alleles, or a closely linked gene, may aid H. glycines in adapting to particular soybean hosts.  相似文献   
37.
Vascular endothelial cells receive proangiogenic or antiangiogenic signals from components of extracellular matrix (ECM) depending upon the situation and many molecular signals can have opposite effects in different vascular beds. Tissue inhibitor of metalloproteinase 1 is antiangiogenic in several tissues, but promotes retinal neovascularization. When cleaved from native collagens, several of the non-collagenous domains (NC1) of basement membrane collagens have antiangiogenic effects in some tissues, but this is context dependent for the NC1 of the alpha 1 chain of collagen IV. It is critical to examine effects in several well-defined model systems before assuming that an ECM component is universally antiangiogenic. In this study, we examined the effects of a recombinant fragment of NC1 of the alpha 2 chain of type IV collagen (alpha2(IV)NC1) in a well-characterized model of ocular neovascularization. Intravitreous or periocular injections of alpha2(IV)NC1 caused selective apoptosis of endothelial cells participating in neovascularization resulting in suppression of neovascularization when the peptide was given prior to onset of new vessel sprouting. Importantly, when the peptide was given after neovascularization had already developed, it caused the new vessels to regress. This suggests that alpha2(IV)NC1, which has previously been shown to suppress tumor angiogenesis in xenograft models, is also a strong antiangiogenic agent in the choroid and is a therapeutic candidate for treatment of neovascular age-related macular degeneration.  相似文献   
38.
Staphylococcus aureus, a major human pathogen, exacerbates allergic disorders, including atopic dermatitis, nasal polyps and asthma, which are characterized by tissue eosinophilia. Eosinophils, via their destructive granule contents, can cause significant tissue damage, resulting in inflammation and further recruitment of inflammatory cells. We hypothesised that the relationship between S. aureus and eosinophils may contribute to disease pathology. We found that supernatants from S. aureus (SH1000 strain) cultures cause rapid and profound eosinophil necrosis, resulting in dramatic cell loss within 2 hours. This is in marked contrast to neutrophil granulocytes where no significant cell death was observed (at equivalent dilutions). Supernatants prepared from a strain deficient in the accessory gene regulator (agr) that produces reduced levels of many important virulence factors, including the abundantly produced α-hemolysin (Hla), failed to induce eosinophil death. The role of Hla in mediating eosinophil death was investigated using both an Hla deficient SH1000-modified strain, which did not induce eosinophil death, and purified Hla, which induced concentration-dependent eosinophil death via both apoptosis and necrosis. We conclude that S. aureus Hla induces aberrant eosinophil cell death in vitro and that this may increase tissue injury in allergic disease.  相似文献   
39.
The cellular response to DNA damage employs multiple dynamic protein modifications to exert rapid and adaptable effects. Substantial work has detailed the roles of canonical checkpoint-mediated phosphorylation in this program. Recent studies have also implicated sumoylation in the DNA damage response; however, a systematic view of the contribution of sumoylation to replication and repair and its interplay with checkpoints is lacking. Here, using a biochemical screen in yeast, we establish that DNA damage-induced sumoylation occurs on a large scale. We identify MRX (Mre11-Rad50-Xrs2) as a positive regulator of this induction for a subset of repair targets. In addition, we find that defective sumoylation results in failure to complete replication of a damaged genome and impaired DNA end processing, highlighting the importance of the SUMO-mediated response in genome integrity. We also show that DNA damage-induced sumoylation does not require Mec1 checkpoint signaling, and the presence of both enables optimal DNA damage resistance.  相似文献   
40.
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