收费全文 | 30074篇 |
免费 | 15674篇 |
国内免费 | 3篇 |
2023年 | 50篇 |
2022年 | 177篇 |
2021年 | 534篇 |
2020年 | 2260篇 |
2019年 | 3806篇 |
2018年 | 3966篇 |
2017年 | 4209篇 |
2016年 | 4236篇 |
2015年 | 4200篇 |
2014年 | 3866篇 |
2013年 | 4403篇 |
2012年 | 2085篇 |
2011年 | 1850篇 |
2010年 | 3271篇 |
2009年 | 1981篇 |
2008年 | 859篇 |
2007年 | 453篇 |
2006年 | 393篇 |
2005年 | 430篇 |
2004年 | 373篇 |
2003年 | 360篇 |
2002年 | 344篇 |
2001年 | 337篇 |
2000年 | 296篇 |
1999年 | 208篇 |
1998年 | 71篇 |
1997年 | 36篇 |
1996年 | 42篇 |
1995年 | 36篇 |
1994年 | 23篇 |
1993年 | 26篇 |
1992年 | 30篇 |
1991年 | 28篇 |
1990年 | 16篇 |
1989年 | 30篇 |
1988年 | 18篇 |
1987年 | 16篇 |
1986年 | 24篇 |
1985年 | 20篇 |
1984年 | 31篇 |
1983年 | 24篇 |
1982年 | 26篇 |
1981年 | 18篇 |
1980年 | 39篇 |
1979年 | 31篇 |
1978年 | 31篇 |
1977年 | 28篇 |
1976年 | 16篇 |
1975年 | 16篇 |
1974年 | 13篇 |
Matrix metallopeptidase 2 (MMP-2) and matrix metallopeptidase 9 (MMP-9) are involved in the breakdown of extracellular matrix in normal physiological processes as well as in disease processes, such as cancer metastasis. We conducted this work to study the role of MMP-2 and MMP-9 in breast cancer by measuring their plasma concentrations before and after surgery. Also, to examine if their levels can reflect the stage of disease and prognosis. Forty-eight breast cancer patients and 13 patients with benign breast diseases were included in the study. MMP-2 and MMP-9 levels were measured by ELISA and semi-quantitative real-time PCR. MMP-2 and MMP-9 levels in plasma were determined by ELISA immediately before surgery and during 6 to 12 months after curative surgery. We observed a significant increase in the level of MMP-9 mRNA expression in breast cancer patients in comparison to their normal breast tissues and to tissues of benign breast disease. In all TNM tumor stages, the plasma levels of MMP-2 and MMP-9 were increased significantly before curative surgery in the studied patients with breast carcinoma and decreased significantly after surgery. Both MMP-2 and MMP-9 may be used as a possible marker for follow-up or as a marker that reflects the response of the disease to treatment.
相似文献Genetic variations of microRNA encoding genes influence various sorts of diseases by modifying the expression or activity of microRNAs. MicroRNA 146a is an epigenetic regulator of immune response through controlling the type I interferon (IFN) and nuclear factor kappa B (NF-κB) pathways. Genetic variations of microRNA 146a impact the susceptibility to systemic lupus erythematosus (SLE) and its clinical presentations. This study aimed to investigate the polymorphisms of microRNA-146a gene (rs2431697 and rs57095329) in patients with SLE and its association with disease activity. Sixty-five patients with SLE and 40 apparently healthy controls were enrolled in this study. Patients were subjected to history taking, clinical examination, and disease activity evaluation by SLEDAI score. The microRNA-146a variants were determined by allele discrimination real-time PCR method in all participants. We found a statistically significant association between rs2431697 T allele and SLE (P-value?<?0.05), but there was no significant association between rs57095329 and SLE. The T/T genotype of microRNA-146a rs2431697 was associated with lupus nephritis, higher disease activity, and autoantibodies production. The microRNA-146a rs2431697 T allele could be a potential risk factor that contributes to SLE susceptibility, development of lupus nephritis, and disease activity.
相似文献