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   130536篇
  免费   23346篇
  国内免费   8803篇
  2024年   55篇
  2023年   1370篇
  2022年   1742篇
  2021年   5515篇
  2020年   5781篇
  2019年   8127篇
  2018年   8072篇
  2017年   7185篇
  2016年   8526篇
  2015年   10622篇
  2014年   11686篇
  2013年   12447篇
  2012年   11927篇
  2011年   10701篇
  2010年   8391篇
  2009年   6781篇
  2008年   6518篇
  2007年   5366篇
  2006年   4676篇
  2005年   3872篇
  2004年   3270篇
  2003年   2963篇
  2002年   2442篇
  2001年   2026篇
  2000年   1788篇
  1999年   1671篇
  1998年   997篇
  1997年   1029篇
  1996年   927篇
  1995年   903篇
  1994年   802篇
  1993年   651篇
  1992年   779篇
  1991年   618篇
  1990年   509篇
  1989年   393篇
  1988年   315篇
  1987年   255篇
  1986年   212篇
  1985年   246篇
  1984年   142篇
  1983年   132篇
  1982年   71篇
  1981年   38篇
  1980年   31篇
  1979年   25篇
  1978年   10篇
  1976年   11篇
  1975年   11篇
  1973年   8篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
72.
73.
Mitochondrial DNA (mtDNA) copy number in peripheral blood has been suggested as risk modifier in various types of cancer. However, its influence on melanoma risk is unclear. We evaluated the association between mtDNA copy number in peripheral blood and melanoma risk in 500 melanoma cases and 500 healthy controls from an ongoing melanoma study. The mtDNA copy number was measured using real-time polymerase chain reaction. Overall, mean mtDNA copy number was significantly higher in cases than in controls (1.15 vs 0.99, P<0.001). Increased mtDNA copy number was associated with a 1.45-fold increased risk of melanoma (95% confidence interval: 1.12-1.97). Significant joint effects between mtDNA copy number and variables related to pigmentation and history of sunlight exposure were observed. This study supports an association between increased mtDNA copy number and melanoma risk that is independent on the known melanoma risk factors (pigmentation and history of sunlight exposure).  相似文献   
74.
75.
In a continuing study of microbial secondary metabolism in simulated microgravity, we have examined gramicidin S (GS) production by Bacillus brevis strain Nagano in NASA High Aspect Rotating Vessels (HARVs), which are designed to simulate some aspects of microgravity. Growth and GS production were found to occur under simulated microgravity. When performance under simulated microgravity was compared with that under normal gravity conditions in the bioreactors, GS production was found to be unaffected by simulated microgravity. The repressive effect of glycerol in flask fermentations was not observed in the HARV. Thus the negative effect of glycerol on specific GS formation is dependent on shear and/or vessel geometry, not gravity. Received: 7 August 1996 / Accepted: 17 September 1996  相似文献   
76.
77.
This study aimed to identify significant biomarkers related to the prognosis of liver cancer using long noncoding RNA (lncRNA)-associated competing endogenous RNAs (ceRNAs) analysis. Differentially expressed mRNA and lncRNAs between liver cancer and paracancerous tissues were screened, and the functions of these mRNAs were predicted by gene ontology and pathway enrichment analyses. A ceRNA network consisting of differentially expressed mRNAs and lncRNAs was constructed. LncRNA FENDRR and lncRNA HAND2-AS1 were hub nodes in the ceRNA network. A risk score assessment model consisting of eight genes (PDE2A, ESR1, FBLN5, ALDH8A1, AKR1D1, EHHADH, ADRA1A, and GNE) associated with prognosis were developed. Multivariate Cox regression suggested that both pathologic_T and risk group could be regarded as independent prognostic factors. Furthermore, a nomogram model consisting of pathologic_T and risk group showed a good prediction ability for predicting the survival rate of liver cancer patients. The nomogram model consisting of pathologic_T and a risk score assessment model could be regarded as an independent factor for predicting prognosis of liver cancer.  相似文献   
78.
79.
Introducing chimeric antigen receptor into immune cells against malignancies has contributed to a revolutionary innovation in cancer immunotherapy. As an important type of adaptive immune cells, T cells first caught researchers' attention and became great success in chimeric antigen receptor-based immunotherapy. However, engineered T cells seem to hit their bottleneck when resistance of cancerous cells, less encouraging responses in solid tumors and unwanted toxicities to the host remain to be solved.Meanwhile, innate immune cells get to join the race. Representatives such as natural killer cells, natural killer T cells, γδT cells and macrophages also prove to be well redirected with chimeric antigen receptors. Compared to chimeric antigen receptor engineered T cells, these engineered innate immune cells may possess multiple targeting and killing mechanisms, have the potential to crack the barrier of solid tumors and have less side effects in the host. Besides, possible universal access to cell resources and improvements in expansion and transduction techniques make these cells promising candidates with huge potential in translational medicine. Therefore, innate immune cells claim a brand-new dimension and are likely to supplement T cells greatly in the field of chimeric antigen receptor-based immunotherapy.  相似文献   
80.
<正>Aristolochic acids, mutational signature, and hepatocellular carcinoma Aristolochic acids (AA) are the etiologic agents of aristolochic acid nephropathy (AAN) and contribute to the global prevalence of chronic kidney disease and urothelial cancer (Grollman et al., 2007). DNA adducts formed by AA generate a unique AT transversions mutation spectrum at  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