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   2277篇
  免费   220篇
  国内免费   161篇
  2023年   24篇
  2022年   58篇
  2021年   107篇
  2020年   80篇
  2019年   89篇
  2018年   102篇
  2017年   74篇
  2016年   129篇
  2015年   163篇
  2014年   152篇
  2013年   176篇
  2012年   209篇
  2011年   182篇
  2010年   109篇
  2009年   80篇
  2008年   118篇
  2007年   109篇
  2006年   83篇
  2005年   86篇
  2004年   64篇
  2003年   65篇
  2002年   48篇
  2001年   44篇
  2000年   39篇
  1999年   35篇
  1998年   29篇
  1997年   25篇
  1996年   30篇
  1995年   22篇
  1994年   17篇
  1993年   12篇
  1992年   13篇
  1991年   9篇
  1990年   14篇
  1989年   5篇
  1988年   7篇
  1987年   13篇
  1986年   6篇
  1985年   7篇
  1984年   4篇
  1983年   3篇
  1979年   1篇
  1978年   1篇
  1977年   2篇
  1975年   3篇
  1974年   2篇
  1971年   2篇
  1969年   1篇
  1968年   1篇
  1965年   1篇
排序方式: 共有2658条查询结果,搜索用时 15 毫秒
991.
992.
Cd-induced apoptosis and the protective effects of Se against Cd-induced injury have been reported in previous studies. However, little is known regarding the effects of Cd-induced apoptosis in hepatic cells and the antagonistic effects of Se on Cd in poultry. In the present study, 128 healthy 31-week-old laying hens were randomly divided into four groups, which were fed basic diets, with the addition of Se (Na2SeO3, 2 mg/kg), Cd (CdCl2, 150 mg/kg), or Se + Cd (150 mg/kg of CdCl2 and 2 mg/kg of Na2SeO3) for 90 days. Ultrastructural changes, nitric oxide (NO) concentrations, inducible nitric oxide synthase (iNOS) activities, results of the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay of apoptosis, and the expression of iNOS and apoptosis-related genes in livers were determined. It was observed that Cd treatment significantly increased the concentrations of NO and iNOS activity in chicken livers. The production of excessive NO initiated the mitochondrial apoptotic pathway. Exposure to Cd increased the mRNA and the protein expression levels of iNOS, caspase-3, Bax, p53, and Cyt-c. Furthermore, the ratio of Bax/Bcl-2 increased, while the expression of Bcl-2 decreased. Treatment with Se significantly alleviated Cd-induced apoptosis in chicken livers, as evidenced by a reduction in the production of NO, iNOS activity, the number of apoptotic cells, and mRNA and protein expression levels of iNOS, caspase-3, Bax, and Cyt-c. It indicated that Cd induced NO-mediated apoptosis through the mitochondrial apoptotic pathway and Se exerted antagonizing effects. The present study provides new insights as to how Se affects Cd-induced toxicity in the chicken liver.  相似文献   
993.
994.
To further understand the trends in the evolution of mitochondrial genomes (mitogenomes or mtDNAs) in the Ulvophyceae, the mitogenomes of two separate thalli of Ulva pertusa were sequenced. Two U. pertusa mitogenomes (Up1 and Up2) were 69,333 bp and 64,602 bp in length. These mitogenomes shared two ribosomal RNAs (rRNAs), 28 transfer RNAs (tRNAs), 29 protein‐coding genes, and 12 open reading frames. The 4.7 kb difference in size was attributed to variation in intron content and tandem repeat regions. A total of six introns were present in the smaller U. pertusa mtDNA (Up2), while the larger mtDNA (Up1) had eight. The larger mtDNA had two additional group II introns in two genes (cox1 and cox2) and tandem duplication mutations in noncoding regions. Our results showed the first case of intraspecific variation in chlorophytan mitogenomes and provided further genomic data for the undersampled Ulvophyceae.  相似文献   
995.
996.
<正>Dear Editor,The 2015–2016 outbreak of Zika virus(ZIKV)fever,first reported in Brazil during early 2015(Zanluca et al.,2015),has infected millions of people and is a global public health concern.ZIKV infections are associated with fetal microcephaly,as well as neurological complications  相似文献   
997.
<正>Dear Editor,Coxsackievirus A16(CV A16)and enterovirus 71(EV71)are currently the two primary causative agents of handfoot-and-mouth disease(HFMD)(Solomon et al.,2010;Mao et al.,2014),threatening health of children worldwide.They both belong to the Enterovirus genus of the  相似文献   
998.
999.
While many patients with hereditary optic neuropathies are caused by mitochondrial DNA (mtDNA) mutations of Leber’s hereditary optic neuropathy (LHON), a significant proportion of them does not have mtDNA mutation and is caused by mutations in genes of the nuclear genome. In this study, we investigated whether the OPA1 gene, which is a pathogenic gene for autosomal dominant optic atrophy (ADOA), is frequently mutated in these patients. We sequenced all 29 exons of the OPA1 gene in 105 Han Chinese patients with suspected LHON. mtDNA copy number was quantified in blood samples from patients with and without OPA1 mutation and compared to healthy controls. In silico program-affiliated prediction, evolutionary conservation analysis, and in vitro cellular assays were performed to show the potential pathogenicity of the mutations. We identified nine OPA1 mutations in eight patients; six of them are located in exons and three are located in splicing sites. Mutation c.1172T?>?G has not been reported before. When we combined our data with 193 reported Han Chinese patients with optic neuropathy and compared to the available data of 4327 East Asians by the Exome Aggregation Consortium (ExAC), we found a significant enrichment of potentially pathogenic OPA1 mutations in Chinese patients. Cellular assays for OPA1 mutants c.869G?>?A and c.2708_2711del showed abnormalities in OPA1 isoforms, mitochondrial morphology, and cellular reactive oxygen species (ROS) level. Our results indicated that screening OPA1 mutation is needed for clinical diagnosis of patients with suspected optic neuropathy.  相似文献   
1000.
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