全文获取类型
收费全文 | 35007篇 |
免费 | 3273篇 |
国内免费 | 5125篇 |
出版年
2024年 | 52篇 |
2023年 | 452篇 |
2022年 | 696篇 |
2021年 | 1847篇 |
2020年 | 1362篇 |
2019年 | 1740篇 |
2018年 | 1582篇 |
2017年 | 1227篇 |
2016年 | 1663篇 |
2015年 | 2418篇 |
2014年 | 2911篇 |
2013年 | 3008篇 |
2012年 | 3629篇 |
2011年 | 3290篇 |
2010年 | 2110篇 |
2009年 | 1876篇 |
2008年 | 2103篇 |
2007年 | 1890篇 |
2006年 | 1652篇 |
2005年 | 1351篇 |
2004年 | 1105篇 |
2003年 | 1037篇 |
2002年 | 871篇 |
2001年 | 548篇 |
2000年 | 474篇 |
1999年 | 435篇 |
1998年 | 283篇 |
1997年 | 259篇 |
1996年 | 230篇 |
1995年 | 183篇 |
1994年 | 178篇 |
1993年 | 123篇 |
1992年 | 132篇 |
1991年 | 104篇 |
1990年 | 78篇 |
1989年 | 76篇 |
1988年 | 61篇 |
1987年 | 40篇 |
1986年 | 51篇 |
1985年 | 60篇 |
1984年 | 23篇 |
1983年 | 29篇 |
1982年 | 29篇 |
1981年 | 23篇 |
1980年 | 10篇 |
1979年 | 20篇 |
1978年 | 9篇 |
1974年 | 8篇 |
1973年 | 11篇 |
1971年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Hepatocellular carcinoma (HCC) is most prevalent tumor in liver and one of the most fatal cancers in the world. Long noncoding RNAs (lncRNAs) have been accepted as important regulators in carcinomas. But there are still many lncRNAs including DLGAP1-AS1 unannotated in HCC. First of all, GEPIA suggested that DLGAP1-AS1 presented high expression in HCC tissue samples relative to the normal tissues. Besides, overexpression of DLGAP1-AS1 was also proved in HCC cell lines. Moreover, DLGAP1-AS1 knockdown efficiently suppressed cell proliferation in HCC. Interestingly, miR-486-5p was predicted and validated to interact with DLGAP1-AS1, while the level of miR-486-5p was significantly increased In HCC after DLGAP1-AS1 knockdown. Moreover, we uncovered that ectopic expression of miR-486-5p induced suppression on HCC cell proliferation and that miR-486-5p inhibition offset the effect of DLGAP1-AS1 silence on HCC cell proliferation and apoptosis. Furthermore, H3F3B was identified as target of miR-486-5p and was therefore positively regulated by DLGAP1-AS1 in HCC. Of note, H3F3B upregulation partly revived the declined cell proliferative capacity in response to DLGAP1-AS1 knockdown. To conclude, DLGAP1-AS1 exerted its oncogenic role in HCC via miR-486-5p/H3F3B axis. Our new findings provided novel theoretical basis for discovery of therapeutic targets of HCC. 相似文献
993.
Nucleotide composition and synonymous codon usage of open reading frames in Norovirus GII.4 variants
Wei Dan Yan Jin Zizhong Tang Yongmin Li 《Journal of biomolecular structure & dynamics》2020,38(16):4764-4773
AbstractNorovirus GII.4 variants, a genotype in genogroup II belonging to the genus Norovirus, is a single-strand positive sense RNA containing three open reading frames (ORF1, ORF2 and ORF3) and is the most important pathogen causing nonbacterial gastroenteritis outbreaks. By using bioinformatic softwares such as Codon W, SPSS and so on, a total of 292 strains of the viruses isolated from 1974 to 2016 were analyzed for nucleotide composition and synonymous codon usage in each ORF. The result shows that it is enriched for A over the other bases in nucleotide composition, G behind the other bases in the 3rd site of all synonymous codons in the three ORFs. The patterns of nucleotide composition and codon bias of ORF2 are similar to those of ORF3 and different from those of ORF1. There are generally UpA motif and CpG motif in the codons with the lowest proportion. Correspondence analysis indicates that the codon usage may be changing over a certain time period for ORF1 in 2006 and 2012, ORF2 in 2012, and ORF3 in 2013. ENC (effective number of codons) plot and other analyses indicate that both natural selection and mutational pressure play partly roles in the ORFs, but natural selection is more important for ORF2 and ORF3. Besides, we also found all optimal codons in the ORFs. The study provides a basic understanding of the mechanism for norovirus GII.4 codon usage bias. Abbreviations ORF Open Reading Frame ENC Effective Number of Codons COA correspondence analysis RSCU Relative Synonymous Codon Usage CAI Codon Adaptation Index CBI Codon Bias Index Fop frequency of optimal codons L_sym number of synonymous codons L_aa length amino acids GRAVY grand average of hydropathicity Aroma aromaticity Communicated by Ramaswamy H. Sarma 相似文献
994.
995.
996.
997.
Taohong Li Yuchen Xia Xinyue Xu Guoqing Wei Lei Wang 《Archives of insect biochemistry and physiology》2020,105(1):e21724
Bombyx mori nucleopolyhedrovirus (BmNPV) is a primary pathogen in silkworm, and the molecular mechanism of B. mori defense to BmNPV infection is still unclear. RNA interference (RNAi) is well-known as an intracellular conserved mechanism that is critical in gene regulation and cell defense. The antiviral RNAi pathway processes viral double-stranded RNA (dsRNA) into viral small interfering RNAs that guide the recognition and cleavage of complementary viral target RNAs. In this study, a Dicer-2 (Dcr2) gene was identified in B. mori and its antiviral function was explored. Dcr2 messenger RNA (mRNA) expression was the highest in hemocytes and expressed in all stages of silkworm growth. After infection with BmNPV, the expression of Dcr2 mRNA was significantly increased after infection in midgut and hemocytes. The expression of Dcr2 was significantly upregulated by injecting dsRNA (dsBmSPH-1) into silkworm after 48 hr. Knocking down the expression level of Dcr2 using specific dsRNA in silkworm, which modestly enhanced the production of viral genomic DNA. Our results suggested that the Dcr2 gene in B. mori plays an important role in against BmNPV invasion. 相似文献
998.
Hllriegl Vera Barkleit Astrid Spielmann Vladimir Li Wei Bo 《Radiation and environmental biophysics》2020,59(1):121-130
Radiation and Environmental Biophysics - Double tracer studies in healthy human volunteers with stable isotopes of cerium citrate were performed with the aim of investigating the gastro-intestinal... 相似文献
999.
1000.
Li Yan-mei Wang Meng Wang Tian-yun Wei Yong-ge Guo Xiao Mi Chun-liu Zhao Chun-peng Cao Xiang-xiang Dou Yuan-yuan 《Molecular biology reports》2020,47(1):469-475
Molecular Biology Reports - Multicistronic vectors can increase transgene expression and decrease the imbalance of gene expression in the Chinese hamster ovary (CHO) cell expression system. Small,... 相似文献