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   119933篇
  免费   2844篇
  国内免费   4626篇
  2024年   82篇
  2023年   402篇
  2022年   876篇
  2021年   1587篇
  2020年   1115篇
  2019年   1414篇
  2018年   12851篇
  2017年   11415篇
  2016年   8526篇
  2015年   2435篇
  2014年   2550篇
  2013年   2662篇
  2012年   6982篇
  2011年   15097篇
  2010年   13482篇
  2009年   9637篇
  2008年   11337篇
  2007年   12763篇
  2006年   1507篇
  2005年   1617篇
  2004年   1846篇
  2003年   1822篇
  2002年   1432篇
  2001年   698篇
  2000年   515篇
  1999年   390篇
  1998年   259篇
  1997年   222篇
  1996年   200篇
  1995年   154篇
  1994年   139篇
  1993年   120篇
  1992年   116篇
  1991年   124篇
  1990年   76篇
  1989年   69篇
  1988年   71篇
  1987年   48篇
  1986年   34篇
  1985年   44篇
  1984年   20篇
  1983年   32篇
  1982年   14篇
  1981年   11篇
  1972年   246篇
  1971年   274篇
  1965年   14篇
  1962年   24篇
  1944年   12篇
  1940年   10篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Heat shock proteins (HSPs) were known as the molecular chaperones, which play a pivotal role in the protein quality control system, ensuring correct folding of proteins, and facilitating the correct refolding of damaged proteins via the transient interaction with their substrate proteins. They also practice in the regulation of cell cycles and are involved in apoptosis. We found that HspB2 was almost completely silent in pancreatic cancer and few studies investigated the role of HspB2 in cancer cells, particularly in pancreatic cancer. Here, we reported that HspB2 effectively inhibited cell proliferation in Panc-1 cells. Specifically, we demonstrated that HspB2 could combine mut-p53 and change the DNA binding site of mutant p53, subsequently upregulated the expression of RPRM, BAI-1, and TSAP6 which were the downstream genes of wt-p53, participate in mediating downstream responses to p53, including inhibiting cell proliferation and angiogenesis. The main aim of this study is to investigate the relationship between HspB2 and p53, and provide a novel treatment strategy for pancreatic cancer.  相似文献   
992.
993.
994.
995.
Abstract

Norovirus 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   
996.
997.
Kamal  Osama M.  Shah  Sayyed Hamad Ahmad  Li  Yan  Hou  Xilin  Li  Ying 《Molecular biology reports》2020,47(9):6887-6897
Molecular Biology Reports - The objective of the present work was the selection of cultivar, suitable medium and explant type for callus, root production, ascorbic acid, total ascorbic acid,...  相似文献   
998.
Li  Wanting  Ye  Anqi  Ao  Luyao  Zhou  Lin  Yan  Yunyi  Hu  Yahui  Fang  Weirong  Li  Yunman 《Neurochemical research》2020,45(10):2258-2277
Neurochemical Research - Stroke is the fifth leading cause of death worldwide and is a main cause of disability in adults. Neither currently marketed drugs nor commonly used treatments can promote...  相似文献   
999.
Tang  Xiangming  Yan  Kunning  Wang  Yingge  Wang  Yaping  Chen  Hongmei  Xu  Jiang  Lu  Yaoyao  Wang  Xiaohong  Liang  Jingyan  Zhang  Xinjiang 《Neurochemical research》2020,45(4):837-850
Neurochemical Research - Brain injury has been proposed as the major cause of the poor outcomes associated with intracerebral hemorrhage (ICH). Emerging evidence indicates that the nuclear...  相似文献   
1000.
Breast cancer is a popularly diagnosed malignant tumor. Genomic profiling studies suggest that breast cancer is a disease with heterogeneity. Chemotherapy is one of the chief means to treat breast cancer, while its responses and clinical outcomes vary largely due to the conventional clinicopathological factors and inherent chemosensitivity of breast cancer. Using the least absolute shrinkage and selection operator (LASSO) Cox regression model, our study established a multi-mRNA-based signature model and constructed a relative nomogram in predicting distant-recurrence-free survival for patients receiving surgery and following chemotherapy. We constructed a signature of eight mRNAs (IPCEF1, SYNDIG1, TIGIT, SPESP1, C2CD4A, CLCA2, RLN2, and CCL19) with the LASSO model, which was employed to separate subjects into groups with high- and low-risk scores. Obvious differences of distant-recurrence-free survival were found between these two groups. This eight-mRNA-based signature was independently associated with the prognosis and had better prognostic value than classical clinicopathologic factors according to multivariate Cox regression results. Receiver operating characteristic results demonstrated excellent performance in diagnosing 3-year distant-recurrence by the eight-mRNA signature. A nomogram that combined both the eight-mRNA-based signature and clinicopathological risk factors was constructed. Comparing with an ideal model, the nomograms worked well both in the training and validation sets. Through the results that the eight-mRNA signature effectively classified patients into low- and high-risk of distant recurrence, we concluded that this eight-mRNA-based signature played a promising predictive role in prognosis and could be clinically applied in breast cancer patients receiving adjuvant chemotherapy.  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