全文获取类型
收费全文 | 89275篇 |
免费 | 7424篇 |
国内免费 | 7215篇 |
出版年
2024年 | 215篇 |
2023年 | 1146篇 |
2022年 | 2527篇 |
2021年 | 4379篇 |
2020年 | 2865篇 |
2019年 | 3600篇 |
2018年 | 3459篇 |
2017年 | 2529篇 |
2016年 | 3574篇 |
2015年 | 5367篇 |
2014年 | 6313篇 |
2013年 | 6787篇 |
2012年 | 8038篇 |
2011年 | 7372篇 |
2010年 | 4619篇 |
2009年 | 4034篇 |
2008年 | 4777篇 |
2007年 | 4233篇 |
2006年 | 3768篇 |
2005年 | 3147篇 |
2004年 | 2683篇 |
2003年 | 2368篇 |
2002年 | 2000篇 |
2001年 | 1686篇 |
2000年 | 1463篇 |
1999年 | 1469篇 |
1998年 | 897篇 |
1997年 | 887篇 |
1996年 | 840篇 |
1995年 | 734篇 |
1994年 | 757篇 |
1993年 | 594篇 |
1992年 | 782篇 |
1991年 | 642篇 |
1990年 | 550篇 |
1989年 | 448篇 |
1988年 | 359篇 |
1987年 | 318篇 |
1986年 | 243篇 |
1985年 | 278篇 |
1984年 | 188篇 |
1983年 | 162篇 |
1982年 | 118篇 |
1981年 | 74篇 |
1980年 | 65篇 |
1979年 | 88篇 |
1978年 | 67篇 |
1977年 | 47篇 |
1976年 | 52篇 |
1973年 | 51篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Hsuan-Hwai Lin Yi-Jen Peng Ming-Jiun Tsai Yi-Ying Wu Tsung-Neng Tsai Hsin-Hung Huang Yu-Lueng Shih Wei-Kuo Chang Tsai-Yuan Hsieh 《Journal of cellular physiology》2020,235(2):1689-1699
Activated hepatic stellate cells promote hepatocellular carcinoma (HCC) progression. Hepatic stellate cells play a key role in retinoid metabolism, and activation of stellate cells increases retinoic acid (RA) in the liver. However, the role of RA in HCC proliferation remains unclear. We aimed to analyse the mechanism of RA in HCC proliferation. Thirty-eight patients who had undergone hepatic resection for HCCs were recruited. Paired non-tumour tissues, adjacent and distal to HCCs, were collected, and the RA levels in the tissues were analysed. The mechanisms of RA and HCC proliferation were assessed in liver cancer cell lines by protein and gene expression analyses. Early recurrence of HCC was significantly higher in patients with a higher RA concentration than in those with a lower RA concentration in tissues adjacent to HCCs (61.1% vs. 20%, p = .010). RA promoted HCC cell proliferation and activated the expression of Amphiregulin, a growth factor in hepatocarcinogenesis. The promoter of Amphiregulin contained the binding sites of the RA receptor, RXRα. Wnt signalling also activated the expression of Amphiregulin, and the RA and Wnt pathways acted synergistically to increase the expression of Amphiregulin. Furthermore, RXRα interacted with β-catenin and then translocated to the nucleus to activate Amphiregulin. An increased RA concentration in the tissues adjacent to the tumour was associated with an early recurrence of HCC. RA activated the expression of Amphiregulin, and then promoted HCC proliferation, which might partly contribute to early recurrence of HCC after hepatic resection. 相似文献
82.
Xian-Hui Dong Dong-Xue Ma Tian-Ci Zhang Xiao-Ping He Li-Jun Xu Ya-Lei Liu Hao Li Wei-Juan Gao 《Neurochemical research》2021,46(5):1068-1080
Neurochemical Research - Alzheimer’s disease (AD) process is characterized classically by two hallmark pathologies: β-amyloid (Aβ) plaque deposition and neurofibrillary tangles of... 相似文献
83.
84.
Xin Deng Guoli Zhang Ling Zhang Yan Feng Zehong Li GuangMou Wu Yuhuan Yue Gensong Li Yu Cao Ping Zhu 《PloS one》2015,10(11)
Non-viral gene delivery system with many advantages has a great potential for the future of gene therapy. One inherent obstacle of such approach is the uptake by endocytosis into vesicular compartments. Receptor-mediated gene delivery method holds promise to overcome this obstacle. In this study, we developed a receptor-mediated gene delivery system based on a combination of the Pseudomonas exotoxin A (PE), which has a receptor binding and membrane translocation domain, and the hyperthermophilic archaeal histone (HPhA), which has the DNA binding ability. First, we constructed and expressed the rPE-HPhA fusion protein. We then examined the cytotoxicity and the DNA binding ability of rPE-HPhA. We further assessed the efficiency of transfection of the pEGF-C1 plasmid DNA to CHO cells by the rPE-HPhA system, in comparison to the cationic liposome method. The results showed that the transfection efficiency of rPE-HPhA was higher than that of cationic liposomes. In addition, the rPE-HPhA gene delivery system is non-specific to DNA sequence, topology or targeted cell type. Thus, the rPE-HPhA system can be used for delivering genes of interest into mammalian cells and has great potential to be applied for gene therapy. 相似文献
85.
An insect larval toxin designated CryII is produced by several subspecies of Bacillus thuringiensis and differs from the other major delta-endotoxins in these bacteria in its size, toxicity profile and presence as part of an operon with three open reading frames (ORF). Such an operon from a novel B. thuringiensis isolate has been cloned and differs from one previously characterized in the following ways: (a) the size and number of amino acid repeats in one of the ORFs; (b) the smaller size of the CryII protoxin and the presence of a unique 110-kDa CryII-related antigen; and (c) high larvicidal activity for a particular Lepidopteran but low activity for a Dipteran. Various subclones of this operon were introduced into a plasmid-free B. thuringiensis strain and only the cryII gene was found to be necessary for protoxin accumulation. 相似文献
86.
87.
Plasmonics - We investigate aluminum nanopatch/nanohole arrays surrounded by a dielectric material on plastic substrates for large area color printing. In this specific arrangement, metallic... 相似文献
88.
89.