全文获取类型
收费全文 | 116931篇 |
免费 | 9285篇 |
国内免费 | 9137篇 |
出版年
2024年 | 146篇 |
2023年 | 1311篇 |
2022年 | 1660篇 |
2021年 | 5610篇 |
2020年 | 3952篇 |
2019年 | 4885篇 |
2018年 | 4689篇 |
2017年 | 3466篇 |
2016年 | 4904篇 |
2015年 | 7155篇 |
2014年 | 8383篇 |
2013年 | 8971篇 |
2012年 | 10742篇 |
2011年 | 9700篇 |
2010年 | 6001篇 |
2009年 | 5323篇 |
2008年 | 6256篇 |
2007年 | 5665篇 |
2006年 | 4945篇 |
2005年 | 3950篇 |
2004年 | 3377篇 |
2003年 | 3140篇 |
2002年 | 2625篇 |
2001年 | 2182篇 |
2000年 | 2014篇 |
1999年 | 1940篇 |
1998年 | 1148篇 |
1997年 | 1090篇 |
1996年 | 1012篇 |
1995年 | 878篇 |
1994年 | 872篇 |
1993年 | 676篇 |
1992年 | 979篇 |
1991年 | 763篇 |
1990年 | 597篇 |
1989年 | 595篇 |
1988年 | 475篇 |
1987年 | 454篇 |
1986年 | 371篇 |
1985年 | 384篇 |
1984年 | 222篇 |
1983年 | 234篇 |
1982年 | 144篇 |
1981年 | 121篇 |
1980年 | 94篇 |
1979年 | 129篇 |
1977年 | 134篇 |
1975年 | 98篇 |
1974年 | 108篇 |
1973年 | 97篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
We have previously reported that in vitro HCV infection of cells of hepatocyte origin attenuates complement system at multiple steps, and attenuation also occurs in chronically HCV infected liver, irrespective of the disease stage. However, none of these regulations alone completely impaired complement pathways. Modulation of the upstream proteins involved in proteolytic processing of the complement cascade prior to convertase formation is critical in promoting the function of the complement system in response to infection. Here, we examined the regulation of C2 complement expression in hepatoma cells infected in vitro with cell culture grown virus, and validated our observations using randomly selected chronically HCV infected patient liver biopsy specimens. C2 mRNA expression was significantly inhibited, and classical C3 convertase (C4b2a) decreased. In separate experiments for C3 convertase function, C3b deposition onto bacterial membrane was reduced using HCV infected patient sera as compared to uninfected control, suggesting impaired C3 convertase. Further, iC3b level, a proteolytically inactive form of C3b, was lower in HCV infected patient sera, reflecting impairment of both C3 convertase and Factor I activity. The expression level of Factor I was significantly reduced in HCV infected liver biopsy specimens, while Factor H level remained unchanged or enhanced. Together, these results suggested that inhibition of C3 convertase activity is an additional cumulative effect for attenuation of complement system adopted by HCV for weakening innate immune response. 相似文献
112.
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
113.
114.
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
115.
116.
117.
Qian Li Chuanyu Li Harry K. Mahtani Jian Du Aashka R. Patel Jack R. Lancaster Jr. 《The Journal of biological chemistry》2014,289(29):19917-19927
Dinitrosyliron complexes (DNIC) have been found in a variety of pathological settings associated with •NO. However, the iron source of cellular DNIC is unknown. Previous studies on this question using prolonged •NO exposure could be misleading due to the movement of intracellular iron among different sources. We here report that brief •NO exposure results in only barely detectable DNIC, but levels increase dramatically after 1–2 h of anoxia. This increase is similar quantitatively and temporally with increases in the chelatable iron, and brief •NO treatment prevents detection of this anoxia-induced increased chelatable iron by deferoxamine. DNIC formation is so rapid that it is limited by the availability of •NO and chelatable iron. We utilize this ability to selectively manipulate cellular chelatable iron levels and provide evidence for two cellular functions of endogenous DNIC formation, protection against anoxia-induced reactive oxygen chemistry from the Fenton reaction and formation by transnitrosation of protein nitrosothiols (RSNO). The levels of RSNO under these high chelatable iron levels are comparable with DNIC levels and suggest that under these conditions, both DNIC and RSNO are the most abundant cellular adducts of •NO. 相似文献
118.
1IntroductionElbo(ECG)offersalotofilllcorralltinfondionforthediagnosisOfheartdis-eases.Berz1,seahaormalEChcax[lrins>llleu"knownsituations,thcycanbeCSUghtinthelongti1Ylecontin~11xHlltoriDg.ndterrnoultonngsystemwhichcanrecord24-hoUrECGdataisoneofeffectiveme~toprovidethefun~.AlthOUghthehag6scaleICmorestohavebeeddevelopepbedeavailabletostorelOngtboeECGdsta,itisveqdifficultyandtioublesomethatalopnUmbeOfdstaisprasersandstoredortiallsillltted.InthedigitedECGdata,thereare… 相似文献
119.
120.