全文获取类型
收费全文 | 4764篇 |
免费 | 434篇 |
国内免费 | 4篇 |
专业分类
5202篇 |
出版年
2022年 | 42篇 |
2021年 | 75篇 |
2020年 | 26篇 |
2019年 | 39篇 |
2018年 | 63篇 |
2017年 | 48篇 |
2016年 | 113篇 |
2015年 | 242篇 |
2014年 | 250篇 |
2013年 | 312篇 |
2012年 | 432篇 |
2011年 | 379篇 |
2010年 | 201篇 |
2009年 | 176篇 |
2008年 | 235篇 |
2007年 | 244篇 |
2006年 | 231篇 |
2005年 | 211篇 |
2004年 | 198篇 |
2003年 | 171篇 |
2002年 | 162篇 |
2001年 | 148篇 |
2000年 | 136篇 |
1999年 | 106篇 |
1998年 | 50篇 |
1997年 | 39篇 |
1996年 | 40篇 |
1995年 | 30篇 |
1994年 | 30篇 |
1993年 | 31篇 |
1992年 | 70篇 |
1991年 | 70篇 |
1990年 | 59篇 |
1989年 | 61篇 |
1988年 | 58篇 |
1987年 | 60篇 |
1986年 | 37篇 |
1985年 | 20篇 |
1984年 | 31篇 |
1983年 | 22篇 |
1982年 | 14篇 |
1981年 | 17篇 |
1979年 | 26篇 |
1978年 | 23篇 |
1977年 | 14篇 |
1976年 | 17篇 |
1975年 | 18篇 |
1974年 | 23篇 |
1973年 | 22篇 |
1972年 | 11篇 |
排序方式: 共有5202条查询结果,搜索用时 0 毫秒
991.
Datsen George Wei Vicki Chiang Elizabeth Fyne Mini Balakrishnan Tiffany Barnes Michael Graupe Joseph Hesselgesser Alivelu Irrinki Jeffrey P. Murry George Stepan Kirsten M. Stray Angela Tsai Helen Yu Jonathan Spindler Mary Kearney Celsa A. Spina Deborah McMahon Jacob Lalezari Derek Sloan John Mellors Romas Geleziunas Tomas Cihlar 《PLoS pathogens》2014,10(4)
Persistent latent reservoir of replication-competent proviruses in memory CD4 T cells is a major obstacle to curing HIV infection. Pharmacological activation of HIV expression in latently infected cells is being explored as one of the strategies to deplete the latent HIV reservoir. In this study, we characterized the ability of romidepsin (RMD), a histone deacetylase inhibitor approved for the treatment of T-cell lymphomas, to activate the expression of latent HIV. In an in vitro T-cell model of HIV latency, RMD was the most potent inducer of HIV (EC50 = 4.5 nM) compared with vorinostat (VOR; EC50 = 3,950 nM) and other histone deacetylase (HDAC) inhibitors in clinical development including panobinostat (PNB; EC50 = 10 nM). The HIV induction potencies of RMD, VOR, and PNB paralleled their inhibitory activities against multiple human HDAC isoenzymes. In both resting and memory CD4 T cells isolated from HIV-infected patients on suppressive combination antiretroviral therapy (cART), a 4-hour exposure to 40 nM RMD induced a mean 6-fold increase in intracellular HIV RNA levels, whereas a 24-hour treatment with 1 µM VOR resulted in 2- to 3-fold increases. RMD-induced intracellular HIV RNA expression persisted for 48 hours and correlated with sustained inhibition of cell-associated HDAC activity. By comparison, the induction of HIV RNA by VOR and PNB was transient and diminished after 24 hours. RMD also increased levels of extracellular HIV RNA and virions from both memory and resting CD4 T-cell cultures. The activation of HIV expression was observed at RMD concentrations below the drug plasma levels achieved by doses used in patients treated for T-cell lymphomas. In conclusion, RMD induces HIV expression ex vivo at concentrations that can be achieved clinically, indicating that the drug may reactivate latent HIV in patients on suppressive cART. 相似文献
992.
993.
994.
Meng-Ya Chang Yu-Shan Yang Mei-Ling Tsai Che-Hsin Lee Chih-Jui Chang Ai-Li Shiau Chao-Liang Wu 《International journal of biological sciences》2014,10(4):358-366
Prothymosin α (ProT) is involved in regulating expression of the oxidative stress-protective genes and it also exerts immunomodulatory activities. In this study, we investigated the therapeutic effects of ProT gene transfer on atherosclerosis in endothelial cells and in ApoE-deficient mice. Adenoviruses encoding mouse ProT (AdProT) were used for the management of atherosclerosis. In vitro, the effects of ProT on antioxidant gene expressions and the protection effect against oxidant-mediated injury in endothelial cells were examined. In vivo, AdProT were administered intraventricularly into the heart of ApoE-/- mice. Histopathological and immunohistochemical assessments of the aortic tissues were performed. Expressions of HO-1 and antioxidant genes in the aortic tissues were also determined. Our results demonstrated that ProT gene transfer increased antioxidant gene expressions, eNOS expression and NO release, as well as reduced the reactive oxygen species production in endothelial cells. Intraventricular administration of AdProT reduced the lesion formation, increased expressions of HO-1 and SOD genes, and reduced infiltrating macrophages in the aorta of ApoE-/- mice. This study suggests that ProT gene transfer may have the therapeutic potential for the management of atherosclerosis via inducing antioxidant gene expressions, eNOS expression and NO release, reducing ROS production and macrophage infiltration in endothelium. 相似文献
995.
Ting-Yu Chang Tse-Shun Huang Hsei-Wei Wang Shing-Jyh Chang Hung-Hao Lo Ya-Lin Chiu Yen-Li Wang Chung-Der Hsiao Chin-Han Tsai Chia-Hao Chan Ren-In You Chun-Hsien Wu Tsung-Neng Tsai Shu-Meng Cheng Cheng-Chung Cheng 《BMC genomics》2014,15(1)
Background
Endothelial progenitor cells (EPCs) play a fundamental role in not only blood vessel development but also post-natal vascular repair. Currently EPCs are defined as early and late EPCs based on their biological properties and their time of appearance during in vitro culture. Both EPC types assist angiogenesis and have been linked to ischemia-related disorders, including coronary artery disease (CAD).Results
We found late EPCs are more mobile than early EPCs and matured endothelial cells (ECs). To pinpoint the mechanism, microRNA profiles of early EPCs late EPCs, and ECs were deciphered by small RNA sequencing. Obtained signatures made up of both novel and known microRNAs, in which anti-angiogenic microRNAs such as miR-221 and miR-222 are more abundant in matured ECs than in late EPCs. Overexpression of miR-221 and miR-222 resulted in the reduction of genes involved in hypoxia response, metabolism, TGF-beta signalling, and cell motion. Not only hamper late EPC activities in vitro, both microRNAs (especially miR-222) also hindered in vivo vasculogenesis in a zebrafish model. Reporter assays showed that miR-222, but not miR-221, targets the angiogenic factor ETS1. In contrast, PIK3R1 is the target of miR-221, but not miR-222 in late EPCs. Clinically, both miR-221-PIK3R1 and miR-222-ETS1 pairs are deregulated in late EPCs of CAD patients.Conclusions
Our results illustrate EPCs and ECs exploit unique miRNA modalities to regulate angiogenic features, and explain why late EPC levels and activities are reduced in CAD patients. These data will further help to develop new plasma biomarkers and therapeutic approaches for ischemia-related diseases or tumor angiogenesis.Electronic supplementary material
The online version of this article (doi:10.1186/1471-2164-15-802) contains supplementary material, which is available to authorized users. 相似文献996.
Yin-Yu Chang Heng-Li Huang Ya-Chi Chen Jui-Ting Hsu Tzong-Ming Shieh Ming-Tzu Tsai 《PloS one》2014,9(4)
Tantalum (Ta) is a promising metal for biomedical implants or implant coating for orthopedic and dental applications because of its excellent corrosion resistance, fracture toughness, and biocompatibility. This study synthesizes biocompatible tantalum carbide (TaC) and TaC/amorphous carbon (a-C) coatings with different carbon contents by using a twin-gun magnetron sputtering system to improve their biological properties and explore potential surgical implant or device applications. The carbon content in the deposited coatings was regulated by controlling the magnetron power ratio of the pure graphite and Ta cathodes. The deposited TaC and TaC/a-C coatings exhibited better cell viability of human osteosarcoma cell line MG-63 than the uncoated Ti and Ta-coated samples. Inverted optical and confocal imaging was used to demonstrate the cell adhesion, distribution, and proliferation of each sample at different time points during the whole culture period. The results show that the TaC/a-C coating, which contained two metastable phases (TaC and a-C), was more biocompatible with MG-63 cells compared to the pure Ta coating. This suggests that the TaC/a-C coatings exhibit a better biocompatible performance for MG-63 cells, and they may improve implant osseointegration in clinics. 相似文献
997.
Ai-Lin Chen Chu-Yin Liu Chien-Hua Chen Jaw-Fen Wang Yu-Chen Liao Chia-Hui Chang Mong-Hsun Tsai Kae-Kang Hwu Kai-Yi Chen 《PloS one》2014,9(5)
Tomato late blight caused by the oomycete pathogen Phytophthora infestans (Mont.) de Bary is a major threat to tomato production in cool and wet environments. Intensified outbreaks of late blight have been observed globally from the 1980s, and are associated with migration of new and more aggressive populations of P. infestans in the field. The objective of this study was to reassess late blight resistance in the wild tomato accession L3708 (Solanum pimpinellifolium L.) against pathogens of different aggressiveness. An F2:3 genetic mapping population was developed using L3708 as the paternal parent. Two isolates of P. infestans, Pi39A and Pi733, were used for inoculation. Pi733 is a highly aggressive genotype that defeats three known late blight resistance genes, Ph-1, Ph-2, and Ph-5t in tomato. In contrast, Pi39A is a less aggressive genotype that defeats only Ph-1. Restriction site Associated DNA Sequencing (RAD-Seq) technology was used to massively sequence 90 bp nucleotides adjacent to both sides of PstI restriction enzyme cutting sites in the genome for all individuals in the genetic mapping population. The RAD-seq data were used to construct a genetic linkage map containing 440 single nucleotide polymorphism markers. Quantitative trait locus (QTL) analysis identified a new disease-resistant QTL specific to Pi733 on chromosome 2. The Ph-3 gene located on chromosome 9 could be detected whichever isolates were used. This study demonstrated the feasibility and efficiency of RAD-Seq technology for conducting a QTL mapping experiment using an F2:3 mapping population, which allowed the identification of a new late blight resistant QTL in tomato. 相似文献
998.
Tung-Han Tsai Shou-Chuan Shih Tsung-Chuan Ho Hsin-I Ma Ming-Ying Liu Show-Li Chen Yeou-Ping Tsao 《PloS one》2014,9(4)
Pigment epithelium-derived factor (PEDF) has been shown previously to prevent liver fibrosis and hepatic stellate cell (HSC) activation. By investigating the functional domains in PEDF, we identified a 34-mer peptide (residues Asp44-Asn77) that harbors the same function as the full-length PEDF protein. Not only did the 34-mer suppress the development of fibrosis in carbon tetrachloride (CCl4)-treated mouse liver but it also upregulated peroxisome proliferator-activated receptor-gamma (PPARγ) expression in HSCs in vivo. Platelet-derived growth factor (PDGF) plays a crucial role on the process of HSC activation in response to liver damage. The 34-mer suppressed PDGF-induced cell proliferation and expression of myofibroblastic marker proteins in primary rat HSC culture, increased the levels of PPARγ mRNA and protein in a dose-dependent manner and markedly reduced the level of active β-catenin protein, an HSC activating factor, in HSC-T6 cells. Similarly, IWR-1, an inhibitor of the Wnt response, displayed the same effect as the 34-mer in preventing HSC-T6 activation. The Wnt signaling-mediated PPARγ suppression was abolished by both the IWR-1 inhibitor and a small interfering RNA (siRNA) targeting β-catenin and the Wnt coreceptor, LRP6. Both PEDF and the 34-mer down-regulated PDGF receptor-α/β expression and blocked the PDGF-induced phosphorylation of Akt and ERK. Moreover, the inhibitory effect on PDGF receptor expression was abolished by PPARγ antagonists and PPARγ siRNA. Our observations indicate that the PEDF-derived 34-mer peptide can mimic PEDF in attenuating HSC activation. Investigation of this 34-mer peptide led to the identification of a signaling mechanism involving PPARγ induction, suppression of Wnt/β-catenin signaling and down-regulation of the PDGF receptor-α/β. 相似文献
999.
Feng-Yen Lin Fung-Ping Hsiao Chun-Yao Huang Chun-Ming Shih Nai-Wen Tsao Chien-Sung Tsai Shue-Fen Yang Nen-Chung Chang Shan-Ling Hung Yi-Wen Lin 《PloS one》2014,9(7)
Porphyromonas gingivalis is a major periodontal pathogen that contains a variety of virulence factors. The antibody titer to P. gingivalis GroEL, a homologue of HSP60, is significantly higher in periodontitis patients than in healthy control subjects, suggesting that P. gingivalis GroEL is a potential stimulator of periodontal disease. However, the specific role of GroEL in periodontal disease remains unclear. Here, we investigated the effect of P. gingivalis GroEL on human periodontal ligament (PDL) cells in vitro, as well as its effect on alveolar bone resorption in rats in vivo. First, we found that stimulation of PDL cells with recombinant GroEL increased the secretion of the bone resorption-associated cytokines interleukin (IL)-6 and IL-8, potentially via NF-κB activation. Furthermore, GroEL could effectively stimulate PDL cell migration, possibly through activation of integrin α1 and α2 mRNA expression as well as cytoskeletal reorganization. Additionally, GroEL may be involved in osteoclastogenesis via receptor activator of nuclear factor κ-B ligand (RANKL) activation and alkaline phosphatase (ALP) mRNA inhibition in PDL cells. Finally, we inoculated GroEL into rat gingiva, and the results of microcomputed tomography (micro-CT) and histomorphometric assays indicated that the administration of GroEL significantly increased inflammation and bone loss. In conclusion, P. gingivalis GroEL may act as a potent virulence factor, contributing to osteoclastogenesis of PDL cells and resulting in periodontal disease with alveolar bone resorption. 相似文献
1000.
Jeng-Sen Tseng Chih-Liang Wang Ming-Shyan Huang Chung-Yu Chen Cheng-Yu Chang Tsung-Ying Yang Chi-Ren Tsai Kun-Chieh Chen Kuo-Hsuan Hsu Meen-Hsin Tsai Sung-Liang Yu Kang-Yi Su Chih-Wei Wu Cheng-Ta Yang Yuh-Min Chen Gee-Chen Chang 《PloS one》2014,9(9)