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   19149篇
  免费   1409篇
  国内免费   1517篇
  22075篇
  2024年   49篇
  2023年   329篇
  2022年   660篇
  2021年   1089篇
  2020年   670篇
  2019年   907篇
  2018年   802篇
  2017年   558篇
  2016年   876篇
  2015年   1153篇
  2014年   1456篇
  2013年   1520篇
  2012年   1809篇
  2011年   1565篇
  2010年   990篇
  2009年   848篇
  2008年   942篇
  2007年   809篇
  2006年   658篇
  2005年   578篇
  2004年   484篇
  2003年   436篇
  2002年   387篇
  2001年   285篇
  2000年   290篇
  1999年   303篇
  1998年   195篇
  1997年   199篇
  1996年   188篇
  1995年   152篇
  1994年   136篇
  1993年   96篇
  1992年   140篇
  1991年   114篇
  1990年   100篇
  1989年   77篇
  1988年   52篇
  1987年   31篇
  1986年   28篇
  1985年   41篇
  1984年   18篇
  1983年   23篇
  1982年   12篇
  1981年   7篇
  1980年   3篇
  1979年   4篇
  1965年   1篇
  1963年   1篇
  1962年   1篇
  1950年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide, and metastasis is the major cause of the high mortality of HCC. In this study, we identified that AnnexinA7 (ANXA7) and Sorcin (SRI) are overexpressed and interacting proteins in HCC tissues and cells. In vitro functional investigations revealed that the interaction between ANXA7 and SRI regulated epithelial–mesenchymal transition (EMT), and then affected migration, invasion, and proliferation in HCC cells. Furthermore overexpression/knockdown of ANXA7 was remarkably effective in promoting/inhibiting tumorigenicity and EMT in vivo. Altogether, our study unveiled a mechanism that ANXA7 promotes EMT by interacting with SRI and further contributes to the aggressiveness in HCC, which provides a novel potential therapeutic target for preventing recurrence and metastasis in HCC.Subject terms: Medical research, Genetics research  相似文献   
62.
Triptolide is a diterpenoid triepoxide derived from the traditional Chinese medical herb Tripterygium wilfordii. In the present study, we demonstrated that this phytochemical attenuated colon cancer growth in vitro and in vivo. Using a proteomic approach, we found that 14‐3‐3 epsilon, a cell cycle‐ and apoptosis‐related protein, was altered in colon cancer cells treated with triptolide. In this regard, triptolide induced cleavage and perinuclear translocation of 14‐3‐3 epsilon. Taken together, our findings suggest that triptolide may merit investigation as a potential therapeutic agent for colon cancer, and its anticancer action may be associated with alteration of 14‐3‐3 epsilon. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   
63.
64.
Protein tyrosine phosphatase 1B (PTP1B) is a major negative regulator of both insulin and leptin signals. For years, inhibiting of PTP1B has been considered to be a potential therapeutics for treating Type 2 diabetes and obesity. Recently, we recognized lithocholic acid (LCA) as a natural inhibitor against PTP1B (IC50 = 12.74 μM) by a vertical screen for the first time. Further SAR research was carried out by synthesizing and evaluating a series of compounds bearing two methyls at C-4 position and a fused heterocycle to ring A. Among them, compound 14b achieved a PTP1B inhibitory activity about eightfold than LCA and a 14-fold selectivity over the homogenous enzyme TCPTP.  相似文献   
65.
66.
67.
H7N9 has caused fatal infections in humans. A safe and effective vaccine is the best way to prevent large-scale outbreaks in the human population. Parainfluenza virus 5 (PIV5), an avirulent paramyxovirus, is a promising vaccine vector. In this work, we generated a recombinant PIV5 expressing the HA gene of H7N9 (PIV5-H7) and tested its efficacy against infection with influenza virus A/Anhui/1/2013 (H7N9) in mice and guinea pigs. PIV5-H7 protected the mice against lethal H7N9 challenge. Interestingly, the protection did not require antibody since PIV5-H7 protected JhD mice that do not produce antibody against lethal H7N9 challenge. Furthermore, transfer of anti-H7 serum did not protect mice against H7N9 challenge. PIV5-H7 generated high HAI titers in guinea pigs, however it did not protect against H7N9 infection or transmission. Intriguingly, immunization of guinea pigs with PIV5-H7 and PIV5 expressing NP of influenza A virus H5N1 (PIV5-NP) conferred protection against H7N9 infection and transmission. Thus, we have obtained a H7N9 vaccine that protected both mice and guinea pigs against lethal H7N9 challenge and infection respectively.  相似文献   
68.
Bombyx batryticatus is a traditional Chinese medicine. To understand apoptotic effect of B. batryticatus ethanol extract (BBE), we investigated the role of BBE in inducing apoptosis of human gastric cancer cells SGC-7901. Cells treated with BBE and apoptosis was assessed by methyl thiazolyl tetrazolium (MTT) assay, morphological changes, DNA fragmentation and flow cytometry assays. The expression of Bcl-2, Bax and P21 were evaluated by western blot analysis and real time polymerase chain reaction. MTT assay showed that the cytotoxicity of BBE extract on SGC-7901 cells was correlated with treatment time and concentration. After treatment with 6 mg/mL of BBE the microscopy showed that, the majority of SGC-7901 cells were obviously reduced, distorted and grew slowly. Annexin-V/propidium iodide double-staining assay emerge the early apoptosis and the late apoptosis after treatment with different times by laser confocal fluorescence microscopy and flow cytometer. Cell cycle analysis of SGC 79 cells showed that BBE induced cell cycle arrest in the G1 and G2 phases. DNA fragmentation indicated the trend of BBE inducing apoptosis on SGC-7901 cells. The qRT-PCR and western blot analysis indicated that the mRNA and protein expressions of Bax and P21 were significantly up-regulated whereas that of Bc1-2 was down-regulated after treatment with BBE for 24 h. Our results revealed a correlation between gene regulation and BBE-induced apoptosis, which might indicate the potential of BBE in cancer therapy.  相似文献   
69.
A study was undertaken to develop a protoplast regeneration system for pinellia. A yield of 19 29 x 105 protoplasts/g F. W. could be obtained from cell suspension cultures incubated in a digestion enzyme solution with 2% cellulase Onzuka R-10, 10% pectinase (Sigma), 0.01% pectolyase Y23. K8P and modified MS media were used to culture protoplasts in: a) liquid, b) liquid-solid double layer, or c) agarose embedded protoplast culture. The former two were conducive to colony formation from protoplast-derived cells. The frequency of cell division was about 8% after 3 days in culture. Gradually adding fresh medium of lower osmotic pressure into the medium for protoplast culture favored cell division. Calli (1–2 mm in diameter) formed after 30–40 days in culture. The calli transferred onto medium supplemented with KT (0.5 mg 1–1) and NAA (0.2 mg 1)–1) could regenerate plants after 40–50 days. Of 47 plantlets transplanted into plots, 29 flowered and were fertile.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - NAA -naphthaleneacetic acid - KT kinetin - CH casein hydrolysate  相似文献   
70.
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