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   22324篇
  免费   1966篇
  国内免费   2584篇
  26874篇
  2024年   61篇
  2023年   219篇
  2022年   561篇
  2021年   892篇
  2020年   760篇
  2019年   902篇
  2018年   860篇
  2017年   704篇
  2016年   838篇
  2015年   1299篇
  2014年   1643篇
  2013年   1776篇
  2012年   2129篇
  2011年   1971篇
  2010年   1323篇
  2009年   1168篇
  2008年   1538篇
  2007年   1299篇
  2006年   1200篇
  2005年   998篇
  2004年   982篇
  2003年   907篇
  2002年   818篇
  2001年   366篇
  2000年   263篇
  1999年   215篇
  1998年   218篇
  1997年   132篇
  1996年   129篇
  1995年   130篇
  1994年   94篇
  1993年   77篇
  1992年   64篇
  1991年   46篇
  1990年   31篇
  1989年   44篇
  1988年   28篇
  1987年   27篇
  1986年   28篇
  1985年   25篇
  1984年   7篇
  1983年   10篇
  1982年   18篇
  1981年   5篇
  1977年   5篇
  1969年   4篇
  1967年   4篇
  1965年   4篇
  1963年   3篇
  1962年   4篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
151.
152.
Long non-coding RNAs (lncRNAs) act as important regulators of tumorigenesis and development in bladder cancer. However, the underlying molecular mechanisms remain elusive. We previously identified a novel lncRNA signature related to immunity and progression in bladder cancer. Here we further explored the function of RP11-89, a lncRNA discovered in the previous signature. Loss- and gain-of function experiments were performed using CCK-8 assay, flow cytometry, Transwell assays, scratch tests and subcutaneous nude mouse models. High-throughput RNA sequencing was conducted to identify dysregulated genes in bladder cancer cells with RP11-89 knockdown or overexpression. Regulation of RP11-89 on miR-129-5p and PROM2 was explored through luciferase reporter assay, RIP assay and RNA pull-down assay. RP11-89 promoted cell proliferation, migration and tumorigenesis and inhibited cell cycle arrest via the miR-129-5p/PROM2 axis. We found that RP11-89 “sponges” miR-129-5p and upregulates PROM2. Elevated PROM2 in cells was associated with attenuated ferroptosis through iron export, formation of multivesicular bodies and less mitochondrial abnormalities. We demonstrated that RP11-89 is a novel tumorigenic regulator that inhibits ferroptosis via PROM2-activated iron export. RP11-89 may serve as a potential biomarker for targeted therapy in bladder cancer.Subject terms: Tumour biomarkers, Tumour biomarkers  相似文献   
153.
小麦族(Triticeae)是禾本科、早熟禾亚科中一个有重要经济价值、以多年生植物占优势的族,族内绝大多数种类是重要的粮食作物和畜牧业上的优良牧草,饲用价值极高,有些种类具有耐寒、耐旱、耐碱等特性,是农牧业上良种繁育、牧草利用的重要基因资源。但该族同时又是分类学上的一个疑难族,各学者对族内系统分类意见不一、争议颇大,尤其在族的界限、族下类群划分以及类群演化关系上问题较多,至今尚未解决。查阅了国内外分类学文献,探讨其分类差异以及存在问题,为充分开发利用中国丰富的小麦族植物资源提供理论依据。  相似文献   
154.
Aging is an inevitable process that occurs in the whole body system accompanying with many functional and morphological changes. Inflammation is known as one of age-related factors, and inflammatory changes could enhance mortality risk. In this study, we compared immunoreactivities of inflammatory cytokines, such as interleukin (IL)-2 (a pro-inflammatory cytokine), its receptor (IL-2R), IL-4 (an anti-inflammatory cytokine), and its receptor (IL-4R) in the cervical and lumbar spinal cord of young adult (2–3 years old) and aged (10–12 years old) beagle dogs using immunohistochemistry and western blotting. IL-2 and IL-2R-immunoreactive nerve cells were found throughout the gray matter of the cervical and lumbar spinal cord of young adult and aged dogs. In the spinal cord neurons of the aged dog, immunoreactivity and protein levels were apparently increased compared with those in the young adult dog. Change patterns of IL-4- and IL-4R-immunoreactive cells and their protein levels were also similar to those in IL-2 and IL-2R; however, IL-4 and IL-4R immunoreactivity in the periphery of the neuronal cytoplasm in the aged dog was much stronger than that in the young adult dog. These results indicate that the increase of inflammatory cytokines and their receptors in the aged spinal cord might be related to maintaining a balance of inflammatory reaction in the spinal cord during normal aging.  相似文献   
155.
Shen  He  Wu  Shuyu  Chen  Xi  Xu  Bai  Ma  Dezun  Zhao  Yannan  Zhuang  Yan  Chen  Bing  Hou  Xianglin  Li  Jiayin  Cao  Yudong  Fu  Xianyong  Tan  Jun  Yin  Wen  Li  Juan  Meng  Li  Shi  Ya  Xiao  Zhifeng  Jiang  Xingjun  Dai  Jianwu 《中国科学:生命科学英文版》2020,63(12):1879-1886
Science China Life Sciences - Spinal cord injury (SCI), especially complete transected SCI, leads to loss of cells and extracellular matrix and functional impairments. In a previous study, we...  相似文献   
156.
水痘-带状疱疹病毒(varicella zoster virus,VZV)糖蛋白E(glycoprotein E,gE)是VZV亚单位疫苗的主要候选蛋白,但目前原核表达系统制备的gE蛋白以包涵体形式为主,可溶性差。本研究采用去除第1~30氨基酸序列的VZV gE胞外域基因,将其与原核表达载体pET32a连接,并转化至感受态细胞BL21(DE3)中。使用异丙基-β-D-硫代半乳糖苷(Isopropylβ-D-thiogalactoside,IPTG)诱导表达,His-tag柱纯化重组gE蛋白,蛋白质印迹法(Western blot,WB)检测其特异性。用该重组gE蛋白免疫BALB/c小鼠制备多克隆抗体,酶联免疫吸附试验(enzyme linked immunosorbent assay,ELISA)和间接免疫荧光法检测多克隆抗体效价及特异性。结果显示,BL21/pET32a-VZV gE工程菌可以表达可溶性重组gE蛋白,纯化后纯度约为90%。WB鉴定该重组蛋白具有良好的免疫反应性。ELISA检测显示小鼠抗VZV gE多克隆抗体效价>1∶10 000,间接免疫荧光实验结果显示该抗体特异性较高。结果表明,本研究在原核表达系统中成功表达可溶性重组VZV gE蛋白,同时该蛋白具有较强的免疫原性,这为VZV gE亚单位疫苗的研制和大规模生产奠定了基础。  相似文献   
157.
Xu J  Gao J  Li J  Xue L  Clark KJ  Ekker SC  Du SJ 《遗传学报》2012,39(2):69-80
Myofibrillogenesis, the process of sarcomere formation, requires close interactions of sarcomeric proteins and various components of sarcomere structures. The myosin thick filaments and M-lines are two key components of the sarcomere. It has been suggested that myomesin proteins of M-lines interact with myosin and titin proteins and keep the thick and titin filaments in order. However, the function of myomesin in myofibrillogenesis and sarcomere organization remained largely enigmatic. No knockout or knockdown animal models have been reported to elucidate the role of myomesin in sarcomere organization in vivo. In this study, by using the gene-specific knockdown approach in zebrafish embryos, we carried out a loss-of-function analysis of myomesin-3 and slow myosin heavy chain 1 (smyhc1) expressed specifically in slow muscles. We demonstrated that knockdown of smyhc1 abolished the sarcomeric localization of myomesin-3 in slow muscles. In contrast, loss of myomesin-3 had no effect on the sarcomeric organization of thick and thin filaments as well as M- and Z-line structures. Together, these studies indicate that myosin thick filaments are required for M-line organization and M-line localization of myomesin-3. In contrast, myomesin-3 is dispensable for sarcomere organization in slow muscles.  相似文献   
158.
Ma J  Zhang L  Han W  Shen T  Ma C  Liu Y  Nie X  Liu M  Ran Y  Zhu D 《Journal of lipid research》2012,53(6):1093-1105
Pulmonary artery endothelial plexiform lesion is responsible for pulmonary vascular remodeling (PVR), a basic pathological change of pulmonary arterial hypertension (PAH). Recent evidence suggests that epoxyeicosatrienoic acid (EET), which is derived from arachidonic acid by cytochrome p450 (CYP) epoxygenase, has an essential role in PAH. However, until now, most research has focused on pulmonary vasoconstriction; it is unclear whether EET produces mitogenic and angiogenic effects in pulmonary artery endothelial cells (PAEC). Here we found that 500 nM/l 8,9-EET, 11,12-EET, and 14,15-EET markedly augmented JNK and c-Jun activation in PAECs and that the activation of c-Jun was mediated by JNK, but not the ERK or p38 MPAK pathway. Moreover, treatment with 8,9-EET, 11,12-EET, and 14,15-EET promoted cell proliferation and cell-cycle transition from the G0/G1 phase to S phase and stimulated tube formation in vitro. All these effects were reversed after blocking JNK with Sp600125 (a JNK inhibitor) or JNK1/2 siRNA. In addition, the apoptotic process was alleviated by three EET region isomers through the JNK/c-Jun pathway. These observations suggest that 8,9-EET, 11,12-EET, and 14,15-EET stimulate PAEC proliferation and angiogenesis, as well as protect the cells from apoptosis, via the JNK/c-Jun pathway, an important underlying mechanism that may promote PAEC growth and angiogenesis during PAH.  相似文献   
159.
The nectin and nectin-like molecule (Necl) family includes important cell adhesion molecules (CAMs) characterized by their Ig-like nature. Such CAMs regulate a broad spectrum of cell-cell interactions, including the interaction between NK cells and cytotoxic T lymphocytes (CTLs) and their target cells. CAM members nectin-2 (CD112) and Necl-5 (CD155) are believed to form homodimers (for nectin-2) or heterodimers in their functions for cell adhesion, as well as to interact with immune costimulatory receptor DNAX accessory molecule 1 (DNAM-1) (CD226) to regulate functions of both NK and CTL cells. However, the structural basis of the interactive mode of DNAM-1 with nectin-2 or Necl-5 is not yet understood. In this study, a soluble nectin-2 Ig-like V-set domain (nectin-2v) was successfully prepared and demonstrated to bind to both soluble ectodomain and cell surface-expressed full-length DNAM-1. The 1.85-? crystal structure of nectin-2v displays a perpendicular homodimer arrangement, revealing the homodimer characteristics of the nectin and Necls. Further mutational analysis indicated that disruption of the homodimeric interface of nectin-2v led to a failure of the homodimer formation, as confirmed by crystal structure and biochemical properties of the mutant protein of nectin-2v. Interestingly, the monomer mutant also loses DNAM-1 binding, as evidenced by cell staining with tetramers and surface plasmon resonance assays. The data indicate that interaction with DNAM-1 requires either the homodimerization or engagement of the homodimeric interface of nectin-2v. These results have implications for immune intervention of tumors or autoimmune diseases in the DNAM-1/nectin-2-dependent pathway.  相似文献   
160.
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