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   20123篇
  免费   1747篇
  国内免费   2358篇
  2024年   57篇
  2023年   306篇
  2022年   643篇
  2021年   1046篇
  2020年   720篇
  2019年   893篇
  2018年   900篇
  2017年   702篇
  2016年   866篇
  2015年   1281篇
  2014年   1612篇
  2013年   1631篇
  2012年   1943篇
  2011年   1730篇
  2010年   1066篇
  2009年   996篇
  2008年   1142篇
  2007年   959篇
  2006年   876篇
  2005年   664篇
  2004年   557篇
  2003年   499篇
  2002年   399篇
  2001年   264篇
  2000年   250篇
  1999年   197篇
  1998年   172篇
  1997年   151篇
  1996年   146篇
  1995年   114篇
  1994年   102篇
  1993年   85篇
  1992年   124篇
  1991年   94篇
  1990年   103篇
  1989年   77篇
  1988年   73篇
  1987年   55篇
  1986年   51篇
  1985年   69篇
  1984年   79篇
  1983年   44篇
  1982年   49篇
  1981年   50篇
  1980年   29篇
  1979年   31篇
  1978年   31篇
  1977年   28篇
  1974年   27篇
  1973年   28篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Chen  Bo  Hua  Zhongyan  Qin  Xiuni  Li  Zhijie 《Neurochemical research》2021,46(2):197-212
Neurochemical Research - Neuroblastomas (NB) are childhood malignant tumors originating in the sympathetic nervous system. MicroRNAs (miRNAs) play an essential regulatory role in tumorigenesis and...  相似文献   
992.
Zhang  Heng-Sheng  Ouyang  Bo  Ji  Xiong-Ying  Liu  Mei-Fang 《Neurochemical research》2021,46(7):1747-1758

Cerebral ischaemia/reperfusion (I/R) injury-induced irreversible brain injury is a major cause of mortality and functional impairment in ageing people. Gastrodin (GAS), derived from the traditional Chinese herbal medicine Tianma, has been reported to inhibit the progression of stroke, but the mechanism whereby GAS modulates the progression of cerebral I/R remains unclear. The middle cerebral artery occlusion method was used as a model of I/R in vivo. Rats were pretreated with GAS by intraperitoneal injection 7 days before I/R surgery and were then treated with GAS for 7 days after I/R surgery. Additionally, an oxygen–glucose deprivation/reoxygenation model using neuronal cells was established in vitro to simulate I/R injury. 2,3,5-Triphenyltetrazolium chloride and Nissl staining were used to evaluate infarct size and neuronal damage, respectively. Lactate dehydrogenase release and cell counting kit-8 assays were used to assess neuronal cell viability. Enzyme-linked immunosorbent assay, qPCR, flow cytometry and western blotting were performed to analyse the expression levels of inflammatory factors (IL-1β, IL-18), lncRNA NEAT1, miR-22-3p, NLRP3 and cleaved caspase-1. Luciferase reporter experiments were performed to verify the association between lncRNA NEAT1 and miR-22-3p. The results indicated that GAS could significantly improve the neurological scores of rats and reduce the area of cerebral infarction. Meanwhile, GAS inhibited pyroptosis by downregulating NLRP3, inflammatory factors (IL-1β, IL-18) and cleaved caspase-1. In addition, GAS attenuated I/R-induced inflammation in neuronal cells through the modulation of the lncRNA NEAT1/miR-22-3p axis. GAS significantly attenuated cerebral I/R injury via modulation of the lncRNA NEAT1/miR-22-3p axis. Thus, GAS might serve as a new agent for the treatment of cerebral I/R injury.

  相似文献   
993.
Yang  Bo  Ao  Yawen  Liu  Ying  Zhang  Xuefen  Li  Ying  Tang  Fengru  Xu  Haibo 《Neurochemical research》2021,46(6):1487-1501
Neurochemical Research - Activation of dopamine (DA) neurons is essential for the transition from sleep to wakefulness and maintenance of awakening, and sufficient to accelerate the emergence from...  相似文献   
994.
Coral Reefs - A correction to this paper has been published: https://doi.org/10.1007/s00338-021-02120-y  相似文献   
995.
Li  Xiongwei  Liu  Pan  Zhou  Jingyi  Su  Mingshen  Ma  Yaping  Jia  Huijuan  Du  Jihong  Gao  Zhongshan  Ye  Zhengwen 《Journal of Plant Growth Regulation》2021,40(3):962-973

Sweetness is one of the key factors determining peach fruit quality. To better understand the molecular basis of gibberellic acid (GA) and 1-naphthaleneacetic acid (NAA) interference with sugar biosynthesis, a middle-late maturing commercial cultivar, ‘Jinxiu’ yellow peach fruit, was treated with three different concentrations of GA4+7 and four of NAA. Fruit weight, firmness, total soluble solids, different sugar contents and the expression level of sugar-related genes were evaluated. The results showed that maximum increase in cv. ‘Jinxiu’ peach fruit size and sucrose content was with 1.25 mM GA4+7, compared to control fruits and the other treatments during the ripening stages. The sucrose-phosphate synthase gene (PpSPS2) which had a high level of expression and positive correlation with sucrose content was significantly regulated by 1.25 mM GA4+7 in the final ripening stages. 0.5 mM NAA treatments significantly reduced the sucrose content and fruit size. Ninety percent of the fruits were deformed or dropped from the trees with treatments of 1 mM NAA and 2 mM NAA in the early development period. The crosstalk of different phytohormones and the related genes will be further investigated to get an insight into the inherent association between hormone control and sugar accumulation.

  相似文献   
996.
997.
Irm  Misbah  Mu  Wei  Xiaoyi  Wu  Geng  Lina  Wang  Xiao  Ye  Bo  Ma  Lei  Zhou  Zhiyu 《Amino acids》2021,53(7):1065-1077

An 8-week feeding trial was conducted to evaluate optimum dietary methionine (Met) requirement of juvenile humpback grouper (Cromileptes altivelis) and the influence of dietary methionine (Met) supplementations on growth, gut micromorphology, protein and lipid metabolism. Seven isoproteic (48.91%) and isolipidic diets (10%) were made to contain 0.70, 0.88, 1.04, 1.27 1.46, 1.61 and 1.76% of dry matter Met levels. Results showed that lower survival, weight gain (WG%), protein efficiency ratio (PER), protein productive value (PPV) but higher daily feed intake (DFI) and feed conversion ratio (FCR) were observed in the Met deficient groups (0.70 and 0.88%). Optimum dietary Met requirement for humpback grouper was found to be 1.07% through the straight-broken line analysis of WG% against Met. Fish fed Met deficient diets (0.70, 0.88%) exhibited lower mRNA levels of growth hormone (GH), growth hormone receptor (GHR), insulin-like growth factor-I (IGF-1), target of rapamycin (TOR) as well as S6 kinase 1 (S6K1) than other dietary groups. Whereas, expression of genes related to general control nonderepressible (GCN2) kinase i.e., GCN2 and C/EBPβ enhancer-binding protein β was upregulated in fish fed low Met diets (P < 0.05). The mRNA expression of hepatic fatty acid synthase (FAS) and sterol regulatory element-binding protein-1 (SREBP-1) were higher in fish fed 0.70 and 0.88% dietary Met group and the lipolytic genes, hepatic peroxisome proliferator-activated receptor α (PPARα) and carnitine palmitoyl transferase-1 (CPT-1) showed an opposite variation tendency as FAS or SREBP1. Generally, the optimum Met requirement for humpback grouper was predicted to be 1.07% of dry matter.

  相似文献   
998.
999.
The International Journal of Life Cycle Assessment - The current global interest in circular economy (CE) opens an opportunity to make society’s consumption and production patterns more...  相似文献   
1000.
ObjectivesStromal cell‐derived factor‐1 (SDF‐1) actively directs endogenous cell homing. Exendin‐4 (EX‐4) promotes stem cell osteogenic differentiation. Studies revealed that EX‐4 strengthened SDF‐1‐mediated stem cell migration. However, the effects of SDF‐1 and EX‐4 on periodontal ligament stem cells (PDLSCs) and bone regeneration have not been investigated. In this study, we aimed to evaluate the effects of SDF‐1/EX‐4 cotherapy on PDLSCs in vitro and periodontal bone regeneration in vivo.MethodsCell‐counting kit‐8 (CCK8), transwell assay, qRT‐PCR and western blot were used to determine the effects and mechanism of SDF‐1/EX‐4 cotherapy on PDLSCs in vitro. A rat periodontal bone defect model was developed to evaluate the effects of topical application of SDF‐1 and systemic injection of EX‐4 on endogenous cell recruitment, osteoclastogenesis and bone regeneration in vivo.ResultsSDF‐1/EX‐4 cotherapy had additive effects on PDLSC proliferation, migration, alkaline phosphatase (ALP) activity, mineral deposition and osteogenesis‐related gene expression compared to SDF‐1 or EX‐4 in vitro. Pretreatment with ERK inhibitor U0126 blocked SDF‐1/EX‐4 cotherapy induced ERK signal activation and PDLSC proliferation. SDF‐1/EX‐4 cotherapy significantly promoted new bone formation, recruited more CXCR4+ cells and CD90+/CD34 stromal cells to the defects, enhanced early‐stage osteoclastogenesis and osteogenesis‐related markers expression in regenerated bone compared to control, SDF‐1 or EX‐4 in vivo.ConclusionsSDF‐1/EX‐4 cotherapy synergistically regulated PDLSC activities, promoted periodontal bone formation, thereby providing a new strategy for periodontal bone regeneration.  相似文献   
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