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   3755篇
  免费   231篇
  国内免费   372篇
  2024年   11篇
  2023年   69篇
  2022年   111篇
  2021年   234篇
  2020年   151篇
  2019年   168篇
  2018年   155篇
  2017年   103篇
  2016年   157篇
  2015年   223篇
  2014年   296篇
  2013年   315篇
  2012年   369篇
  2011年   320篇
  2010年   174篇
  2009年   148篇
  2008年   181篇
  2007年   192篇
  2006年   169篇
  2005年   148篇
  2004年   106篇
  2003年   101篇
  2002年   93篇
  2001年   32篇
  2000年   36篇
  1999年   47篇
  1998年   30篇
  1997年   20篇
  1996年   27篇
  1995年   26篇
  1994年   16篇
  1993年   16篇
  1992年   21篇
  1991年   21篇
  1990年   12篇
  1989年   12篇
  1988年   8篇
  1987年   7篇
  1986年   8篇
  1985年   3篇
  1984年   3篇
  1983年   2篇
  1982年   3篇
  1981年   4篇
  1980年   3篇
  1979年   2篇
  1974年   2篇
  1971年   1篇
  1966年   2篇
排序方式: 共有4358条查询结果,搜索用时 109 毫秒
181.
Cervical cancer is the fourth most common malignancy in women worldwide and cervical squamous cell carcinoma (CESC) is the most common histological type of cervical cancer. The dysregulation of genes plays a significant role in cancer. In the present study, we screened out differentially expressed genes (DEGs) of CESC in the GSE63514 data set from the Gene Expression Omnibus database. An integrated bioinformatics analysis was used to select hub genes, as well as to investigate their related prognostic signature, functional annotation, methylation mechanism, and candidate molecular drugs. As a result, a total of 1907 DEGs were identified (944 were upregulated and 963 were downregulated). In the protein–protein interaction network, three hub modules and 30 hub genes were identified. And two hub modules and 116 hub genes were screened out from four CESC-related modules by the weighted gene coexpression network analysis. The gene ontology term enrichment analysis and Kyoto encyclopedia of genes and genomes pathway analysis were performed to better understand functions and pathways. Genes with a significant prognostic value were found by prognostic signature analysis. And there were five genes (EPHX2, CHAF1B, KIAA1524, CDC45, and RMI2) identified as significant CESC-associated genes after expression validation and survival analysis. Among them, EPHX2 and RMI2 were noted as two novel key genes for the CESC-associated methylation and expression. In addition, four candidate small molecule drugs for CESC (camptothecin, resveratrol, vorinostat, and trichostatin A) were defined. Further studies are required to explore these significant CESC-associated genes for their potentiality in diagnosis, prognosis, and targeted therapy.  相似文献   
182.
Atherosclerosis (AS), a progressive disorder, is one of the tough challenges in the clinic. Scutellarin, an extract from Herba Erigerontis, is found to have oxygen-free radicals scavenging effects and antioxidant effects. In this study, we aimed to investigate the anti-AS effects of scutellarin is related to controlling the Hippo–FOXO3A and PI3K/AKT signal pathway. To establish an AS model, the rats in the scutellarin and model groups were intraperitoneally injected with vitamin D 3 and then fed a high-fat diet for 12 weeks. In addition, in vitro angiotensin II-induced apoptosis of human aortic endothelial cells (HAECs) were used to establish models. Scutellarin significantly reduced blood lipid levels and increased antioxidase levels in both models. Additionally, scutellarin inhibited reactive oxygen species generation and apoptosis in HAECs. The impaired vascular barrier function was restored by using scutellarin in AS rats and in HAECs cells characterized by inhibiting mammalian sterile-20-like kinases 1 (Mst1) phosphorylation, Yes-associated protein (YAP) phosphorylation, forkhead box O3A (FOXO3A) phosphorylation at serine 207, nuclear translocation of FOXO3A, and upregulating protein expression of AKT and FOXO3A phosphorylation at serine 253. Scutellarin significantly reduced Bcl-2 interacting mediator of cell death (Bim), caspase-3, APO-1, CD95 (Fas), and Bax: Bcl-2-associated X (Bax) levels and activated Bcl-2: B-cell lymphoma-2 (Bcl-2). Scutellarin also significantly inhibited the expression of Mst1, YAP, FOXO3A at the messenger RNA level. When Mst1 was overexpressed or phosphoinositide 3-kinases suppressed, the effects of scutellarin were significantly blocked. In conclusion, the results of the present study suggest that scutellarin exerts protective effects against AS by inhibiting endothelial cell injury and apoptosis by regulating the Hippo–FOXO3A and PI3K/AKT signal pathways.  相似文献   
183.
【目的】探讨凡纳滨对虾养殖水体中入侵蓝藻拟柱孢藻的生长生理特性。【方法】从汕头澄海人工对虾养殖池分离纯化藻株,通过形态及其16SrRNA基因鉴定,之后在CT与BG11两种蓝藻通用培养基的基础上优化最佳培养条件,最后分析了不同浓度的3种重金属离子即Cu~(2+)(0–0.8 mg/L)、Cd~(2+)(0–4 mg/L)和Pb~(2+)(0–80 mg/L)对藻株生长的影响。【结果】澄海虾池来源的分离纯化藻株形态呈卷曲螺旋型,16S rRNA基因序列与多株其他来源的拟柱孢藻相似度均达98%以上。实验室培养,藻株最佳生长状态的培养条件是在BG11培养基的基础上调整氮浓度及氮磷比分别为N 62 mg/L,N︰P=9︰1,在此条件下,藻丝生物量可达(0.632±0.170)×107/L,藻丝比平均生长速率最高为(0.063±0.001)/d。本分离藻株活体对重金属Cu~(2+)、Cd~(2+)和Pb~(2+)具有一定的耐受性,其耐受浓度范围分别为0–0.2、0–0.5和1–40 mg/L,其中,Cu~(2+)和Cd~(2+)对藻的生长具有抑制作用,而且此抑制作用随着金属离子剂量的增加及作用时间的延长更加显著,Cu~(2+)和Cd~(2+)对藻体的半数抑制浓度(96 h EC50)分别为0.125和0.551 mg/L;而浓度范围为0–80 mg/L的Pb~(2+)对藻体的生长则表现为低剂量(≤40 mg/L)呈促进,高剂量(≥80 mg/L)则抑制。【结论】从凡纳滨对虾养殖池中分离鉴定出一株形态呈螺旋型的拟柱孢藻,命名为螺旋拟柱孢藻(Cylindrospermopsis raciborskii helix),本藻株活体能够在一定浓度的Cu~(2+)、Cd~(2+)和Pb~(2+)中生长,为螺旋拟柱孢藻活藻生物吸附重金属离子而改善虾池水体环境提供了可能性。  相似文献   
184.
Pravastatin sodium on triggering receptor expressed on myeloid cell-1 (TREM-1)-mediated inflammation in human peripheral blood mononuclear cells (PBMCs) has been poorly investigated. In this study, we isolated PBMCs from the peripheral blood samples of patients with chronic obstructive pulmonary disease, treated the cells with pravastatin sodium, and determined a concentration at which more than 90% cells could survive. Then we treated cells with 10?ng/ml of lipopolysaccharide, added with 10, 50, 100?μM of pravastatin sodium combined with or without LR-12, a known TREM-1 inhibitor. The expression of TREM-1 was determined by quantitative RT-PCR. The levels of TREM-1, IL-6, and TNF-α in cell culture supernatant were measured with ELISA. Simultaneously, NF-κB signaling pathway-related protein p-p65 and p-IκBα were detected by Western blot assay. Results demonstrated that pravastatin sodium significantly mitigated lipopolysaccharide-stimulated TREM-1 over-expression at mRNA and protein levels dose-dependently. Elevated IL-6 and TNF-α levels changed synchronously. LR-12 inhibited the TREM-1 over-expression and inflammatory factor production but did not show extra synergistic effect to pravastatin. Lipopolysaccharide induced phospho-p65 and -IκBα over-expression was weakened significantly when cells were treated with pravastatin sodium. In conclusion, pravastatin could inhibit TREM-1-medieted inflammation and NF-κB signaling pathway was involved.  相似文献   
185.
Local transplantation of stem cells has therapeutic effects on skin damage but cannot provide satisfactory wound healing. Studies on the mechanisms underlying the therapeutic effects of stem cells on skin wound healing will be needed. Hence, in the present study, we explored the role of Caveolin-1 in epidermal stem cells (EpiSCs) in the modulation of wound healing. We first isolated EpiSCs from mouse skin tissues and established stable EpiSCs with overexpression of Caveolin-1 using a lentiviral construct. We then evaluated the epidermal growth factor (EGF)-induced cell proliferation ability using cell counting Kit-8 (CCK-8) assay and assessed EpiSC pluripotency by examining Nanog mRNA levels in EpiSCs. Furthermore, we treated mice with skin burn injury using EpiSCs with overexpression of Caveolin-1. Histological examinations were conducted to evaluate re-epithelialization, wound scores, cell proliferation and capillary density in wounds. We found that overexpression of Caveolin-1 in EpiSCs promoted EGF-induced cell proliferation ability and increased wound closure in a mouse model of skin burn injury. Histological evaluation demonstrated that overexpression of Caveolin-1 in EpiSCs promoted re-epithelialization in wounds, enhanced cellularity, and increased vasculature, as well as increased wound scores. Taken together, our results suggested that Caveolin-1 expression in the EpiSCs play a critical role in the regulation of EpiSC proliferation ability and alteration of EpiSC proliferation ability may be an effective approach in promoting EpiSC-based therapy in skin wound healing.  相似文献   
186.
187.
Angiogenesis is an important process in atherosclerosis. ErbB2 was proved to have an important role in vascular development, but it is still unclear whether Erbin expresses in vessels as well as its location and function in the vessels. In the current study, we investigated the location and function of Erbin in human umbilical veins. The human umbilical veins were prepared, and immunofluorescent analysis was performed to determine the expression of Erbin. Human umbilical vein endothelial cells (HUVECs) were cultured and the lentivirus (LV) containing Erbin RNAi was also prepared. After transfection with the lentivirus, CCK-8 assay and Annexin V-PI assay were used for cell proliferation and apoptosis, respectively. Cell migration was studied using the scratch wound healing assay and the transwell assay. The capillary-like tube formation assay was performed to illustrate the effect of Erbin on HUVEC tube formation. Expression of signaling pathway molecules was assessed with Western blot. The immunofluorescent analysis suggested that Erbin expressed in human umbilical veins and the majority of the Erbin is strongly colocalized in endothelial cells. Although knockdown of Erbin did not affect HUVEC proliferation and apoptosis, it significantly suppressed HUVEC migration and tubular structure formation. Erbin knockdown showed no effect on the ERK1/2 and Smad2/3 signaling pathways but significantly promoted Smad1/5 phosphorylation and nuclear translocation. Ablation of the Smad1/5 pathway decreased the effects of Erbin on endothelial cells. Erbin is mainly localized in endothelial cells in human umbilical veins and plays a critical role in endothelial cell migration and tubular formation via the Smad1/5 pathway.  相似文献   
188.
FAM83H-AS1, also known as oncogenic long noncoding RNA (lncRNA)-3, is a novel lncRNA that has been suggested to be dysregulated in a variety of human cancers. However, the expression status and function of FAM83H-AS1 in bladder cancer are still unknown. The object of our study is to explore the clinical value of FAM83H-AS1 in patients with bladder cancer and the biological function of FAM83H-AS1 in bladder cancer cells. In our results, the expression of FAM83H-AS1 was obviously elevated in bladder cancer tissue samples and bladder cancer cell lines compared with adjacent normal tissue samples and normal bladder epithelial cell lines, respectively. In addition, high expression of FAM83H-AS1 was associated with advanced clinical stage and the presence of muscularis invasion and served as an independent poor prognostic factor for overall survival in patients with bladder cancer. The loss-of-function study showed that silencing FAM83H-AS1 expression suppressed cell proliferation, migration, and invasion and induced cycle arrest at G0/G1 phase. In conclusion, FAM83H-AS1 is involved in the progression of bladder cancer and serves as a prognostic biomarker and potential therapeutic target for patients with bladder cancer.  相似文献   
189.
This study investigated the molecular mechanism by which sodium butyrate (NaB) causes oxidative stress damage induced by lipopolysaccharide (LPS) on cow mammary epithelial cells (MAC-T). We found that NaB significantly increased the activities of antioxidant enzymes, including superoxide dismutase, glutathione peroxidase, catalase, peroxidase, and total antioxidant capacity and decreased the reactive oxygen species production in LPS-induced MAC-T cells. NaB attenuated protein damage and reduced apoptosis in LPS-induced MAC-T cells. The messenger RNA (mRNA) levels of caspase-3, caspase-9, and Bax decreased, while the Bcl-2 mRNA level increased in LPS-induced MAC-T cells treated with NaB. Our results showed that NaB treatment increased the phosphoinositide 3-kinase (PI3K) and phospho-AKT (P-AKT) protein levels, whereas it decreased the Bax, caspase-3, and caspase-9 protein levels in LPS-induced MAC-T cells. However, the increase in PI3K and P-AKT protein levels and the decrease in Bax, caspase-3, and caspase-9 protein levels induced by NaB treatment were reversed when the cells were pretreated with LY294002 (PI3K inhibitor). These results indicate that NaB ameliorates LPS-induced oxidative damage by increasing antioxidative enzyme activities and ameliorating protein damage in MAC-T cells. In addition, NaB decreased apoptosis by inhibiting caspase-3, caspase-9, and Bax protein levels, and this action was mainly achieved via activation of the PI3K/AKT signaling pathways in LPS-induced MAC-T cells. These results provide substantial information for NaB as a chemical supplement to treat oxidative stress and its related diseases in ruminants.  相似文献   
190.
Diabetic cognitive impairment (DCI) is a common diabetic complication with hallmarks of loss of learning ability and disorders of memory and behavior. Glucocorticoid receptor (GR) dysfunction is a main reason for neuronal impairment in brain of diabetic patients. Here, we determined that ipriflavone (IP) a clinical anti‐osteoporosis drug functioned as a non‐steroidal GR antagonist and efficiently ameliorated learning and memory dysfunction in both type 1 and 2 diabetic mice. The underlying mechanism has been intensively investigated by assay against the diabetic mice with GR‐specific knockdown in the brain by injection of adeno‐associated virus (AAV)‐ePHP‐siGR. IP suppressed tau hyperphosphorylation through GR/PI3K/AKT/GSK3β pathway, alleviated neuronal inflammation through GR/NF‐κB/NLRP3/ASC/Caspase‐1 pathway, and protected against synaptic impairment through GR/CREB/BDNF pathway. To our knowledge, our work might be the first to expound the detailed mechanism underlying the amelioration of non‐steroidal GR antagonist on DCI‐like pathology in mice and report the potential of IP in treatment of DCI.  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