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   29196篇
  免费   2982篇
  国内免费   2692篇
耳鼻咽喉   106篇
儿科学   247篇
妇产科学   261篇
基础医学   3787篇
口腔科学   490篇
临床医学   1704篇
内科学   3084篇
皮肤病学   382篇
神经病学   1902篇
特种医学   574篇
外国民族医学   47篇
外科学   1747篇
综合类   7329篇
现状与发展   5篇
预防医学   775篇
眼科学   755篇
药学   4507篇
中国医学   2422篇
肿瘤学   4746篇
  2024年   76篇
  2023年   344篇
  2022年   578篇
  2021年   982篇
  2020年   857篇
  2019年   773篇
  2018年   709篇
  2017年   992篇
  2016年   1064篇
  2015年   1354篇
  2014年   1565篇
  2013年   2106篇
  2012年   1888篇
  2011年   2133篇
  2010年   1861篇
  2009年   1740篇
  2008年   1917篇
  2007年   2002篇
  2006年   1893篇
  2005年   1825篇
  2004年   1648篇
  2003年   1492篇
  2002年   1219篇
  2001年   1191篇
  2000年   905篇
  1999年   580篇
  1998年   469篇
  1997年   307篇
  1996年   179篇
  1995年   107篇
  1994年   47篇
  1993年   12篇
  1992年   15篇
  1991年   11篇
  1990年   3篇
  1989年   10篇
  1988年   1篇
  1987年   6篇
  1985年   3篇
  1984年   2篇
  1983年   2篇
  1981年   1篇
  1966年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
BACKGROUND Aloe vera exerts several biological activities, such as, anti-inflammatory, antioxidant, and antimicrobial effects. It was recently shown to reduce insulin resistance and triglyceride level. We hypothesized that aloe vera would have beneficial effects in alleviating non-alcoholic steatohepatitis(NASH) in rats.AIM To examine the therapeutic effects of aloe vera in NASH rats.METHODS All rats were randomly divided into 3 groups(n = 6 in each group). Rats in the control group were fed ad libitum with a standard diet for 8 wk. Rats in the NASH group were fed ad libitum with a high-fat high-fructose diet(HFHFD) for 8 wk. Rats in the aloe vera group were fed ad libitum with a HFHFD and aloe vera in dimethylsulfoxide(50 mg/kg) by gavage daily for 8 wk. Liver samples were collected at the end of the treatment period.RESULTS Hepatic malondialdehyde(MDA) levels increased significantly in the NASH group as compared with the control group(377 ± 77 nmol/mg vs 129 ± 51 nmol/mg protein, respectively, P 0.001). Glutathione(GSH) levels were significantly lower in the NASH group than the control group(9 ± 2 nmol/mg vs 24 ± 8 nmol/mg protein, respectively, P = 0.001). The expression of interleukin-18(IL-18), nuclear factor-kappa β, and caspase-3 increased, while peroxisome proliferator-activated receptor gamma decreased in the NASH group compared with the controls. Following aloe vera administration, MDA levels decreased(199 ± 35 nmol/mg protein) and GSH increased(18 ± 4 nmol/mg protein) markedly. Steatosis, hepatocyte ballooning, lobular inflammation and increased hepatocyte apoptosis were observed in the NASH group. Aloe vera treatment attenuated these changes in liver histology.CONCLUSION Aloe vera attenuated oxidative stress, hepatic inflammation and hepatocyte apoptosis, thus improving liver pathology in rats with NASH.  相似文献   
12.
目的 探讨MicroRNA-21(miR-21)对视网膜母细胞瘤(RB)细胞增殖的影响及作用机制。方法 采用Real-time PCR技术检测miR-21在正常视网膜组织和确诊RB组织中的表达情况;然后在转染的基础上运用MTT检查RB细胞存活率、流式细胞仪检测细胞凋亡率。Western blot法检测与细胞凋亡相关蛋白PDCD4、Bax、Bcl-2的表达。结果 与正常视网膜组织miR-21表达 (0.703±0.071)相比,RB组织miR-21为高表达(2.214±0.162),差异有统计学意义(P<0.01)。在Weri-Rb-1细胞中,与NC组(2.245±0.213)相比,miR-21抑制剂转染后明显降低了miR-21的表达水平,miR-21 inhibitor组为0.683±0.075,差异有统计学意义 (P<0.01)。两组细胞转染后24 h、48 h、72 h、96 h,MTT测定法检测细胞活力结果显示:两组24 h的A值比较,差异无统计学意义 (P>0.05),miR-21 inhibitor 组在 48 h、72 h、 96 h的A值均低于 NC 组,差异均有统计学意义 (均为P<0.01)。流式细胞术检测结果显示:NC组凋亡细胞在总细胞中百分比为(3.045±0.301)%和(4.832±0.493)%,miR-21 inhibitor组凋亡细胞在总细胞中百分比为(2.593±0.257)%和(40.167±4.014)%,miR-21 inhibitor组Weri-Rb-1细胞的凋亡率明显高于miR-21 NC组(P<0.01)。Western blot检测结果显示:NC组PDCD4表达(0.192±0.045)相比miR-21 inhibitor组(0.683±0.091)表达明显减少,NC组Bax的蛋白表达水平(0.143±0.036)相比miR-21 inhibitor组(1.192±0.054)也明显减少,差异均有统计学意义(P<0.01),NC组Bcl-2蛋白表达(0.864±0.038)相比miR-21 inhibitor组(0.257±0.026)明显增多,差异有统计学意义(P<0.05)。结论 miR-21是RB的促癌基因,miR-21抑制剂可以通过降低miR-21表达抑制肿瘤细胞的增殖、促进细胞凋亡,这一过程与PDCD4、Bax、Bcl-2等凋亡相关蛋白有关。  相似文献   
13.
14.
Acute lung injury (ALI) is a major cause of sepsis-induced acute respiratory failure. Emodin has been considered to play a protective role for acute lung edema in cecal ligation and puncture (CLP)-induced sepsis model. In this study we aimed to investigate whether emodin could improve CLP-induced lung sepsis via regulating aquaporin (AQP) and tight junction (TJ), inflammatory factors, and pulmonary apoptosis. The results showed that sepsis-induced pulmonary pathological changes were significantly improved after emodin treatment. Emodin was found to upregulate AQP and TJ expression in the CLP model. Meanwhile, inflammatory cytokine release and pulmonary apoptosis was remarkably reduced after emodin treatment in lung sepsis. Our data demonstrated that emodin could suppresse inflammation, restore pulmonary epithelial barrier and reduce mortality in CLP-induced ALI, suggesting the potential therapeutic application of emodin in sepsis.  相似文献   
15.
目的探讨不同时期婴幼儿口腔颌面部血管瘤TRAIL受体DR4、DR5 m RNA的表达及意义。方法本研究于2013年3—10月在中国医科大学中心实验室完成。收集婴幼儿口腔颌面部血管瘤组织标本40例(增殖期血管瘤26例、退化期血管瘤14例),以及正常皮肤组织标本12例,应用RT-PCR检测TRAIL的2个受体DR4和DR5m RNA在其中的分布情况。结果增殖期血管瘤组织中DR4和DR5 m RNA的表达强度显著低于退化期血管瘤和正常皮肤组织,差异有统计学意义(P<0.01)。退化期血管瘤和正常皮肤组织中DR4、DR5 m RNA的表达强度较高,但二者之间差异无统计学意义。结论退化期血管瘤组织DR4和DR5 m RNA表达程度高,与增殖期血管瘤相比,退化期血管瘤可以更多的结合TRAIL,细胞凋亡增多,引发血管瘤消退。  相似文献   
16.
Fas/FasL在各阶段婴幼儿血管瘤中的表达及意义   总被引:15,自引:0,他引:15  
目的 检测Fas/FasL在各阶段婴幼儿血管瘤组织中的表达,探讨Fas/FasL在婴幼儿血管瘤细胞凋亡中的作用。方法 应用EnVision法免疫组化染色和RT-PCR检测Fas/FasL蛋白及mRNA在各阶段血管瘤组织中的表达。结果 ①增生早期和增生中期,部分血管瘤细胞表达Fas;增生晚期,阳性细胞明显增多,Fas mRNA表达最强;消退早期,仍有少量微血管内皮细胞表达Fas,之后Fas表达迅速减弱。②最早期细胞团中没有FasL(+)细胞;增生中期,血管瘤组织中出现少量FasL(+)细胞;增生晚期FasL(+)细胞显著增多,FasL mRNA表达最强;消退早期之后,FasL(+)细胞迅速减少以至消失。结论 Fas/FasL与婴幼儿血管瘤演变过程有密切联系,Fas/FasL介导的血管瘤细胞凋亡可能是婴幼儿血管瘤自行消退的重要原因。  相似文献   
17.
BACKGROUND: Common clinical forms of oral lichen planus (OLP) and oral lichenoid reactions (OLR) are erythematous (ERY) or reticular (RET). The purpose of this study was to find histopathological changes that differ between these forms. METHODS: Epithelial thickness, epithelial proliferation rate, apoptosis, and HLA-DR expression were compared among 10 reticular and 12 erythematous lesions, and 11 normal oral mucosa samples (NOM). RESULTS: The epithelium in ERY was thinner than in NOM, whereas RET showed values between ERY and NOM. Cell proliferation increased significantly in ERY as compared with RET and NOM, with no difference between RET and NOM. Relative numbers of epithelial cell nuclei displaying visible chromatin condensation were reduced in ERY form. CONCLUSIONS: The markedly increased cell proliferation in ERY supports the notion that this form displays a higher disease activity as compared to RET. It can therefore be important to study each disease form separately.  相似文献   
18.
目的探讨Survivin在食管癌组织中的表达及其与bcl-2蛋白表达的相关性。方法应用免疫组织化学SP法,检测Survivin、bcl-2蛋白在68例食管癌组织和20例正常食管组织中的表达。结果Survivin蛋白在正常食管组织中低表达或不表达,68例食管癌组织中,49例表达阳性,占72.1%。Survivin蛋白表达与分化程度、淋巴结转移密切相关(P<0.05)。食管癌组织bcl-2蛋白表达阳性、阴性组中,Survivin蛋白阳性表达率分别为94.7%(36/38)和43.3%(13/30),两者比较,差异有统计学意义(P<0.05)。Survivin蛋白表达与bcl-2蛋白表达密切相关。结论Survivin在食管癌组织中表达上调,通过抑制细胞凋亡,在食管癌的发生中起到重要作用;凋亡相关基因bcl-2的上调与Survivin的表达可能在食管癌变中起协同作用。  相似文献   
19.
20.
The B cell functional response following ligation of surface(s) lgM is dependent upon the differentiation stage of the populationstudied: cross-linking slgM promotes proliferation of restingtonsillar follicular mantle (FM) B lymphocytes but induces apoptosisin the susceptible Epstein- Barr virus genome-negative Burkittlymphoma (BL) cell line Ramos (Ramos-BL). This study investigateswhether phosphatidylinositol-3-kinase (Pl3-kinase), which hasbeen reported to be intimately involved in the regulation ofcellular growth, plays a role in the regulation of these sig-promoted B cell responses, and uses the selective and irreversibleinhibitor of Pl3-kinase activity, wortmannin (Wm). In Ramos-BLB cells, at 8 h post-treatment, Wm triggers a transient increasein apoptosis of 16 ± 6.9% with a concomitant cellularloss of 16 ± 6.1% from the G1 phase of cell cycle; [3H]thymidineincorporation also decreases by 33 ± 5.0%, from 37,274c.p.m. ± 10% to 25,127 c.p.m. ± 4.0%. Moreover,at 72 h culture, Wm inhibits anti-lgM-induced FM B lymphocytelevels of [3H]thymidine incorporation typically by 47% and triggers80% apoptosis from the G0G1 phase of cell cycle. Ramos-BL Bcells exhibit high basal levels of Pl3-kinase activity, as determinedby immunoprecipitation with antibody to the p85 regulatory subunitof Pl3-kinase and 32P incorporation into phosphatidylinositol,which is not significantly affected by anti-lgM stimulation;by contrast, anti-lgM stimulates significant Pl3-kinase activityover negligible basal levels in FM B lymphocytes. Pre-treatmentwith Wm inhibits Pl3-kinase activity in both cell types. Takentogether these data indicate that in Ramos-BL B cells slgM-triggeredgrowth arrest and apoptosis is Pl3- kinase independent, whereasPl3-kinase activity is critical for slgM-triggered mitogenesisof FM B lymphocytes. Thus Pl3-kinase plays a pivotal role inthe regulation of both normal and neoplastic B lymphocyte progressionthrough the cell cycle, such that if this Pl3-kinase-dependentpathway is inhibited these cells default to apoptosis.  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