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   46123篇
  免费   3836篇
  国内免费   1342篇
耳鼻咽喉   185篇
儿科学   882篇
妇产科学   991篇
基础医学   4536篇
口腔科学   898篇
临床医学   5490篇
内科学   9758篇
皮肤病学   312篇
神经病学   787篇
特种医学   596篇
外国民族医学   11篇
外科学   1930篇
综合类   7112篇
现状与发展   9篇
预防医学   5845篇
眼科学   164篇
药学   6104篇
  12篇
中国医学   1490篇
肿瘤学   4189篇
  2024年   36篇
  2023年   584篇
  2022年   972篇
  2021年   1872篇
  2020年   1573篇
  2019年   1522篇
  2018年   1553篇
  2017年   1505篇
  2016年   1828篇
  2015年   2017篇
  2014年   3179篇
  2013年   3850篇
  2012年   3369篇
  2011年   3534篇
  2010年   2713篇
  2009年   2481篇
  2008年   2623篇
  2007年   2567篇
  2006年   2195篇
  2005年   1885篇
  2004年   1568篇
  2003年   1194篇
  2002年   956篇
  2001年   867篇
  2000年   682篇
  1999年   583篇
  1998年   445篇
  1997年   427篇
  1996年   349篇
  1995年   301篇
  1994年   288篇
  1993年   219篇
  1992年   213篇
  1991年   181篇
  1990年   130篇
  1989年   127篇
  1988年   88篇
  1987年   104篇
  1986年   65篇
  1985年   114篇
  1984年   75篇
  1983年   45篇
  1982年   73篇
  1981年   57篇
  1980年   52篇
  1979年   40篇
  1978年   27篇
  1977年   37篇
  1976年   36篇
  1975年   26篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
The aim of this systematic review and meta‐analysis was to analyze the effects of grape seed extract (GSE) on glycemic control and serum lipoproteins, inflammation and body weight. Two independent authors systematically searched online databases including EMBASE, Scopus, PubMed, Cochrane Library, and Web of Science from inception until May 30, 2019. Cochrane Collaboration risk of bias tool was applied to assess the methodological quality of included trials. The heterogeneity among the included studies was assessed using Cochrane's Q test and I‐square (I2) statistic. Data were pooled using a random‐effects model and weighted mean difference (WMD) was considered as the overall effect size. Fifty trials were included in this meta‐analysis. Pooling effect sizes from studies demonstrated a significant decrease in fasting plasma glucose (FPG) (WMD): ?2.01; 95% confidence interval (CI): ?3.14, ?0.86), total cholesterol (TC; WMD: ?6.03; 95% CI: ?9.71, ?2.35), low‐density lipoprotein (LDL) cholesterol (WMD: ?4.97; 95% CI: ?8.37, ?1.57), triglycerides (WMD: ?6.55; 95% CI: ?9.28, ?3.83), and C‐reactive protein (CRP) concentrations (WMD: ?0.81; 95% CI: ?1.25, ?0.38) following GSE therapy. Grape seed did not influence HbA1c, HDL cholesterol levels, and anthropometric measurements. This meta‐analysis demonstrated that GSE intake significantly reduced FPG, TC, LDL cholesterol, triglycerides, and CRP levels.  相似文献   
22.
Malignant melanoma is a highly aggressive skin cancer characterized by an elevated grade of tumor cell plasticity. Such plasticity allows adaptation of melanoma cells to different hostile conditions and guarantees tumor survival and disease progression, including aggressive features such as drug resistance. Indeed, almost 50% of melanoma rapidly develop resistance to the BRAFV600E inhibitor vemurafenib, with fast tumor dissemination, a devastating consequence for patients’ outcomes. Vasculogenic mimicry (VM), the ability of cancer cells to organize themselves in perfused vascular-like channels, might sustain tumor spread by providing vemurafenibresistant cancer cells with supplementary ways to enter into circulation and disseminate. Thus, this research aims to determine if vemurafenib resistance goes with the acquisition of VM ability by aggressive melanoma cells, and identify a driving molecule for both vemurafenib resistance and VM. We used two independent experimental models of drug-resistant melanoma cells, the first one represented by a chronic adaptation of melanoma cells to extracellular acidosis, known to drive a particularly aggressive and vemurafenib-resistant phenotype, the second one generated with chronic vemurafenib exposure. By performing in vitro tube formation assay and evaluating the expression levels of the VM markers EphA2 and VE-cadherin by Western blotting and flow cytometer analyses, we demonstrated that vemurafenib-resistant cells obtained by both models are characterized by an increased ability to perform VM. Moreover, by exploiting the CRISPR-Cas9 technique and using the urokinase plasminogen activator receptor (uPAR) inhibitor M25, we identified uPAR as a driver of VM expressed by vemurafenib-resistant melanoma cells. Thus, uPAR targeting may be successfully leveraged as a new complementary therapy to inhibit VM in drug-resistant melanoma patients, to counteract the rapid progression and dissemination of the disease.  相似文献   
23.
《药学学报(英文版)》2020,10(2):327-343
Our recent studies demonstrated that the natural product nobiletin (NOB) served as a promising multidrug resistance (MDR) reversal agent and improved the effectiveness of cancer chemotherapy in vitro. However, low aqueous solubility and difficulty in total synthesis limited its application as a therapeutic agent. To tackle these challenges, NOB was synthesized in a high yield by a concise route of six steps and fourteen derivatives were synthesized with remarkable solubility and efficacy. All the compounds showed improved sensitivity to paclitaxel (PTX) in P-glycoprotein (P-gp) overexpressing MDR cancer cells. Among them, compound 29d exhibited water solubility 280-fold higher than NOB. A drug-resistance A549/T xenograft model showed that 29d, at a dose of 50 mg/kg co-administered with PTX (15 mg/kg), inhibited tumor growth more effective than NOB and remarkably increased PTX concentration in the tumors via P-gp inhibition. Moreover, Western blot experiments revealed that 29d inhibited expression of NRF2, phosphorylated ERK and AKT in MDR cancer cells, thus implying 29d of multiple mechanisms to reverse MDR in lung cancer.  相似文献   
24.
社区获得性肺炎(Community Acquired Pneumonia,CAP)是比较常见的院外肺部炎性疾病之一,随着细菌、支原体、衣原体等多种病原体的耐药率的上升,以及病患梯度的范围增加,CAP的发病率呈逐年上升的趋势,死亡率日益增高,导致医疗资源消耗巨大。目前临床上CAP的患者主要依靠经验性治疗。正确选择抗生素、减少病原体的耐药率,优化肺部炎症疾病的医疗方案,提高CAP临床治愈率已经成为临床医生当前面临的一项重大挑战。中药制剂具有广谱抗菌、调节免疫、不易耐药、简便价廉等特点,是解决上述难题的一个很好途径。  相似文献   
25.
目的以肠道微生态为切入点探讨补肾化浊方联合粪菌移植治疗多囊卵巢综合征(PCOS)潜在机制。方法将30只6周龄SD大鼠随机分为空白组、模型组、中药组、粪菌移植组、中药+粪菌移植组,每组6只。来曲唑1 mg/(kg d)灌胃51 d,第22日起,中药组加灌补肾化浊方21.7 g/(kg d),粪菌移植组加灌新鲜粪便2 g/(kg d),中药+粪菌移植组加灌补肾化浊方21.7 g/(kg d)和新鲜粪便2 g/(kg d),连续30 d,另设空白组。干预结束后,腹主动脉取血检测大鼠血清性激素、空腹胰岛素(FINS)、空腹血糖(FPG),ELISA检测大鼠血清白细胞介素(IL)-18、肿瘤坏死因子-α(TNF-α)水平,HE染色观察大鼠卵巢形态学变化。结果与空白组比较,模型组大鼠卵巢呈多囊样改变,体质量、睾酮、黄体生成素(LH)/促卵泡激素(FSH)、FPG、HOMA-IR、IL-18、TNF-α水平均明显升高(P<0.01,P<0.001);与模型组比较,中药+粪菌移植组可显著改善上述指标(P<0.05,P<0.01,P<0.001),中药组可显著改善除TNF-α外各项指标(P<0.05,P<0.01),粪菌移植组可显著降低PCOS大鼠LH/FSH、IL-18水平(P<0.01,P<0.001);在降低IL-18水平方面,中药+粪菌移植组作用显著优于中药组(P<0.01)。结论中药联合粪菌移植可显著改善PCOS大鼠生殖和代谢功能,改善慢性炎症状态。  相似文献   
26.
27.
Multidrug resistance due to facilitated drug efflux mediated by ATP-binding cassette (ABC) transporters is a main cause for failure of cancer therapy. Genetic polymorphisms in ABC genes affect the disposition of chemotherapeutics and constitute important biomarkers for therapeutic response and toxicity. Here we correlated germline variability in ABC transporters with disease-specific survival (DSS) in 960 breast cancer (BRCA), 314 clear cell renal cell carcinoma and 325 hepatocellular carcinoma patients. We find that variant burden in ABCC1 is a strong predictor of DSS in BRCA patients, whereas candidate polymorphisms are not associated with DSS. This association is highly drug-specific for subgroups treated with the MRP1 substrates cyclophosphamide (log-rank p = 0.0011) and doxorubicin (log-rank p = 0.0088) independent of age and tumor stage, whereas no association was found in individuals treated with tamoxifen (log-rank p = 0.13). Structural mapping of significant variants revealed multiple variants at residues involved in protein stability, cofactor stabilization or substrate binding. Our results demonstrate that BRCA patients with high variant burden in ABCC1 are less prone to respond appropriately to pharmacological therapy with MRP1 substrates, thus incentivizing the consideration of genomic germline data for precision cancer medicine.  相似文献   
28.
29.
目的:观察PERK蛋白对结肠癌细胞药物敏感性的影响,并进一步探讨其相关作用机制。方法:结肠癌细胞系HCT116分为三组:空白对照(Control)组、下调PERK表达(si-PERK)组、阴性对照(si-NC)组;采用免疫荧光及RT-PCR验证转染效率;利用CCK-8实验检测下调PERK表达后结肠癌细胞对化疗药物5-FU的敏感性变化;Annexin V-FITC凋亡实验检测下调PERK表达对结肠癌细胞凋亡的影响;利用RT-PCR及Western Blot实验检测PERK信号通路中关键分子eIF2α、ATF4、CHOP、XIAP的mRNA及蛋白表达变化。结果:RT-PCR实验表明:与正常对照组相比,si-PERK 组mRNA的表达显著下降(P<0.05),免疫荧光提示转染效率达80%以上;CCK-8实验发现与si-NC组相比,5-FU对 si-PERK组细胞的半数抑制浓度(IC50)明显降低(P<0.01);Annexin V-FITC凋亡实验发现与si-NC组相比,si-PERK组细胞的凋亡发生率显著升高(P<0.05);RT-PCR及Western Blot实验发现与si-NC组相比,si-PERK组细胞中PERK信号通路下游关键分子eIF2α、ATF4、CHOP的mRNA及蛋白表达均明显降低(P<0.05)。结论:在结肠癌细胞中,抑制PERK表达后,其可能通过下调eIF2α、ATF4、CHOP的表达促进细胞发生凋亡,从而促进细胞对化疗药物5-FU的敏感性。  相似文献   
30.
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