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   300704篇
  免费   28521篇
  国内免费   21202篇
耳鼻咽喉   2644篇
儿科学   3289篇
妇产科学   3680篇
基础医学   33918篇
口腔科学   5042篇
临床医学   40331篇
内科学   43010篇
皮肤病学   3007篇
神经病学   15773篇
特种医学   11268篇
外国民族医学   158篇
外科学   30252篇
综合类   53770篇
现状与发展   76篇
一般理论   22篇
预防医学   19991篇
眼科学   8472篇
药学   31633篇
  290篇
中国医学   19115篇
肿瘤学   24686篇
  2024年   1017篇
  2023年   4680篇
  2022年   11907篇
  2021年   15099篇
  2020年   11590篇
  2019年   9907篇
  2018年   10343篇
  2017年   9592篇
  2016年   8901篇
  2015年   13611篇
  2014年   16894篇
  2013年   15311篇
  2012年   22352篇
  2011年   25106篇
  2010年   16192篇
  2009年   13079篇
  2008年   16534篇
  2007年   16253篇
  2006年   15996篇
  2005年   15374篇
  2004年   10382篇
  2003年   9907篇
  2002年   8420篇
  2001年   7128篇
  2000年   6963篇
  1999年   6888篇
  1998年   4221篇
  1997年   4231篇
  1996年   3334篇
  1995年   3067篇
  1994年   2540篇
  1993年   1631篇
  1992年   2105篇
  1991年   1802篇
  1990年   1445篇
  1989年   1232篇
  1988年   1130篇
  1987年   982篇
  1986年   798篇
  1985年   588篇
  1984年   372篇
  1983年   260篇
  1982年   163篇
  1981年   152篇
  1980年   124篇
  1979年   149篇
  1978年   54篇
  1977年   60篇
  1975年   63篇
  1974年   64篇
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
991.
张少浩  朱勇冬  林麒 《安徽医药》2024,28(7):1430-1434
目的分析病毒性脑炎并发症状性癫痫的风险因素,据此构建列线图预测模型。方法回顾性分析 2018年 2月至 2022年 5月汕头市中心医院收治的 217例病毒性脑炎病人临床资料,抽取 70%为建模集(152例),30%为验证集(65例)。根据病人是否合并症状性癫痫,将建模集进一步分为发生组和未发生组,比较两组病人一般资料,选择差异有统计学意义的指标用逐步向前回归法进行非条件多因素 logistic分析病毒性脑炎病人症状性癫痫发生的影响因素,并采用 R3.4.3软件包绘制基于多因素分析结果的列线图模型。采用 Bootstrap法分别对建模集和验证集进行验证,并绘制受试者操作特征曲线(ROC曲线)和决策曲线(DCA)以评估列线图模型的预测效能和临床净获益率。结果 217例病毒性脑炎病人中,共 46例病人合并症状性癫痫(21.20%),其中建模集中有 32例合并症状性癫痫,验证集中有 14例合并症状性癫痫;发生组昏迷、大脑皮质损坏、脑电图重度异常、颅脑核磁共振成像(MRI)有责任病灶、累及颞叶或额叶、脑脊液单纯疱疹病毒(HSV)(+)占比及脑脊液压力均高于未发生组(P<0.05); logistic多元回归分析,昏迷、大脑皮质损坏、脑电图重度异常、颅脑 MRI有责任病灶、累及颞叶或额叶、脑脊液压力、脑脊液 HSV(+)均是病毒性脑炎合并症状性癫痫的影响因素(P<0.05);经 Bootsrap法进行验证,建模集其一致性指数( C-index)为 0.833,验证集的 Cindex则为 0.830,校正曲线和标准曲线拟合度较好。建模集 ROC曲线下面积(AUC)、灵敏度、特异度分别为 0.84[98%CI:(0.78,0.89)]、79.17%、84.04%,验证集则为 0.81[98%CI:(0.76,0.86)],83.04%,73.64%,提示模型区分度良好。 DCA曲线显示病人根据列线图模型进行风险评估可获得满意的净收益。结论昏迷、大脑皮质损坏、脑电图重度异常、颅脑 MRI有责任病灶、累及颞叶或额叶、脑脊液压力、脑脊液 HSV(+)均是病毒性脑炎合并症状性癫痫的影响因素,综合上述因素针对病毒性脑炎病人构建的列线图预测模型可以较好地个体化预测症状性癫痫的发生,对临床防治症状性癫痫提供指导。  相似文献   
992.
Aluminum alloy (Al6061-T6) is an alloy with strong corrosion resistance, excellent disassembly, and moderate strength, which is widely used in the fields of construction, automobile, shipping, and aerospace manufacturing. Researching on the influence of machining precision and surface quality on the micro-milling process of thin-walled structures of Al6061 is highly significant. Combined with the two simulations (DEFORM-3D simulation and interactive finite element numerical simulation (FEM)) and milling experimental verification, the deformations, errors, and surface quality of milling thin-walled Al6061 were analyzed. The simulations and experimental results show that the deformation of milling a micro thin-walled structure was caused by the vertical stiffness of the thin-walled structure and the cutting force. Surface micromorphology further characterized and showed a poorer quality area, top burr, and concave defects, which directly affect machining quality. It is necessary to improve the surface quality, reduce the surface defects, and increase the stiffness at the top of thin-walled structures in future work.  相似文献   
993.
Porcine epidemic diarrhea (PED), characterized by diarrhea, vomiting, and dehydration, is an acute enteric infectious disease of pigs. The disease is caused by porcine epidemic diarrhea virus (PEDV), which infects the intestinal mucosal surface. Therefore, mucosal immunization through the oral route is an effective method of immunization. Lactic acid bacteria, which are acid resistant and bile-salt resistant and improve mucosal immunity, are ideal carriers for oral vaccines. The S1 glycoprotein of PEDV mediates binding of the virus with cell receptors and induces neutralizing antibodies against the virus. Therefore, we reversely screened the recombinant strain pPG-SD-S1/Δupp ATCC 393 expressing PEDV S1 glycoprotein by Lactobacillus casei deficient in upp genotype (Δupp ATCC 393). Mice were orally immunized three times with the recombinant bacteria that had been identified for expression, and the changes of anti-PEDV IgG and secreted immunoglobulin A levels were observed over 70 days. The results indicated that the antibody levels notably increased after oral administration of recombinant bacteria. The detection of extracellular cytokines on the 42nd day after immunization indicated high levels of humoral and cellular immune responses in mice. The above results demonstrate that pPG-SD-S1/Δupp ATCC 393 has great potential as an oral vaccine against PEDV.  相似文献   
994.
目的 探讨低剂量辐射(LDR)对Lewis肺癌小鼠肿瘤微环境(TME)的影响,以及高剂量辐射(HDR)前LDR预处理在TME中发挥的效应机制.方法 接种Lewis肺癌细胞(1×106)于雄性C57BL/6小鼠左侧腋下,待小鼠肿瘤直径1 cm左右(12 d),随机分为假手术Sham(1)组、LDR(2)组、HDR(3)组...  相似文献   
995.
The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2, SARS2) remains a great global health threat and demands identification of more effective and SARS2-targeted antiviral drugs, even with successful development of anti-SARS2 vaccines. Viral replicons have proven to be a rapid, safe, and readily scalable platform for high-throughput screening, identification, and evaluation of antiviral drugs against positive-stranded RNA viruses. In the study, we report a unique robust HIV long terminal repeat (LTR)/T7 dual-promoter-driven and dual-reporter firefly luciferase (fLuc) and green fluorescent protein (GFP)-expressing SARS2 replicon. The genomic organization of the replicon was designed with quite a few features that were to ensure the replication fidelity of the replicon, to maximize the expression of the full-length replicon, and to offer the monitoring flexibility of the replicon replication. We showed the success of the construction of the replicon and expression of reporter genes fLuc and GFP and SARS structural N from the replicon DNA or the RNA that was in vitro transcribed from the replicon DNA. We also showed detection of the negative-stranded genomic RNA (gRNA) and subgenomic RNA (sgRNA) intermediates, a hallmark of replication of positive-stranded RNA viruses from the replicon. Lastly, we showed that expression of the reporter genes, N gene, gRNA, and sgRNA from the replicon was sensitive to inhibition by Remdesivir. Taken together, our results support use of the replicon for identification of anti-SARS2 drugs and development of new anti-SARS strategies targeted at the step of virus replication.  相似文献   
996.
997.
Drug-induced hyperglycemia/diabetes is a global issue. Some drugs induce hyperglycemia by activating the pregnane X receptor (PXR), but the mechanism is unclear. Here, we report that PXR activation induces hyperglycemia by impairing hepatic glucose metabolism due to inhibition of the hepatocyte nuclear factor 4-alpha (HNF4α)‒glucose transporter 2 (GLUT2) pathway. The PXR agonists atorvastatin and rifampicin significantly downregulated GLUT2 and HNF4α expression, and impaired glucose uptake and utilization in HepG2 cells. Overexpression of PXR downregulated GLUT2 and HNF4α expression, while silencing PXR upregulated HNF4α and GLUT2 expression. Silencing HNF4α decreased GLUT2 expression, while overexpressing HNF4α increased GLUT2 expression and glucose uptake. Silencing PXR or overexpressing HNF4α reversed the atorvastatin-induced decrease in GLUT2 expression and glucose uptake. In human primary hepatocytes, atorvastatin downregulated GLUT2 and HNF4α mRNA expression, which could be attenuated by silencing PXR. Silencing HNF4α downregulated GLUT2 mRNA expression. These findings were reproduced with mouse primary hepatocytes. Hnf4α plasmid increased Slc2a2 promoter activity. Hnf4α silencing or pregnenolone-16α-carbonitrile (PCN) suppressed the Slc2a2 promoter activity by decreasing HNF4α recruitment to the Slc2a2 promoter. Liver-specific Hnf4α deletion and PCN impaired glucose tolerance and hepatic glucose uptake, and decreased the expression of hepatic HNF4α and GLUT2. In conclusion, PXR activation impaired hepatic glucose metabolism partly by inhibiting the HNF4α‒GLUT2 pathway. These results highlight the molecular mechanisms by which PXR activators induce hyperglycemia/diabetes.Key words: Pregnane X receptor, Hepatocyte nuclear factor 4-alpha, Glucose transporter 2, Hepatic glucose uptake, Diabetes, Drug-induced hyperglycemia  相似文献   
998.
文章对妊娠早期的胚胎发育监测进行介绍.  相似文献   
999.
ContextThe risk of contrast-induced acute kidney injury (CI-AKI) is increasing and the harm is great. Quercetin is the main active component in Abelmoschus manihot (L.) Medik (Malvaceae) and was reported to reduce the expression of HIF-1α.ObjectiveWe investigate whether quercetin improves the CI-AKI through the HIF-1α/lncRNA NEAT1/HMGB1 pathway.Materials and methodsHK-2 cells were treated with iohexol (200 mg/mL) for 6 h to establish a CI-AKI model. Quercetin (20 μM) was administered to CI-AKI cells cultured in dishes for 24 h. Cell morphology was observed by a fluorescence microscope. MTT and TUNEL assays were used to detect cell survival rate and apoptosis. Relative mRNA levels were measured by qRT-PCR. Protein levels were detected using western blotting. IL-6 and TNF-α protein levels were tested by Elisa assay. Targeting binding sites of HIF-1α and lncRNA NEAT1 were detected by luciferase assay.ResultsThe IC50 value of quercetin was 163.25 μM. The expression levels of HIF-1α, lncRNA NEAT1 and HMGB1 were upregulated in the CI-AKI cell model. Quercetin diminished cell injury and apoptosis via inhibiting HIF-1α. Silencing of HIF-1α targeting lncRNA MEAT1 diminished cell injury and apoptosis. Silencing lncRNA NEAT1 has the same effect via suppressing HMGB1 expression. Collectively, quercetin diminished cell injury and apoptosis in CI-AKI cell model via the inhibition of HIF-1α on lncRNA NEAT1/HMGB1 signalling pathway.Discussion and conclusionsQuercetin diminished cell injury and apoptosis in CI-AKI cell mode via the inhibition of HIF-1α on the lncRNA NEAT1/HMGB1 signalling pathway, offering a potential novel therapeutic target for CI-AKI therapy.  相似文献   
1000.
BackgroundBecause trends in the epidemiology and burden of gastroesophageal reflux disease (GERD) are changing, reinvestigating the geographical differences and trend changes is essential. Here we evaluated the latest epidemiologic patterns and trends for GERD, using data from Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019.MethodsAnnual case numbers, age-standardized rates of prevalence, incidence, and years of life lived with disability (YLDs), and their estimated annual percentage changes (EAPCs) for GERD between 1990 and 2019 were derived from the GBD 2019 study. Association between GERD burden and socio-demographic index (SDI) was also investigated.ResultsIn 2019, there were 783.95 million cases of GERD globally. Between 1990 and 2019, the total number of prevalent cases, incident cases, and YLDs increased by 77.53%, 74.79%, and 77.19%, respectively. The global age-standardized incidence rate (ASIR) and age-standardized YLD rate (ASYR) increased during this period (EAPC = 0.06 and 0.05, respectively). Tropical Latin America and East Asia had the highest and lowest age-standardiZed prevalence rate (ASPR), ASIR, and ASYR in 2019, respectively. From 1990 to 2019, prevalent cases, incident cases, YLDs, and their corresponding age-standardized rates of GERD were higher in females than males in all years. Higher SDI was associated with lower ASPR, ASIR, and ASYR of GERD in 2019.ConclusionsGERD will continue to be a major public health burden due to increasing numbers of prevalent cases, incident cases, and YLDs. In order to tackle this troublesome disease, it is crucial to understand the changes in both global and regional trends in epidemiology and the burden for policymakers and other stakeholders.

Key messages

  • This is the most updated estimate on GERD epidemiology globally, including 204 countries, some of which were not assessed before.
  • The overall burden of GERD continued to worsen with the prevalent cases increasing by 77.53% from 441.57 million in 1990 to 783.95 million in 2019.
  • GERD is likely to remain a common reason for consultation in primary care, and our data may allow for health service provision planning.
  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