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   196755篇
  免费   17967篇
  国内免费   7563篇
耳鼻咽喉   1194篇
儿科学   4624篇
妇产科学   2686篇
基础医学   37224篇
口腔科学   3775篇
临床医学   12355篇
内科学   33465篇
皮肤病学   3247篇
神经病学   16081篇
特种医学   3716篇
外国民族医学   57篇
外科学   14312篇
综合类   24132篇
现状与发展   30篇
预防医学   8859篇
眼科学   2296篇
药学   26027篇
  22篇
中国医学   6810篇
肿瘤学   21373篇
  2024年   515篇
  2023年   3101篇
  2022年   6321篇
  2021年   8012篇
  2020年   6752篇
  2019年   7785篇
  2018年   7344篇
  2017年   7239篇
  2016年   7085篇
  2015年   8502篇
  2014年   11860篇
  2013年   13244篇
  2012年   12186篇
  2011年   14445篇
  2010年   12286篇
  2009年   11649篇
  2008年   11051篇
  2007年   9843篇
  2006年   8906篇
  2005年   7590篇
  2004年   6645篇
  2003年   5643篇
  2002年   4373篇
  2001年   3731篇
  2000年   3085篇
  1999年   2801篇
  1998年   2402篇
  1997年   2178篇
  1996年   1883篇
  1995年   1583篇
  1994年   1380篇
  1993年   1163篇
  1992年   969篇
  1991年   867篇
  1990年   714篇
  1989年   599篇
  1988年   513篇
  1987年   415篇
  1986年   422篇
  1985年   796篇
  1984年   820篇
  1983年   574篇
  1982年   644篇
  1981年   508篇
  1980年   418篇
  1979年   365篇
  1978年   280篇
  1977年   221篇
  1976年   206篇
  1975年   142篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Infective endocarditis in pregnancy is extremely rare in clinical practice. Guidelines addressing prophylaxis and management of infective endocarditis do not extensively deal with concomitant pregnancy, and case reports on infective endocarditis are scarce. Due to increased blood volume and hemodynamic changes in late pregnancy, endocardial neoplasms are easy to fall off and cause systemic or pulmonary embolism, respiratory, cardiac arrest and sudden death may occur in pregnant women, the fetus can suffer from intrauterine distress and stillbirth at any time, leading to adverse outcomes for pregnant women and fetuses. The disease is dangerous and difficult to treat, which seriously threatens the lives of mothers and babies. Early diagnosis and reasonable treatment can effectively improve the prognosis of patients. The most important method for the treatment of infective endocarditis requires early, adequate, long-term and combined antibiotic therapy. Moreover, surgical controversies regarding indication and timing of treatment exist, especially in pregnancy. In terms of the timing of termination of pregnancy, the timing of cardiac surgery, and the method of surgery, individualized programs must be adopted. A pregnant woman with 30+5 weeks of gestation is reported. She was admitted to hospital due to intermittent chest tightness, suffocation and fever, with grade Ⅲ cardiac insufficiency. Imaging revealed large mitral valve vegetation, 22.0 mm×4.1 mm and 22.0 mm×5.1 mm, respectively, and severe valve regurgitation. Mitral valve perforation was more likely, blood culture suggested Staphylococcus epidermidis infection, after antibiotic conservative treatment, the effect was poor. After the joint consultation including cardiology, neonatology, interventional vascular surgery, anesthesiology, and obstetrics, the combined operation of obstetrics and cardiac surgery was performed in time. The heart was blocked for 60 minutes, the bleeding was 1 200 mL, the newborn was mildly asphyxiated after birth, and the birth weight was 1 890 g. Nine days after the operation, the patient was discharged from the hospital, and the newborn was discharged with the weight of 2 020 g. Critical cases like this require a thorough weighing of risks and benefits followed by swift action to protect the mother and her unborn child. An optimal outcome in a challenging case like this greatly depends on effective interdisciplinary communication, informed consent of the patient, and concerted action among the specialists involved.  相似文献   
992.
We investigated potential sources of infection for 6 confirmed influenza A (H5N1) patients who resided in urban areas of People's Republic of China. None had known exposure to sick poultry or poultry that died from illness, but all had visited wet poultry markets before illness.  相似文献   
993.
We reported a new method dealing with the synthesis of novel pharmacologically relevant α-aminophosphonate derivatives via a lipase-catalyzed Kabachnik−Fields reaction with yields of up to 93%. The advantages of this protocol are excellent yields, mild reaction conditions, low costs, and sustainability. The developed protocol is applicable to a range of H-phosphites and organic amines, providing a wide substrate scope. A new class of α-aminophosphonate analogues possessing P-chiral centers was also synthesized. The synthesized compounds were characterized on the basis of their antimicrobial activities against E. coli. The impact of the various alkoxy groups on antimicrobial activity was demonstrated. The crucial role of the substituents, located at the aromatic rings in the phenylethyloxy and benzyloxy groups, on the inhibitory action against selected pathogenic E. coli strains was revealed. The observed results are especially important because of increasing resistance of bacteria to various drugs and antibiotics.  相似文献   
994.
目的:了解血样制备前后放置时间对艾滋病患者外周血CD4^+、CD8^+、细胞计数的影响.方法:用艾滋病患者外周血分别在室温放置6、24、48及72 h后进行样品制备,流式细胞仪检测CD4^+、CD8^+细胞绝对计数;以及样品制备后分别在2、24、48、72及168 h上机检测;结果用SPSS软件进行统计学分析.结果:血液在室温放置72 h之内制备,CD4^+细胞计数变化差异无统计学意义(P>0.05),CD8^+细胞计数72 h与6 h比较差异有统计学意义(P<0.05);血样制备后室温放置1周内CD4^+、CD8^+细胞计数差异无统计学意义(P>0.05).结论:血液制备前在室温放置72 h后CD8^+细胞计数有明显变化;血样立即制备后室温放置1周CD4^+、CD8^+细胞计数是相对稳定的.  相似文献   
995.
PurposeKC7F2 is a novel molecule compound that can inhibit the translation of hypoxia-inducible factor 1α (HIF1α). It has been reported to exhibit potential antiangiogenic effect. We hypothesized that KC7F2 could inhibit oxygen-induced retinal neovascularization (RNV). The purpose of this study was to investigate this assumption.MethodsOxygen-induced retinopathy (OIR) models in C57BL/6J mice and Sprague-Dawley rats were used for in vivo study. After intraperitoneal injections of KC7F2, RNV was detected by immunofluorescence and hematoxylin and eosin staining. Retinal inflammation was explored by immunofluorescence. EdU incorporation assay, cell counting kit-8 assay, scratch test, transwell assay, and Matrigel assay were used to evaluate the effect of KC7F2 on the proliferation, migration and tube formation of human umbilical vein endothelial cells (HUVEC) induced by vascular endothelial growth factor (VEGF) in vitro. Protein expression was examined by Western blot.ResultsKC7F2 treatment (10 mg/kg/d) in OIR mice significantly attenuated pathological neovascularization and decreased the number of preretinal neovascular cell nuclei, without changing the avascular area, which showed the same trends in OIR rats. Consistently, after the KC7F2 intervention (10 µM), cell proliferation was inhibited in VEGF-induced HUVEC, which was in agreement with the trend observed in the retinas of OIR mice. Meanwhile, KC7F2 suppressed VEGF-induced HUVEC migration and tube formation, and decreased the density of leukocytes and microglia colocalizing neovascular areas in the retinas. Moreover, the HIF1α–VEGF pathway activated in retinas of OIR mice and hypoxia-induced HUVEC, was suppressed by KC7F2 treatment.ConclusionsThe current study revealed that KC7F2 was able to inhibit RNV effectively via HIF1α–VEGF pathway, suggesting that it might be an effective drug for RNV treatment.  相似文献   
996.
目的探讨无症状心肌缺血与心绞痛患者血浆内皮素-1变化的临床意义。方法采用放射免疫法测定ET-1含量,并查心电图及超声心动图。结果SMI与对照组无显著差异,其病变程度与ET-1变化呈零相关,AP组ET-1明显高于对照组,其病变程度与ET-1变化呈正相关,治疗后ET-1降至正常水平,AP非发作期ET-1亦有显著差异。结论结果显示血浆ET-1水平可能在冠心病心肌缺血类型和临床症状等方面起作用。  相似文献   
997.
Circular RNA (circRNA) participates in a variety of pathophysiological processes, including the development of gastric cancer (GC). However, the role of circ_0006089 in GC progression and its underlying molecular mechanism need to be further revealed. Quantitative real‐time PCR was utilized for detecting circ_0006089, microRNA (miR)‐361‐3p and transforming growth factor‐β1 (TGFB1) expression. The interaction between miR‐361‐3p and circ_0006089 or TGFB1 was confirmed using a dual‐luciferase reporter assay and an RNA immunoprecipitation (RIP) assay. Cell proliferation, metastasis, apoptosis, and angiogenesis were determined using colony formation assay, EdU assay, transwell assay, flow cytometry, and tube formation assay. Cell glycolysis was evaluated by detecting glucose consumption, lactate production, and ATP levels. In addition, western blot (WB) analysis was used to measure protein expression. Xenograft tumor models were used to assess the effect of circ_0006089 knockdown on GC tumorigenesis. circ_0006089 had been found to be upregulated in GC tissues and cells, and it could act as an miR‐361‐3p sponge. circ_0006089 knockdown suppressed GC proliferation, metastasis, glycolysis, angiogenesis, and increased apoptosis, while this effect could be revoked by miR‐361‐3p inhibitor. TGFB1 was targeted by miR‐361‐3p, and its overexpression reversed the effects of miR‐361‐3p on GC cell function. Also, circ_0006089 promoted TGFB1 expression via sponging miR‐361‐3p. Animal experiments showed that silenced circ_0006089 inhibited GC tumorigenesis through the miR‐361‐3p/TGFB1 pathway. Our results revealed that the circ_0006089/miR‐361‐3p/TGFB1 axis contributed to GC progression, confirming that circ_0006089 might be a potential therapeutic target for GC.  相似文献   
998.
Obesity is a multifactorial disease and is associated with an increased risk of developing metabolic syndrome and co-morbidities. Dysregulated expansion of the adipose tissue during obesity induces local tissue hypoxia, altered secretory profile of adipokines, cytokines and chemokines, altered profile of local tissue inflammatory cells leading to the development of low-grade chronic inflammation. Low grade chronic inflammation is considered to be the underlying mechanism that increases the risk of developing obesity associated comorbidities. The glucocorticoid induced protein annexin A1 and its N-terminal peptides are anti-inflammatory mediators involved in resolving inflammation. The aim of the current study was to investigate the role of annexin A1 in obesity and associated inflammation. To achieve this aim, the current study analysed data from two feasibility studies in clinical populations: (1) bariatric surgery patients (Pre- and 3 months post-surgery) and (2) Lipodystrophy patients. Plasma annexin A1 levels were increased at 3-months post-surgery compared to pre-surgery (1.2 ± 0.1 ng/mL, n = 19 vs. 1.6 ± 0.1 ng/mL, n = 9, p = 0.009) and positively correlated with adiponectin (p = 0.009, r = 0.468, n = 25). Plasma annexin A1 levels were decreased in patients with lipodystrophy compared to BMI matched controls (0.2 ± 0.1 ng/mL, n = 9 vs. 0.97 ± 0.1 ng/mL, n = 30, p = 0.008), whereas CRP levels were significantly elevated (3.3 ± 1.0 µg/mL, n = 9 vs. 1.4 ± 0.3 µg/mL, n = 31, p = 0.0074). The roles of annexin A1 were explored using an in vitro cell based model (SGBS cells) mimicking the inflammatory status that is observed in obesity. Acute treatment with the annexin A1 N-terminal peptide, AC2-26 differentially regulated gene expression (including PPARA (2.8 ± 0.7-fold, p = 0.0303, n = 3), ADIPOQ (2.0 ± 0.3-fold, p = 0.0073, n = 3), LEP (0.6 ± 0.2-fold, p = 0.0400, n = 3), NAMPT (0.4 ± 0.1-fold, p = 0.0039, n = 3) and RETN (0.1 ± 0.03-fold, p < 0.0001, n = 3) in mature obesogenic adipocytes indicating that annexin A1 may play a protective role in obesity and inflammation. However, this effect may be overshadowed by the continued increase in systemic inflammation associated with rapid tissue expansion in obesity.  相似文献   
999.
BackgroundObstructive sleep apnea (OSA) and inflammation are closely related. This study aimed to evaluate the associations and causal effect between C-reactive protein (CRP) and tumour necrosis factor-alpha (TNF-α) levels and OSA.MethodsPooled analysis was conducted to compare the expression differences of CRP and TNF-α between OSA patients with different severity and controls, and between continuous positive airway pressure (CPAP) and non-CPAP interventions for OSA patients. Using published GWAS summary statistics, we conducted a bidirectional two-sample Mendelian Randomization (MR) to estimate the causal relationships between CRP and TNF-α levels and OSA risk. Effect estimates were evaluated using inverse-variance weighted (IVW) as primary method, and several other MR methods as sensitivity analysis.ResultsBoth TNF-α (WMD [95%CI] = 5.86 [4.80–6.93] pg/ml, p < .00001) and CRP (WMD [95%CI] = 2.66 [2.15–3.17] mg/L, p < .00001), showed a significant increase in OSA patients compared with controls and this increasing trend was associated with OSA severity. Besides, compared to blank control (non-CPAP), CPAP treatment can reduce high TNF-α (WMD [95%CI]= −4.44 [−4.81, −4.07]pg/ml, p < .00001) and CRP (WMD [95%CI]= −0.91 [−1.65, −0.17] mg/l, p = .02) in OSA. Moreover, the primary MR analysis by IVW showed that OSA was the genetically predicted cause of elevated CRP (estimate: 0.095; 95% CI, [0.010–0.179]; p = .029) using six SNPs as the instrument variable, which were repeated by weighted median (estimate: 0.053; 95% CI, [0.007, 0.100]; p =.024) and MR RAPS (estimate: 0.109; 95% CI, [0.079, 0.140]; p = 1.98x10−12). Besides, the causal effect from elevated CRP on increased OSA risk was almost significant by IVW (OR:1.053; 95% CI, [1.000, 1.111]; p = .053). However, there were no causal associations between TNF-α and OSA from both directions.ConclusionsIncreased CRP and TNF-α were associated with OSA severity and sensible to CPAP treatment. Also, OSA had a suggestive causal effect on elevated CRP.  相似文献   
1000.
目的探索褐藻素(FX)对糖尿病心肌病的保护效应和作用机制。方法腹腔注射链脲佐菌素建立糖尿病大鼠模型,进行分组:糖尿病组(DM)、褐藻素干预糖尿病组(DM+FX)和二甲双胍干预糖尿病组(DM+Met),另取正常大鼠给予正常喂养作为正常组(Con)。造模成功后连续12周每日灌胃给药,褐藻素组每日给予200 mg/kg褐藻素灌胃,二甲双胍组每日给予230 mg/kg灌胃,糖尿病组同步灌胃生理盐水。HE染色观察各组大鼠心脏细胞肥大情况;Western blot法检测大鼠心脏中纤维化蛋白TGF-β1和FN蛋白表达水平。H9C2细胞分为3组:正常糖组(NG,5.5 mmol/L葡萄糖)、高糖组(HG,45 mmol/L葡萄糖)和褐藻素干预高糖组(HG+1 μmol/L FX)。FITC标记的鬼笔环肽检测大鼠心肌细胞H9C2表面积变化;qRT-PCR法测定各组细胞肥大因子ANP、BNP和β-MHC基因表达变化;Western blot法检测各组大鼠心脏组织和H9C2细胞中Nrf2、Keap1、HO-1、SOD1蛋白表达水平;DCFH-DA探针检测细胞内活性氧水平变化。结果褐藻素改善糖尿病大鼠心肌纤维化和心肌细胞肥大,同时上调心脏组织中Nrf2和HO-1蛋白表达,抑制Keap1蛋白表达(P < 0.05)。褐藻素可抑制高糖诱导H9C2心肌细胞表面积增加,降低ANP、BNP和β-MHC的mRNA表达水平(P < 0.05)。褐藻素可促进高糖诱导的H9C2细胞中Nrf2入核,上调下游靶蛋白SOD1和HO-1蛋白表达(P < 0.05)来增强细胞抗氧化能力,降低细胞内活性氧的水平。结论褐藻素具有良好的抗糖尿病心肌纤维化和心肌细胞肥大作用,同时上调Nrf2信号通路并促进下游抗氧化蛋白SOD1和HO-1的表达,降低活性氧水平。  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