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   21939篇
  免费   2311篇
  国内免费   948篇
耳鼻咽喉   101篇
儿科学   958篇
妇产科学   153篇
基础医学   2705篇
口腔科学   335篇
临床医学   1482篇
内科学   7345篇
皮肤病学   217篇
神经病学   286篇
特种医学   736篇
外国民族医学   1篇
外科学   2460篇
综合类   3307篇
现状与发展   3篇
预防医学   750篇
眼科学   164篇
药学   2061篇
  5篇
中国医学   1613篇
肿瘤学   516篇
  2024年   82篇
  2023年   461篇
  2022年   692篇
  2021年   969篇
  2020年   1064篇
  2019年   1000篇
  2018年   1011篇
  2017年   1019篇
  2016年   884篇
  2015年   970篇
  2014年   1342篇
  2013年   1604篇
  2012年   1284篇
  2011年   1367篇
  2010年   1189篇
  2009年   1123篇
  2008年   1177篇
  2007年   1133篇
  2006年   1010篇
  2005年   889篇
  2004年   694篇
  2003年   544篇
  2002年   485篇
  2001年   422篇
  2000年   320篇
  1999年   283篇
  1998年   288篇
  1997年   237篇
  1996年   196篇
  1995年   167篇
  1994年   159篇
  1993年   127篇
  1992年   118篇
  1991年   85篇
  1990年   87篇
  1989年   54篇
  1988年   67篇
  1987年   72篇
  1986年   67篇
  1985年   84篇
  1984年   70篇
  1983年   30篇
  1982年   71篇
  1981年   50篇
  1980年   38篇
  1979年   23篇
  1978年   22篇
  1977年   18篇
  1976年   18篇
  1974年   10篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
《Cancer radiothérapie》2022,26(4):611-615
In order to provide more convenient irradiation regimens for patient comfort, radiation facility organization and health expenses, new hypofractionated protocols have been evaluated. Moderately (dose/fraction: 2.3 to 3 Gy), then ultra (dose/fraction: 5.2 to 6.1 Gy) hypofractionated irradiations were first validated. The current question is: is it possible to go forward using extreme hypofractionated regimens (EHR) based on 1 to 3 fractions. Different irradiation techniques are under investigation. However, brachytherapy remains the smartest way to deliver a high dose in a small volume. We report prospective and retrospective study results which evaluated EHR for breast and prostate brachytherapy. While oncological outcome and toxicity profile appear extremely encouraging for low-risk breast cancer after a 1 to 4 fractions (6.25 to 20 Gy/fraction), the use of a single fraction of 19 to 23 Gy appears debatable for prostate cancer. Brachytherapy represents an emblematic example of EHR but longer follow-up and more mature results are awaited in order to specify the right indications and refine the EQD2 calculation method including new biological and technical factors.  相似文献   
2.
Noninvasive imaging of cardiac fibrosis is important for early diagnosis and intervention in chronic heart diseases. Here, we investigated whether noninvasive, contrast agent-free MRI T2-mapping can quantify myocardial fibrosis in preclinical models of aging and pressure overload. Myocardial fibrosis and remodeling were analyzed in two animal models: (i) aging (15-month-old male CF-1 mice vs. young 6- to 8-week-old mice), and (ii) pressure overload (PO; by transverse aortic constriction in 4- to 5-month-old male C57BL/6 mice vs. sham-operated for 14 days). In vivo T2-mapping was performed by acquiring data during the isovolumic and early diastolic phases, with a modified respiratory and ECG-triggered multiecho TurboRARE sequence on a 7-T MRI. Cine MRI provided cardiac morphology and function. A quantitative segmentation method was developed to analyze the in vivo T2-maps of hearts at midventricle, apex, and basal regions. The cardiac fibrosis area was analyzed ex vivo by picro sirius red (PSR) staining. Both aged and pressure-overloaded hearts developed significant myocardial contractile dysfunction, cardiac hypertrophy, and interstitial fibrosis. The aged mice had two phenotypes, fibrotic and mild-fibrotic. Notably, the aged fibrotic subgroup and the PO mice showed a marked decrease in T2 relaxation times (25.3 ± 0.6 in aged vs. 29.9 ± 0.7 ms in young mice, p = 0.002; and 24.3 ± 1.7 in PO vs. 28.7 ± 0.7 ms in shams, p = 0.05). However, no significant difference in T2 was detected between the aged mild-fibrotic subgroup and the young mice. Accordingly, an inverse correlation between myocardial fibrosis percentage (FP) and T2 relaxation time was derived (R2 = 0.98): T2 (ms) = 30.45 – 1.05 × FP. Thus, these results demonstrate a statistical agreement between T2-map–quantified fibrosis and PSR staining in two different clinically relevant animal models. In conclusion, T2-mapping MRI is a promising noninvasive contrast agent-free quantitative technique to characterize myocardial fibrosis.  相似文献   
3.
目的 通过分析特发性肺纤维化急性加重期(AE-IPF)患者证候与血清生物标志物的关系,为中医辨证治疗提供参考。方法 采用观察性研究设计,收集2019年3月至2019年11月三个中心的AE-IPF患者76例,其中痰热壅肺证26例、痰浊阻肺证50例,并纳入健康志愿者10例作为对照。采用ELISA测定患者血清CCL18、HMGB1、KL-6、MMP-7、SP-A和SP-D水平,分析与中医证候的相关性。结果 AE-IPF患者血清CCL18、HMGB1、KL-6、MMP-7、SP-A和SP-D水平均显著高于健康对照组。血清CCL18、HMGB1、KL-6、MMP-7和SP-D水平在痰热壅肺证和痰浊阻肺证患者间无显著性差异(P>0.05),而血清SP-A水平存在显著性差异(P<0.05)。结论 血清SP-A与AE-IPF证候存在一定的相关性,血清SP-A的浓度升高,与痰热壅肺证关系越密切,反之,血清SP-A浓度降低,则与痰浊阻肺证关系越密切。AE-IPF痰热壅肺证患者的预后可能较痰浊阻肺证患者更差。  相似文献   
4.
目的 运用网络药理学方法及分子对接技术探讨黄芪干预腹膜纤维化的可能机制。方法 利用中药系统药理学数据库及分析平台(TCMSP)检索黄芪的主要化学成分及靶点,并补充文献报道相关药理作用的成分作为潜在活性成分。以"peritoneal fibrosis"为关键词分别在OMIM、Genecards获取目前已知的与腹膜纤维化相关的疾病靶点,后取两者的交集靶点;对交集基因通过STRING数据库与Cytoscape 3.7.2软件构建"药物-成分-靶点-疾病"网络及蛋白互作(PPI)网络并筛选核心网络。基于R软件使用Bioconductor生物信息软件对核心靶点进行GO及KEGG富集分析,最终采用AutoDock软件将主要有效成分与核心靶点进行分子对接,得出其结合能力。结果 筛选出20个黄芪活性成分及文献报道有相关药理作用4个, 457药物作用靶点,与674个腹膜纤维化病靶点取交集,得到86个共同靶点。GO功能富集分析提示黄芪拮抗腹膜纤维化主要参与了蛋白激酶B信号转导的调节、细胞对化学的应激反应、炎症反应的调节等通路; KEGG通路富集分析主要涉及调控肿瘤、磷脂酰肌醇-3-羟激酶-蛋白激酶B(PI3K-Akt)、晚期糖基化终末产物/晚期糖基化终末产物受体(AGE-RAGE)、人类巨细胞病毒感染、HIF-1信号通路等;分子对接结果显示关键靶点与活性成分具有较好的结合能力。结论 黄芪治疗腹膜纤维化的分子机制,可能与抑制炎症及氧化应激反应、调节多种信号通路等相关。  相似文献   
5.
6.

Background

Resistin is an immunometabolic mediator that is elevated in several inflammatory disorders. A ligand for Toll-like receptor 4, resistin modulates the recruitment and activation of myeloid cells, notably neutrophils. Neutrophils are major drivers of cystic fibrosis (CF) lung disease, in part due to the release of human neutrophil elastase- and myeloperoxidase-rich primary granules, leading to tissue damage. Here we assessed the relationship of resistin to CF lung disease.

Methods

Resistin levels were measured in plasma and sputum from three retrospective CF cohorts spanning a wide range of disease. We also assessed the ability of neutrophils to secrete resistin upon activation in vitro. Finally, we constructed a multivariate model assessing the relationship between resistin levels and lung function.

Results

Plasma resistin levels were only marginally higher in CF than in healthy control subjects. By contrast, sputum resistin levels were very high in CF, reaching 50–100 fold higher levels than in plasma. Among CF patients, higher plasma resistin levels were associated with allergic bronchopulmonary aspergillosis, and higher sputum resistin levels were associated with CF-related diabetes. Mechanistically, in vitro release of neutrophil primary granules was concomitant with resistin secretion. Overall, sputum resistin levels were negatively correlated with CF lung function, independently of other variables (age, sex, and genotype).

Conclusions

Our data establish relationships between resistin levels in the plasma and sputum of CF patients that correlate with disease status, and identify resistin as a novel mechanistic link between neutrophilic inflammation and lung disease in CF.  相似文献   
7.
PurposeTo explore the safety and effectiveness of bronchial artery (BA) embolization (BAE) in children with pulmonary hemorrhage.Materials and MethodsBetween February 2016 and February 2019, 41 patients (median age, 4 y; interquartile range, 2.3-8 y; median weight, 17.6 kg; interquartile range, 12.3–23.6 kg) underwent BAE. The indication of BAE included massive hemoptysis in 10 patients (24.4%), recurrent hemoptysis in 18 patients (43.9%), and refractory anemia in 13 patients (31.7%). The main etiology of pulmonary hemorrhage included pulmonary hemosiderosis (58.5%), congenital heart disease (17.1%), and infection (14.6%). A retrospective review was conducted of clinical outcomes of BAE.ResultsThere were 44 embolization sessions, with a total of 137 embolized vessels. Pulmonary hemorrhage was caused by BAs in 30 cases, nonbronchial systemic arteries plus BAs in 10, and nonbronchial systemic arteries in 1. Embolic particles were used in 30 cases (24 polyvinyl alcohol [PVA] and 6 microsphere), coils in 9 cases, and particles plus coils in 5 cases (4 PVA and 1 microsphere). Technical success (ability to embolize abnormal vessel) was achieved in 97.6% of patients (40 of 41), and clinical success (complete or partial resolution of hemoptysis within 30 days of embolization) was achieved in 90.2% (37 of 41). There was 1 procedure-related complication (2.4%) of cerebral infarction and 1 death from multiple-organ dysfunction (2.4%). Bleeding-free survival rates at 6, 12, 24, and 36 months were 92.5%, 83.9%, 83.9%, and 70.8%, respectively.ConclusionsBAE is a safe and effective procedure in children with pulmonary hemorrhage.  相似文献   
8.
9.
10.
Background: Pulmonary manifestations of systemic lupus erythematosus (SLE) are appearing in 4-5% of patients involving lung in almost half of the cases during the disease course. Objective: We compared the autoimmune pulmonary inflammation in the lung tissue of mice to determine the association between decreased expression levels of Forkhead Box J1 (FOXJ1) and the activation of the NF-κB pathway in autoimmune pulmonary inflammation of MRL/Lpr mice. Methods: The female BALB/c mice (n=6) and MRL/Lpr mice (n=30) were divided into 5 groups including a control group (BALB/c), and five MRL/Lpr mice groups (8W, 12W, 16W, 24W, and 32W). The infiltration of the inflammatory cells was determined in lung tissue by performing the histological analysis. The western blotting was used to examine the expression levels of the age-related FOXJ1, and p50 and p65 proteins in the lungs of MRL/Lpr mice. The expression levels of MMP2 and MMP9 were determined via immunohistochemistry and immunofluorescence. Results: There were severe infiltrates of lung cells with high levels of tracheal damage, perivascular injury and interstitial inflammatory cell infiltration when the MRL/Lpr mice from 16w to 32w comparing to the 8w old healthy MRL/Lpr mice in the control group (p <0.05). Moreover, the reduced expression levels of FOXJ1 were associated with the activation of the NF-κB pathway in interstitial lung disease of MRL/Lpr mice via the modulation of p50 and p65. In addition, the expression levels of MMP2 and MMP9 pro-inflammation factors increased in the lungs of the MRL/Lpr mice from 16w to 32w. Conclusions: The expression level of FOXJ1 might be an indicator of the degree of lung disease in lupus-prone mice.  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