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   38716篇
  免费   2402篇
  国内免费   1558篇
耳鼻咽喉   299篇
儿科学   872篇
妇产科学   522篇
基础医学   6282篇
口腔科学   875篇
临床医学   3607篇
内科学   5335篇
皮肤病学   1216篇
神经病学   1654篇
特种医学   817篇
外国民族医学   6篇
外科学   1859篇
综合类   6188篇
现状与发展   4篇
预防医学   2533篇
眼科学   408篇
药学   7005篇
  13篇
中国医学   1235篇
肿瘤学   1946篇
  2024年   36篇
  2023年   406篇
  2022年   682篇
  2021年   1223篇
  2020年   1015篇
  2019年   938篇
  2018年   910篇
  2017年   990篇
  2016年   971篇
  2015年   1066篇
  2014年   2022篇
  2013年   2124篇
  2012年   2079篇
  2011年   2466篇
  2010年   2074篇
  2009年   1916篇
  2008年   2013篇
  2007年   2123篇
  2006年   1796篇
  2005年   1883篇
  2004年   1567篇
  2003年   1508篇
  2002年   1290篇
  2001年   1124篇
  2000年   1065篇
  1999年   1026篇
  1998年   922篇
  1997年   804篇
  1996年   590篇
  1995年   711篇
  1994年   613篇
  1993年   448篇
  1992年   401篇
  1991年   287篇
  1990年   206篇
  1989年   155篇
  1988年   139篇
  1987年   120篇
  1986年   90篇
  1985年   146篇
  1984年   138篇
  1983年   107篇
  1982年   109篇
  1981年   96篇
  1980年   67篇
  1979年   48篇
  1978年   36篇
  1977年   41篇
  1976年   38篇
  1973年   16篇
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
1.
2.
Defining con-founders that affect the reliability of diagnostic tests for coronavirus disease 2019 is vital to breaking the chain of infection. The elderly population is a higher risk group for the emerging virus. However, gender seems to exert a critical role in modifying the infection risk among women owing to hormonal changes. The menopause transition is an exceptional period for older women where the protective and immunomodulatory effects of the estrogen hormone are lost. Accordingly, attention should be given to postmenopausal women since they will have an increased risk compared to their pre-menopausal peers.  相似文献   
3.
ObjectivesOur aim was to evaluate the effect of the updated European Organization for Research and Treatment of Cancer (EORTC) and Mycoses Study Group 2019 definitions for invasive pulmonary aspergillosis (IPA) on patient classification and the related all-cause 12-week mortality.MethodsIn this retrospective cohort study from our tertiary care centre, we reclassified patients with haematological malignancy who underwent bronchoalveolar lavage between 2014 and 2019 for suspected IPA using the novel EORTC 2019 criteria. We performed receiver operating characteristic curve analysis to define the optimal cut-off for positive PCR and galactomannan and present survival analyses and their possible association with these diagnostic criteria through post hoc comparisons with log rank and Cox regression.ResultsFrom 323 episodes of suspected IPA in 282 patients, 73 were reclassified: 31 (42.5%) from possible to probable IPA, 5 (6.8%) from EORTC criteria not met to probable IPA, and 37 (50.7%) from EORTC criteria not met to possible IPA. Probable IPA increased therefore 11.1% (64/323, 19.8% to 100/323, 30.9%), mostly due to positive PCR (31/36, 86.1%). There was no difference in mortality between newly defined possible and probable IPA (log rank p = 0.950). Mortality was higher in probable cases with lower cycle thresholds (Ct values) versus higher Ct values (p = 0.004). Receiver operating characteristic curve analysis showed an optimal Ct value cut-off of 36.8 with a sensitivity of 75% (95% CI 64.9%–85.1%) and a specificity of 61.7% (95% CI 53.5–69.9) for 12-week mortality.DiscussionThe new EORTC criteria led to 11.1% more probable IPA diagnoses, mostly due to Aspergillus PCR. Restricting positive PCR to below a certain threshold might improve the discrimination of the new EORTC IPA categories for mortality.  相似文献   
4.
《Vaccine》2022,40(30):4038-4045
PurposeAs protection from COVID-19 following two doses of the BNT162b2 vaccine showed a time dependent waning, a third (booster) dose was administrated. This study aims to compare the antibody response following the third dose versus the second and to evaluate post-booster seroconversion.MethodsA prospective observational study conducted in Maccabi Healthcare Services. Serial SARS-CoV-2 Spike IgG tests, 1,2,3 and 6 months following the second vaccine dose and one month following the third were obtained. Neutralizing antibody levels were measured in a subset of participants. Per individual SARS-CoV-2 Spike IgG titer ratios were calculated one month after the booster administration compared to titers one month following the second dose and prior to booster.ResultsAmong 110 participants, 56 (51%) were women. Mean age was 61.7 ± 1.9 years and 66 (60%) were immunocompromised. One month after third dose, IgG titers were induced 7.83 (95 %CI 5.25–11.67) folds and 2.40 (95 %CI 1.90–3.03) folds compared to one month after the second, in the immunocompromised and immunocompetent groups, respectively. Of the 17 immunocompromised participants who were seronegative after the second dose, 4 (24%) became seropositive following the third. Comparing the titers prior to the third dose, an increase of 50.7 (95 %CI 32.5–79.1) fold in the immunocompromised group and 25.7 (95 %CI 19.1–34.7) fold in and immunocompetent group, was observed.ConclusionA third BNT162b2 vaccine elicited robust humoral response, superior to the response observed following the second, among immunocompetent and immunocompromised individuals.  相似文献   
5.
目的:探讨阿帕替尼单药在标准治疗方案失败晚期结直肠癌(colorectal cancer,CRC)患者中的疗效和安全性。方法:本研究为前瞻性研究设计,用PASS15 软件计算研究所需的样本量,从2017 年7 月到2018 年8 月入组标准方案治疗失败的晚期CRC患者52 例,给予阿帕替尼起始剂量750 mg或500 mg单药治疗;评估患者的客观缓解率(ORR)和疾病控制率(DCR),随访评价患者的无进展生存期(PFS)和总生存期(OS),并记录治疗过程中出现的不良反应。主要研究终点为PFS,次要研究终点为ORR、DCR、OS和安全性。结果:纳入研究的52 例CRC患者中45 例可以评价疗效及安全性,其均为既往接受过至少2 次系统性化疗的晚期CRC患者。疗效:完全缓解0 例、部分缓解5 例、疾病稳定30 例、疾病进展10 例,ORR为11.11%、DCR为77.78%;预后:45 例患者的中位PFS 为3.95 个月(95% CI=3.16~4.74),中位OS为10.3 个月(95% CI=5.70~14.90);3 级以上不良反应:手足综合征6 例(13.33%),高血压5 例(11.11%),蛋白尿5 例(6.67%),转氨酶升高4 例(8.89%),腹泻3 例(6.67%),疲劳2 例(4.44%),出血1例(2.22%)。结论:阿帕替尼单药治疗标准方案失败的晚期CRC患者具有潜在的临床获益,安全性事件总体可控。  相似文献   
6.
Purpose: To use polymerase chain reaction (PCR) and Goldmann-Witmer coefficient (GWC) calculation to diagnose infectious uveitis.

Methods: Prospective cross-sectional study.

Results: Twenty-seven of 106 patients had positive PCR and/or GWC results on aqueous humor (AH) sampling and 15 of 27 (55.6%) were HIV-positive. Patients with non-anterior uveitis (NAU) were more likely to be HIV+ (p = 0.005). More than 1 possible pathogen was identified in 9 of 27 patients of whom 7 were HIV+. The final clinical diagnosis was discordant with AH findings in 9 of 27 cases. A positive EBV PCR result was associated with a discordant diagnosis (p = 0.001). All cases of herpetic anterior uveitis (42.9% HIV+) tested PCR-/GWC+ while all cases of herpetic NAU tested PCR+/GWC- (83.3% HIV+). All rubella virus cases were PCR+/GWC+.

Conclusion: PCR is useful to diagnose herpetic NAU in HIV+ patients while GWC is useful to diagnose herpetic anterior uveitis.  相似文献   

7.
Gut bacteria and gut barrier plays important roles in body homeostasis. Ciprofloxacin (CPFX) is widely used to treat bacterial infections. However, whether high dosage of CPFX has side effects on gut barrier integrity is still unclear. Our results indicated that the High CPFX treatment (1 mg/ml) caused weight loss, nervousness, anorexia, and increased apoptosis cells in gut, but less influence was observed in the Low CPFX group (0.2 mg/ml). Meanwhile, the High CPFX treatment impaired tight junction molecules Ocln/ZO-1 level and down-regulated antibacterial genes expression (reg3γ, pla2g2α and defb1). Further, the High CPFX treatment increased pro-inflammatory cytokine IL-1β in intestinal tract, decreased IL-17A of duodenum but increased IL-17A of colon at day 37. In addition, the gut bacterial diversity and richness behaved significantly loss regarding CPFX treatment, especially in the High CPFX group during the experiment. Indole exhibited sharply decline in both Low and High CPFX groups at day 7, and the High CPFX mice needed longer time on restoring indole level. Meanwhile, CPFX treatment strongly decreased the concentrations of butyric acid and valeric acid at day 1. Correlation analysis indicated that the linked patterns between the key bacteria (families Bacteroidales_S247, Ruminococcaceae and Desulfovibrionaceae) and metabolites (indole and butyric acid) were disturbed via the CPFX treatment. In conclusion, the High CPFX treatment impaired the gut barrier with the evidence of reduced expression of tight junction proteins, increased apoptosis cells and inflammatory cells, decreased the bacterial diversity and composition, which suggesting a proper antibiotic-dosage use should be carefully considered in disease treatment.  相似文献   
8.
目的探讨酪氨酸激酶受体RON及上皮型钙粘蛋白(E-cadherin)在子宫内膜异位症(endometriosis,EMs)上的表达及意义。方法选择2017年7~12月深圳市龙岗区人民医院收治的42例EMs患者,术中分别留取新鲜异位内膜组织和在位内膜组织,随机选取子宫切除或诊断性刮宫治疗的非EMs患者42例,术中留取其正常子宫内膜组织。采用逆转录聚合酶链反应(RT-PCR)检测子宫内膜组织中RON mRNA的表达,采用免疫组织化学方法检测对应42例石蜡组织中RON蛋白和E-cadherin的表达,并分析RON蛋白和E-cadherin的相关性。结果EMs异位内膜组织RON mRNA及RON蛋白阳性表达率显著高于在位内膜组织及正常子宫内膜组织(P<0.001),在位内膜组织及正常内膜组织中E-cadherin阳性表达率显著高于异位内膜组织(P<0.001),且异位内膜组织中RON mRNA及RON蛋白的表达与临床分期有关(P<0.001)。在同一标本中RON蛋白和E-cadherin表达呈负相关关系(r=-0.497,P<0.05)。结论RON的过度表达与EMs的发生发展密切相关,联合检测RON和E-cadherin的异常对判断EMs的发生发展有一定的参考价值,RON可能成为诊断治疗EMs的新靶点。  相似文献   
9.
Background: There is a huge need to develop molecular typing methods which are simple to perform, rapid and cost effective to confirm clonality of nosocomial isolates in outbreak situations. Objectives: The aim of the study was to investigate a hospital outbreak of multi-drug resistant (MDR) Klebsiellapneumoniae septicemia in a paediatric surgery intensive care unit (PSICU) using a repetitive extragenic palindromic polymerase chain reaction (REP-PCR). Materials and Methods: MDR Klebsiella pneumoniae isolates from an outbreak of nosocomial sepsis were typed byREP-PCR using consensus primers. Isolates from different intensive care units (ICUs) but with similar antibiogram were also genotyped for comparison. Results and Conclusion: A cluster of twelve MDR K Pneumoniae septicemia cases was identified at the PSICU by genotyping using REP-PCR. Surveillance cultures failed to pick up any source of infection. REP-PCR was found to be a rapid and simple tool for investigation outbreaks in hospitals. Due to early detection we could initiate infection control practices with focus on hand washing and prevent the further transmission of the organism.  相似文献   
10.
人类微生物群是由寄生在人体上皮屏障的细菌和其他微生物组成的,其中大部分位于肠道内,与宿主之间形成共生的关系。机体肠道微生物的组成虽然受到年龄、饮食、生活方式等因素的影响,但在正常生理情况下是相对稳定的。近年来,肠道菌群与恶性肿瘤的关系越来越受到重视。肠道菌群不但能够维持局部稳态,还能调节机体代谢、炎症和免疫等生理过程。有研究表明,微生物群,特别是肠道菌群能够显著调节机体对癌症治疗的反应性以及机体对毒副反应的敏感性。检查肠道菌群中各菌种之间的比例可作为筛查恶性肿瘤的新方法。本文将综述微生物群具有影响肿瘤的发生发展、抗肿瘤治疗疗效以及药物不良反应的证据,以及其中所涉及的微生物种类,从而为恶性肿瘤精准治疗提供证据。  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