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   186884篇
  免费   14417篇
  国内免费   4385篇
耳鼻咽喉   1443篇
儿科学   2985篇
妇产科学   4330篇
基础医学   23979篇
口腔科学   4053篇
临床医学   13354篇
内科学   22656篇
皮肤病学   2527篇
神经病学   12123篇
特种医学   6799篇
外国民族医学   2篇
外科学   16346篇
综合类   25810篇
现状与发展   21篇
一般理论   8篇
预防医学   15573篇
眼科学   2405篇
药学   25806篇
  78篇
中国医学   12595篇
肿瘤学   12793篇
  2024年   151篇
  2023年   2337篇
  2022年   3230篇
  2021年   7118篇
  2020年   6486篇
  2019年   6414篇
  2018年   6454篇
  2017年   7121篇
  2016年   7197篇
  2015年   6714篇
  2014年   7844篇
  2013年   11902篇
  2012年   9574篇
  2011年   11528篇
  2010年   7334篇
  2009年   7454篇
  2008年   8851篇
  2007年   9816篇
  2006年   9355篇
  2005年   8673篇
  2004年   7419篇
  2003年   6661篇
  2002年   5192篇
  2001年   4684篇
  2000年   3954篇
  1999年   3290篇
  1998年   2458篇
  1997年   2500篇
  1996年   2289篇
  1995年   2156篇
  1994年   2083篇
  1993年   1756篇
  1992年   1623篇
  1991年   1518篇
  1990年   1315篇
  1989年   1080篇
  1988年   1044篇
  1987年   943篇
  1986年   870篇
  1985年   1255篇
  1984年   999篇
  1983年   756篇
  1982年   783篇
  1981年   637篇
  1980年   616篇
  1979年   493篇
  1978年   309篇
  1977年   270篇
  1976年   249篇
  1975年   188篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
41.
《Saudi Dental Journal》2022,34(7):596-603
ObjectiveStudies have shown that gingival crevices may be a significant route for SARS-CoV-2 entry. However, the role of oral health in the acquisition and severity of COVID-19 is not known.DesignA retrospective analysis was performed using electronic health record data from a large urban academic medical center between 12/1/2019 and 8/24/2020. A total of 387 COVID-19 positive cases were identified and matched 1:1 by age, sex, and race to 387 controls without COVID-19 diagnoses. Demographics, number of missing teeth and alveolar crestal height were determined from radiographs and medical/dental charts. In a subgroup of 107 cases and controls, we also examined the rate of change in alveolar crestal height. A conditional logistic regression model was utilized to assess association between alveolar crestal height and missing teeth with COVID-19 status and with hospitalization status among COVID-19 cases.ResultsIncreased alveolar bone loss, OR = 4.302 (2.510 – 7.376), fewer missing teeth, OR = 0.897 (0.835–0.965) and lack of smoking history distinguished COVID-19 cases from controls. After adjusting for time between examinations, cases with COVID-19 had greater alveolar bone loss compared to controls (0.641 ± 0.613 mm vs 0.260 ± 0.631 mm, p < 0.01.) Among cases with COVID-19, increased number of missing teeth OR = 2.1871 (1.146– 4.174) was significantly associated with hospitalization.ConclusionsAlveolar bone loss and missing teeth are positively associated with the acquisition and severity of COVID-19 disease, respectively.  相似文献   
42.
43.
AimTo determine whether convalescent angiotensin (1?7) peptide replacement therapy with plasma (peptide plasma) transfusion can be beneficial in the treatment of critically ill patients with severe coronavirus 2 (SARS-CoV-2) infection.Study designCase series of 9 critically ill patients with laboratory-confirmed COVID-19 who met the following criteria: severe pneumonia with rapid progression and continuously high viral load despite antiviral treatment.Peptide plasma: Plasma with angiotensin (1?7) content 8–10 times higher than healthy plasma donors was obtained from suitable donors. Peptide plasma transfusion was applied to 9 patients whose clinical status and/or laboratory profile deteriorated and who needed intensive care for 2 days.ResultsIn our COVID-19 cases, favipiravir, low molecular weight heparin treatment, which is included in the treatment protocol of the ministry of health, was started. Nine patients with oxygen saturation of 93% and below despite nasal oxygen support, whose clinical and/or laboratory deteriorated, were identified. The youngest of the cases was 36 years old, and the oldest patient was 85 years old. 6 of the 9 cases had male gender. 3 cases had been smoking for more than 10 years. 4 cases had at least one chronic disease.In all of our cases, SARS CoV2 lung involvement was bilateral and peptide plasma therapy was administered in cases when oxygen saturation was 93% and below despite nasal oxygen support of 5 liters/minute and above, and intensive care was required. Although it was not reflected in the laboratory parameters in the early period, 8 patients whose saturations improved with treatment were discharged without the need for intensive care. However, a similar response was not obtained in one case. Oxygen requirement increased gradually and, he died in intensive care process. An increase of the platelet count was observed in all cases following the peptide plasma treatment.ConclusionIn this preliminary case series of 9 critically ill patients with COVID-19, administration of plasma containing angiotensin (1?7) was followed by improvement in their clinical status. The limited sample size and study design preclude a definitive statement about the potential effectiveness of this treatment, and these observations require evaluation in clinical trials.  相似文献   
44.
Frameworks for deriving occupational exposure limits (OELs) and OEL-analogue values (such as derived-no-effect levels [DNELs]) in various regulatory areas in the EU and at national level in Germany were analysed. Reasons for differences between frameworks and possible means of improving transparency and harmonisation were identified. Differences between assessment factors used for deriving exposure limits proved to be one important reason for diverging numerical values. Distributions for exposure time, interspecies and intraspecies extrapolation were combined by probabilistic methods and compared with default values of assessment factors used in the various OEL frameworks in order to investigate protection levels. In a subchronic inhalation study showing local effects in the respiratory tract, the probability that assessment factors were sufficiently high to protect 99% and 95% of the target population (workers) from adverse effects varied considerably from 9% to 71% and 17% to 87%, respectively, between the frameworks. All steps of the derivation process, including the uncertainty associated with the point of departure (POD), were further analysed with two examples of full probabilistic assessments. It is proposed that benchmark modelling should be the method of choice for deriving PODs and that all OEL frameworks should provide detailed guidance documents and clearly define their protection goals by stating the proportion of the exposed population the OEL aims to cover and the probability with which they intend to provide protection from adverse effects. Harmonisation can be achieved by agreeing on the way to perform the methodological steps for deriving OELs and on common protection goals.  相似文献   
45.
46.
Recently, we reported that titanium dioxide (TiO2) materials activated endothelial cells via Kruppel-like factor (KLF)-mediated nitric oxide (NO) dysfunction, but the roles of physical properties of materials are not clear. In this study, we prepared nanobelts from P25 particles and compared their adverse effects to human umbilical vein endothelial cells (HUVECs). TiO2 nanobelts had belt-like morphology but comparable surface areas as P25 particles. When applied to HUVECs, P25 particles or nanobelts did not induce cytotoxicity, although nanobelts were much more effective to increase intracellular Ti element concentrations compared the same amounts of P25 particles. Only nanobelts significantly induced THP-1 adhesion onto HUVECs. Consistently, nanobelts were more significant to induce the expression of intracellular adhesion molecule-1 (ICAM1) and the release of soluble ICAM-1 (sICAM-1), indicating that nanobelts were more potent to induce endothelial activation in vitro. As the mechanisms for endothelial activation, both P25 and nanobelts reduced the generation of intracellular NO as well as the expression of NO regulators KLF2 and KLF4. Combined, the results from this study indicated that the different morphologies of P25 particles and nanobelts only changed their internalization into HUVECs but showed minimal impact on KLF-mediated NO signaling pathways.  相似文献   
47.
ObjectiveThe Improving Medicare Post-Acute Care Transformation Act of 2014 mandates using standardized patient functional data across post-acute settings. This study characterized similarities and differences in clinician-observed scores of self-care and transfer items for the standardized section GG functional domain and the functional independent measure (FIM) at inpatient rehabilitation facilities.DesignWe conducted secondary analyses of 2017 Uniform Data System for Medical Rehabilitation national data. Patients were assessed by clinicians on both section GG and FIM at admission and discharge. We identified 7 self-care items and 6 transfer items in section GG conceptually equivalent with FIM. Clinician-assessed scores for each pair of items were examined using score distributions, Bland-Altman plot, correlation (Pearson coefficients), and agreement (kappa and weighted kappa) analyses.Setting and ParticipantsIn all, 408,491 patients were admitted to Uniform Data System for Medical Rehabilitation-affiliated inpatient rehabilitation facilities with one of the following impairments: stroke, brain dysfunction, neurologic condition, orthopedic disorders, and debility.MeasuresSection GG and FIM.ResultsPatients were scored as more functionally independent in section GG compared with FIM, but change score distributions and score orders within impairment groups were similar. Total scores in section GG had strong positive correlations (self-care: r = 0.87 and 0.95; transfer: r = 0.82 and 0.90 at admission and discharge, respectively) with total FIM scores. Weak to moderate ranking agreements with total FIM scores were observed (self-care: kappa = 0.49 and 0.60; transfers: kappa = 0.43 and 0.52 at admission and discharge, respectively). Lower agreements were observed for less able patients at admission and for higher ability patients of their change scores.Conclusions and ImplicationsOverall, response patterns were similar in section GG and FIM across impairments. However, variations exist in score distributions and ranking agreement. Future research should examine the use of GG codes to maintain effective care, outcomes, and unbiased reimbursement across post-acute settings.  相似文献   
48.
The 43rd European Congress of Cytology in Wrocław, Poland, was held as a hybrid meeting in the Fall of 2021. After nearly 2 years without in-person cytology conferences, the 43rd Congress represents 1 of the first major international scientific meetings to occur during the severe acute respiratory syndrome-coronavirus 2 pandemic. Since March 2020, the pandemic situation substantially modified the organization of scientific meetings because of both domestic and international travel restrictions, new health standards, and concern among participants, resulting in new alternative forms of virtual conferencing. Cancer (Cancer Cytopathol) 2022;130:000-000. ;  相似文献   
49.
50.
背景 致密性骨炎(OCI)和其他疾病有时难以鉴别,探讨血清骨转换生化标志物可为OCI的鉴别诊断提供依据。 目的 探索女性OCI患者的血清骨转换生化标志物的水平变化及临床意义。 方法 回顾性选取2013年6月至2022年2月在北京积水潭医院门诊及住院诊断为OCI的61例女性患者作为观察组,年龄15~50岁,平均(33.8±6.6)岁,病程2周~15年。选择同期61例女性体检健康者作为对照组,年龄15~48岁,平均(35.6±7.6)岁。比较两组一般临床资料和血清骨转换生化标志物水平,并对血清骨转换生化标志物与病情相关指标进行相关性分析。 结果 观察组血清白蛋白(45.4±2.9)g/L低于对照组(46.5±2.8)g/L(t=2.190,P<0.05)。血清骨转换生化标志物比较结果显示,观察组血清1型胶原羧基末端肽β特殊序列(β-CTX)〔0.28(0.23,0.37)μg/L〕、N-端骨钙素(OC)〔13.1(11.2,16.2)μg/L〕、25-羟维生素D3〔25-(OH)VD3〕〔(14.1±5.1)μg/L〕低于对照组〔0.36(0.29,0.48)μg/L,15.6(13.7,17.3)μg/L,(17.5±6.6)μg/L〕(Z=-2.983、-3.255,t=3.081,P<0.05)。长病程亚组OC水平〔14.6(12.4,18.5)μg/L〕高于短病程亚组〔11.7(10.2,14.0)μg/L〕(Z=-2.407,P<0.05)。多孕亚组β-CTX〔0.25(0.22,0.32)μg/L〕、OC水平〔12.2(10.3,15.0)μg/L〕低于非多孕亚组〔0.33(0.26,0.44)μg/L、13.4(12.0,18.8)μg/L〕(Z=-2.486、-1.897,P<0.05)。相关性分析显示,观察组血清1型前胶原氨基端延长肽(tP1NP)与妊娠次数、生产次数均呈负相关(rs=-0.276、-0.298,P<0.05),OC与体质指数(BMI)、视觉模拟评分法(VAS)评分、妊娠次数均呈负相关(rs=-0.284、-0.374、-0.360,P<0.05),25-(OH)VD3水平与BMI呈正相关(rs=0.275,P<0.05)。 结论 女性OCI患者血清OC、β-CTX水平明显降低,可为鉴别其他疾病提供依据;血清OC水平可以反映OCI患者的严重程度,同时OC水平与患者妊娠次数相关;tP1NP与妊娠次数、生产次数相关。  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