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   249388篇
  免费   19669篇
  国内免费   7285篇
耳鼻咽喉   1804篇
儿科学   9393篇
妇产科学   2380篇
基础医学   22836篇
口腔科学   4456篇
临床医学   25870篇
内科学   60348篇
皮肤病学   3328篇
神经病学   29081篇
特种医学   6994篇
外国民族医学   12篇
外科学   20472篇
综合类   31954篇
现状与发展   33篇
一般理论   11篇
预防医学   19630篇
眼科学   3206篇
药学   17775篇
  192篇
中国医学   11219篇
肿瘤学   5348篇
  2024年   232篇
  2023年   4841篇
  2022年   6536篇
  2021年   12218篇
  2020年   12180篇
  2019年   10587篇
  2018年   10313篇
  2017年   9525篇
  2016年   9451篇
  2015年   9295篇
  2014年   17913篇
  2013年   20071篇
  2012年   14715篇
  2011年   16138篇
  2010年   12406篇
  2009年   11833篇
  2008年   11765篇
  2007年   11085篇
  2006年   9740篇
  2005年   8139篇
  2004年   7010篇
  2003年   6029篇
  2002年   5024篇
  2001年   4372篇
  2000年   3727篇
  1999年   3040篇
  1998年   2622篇
  1997年   2279篇
  1996年   1987篇
  1995年   2092篇
  1994年   1942篇
  1993年   1642篇
  1992年   1533篇
  1991年   1386篇
  1990年   1108篇
  1989年   941篇
  1988年   877篇
  1987年   799篇
  1986年   684篇
  1985年   1266篇
  1984年   1231篇
  1983年   813篇
  1982年   941篇
  1981年   797篇
  1980年   636篇
  1979年   573篇
  1978年   469篇
  1977年   381篇
  1976年   347篇
  1975年   275篇
排序方式: 共有10000条查询结果,搜索用时 19 毫秒
41.
42.
Circadian rhythms are 24-hour natural rhythms regulated by the suprachiasmatic nucleus, also known as the "master clock". The retino-hypothalamic tract entrains suprachiasmatic nucleus with photic information to synchronise endogenous circadian rhythms with the Earth’s light-dark cycle. However, despite the robustness of circadian rhythms, an unhealthy lifestyle and chronic photic disturbances cause circadian rhythm disruption in the suprachiasmatic nucleus’s TTFL loops via affecting glutamate and γ-aminobutyric acid-mediated neurotransmission in the suprachiasmatic nucleus. Recently, considerable evidence has been shown correlating CRd with the incidence of Alzheimer's disease. The present review aims to identify the existence and signalling of endocannabinoids in CRd induced Alzheimer's disease through retino-hypothalamic tract- suprachiasmatic nucleus-cortex. Immunohistochemistry has confirmed the expression of cannabinoid receptor 1 in the suprachiasmatic nucleus to modulate the circadian phases of the master clock. Literature also suggests that cannabinoids may alter activity of suprachiasmatic nucleus by influencing the activity of their major neurotransmitter γ-aminobutyric acid or by interacting indirectly with the suprachiasmatic nucleus’s two other major inputs i.e., the geniculo-hypothalamic tract-mediated release of neuropeptide Y and serotonergic inputs from the dorsal raphe nuclei. Besides, the expression of cannabinoid receptor 2 ameliorates cognitive deficits via reduction of tauopathy and microglial activation. In conclusion, endocannabinoids may be identified as a putative target for correcting CRd and decelerating Alzheimer’s disease.  相似文献   
43.
BackgroundRecent studies have described the use of telehealth for pediatric surgical care during the COVID-19 pandemic. We aimed to evaluate equity in telehealth use by comparing rates of utilization and satisfaction with pediatric surgical telemedicine among Hispanic patients.MethodsWe conducted a retrospective cohort study of patients seen by a surgical subspecialty provider in the outpatient setting at a quaternary pediatric hospital between April 1 and June 30, 2020. Patients evaluated in the same three-month period in 2019 were analyzed as a historic control. Differences in Family Experience Survey (FES) responses based on race and ethnicity and preferred language of care were assessed using univariable and multivariable generalized linear modeling.ResultsThe pandemic cohort included fewer patients of Hispanic ethnicity and fewer Spanish-speakers. After controlling for visit type, comparison of Spanish-speaking and English-speaking patients revealed that Spanish-speaking families had significantly lower scores for FES items that evaluated healthcare provider explaining (IRR 0.74, 95% CI: 0.61–0.90), listening (IRR 0.76, 95% CI: 0.63–0.92), and time spent with the family (IRR 0.73, 95% CI: 0.60–0.89). There were no differences in FES responses based on insurance status or degree of medical complexity.ConclusionsTelehealth services were less commonly used among Hispanic and Spanish-speaking patients. Language may differentially affect family satisfaction with healthcare and telehealth solutions. Strategies to mitigate these inequities are needed and may include strengthening interpreter services and providing language-concordant care.Level of evidenceLevel IV.  相似文献   
44.
IntroductionThe risk of mortality in patients with COVID-19 was found to be significantly higher in patients who experienced thromboembolic events. Thus, several guidelines recommend using prophylactic anticoagulants in all COVID-19 hospitalized patients. However, there is uncertainty about the appropriate dosing regimen and safety of anticoagulation in critically ill patients with COVID-19. Thus, this study aims to compare the effectiveness and safety of standard versus escalated dose pharmacological venous thromboembolism (VTE) prophylaxis in critically ill patients with COVID-19.MethodsA two-center retrospective cohort study including critically ill patients aged ≥ 18-years with confirmed COVID-19 admitted to the intensive care unit (ICU) at two tertiary hospitals in Saudi Arabia from March 1st, 2020, until January 31st, 2021. Patients who received either Enoxaparin 40 mg daily or Unfractionated heparin 5000 Units three times daily were grouped under the “standard dose VTE prophylaxis and patients who received higher than the standard dose but not as treatment dose were grouped under ”escalated VTE prophylaxis dose“. The primary outcome was the occurance of thrombotic events, and the secondary outcomes were bleeding, mortality, and other ICU-related complications.ResultsA total of 758 patients were screened; 565 patients were included in the study. We matched 352 patients using propensity score matching (1:1). In patients who received escalated dose pharmacological VTE prophylaxis, any case of thrombosis and VTE were similar between the two groups (OR 1.22;95 %CI 0.52–2.86; P = 0.64 and OR 0.75; 95% CI 0.16–3.38; P = 0.70 respectively). However, the odds of minor bleeding was higher in patients who received escalated VTE prophylaxis dose (OR 3.39; 95% CI 1.08–10.61; P = 0.04). There was no difference in the 30-day mortality nor in-hospital mortality between the two groups (HR 1.17;95 %CI0.79–1.73; P = 0.43 and HR 1.08;95 %CI 0.76–1.53; P = 0.83, respectively).ConclusionEscalated-dose pharmacological VTE prophylaxis in critically ill patients with COVID-19 was not associated with thrombosis, or mortality benefits but led to an increased risk of minor bleeding. This study supports previous evidence regarding the optimal dosing VTE pharmacological prophylaxis regimen for critically ill patients with COVID-19.  相似文献   
45.
46.
47.
ObjectivesPreclinical and clinical studies indicate a role for MLC901 (NeuroAiD II) in Alzheimer's disease (AD). The primary aim was to investigate its safety as add-on therapy to standard treatment and the secondary aims its effect on cognition and slowing disease progression.DesignRandomized double-blind placebo-controlled delayed-start study.Setting and ParticipantPatients with mild to moderate probable AD by NINCDS-ADRDA criteria, stable on acetylcholinesterase inhibitors or memantine (n = 125), were randomized to receive MLC901 (early starters) or placebo (delayed starters) for 6 months, followed by a further 6 months when all patients received MLC901, in a delayed-start design (clinical trial registration: ClinicalTrials.gov, NCT03038035).MethodsThe primary outcome measure was occurrence of serious adverse events (SAEs) at 6 months. Secondary outcomes included the Alzheimer's Disease Assessment Scale–Cognitive subscale (ADAS-Cog) and other assessment scales.ResultsThere was no significant difference in the risk of SAEs between early and delayed starters at month (M) 6 (22.6% vs 27.0%, risk difference ?4.4%, 90% CI –16.9% to 8.3%). Similarly, there was no significant difference in the risk of adverse events and the occurrence of stroke or vascular events between early and delayed starters throughout the 12-month study period. Early starters did not differ significantly on ADAS-Cog from delayed starters at M6 [mean difference (MD) ?1.0, 95% CI –3.3 to 1.3] and M12 (MD –2.35, 95% CI –5.45 to 0.74) on intention-to-treat analysis. Other cognitive assessment scales did not show significant differences.Conclusions and ImplicationsThis study of 125 persons with dementia found no evidence of a significant increase in adverse events between MLC901 and placebo, thus providing support for further studies on both efficacy and safety. Analyses suggest the potential of MLC901 in slowing down AD progression, but this requires further confirmation in larger and longer studies using biomarkers for AD.  相似文献   
48.
ObjectivePrevious epidemiologic studies have suggested an association between appendectomy and Parkinson's disease. The aim of the current study was to examine the risk of Alzheimer's disease (AD) and other types of dementia following appendicitis or appendectomy for appendicitis.DesignPopulation-based cohort study.Setting and participantsWe used claims data from the Taiwan National Health Insurance Research Database. Participants aged ≥45 years with acute appendicitis or who received appendectomy for appendicitis were enrolled and followed up for more than 15 years. Cases and controls underwent 1:1 matching by age, sex, index date, and dementia-related comorbidities.MethodsThe primary outcome was AD, and secondary outcomes included other dementia types. Adjusted hazard ratios (aHRs) were calculated, and a competing risk regression model was created. The E value for causality of evidence was calculated.ResultsPatients developing appendicitis (0.6% vs 0.1%, P = .005) and those receiving appendectomy for appendicitis (0.4% vs 0.1%, P = .003) had higher incidences of AD than the controls during the follow-up period. A Cox regression analysis with adjustment for potential confounders showed that patients with appendicitis [aHR 6.68, 95% confidence interval (CI) 1.84-24.48] and those receiving appendectomy for appendicitis (aHR 5.01, 95% CI 1.33-18.85) were more likely to develop AD than the controls. These 2 groups also had higher risks for unspecified dementia and all types of dementia but not for vascular dementia than the controls. The age at dementia diagnosis was 88.51 years in the controls; however, among people who developed dementia following appendicitis, the mean age at diagnosis was 70.18 years, and dementia occurred 5.84 years after appendicitis. The competing risk regression models and the E values support the study findings.Conclusions and implicationsAfter recovery from appendicitis, these patients should be followed up for signs of AD.  相似文献   
49.
BackgroundExplosion fatalities are the severest type of violent crimes. These involve the use of explosive devices in terrorist like activities in confined spaces in civilian or military settings, with mass number of people present all around. A stark dearth of literature for the forensic interpretation of such catastrophes is astonishing.PurposeCharacterization of the pattern of the multitude of injuries in explosions in confined spaces as guide for investigations and growth of literature on this entity.MethodologyA review of the archives of the forensic examinations of mass fatalities due to an explosion in a metro car was undertaken. It was combined with the reconstruction of the events by developing a three-dimensional model of this incident that involved seventeen fatalities.ResultsAll the decedents showed differential pattern of fatal injuries under the influence of damaging explosion factors (DEFs). The causative forces were characterized as gas-detonation (in all the cases), damaging effect by shock waves (59% of the cases), and impact of fragmentation and collision of the body (thrown off) with nearby objects. Traumatic effect due to shrapnel as well as blunt force was noted in 82% of the cases. Gross destruction of head due to combined effect of gas-detonation and fragmentation was seen in 29% of the cases.ConclusionAn interpretation of the nature and pattern of injuries in confined space explosions can help to estimate the location of deceased/s with respect to the epicenter and the type of DEFs.  相似文献   
50.
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