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   3253986篇
  免费   218209篇
  国内免费   4922篇
耳鼻咽喉   45875篇
儿科学   106752篇
妇产科学   86918篇
基础医学   469353篇
口腔科学   88580篇
临床医学   292371篇
内科学   627519篇
皮肤病学   70989篇
神经病学   258196篇
特种医学   123017篇
外国民族医学   1100篇
外科学   487909篇
综合类   68185篇
现状与发展   12篇
一般理论   1181篇
预防医学   253052篇
眼科学   75421篇
药学   240474篇
  78篇
中国医学   6220篇
肿瘤学   173915篇
  2021年   25963篇
  2019年   27397篇
  2018年   36638篇
  2017年   27569篇
  2016年   31000篇
  2015年   34834篇
  2014年   48861篇
  2013年   73441篇
  2012年   101513篇
  2011年   107812篇
  2010年   64381篇
  2009年   60776篇
  2008年   101425篇
  2007年   108303篇
  2006年   108952篇
  2005年   105638篇
  2004年   101648篇
  2003年   97792篇
  2002年   95270篇
  2001年   145738篇
  2000年   149878篇
  1999年   126978篇
  1998年   37371篇
  1997年   32876篇
  1996年   33112篇
  1995年   31422篇
  1994年   29171篇
  1993年   27255篇
  1992年   99128篇
  1991年   97111篇
  1990年   94479篇
  1989年   90692篇
  1988年   83497篇
  1987年   82230篇
  1986年   76900篇
  1985年   74055篇
  1984年   55425篇
  1983年   47068篇
  1982年   28055篇
  1979年   50696篇
  1978年   35986篇
  1977年   30237篇
  1976年   28667篇
  1975年   30978篇
  1974年   36710篇
  1973年   35133篇
  1972年   32737篇
  1971年   30638篇
  1970年   28576篇
  1969年   26898篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
<正>Norepinephrine (NE; also known as noradrenaline) is the body's primary adrenergic neurotransmitter which belongs to the catecholamine family. Norepinephrine has pharmacologic effects on theα1 (Suita et al.,2015),α2 (Schwartz,1997),β1,β2 andβ3(Tsukada et al., 2003) adrenoceptors. In the brain, norepinephrine increases arousal and alertness, promotes vigilance, enhances formation and retrieval of memory, and focuses attention. It also increases restlessness and anxiety. In the remainder of the body,  相似文献   
32.
33.
34.

Background

We hypothesized that trends in total bilirubin in the context of cholecystitis and symptomatic cholelithiasis could be used to guide testing for the presence of common bile duct stones (CBDS).

Methods

A review of adult patients with acute cholecystitis or biliary colic with elevated total bilirubin and at least two levels drawn prior to procedural intervention was performed. Trends of total bilirubin and other serum makers were examined to predict the presence of CBDS.

Results

The total bilirubin level at presentation, average over 24?h and average over 48?h (3.74?mg/dl vs. 2.29?mg/dl, p?=?0.005; 3.72?mg/dl vs. 2.40?mg/dl, p?=?0.009; 2.41?mg/dl vs. 1.47?mg/dl, p?<?0.001) respectively, were all higher in those with CBDS. However, prediction was not improved by following levels over time.

Conclusion

Patients presenting with elevated serum bilirubin, should undergo immediate imaging or procedural intervention rather than obtaining follow-up bilirubin levels.  相似文献   
35.

Background and aims

There is controversy on the potentially benign nature of metabolically healthy obesity (MHO), i.e., obese persons with few or no metabolic abnormalities. So far, associations between MHO and coronary artery calcification (CAC), a measure of subclinical atherosclerosis, have mainly been studied cross-sectionally in Asian populations. We assessed cross-sectional and longitudinal MHO CAC associations in a Caucasian population.

Methods and results

In the Heinz Nixdorf Recall Study, a population-based cohort study in Germany, CAC was assessed by electron-beam tomography at baseline and at 5-year follow-up. For cross-sectional and longitudinal analyses, we included 1585 participants free of coronary heart disease at baseline, with CAC measurements at baseline and at follow-up, and with either normal weight (BMI 18.5–24.9 kg/m2) or obesity (BMI ≥30.0 kg/m2) at baseline. We used four definitions of MHO. In our main analysis, we defined obese persons as metabolically healthy if they met ≤1 of the NCEP ATP III criteria for the definition of the metabolic syndrome – waist circumference was not taken into account because of collinearity with BMI.Persons with MHO had a higher prevalence of CAC than metabolically healthy normal weight (MHNW) persons (prevalence ratio = 1.59 (95% confidence interval 1.38–1.84) for the main analysis). Persons with MHO had slightly larger odds of CAC progression than persons with MHNW (odds ratios ranged from 1.17 (0.69–1.99) to 1.48 (1.02–2.13) depending on MHO definition and statistical approach).

Conclusion

Our analyses on MHO CAC associations add to the evidence that MHO is not a purely benign health condition.  相似文献   
36.
37.

Objectives

To analyze the factors associated with fatigue focusing on comorbidities in a large cohort of rheumatoid arthritis (RA).

Methods

Cross-sectional analyses were performed on RA patients from the French COMEDRA cohort study, a nurse-led program for comorbidities management. Fatigue was assessed using Question 3 of the Rheumatoid Arthritis Impact of Disease (RAID) score on a 0–10 numerical rating scale (NRS). Fatigue was defined as acceptable if?≤?2, moderate if 3 or 4, or severe if?≥?5 out of 10. Using univariate and multivariate models, the relationship between fatigue and demographics, social, disease characteristics, comorbidities (cardiovascular, infections, cancer, pulmonary, osteoporosis, and psychiatric disorders), physical activity, quality of life, and treatments was investigated.

Results

In total, 962 patients were analyzed. The mean fatigue score was 3.8?±?2.7, 40% of patients reported severe fatigue. Patients had an average of 1.8 additional morbid conditions, with anxiety/depression the most common (52%). In univariate analysis, severe fatigue was more frequent in women, in patients not working, and in those with less physical activity. It was associated with disease duration and activity, mHAQ, pain, sleeping and emotional difficulties. Severe fatigue correlated with Multimorbidity index assessing the number of morbid conditions and was associated with obesity, hypertension, COPD, and anxiety/depression. In multivariate models, the risk of severe fatigue was associated with female gender, disease activity, mHAQ, current treatment with NSAIDs and biologics, multimorbidity, obesity and anxiety/depression.

Conclusions

Assessment of comorbidities, psychological health and physical activity should be taken into account in order to address frequent RA-related severe fatigue.  相似文献   
38.

Background

Pulmonary hypertension (PH) is a comorbidity associated with interstitial lung disease (ILD). The purpose of this study was to evaluate the influence of PH on intrahospital mortality in lung transplantation (LT) for ILD.

Methods

We conducted a retrospective cohort study of 66 patients who underwent LT for ILD at the 12 de Octubre University Hospital (Madrid, Spain) from October 2008 to June 2014. PH was defined as mean pulmonary arterial pressure (mPAP) ≥25 mmHg on right-sided heart catheterization and intrahospital mortality as any death taken place after the transplantation of patients not being discharged.

Results

We retrospectively analyzed data of 66 patients; they were stratified by the presence or absence of PH before LT. Twenty-seven patients (41%) had PH. The PH group had a lower diffusing capacity of carbon monoxide (DLCO), carbon monoxide transfer coefficient (KCO), and 6-minute walk distance test (6MWT) and a higher total lung capacity (TLC), modified medical research council dyspnea scale (mMRC), and lung allocation score (LAS) than the non-PH group. Patients with PH more often underwent double lung transplantation (DLT; 59%) than single lung transplantation (SLT).Intrahospital mortality was 13% (9/66). No significant differences were observed in Kaplan-Meier survival curves for the PH and non-PH groups with a median survival time of 46 days versus 33 days (IQR 26–74; log-rank P = .056); however, the postoperative length of stay in the hospital was greater in the PH group.

Conclusions

In our cohort, pulmonary hypertension was not related to early mortality in lung transplantation recipients for interstitial lung diseases.  相似文献   
39.

Background and purpose

The vein of Galen aneurysmal malformation (VGAM) is a rare congenital vascular malformation with a higher morbidity and mortality, especially in neonates. Ultrasound, CT and MR are usually used in diagnosis and treatment monitoring of these disorders. In this current study, we aim to examine utility of SWI in evaluation of treatment response in infants with VGAM.

Materials and methods

We performed a retrospective chart analysis of children with VGAM in our institution between January 2008 and December 2016. Inclusion criteria included; confirmed VGAM on DSA; available SWI sequence at baseline and at follow up after at least a single embolization session; age at initial MR of 18?years or younger. Signal intensity and Angioarchitecture of VGAM and cerebral veins on SWI, as well as hydrocephalus and clinical outcome were evaluated.

Results

Of 11 patients identified with VGAM in our institution, 5 children (3 males and 2 females) satisfied the inclusion criteria. The average age at initial MR was 29?days (range 1–120). Fourteen MRI were available for review. All children had VGAM of mural type. Intramedullary veins were dilated and SWI-hypointense in all children, while subependymal and sulcal veins were dilated and SWI-hypointense in 4 patients on initial MRI. On the first available follow up MRI, cerebral veins have mostly normalized in 4 children and remained mostly dilated and SWI-hypointense in 1 child; even after complete treatment of the VGAM.

Conclusion

Our preliminary findings show that SWI seems to offer a beneficial non-invasive tool in evaluating passive venous congestion patterns in pediatric patients with VGAM. It remains to be determined in larger studies, the clinical significance of these SWI changes.  相似文献   
40.
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