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   7180篇
  免费   431篇
  国内免费   40篇
耳鼻咽喉   50篇
儿科学   391篇
妇产科学   194篇
基础医学   895篇
口腔科学   137篇
临床医学   1171篇
内科学   1151篇
皮肤病学   113篇
神经病学   561篇
特种医学   114篇
外科学   648篇
综合类   95篇
一般理论   6篇
预防医学   904篇
眼科学   214篇
药学   577篇
中国医学   13篇
肿瘤学   417篇
  2024年   20篇
  2023年   48篇
  2022年   74篇
  2021年   155篇
  2020年   105篇
  2019年   155篇
  2018年   135篇
  2017年   118篇
  2016年   115篇
  2015年   172篇
  2014年   211篇
  2013年   359篇
  2012年   445篇
  2011年   528篇
  2010年   277篇
  2009年   262篇
  2008年   460篇
  2007年   504篇
  2006年   497篇
  2005年   501篇
  2004年   459篇
  2003年   363篇
  2002年   418篇
  2001年   72篇
  2000年   47篇
  1999年   67篇
  1998年   95篇
  1997年   67篇
  1996年   54篇
  1995年   47篇
  1994年   54篇
  1993年   44篇
  1992年   38篇
  1991年   43篇
  1990年   28篇
  1989年   28篇
  1988年   26篇
  1987年   24篇
  1986年   28篇
  1985年   28篇
  1984年   34篇
  1983年   31篇
  1982年   41篇
  1981年   41篇
  1980年   43篇
  1979年   26篇
  1978年   28篇
  1975年   20篇
  1974年   24篇
  1971年   17篇
排序方式: 共有7651条查询结果,搜索用时 15 毫秒
61.
PURPOSE: To determine the effect of posterior capsular opacification (PCO) removal on anterior segment birefringence (ASB) and its influence on peripapillary retinal nerve fibre layer (RNFL) retardation measurements obtained by means of scanning laser polarimetry. METHODS: In this prospective interventional study, scanning laser polarimetry was performed using GDx variable corneal compensation on 26 eyes of 26 patients who developed clinically significant PCO (after uncomplicated cataract surgery and with no other ocular pathology) both before and between 1 and 4 weeks after Nd:YAG capsulotomy. Best-corrected visual acuity (BCVA), intraocular pressure, corneal polarization axis (CPA), corneal polarization magnitude (CPM) were compared using the Student t-test and Wilcoxon signed ranks test. Spearman correlations between changes (differences between values after and before capsulotomy) in the CPA, CPM, BCVA and RNFL data were also performed. RESULTS: PCO removal is associated with a shift in CPA (from 10.86 to 15.03 degrees, P = 0.004) and CPM (from 28.54 to 37.92 nm, P = 0.004). Significant correlations were found between changes in the parameters of ASB and BCVA. Furthermore, RNFL measurements (nerve fibre indicator, temporal-superior-nasal-inferior-temporal average and superior average) were also well related to the CPA and CPM shifts. CONCLUSIONS: PCO induces an inaccurate compensation of ASB which affects RNFL assessment. Thus, it is necessary to recompensate ASB after posterior capsulotomy.  相似文献   
62.
The purpose of this review is to highlight the advances made by epidemiologic research into cataract. Considerable progress has been made in characterizing phenotypes, determining the prevalence and incidence in various population groups, and understanding risk factors for cataract. Cataract surgery research has documented functional improvements following surgery and has identified aspects of surgery delivery that could be made. Cataract is an independent marker of early mortality, providing a possible system for studying the aging process. Promising future work in cataract epidemiology is highlighted. Despite the availability of cataract surgery, cataract is still the leading cause of blindness worldwide. From a public health standpoint, research that can identify ways to delay onset or progression, or achieve the holy grail of prevention of cataract, should remain a leading priority.  相似文献   
63.
PURPOSE: To determine the role of vision and visual attention factors in automobile crash involvement. METHODS: Drivers aged 65 to 84 years were identified during the baseline interview (1993-1995) of the Salisbury Eye Evaluation (SEE) Study. Crash involvement through December 1997 was determined from Maryland State motor vehicle records. Vision tests at baseline included distance acuity at normal and low luminance, contrast sensitivity, glare sensitivity, stereoacuity, and visual fields. Visual attention was evaluated with the Useful Field of View Test (UFOV; Visual Awareness, Chicago, IL). Survival analysis was used to determine the relative risk of a crash as a function of demographic variables, miles driven, vision, and visual attention. RESULTS: One hundred twenty (6.7%) of the 1801 drivers were involved in a crash during the observation interval. Glare sensitivity and binocular field loss were significant predictors of crash involvement (P < 0.05). For those with moderate or better vision (<3 letters for glare sensitivity and <20 points missed for binocular visual fields) increased glare sensitivity or reduced visual fields were, paradoxically, associated with a reduction in crash risk, whereas for those with poorer levels of vision, increased glare sensitivity or reduced visual fields were associated with increased crash risk. Worse UFOV score was associated with increased crash risk. CONCLUSIONS: Glare sensitivity, visual field loss, and UFOV were significant predictors of crash involvement. Acuity, contrast sensitivity, and stereoacuity were not associated with crashes. These results suggest that current vision screening for drivers' licensure, based primarily on visual acuity, may miss important aspects of visual impairment.  相似文献   
64.
The mechanism (s) by which stress exacerbates asthma is unknown. One explanation could be a reduction in endogenous serum cortisol concentrations as a result of stress. Our objective was to determine if a reduction in morning serum cortisol concentrations is associated with higher levels of stress in women with asthma. In this pilot study, seven women with a history of allergic-asthma were prospectively assigned to either low, moderate, or high stress groups based on a combination of their level of current stress and their resources to cope with the stress. After stress group assignment, women donated a morning blood sample, which was analyzed for serum cortisol concentration by an independent laboratory whose personnel were blinded to the subjects' stress status. Three women were assigned to the low stress group, two to the moderate stress group and two to the high stress group. Serum cortisol concentrations ranged from 8 to 23 microg/dl, averaging 14 +/- 6 microg/dl. A Spearman rank correlation indicated that serum cortisol concentrations were significantly inversely related to the stress groupings (r(s) = -0.915; P = 0.025). These results suggest that a reduction in morning serum cortisol concentration may be associated with higher levels of stress and lower resources to cope with the stress in women with allergic-asthma.  相似文献   
65.
66.
Background The histopathological characteristics of Chagas disease (ChD) are: presence of myocarditis, destruction of heart fibers, and myocardial fibrosis. Galectin-3 (Gal-3) is a biomarker involved in the mechanism of fibrosis and inflammation that may be useful for risk stratification of individuals with ChD.Objectives We sought to evaluate whether high Gal-3 levels are associated with severe forms of Chagas cardiomyopathy (CC) and whether they are predictive of mortality.Methods We studied anti-T. cruzi positive blood donors (BD): Non-CC-BD (187 BD without CC with normal electrocardiogram [ECG] and left ventricular ejection fraction [LVEF]); CC-Non-Dys-BD (46 BD with CC with abnormal ECG but normal LVEF); and 153 matched serum-negative controls. This cohort was composed of 97 patients with severe CC (CC-Dys). We used Kruskall-Wallis and Spearman’s correlation to test hypothesis of associations, assuming a two-tailed p<0.05 as significant.Results The Gal-3 level was 12.3 ng/mL for Non-CC-BD, 12.0 ng/mL for CC-Non-Dys-BD, 13.8 ng/mL for controls, and 15.4 ng/mL for CC-Dys. LVEF<50 was associated with higher Gal-3 levels (p=0.0001). In our linear regression adjusted model, we found association between Gal-3 levels and echocardiogram parameters in T. cruzi-seropositive subjects. In CC-Dys patients, we found a significant association of higher Gal-3 levels (≥15.3 ng/mL) and subsequent death or heart transplantation in a 5-year follow-up (Hazard ratio – HR 3.11; 95%CI 1.21–8.04; p=0.019).Conclusions In ChD patients, higher Gal-3 levels were significantly associated with severe forms of the disease and more long-term mortality, which means it may be a useful means to identify high-risk patients. (Arq Bras Cardiol. 2021; 116(2):248-256)  相似文献   
67.
68.

Objective

To examine associations between antidepressant use and health care utilization in young adults beginning maintenance hemodialysis (HD) therapy.

Patients and Methods

Antidepressant use, hospitalizations, and emergency department (ED) visits were examined in young adults (N=130; age, 18-44 years) initiating HD (from January 1, 2001, through December 31, 2013) at a midwestern US institution. Primary outcomes included hospitalizations and ED visits during the first year.

Results

Depression diagnosis was common (47; 36.2%) at HD initiation, yet only 28 patients (21.5%) in the cohort were receiving antidepressant therapy. The antidepressant use group was more likely to have diabetes mellitus (18 [64.3%] vs 33 [32.4%]), coronary artery disease (8 [28.6%] vs 12 [11.8%]), and heart failure (9 [32.1%] vs 15 [14.7%]) (P<.05 for all) than the untreated group. Overall, 68 (52.3%) had 1 or more hospitalizations and 33 (25.4%) had 1 or more ED visits in the first year. The risk of hospitalization during the first year was higher in the antidepressant use group (hazard ratio, 2.35; 95% CI, 1.39-3.96; P=.001), which persisted after adjustment for diabetes, coronary artery disease, and heart failure (hazard ratio, 1.94; 95% CI, 1.22-3.10; P=.006). Emergency department visit rates were similar between the groups.

Conclusion

Depression and antidepressant use for mood indication are common in young adult incident patients initiating HD and and are associated with higher hospitalization rates during the first year. Further research should determine whether antidepressants are a marker for other comorbidities or whether treated depression affects the increased health care use in these individuals.  相似文献   
69.
70.
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