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   1396篇
  免费   105篇
  国内免费   4篇
耳鼻咽喉   14篇
儿科学   64篇
妇产科学   51篇
基础医学   147篇
口腔科学   21篇
临床医学   116篇
内科学   358篇
皮肤病学   15篇
神经病学   198篇
特种医学   37篇
外科学   202篇
综合类   13篇
一般理论   2篇
预防医学   116篇
眼科学   38篇
药学   41篇
肿瘤学   72篇
  2023年   16篇
  2022年   24篇
  2021年   71篇
  2020年   32篇
  2019年   60篇
  2018年   58篇
  2017年   34篇
  2016年   54篇
  2015年   58篇
  2014年   60篇
  2013年   63篇
  2012年   102篇
  2011年   88篇
  2010年   60篇
  2009年   65篇
  2008年   85篇
  2007年   83篇
  2006年   79篇
  2005年   54篇
  2004年   57篇
  2003年   46篇
  2002年   38篇
  2001年   16篇
  2000年   11篇
  1999年   10篇
  1998年   5篇
  1997年   5篇
  1995年   5篇
  1994年   6篇
  1992年   7篇
  1991年   6篇
  1990年   14篇
  1989年   9篇
  1988年   5篇
  1987年   6篇
  1986年   8篇
  1985年   9篇
  1984年   8篇
  1983年   7篇
  1982年   6篇
  1981年   6篇
  1980年   6篇
  1979年   6篇
  1978年   8篇
  1976年   4篇
  1975年   4篇
  1974年   9篇
  1973年   5篇
  1969年   5篇
  1967年   4篇
排序方式: 共有1505条查询结果,搜索用时 15 毫秒
31.
Objective: Controversy exists concerning the impact of amniotic fluid index (AFI) on the accuracy of sonographic estimation of fetal weight (EFW). Thus, we aimed to evaluate whether differences in AFI has an influence on the accuracy of sonographic EFW.

Methods: All term, singleton pregnancies which underwent a sonographic EFW and measurement of AFI within a week from delivery were included. Cases were stratified into three categories according to AFI: (1) Normal AFI (51–249?mm), (2) Oligohydramnios (AFI?≤?50?mm) and (3) Polyhydramnios (AFI?≥?250?mm). Inaccurate EFW was defined if there was more than 15% difference between sonographic EFW and actual birthweight.

Results: Overall, 1746 pregnancies were identified (1096 with normal AFI, 455 with oligohydramnios and 195 with polyhydramnios). Mean AFI was 115.8?±?60?mm, 28.1?±?13?mm and 293?±?35?mm, p?<?0.001, and mean sonographic EFW was 3182.5?±?573?g, 3118.8?±?517?g and 3713.2?±?461?g, p?<?0.001, respectively. Demographic data and gestational age at delivery were similar. Mean birthweight was 3221.7?±?535?g, 3132.5?±?505?g and 3654.1?±?480?g, p?<?0.001, respectively. The rate of inaccurate EFW was similar between the groups (8.4%, 8.7% and 9.7%, p?=?0.19, respectively). On multivariate analysis, AFI was not associated with EFW inaccuracy (OR 1.01, 95% C.I 0.67–1.54, p?=?0.93).

Conclusion: AFI has limited impact on the percentage of errors in sonographic fetal weight estimation a week prior delivery.  相似文献   

32.
The demand for Long-Term Care (LTC) is steadily increasing as Baby Boomers age and enter retirement. High turnover rates among employees in LTC creates challenges for supervisors and administrators, and can negatively impact quality of care. This study examines manager-subordinate relationship quality using Leader-Member Exchange Theory (LMX) as an antecedent to turnover among low-wage earners in the LTC environment. Survey data measuring LMX, job satisfaction, and demographic information was collected at time 1, and turnover data was collected 18 months later at time 2. The results reveal that all four LMX dimensions were rated significantly different among subordinates who left versus those who stayed, however, only the LMX dimension of supervisor loyalty was a significant predictor of turnover among low wage earners. Our study adds a more nuanced view of the reasons low-wage employees turnover, and presents implications for clinical managers and LTC organizations more broadly.  相似文献   
33.
Journal of Thrombosis and Thrombolysis - Managing anticoagulation in hematological malignancy patients with atrial fibrillation and thrombocytopenia is a clinical challenge with limited data. We...  相似文献   
34.

Background

The Heartmate 3 (HM3) is a Conformiteé Européenne mark–approved left ventricular (LV) assist device (LVAD) with fully magnetically levitated rotor and features consisting of a wide range operational speeds, wide flow paths, and artificial pulse. We performed a hemodynamic-echocardiographic speed optimization evaluation in HM3-implanted patients to achieve optimal LV- and right ventricular (RV) shape.

Methods and Results

Sixteen HM3 patients underwent pump speed ramp tests with right heart catheterization. Three-dimensional echocardiographic (3DE) LV and RV datasets (Philips) were acquired, and volumetric (Tomtec) and shape (custom software) analyses were performed (LV: sphericity, conicity; RV: septal and free-wall curvatures). Data were recorded at up to 13 speed settings. Speed changes were in 100-rpm steps, starting at 4600 rpm and ramping up to 6200 rpm. 3DE was feasible in 50% of the patients. Mean original speed was 5306 ± 148 rpm. LV end-diastolic (ED) diameter (?0.15 ± 0.09 cm/100 rpm) and volumes (ED: 269 ± 109 mL to 175 ± 90 mL; end-systolic [ES]: 234 ± 111 mL to 146 ± 81 mL) progressively decreased as the shape became less spherical and more conical; RV volumes initially remained stable, but at higher speeds increased (ED: from 148 ± 64 mL to 181 ± 92 mL; ES: 113 ± 63 mL to 130 ± 69 mL). On average, the RV septum became less convex (bulging toward the LV) at the highest speeds.

Conclusions

LV and RV shape changes were noted in HM3-supported patients. Although a LV volumetric decrease and shape improvement was consistently noted, RV volumes grew in response to increase in speed above a certain point. A next concern would be whether understanding of morphologic and function changes in LV and RV during LVAD speed change assessed with the use of 3DE helps to optimize LVAD speed settings and improve clinical outcomes.  相似文献   
35.
We compared clinical, microbiological, and prognostic characteristics of infective endocarditis in patients with and without diabetes mellitus. In 1987--1996, 213 patients with definite or possible infective endocarditis were included, of which 39 (18%) had diabetes mellitus. Diabetic patients were older than non-diabetic (median age of 71 vs 65 y, respectively; p =0.04), had more aortic valve and less mitral valve involvement (71% vs 27%, and 21% vs 62%; p = 0.004). There was no significant difference in the frequency of Staphylococcus aureus involvement between the 2 groups (21% in diabetic vs 20% in non-diabetic group; p = ns). On multivariate analysis diabetes mellitus was not found to be an independent factor for mortality. Unlike other infections diabetes mellitus does not significantly affect clinical and microbiological features, and outcome of infective endocarditis.  相似文献   
36.
Leukapheresis of neutrophil granulocytes in mice increased the myelopoietic activity of their serum. Leukapheresed mouse serum (LMS) caused a threefold increase in the in vitro stathmokinetic index of myeloid precursors. Five to ten minutes of incubation were sufficient to change the colony-forming capacity of mouse bone marrow cells as expressed by the increase in the ratio of granuloid to erythroid cells in spleen colonies. The in vitro stathmokinetic index assay also showed that there are diurnal variations in levels of granulopoietic activity in normal mouse sera. However, at any time of the day, LMS had higher granulopoietic activity.  相似文献   
37.
38.
Despite evidence of a substantial genetic component, the genetic factors that underlie longevity in humans remain to be identified. Previous genome-wide linkage and association studies have not found strong evidence for the contribution of common variants besides the APOE gene, suggesting the role of rare variants in human longevity. To discover rare variants that might contribute to longevity, we selected 988 candidate genes and performed a pilot study to identify novel non-synonymous variants in 6 Ashkenazi Jewish centenarians older than 105. Our candidate genes act in pathways implicated in aging and longevity, including neurodegeneration, cognitive function, lipid metabolism, DNA repair, and genome maintenance. By implementing custom-designed Agilent SureSelect target capture and next-generation sequencing, we discovered a total of 89 novel non-synonymous SNPs (nsSNPs) and validated 51 nsSNPs by iPLEX MassArray assays. Genotyping analysis of these novel SNPs in 410 Ashkenazi Jewish controls and 390 centenarians showed significant enrichment (5.3 fold, = 0.02) of the p.Y318C variant in PMS2 and significant depletion (7.5 fold, = 0.04) of the p.V465A variant in GABRR3 in centenarians compared to controls. Our study presents the potential of targeted next-generation sequencing for discovery of rare but functional genetic variation which may lead to exceptional longevity in humans.  相似文献   
39.
Possti  Daniel  Fahoum  Firas  Sosnik  Ronen  Giladi  Nir  Hausdorff  Jeffrey M.  Mirelman  Anat  Maidan  Inbal 《Journal of neurology》2021,268(1):161-168
Journal of Neurology - The ability to maintain adequate motor-cognitive performance under increasing task demands depends on the regulation and coordination of neural resources. Studies have shown...  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