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   1744篇
  免费   223篇
  国内免费   16篇
耳鼻咽喉   15篇
儿科学   107篇
妇产科学   35篇
基础医学   219篇
口腔科学   66篇
临床医学   196篇
内科学   467篇
皮肤病学   36篇
神经病学   132篇
特种医学   66篇
外科学   219篇
综合类   31篇
一般理论   1篇
预防医学   132篇
眼科学   38篇
药学   94篇
中国医学   9篇
肿瘤学   120篇
  2023年   13篇
  2022年   25篇
  2021年   63篇
  2020年   29篇
  2019年   41篇
  2018年   114篇
  2017年   115篇
  2016年   91篇
  2015年   79篇
  2014年   78篇
  2013年   90篇
  2012年   109篇
  2011年   89篇
  2010年   75篇
  2009年   76篇
  2008年   64篇
  2007年   92篇
  2006年   83篇
  2005年   80篇
  2004年   58篇
  2003年   61篇
  2002年   58篇
  2001年   32篇
  2000年   36篇
  1999年   37篇
  1998年   26篇
  1997年   37篇
  1996年   32篇
  1995年   15篇
  1994年   22篇
  1993年   18篇
  1992年   14篇
  1991年   11篇
  1990年   9篇
  1989年   12篇
  1988年   13篇
  1987年   3篇
  1986年   3篇
  1985年   7篇
  1979年   4篇
  1976年   3篇
  1975年   6篇
  1972年   4篇
  1971年   4篇
  1969年   3篇
  1968年   3篇
  1963年   4篇
  1943年   2篇
  1939年   2篇
  1938年   2篇
排序方式: 共有1983条查询结果,搜索用时 15 毫秒
1.
Prevalence of osteoporosis is more than 50% in older adults, yet current clinical methods for diagnosis that rely on areal bone mineral density (aBMD) fail to detect most individuals who have a fragility fracture. Bone fragility can manifest in different forms, and a “one-size-fits-all” approach to diagnosis and management of osteoporosis may not be suitable. High-resolution peripheral quantitative computed tomography (HR-pQCT) provides additive information by capturing information about volumetric density and microarchitecture, but interpretation is challenging because of the complex interactions between the numerous properties measured. In this study, we propose that there are common combinations of bone properties, referred to as phenotypes, that are predisposed to different levels of fracture risk. Using HR-pQCT data from a multinational cohort (n = 5873, 71% female) between 40 and 96 years of age, we employed fuzzy c-means clustering, an unsupervised machine-learning method, to identify phenotypes of bone microarchitecture. Three clusters were identified, and using partial correlation analysis of HR-pQCT parameters, we characterized the clusters as low density, low volume, and healthy bone phenotypes. Most males were associated with the healthy bone phenotype, whereas females were more often associated with the low volume or low density bone phenotypes. Each phenotype had a significantly different cumulative hazard of major osteoporotic fracture (MOF) and of any incident osteoporotic fracture (p < 0.05). After adjustment for covariates (cohort, sex, and age), the low density followed by the low volume phenotype had the highest association with MOF (hazard ratio = 2.96 and 2.35, respectively), and significant associations were maintained when additionally adjusted for femoral neck aBMD (hazard ratio = 1.69 and 1.90, respectively). Further, within each phenotype, different imaging biomarkers of fracture were identified. These findings suggest that osteoporotic fracture risk is associated with bone phenotypes that capture key features of bone deterioration that are not distinguishable by aBMD. © 2021 American Society for Bone and Mineral Research (ASBMR).  相似文献   
2.

Objective

To systematically review literature on uptake and timeliness of diphtheria-tetanus-pertussis, measles-mumps-rubella, and/or polio-containing vaccines in infants who were born preterm, with a low birth weight, and/or with chronic health conditions that were diagnosed within the first 6?months of life.

Methods

Using a standardized search strategy developed by a medical librarian, records were extracted from MEDLINE, Embase, Database of Abstracts of Reviews of Effects, and CINAHL up to May 8, 2018.

Results

Out of the 1997 records that were screened, we identified 21 studies that met inclusion criteria. Eleven studies assessed vaccine coverage and/or timeliness in preterm infants, 6 in low birth weight infants, and 7 in children with chronic health conditions. Estimates of coverage in these populations were highly variable, ranging from 40% to 100% across the vaccines and population groups.

Conclusions

There is a lack of studies reporting coverage and timeliness of routine immunizations in special populations of children.

Policy implications

Our review suggests a need for improved surveillance of immunization status in special populations of infants, as well as a need for standardization of reporting practices.  相似文献   
3.
Background: Large randomized trials show that in appropriately selected patients with left ventricular dysfunction, implantable cardioverter-defibrillators (ICDs) can improve overall survival at 2–5 years. Since direct implementation of the criteria used in the MADIT II and SCD-HeFT will lead to a marked rise in ICD implants, there is a growing fear that increased use of ICDs may cause a dramatic burden to health care systems. The ICD has traditionally been seen as an expensive form of treatment, which is difficult to accept at the first look. This is mainly due to the nonlinear character of the ICD investment, characterized by high initial expenditure, followed by a deferred pay-off in terms of clinical benefits. Cost-effectiveness analysis may help provide a different perspective on the problem of ICD cost, as may estimation of the daily cost of ICD treatment, assuming a time horizon of 5–7 years—a particularly interesting subject for further registry studies.
Methods and Results: Based on real expenditure data from 2002 to 2005, as recorded in the Search-MI Registry-Italian Sub-study of patients implanted on MADIT II indications, we estimated the daily costs associated with the device and leads. Over a 5–7 year time horizon, the average daily cost was estimated to be €4.60–€6.70. Translation of these figures into U.S. market conditions suggests a daily cost of around $7.90–$11.40.
Conclusions: These findings appear useful to help evaluate the affordability of ICD in comparison with other therapeutic options in a context of limited available economic resources.  相似文献   
4.
Vascular 18F-FDG uptake marker represents inflammation in atherosclerotic lesions, but whether inflammation can be reversed by risk-modifying interventions has not, to our knowledge, been demonstrated. In this study, we evaluated the change of vascular 18F-FDG uptake in response to lifestyle intervention on serial PET/CT scans and further assessed how the findings relate to atherogenic risk reduction. METHODS: A total of 60 healthy adults underwent 18F-FDG PET/CT scans and atherogenic risk-factor assessment at baseline and again after 17.1 +/- 8.3 mo of practicing lifestyle modification. The PET/CT images were evaluated for the presence of vascular 18F-FDG lesions, and vessel-to-blood-pool 18F-FDG ratios were measured. Indices from summed ratios of positive lesions were compared and correlated to atherogenic risk factors. RESULTS: At follow-up, significant reductions in diastolic blood pressure (P < 0.05), total cholesterol (P < 0.05), and low-density lipoprotein level (P < 0.05) and an increase in high-density lipoprotein (HDL) level (P < 0.0001) were demonstrated. On the initial PET/CT scan, 50 of 60 subjects showed 1 or more 18F-FDG-positive lesions (5.9 +/- 5.0/subject), leading to a total of 352 vascular sites. On follow-up, 18F-FDG-positive lesions were significantly reduced to 2.1 +/- 2.2 sites per subject (P < 0.0001) and a total of 124 sites (64.8% reduction). Follow-up 18F-FDG-positive rates were significantly reduced for the aorta and iliac arteries. In addition, significant reductions in the whole-body 18F-FDG index from 1.39 +/- 1.23 to 0.53 +/- 0.59 (P < 0.0001) and carotid 18F-FDG index from 0.08 +/- 0.16 to 0.03 +/- 0.06 (P = 0.01) were shown. The whole-body 18F-FDG index correlated with total cholesterol (P < 0.05) and HDL level (P < 0.05), and the magnitude of reduction in the 18F-FDG index closely correlated to the amount of increase in plasma HDL level (P = 0.005). CONCLUSION: Our study demonstrated that vascular 18F-FDG uptake is reversed in response to atherogenic risk reduction by lifestyle intervention and that the magnitude of improvement correlates to increases in plasma HDL levels. Thus, serial 18F-FDG PET/CT may be useful for monitoring improvements in the inflammatory component of atherosclerotic lesions in response to risk modification.  相似文献   
5.
6.
Abstract: In order to evaluate the level of evidence of factors influencing the survival of reconstructions, systematic reviews of the relevant literature were prepared by a group of rapporteurs. The review papers were circulated to the members of the group before the conference and formed the basis for group and panel discussions. Subsequently, modifications were added to the review papers, and suggestions for consensus statements concerning the following topics were prepared and again critically reviewed in the group and in the plenum: Impact of (i) periodontal disease on the survival of tooth-supported reconstructions, (ii) post-surgical factors as supportive therapy on the survival of implant supported reconstructions, (iii) technical and/or biological complications on the survival of different types of reconstructions, (iiii) material choice for reconstructions on the survival of single crowns and fixed dental prostheses.  相似文献   
7.
Defecography in multiple sclerosis patients with severe constipation   总被引:3,自引:0,他引:3  
Gill  KP; Chia  YW; Henry  MM; Shorvon  PJ 《Radiology》1994,191(2):553
  相似文献   
8.
9.
10.
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