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   5677篇
  免费   487篇
  国内免费   12篇
耳鼻咽喉   71篇
儿科学   190篇
妇产科学   139篇
基础医学   613篇
口腔科学   133篇
临床医学   675篇
内科学   1007篇
皮肤病学   62篇
神经病学   556篇
特种医学   178篇
外科学   873篇
综合类   132篇
一般理论   2篇
预防医学   730篇
眼科学   143篇
药学   336篇
中国医学   6篇
肿瘤学   330篇
  2023年   52篇
  2022年   81篇
  2021年   225篇
  2020年   95篇
  2019年   157篇
  2018年   187篇
  2017年   131篇
  2016年   123篇
  2015年   160篇
  2014年   186篇
  2013年   252篇
  2012年   318篇
  2011年   323篇
  2010年   148篇
  2009年   164篇
  2008年   269篇
  2007年   253篇
  2006年   207篇
  2005年   226篇
  2004年   213篇
  2003年   190篇
  2002年   153篇
  2001年   134篇
  2000年   161篇
  1999年   118篇
  1998年   68篇
  1997年   45篇
  1996年   54篇
  1995年   38篇
  1994年   57篇
  1993年   38篇
  1992年   83篇
  1991年   90篇
  1990年   82篇
  1989年   75篇
  1988年   78篇
  1987年   62篇
  1986年   67篇
  1985年   52篇
  1984年   52篇
  1983年   55篇
  1982年   44篇
  1981年   34篇
  1980年   34篇
  1979年   59篇
  1978年   55篇
  1976年   28篇
  1974年   29篇
  1973年   32篇
  1970年   29篇
排序方式: 共有6176条查询结果,搜索用时 62 毫秒
971.
972.
Abstract

Introduction: ASPIRE Excellence Awards in Student Assessment are offered to medical schools with innovative and comprehensive assessment programmes adjudged by international experts, using evidence-based criteria.

The journeys of three ASPIRE-winning medical schools toward “assessment excellence” are presented. These schools include Aga Khan University Medical College (AKU-MC), Pakistan, Southern Illinois University School of Medicine (SIUSOM), USA, and University of Leeds School of Medicine, UK.

Methods: The unfolding journeys highlighting achievements, innovations, and essential components of each assessment programme were compared to identify differences and commonalities.

Results: Cultural contextual differences included developed-versus-developing country, east-west, type of regulatory bodies, and institutional-versus-national certifying/licensing examinations, which influence curricula and assessments.

In all, 12 essential commonalities were found: alignment with institutional vision; sustained assessment leadership; stakeholder engagement; communication between curriculum and assessment; assessment-for-learning and feedback; longitudinal student profiling of outcome achievement; assessment rigor and robustness; 360° feedback from-and-to assessment; continuous enrichment through rigorous quality assurance; societal sensitivity; influencing others; and a “wow factor.”

Conclusions: Although the journeys of the three medical schools were undertaken in different cultural contexts, similar core components highlight strong foundations in student assessment. The journeys continue as assessment programmes remain dynamic and measurement science expands. This article may be helpful to other institutions pursuing excellence in assessment.  相似文献   
973.
974.
Prevention Science - Parents frustrated about food marketing influences need media management skills to challenge marketing messages and interpret factual content. We tested a media literacy-based,...  相似文献   
975.
In the context of survival analysis, calibration refers to the agreement between predicted probabilities and observed event rates or frequencies of the outcome within a given duration of time. We aimed to describe and evaluate methods for graphically assessing the calibration of survival models. We focus on hazard regression models and restricted cubic splines in conjunction with a Cox proportional hazards model. We also describe modifications of the Integrated Calibration Index, of E50 and of E90. In this context, this is the average (respectively, median or 90th percentile) absolute difference between predicted survival probabilities and smoothed survival frequencies. We conducted a series of Monte Carlo simulations to evaluate the performance of these calibration measures when the underlying model has been correctly specified and under different types of model mis-specification. We illustrate the utility of calibration curves and the three calibration metrics by using them to compare the calibration of a Cox proportional hazards regression model with that of a random survival forest for predicting mortality in patients hospitalized with heart failure. Under a correctly specified regression model, differences between the two methods for constructing calibration curves were minimal, although the performance of the method based on restricted cubic splines tended to be slightly better. In contrast, under a mis-specified model, the smoothed calibration curved constructed using hazard regression tended to be closer to the true calibration curve. The use of calibration curves and of these numeric calibration metrics permits for a comprehensive comparison of the calibration of competing survival models.  相似文献   
976.

Purpose

The regionalization of trauma in the USA results in frequent transfers of patients from a primary hospital ED to a higher level trauma facility. While many hospitals have a Picture Archive Communication System (PACS) which captures digital radiological images, these are often not available to the receiving institution resulting in duplicate imaging. The state of Arkansas instituted a trauma image repository (TIR) in July 2013. We examined whether implementation of this repository would impact CT scan duplication in the trauma system.

Methods

This was a retrospective analysis of trauma patients transferred from outlying hospitals in Arkansas and Missouri to a single level 1 trauma hospital in Missouri between July 2012 and June 2015. We compared the duplicate CT rate for patients transferred from Arkansas and Missouri hospitals before and after the repository was implemented for Arkansas.

Results

Prior to implementation (July 2012–June 2013) of Arkansas TIR, duplicate CT rates were similar for patients transferred from Arkansas (11.5%?±?2.8) or Missouri (16.3%?±?7.5). Following implementation (July 2013–June 2014), the duplicate CT rate for patients transferred from Arkansas was significantly lower (Arkansas?=?10.1% vs. Missouri 16.2%; CI 95%, p?=?0.02), and significance continued (Arkansas?=?9.0% vs. Missouri?=?17.8%; CI 95%, p?=?0.02) during follow-up (July 2014–June 2015).

Conclusion

Fewer patients received duplicated scans within the Arkansas as compared with the Missouri-based trauma referral systems regardless of Injury Severity Scores (ISS). Our findings suggest that TIR adoption coupled with PACS improved transferability of radiographic studies and could improve patient care while reducing costs in trauma transfers.
  相似文献   
977.
Treatment-related changes can be difficult to differentiate from progressive glioma using MRI with contrast (CE). The purpose of this study is to compare the sensitivity and specificity of 18F-DOPA-PET and MRI in patients with recurrent glioma. Thirteen patients with MRI findings suspicious for recurrent glioma were prospectively enrolled and underwent 18F-DOPA-PET and MRI for neurosurgical planning. Stereotactic biopsies were obtained from regions of concordant and discordant PET and MRI CE, all within regions of T2/FLAIR signal hyperintensity. The sensitivity and specificity of 18F-DOPA-PET and CE were calculated based on histopathologic analysis. Receiver operating characteristic curve analysis revealed optimal tumor to normal (T/N) and SUVmax thresholds. In the 37 specimens obtained, 51% exhibited MRI contrast enhancement (M+) and 78% demonstrated 18F-DOPA-PET avidity (P+). Imaging characteristics included M?P? in 16%, M?P+ in 32%, M+P+ in 46% and M+P? in 5%. Histopathologic review of biopsies revealed grade II components in 16%, grade III in 43%, grade IV in 30% and no tumor in 11%. MRI CE sensitivity for recurrent tumor was 52% and specificity was 50%. PET sensitivity for tumor was 82% and specificity was 50%. A T/N threshold?>?2.0 altered sensitivity to 76% and specificity to 100% and SUVmax?>?1.36 improved sensitivity and specificity to 94 and 75%, respectively. 18F-DOPA-PET can provide increased sensitivity and specificity compared with MRI CE for visualizing the spatial distribution of recurrent gliomas. Future studies will incorporate 18F-DOPA-PET into re-irradiation target volume delineation for RT planning.  相似文献   
978.
Mitochondrial DNA (mtDNA) can provide a means for forensic identity testing when genotyping of nuclear DNA (nuDNA) targets is not possible due to degradation or lack of template. For degraded samples, an indication of the quantity and quality of mtDNA is essential to allow selection of appropriately sized targets for hypervariable region (HVR) analysis, which may conserve sample and resources. Three human-specific mtDNA targets of increasing length (86, 190 and 452 base pairs) were amplified by singleplex quantitative real-time PCR (qPCR), capable of providing an index of mtDNA degradation from fragment length information. Quantification was achieved by preparation of a standard curve for each target, using a purified mtDNA standard containing all three targets of interest, which produced a linear, accurate and precise result from 1×108 to 10 copies. These novel assays demonstrated excellent sensitivity, specificity and reproducibility in line with the minimum information for qPCR experiments (MIQE) guidelines. Further, a separate inhibition control reaction was included to guide sample clean-up and ensure the validity of degradation assays. This protocol assists the selection and analysis of appropriately sized targets to maximize the chance of obtaining an informative result in downstream assays like sequencing.  相似文献   
979.
980.
OBJECTIVES: The postnatal period is a time of increased onset and relapse of mental illness. It poses a clinical dilemma, as many mothers requiring medication acutely or prophylactically will also choose to breast feed. The present paper first reviews the safety of psychotropes in breast-fed infants and the usefulness of prophylaxis for women at risk of postpartum affective relapse and, second, provides guidelines in the use of psychotropic drugs in breast-feeding women. METHODS: A Medline review was conducted reviewing all papers published during the period 1993-1998 (and their associated bibliographies) on the use of psychotropes in breast-feeding women and the prophylactic usefulness of medications in women at risk of affective postpartum relapse. RESULTS: Findings are based on case reports and small, mostly uncontrolled studies. Both tricyclic antidepressants (TCA) and specific serotonin re-uptake inhibitors (SSRIs) appear to be relatively safe in breast feeding. Antidepressants commenced in the early postpartum period may reduce depressive relapse. While prophylactic lithium appears to significantly reduce relapse of affective psychosis in the puerperium, there have been no studies of the anticonvulsants in the puerperium. Finally, high dose antipsychotics should be avoided, as they may be associated with long-term adverse sequelae in the infant. CONCLUSIONS: On the basis of current knowledge, the use of SSRIs, TCA, carbamazepine, sodium valproate and short-acting benzodiazepines in breast feeding is relatively safe. If lithium is to be used, close collaboration with a paediatrician is essential. The long-term risks of antipsychotics, especially at high doses, remain to be clarified. Before a decision can be made, the risk-benefit ratio must be clearly outlined and discussed with the mother and her partner.  相似文献   
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