全文获取类型
收费全文 | 1203篇 |
免费 | 131篇 |
国内免费 | 38篇 |
专业分类
耳鼻咽喉 | 2篇 |
儿科学 | 7篇 |
妇产科学 | 12篇 |
基础医学 | 168篇 |
口腔科学 | 117篇 |
临床医学 | 52篇 |
内科学 | 157篇 |
皮肤病学 | 63篇 |
神经病学 | 16篇 |
特种医学 | 96篇 |
外科学 | 90篇 |
综合类 | 88篇 |
预防医学 | 64篇 |
眼科学 | 17篇 |
药学 | 275篇 |
中国医学 | 93篇 |
肿瘤学 | 55篇 |
出版年
2024年 | 5篇 |
2023年 | 22篇 |
2022年 | 28篇 |
2021年 | 82篇 |
2020年 | 58篇 |
2019年 | 63篇 |
2018年 | 47篇 |
2017年 | 48篇 |
2016年 | 49篇 |
2015年 | 50篇 |
2014年 | 67篇 |
2013年 | 72篇 |
2012年 | 56篇 |
2011年 | 85篇 |
2010年 | 50篇 |
2009年 | 70篇 |
2008年 | 70篇 |
2007年 | 61篇 |
2006年 | 34篇 |
2005年 | 39篇 |
2004年 | 47篇 |
2003年 | 44篇 |
2002年 | 36篇 |
2001年 | 22篇 |
2000年 | 17篇 |
1999年 | 10篇 |
1998年 | 16篇 |
1997年 | 13篇 |
1996年 | 18篇 |
1995年 | 12篇 |
1994年 | 19篇 |
1993年 | 8篇 |
1992年 | 8篇 |
1991年 | 10篇 |
1990年 | 8篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有1372条查询结果,搜索用时 31 毫秒
1.
Background:We aim to evaluate the efficiency of Raman spectroscopy (RS) in diagnosing suspected patients with intrahepatic cholangiocarcinoma (ICC), manifested by diagnostic sensitivity, specificity, and accuracy.Methods:We will research widely the articles concerning the use of RS in ICC through authenticated database including PubMed/Medline, EMBASE, Web of Science, Ovid, Web of Knowledge, Cochrane Library, and CNKI between January 2012 and November 2020, retrieving at least 1500 spectra with strict criteria. This study will be carried out in accordance to Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. We are going to summarize the test performance using random effects models.Results:Based on the pooled sensitivity, specificity, and diagnostic accuracy, we intend to provide the relative diagnostic efficiency in ICC through RS.Conclusion:Through this systematic review and meta-analysis, we intend to provide the pooled sensitivity, specificity and diagnostic accuracy of RS in the diagnosis of suspected ICC. Other parameters like positive likelihood ratios (LR), negative LR, diagnostic odds ratio (DOR), and area under curve (AUC) of the summary receiver operating characteristics (SROC) curve will also be calculated and related figures will be drawn to help illustrate the efficacy of RS in the diagnosis of ICC. 相似文献
2.
3.
4.
5.
Pan Su Hongli Fan Peiying Liu Yang Li Ye Qiao Jun Hua Doris Lin Dengrong Jiang Jay J. Pillai Argye E. Hillis Hanzhang Lu 《NMR in biomedicine》2020,33(1)
MR Fingerprinting (MRF)‐based Arterial‐Spin‐Labeling (ASL) has the potential to measure multiple parameters such as cerebral blood flow (CBF), bolus arrival time (BAT), and tissue T1 in a single scan. However, the previous reports have only demonstrated a proof‐of‐principle of the technique but have not examined the performance of the sequence in the context of key imaging parameters. Furthermore, there has not been a study to directly compare the technique to clinically used perfusion method of dynamic‐susceptibility‐contrast (DSC) MRI. The present report consists of two studies. In the first study (N = 8), we examined the dependence of MRF‐ASL sequence on TR time pattern. Ten different TR patterns with a range of temporal characteristics were examined by both simulations and experiments. The results revealed that there was a significance dependence of the sequence performance on TR pattern (p < 0.001), although there was not a single pattern that provided dramatically improvements. Among the TR patterns tested, a sinusoidal pattern with a period of 125 TRs provided an overall best estimation in terms of spatial consistency. These experimental observations were consistent with those of numerical simulations. In the second study (N = 8), we compared MRF‐ASL results with those of DSC MRI. It was found that MRF‐ASL and DSC MRI provided highly comparable maps of cerebral blood flow (CBF) and bolus‐arrival‐time (BAT), with spatial correlation coefficients of 0.79 and 0.91, respectively. However, in terms of quantitative values, BAT obtained with MRF‐ASL was considerably lower than that from DSC (p < 0.001), presumably because of the differences in tracer characteristics in terms of diffusible versus intravascular tracers. Test–retest assessment of MRF‐ASL MRI revealed that the spatial correlations of parametric maps were 0.997, 0.962, 0.746 and 0.863 for B1+, T1, CBF, and BAT, respectively. MRF‐ASL is a promising technique for assessing multiple perfusion parameters simultaneously without contrast agent. 相似文献
6.
Jesse I. Hamilton Yun Jiang Brendan Eck Mark Griswold Nicole Seiberlich 《NMR in biomedicine》2020,33(8)
This study introduces a technique called cine magnetic resonance fingerprinting (cine‐MRF) for simultaneous T1, T2 and ejection fraction (EF) quantification. Data acquired with a free‐running MRF sequence are retrospectively sorted into different cardiac phases using an external electrocardiogram (ECG) signal. A low‐rank reconstruction with a finite difference sparsity constraint along the cardiac motion dimension yields images resolved by cardiac phase. To improve SNR and precision in the parameter maps, these images are nonrigidly registered to the same phase and matched to a dictionary to generate T1 and T2 maps. Cine images for computing left ventricular volumes and EF are also derived from the same data. Cine‐MRF was tested in simulations using a numerical relaxation phantom. Phantom and in vivo scans of 19 subjects were performed at 3 T during a 10.9 seconds breath‐hold with an in‐plane resolution of 1.6 x 1.6 mm2 and 24 cardiac phases. Left ventricular EF values obtained with cine‐MRF agreed with the conventional cine images (mean bias ?1.0%). Average myocardial T1 times in diastole/systole were 1398/1391 ms with cine‐MRF, 1394/1378 ms with ECG‐triggered cardiac MRF (cMRF) and 1234/1212 ms with MOLLI; and T2 values were 30.7/30.3 ms with cine‐MRF, 32.6/32.9 ms with ECG‐triggered cMRF and 37.6/41.0 ms with T2‐prepared FLASH. Cine‐MRF and ECG‐triggered cMRF relaxation times were in good agreement. Cine‐MRF T1 values were significantly longer than MOLLI, and cine‐MRF T2 values were significantly shorter than T2‐prepared FLASH. In summary, cine‐MRF can potentially streamline cardiac MRI exams by combining left ventricle functional assessment and T1‐T2 mapping into one time‐efficient acquisition. 相似文献
7.
Jerry R. Paugh Alba Alfonso-Garcia Andrew Loc Nguyen Jeffrey L. Suhalim Marjan Farid Sumit Garg Jeremiah Tao Donald J. Brown Eric O. Potma James V. Jester 《The ocular surface》2019,17(1):151-159
Purpose
This study examined whether hyperspectral stimulated Raman scattering (hsSRS) microscopy can detect differences in meibum lipid to protein composition of normal and evaporative dry eye subjects with meibomian gland dysfunction.Methods
Subjects were evaluated for tear breakup time (TBUT), staining, meibum expression and gland dropout. Expressed meibum was analyzed using SRS vibrational signatures in the CH stretching region (2800–3050?cm?1). Vertex component analysis and K-means clustering were used to group the spectral signatures into four fractions containing high lipid (G1) to high protein (G4).Results
Thirty-three subjects could be statistically analyzed using pooled meibum (13 with stable tear films (TBUTs?>?10?s) and 20 with unstable tear films (TBUTs?≤?10?s). Significant differences in meibum from subjects with unstable vs. stable TBUTs were found for the G1 fraction (medians 0.164 and 0.020, respectively; p?=?0.012) and the G2 fraction (medians 0.244 and 0.272, respectively; p?=?0.045). No differences were observed for the G3 and G4 fractions. Single orifice samples were not significantly different vs. pooled samples from the fellow eye, and eyelid sector samples (nasal, central and temporal) G2:G3 fractional components were not significantly different (p?=?0.449). Spearman analysis suggested a significant inverse correlation between G1 fraction and TBUT (R?=??0.351; p?=?0.045).Conclusions
hsSRS microscopy allows compositional analysis of expressed meibum from humans which correlated to changes in TBUT. These findings support the hypothesis that hsSRS may be useful in classifying meibum quality and evaluating the effects of therapy. 相似文献8.
9.
Vignesh Raman Oliver K. Jawitz Chi-Fu J. Yang Soraya L. Voigt Betty C. Tong Thomas A. D’Amico David H. Harpole 《Journal of thoracic oncology》2019,14(12):2143-2151
IntroductionThere are limited small, single-institution observational studies examining the role of surgery in large cell neuroendocrine cancer (LCNEC). We investigated the outcomes of surgery for stage I to IIIA LCNEC by using the National Cancer Database.MethodsPatients with stage I to IIIA LCNEC were identified in the National Cancer Database (2004–2015) and grouped by treatment: definitive chemoradiation versus surgery. Overall survival, by stage, was the primary outcome. Outcomes of surgical patients were also compared with those of patients with SCLC or other non–small cell histotypes.ResultsA total of 6092 patients met the criteria: 96%, 94%, 75%, and 62% of patients received an operation for stage I, II, IIIA, and cN2 disease, respectively. Complete resection was achieved in at least 85% of patients. The 5-year survival rates for patients undergoing an operation for stage I and II LCNEC were 50% and 45%, respectively. Surgical patients with stage IIIA and N2 disease had 36% and 32% 5-year survival rates, respectively. When compared with stereotactic body radiation in stage I disease and chemoradiation in patients with stage II to IIIA disease, surgery was associated with a survival benefit. Patients with LCNEC who underwent an operation generally experienced worse survival by stage than did those with adenocarcinoma but experienced improved survival compared with patients with SCLC. Perioperative chemotherapy was associated with improved survival for pathologic stage II to IIIA disease.ConclusionsSurgery is associated with reasonable outcomes for stage I to IIA LCNEC, although survival is generally worse than for adenocarcinoma. Surgery should be offered to medically fit patients with both early and locally advanced LCNEC, with guideline-concordant induction or adjuvant therapy. 相似文献