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   2917篇
  免费   387篇
  国内免费   53篇
耳鼻咽喉   93篇
儿科学   35篇
妇产科学   11篇
基础医学   361篇
口腔科学   32篇
临床医学   326篇
内科学   374篇
皮肤病学   22篇
神经病学   429篇
特种医学   528篇
外科学   118篇
综合类   221篇
预防医学   154篇
眼科学   224篇
药学   298篇
  4篇
中国医学   68篇
肿瘤学   59篇
  2024年   7篇
  2023年   47篇
  2022年   104篇
  2021年   138篇
  2020年   163篇
  2019年   146篇
  2018年   168篇
  2017年   137篇
  2016年   156篇
  2015年   118篇
  2014年   227篇
  2013年   215篇
  2012年   163篇
  2011年   196篇
  2010年   156篇
  2009年   130篇
  2008年   118篇
  2007年   121篇
  2006年   130篇
  2005年   92篇
  2004年   83篇
  2003年   71篇
  2002年   73篇
  2001年   57篇
  2000年   44篇
  1999年   34篇
  1998年   20篇
  1997年   25篇
  1996年   22篇
  1995年   21篇
  1994年   17篇
  1993年   16篇
  1992年   11篇
  1991年   11篇
  1990年   13篇
  1989年   13篇
  1988年   12篇
  1987年   12篇
  1986年   10篇
  1985年   13篇
  1984年   12篇
  1983年   6篇
  1982年   6篇
  1981年   9篇
  1980年   2篇
  1979年   5篇
  1978年   2篇
  1977年   4篇
  1973年   1篇
排序方式: 共有3357条查询结果,搜索用时 46 毫秒
1.
目的探讨磁共振结合高分辨率CT在中耳乳突炎患者术前评估中的临床应用。方法选取我院2018年11月~2020年12月接收患有中耳乳突炎的患者40例为研究对象,所有患者均采用磁共振以及高分辨率CT进行诊断检查,比较两组患者诊断后手术特征显示度。结果诊断后,磁共振联合高分辨率CT检查图像显示度高于单独使用磁共振或高分辨率CT诊断(P<0.05)。结论使用磁共振结合高分辨率CT对中耳乳突炎患者进行术前评估,显示度较高,提高诊断准确度,值得推广。  相似文献   
2.
《中国现代医生》2020,58(7):44-46+50+封三
目的 探讨超高分辨率眼前节OCT在结膜增生性疾病诊断中的应用效果。方法 选取2017年1月~2018年12月浙江大学附属第一医院及北仑分院眼科门诊收治的150例(150眼)结膜增生性疾病患者作为研究组。另选同期在我院进行体检的结膜正常者80例(80眼)作为对照组。统计分析超高分辨率眼前节OCT在睑裂斑,翼状胬肉及鳞状上皮瘤等结膜增生性疾病中临床诊断与病理诊断的符合率。观察分析睑裂斑,翼状胬肉及鳞状上皮瘤等结膜增生性疾病的特征性表现。结果 150例(150眼)结膜增生患者临床诊断为睑裂斑患者30例(30眼),翼状胬肉患者100例(100眼),以及眼表鳞状细胞瘤的患者20例(20眼)。与病理学诊断相比,UHR-OCT诊断睑裂斑诊断符合率为100.00%(30/30),翼状胬肉诊断符合率100.00%(98/98),眼表鳞状细胞瘤诊断符合率为90.91%(20/22),经统计学处理,差异无统计学意义(P0.05)。睑裂斑患者图像特征:生长在角巩膜缘处停止,且角膜上未见隆起,与前弹力层间未见高反射信号,与巩膜间未见明显分界。翼状胬肉患者图像特征:结膜上皮厚度轻度增厚,上皮层表现为中等程度的高反射,角膜上皮与前弹力层间表现为较高程度的高反射信号。OSSN患者图像特征:结膜上皮增厚,呈高反射,结膜正常上皮与异常上皮转变突然,无过渡区域,深部组织间上皮内可见瘤变。结论 超高分辨率眼前节OCT在结膜增生性疾病的诊断中具有较高的准确性,且影像特征明显,具有广阔的临床应用前景。  相似文献   
3.
目的利用UPLC-LTQ-Orbitrap-MS技术对刺果番荔枝叶的化学成分进行定性分析。方法采用Waters Acquity UPLC HSS T 3色谱柱(2.1 mm×100 mm,1.8μm),流动相为0.1%甲酸水(A)和乙腈(B)梯度洗脱,流速为0.3 mL/min,进样量2μL,在电喷雾正负离子模式下采集数据。经Reaxys数据库检索番荔枝属类化合物信息,通过质谱信息比对各化合物的m/z值、保留时间、质谱特征碎片等,并结合文献数据对鉴定的化合物进行验证。结果根据各化合物的特征裂解规律,从刺果番荔枝叶中共鉴定出45个化合物,包括16个生物碱类,14个番荔枝内酯类,7个黄酮类和8个其他类化合物,其中以番荔枝内酯类和生物碱类成分居多,与文献报道番荔枝内酯与生物碱类化合物是发挥抗癌的主要活性成分一致。结论利用UPLC-LTQ-Orbitrap-MS技术对刺果番荔枝叶中的化学成分进行了快速、准确的定性分析,为刺果番荔枝叶的提取分离与药效物质基础的研究提供依据。  相似文献   
4.
AIM: To evaluate the outcome of primary vesicoureteral reflux (VUR) using conservative treatment. METHODS: Eighty-seven children with primary VUR who had been treated with a conservative medical regimen and monitored through a yearly cystogram were recruited for the study. The study was conducted at the Pediatric Nephrology Clinic in Songklanagarind Hospital, the major tertiary care center in southern Thailand. Statistical analyses using Kaplan-Meier survival curves, chi-squared test, Fisher's exact test and multivariate analysis with Cox regression were performed. RESULTS: The study group consisted of 41 boys and 46 girls, with a total of 133 VUR. The age of the boys was significantly lower than that of the girls (P < 0.001). Resolution of the low grades (grades I-III) of VUR was significantly more frequent than that of the high grades (grades IV-V) (68/95, 72%vs 14/38, 37%; P < 0.001). Using the Kaplan-Meier survival analysis and log-rank test, the resolutions of VUR in boys versus girls, and age <1 years versus >or=1 years were not significantly different (P = 0.2252 and 0.4756, respectively). Low-grade VUR and unilateral VUR had significantly higher probabilities of resolution than high-grade VUR and bilateral VUR, respectively (P = 0.0041 and 0.0467, respectively). Multivariate Cox regression analysis indicated that among low-grade VUR, boys and unilateral VUR had significantly higher probabilities of resolution. Among the high-grade VUR, neither sex nor laterality had a significant effect on the probabilities of VUR resolution. CONCLUSION: This study offers more evidence that children with low-grade VUR have a higher chance of reflux resolution if they are boys and have only unilateral VUR. There is still no good guide for resolution of reflux in children with high-grade VUR.  相似文献   
5.
m.  fox    r.  sweis    t.  wong  † & a.  anggiansah 《Neurogastroenterology and motility》2007,19(10):798-803
Oesophageal spasm presents with dysphagia and chest pain. Current treatments are limited by poor efficacy and side effects. Studies in health and oesophageal dysmotility show that sildenafil reduces peristaltic pressure and velocity; however the clinical efficacy and tolerability in symptomatic oesophageal spasm remains uncertain. We provided open-label sildenafil treatment to two patients with severe, treatment resistant symptoms associated with oesophageal spasm. The effects of sildenafil on oesophageal function and symptoms were documented by high resolution manometry (HRM). Patients were followed up to assess the efficacy of maintenance treatment with sildenafil b.i.d. HRM revealed focal and diffuse spasm in the smooth muscle oesophagus that were associated with symptoms in both cases, especially on swallowing solids. Lower oesophageal sphincter function was normal. A therapeutic trial of 25-50 mg sildenafil suppressed oesophageal contraction almost completely for water swallows; however effective, coordinated peristalsis returned with reduced frequency of spasm for solid swallows. Dysphagia and chest pain resolved during the therapeutic trial and efficacy was maintained on maintenance treatment with 25-50 mg sildenafil b.i.d. without troublesome side effects. This report shows that sildenafil can improve oesophageal function and relieve dysphagia and chest pain in patients with oesophageal spasm in whom other treatments have failed.  相似文献   
6.
Limited spatial resolution is a key obstacle to the study of brain white matter structure with diffusion tensor imaging (DTI). In its frequent implementation with single-excitation spin-echo echo-planar sequences, DTI's ability to resolve small structures is strongly restricted by T2 and T2* decay, B0 inhomogeneity, and limited signal-to-noise ratio (SNR). In this work the influence of sensitivity encoding (SENSE) on diffusion-weighted (DW) image properties is investigated. Computer simulations showed that the PSF becomes narrower with increasing SENSE reduction factors, R, enhancing the intrinsic resolution. After a brief theoretical discussion, we describe the estimation of SNR on a pixel-by-pixel basis as a function of R. The mean image SNR behavior is manifold: SENSE is capable of increasing SNR efficiency by reducing the echo time (TE). Each SNR(R) curve reveals a maximum that depends on the amount of partial Fourier encoding used. The overall best SNR efficiency for an eight-element head coil array and a b-factor of 1000 s/mm2 is achieved at R = 2.1 and partial Fourier encoding of 60%. In vivo tensor maps of volunteers and a patient, with an in-plane resolution of 0.78 x 0.78 mm2, are also presented to demonstrate the practical implementation of the parallel approach.  相似文献   
7.
BACKGROUND: Past receiver operating characteristic (ROC) studies have demonstrated that single photon emission computed tomography (SPECT) perfusion imaging by use of iterative reconstruction with combined compensation for attenuation, scatter, and detector response leads to higher area under the ROC curve (A(z)) values for detection of coronary artery disease (CAD) in comparison to the use of filtered backprojection (FBP) with no compensations. A new ROC study was conducted to investigate whether this improvement still holds for iterative reconstruction when observers have available all of the imaging information normally presented to clinical interpreters when reading FBP SPECT perfusion slices. METHODS AND RESULTS: A total of 87 patient studies including 50 patients referred for angiography and 37 patients with a lower than 5% likelihood for CAD were included in the ROC study. The images from the two methods were read by 4 cardiology fellows and 3 attending nuclear cardiologists. Presented for the FBP readings were the short-axis, horizontal long-axis, and vertical long-axis slices for both the stress and rest images; cine images of both the stress and rest projection data; cine images of selected cardiac-gated slices; the CEQUAL-generated stress and rest polar maps; and an indication of patient gender. This was compared with reading solely the iterative reconstructed stress slices with combined compensation for attenuation, scatter, and resolution. With A(z) as the criterion, a 2-way analysis of variance showed a significant improvement in detection accuracy for CAD for the 7 observers (P = .018) for iterative reconstruction with combined compensation (A(z) of 0.895 +/- 0.016) over FBP even with the additional imaging information provided to the observers when scoring the FBP slices (A(z) of 0.869 +/- 0.030). When the groups of 3 attending physicians or 4 cardiology fellows were compared separately, the iterative technique was not statistically significantly better; however, the A(z) for each of the 7 observers individually was larger for iterative reconstruction than for FBP. Compared with results from our previous studies, the additional imaging information did increase the diagnostic accuracy of FBP for CAD but not enough to undo the statistically significantly higher diagnostic accuracy of iterative reconstruction with combined compensation. CONCLUSIONS: We have determined through an ROC investigation that included two classes of observers (experienced attending physicians and cardiology fellows in training) that iterative reconstruction with combined compensation provides statistically significantly better detection accuracy (larger A(z)) for CAD than FBP reconstructions even when the FBP studies were read with all of the extra clinical nuclear imaging information normally available.  相似文献   
8.
9.
重点介绍了地尔硫的化学合成和拆分方法,以及近年来在其不对称合成领域的进展。  相似文献   
10.
We report a rare case of advanced renal cell carcinoma in apatient who showed complete resolution of metastases to thelung and bones after nephrectomy, partial jejunectomy and subsequentalpha-interferon therapy. The patient was a 54-year-old manwhose right lung and left femur metastases were detected beforenephrectomy. In the seventh week after nephrectomy, a partialjejunectomy was carried out because of the obstructive ileuscaused by intraluminal multiple metastases of the jejunum. Apathological fracture of the metastasized right humerus occurredsubsequently. After four months of intramuscular alpha-interferonadministration (3x106 units/day), however, x-rays revealed thecomplete disappearance of the metastatic lung shadow and a solidunion of the humerus, and there were no tumor cells in the femurspecimen resected at the subsequent reconstruction surgery ofthe left leg. Seven years have passed from onset, and the patientis still alive and disease free.  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