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   8537篇
  免费   449篇
  国内免费   78篇
耳鼻咽喉   99篇
儿科学   189篇
妇产科学   68篇
基础医学   870篇
口腔科学   162篇
临床医学   582篇
内科学   2210篇
皮肤病学   175篇
神经病学   606篇
特种医学   346篇
外科学   1815篇
综合类   39篇
预防医学   219篇
眼科学   206篇
药学   452篇
中国医学   16篇
肿瘤学   1010篇
  2023年   88篇
  2022年   163篇
  2021年   309篇
  2020年   171篇
  2019年   183篇
  2018年   279篇
  2017年   202篇
  2016年   262篇
  2015年   263篇
  2014年   284篇
  2013年   364篇
  2012年   532篇
  2011年   589篇
  2010年   309篇
  2009年   260篇
  2008年   412篇
  2007年   459篇
  2006年   440篇
  2005年   398篇
  2004年   402篇
  2003年   416篇
  2002年   359篇
  2001年   154篇
  2000年   131篇
  1999年   130篇
  1998年   88篇
  1997年   67篇
  1996年   75篇
  1995年   63篇
  1994年   81篇
  1993年   54篇
  1992年   105篇
  1991年   98篇
  1990年   95篇
  1989年   109篇
  1988年   86篇
  1987年   67篇
  1986年   76篇
  1985年   61篇
  1984年   35篇
  1983年   30篇
  1982年   19篇
  1981年   18篇
  1980年   22篇
  1979年   36篇
  1978年   17篇
  1977年   23篇
  1971年   20篇
  1969年   17篇
  1968年   16篇
排序方式: 共有9064条查询结果,搜索用时 15 毫秒
101.
Optic nerve injury demonstrated by MRI with STIR sequences   总被引:1,自引:0,他引:1  
We studied nine patients with optic nerve injury associated with closed head trauma by magnetic resonance imaging (MRI) with short inversion time inversion recovery (STIR) sequences on 11 occasions from 4 days to 14 years after the injury: three studies were within 17 days and eight over 4 months to 14 years. MRI revealed abnormal high signal in 10 of the 11 injured nerves. MRI 4 days after the injury showed no abnormality.  相似文献   
102.
Laparoscopic pancreatic surgery is evolving rapidly; however, the surgical treatment of periampullary tumors is still fraught with challenges, such as technical difficulty and the appropriateness of oncologic treatment for these patients. We describe how we performed laparoscopic pancreaticoduodenectomy (LPD) combined with minilaparotomy successfully in six consecutive patients. This procedure consisted of two surgical phases: safe laparoscopic surgery, including the Kocher maneuver, tunneling behind the pancreatic neck, and dissecting along the uncinate process with magnified vision; and a secure open approach with complete skeletonization of the hepatoduodenal ligament and alimentary tract reconstruction, performed similarly to conventional pancreaticoduodenectomy, under direct visualization through the minilaparotomy. By performing this procedure, we combined a safe and secure minilaparotomy approach under direct vision with a less invasive laparoscopic approach providing a magnified image. Our experience demonstrates that LPD combined with minilaparotomy is technically feasible for selected patients with periampullary tumors.  相似文献   
103.

Purpose

Gastrointestinal stromal tumors (GISTs) should be surgically resected, even those smaller than 5?cm in size, which is the threshold of clinical malignancy for submucosal tumors (SMTs) in the gastrointestinal tract. This study reviewed the use of laparoscopic surgery for gastric partial resection of GISTs or SMTs that were suspected to be GISTs.

Methods

Eighteen patients underwent laparoscopic partial resection of the stomach for GISTs or SMTs. The tumor location was confirmed by intraluminal endoscopy. One-half of the circumference around the tumor was dissected, and the tumor was turned toward the abdominal cavity. The nonresected part of the tumor and the edge of the incision line was lifted up using forceps, and the incision line was closed using laparoscopic stapling devices.

Results

Two cases were diagnosed as GIST by endoscopic biopsy. Six patients underwent endoscopic ultrasound-guided fine-needle aspiration biopsy (EUS-FNAB) examinations, which diagnosed five GISTs. There were 18 tumors smaller than 5?cm, including 10 GISTs, 4 leiomyomas, 3 schwannomas, and one heterotopic pancreas.

Conclusions

Endoscopic ultrasound-guided FNAB is recommended for definite preoperative diagnosis of histopathologically unknown SMTs to determine the indications for surgery. The laparoscopic approach with the assistance of endoscopy is useful for improving the curability, with minimal invasiveness for the partial resection of GISTs.  相似文献   
104.
105.
Advanced age donors have inferior outcomes of liver transplantation for Hepatitis C (HCV). Aged donors grafts may be transplanted into young or low model for end stage liver disease (MELD) patients in order to offset the effect of donor age. However, it is not well understood how to utilize liver grafts from advanced aged donors for HCV patients. Using the UNOS database, we retrospectively studied 7508 HCV patients who underwent primary liver transplantation. Risk factors for graft failure and graft survival using advanced aged grafts (donor age ≥ 60 years) were analyzed by Cox hazards models, donor risk index (DRI) and organ patient index (OPI). Recipient's age did not affect on graft survival regardless of donor age. Advanced aged grafts had significant inferior survival compared to younger aged grafts regardless of MELD score (P < 0.0001). Risk factors of HCV patients receiving advanced aged grafts included donation after cardiac death (DCD, HR: 1.69) and recent hospitalization (HR: 1.43). Advanced aged grafts showed significant difference in graft survival of HCV patients with stratification of DRI and OPI. In conclusion, there was no offsetting effect by use of advanced aged grafts into younger or low MELD patients. Advanced aged grafts, especially DCD, should be judiciously used for HCV patients with low MELD score.  相似文献   
106.
Abstract Background: Advances in percutaneous coronary intervention (PCI) using drug‐eluting stents (DES) have impacted clinical practice. However, the efficacy of DES for dialysis patients still remains controversial. This study compares the early and long‐term clinical outcomes of coronary artery bypass grafting (CABG) and PCI with DES in dialysis patients. Methods: A retrospective review was performed in 125 dialysis patients treated between 2004 and 2007. Fifty‐eight patients underwent CABG and 67 underwent PCI with DES. The overall death, cardiac death, and cardiac‐related event rates were analyzed using the Kaplan‐Meier method. For the risk‐adjusted comparisons, multivariable logistic and Cox regression analyses were used. Results: The preoperative characteristics of the patients were similar except for the ejection fraction (p = 0.002) and the number of diseased vessels (p < 0.001). The 30‐day mortality was 0 in both groups. The overall survival rates at one, three, and five years were 84.2%, 64.7%, and 56.2% in CABG group and 88.2%, 75.5%, and 61.7% in DES group, respectively (p = 0.202). The rates of freedom from cardiac‐related events at one, three, and five years were 76.6%, 68.1%, and 48.6%, and 63.0%, 31.4%, and 0% in CABG and DES groups (p < 0.001), respectively, including seven (10%) late thromboses in the DES group. Although the risk‐adjusted analysis showed no significant difference for overall and cardiac death rates, the rates of cardiac‐related events and graft/stent failure were significantly higher in the DES group. Conclusions: CABG is superior for revascularization in dialysis patients compared with PCI using DES in terms of freedom from cardiac‐related events. (J Card Surg 2012;27:281‐287)  相似文献   
107.
H+/peptide transporter, PEPT1, is functionally expressed in some human cancer cell lines and might be a candidate molecular target for detection of cancers in vivo using PET. The aim of the present study was to establish a novel tumor-imaging technology using a PET tracer targeted to H+/peptide transporter(s). We also compared the tracer with 18F-FDG, focusing on the specificity of their accumulation between tumor and inflammatory tissues. METHODS: A dipeptide PET tracer, 11C-glycylsarcosine (11C-Gly-Sar), was injected intravenously into athymic mice transplanted with human pancreatic, prostate, and gastric cancer cells. The distribution patterns of 11C-Gly-Sar and 18F-FDG in the tumor-bearing mice, and in mice with inflammatory tissue, were assessed by imaging with a positron planar imaging system (PPIS). Tissue distributions of tracer radioactivity were also measured. The expression levels of PEPT1 and PEPT2 (PEPTs) proteins in tumor xenografts and inflammatory tissue were examined by immunohistochemical analysis. The messenger RNA expression levels of PEPTs in 58 available cancer cell lines were quantified by means of real-time polymerase chain reaction. RESULTS: All 3 tumor xenografts were well visualized with the PPIS after injection of 11C-Gly-Sar. Expression of PEPTs in those xenografts was confirmed by immunohistochemical analysis. Tumor-to-blood concentration ratios of 11C-Gly-Sar increased in a time-dependent manner and were much higher than unity. Most of the radioactivity found in the tumor tissue was recovered as the intact tracer. These results indicated that 11C-Gly-Sar was taken up by the PEPTs in tumor xenografts. It is noteworthy that 11C-Gly-Sar was minimally present in inflammatory tissues that expressed no PEPT1 or PEPT2 protein, whereas 18F-FDG was highly accumulated, with the values of the selectivity index being >25.1 and 0.72 for 11C-Gly-Sar and 18F-FDG, respectively. The mRNAs of PEPT1 and PEPT2 were expressed in 27.6% and 93.1%, respectively, of the cancer cell lines examined in the present study. CONCLUSION: The present study indicates that 11C-Gly-Sar is a promising tumor-imaging agent and is superior to 18F-FDG for distinguishing between tumors and inflammatory tissue. Because PEPTs were ubiquitously expressed in various types of tumor cells examined, 11C-Gly-Sar could be useful for the detection of many types of cancers.  相似文献   
108.
Purpose  The aim of this study was to investigate the regional differences between the morphologic and functional changes in the same patients with frontotemporal dementia (FTD) using statistical parametric mapping and voxel-based morphometry (VBM). Methods  Thirteen FTD patients (mean age, 64.9 years old; mean MMSE score, 17.7), 20 sex-matched Alzheimer’s disease (AD) patients (mean age, 65.0 years old; mean MMSE score, 17.5), and 20 normal volunteers (mean age, 65.2 years old; mean MMSE score, 29.0) underwent both [18F]FDG positron emission tomography and three-dimensional spoiled gradient echo MRI. Statistical parametric mapping was used to conduct a VBM analysis of the morphologic data, which were compared voxel by voxel with the results of a similar analysis of glucose metabolic data. Results  FTD patients showed decreased grey matter volume and decreased glucose metabolism in the frontal lobe and anterior temporal lobe. In addition, there was a clear asymmetry in grey matter volume in FTD patients by the VBM analysis while the glucose metabolic data showed little asymmetry. In AD patients, glucose metabolic reduction occurred in the bilateral posterior cingulate gyri and parietal lobules while grey matter density decreased the least in the same patients. Conclusion  In FTD, metabolic and morphologic changes occur in the bilateral frontal lobe and temporal lobe with a limited asymmetry whereas there was considerable discordance in the AD group.  相似文献   
109.
The utility of measuring the corpus callosal angle (CA) for the diagnosis of idiopathic normal pressure hydrocephalus (INPH) was investigated. Three-dimensional magnetic resonance imaging (MRI) was performed in 34 INPH patients, 34 Alzheimer’s disease (AD) patients, and 34 normal control (NC) subjects. Measurement of the CA on the coronal MR images of the posterior commissure perpendicular to the anteroposterior commissure plane was performed for all subjects. The CA of the INPH group (mean ± SD, 66 ± 14°) was significantly smaller than those of the AD (104 ± 15°) and NC (112 ± 11°) groups. When using the threshold of the mean − 2SD value of the NC group (= 90°), an accuracy of 93%, sensitivity of 97%, and specificity of 88% were observed for discrimination of INPH from AD patients. Measuring the CA helps in differentiating INPH patients from AD and normally aged subjects.  相似文献   
110.
PURPOSE: The volar region of the scapholunate interosseous ligament is one of the key structures that maintains scapholunate alignment. It is, however, difficult to evaluate this ligament using standard diagnostic procedures, including the arthroscopy through a dorsal portal. We have performed arthroscopic evaluation of this ligament through a volar portal. METHODS: Skin incision was made at just radial of the flexor carpi radialis tendon and the portal was opened through the tendon sheath. RESULTS: The volar approach enabled us to directly observe the extent of the tear of the volar region of scapholunate interosseous ligament. A shaver is inserted through the dorsal portal, and debridement can be performed by using the volar portal vein. We have not had any complications using volar portal. CONCLUSION: Volar approach is a feasible and safe procedure to evaluate and treat the volar region of the scapholunate interosseous ligament.  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