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   5637篇
  免费   278篇
  国内免费   33篇
耳鼻咽喉   139篇
儿科学   91篇
妇产科学   27篇
基础医学   788篇
口腔科学   125篇
临床医学   418篇
内科学   1341篇
皮肤病学   81篇
神经病学   244篇
特种医学   190篇
外科学   1115篇
综合类   30篇
预防医学   160篇
眼科学   47篇
药学   450篇
中国医学   1篇
肿瘤学   701篇
  2023年   42篇
  2022年   103篇
  2021年   160篇
  2020年   75篇
  2019年   100篇
  2018年   124篇
  2017年   85篇
  2016年   105篇
  2015年   116篇
  2014年   134篇
  2013年   147篇
  2012年   252篇
  2011年   275篇
  2010年   139篇
  2009年   116篇
  2008年   209篇
  2007年   238篇
  2006年   228篇
  2005年   232篇
  2004年   237篇
  2003年   218篇
  2002年   221篇
  2001年   180篇
  2000年   199篇
  1999年   193篇
  1998年   61篇
  1997年   47篇
  1996年   45篇
  1995年   48篇
  1994年   44篇
  1993年   33篇
  1992年   118篇
  1991年   117篇
  1990年   114篇
  1989年   110篇
  1988年   119篇
  1987年   117篇
  1986年   120篇
  1985年   101篇
  1984年   68篇
  1983年   73篇
  1979年   44篇
  1977年   35篇
  1974年   28篇
  1973年   38篇
  1972年   33篇
  1971年   36篇
  1970年   27篇
  1969年   29篇
  1968年   34篇
排序方式: 共有5948条查询结果,搜索用时 15 毫秒
61.
Background: T1-shortening contrast media are routinely used in magnetic resonance (MR) examinations for the diagnosis of brain tumors. Although some studies show a benefit of 3 Tesla (T) compared to 1.5T in delineation of brain tumors using contrast media, it is unclear which pulse sequences are optimal.

Purpose: To compare gadopentetate dimeglumine (Gd-DTPA)-induced signal enhancements in rat brain C6 glioma in the thalamus region among different pulse sequences in 3T MR imaging.

Material and Methods: Five rats with a surgically implanted C6 glioma in their thalamus were examined. T1-weighted brain images of the five rats were acquired before and after Gd-DTPA administration (0.1 mmol/kg) using three clinically available pulse sequences (spin echo [SE], fast SE [FSE], fast spoiled gradient echo [FSPGR]) at 3T. Signal enhancement in the glioma (ET) was calculated as the signal intensity after Gd-DTPA administration scaled by that before administration. Pulse sequences were compared using the Tukey-Kramer test.

Results: ET was 1.12±0.05 for FSE, 1.26±0.11 for FSPGR, and 1.20±0.11 for SE. FSPGR showed significantly higher signal enhancement than FSE and comparable enhancement to SE.

Conclusion: FSPGR is superior to FSE and comparable to SE in its ability to delineate rat brain C6 glioma in the thalamus region.  相似文献   
62.
Leaving anterior cruciate ligament (ACL) insufficiency and posterior cruciate ligament (PCL) insufficiency untreated frequently leads to osteoarthritis (OA). The purpose of this study was to evaluate dynamically the lateral thrust of ACL-insufficient knees and PCL-insufficient knees, and from the findings investigate the relationship between cruciate ligament insufficiency and OA occurrence. An acceleration sensor was attached to the affected and control anterior tibial tubercles, acting in medial-lateral and perpendicular directions. The lateral thrust immediately after heel strike was measured continuously by a telemeter under stabilised walking conditions. When compared to the contralateral healthy knee, the peak value of lateral acceleration immediately after heel strike was significantly larger in the ACL-insufficient knee; and lateral thrust was increased, but not significantly, in the PCL-insufficient knee. Given that lateral thrust of the knee during walking increases due to ACL or PCL injury, it may be a principal contributor to OA progression.  相似文献   
63.
64.
We report a case of double cancer of the cystic duct and gallbladder associated with low junction of the cystic duct. A 73-year-old woman was admitted to the hospital complaining of upper abdominal pain. Endoscopic retrograde cholangiography showed a stenotic lesion in the lower common bile duct and no visualization of the cystic duct or gallbladder. Enhanced computed tomography revealed a heterogeneously enhanced tumorous lesion around the lower bile duct in the pancreatic head. A diagnosis of cancer arising from the cystic duct that entered the lower part of the common hepatic duct was made by intraductal ultrasonography, which showed an intraluminal protruding lesion in the cystic duct. Isolated gallbladder cancer was also diagnosed, by abdominal computed tomography. She underwent pancreaticoduodenectomy with dissection of regional lymph nodes. Histological examination revealed moderately differentiated adenocarcinoma of the cystic duct and well-differentiated adenocarcinoma of the gallbladder. Double cancer of the cystic duct and gallbladder is extremely rare, and this case also suggests a relationship between a low junction of the cystic duct and neoplasm in the biliary tract.  相似文献   
65.
Arthroscopic findings in Maisonneuve fractures   总被引:1,自引:0,他引:1  
Background A Maisonneuve fracture consists of a proximal fibular fracture with associated syndesmotic ligament disruption and injury to the medial ankle structures. The treatment outcome is good in most cases, although poor results have also been reported. The purpose of this study was to investigate intra-articular lesions in Maisonneuve fractures. Methods The subjects consisted of four patients (four ankle joints) who had suffered a Maisonneuve fracture and had undergone surgical treatment between June 2005 and November 2005. The mean age was 24. 2 years. At the time of surgery, we performed ankle arthroscopy and determined the presence of tibiofibular syndesmosis disruption, cartilaginous damage, and ligament damage. Lesions of the articular cartilage were graded by depth as determined by inspection and probing. Results All four of the cases had cartilaginous damage to the medial section of the talar dome. Lateral lesions were not observed. Chondral debris and hemarthrosis were noted in virtually all cases, and each ankle had a tear on the anterior inferior tibiofibular ligament and interosseous tibiofibular ligament. No patients had a tear of the posterior inferior tibiofibular ligament. Conclusions Arthroscopy was useful in identifying associated intra-articular lesions in Maisonneuve fractures.  相似文献   
66.
OBJECTIVE: Reoperative coronary artery bypass grafting with cardiopulmonary bypass tends to cause a higher mortality and morbidity than the primary operation. The purpose of this study was to discuss the effectiveness and safety of a minimally invasive coronary artery bypass procedure for patients who had previously undergone coronary artery bypass surgery. METHODS: We performed redo single coronary artery bypass grafting to the left anterior descending coronary artery in 9 patients and to the right coronary artery in 3 patients using minimally invasive cardiac surgery. The graft to the left anterior descending coronary artery was taken from the left internal thoracic artery in 5 patients, the right gastroepiploic artery in 3 patients, and from the saphenous vein in the other 1 patient. The graft to the right coronary artery was from the right gastroepiploic artery in all 3 patients. RESULTS: All grafts were patent. There was no major postoperative complication and no surgical or hospital death except one late death. CONCLUSIONS: In selected patients, we could safely and completely perform coronary artery bypass re-grafting to the left descending coronary artery or right coronary artery using a minimally invasive operation.  相似文献   
67.
Six knees from cadavers were tested for change in stability after release of the medial collateral ligament with posterior cruciate-retaining and substituting total knee replacements. Load deformation curves of the joint were recorded in full extension and 30 degrees, 60 degrees, and 90 degrees flexion under a 10 N-m varus and valgus torque, 1.5 N-m internal and external rotational torque, and a 35 N anterior and posterior force to test stability in each knee. The intact specimen and posterior cruciate ligament-retaining total joint replacement were tested for baseline comparisons. The superficial medial collateral ligament was released, followed by release of the posterior cruciate ligament. The knee then was converted to a posterior-stabilized implant. After medial collateral ligament release, valgus laxity was statistically significantly greater at 30 degrees, 60 degrees, and 90 degrees flexion after posterior cruciate ligament sacrifice than it was when the posterior cruciate ligament was retained. The posterior-stabilizing post added little to varus and valgus stability. Small, but significant, differences were seen in internal and external rotation before and after posterior cruciate ligament sacrifice. The posterior-stabilized total knee arthroplasty was even more rotationally constrained in full extension than the knee with intact medial collateral ligament and posterior cruciate ligament.  相似文献   
68.
Radical prostatectomy is the only potential modality for cure in patients with localized prostate cancer. However, the lack of reliable and accurate clinical staging frequently leads to incomplete excision of tumor, with the consequences of early local recurrence or distant metastasis. Thus, the role of neoadjuvant or adjuvant hormonal treatment has been investigated in improving disease-free or cause-specific survival. This review reports the current status and problems of such androgen deprivation in combination with radical prostatectomy for localized prostate cancer.  相似文献   
69.
70.
OBJECTIVES: Vascular endothelial growth factor (VEGF) is considered to play critical roles in tumor development and progression, especially in renal cell carcinoma (RCC) via von Hippel-Lindau gene inactivation. Although VEGF -2578CC, -1154GG, and -634CC genotypes are reportedly correlated with higher levels of VEGF production, no previous studies have reported on the associations of these polymorphisms with RCCs. This study was aimed to clarify the effects of these functional polymorphisms on RCC progression and prognosis. METHODS: We investigated the associations of three polymorphisms (-2578C/A, -1154G/A, and -634C/G) in the VEGF gene with the clinicopathologic parameters and survival of 213 patients with RCC. The -2578C/A and -634C/G polymorphisms were genotyped using a polymerase chain reaction (PCR) restriction fragment length polymorphism technique and the -1154G/A polymorphism was genotyped by an amplification refractory mutation system PCR technique. RESULTS: The GA+AA genotypes of -1154G/A were weakly associated with smaller tumors, lower tumor stage, and lower stage grouping (p=0.028, p=0.012, and p=0.028, respectively). The CA and CA+AA genotypes of -2578C/A were weakly associated with less frequent lymph node metastasis (p=0.029 and p=0.034, respectively) and were significantly associated with favorable cancer-specific survival (p=0.047 and p=0.048, respectively). There was no apparent clinical effect of the -634C/G polymorphism. CONCLUSIONS: These results suggest that some VEGF genotypes may have effects on RCC progression or prognosis, possibly through altered VEGF expression. This finding might help in clarifying the mechanisms of RCC development and progression.  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