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   127814篇
  免费   7211篇
  国内免费   1098篇
耳鼻咽喉   1954篇
儿科学   1970篇
妇产科学   1880篇
基础医学   20307篇
口腔科学   3102篇
临床医学   11928篇
内科学   22879篇
皮肤病学   3979篇
神经病学   10329篇
特种医学   7489篇
外科学   16665篇
综合类   552篇
现状与发展   3篇
一般理论   27篇
预防医学   6716篇
眼科学   3195篇
药学   11427篇
中国医学   1460篇
肿瘤学   10261篇
  2023年   912篇
  2022年   2716篇
  2021年   4401篇
  2020年   2110篇
  2019年   2949篇
  2018年   3695篇
  2017年   2998篇
  2016年   3916篇
  2015年   5451篇
  2014年   6460篇
  2013年   7520篇
  2012年   11255篇
  2011年   10789篇
  2010年   6198篇
  2009年   5344篇
  2008年   7552篇
  2007年   7159篇
  2006年   6474篇
  2005年   5983篇
  2004年   5218篇
  2003年   4549篇
  2002年   3912篇
  2001年   3045篇
  2000年   2795篇
  1999年   2148篇
  1998年   954篇
  1997年   718篇
  1996年   571篇
  1995年   498篇
  1994年   431篇
  1993年   378篇
  1992年   758篇
  1991年   702篇
  1990年   652篇
  1989年   588篇
  1988年   493篇
  1987年   497篇
  1986年   364篇
  1985年   391篇
  1984年   276篇
  1983年   200篇
  1982年   153篇
  1981年   182篇
  1980年   135篇
  1979年   224篇
  1978年   166篇
  1977年   129篇
  1976年   143篇
  1975年   133篇
  1974年   139篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Koo KH  Ahn IO  Kim R  Song HR  Jeong ST  Na JB  Kim YS  Cho SH 《Radiology》1999,211(3):715-722
PURPOSE: To determine the accuracy of magnetic resonance (MR) cholangiography for demonstration of the biliary tract and detection of biliary complications in patients who have undergone orthotopic liver transplantation. MATERIALS AND METHODS: Breath-hold half-Fourier rapid acquisition with relaxation enhancement MR cholangiography was performed in 25 patients who had undergone orthotopic liver transplantation. MR cholangiograms were prospectively and independently interpreted by two radiologists for depiction of the biliary tract and ductal anastomosis and for complications (eg, biliary dilatation, stricture, stones). MR cholangiographic findings were correlated with findings from direct cholangiography (n = 24) and surgery (n = 1). RESULTS: MR cholangiography completely demonstrated first-order intrahepatic bile ducts in 23 (92%) patients, the donor extrahepatic bile duct in 25 (100%), the recipient extrahepatic bile duct in 17 of 18 (94%), and the anastomosis in 24 (96%). The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of MR cholangiography for detection of biliary dilatation and stricture were each 100%. Complete interobserver agreement occurred in the detection of biliary dilatation and stricture. The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of MR cholangiography for detection of stones were 100% for one radiologist and 86%, 100%, 96%, 100%, and 95%, respectively, for the other. Both radiologists agreed on the diagnosis of bile duct stones in six of seven cases (kappa = 0.90). CONCLUSION: MR cholangiography enables accurate depiction of the biliary tract and detection of biliary complications in patients with an orthotopic liver transplant.  相似文献   
992.
We report the transrectal ultrasonographic (TRUS) and endorectal surface coil MR findings for paragonimiasis involving the perirectal space. The patient presented with voiding difficulty. TRUS showed a well demarcated, oval-shaped hyperechoic mass in the perirectal space. On endorectal MR images, the lesion was depicted as a well defined cystic mass with homogeneous intermediate signal intensity on T1-weighted images and heterogeneous hyperintensity on T2-weighted images. Ectopic paragonimiasis can appear as a well defined cystic mass in the peritoneum and should be included in the differential diagnosis of cystic mass in the abdomen and pelvic cavity, including the perirectal space.  相似文献   
993.
PURPOSE: The purpose of this work was to describe the radiologic findings of pulmonary tuberculosis in patients who presented with acute respiratory failure. METHODS: We included patients who had newly diagnosed active pulmonary tuberculosis and who presented with acute respiratory failure. Initial chest radiographic (n = 17) and high-resolution CT (n = 11) findings of each patient were analyzed retrospectively. RESULTS: Of 1,010 patients with active pulmonary tuberculosis, 17 patients (1.7%) presented with acute respiratory failure. Nine (53%) of the 17 patients died. The most common initial chest radiographic findings were small nodular lesions (16/17; 94%), consolidation (13/17; 76%), and ground-glass opacity (12/17; 70%). Eleven (69%) of 16 nodular lesions, 9 of 13 (69%) consolidations, and 10 of 12 (83%) ground-glass opacities were bilateral. On HRCT (n = 11), miliary micronodular lesions were seen in 6 patients (55%), whereas bronchogenic spread of tuberculosis with disseminated centrilobular nodules and tree-in-bud appearance was seen in 5 patients (45%). Diffuse areas of ground-glass attenuation were seen in all six patients with miliary nodules and four of five patients with bronchogenic spread of tuberculosis. CONCLUSION: Patients with pulmonary tuberculosis occasionally present with acute respiratory failure. In this condition, chest radiograph most commonly shows bilateral small nodular lesions mixed with consolidation or ground-glass opacity, whereas HRCT demonstrates findings of miliary or bronchogenic disseminated tuberculosis with diffuse areas of ground-glass attenuation.  相似文献   
994.
Lee KS  Han BH  Chun YK  Kim HS  Kim EE 《Clinical imaging》1999,23(6):1183-346
This retrospective study correlated the mammographic manifestations and averaged nuclear grades using Holland, Van-Nuys, and Lagios classifications in 37 cases of ductal carcinoma in situ (DCIS); microcalcifications alone were seen in 59.4%, microcalcifications with associated mass in 19%, and mass alone in 21.6%. DCIS is more likely to be accompanied by microcalcifications than mass on mammography. Correlation is good between the nuclear grades of DCIS and mammographic manifestations.  相似文献   
995.
RATIONALE AND OBJECTIVES: The purpose of the study was to evaluate a method of producing obstruction of the common bile duct and concomitant biliary duct dilatation in an animal model. MATERIALS AND METHODS: Laparoscopic placement of a double-balloon occlusion device was used to produce common bile duct obstruction and bile duct dilatation in pigs. RESULTS: One week after the procedure, common bile duct obstruction and dilatation of the biliary tree were demonstrated with either percutaneous transhepatic cholangiography or percutaneous cholecystography. CONCLUSION: The use of this method is technically feasible and provides a useful subacute and chronic animal model of common bile duct obstruction and dilatation of the biliary tree for percutaneous interventional training and research purposes.  相似文献   
996.
997.
BACKGROUND/PURPOSE: Hepatotrophic factors in the portal blood are critically important for the survival of heterotopically transplanted hepatocytes. Currently, no model exists for the implantation of hepatocytes on biodegradable polymer scaffolds with direct access to the portal blood. This study investigates the use of small intestinal submucosa (SIS) as a small-caliber venous conduit that may be used for the implantation of tissue-engineered liver. METHODS: SIS was prepared from segments of rat jejunum and implanted as a venous conduit between the portal vein and inferior vena cava in 26 heparinized Lewis rats. Venograms were performed periodically, and the grafts were harvested at various time-points and examined by scanning electron microscopy (SEM) and histology. Von Willebrand Factor (vWF) staining was performed to assess endothelialization. RESULTS: Five rats died of technical complications. Seventeen of 21 rats (81%) maintained patent grafts at the time of death up to 8 weeks. Venograms demonstrated patent grafts at 3 and 8 weeks. SEM results showed a smooth luminal surface with endothelial-like cells by 3 weeks. Histology demonstrated a confluent luminal endothelial monolayer, absence of thrombus, and neovascularization in the SIS graft. VWF staining results were positive, confirming the growth of endothelial cells on the luminal surface. In preliminary studies, implantation of hepatocytes seeded on biodegradable polymer tubes into the SIS graft demonstrated clusters of viable cells after 2 days. CONCLUSIONS: Rat SIS can be prepared readily, maintains high patency as a small-caliber venous graft, and may be a useful model for the transplantation of tissue-engineered liver with access to the portal circulation.  相似文献   
998.
To avoid a high-risk operation on a moribund neonate with a ruptured hepatic tumor, transumbilical embolization of the bleeding tumor was attempted in a 2-day-old neonate. A 3F microferret catheter was advanced through the right umbilical artery. After identifying the left hepatic artery feeding the bleeding tumor, Gelfoam (Upjohn, Kalamazoo, MI) particles were injected. Bleeding was successfully controlled. The infant was able to tolerate enteral feeding when stable. Seventeen days after embolization, elective left hepatic lobectomy was performed. Histological examination showed a fetal epithelial type hepatoblastoma. The baby is 13 months old now and is receiving chemotherapy.  相似文献   
999.
1000.
We report a rare case of thoracic intramedullary schwannoma. The patient, a 37-year-old woman, showed no evidence of neurofibromatosis. The possible etiology and treatment of the tumor are discussed and a review of literature is presented.  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