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   12871篇
  免费   679篇
  国内免费   83篇
耳鼻咽喉   139篇
儿科学   247篇
妇产科学   165篇
基础医学   1497篇
口腔科学   282篇
临床医学   843篇
内科学   3482篇
皮肤病学   176篇
神经病学   828篇
特种医学   576篇
外科学   2350篇
综合类   82篇
一般理论   1篇
预防医学   386篇
眼科学   301篇
药学   693篇
中国医学   33篇
肿瘤学   1552篇
  2023年   81篇
  2022年   160篇
  2021年   275篇
  2020年   181篇
  2019年   224篇
  2018年   301篇
  2017年   237篇
  2016年   298篇
  2015年   272篇
  2014年   407篇
  2013年   413篇
  2012年   659篇
  2011年   760篇
  2010年   475篇
  2009年   367篇
  2008年   542篇
  2007年   624篇
  2006年   636篇
  2005年   619篇
  2004年   553篇
  2003年   518篇
  2002年   514篇
  2001年   380篇
  2000年   375篇
  1999年   322篇
  1998年   139篇
  1997年   111篇
  1996年   93篇
  1995年   107篇
  1994年   86篇
  1993年   91篇
  1992年   272篇
  1991年   219篇
  1990年   219篇
  1989年   260篇
  1988年   206篇
  1987年   211篇
  1986年   194篇
  1985年   185篇
  1984年   127篇
  1983年   112篇
  1980年   46篇
  1979年   91篇
  1978年   68篇
  1977年   54篇
  1974年   43篇
  1972年   43篇
  1971年   43篇
  1970年   46篇
  1968年   50篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
Our objective was to analyze problems in the perioperative management and long-term outcome of living donor liver transplantation (LDLT) for biliary atresia (BA). Many reports have described the effectiveness of liver transplantation (LT) for BA, particularly in pediatric cases, but little information is available regarding LT in adults (> or =16 years old). Between June 1990 and December 2004, 464 patients with BA underwent LDLT at Kyoto University Hospital, of whom 47 (10.1%) were older than 16 years. In this study, we compared the outcomes between adult (> or =16 years old) and pediatric (<16 years old) patients. The incidence of post-transplant intestinal perforation, intra-abdominal bleeding necessitating repeat laparotomy and biliary leakage was significantly higher (p < 0.0001, <0.001 and <0.001, respectively) in adults. Overall cumulative 1-, 5- and 10-year survival rates in pediatric patients were significantly higher (p < 0.005) than in adults. Two independent prognostic determinants of survival were identified: a MELD score over 20 and post-transplant complications requiring repeat laparotomy. Outcome of LDLT in adult BA patients was poorer than in pediatric patients. It seems likely that LT will be the radical treatment of choice for BA and that LDLT should be considered proactively at the earliest possible stage.  相似文献   
42.
A series of 8-substituted-9,1-(epoxymethano)-7-fluoro-5-oxo-5H- thiazolo[3,2-a]quinoline-4-carboxylic acids having a novel tetracyclic structure was synthesized and tested for antibacterial activity. The nature of the heteroatom (N, O, or S) substituted at the 8-position had little influence on the antibacterial activity. Among the six pyrrolidinyl derivatives and the five piperazinyl derivatives, the 8-(3-hydroxy-1-pyrrolidinyl) derivative 6h and the hydrochloride of the 8-(4-methyl-1-piperazinyl) derivative 6l showed the most potent activity against both Gram-positive and Gram-negative bacteria. Against nalidixic acid resistant strains, isolated from Escherichia coli KC-14, compound 6h was less potent than 6l. Replacement of the piperazinyl nitrogen atom by a carbon atom, an oxygen atom, or a sulfur atom (corresponding to the piperidino, morpholino, or thiomorpholino group, respectively) enhanced the activity against Gram-positive bacteria, but reduced the activity against Gram-negative bacteria. Compound 6l also showed potent in vivo antibacterial activity against Gram-positive and Gram-negative bacteria, and did not cause convulsions in mice with the concomitant administration of fenbufen. Replacement of the carboxy group by a sulfonic acid group in 6l resulted in a complete loss of antibacterial activity.  相似文献   
43.
A 14-year-old girl was admitted because of cough, chest pain and hemosputum. Chest roentgenogram on admission showed a pneumothorax and a cavitary lesion with niveau formation in the right lung and cystic lesions in the bilateral lung fields. After bed rest and intravenous administration of antibiotics for two weeks, the right lung inflated well and the niveau formation disappeared, and the patient was discharged. One week later, she was readmitted with sudden-onset severe dyspnea, caused by bilateral pneumothoraces. Emergency tube thoracostomy and wedge resection of the bullous lesion was performed. Macroscopically, multiple small cystic changes were seen on the surface of the right lung. Histological examination revealed nodular proliferations of smooth muscle cells in the interstitium and vessel walls in the lung, which contained slit-like lymphatic channels. The diagnosis of pulmonary lymphangiomyomatosis was made. In this case, we could not measure receptors for estrogen and progesterone. Recently, hormonal therapy and oophorectomy have been reported as being useful. Tamoxifen (Norvadex) was therefore initiated, and the patient has remained well with slight dyspnea on exertion. There has been no recurrence of pneumothorax. Lymphangiomyomatosis is a rare disease of unknown etiology which occurs exclusively in women, mostly in those of reproductive age. We report a 14-year-old female patient with lymphangiomyomatosis associated with repeated pneumothorax, who had been under treatment for epilepsy. We believe this case to be of importance because of the long discussed relation between pulmonary lymphangiomyomatosis and tuberous sclerosis.  相似文献   
44.
The admission of antihypertensive medications in the elderly (65 y.o. or more, 269 pts) was compared to that in younger cases (less than 65 y.o., 348 pts). All were outpatients who visited our clinic in 1990. The number of patients on a single therapeutic regimen was almost equal in both age groups. Once-a-day regimens were more common in the young (56.9% vs 48.3%, p less than 0.05), and three times-a-day regimens were more common in the elderly (14.7% vs 23.1%, p less than 0.01). The choice of antihypertensive drugs in patients with single therapy or combined therapy in the young was beta blockers in 49.7%, Ca blockers in 39.4%, diuretics in 30.7% and ACE inhibitors in 17.8%, and those in the elderly were Ca blockers in 46.1%, diuretics in 44.2%, beta blockers in 33.8%, and ACE inhibitors in 16.4%. The patients were subdivided into three groups according to the time of the initial visit to the clinic; initial visit during 1969-1979 (phase 1), 1980-1984 (phase 2) and 1985-1990 (phase 3). In the young, choice of beta blockers and diuretics was most popular in phase 1. However, the choice of diuretics decreased in phase 2, and in phase 3 beta blockers were used in 50.4%, Ca blockers in 43.2%, ACE inhibitors in 22.3% and diuretics in only 17.3%. In the elderly, diuretics were most popular followed by Ca blockers and beta blockers in phase 1 and phase 2. In phase 3 Ca blockers were selected in 58.2% followed by both beta blockers and ACE inhibitors in 28.4% then diuretics in 23.9%.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
45.
PURPOSETo determine whether steady-state free precession sequences improve the MR visibility of epidermoid tumors in comparison with spin-echo images.METHODSPatients were four women and three men with epidermoid tumors in the subarachnoid spaces. MR was performed with a 1.5-T superconductive unit. For steady-state free precession imaging, three-dimensional Fourier transform fast imaging with steady-state free precession (FISP) images were used (20-40/7 [repetition time/echo time], flip angle of 25 degrees). The visualization and contrast-to-noise ratio were compared in FISP images and spin-echo images. In one case, the images of FISP and fast low-angle shot were obtained with variable repetition times and flip angles to evaluate the best pulse sequences for the visualization of epidermoid tumors.RESULTSThe contrast-to-noise ratios between tumors and cerebrospinal fluid ranged from 7.9 to 17.5 (average was 12.9) on FISP images. The average of contrast-to-noise ratios on T1, T2, and proton density-weighted spin-echo images were 1.6, 2.0, and 4.2, respectively. Three-dimensional Fourier transform FISP images best showed central nervous system and demonstrated epidermoid tumors excellently.CONCLUSIONSEpidermoid tumors in the subarachnoid spaces were better demonstrated on steady-state free precession (three-dimensional Fourier transform FISP) than on conventional spin-echo images.  相似文献   
46.
PURPOSETo describe MR and CT features of germinoma originating in the basal ganglia and thalamus and to discuss the roles of each modality for its diagnosis.METHODSMR and CT studies of six cases of germinomas, five of which were histologically proved, were retrospectively reviewed. T1-weighted, T2-weighted, and contrast-enhanced T1-weighted conventional spin-echo images, and unenhanced and contrast-enhanced CT images were evaluated.RESULTSTypically, the tumor consisted of an irregular solid area with contrast enhancement and various-size cysts. Cystic components were found in five cases and calcification in four. Intratumoral hemorrhage was noted in one. Ipsilateral cerebral hemiatrophy and brain stem hemiatrophy were noted in three cases each. MR was superior to CT in evaluating precise tumor extension, cystic components, and intratumoral hemorrhage, although in one case, extension of the tumor was better defined on CT in its early stage. Calcification was difficult to identify by MR alone. The solid components of the tumors generally showed slightly high density on CT, which seemed to be characteristic compared with nonspecific intensity pattern on MR.CONCLUSIONThe combination of CT and MR findings allows early detection and appropriate diagnosis of the mass in the basal ganglia and/or thalamus.  相似文献   
47.
48.
Effects of intraaortic balloon position on renal artery blood flow.   总被引:2,自引:0,他引:2  
Debate continues over what happens to renal blood flow when intraaortic balloons are adjacent to the renal arteries. Fourteen dogs were prepared by implanting instruments to measure heart rate; right atrial, pulmonary arterial, carotid arterial, and femoral arterial pressures; cardiac index; mixed venous oxygen saturation; urine output; and left and right renal blood flows. A 12-mL intraaortic balloon was inserted through the left (n = 9) or right (n = 5) femoral artery. The position of the balloon was randomized so that it was initially placed in either the control (thoracic) or renal position (at the level of the renal arteries). Intraaortic balloon pumping was performed for 4 hours in each position. In 8 dogs, at least one of the renal arteries had partial occlusion, 23% to 98% decrease in flow (mean decrease, 66%), while the intraaortic balloon was in the renal position. An intraaortic balloon in the renal position results in lower renal blood flow as well as a high risk (57%) of selective renal artery occlusion. Decreased renal blood flow is not apparent using conventional monitoring, as hemodynamics do not change.  相似文献   
49.
50.
In the present study, the results of living donor liver transplantation (LDLT) for 125 hepatocellular carcinoma (HCC) patients were analyzed to determine optimal criteria exceeding the Milan criteria (MC) but still with predictably good outcomes. On the basis of pretransplant imaging studies, 70 patients met the MC, and 55 patients did not. Patients who exceeded the MC but presented with 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