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   36203篇
  免费   2391篇
  国内免费   358篇
耳鼻咽喉   596篇
儿科学   559篇
妇产科学   477篇
基础医学   6019篇
口腔科学   668篇
临床医学   2922篇
内科学   7227篇
皮肤病学   1182篇
神经病学   2992篇
特种医学   1907篇
外科学   5089篇
综合类   169篇
现状与发展   2篇
一般理论   7篇
预防医学   1461篇
眼科学   783篇
药学   3264篇
中国医学   455篇
肿瘤学   3173篇
  2023年   302篇
  2022年   836篇
  2021年   1409篇
  2020年   637篇
  2019年   971篇
  2018年   1085篇
  2017年   840篇
  2016年   1256篇
  2015年   1613篇
  2014年   1866篇
  2013年   2117篇
  2012年   3228篇
  2011年   3052篇
  2010年   1742篇
  2009年   1439篇
  2008年   2206篇
  2007年   2021篇
  2006年   1880篇
  2005年   1679篇
  2004年   1459篇
  2003年   1247篇
  2002年   1092篇
  2001年   755篇
  2000年   701篇
  1999年   559篇
  1998年   266篇
  1997年   200篇
  1996年   171篇
  1995年   166篇
  1994年   135篇
  1993年   113篇
  1992年   209篇
  1991年   194篇
  1990年   164篇
  1989年   158篇
  1988年   130篇
  1987年   127篇
  1986年   109篇
  1985年   106篇
  1984年   68篇
  1983年   69篇
  1982年   34篇
  1981年   31篇
  1980年   37篇
  1979年   65篇
  1978年   32篇
  1976年   34篇
  1972年   31篇
  1971年   34篇
  1969年   31篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
A 78-year-old woman with diagnosis of acute myocardial infarction (AMI) in the anteroseptal area fell into cardiogenic shock suddenly just before starting percutaneous coronary intervention (PCI). Echocardiography showed left ventricular free wall rupture, then an emergent operation was performed by sutureless patch repair using collagen fleece with fibrinogen-based impregnation. Eight days later from the initial operation, the onset of ventricular septal perforation (VSP) was recognized. Fifteen days after, the infarct exclusion technique with endocardial patch was performed. She has been doing well 4 months after the operation without residual shunt. To our best knowledge, this is the first surgical case report that free wall rupture of left ventricle and VSP which are serious complications after myocardial infarction happened in succession.  相似文献   
42.
43.
Symptomatic liver cyst: Special reference to surgical management   总被引:2,自引:0,他引:2  
We conducted a retrospective study of 14 patients with symptomatic liver cysts to evaluate current therapeutic interventions for this condition. Abdominal pain (n = 7) or abdominal mass (n = 5) were the most frequent presentations. Three patients also had renal cyst. Percutaneous aspiration with ethanol sclerotheraphy was carried out in 4 patients and all cysts so treated diminished in size, with relief of the symptoms. One patient was treated by aspiration only and re-retension occurred. Cystectomy was performed in 2 patients, unroofing in 5, and fenestration in 2 patients. All patients gained relief of symptoms, with no recurrence of symptoms. Computed tomography revealed that the cysts were diminished or were no longer observable after all the treatments. Our experience indicates that unroofing, fenestration, and cystectomy are safe and suitable procedures for treatment of the condition. Ethanol sclerotherapy may be a feasible alternative to surgical intervention in selected patients. Received for publication on July 23, 1997; accepted on Dec. 25, 1997  相似文献   
44.
Carbohydrate analysis is important in studying structure and activity of complex polysaccharides. New analytical method was applied to get an information on the composition of polysaccharides showing antitumor activity. Monosaccharides were labeled with 7-amino-1,3-naphthalenedisulfonic acid (7-AGA) by reductive amination and separated by HPLC. Five kinds of polysaccharides fromBasidiomycetes were hydrolyzed and analyzed in combination with electrophoresis and HPLC. At the same time, alditol acetate derivatives were prepared and analyzed by gas chromatography. Two different techniques using different derivatization methods showed very similiar results. The monosaccharides fromCoriolus versicolor andLentinus eodes were mainly composed of D-glucose, while those fromGanoderma lucidium andCordyceps militaris were glucose and galactose.Phellinus linteus composed of glucose, galactose, mannose, arabinose and fucose. The HPLC method with fluorescence detector was very sensitive compared to other methods.  相似文献   
45.
46.
The role of cadaver kidney transplantation in the management of end-stage renal disease in young children is controversial. To assess the current risk-benefit ratio of cadaver first and second kidney transplants in recipients under 6 years of age, we compared the outcome of 19 transplants performed between 1984 and 1989 using a quadruple-drug regimen (Minnesota antilymphocyte globulin, azathioprine, prednisone, cyclosporine) with the outcome of 25 transplants performed prior to 1984 without the use of cyclosporine at a single institution. Twenty-five transplants were in children under the age of 3 years. In the last decade patient survival has significantly improved. One-year patient survival improved from 53% before 1979 to 90% since 1979 (P less than 0.05). The use of the quadruple-drug regimen since 1984 was associated with a significant improvement in one-year cadaver graft function from 40% before 1979 to 78% in recipients under 6 years of age, and from 22% to 82% in recipients under 3 years of age (P less than 0.05). With the quadruple-drug regimen, one-year and four-year graft function rates for children under 6 years of age were 83% for first cadaver transplants and 72% for second cadaver transplants, which were essentially the same results as in older children and adults. Children who received kidneys from donors over 4 years of age achieved the best result, with 87% one-year graft function compared with 50% for kidneys from donors under 4 years old. In 15 children with successful transplants, 8 (53%) showed accelerated growth, 5 (33%) had normal-velocity growth, and only 2 children (14%) with suboptimal renal function had poor growth following transplantation. Therefore, we believe that with a quadruple-drug immunosuppressive protocol, cadaver renal transplantation using kidneys from adults or pediatric donors over 4 years old is an acceptable form of treatment in young children with end-stage renal disease for whom there are no suitable living-related donors.  相似文献   
47.
48.
To evaluate the possibility of radionuclide gene therapy and imaging in hepatocellular carcinoma cancer, we investigated the iodine accumulation of a human hepatocellular carcinoma cell line, SK-Hep1, by transfer of human sodium iodide symporter (hNIS) gene. By targeting NIS expression in SK-Hep1, we could also investigate whether these cells concentrate 99mTc-pertechnetate and 188Re-perrhenate as well as 125I in vitro and in vivo. METHODS: The hNIS gene was transfected to human hepatocellular carcinoma SK-Hep1 cell lines using lipofectamine plus reagent. The uptake and efflux of 125I, 99mTc-pertechnetate, and 188Re-perrhenate were measured in the transfected and parental cells. Biodistribution was studied in nude mice bearing SK-Hep1 and SK-Hep1-NIS at 10 and 30 min and at 1, 2, 6, 16, and 23 h after injection of 125I, 99mTc- pertechnetate, or 188Re-perrhenate. In tumor imaging studies, the nude mice were intravenously injected with 188Re-perrhenate and imaged with a gamma-camera equipped with a pinhole collimator at 30 and 60 min after injection. The survival rate (%) was determined by the clonogenic assay after 37 MBq/10 mL (1 mCi/10 mL) 131I and 188Re-perrhenate treatment. RESULTS: SK-Hep1-NIS, stably expressing the NIS gene, accumulated 125I up 150 times higher than that of SK-Hep1. Iodine uptake of SK-Hep1-NIS is completely blocked by perchlorate. NIS gene transfection into SK-Hep1 also resulted in 112- and 87-fold increases of 99mTc-pertechnetate and 188Re-perrhenate uptake, respectively. Iodide efflux from SK-Hep1-NIS was relatively slow, with only 10% released during the initial 5 min, and 60% remained at 25 min. In the biodistribution study using SK-Hep1-NIS-xenographed mice, the tumor uptake of 125I, 188Re-perrhenate, and 99mTc-pertechnetate was 68.0 +/- 15.0, 46.2 +/- 9.1, and 59.6 +/- 16.2 %ID/g (percentage injected dose per gram) at 2 h after injection, respectively. After 188Re-perrhenate injection in SK-Hep1 and SK-Hep1-NIS-xenographed nude mice, whole-body images clearly visualized the SK-Hep1-NIS tumor, whereas the control tumor was not visualized. The survival rate (%) of SK-Hep1-NIS was markedly reduced to 46.3% +/- 10.1% and 28.9% +/- 5.2% after 37 MBq/mL (1 mCi/10 mL) 131I and 188Re-perrhenate treatment compared with the survival rates of the parental cells. These results demonstrated that SK-Hep1-NIS could be selectively killed by the induced 131I and 188Re-perrhenate accumulation through NIS gene expression. CONCLUSION: NIS-based gene therapy using beta-emitting radionuclides has the potential to be used in hepatocellular carcinoma management.  相似文献   
49.
There have been a few studies and inconsistent results regarding the coincidence of Parkinson's disease (PD) and atherosclerotic diseases, such as cerebrovascular disease. Carotid intima-media thickness (IMT) is a known marker for subclinical atherosclerosis. The aim of this study was to investigate the carotid IMT between PD patients and controls. We studied 43 patients with PD and 86 matched controls. The carotid IMT in PD patients was significantly smaller than in controls (0.796 +/- 0.179 mm vs. 0.913 +/- 0.237 mm, P < 0.05). In multivariate analysis, the carotid IMT was inversely associated with the duration of levodopa medication and the severity of PD. These results suggest that PD patients have a lower risk of atherosclerosis.  相似文献   
50.
OBJECTIVES: Graft failure has been reported when the arterial conduit, such as the internal thoracic artery (ITA) or the right gastroepiploic artery (GEA), is grafted to a lower grade coronary artery stenosis. The shear stress as a significant factor affecting graft patency was compared between the arterial conduit and the saphenous vein graft (SVG) after surgery. METHODS: In 101 patients, 40 ITAs, 27 GEAs and 34 SVGs were examined using a Doppler-tipped guide wire during postoperative angiography. The graft flow volume and shear stress were calculated from velocity and diameter data. The study grafts were classified according to the grade of native coronary artery stenosis: group L had more than 50 up to 75% stenosis, and group H had more than 75% stenosis. Group H consisted of 25 ITAs, 17 GEAs and 21 SVGs, while group L consisted of 15 ITAs, 10 GEAs and 13 SVGs. RESULTS: In group H, graft flow volume did not significantly differ among the ITA (34+/-11 ml/min), GEA (36+/-16 ml/min) and SVG (41+/-15 ml/min), and graft shear stress significantly (ITA vs. GEA P<0.0001; GEA vs. SVG P<0.01) differed among the ITA (16.0+/-4.8dyn/cm(2)), GEA (9.1+/-3.2dyn/cm(2)) and SVG (4.8+/-1.6dyn/cm(2)). In group L, flow volume was lower (P<0.001) in the ITA (18+/-6 ml/min) and GEA (13+/-8 ml/min) than in the SVG (35+/-16 ml/min), and shear stress was significantly (P<0.001) greater in the ITA (13.7+/-4.9dyn/cm(2)) than the GEA (5.6+/-2.0dyn/cm(2)) or SVG (4.6+/-2.0dyn/cm(2)). CONCLUSIONS: These data suggest that shear stress of the ITA is superior and maintained despite the flow volume being reduced by flow competition. Lower shear stress of the GEA for intermediate stenosis may be associated with the development of conduit failure.  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