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   3826篇
  免费   194篇
  国内免费   32篇
耳鼻咽喉   15篇
儿科学   105篇
妇产科学   30篇
基础医学   443篇
口腔科学   77篇
临床医学   313篇
内科学   1052篇
皮肤病学   56篇
神经病学   257篇
特种医学   112篇
外科学   808篇
综合类   22篇
预防医学   76篇
眼科学   14篇
药学   271篇
中国医学   30篇
肿瘤学   371篇
  2023年   25篇
  2022年   30篇
  2021年   94篇
  2020年   67篇
  2019年   72篇
  2018年   88篇
  2017年   67篇
  2016年   62篇
  2015年   72篇
  2014年   107篇
  2013年   122篇
  2012年   223篇
  2011年   227篇
  2010年   108篇
  2009年   96篇
  2008年   208篇
  2007年   184篇
  2006年   191篇
  2005年   230篇
  2004年   208篇
  2003年   179篇
  2002年   185篇
  2001年   72篇
  2000年   88篇
  1999年   85篇
  1998年   67篇
  1997年   51篇
  1996年   41篇
  1995年   43篇
  1994年   35篇
  1993年   35篇
  1992年   62篇
  1991年   59篇
  1990年   61篇
  1989年   54篇
  1988年   45篇
  1987年   48篇
  1986年   37篇
  1985年   42篇
  1984年   32篇
  1983年   32篇
  1982年   17篇
  1981年   12篇
  1979年   19篇
  1978年   20篇
  1977年   19篇
  1974年   14篇
  1973年   13篇
  1971年   16篇
  1970年   19篇
排序方式: 共有4052条查询结果,搜索用时 15 毫秒
91.
A 76-year-old male patient with jaundice was diagnosed as having hepatic hilar cholangiocarcinoma. The patient underwent percutaneous transhepatic biliary drainage of the left and the right intrahepatic bile duct. He could not have a percutaneous transhepatic endoprosthesis placed because it was impossible to pass the guidewire through the stenotic portion of the lesion. The patient was operated, but the tumor was considered to be unresectable. Along the intrahepatic routes formed by the preexisting two percutaneous transhepatic biliary drainage tubes, silicon tubes were inserted. Through the lumen of a long jejunal limb, Roux-en-Y, the tubes with five to six side holes were passed in the distal direction and drawn out from the lumen of the jejunal limb and passed through the abdominal wall to outside. The tubes were occluded and buried in the subcutaneous space after a few clamping tests. He died of liver failure in his house four months after the operation without any symptoms of jaundice, fever or of obstruction of the tubes.  相似文献   
92.
We describe a gastric carcinoma cell line that has been maintained in vitro for more than 10 years and retains the capacity to produce a large amount of alpha-fetoprotein. This cell line was isolated from a metastatic lymph node of a 63-year-old male patient with advanced gastric carcinoma (T2N3P0H0M0) who showed high serum levels of alpha-fetoprotein. The primary tumor was moderately differentiated tubular adenocarcinoma and the lymph node was poorly differentiated adenocarcinoma without any particular pattern. The cultured cells grew as densely packed islet-like colonies with small polygonal cells. Electron microscopy revealed cells abundant in cytoplasmic organelles, with some cellular attachments being tight with junctional complexes and some being loose across intercellular spaces. The free cell surface had microvilli. The population doubling-time was 152 h at passage 58. Chromosomal analysis revealed the modal number to be 77, with numerous karyotype abnormalities. The tumorigenicity of the cultured cells in athymic nude mice was positive only when they were subcutaneously transplanted beneath a plastic plate, but when the cells were transplanted subcutaneously or administered by intrasplenic injection in intact or weakly irradiated nude mice, no tumorigenicty was shown. The cell line produced tumor-associated antigens, such as alpha-fetoprotein, carcinoembryonic antigen, and tissue polypeptide antigen. This cell line may be useful for comparative studies of different types of gastric carcinoma and alpha-fetoproteins of different origins.  相似文献   
93.
Annals of Nuclear Medicine - Although previous studies have investigated age and gender effects on striatal subregional dopamine transporter (DaT) binding, these studies were mostly based on a...  相似文献   
94.
Incidence of human parvovirus B19 DNA detection in blood donors   总被引:2,自引:0,他引:2  
Summary. 1000 serum samples from blood donors were tested for human parvovirus B19 (B19) DNA by a nested PCR assay: six samples were positive for B19 DNA. The frequency was 1/167 (0-6%), considerably higher than previous surveys (0-004-0-03%). Five of the six samples were also positive for anti-B19 IgM, indicating an acute phase of infection. It is recommended to screen for B19 DNA in blood products to prevent transfusion mediated viral infection for those susceptible such as immunocompromised patients and pregnant women.  相似文献   
95.
The mechanisms that are responsible for the development of myocardial fibrosis in inflammatory cardiomyopathy are unknown. We have previously generated lines of transgenic mice with cardiac-restricted overexpression of tumor necrosis factor (MHCsTNF mice), a pro-inflammatory cytokine. The MHCsTNF mice develop a heart failure phenotype that is characterized by progressive myocardial fibrosis, as well as increased levels transforming growth factor-β (TGF-β)(mRNA and protein. In order to determine whether TGF-β-mediated signaling was responsible for the myocardial fibrosis observed in the MHCsTNF mice, we treated MHCsTNF and littermate control mice from 4 to 12 weeks of age with a novel orally available TGF-β receptor antagonist (NP-40208). At the time of terminal study, myocardial collagen content was determined using the picrosirius red technique, and left ventricular (LV) systolic and diastolic function were determined using the Langendorff method. Treatment with NP-40208 resulted in a significant (P < 0.05) 65% decrease in nuclear translocation of Smad 2/3, a significant (P < 0.05), decrease in the heart-weight to body-weight ratio from 6.5 to 5.7, a ∼37% decrease in fibrillar collagen content (P < 0.01) and a significant (P < 0.05) decrease in the LV chamber stiffness by ∼25% in the MHCsTNF mice when compared to diluent-treated controls. Treatment with NP-40208 had no discernable effect on LV systolic function, nor any effect on cardiac myocyte size or fetal gene expression in the MHCsTNF mice. Taken together, these observations suggest that sustained pro-inflammatory signaling in the adult heart is associated with a pro-fibrotic phenotype that arises, at least in part, from TGF-β-mediated signaling, with resultant activation of Smad 2/3, leading to increased myocardial fibrosis and increased LV diastolic chamber stiffness. Returned for 1. revision: 29 August 2007 1. Revision received: 24 September 2007  相似文献   
96.
Bilateral coronary artery fistula constitutes an uncommon subgroup of coronary artery fistulas that may have a distinct embryologic origin. Coronary artery fistulas usually show a tortuous arrangement upon coronary angiography, but aneurysmal dilatation is rare. We report here an extremely rare case of coronary artery fistula originating from both coronary arteries, which showed multicystic aneurysmal dilatation.  相似文献   
97.
A case of solitary neurofibroma in the retroperitoneum involving the uncinate process of the pancreas, which has been reported in only one case in Japan and less than 20 cases in the world literature, is described. A 57-year-old male complained of back pain and microhematuria. Plain and enhanced abdominal computed tomography (CT) indicated an 8 × 6 cm hypovasular tumor located in the uncinate process. We initially assumed it to be a cancer of the pancreas. His physical examination and blood chemistry result were normal. Various diagnostic imaging methods however, disclosed a rare type of tumor. The tumor was resected by pancreaticoduodenectomy and histological examination revealed it to be neurofibroma.  相似文献   
98.
We have shown previously that Cyp11b1, an 11beta-hydroxylase responsible for glucocorticoid biosynthesis in the adrenal gland, was induced by cAMP in androgen-producing Leydig-like cells derived from mesenchymal stem cells. We found that Cyp11b1 was induced in male Leydig cells, or female theca cells, when human chorionic gonadotropin was administered in immature mice. Expression of Cyp11b1 in rodent gonads caused the production of 11-ketotestosterone (11-KT), a major fish androgen, which induces male differentiation or spermatogenesis in fish. As in teleosts, plasma concentrations of 11-KT were elevated in human chorionic gonadotropin-treated mice. In contrast to teleosts, however, plasma concentrations of 11-KT were similar in both sexes, despite levels of testosterone, a precursor substrate, being about 20 times higher in male mice. Because expression of 11beta-hydroxysteroid dehydrogenase type 2, was much higher in the mouse ovary than in the testis, conversion of testosterone into 11-KT may occur more efficiently in the ovary. In a luciferase reporter system that was responsive to and activated by androgens, 11-KT efficiently activated mammalian androgen receptor-mediated transactivation. Our results suggest that the androgen metabolic pathway is conserved between teleosts and mammals, despite sexual dominance and reproductive functions of 11-KT being altered during evolution.  相似文献   
99.
INTRODUCTION: Most idiopathic nonreentrant ventricular tachycardia (VT) and ventricular premature contractions (VPCs) arise from the right or left ventricular outflow tract (OT). However, some right ventricular (RV) VT/VPCs originate near the His-bundle region. The aim of this study was to investigate ECG characteristics of VT/VPCs originating near the His-bundle in comparison with right ventricular outflow tract (RVOT)-VT/VPCs. METHODS AND RESULTS: Ninety RV-VT/VPC patients underwent catheter mapping and radiofrequency ablation. ECG variables were compared between VT/VPCs originating from the RVOT and near the His-bundle. Ten patients had foci near the His-bundle (HIS group), with the His-bundle local ventricular electrogram preceding the QRS onset by 15-35 msec (mean: 22 msec) and His-bundle pacing produced a nearly identical ECG to clinical VT/VPCs. The HIS group R wave amplitude in the inferior leads (lead III: 1.0 +/- 0.6 mV) was significantly lower than that of the RVOT group (1.7 +/- 0.4 mV, P < 0.05). An R wave in aVL was present in 6 of 10 HIS group patients, while almost all RVOT group patients had a QS pattern in aVL. Lead I in HIS group exhibited significantly taller R wave amplitudes than RVOT group. HIS group QRS duration in the inferior leads was shorter than that of the RVOT group. Eight of 10 HIS group patients exhibited a QS pattern in lead V1 compared to 14 of 81 RVOT group patients. HIS group had larger R wave amplitudes in leads V5 and V6 than RVOT group. CONCLUSION: VT/VPCs originating near the His-bundle have distinctive ECG characteristics. Knowledge of the characteristic QRS morphology may facilitate catheter mapping and successful ablation.  相似文献   
100.
Ultraviolet (UV)-induced unscheduled DNA synthesis of xeroderma pigmentosum cells, belonging to complementation groups A, B, C, D, and E, was restored to the normal level by concomitant treatment of the cells with T4 endonuclease V and UV-inactivated HVJ (Sendai virus). The present results suggest that (1) T4 endonuclease molecules were inserted effectively into the cells by the interaction of HVJ with the cell membranes, (2) the enzyme was functional on human chromosomal DNA which had been damaged by UV irradiation in the viable cells, (3) all the studied groups of xeroderma pigmentosum ("variant" was not tested) were defective in the first step (incision) of excision repair.  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