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   224篇
  免费   84篇
  国内免费   3篇
耳鼻咽喉   1篇
儿科学   14篇
妇产科学   7篇
基础医学   35篇
口腔科学   25篇
临床医学   27篇
内科学   70篇
皮肤病学   7篇
神经病学   21篇
特种医学   24篇
外科学   25篇
综合类   10篇
预防医学   18篇
眼科学   7篇
药学   12篇
肿瘤学   8篇
  2020年   2篇
  2015年   2篇
  2014年   3篇
  2013年   3篇
  2012年   3篇
  2011年   2篇
  2010年   5篇
  2009年   7篇
  2008年   7篇
  2007年   5篇
  2006年   7篇
  2005年   5篇
  2004年   4篇
  2003年   6篇
  2002年   6篇
  2001年   8篇
  2000年   4篇
  1999年   8篇
  1998年   11篇
  1997年   15篇
  1996年   20篇
  1995年   14篇
  1994年   15篇
  1993年   9篇
  1992年   6篇
  1991年   6篇
  1990年   7篇
  1989年   13篇
  1988年   11篇
  1987年   10篇
  1986年   10篇
  1985年   17篇
  1984年   12篇
  1983年   6篇
  1982年   2篇
  1981年   3篇
  1980年   6篇
  1979年   4篇
  1978年   3篇
  1977年   3篇
  1976年   2篇
  1974年   3篇
  1973年   1篇
  1972年   1篇
  1971年   3篇
  1970年   1篇
  1968年   2篇
  1966年   2篇
  1956年   1篇
  1955年   1篇
排序方式: 共有311条查询结果,搜索用时 15 毫秒
11.
Three groups of subjects, an idiot-savant group, a group of mentally handicapped subjects matched for IQ, and normal artistically gifted children, were compared for their recognition and graphic reproduction abilities. It was found that, independent of input modality, level of intelligence determined recognition performance, while graphic ability independent of IQ was the determining factor in reproduction accuracy.  相似文献   
12.
Although exposure of LLC-PK1 epithelial cell sheets to phorbol esters (TPA) causes a near immediate and total decrease of transepithelial electrical resistance (TER), continuation of exposure for 3 to 4 days results in a tachyphylactic response as TER begins to return to control levels. Recovery of TER is maximal by 5 to 6 days, but reaches only 70 to 80% of control level. A reciprocal change in the transepithelial flux of D-mannitol indicates that the TER decrease is indicative of an increase in tight junction permeability. Exposure of cell sheets to TPA for several days also results in the appearance of multilayered polyp- like foci (PLFs) across the otherwise one cell layer thick cell sheets. The pattern of penetration of the electron dense dye, ruthenium red, from the apical surface, across the tight junction and into the lateral intercellular space indicates that the tight junctions of the cell sheet become uniformly leaky after acute exposure to TPA. However, when exposure is continued for several days, only the junctions of cells in the PLFs manifest leakiness. The decrease in TER following acute TPA exposure correlates with the translocation of protein kinase C-alpha (PKC alpha) into a membrane-associated compartment. With exposure of several days, only a trace of PKC alpha is visible by Western immunoblot, and this is in the membrane-associated compartment. Immunofluorescent microscopy indicates that the trace of PKC alpha seen in the Western immunoblots is ascribable distinctly to cells of the PLFs. Monolayer areas between PLFs show no discernible immunofluorescent signal. The data therefore indicate that tight junction barrier function may be restored in certain areas by the down regulation of PKC alpha from the membrane-associated compartment. Failure to down regulate may result in the paracellular leakiness and abnormal cell architecture of the PLFs. Possible implications of this model for in vivo epithelial tumor promotion are discussed.   相似文献   
13.
Molecular analysis of PKU in Ireland   总被引:1,自引:0,他引:1  
Classical phenylketonuria (PKU: McKusick No. 261600) is caused by mutations occurring at the phenylalanine hydroxylase (PAH) locus on chromosome 12 and has a prevalence in Ireland of 1 in 4500. We examined 304 independent alleles from 350 patients for the presence of six mutations and have characterized VNTR alleles within the minisatellite region 3' to the PAH gene in patients carrying the most prevalent mutation. R408W was the most common mutation found, with a relative frequency of 42%. All other mutations had relative frequencies of <10%. VNTR analysis showed that the R408W mutation is associated with the VNTR-8 allele in the Irish population, indicating that R408W is associated with RFLP haplotype 1. This differs from that reported from eastern Europe where R408W is associated with RFLP haplotype 2/VNTR-3; an observation which has led several groups to propose a Balto-Slavic origin for this mutation. These results support the hypothesis of a second, independent founding event for the R408W mutation on an RFLP haplotype 1 VNTR-8 chromsome background in the Irish/Celtic population.  相似文献   
14.
Thirty-two patients who underwent bilateral bicompartmental Oxford Meniscal Knee arthroplasty have been followed up prospectively for a mean period of 51 months from the time of their first operation. Pain relief was obtained in all but one knee; walking ability was improved in more than two-thirds. Overall patient satisfaction with the results was good. Two knees failed. The results demonstrate that bilateral knee arthroplasty can be expected to give good functional results.  相似文献   
15.
16.
Gastrointestinal endoscopy: infection and disinfection.   总被引:4,自引:0,他引:4       下载免费PDF全文
H J O''Connor  A T Axon 《Gut》1983,24(11):1067-1077
The past decade has seen the development of an array of complex flexible fibreoptic instruments for gastrointestinal (GI) endoscopy, and an increasing use of these for diagnostic and therapeutic purposes. It has been recognised more recently that the use of contaminated endoscopic equipment can lead to serious and occasionally fatal infections. Infection with a wide variety of micro-organisms has been reported following oesophago-gastroduodenoscopy (OGD) and endoscopic retrograde cholangio-pancreatography (ERCP).  相似文献   
17.
This article describes a method of fabricating a fixed retrievable implant‐retained prosthesis based on electroforming. This method combines the advantages of both the cement‐ and screw‐retained prostheses, including passive fit, ease of fabrication, and retrievability. The absence of visible occlusal screw‐canals adds to its increased esthetic appeal.  相似文献   
18.
The beta-adrenoceptor blocking properties and cardioselectivity of ICI 141, 292 were investigated in healthy male subjects. Seven subjects received in random order oral doses of ICI 141,292 20, 50, 100, 200 and 400 mg, atenolol 50 and 100 mg and placebo. ICI 14 292 had no effect on supine heart rate which was reduced by atenolol 100 mg. ICI 141,292 50, 100 and 200 mg had no effect on standing heart rate which was reduced by 400 mg at 2 h. Both doses of atenolol caused greater reductions. The maximum percent reduction of an exercise tachycardia after ICI 141,292 200 mg (23.9 +/- 3.7%) and 400 mg (24.3 +/- 5.2%) were similar to atenolol 50 mg (27.3 +/- 4.7%) but less than atenolol 100 mg (30.8 +/- 2.9%) (P less than 0.02). Six subjects received in random order single oral doses of ICI 141,292 100, 200 and 400 mg, atenolol 50 mg, propranolol 40 mg and placebo. Following each dose each subject received graded infusions of isoprenaline sulphate until heart rate increased by 40 beats min-1. Dose-response curves were constructed for the changes in heart rate, finger tremor, blood pressure and forearm blood flow produced by each infusion. At the 4 micrograms min-1 dose of isoprenaline, ICI 141,292 200 mg caused more attenuation than atenolol 50 mg but less than propranolol 40 mg in the changes of heart rate, diastolic blood pressure and finger tremor (P less than 0.02). ICI 141,292 400 mg caused more attenuation of the changes of all parameters than atenolol 50 mg but less attenuation of the changes in diastolic blood pressure and finger tremor than propranolol 40 mg (P less than 0.02). These results indicate that ICI 141,292 is a cardioselective beta-adrenoceptor antagonist with partial agonist activity.  相似文献   
19.
The incidence of adenocarcinoma and dysplasia in Barrett''s esophagus   总被引:17,自引:0,他引:17  
OBJECTIVE: The reported incidence of adenocarcinoma in Barrett's esophagus is variable. The aim of this study was to determine the incidence of dysplasia and adenocarcinoma in a population of patients with Barrett's esophagus followed prospectively and to compare these findings with other series. METHODS: All patients enrolled in the Cleveland Clinic Foundation's Barrett's esophagus registry from 1979 to 1995 were followed. Barrett's esophagus was defined as intestinal metaplasia anywhere in the tubular esophagus. The incidence of dysplasia and adenocarcinoma in these patients was recorded systematically. RESULTS: A total of 136 patients (91 male, 45 female) were followed in an endoscopic surveillance program for a mean of 4.2 yr and a total of 570 patient-years of follow-up. Thirty patients (22%) had short segment Barrett's esophagus. Two adenocarcinomas developed during follow-up, yielding an incidence of one per 285 patient-years of follow-up. Low grade dysplasia developed in 24 patients, whereas high grade dysplasia developed in four patients. CONCLUSIONS: Our study suggests that the incidence of adenocarcinoma in Barrett's esophagus is lower than initially thought. However, large multicenter studies are required to clarify the epidemiological and clinical factors related to the development of dysplasia and adenocarcinoma in Barrett's esophagus.  相似文献   
20.
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