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   467篇
  免费   21篇
  国内免费   22篇
耳鼻咽喉   1篇
儿科学   42篇
妇产科学   1篇
基础医学   25篇
口腔科学   9篇
临床医学   47篇
内科学   91篇
皮肤病学   8篇
神经病学   12篇
特种医学   120篇
外科学   28篇
综合类   29篇
预防医学   14篇
眼科学   27篇
药学   30篇
肿瘤学   26篇
  2023年   1篇
  2020年   1篇
  2019年   3篇
  2018年   6篇
  2017年   4篇
  2016年   3篇
  2015年   10篇
  2014年   11篇
  2013年   12篇
  2012年   7篇
  2011年   13篇
  2010年   14篇
  2009年   16篇
  2008年   14篇
  2007年   23篇
  2006年   29篇
  2005年   8篇
  2004年   16篇
  2003年   12篇
  2002年   11篇
  2001年   19篇
  2000年   8篇
  1999年   7篇
  1998年   33篇
  1997年   22篇
  1996年   28篇
  1995年   22篇
  1994年   19篇
  1993年   22篇
  1992年   7篇
  1991年   5篇
  1990年   9篇
  1989年   7篇
  1988年   7篇
  1987年   4篇
  1986年   11篇
  1985年   10篇
  1984年   7篇
  1983年   6篇
  1982年   7篇
  1981年   7篇
  1980年   13篇
  1979年   3篇
  1978年   4篇
  1977年   4篇
  1976年   4篇
  1975年   1篇
排序方式: 共有510条查询结果,搜索用时 17 毫秒
1.
Purpose: It was investigated whether alterations in neuronal structure and function occasioned by strabismic amblyopia also may be reflected in alterations in the expression on Y type neurons of a Cat-301 antibody sensitive antigen in the lateral geniculate nucleus (LGN) and cortex of our cat model of strabismic amblyopia. Methods/Results: The percentage of positively labelled cells was reduced in LGN laminae that received input from the deviated eye in strabismic amblyopic cats compared with normal cats. In the strabismic cortex, the density of immunopositive neurons was significantly reduced compared with normal, the effect being most pronounced in layer IV Conclusions: Despite previous physiological recordings indicating a decrease in X-cell associated acuity in strabismic amblyopia, the present findings imply that the changes in the early visual experience occasioned by strabismus also produce specific molecular changes in theY neuronal class.  相似文献   
2.
3.
4.
5.
6.
7.
A comprehensive anatomic and radiographic analysis of the peribursal fat plane in 12 cadavers confirmed that the fat plane seen on radiographs represents extrasynovial fat lining the subacromial bursa and documented the anatomic relations of the bursa. A three-part retrospective clinical evaluation of rotator cuff tears, calcific tendinitis, and rheumatoid arthritis was performed. Two osteoradiologists blindly graded the appearance of the peribursal fat plane with the shoulder in external versus internal rotation in 21 patients with arthrographically intact rotator cuffs and 21 patients with disrupted rotator cuffs. The peribursal fat plane was seen better with disrupted rotator cuffs. The peribursal fat plane was seen better with the shoulder in internal rotation and was seen in 60% of control subjects but only 21% of patients with rotator cuff tears. Partial or complete obliteration of this fat plane is a sensitive (79%) but less specific (60%) indicator of rotator cuff tears. Obliteration of the peribursal fat plane by inflammatory processes in adjacent tissues, including calcific tendinitis and rheumatoid arthritis, occurred with a high frequency.  相似文献   
8.
Safe placement of nasogastric tubes requires reliable positioning of the tip of the tube within the stomach. Radiology and aspiration are currently used to confirm tube position, but suffer from significant problems of cost and efficacy, respectively. We have developed a novel method to locate the position of a catheter tip within the body, using the detection of a low energy electromagnetic field generated in a coil located in the catheter with an external hand-held unit (Cathlocator). In vitro, the unit detected the distance of the coil from the detector with an accuracy of 0.1 cm over a range of 4–12 cm. In vivo studies were performed in 11 healthy volunteers using a purpose-built manometric assembly that incorporated the signal generating coil in its tip. In all subjects the Cathlocator showed the position of the signal generating coil to be cranial to the xiphisternum when manometric and transmucosal potential difference criteria showed it to be located above the lower oesophageal sphincter. When the coil was within the stomach, the Cathlocator identified its position within the epigastric, umbilical and left hypochondrial regions of the abdomen. The distance of the coil from the surface was significantly greater when in the duodenum mean (±s.e.m. 7.6±0.3 cm; P<0.001) and oesophagus (8.6±0.2 cm; P<0.002) than the stomach (5.0±0.4 cm). In one subject studied twice there was a close correlation between the location and depth measured by the device on each occasion. The Cathlocator is a novel non-radiological device that has the potential to be useful in the placement of gastrointestinal catheters.  相似文献   
9.
Tumor vascular signals in renal masses: detection with Doppler US   总被引:3,自引:0,他引:3  
Ramos  IM; Taylor  KJ; Kier  R; Burns  PN; Snower  DP; Carter  D 《Radiology》1988,168(3):633-637
The vascularity of 49 renal masses (26 malignant and 23 benign lesions) was investigated with duplex Doppler ultrasound. Doppler signals obtained at the margins of renal masses were defined as "tumor signals" when the Doppler-shifted frequency of the lesion exceeded the frequency shift in the ipsilateral main renal artery. These exceeded 2.5 kHz with a 3-MHz insonating frequency. Among the 26 renal masses that subsequently proved to be malignant, tumor signals were obtained in 15 of 18 (83%) untreated renal cell carcinomas, in three of four Wilms tumors, and in two patients with metastases to the kidney, but not in the one patient with lymphoma. None of the 23 benign renal masses demonstrated tumor signals. Tumor vascularity in malignant lesions gives rise to abnormal, high-velocity, Doppler-shifted signals that can help in the differential diagnosis of renal masses.  相似文献   
10.
BACKGROUND. In most countries, heparin is used in the initial treatment of patients with deep-vein thrombosis. Well-designed studies establishing the efficacy of heparin therapy are lacking, however. Treatment with acenocoumarol alone, according to the hypothesis that high dosages of oral anticoagulants obviate the need for heparin, is considered an effective alternative in some countries. METHODS. In a randomized, double-blind study we compared the efficacy and safety of continuous intravenous heparin plus acenocoumarol with the efficacy and safety of acenocoumarol alone in the initial treatment of outpatients with proximal-vein thrombosis. The principal study end point was a confirmed symptomatic extension or recurrence of venous thromboembolism during six months of follow-up. In addition, we assessed asymptomatic extension or pulmonary embolism by repeating venography and lung scanning after the first week of treatment. The incidence of major bleeding was determined during three months of follow-up. RESULTS. The study was terminated early by the Data Safety and Monitoring Committee because of an excess of symptomatic events in the group that received acenocoumarol alone (in 12 of 60 patients [20 percent], as compared with 4 of 60 patients [6.7 percent] in the combined-therapy group by intention-to-treat analysis; P = 0.058). Asymptomatic extension of venous thrombosis was observed in 39.6 percent of the patients in the acenocoumarol group and in 8.2 percent of patients treated with heparin plus acenocoumarol (P < 0.001). Major bleeding complications were infrequent and comparable in the two groups. CONCLUSIONS. Patients with proximal-vein thrombosis require initial treatment with full-dose heparin, which can safely be combined with acenocoumarol therapy.  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