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   18849篇
  免费   1050篇
  国内免费   58篇
耳鼻咽喉   177篇
儿科学   520篇
妇产科学   791篇
基础医学   2470篇
口腔科学   488篇
临床医学   1646篇
内科学   3718篇
皮肤病学   416篇
神经病学   1990篇
特种医学   1076篇
外国民族医学   3篇
外科学   2680篇
综合类   162篇
一般理论   38篇
预防医学   1189篇
眼科学   223篇
药学   1206篇
中国医学   28篇
肿瘤学   1136篇
  2021年   215篇
  2020年   160篇
  2019年   230篇
  2018年   320篇
  2017年   221篇
  2016年   279篇
  2015年   305篇
  2014年   470篇
  2013年   607篇
  2012年   912篇
  2011年   964篇
  2010年   501篇
  2009年   517篇
  2008年   731篇
  2007年   844篇
  2006年   931篇
  2005年   809篇
  2004年   735篇
  2003年   775篇
  2002年   728篇
  2001年   679篇
  2000年   703篇
  1999年   507篇
  1998年   299篇
  1997年   254篇
  1996年   150篇
  1995年   151篇
  1994年   120篇
  1993年   163篇
  1992年   355篇
  1991年   316篇
  1990年   353篇
  1989年   339篇
  1988年   309篇
  1987年   314篇
  1986年   295篇
  1985年   272篇
  1984年   182篇
  1983年   170篇
  1982年   120篇
  1979年   203篇
  1978年   131篇
  1977年   125篇
  1976年   123篇
  1975年   165篇
  1974年   170篇
  1973年   147篇
  1972年   148篇
  1971年   120篇
  1970年   138篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
39 human immunodeficiency-virus-1 (HIV-1)-positive hemophiliacs who had been regularly treated with non-virus-inactivated intermediate-purity factor VIII concentrates were divided into two groups. Group A consisted of 21 patients with a CD4/CD8 cell ratio of less than 1.0 and group B of 18 patients with a CD4/CD8 cell ratio of greater than 1.0. All patients of group A were switched to a high-purity virus-inactivated factor VIII concentrate, whereas patients of group B continued to receive the intermediate-purity concentrate. There was no significant difference in the average decline of CD4 cells between the two groups during the observation period. 9 patients of group A and 4 patients of group B developed AIDS. 5 patients of group A but 11 patients of group B remained clinically asymptomatic. We conclude that the 15-fold increase in purity of the factor VIII concentrate had no apparent beneficial effect on the CD4 cell counts in this patient group.  相似文献   
102.
In 148 patients with impingement lesion type I or type II, we performed an arthroscopic subacromial decompression (ASD). 122 patients ran a follow up one to three years post-operatively. All patients were pre- and postoperatively documented by a 100 point shoulder score. The mean score was 57.9 (+/- 11.5) preoperatively. Postoperatively there was a significant increase to 80.7 (+/- 17.9) (p < 0.05). 15% of the patients with a postoperative score less than 70 points were determined as failures. Patients with a preoperative pain history of more than one year had a significantly worse result (79.1 +/- 8.4) compared to those patients with a preoperative course less than one year (88.8 +/- 11.6) (p < 0.05). Other significant factors were the patient's age, and calcific tendinitis, whereas sex, preoperative range of motion, muscle atrophy, and degeneration of the acromioclavicular joint did not significantly influence the result. Our results after ASD in patients with subacromial pathology without a rupture of the rotator cuff are encouraging. Therefore, ASD seems to be a reasonable alternative to open acromioplasty.  相似文献   
103.
In the first part the statistical methods of meta-analysis are discussed. Meta-analysis is considered as a statistical tool for quantitatively summarizing the results of clinical trials with comparable aims (treatments) and designs. Meta-analysis can be based on the significance probabilities or effect values. The last procedure is preferable as it gives an estimate (and confidence interval) for the global effect of the treatment of interest, if homogeneity of the effects between the trials can be assumed. Such a homogeneity can be often achieved by a suitable standardization of the effect variables within the trials. In the second part the methods of meta-analysis are applied to controlled clinical trials with Ginkgo biloba extract EGb 761 in patients with peripheral arterial disease. Included were 5 placebo-controlled clinical trials with similar design and inclusion criteria. In all studies treatment effect was quantified by the increase of walking distance (measured in standardized treadmill exercise). The effect value of EGb 761 treatment was expressed by the standardized mean difference in walking distance increase between EGb 761 and placebo, standardized by the standard deviation. It could be shown that this effect value is homogeneous in all trials. The global effect size was estimated as 0.75. This means that the mean increase in walking distance achieved by EGb 761 is 0.75 times of the standard deviation higher than that achieved by placebo. This value is highly significant different from zero. So the meta-analysis revealed a highly significant therapeutic effect of EGb 761 for the treatment of peripheral arterial disease.  相似文献   
104.
Erb:YAG and Hol:YAG laser ablation rates of fibrocartilage and nucleus pulposus were measured in vitro simulating clinical conditions. After ablation macroscopic and microscopic appearance of the ablation site was investigated. Hol:YAG and Erb:YAG laser mean ablation rates increased almost linearly with rising energies, showing higher total ablation rates for the Hol:YAG laser due to its higher achievable energy density. At comparable energy densities the Erb:YAG laser appears to be more effective with respect to the corresponding ablation rates. Consequently, the ablational threshold proved to be lower for the Erb:YAG laser. Whereas during Hol:YAG laser ablation, some smoke formation and considerable tissue shrinking occurred, these effects could not be observed during Erb:YAG laser ablation. Consequently macroscopic and microscopic inspection showed some thermal damage after Hol:YAG and only minimal alterations after Erb:YAG laser ablation. Adjacent thermal damage was determined and proved to be lower for the Erb:YAG laser. In our opinion the characteristics of each laser system provide certain advantages for special clinical indications.  相似文献   
105.
Reiman  TH; Heiken  JP; Totty  WG; Lee  JK 《Radiology》1988,169(2):564-566
Limited-field-of-view radio-frequency receiver antennas provide improved near-field sensitivity for magnetic resonance imaging by decreasing the antenna volume. The Helmholtz-type surface coil, consisting of two flat rings, is an organ-encompassing antenna that takes advantage of this principle to yield an improved signal-to-noise ratio (S/N). The coil was tested in a group of 50 patients and 16 healthy volunteers. Images obtained with the Helmholtz coil demonstrated quantitatively superior S/N of 2.2-fold or greater than that of comparison body coil images, as well as qualitatively superior anatomic resolution.  相似文献   
106.
107.
108.
During the seventies and eighties of the 20th century, France reported a considerable decline in the overall rate of preterm deliveries. The figure for all births before 37 weeks gestation dropped from 8.2% in 1972 to 4.9% in 1988, and births before 34 weeks accounted for 2.4% of all births in 1972 and 0.9% in 1988. This development was paralleled by the creation of a national program for the active support of women, children and families. This program was aimed at improving medical care, together with financial and social support, in particular for education and improved working conditions for mothers inside as well as outside of the home. Surprisingly, in the nineties a rise in the rate of preterm deliveries was noticed and in a national survey in France the number for all deliveries before 37 weeks was 6.8% in 1998 and 2.0% for the early preterm deliveries. A similar development was also seen in other countries. This could not be explained by changes in socio-medical support programs. Instead, it was related to a rise in the mean age of pregnant women as well as to the development of assisted reproduction. The example of France demonstrates that a political initiative for the support of women, children and families is not only effective in reducing the number of preterm deliveries but also has a positive effect on the national fertility rate. In Europe, France together with Ireland, with 1.89 children per women, rank at the top of the list of national fertility rates. The mean for Europe is 1.41 and countries like Spain and Italy, with fertility rates of 1.22 and 1.25, are at the end of the list.  相似文献   
109.
A 4-year-old girl with post-surgical complete atrioventricular block received an epicardial dual chamber pacemaker system. During further growth intermittent exit block occurred, first misinterpreted as neurological seizures. The epicardial lead was replaced using a transvenous approach, and a pacemaker with an integrated home monitoring facility was implanted. After her discharge, a rise in the pacing threshold automatically initiated an event message. On the basis of this information, the patient was called in and imminent dislodgement of the ventricular lead was diagnosed by x-ray. The lead was repositioned and was found stable over 1-year follow-up.  相似文献   
110.
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