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   461篇
  免费   23篇
  国内免费   18篇
耳鼻咽喉   1篇
儿科学   23篇
妇产科学   6篇
基础医学   41篇
口腔科学   10篇
临床医学   54篇
内科学   121篇
皮肤病学   3篇
神经病学   10篇
特种医学   132篇
外科学   16篇
综合类   13篇
预防医学   20篇
眼科学   3篇
药学   29篇
肿瘤学   20篇
  2021年   4篇
  2019年   1篇
  2018年   4篇
  2017年   7篇
  2016年   6篇
  2015年   3篇
  2014年   8篇
  2013年   13篇
  2012年   11篇
  2011年   13篇
  2010年   11篇
  2009年   14篇
  2008年   6篇
  2007年   16篇
  2006年   7篇
  2005年   11篇
  2004年   8篇
  2003年   3篇
  2002年   6篇
  2001年   5篇
  2000年   9篇
  1999年   9篇
  1998年   35篇
  1997年   18篇
  1996年   24篇
  1995年   18篇
  1994年   21篇
  1993年   13篇
  1992年   5篇
  1991年   7篇
  1990年   12篇
  1989年   21篇
  1988年   29篇
  1987年   13篇
  1986年   16篇
  1985年   14篇
  1984年   12篇
  1983年   8篇
  1982年   9篇
  1981年   5篇
  1980年   12篇
  1979年   3篇
  1978年   5篇
  1977年   11篇
  1976年   7篇
  1973年   1篇
  1972年   1篇
  1970年   3篇
  1969年   1篇
  1947年   1篇
排序方式: 共有502条查询结果,搜索用时 0 毫秒
71.
A factor that augmented the phagocytosis of IgG-coated ox red blood cells by the human monocyte/macrophage line U937 was identified in cell culture supernatants from two of two patients with angiocentric peripheral T cell lymphomas, three of three patients with angiocentric immunoproliferative lesions that were not frankly malignant, and one of two patients with T lymphoblastic malignancies. The factor was not present in supernatants derived from 14 nonangiocentric peripheral T cell lymphomas of other histologic types nor in ten cases of B cell lymphoma and two cases of Hodgkin's disease. A similar factor was present in the supernatants of concanavalin A (Con A)-stimulated normal peripheral blood mononuclear cells and in the supernatants of IL-2- dependent T cell lines derived from normal peripheral blood. The factor had an apparent mol wt of greater than 50,000 daltons, was heat labile (100 degrees C for two minutes), and stable at pH 2.0. Its stimulation of phagocytosis was independent of any increase in number of Fc receptors. Thus, this factor is probably not gamma-interferon. This factor may play a pathogenetic role in the hemophagocytic syndromes associated with certain T cell malignancies and immunodeficient states.  相似文献   
72.
Prior studies have shown that pneumothorax is one of the more difficult entities to diagnose with digitized radiography. This study was designed to test whether increasing resolution from 1.25 to 2.5 line pairs per millimeter (lp/mm) and image processing (edge enhancement from unsharp masking) would increase accuracy and confidence in the diagnosis of pneumothorax, as well as normal cases and other forms of lung disease. Conventional radiographs were digitized with use of a laser reader and then reformatted as film hard copy. Eleven observers read 35 cases reformatted in three different ways (1.25 lp/mm, 2.5 lp/mm, 1.25 lp/mm unsharp mask). The images with finer resolution (2.5 lp/mm) and unsharp mask images were superior to those with coarser resolution (1.25 lp/mm) for the diagnosis of pneumothorax. There was no difference in diagnostic accuracy for normal patients. For abnormalities other than pneumothorax, the unsharp mask images were significantly worse. Confidence in the diagnosis of pneumothorax and other abnormalities was highest with the finest resolution (2.5 lp/mm).  相似文献   
73.
Human red cells (RBCs) were collected in CPDA-1 and then freeze-dried in lyoprotective solution. The lyophilized RBCs were then stored at -20 degrees C for 7 days. At the end of the storage period, the lyophilized RBCs were rehydrated and washed in dextrose saline. The washed, reconstituted, lyophilized RBCs were resuspended in final wash solutions of ADSOL, CPDA-1, or a special additive solution containing glucose, citrate, phosphate, adenine, and mannitol, and then they were stored at 4 degrees C for an additional 7 days. The main purpose of this study was to determine whether human RBCs can be lyophilized in such a manner that normal metabolic, rheologic, and cellular properties are maintained during rehydration and subsequent storage in standard blood bank preservative solutions. Our results show that reconstituted, lyophilized RBCs maintained levels of ATP, 2,3 DPG, lactate, and cellular properties that are equal to or better than those in control nonlyophilized RBCs stored for a comparable period in CPDA-1. Reconstituted, lyophilized RBCs stored at 4 degrees C after rehydration also show better maintenance of ATP, 2,3 DPG, and lactate than do control RBCs stored in the same preservative solutions for comparable periods.  相似文献   
74.
The Film Digital Radiography System (FilmDRS) is a device with a laser optical film digitizer, 2,000 X 2,000 X 12-bit memory, and a 1,000-line video display. To evaluate the adequacy of this device for general radiography of the chest, four readers independently analyzed both radiographs and the corresponding video display of the digitized chest images of 150 patients, consisting of 100 images of abnormalities and 50 normal images. The overall results indicate equal sensitivity for the two systems. The FilmDRS, with interactive windowing, proved superior in the detection of hilar and mediastinal disease. X-ray film was superior in allowing detection of hyperlucent states. There was equivalent sensitivity for other disease categories. Superior specificity was achieved with conventional radiographs.  相似文献   
75.
76.
Focal liver masses: differential diagnosis with pulsed Doppler US   总被引:8,自引:0,他引:8  
Duplex Doppler ultrasound (US) was used in 68 consecutive patients with focal liver lesions, including 12 hepatocellular carcinomas, one cholangiocarcinoma, 37 metastases, 15 hemangiomas, one hemangioendothelioma, and two focal nodular hyperplasias. Of the hepatocellular carcinomas, six were diffusely hyperechoic, two were hypoechoic, two were single hyperechoic lesions, and two were multifocal and hyperechoic. All ten tumors with Doppler shifts of 5 kHz or above proved to be hepatocellular carcinomas. The other two hepatocellular carcinomas showed Doppler shifts of 3 kHz. In contrast, no hemangioma showed shifts above 0.7 kHz, and ten of the 15 gave no detectable signal. Of the metastases, 20 gave no signal and 17 had signals of up to 4 kHz. Three-kilohertz signals were also obtained from a cholangiocarcinoma, a hemangioendothelioma, and focal nodular hyperplasia. Correlation with angiographic findings suggested that the high-velocity Doppler signals were associated with large pressure gradients due to arteriovenous shunting. Duplex Doppler US can therefore aid in the differential diagnosis of diffuse and focal liver lesions.  相似文献   
77.
Studies of women undergoing termination of a pregnancy are often used to make recommendations about family planning and health education policy. However, it is not clear how similar the women in these studies are to the general population of women of childbearing age. Our secondary analysis of the National Sexual Attitudes and Lifestyles Survey allowed us to test the hypothesis that women who have undergone an abortion are the same as those who have not (in terms of socio-demographic characteristics, lifestyles, and attitudes). Our findings show significant differences between these two groups of women, particularly regarding ethnicity, marital status, number of natural children, lifetime number of sexual partners, and attitudes to abortion. We conclude that family planning/reproductive health services and health education policies need to take these differences into account and that further research is required to explain why these differences arise.  相似文献   
78.
79.
80.
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