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   358570篇
  免费   27035篇
  国内免费   15654篇
耳鼻咽喉   3753篇
儿科学   6064篇
妇产科学   8991篇
基础医学   46258篇
口腔科学   7695篇
临床医学   40045篇
内科学   60946篇
皮肤病学   5245篇
神经病学   21508篇
特种医学   12558篇
外国民族医学   99篇
外科学   43151篇
综合类   38604篇
现状与发展   48篇
一般理论   78篇
预防医学   23680篇
眼科学   9440篇
药学   34019篇
  164篇
中国医学   11594篇
肿瘤学   27319篇
  2023年   3776篇
  2022年   9147篇
  2021年   12386篇
  2020年   8912篇
  2019年   8576篇
  2018年   9563篇
  2017年   8098篇
  2016年   7811篇
  2015年   11448篇
  2014年   14549篇
  2013年   14380篇
  2012年   21015篇
  2011年   22900篇
  2010年   14067篇
  2009年   11506篇
  2008年   16039篇
  2007年   16333篇
  2006年   15871篇
  2005年   15574篇
  2004年   11539篇
  2003年   10367篇
  2002年   9192篇
  2001年   12340篇
  2000年   12680篇
  1999年   11850篇
  1998年   5382篇
  1997年   4995篇
  1996年   3749篇
  1995年   3463篇
  1994年   3032篇
  1993年   2278篇
  1992年   5865篇
  1991年   5672篇
  1990年   5120篇
  1989年   4859篇
  1988年   4550篇
  1987年   4303篇
  1986年   3910篇
  1985年   3600篇
  1984年   2471篇
  1983年   2124篇
  1982年   1197篇
  1979年   2141篇
  1978年   1337篇
  1975年   1281篇
  1974年   1481篇
  1973年   1513篇
  1972年   1439篇
  1971年   1328篇
  1970年   1212篇
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
41.
A patient with Graves' disease had a symptomatic thrombocytopathy during periods of remission. When euthyroid, she noticed bruising, petechiae, and epistaxis. Hemostatic abnormalities included prolongation of the bleeding time by aspirin, reduced platelet retention (a second-phase defect), and abnormal thrombin-induced aggregation and serotonin release. When hyperthyroid, bleeding symptoms resolved, and platelet function returned to normal. These observations suggest that mild bleeding disorders may be influenced either directly or indirectly by thyroid hormone levels.  相似文献   
42.
Measurements of the fetal eyeball and its pattern of growth   总被引:1,自引:0,他引:1  
  相似文献   
43.
44.
45.
Computed tomography of the brain in the Smith-Lemli-Opitz syndrome   总被引:1,自引:0,他引:1  
Computed tomographic (CT) scans of the brain in a child with Smith-Lemli-Opitz syndrome revealed enlargement of the ventricular system, hypoplasia of the cerebellum, and abnormal thickening of the gray matter, consistent with pachygyria. These findings have been previously noted in autopsies performed on patients with this disorder. We conclude that CT scanning is a valuable tool in the evaluation of children suspected of having the Smith-Lemli-Opitz syndrome.  相似文献   
46.
Normal seminal vesicles were studied histologically in 80, and by Feulgen’s cytophotometric method in 10 autopsied cases (males, 44–82 years of age). In every case large, hyperchromatic nuclei were found. By cytophotometry euploid polyploid atypia was also shown in every case, which is characteristic of benign hormonal dysplasia.  相似文献   
47.
Seventy seven antral biopsies were collected from patients attending endoscopy clinic at King Khalid University Hospital, Riyadh, Saudi Arabia during a period of six months between December 1988 to May 1989. Of these 69 (89.6%) showed chronic gastritis as well as Helicobacter-like organisms (HLOs) in the biopsy specimens while 63 (81.8%) of biopsies grew Helicobacter pylori on culture. These findings indicate a good correlation between the histological diagnosis of chronic gastritis and isolation of H. pylori on culture.  相似文献   
48.
Rats exposed on their first postnatal day to 100% nitrogen for 25 min developed hyperactivity and lower performance in passive avoidance task during development. Administration of MK-801 (0.5 mg/kg i.p.) 1 h before anoxia or (0.25 and 0.5 mg/kg) 1 h after completely reversed this behavioral impairment. Senescent rats (24-26 months) exposed to hypoxia (92% N2 + 8% O2) for 5 h failed in their performance in C.A.R., 30 days later. Pretreatment with MK-801 (1 mg/kg i.p.) completely reversed this impairment. These data suggest that activation of endogenous NMDA receptors produces different behavioral consequences in neonatal and senescent rats and that MK-801 administration close to exposure of animals to anoxia or hypoxia can prevent such damage, thus preventing behavioral impairments in postnatal as well as in senescent rats.  相似文献   
49.
Transient transfection of pLB2CAT constructs bearing short synthetic oligonucleotides derived either from the tyrosine hydroxylase (TH) promoter or other sources was used to examine functional cAMP regulatory element (CRE) activity in a variety of cell lines. The region containing only the putative TH CRE was found to be as or more effective in conferring cAMP responsiveness onto pLB2CAT (which employs the TK promoter) than the immediate 272 bp region of the TH promoter. Increases in CAT activity of 10- to 20-fold were observed in JEG-3 cells with a single insert of the TH CRE region (-31 to -54) in pLB2CAT, and the presence of a second insert generated only a modest further increase. This construct also responded to cAMP in 4 other cell lines tested but the degree of increase was less dramatic. Inserts containing the consensus 8 bp CRE motif embedded in other natural or artificial contexts served generally as weak functional CREs in all cell lines tested. In vitro analysis revealed that a specific protein-DNA complex apparently containing a single protein with a MW of 45-50 kDa was formed equally well with JEG-3 cell nuclear extract and CRE-bearing-TH and other fragments which produced dramatically different cAMP effects in vivo. These results suggest specificity in the effects of cAMP on different CREs which are dictated by contextual differences.  相似文献   
50.
Oncologic screenings of the populations in the areas with increased incidence of esophageal cancer have revealed Barrett's ulcer in 1 percent of the examinees. Endoscopic and cytologic characteristics of this condition are presented. Precancer changes--severe dysplasia--are most frequent in male Kazakhs (14.1 percent) aged 50 to 59 (14.7 percent). Subjects with Barrett's ulcer developing severe dysplasia, as evidenced by cytograms, should be included in the group of subjects at risk for carcinoma of the lower third of the esophagus and cardia.  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