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   14951篇
  免费   930篇
  国内免费   98篇
耳鼻咽喉   131篇
儿科学   318篇
妇产科学   886篇
基础医学   1901篇
口腔科学   310篇
临床医学   1682篇
内科学   3160篇
皮肤病学   278篇
神经病学   1140篇
特种医学   419篇
外科学   1990篇
综合类   279篇
一般理论   8篇
预防医学   795篇
眼科学   424篇
药学   1068篇
中国医学   126篇
肿瘤学   1064篇
  2023年   67篇
  2022年   198篇
  2021年   358篇
  2020年   156篇
  2019年   310篇
  2018年   415篇
  2017年   253篇
  2016年   280篇
  2015年   443篇
  2014年   535篇
  2013年   752篇
  2012年   1100篇
  2011年   1170篇
  2010年   744篇
  2009年   601篇
  2008年   869篇
  2007年   869篇
  2006年   834篇
  2005年   808篇
  2004年   729篇
  2003年   640篇
  2002年   611篇
  2001年   549篇
  2000年   526篇
  1999年   376篇
  1998年   108篇
  1997年   100篇
  1996年   91篇
  1995年   78篇
  1994年   66篇
  1993年   54篇
  1992年   181篇
  1991年   152篇
  1990年   116篇
  1989年   112篇
  1988年   105篇
  1987年   82篇
  1986年   71篇
  1985年   62篇
  1984年   46篇
  1983年   32篇
  1982年   25篇
  1981年   23篇
  1980年   18篇
  1979年   42篇
  1978年   24篇
  1977年   22篇
  1976年   20篇
  1975年   24篇
  1973年   25篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
13.
Using a prospective hospital-based registry, 146 patients with transient ischaemic attack (TIA) were compared with 376 patients with minor first-ever ischaemic stroke with respect to the 3-month risk of subsequent vascular events, in order to clarify the distinctions between the disease entities. All patients were enrolled within 48 h of onset. The risk factor distribution for the two groups was comparable, except that the TIA patients had more previous TIAs. Large artery atherosclerosis (34%) and small vessel occlusion (32%) were the main aetiologies in the TIA group, whereas small vessel occlusion (49%) was the major cause in the stroke group. The 3-month risk of combined endpoints of stroke, myocardial infarction, and vascular death for TIA patients was higher than that for the minor stroke group (15.1% vs. 3.2%; hazard ratio 4.6, 95% confidence interval 2.3-9.3 in multivariate analysis). Large artery atherosclerosis and male sex were the other significant predictors. TIA may demand more urgent management than minor stroke. The fact that aetiology is a predictor, highlights the need for rapid diagnostic tests to establish pathogenesis.  相似文献   
14.
Extracellular phospholipase A2 (PLA2) is a proinflammatory enzyme found especially in the inflammatory exudate to modulate blood flow to areas of antigen stimulation. In this study we found that PLA2 exerted a biphasic effect on the proliferation of phytohemagglutinin (PHA)-stimulated human mononuclear cells (PHA MNC). At low concentrations range from 0.001 to 1 U/ml, PLA2 enhanced the proliferation of PHA MNC (maximal increase was 37.0 +/- 5.67%). Conversely, at concentrations over 10 U/ml, PLA2 markedly suppressed the PHA-induced MNC proliferation (maximal decrease was 88.86 +/- 2.89%). PLA2 was non-toxic to lymphocytes after three days culture, unless the concentration was higher than 100 U/ml. The membrane polarization of PHA-stimulated lymphocytes was also increased by PLA2 at a low concentration. In addition, PLA2 displayed a similar effect on the proliferation of streptokinase-streptodornase (SK/SD) or allogeneic cell stimulated lymphocytes. The change of lymphocyte proliferation by PLA2, was parallel to the change of percentage of helper T cells. Furthermore--a CD4-rich population was proved more susceptible to PLA2 effect than a CD8-rich population. Para-bromophenacyl bromide (pBPB), an irreversible inhibitor of PLA2, abrogated the biphasic effect of PLA2 on PHA MNC proliferation. These results suggest that PLA2 plays a regulatory role on immune reactions by modulating the percentage of helper T cells.  相似文献   
15.
Using the polymerase chain reaction (PCR)-based single strand conformation polymorphism (SSCP) analysis, we have examined the highly conserved regions of the p53 gene in 58 biopsy samples of head and neck tumors. Mutations were found in 13/58 (23%) tumor specimens, but not in 6 normal tissues. Ten of 13 mutations were due to single base changes and the remaining 3 were 1- or 8-base deletion mutants. These mutations were clustered in exons 5 and 7 and resulted in amino acid changes. Our results seem to indicate that mutations in the p53 gene contribute to a significant number of cases of the head and neck tumors including 20% of nasopharyngeal carcinoma biopsies. The relationship of Epstein-Barr virus or human papillomavirus and p53 gene mutations in this group of cancers was also analyzed and discussed.  相似文献   
16.
17.
18.
19.
PURPOSE: To study the diagnostic ability of scanning laser polarimetry with variable corneal compensation (GDx VCC) for early glaucomatous (EG) eyes and glaucoma-suspect (GS) eyes in a Taiwan Chinese population. METHODS: This prospective cross-sectional study included 82 EG eyes (mean deviation, MD: -3.32 +/- 2.20 dB), 45 GS eyes (MD: -2.43 +/- 2.16 dB), and 62 normal eyes. Retinal nerve fiber layer thickness of each subject was measured using GDx VCC and Humphrey Field Analyzer visual field testing. Measured GDx VCC parameters were compared among groups. The area under the receiver operating characteristic (AROC) curve of each parameter was used to differentiate normal from EG eyes or GS eyes. The correlation between MD and each parameter was also evaluated. RESULTS: For both normal versus EG and normal versus GS, the largest AROC values were for nerve fiber indicator, superior average thickness, and inferior average thickness. There was no significant correlation between MD and GDx-VCC-measured parameters either in EG or GS eyes. CONCLUSIONS: GDx VCC shows only moderate ability to distinguish normal eyes from eyes with early glaucoma. However, its diagnostic role in eyes with suspicious discs and normal visual fields is uncertain at this moment in the Taiwan Chinese population. Further studies are needed to address this issue.  相似文献   
20.
Y H Tsai  M H Chang 《台湾医志》1992,91(3):283-286
Fasting serum gastrin values were measured by radioimmunoassay in 53 children with peptic ulcer disease. The mean fasting serum gastrin levels for children with chronic duodenal ulcer, acute gastric ulcer, acute duodenal ulcer who were younger than two years old and acute duodenal ulcer who were older than two years old were: 46.2 +/- 25.7 pg/mL, 46.9 +/- 43.5 pg/mL, 47.9 +/- 12.0 pg/mL and 37.5 +/- 17.8 pg/mL, respectively. Children with peptic ulcer disease did not have elevated fasting serum gastrin levels when compared with age-matched controls. We conclude that a fasting serum gastrin value cannot be used as a screening test for peptic ulcer disease in children, except for Zollinger-Ellison syndrome.  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