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   2689033篇
  免费   194755篇
  国内免费   7877篇
耳鼻咽喉   35863篇
儿科学   88365篇
妇产科学   73865篇
基础医学   377108篇
口腔科学   75387篇
临床医学   242554篇
内科学   538108篇
皮肤病学   64936篇
神经病学   222179篇
特种医学   103087篇
外国民族医学   752篇
外科学   399450篇
综合类   51373篇
现状与发展   6篇
一般理论   1006篇
预防医学   207959篇
眼科学   58791篇
药学   194362篇
  8篇
中国医学   5825篇
肿瘤学   150681篇
  2021年   22635篇
  2019年   23010篇
  2018年   32585篇
  2017年   24957篇
  2016年   28441篇
  2015年   32139篇
  2014年   44126篇
  2013年   64972篇
  2012年   87316篇
  2011年   92113篇
  2010年   54861篇
  2009年   52435篇
  2008年   84661篇
  2007年   89838篇
  2006年   91054篇
  2005年   87372篇
  2004年   84153篇
  2003年   80851篇
  2002年   76722篇
  2001年   130466篇
  2000年   133325篇
  1999年   112279篇
  1998年   32057篇
  1997年   28584篇
  1996年   28875篇
  1995年   27908篇
  1994年   25597篇
  1993年   23949篇
  1992年   86434篇
  1991年   82755篇
  1990年   79884篇
  1989年   77164篇
  1988年   70510篇
  1987年   68994篇
  1986年   64468篇
  1985年   61381篇
  1984年   45621篇
  1983年   38500篇
  1982年   22762篇
  1981年   20282篇
  1979年   39531篇
  1978年   27770篇
  1977年   23551篇
  1976年   21730篇
  1975年   23145篇
  1974年   27125篇
  1973年   25719篇
  1972年   24035篇
  1971年   22219篇
  1970年   20481篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Cytokines play a part in the control of cellular growth, differentiation and development. Given such pleiotropic activities, it is not unexpected that the expression of the cytokines is tightly regulated. When cytokine-mediated processes are altered by mutation and/or overexpression of some cytokine or cytokine receptor genes, oncogenic transformation can occur. Oncogenes which derive their transforming potential through this mechanism include sis, which represents the activated form of the platelet-derived growth factor B chain, hst1/K-fgflint-2, which share appreciable homology with the gene family of fibroblast growth factors, fms, which is related to the cell surface receptor for macrophage-colony stimulating factor, and erbB-1, which encodes a truncated form of the epidermal growth factor receptor. Cytokine treatment has resulted in modulation of aberrant oncogene activity in some model systems.  相似文献   
993.
It has long been noted that tetanus is rare in leprosy patients. Five cases of tetanus are reported in leprosy patients in Addis Ababa, Ethiopia. Although natural immunity to tetanus occurs and this appears to be higher in leprosy patients than in the general population, it is not completely protective. Further research on the relationship between tetanus and leprosy is indicated. Although firm epidemiologic data are lacking, it is prudent to give leprosy patients at least one dose of tetanus toxoid.  相似文献   
994.
Using indirect immunohistochemistry and an antiserum raised against rat corticotrophin-releasing factor (CRF) we have outlined an asymmetric network of cells and varicose fibers in sheep adrenal cortex. This network was not associated with the larger splanchnic nerves, but was occasionally found in small bundles or with blood vessels; in most instances fibers were found weaving independently through cortical parenchyma. A plexus of fibers was found in the zona reticularis, with a few fibers ramifying into adjacent medulla. Uni or bipolar cells were found throughout the cortex, with the greatest frequency at the corticomedullary junction; a multipolar-type cell was also found in this area. Staining of varicose structures and most cells was abolished by incubation with excess rat CRF 1-41, but not by ovine CRF or a range of other peptides. Though the immunoreactive species has not as yet been identified, it may thus share homology with sequences present in rat but not ovine CRF.  相似文献   
995.
996.
In an attempt to identify a cause for the alteration in breathing pattern seen when conventional respiratory apparatus is applied to the face, we have studied the effects of causing the subject to focus attention on breathing by counting breaths in threes for 5 min. We used the respiratory inductance plethysmograph in 18 naive subjects who were unaware that their breathing was being measured. In the control periods, distraction was provided by a recorded story played through head-phones. The experiment was repeated with the rim of a facemask applied to the face. Focusing attention on breathing caused a prolongation of inspiration at a constant mean inspiratory flow, and lengthening of expiration. Tidal volume but not ventilation was increased. The facemask rim caused no significant change. It is concluded that conscious awareness of breathing could account for a major part of the effect of conventional respiratory apparatus.  相似文献   
997.
998.
The aim of the study was to evaluate the importance of atrial synchronism for pacing therapy of patients with mixed carotid sinus syndrome. On 23 patients (21 m, 2 f; mean age 69 +/- 8 years) affected by symptomatic mixed carotid sinus syndrome we performed: 1) the study of ventriculo-atrial conduction, 2) the evaluation of pacemaker effect and 3) the carotid sinus massage in standing position during VVI and DVI temporary pacing. All patients received a permanent DVI pacemaker and then underwent a two-month period single-blind, randomized, cross-over study on DVI vs VVI mode. During DVI period, no syncope occurred in any patients, minor symptoms persisted in 11 (48%) of them; during VVI period syncopes recurred in 3 patients, symptoms requiring the withdrawal of VVI pacing and premature DVI reprogramming in 8, minor symptoms were observed in 17 (74%). A comparison between 14 patients who preferred DVI period (Group A) and the remaining 9 patients who had no preference for DVI and VVI period (Group B) revealed that Group A patients had a greater pacemaker effect (-34 +/- 16 mmHg vs -16 +/- 14 mmHg; p less than 0.02) and a higher prevalence of ventriculo-atrial conduction (78% vs 44%; p = 0.1), while the entity of the systolic pressure fall caused by carotid sinus massage was similar in the two groups both during VVI mode (Group A -51 +/- 16 mmHg vs Group B -56 +/- 27 mmHg) and DVI mode (Group A -38 +/- 17 mmHg vs Group B -45 +/- 17 mmHg).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
999.
1000.
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