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   2644522篇
  免费   192077篇
  国内免费   7840篇
耳鼻咽喉   36040篇
儿科学   87024篇
妇产科学   73665篇
基础医学   371118篇
口腔科学   71620篇
临床医学   238698篇
内科学   529769篇
皮肤病学   64258篇
神经病学   218989篇
特种医学   100955篇
外国民族医学   737篇
外科学   392675篇
综合类   50804篇
现状与发展   5篇
一般理论   987篇
预防医学   202362篇
眼科学   58012篇
药学   193316篇
  8篇
中国医学   5711篇
肿瘤学   147686篇
  2021年   22289篇
  2019年   22687篇
  2018年   31791篇
  2017年   24108篇
  2016年   27700篇
  2015年   30996篇
  2014年   42936篇
  2013年   63827篇
  2012年   84793篇
  2011年   89576篇
  2010年   53852篇
  2009年   51280篇
  2008年   82392篇
  2007年   87621篇
  2006年   89091篇
  2005年   85270篇
  2004年   82048篇
  2003年   79177篇
  2002年   76081篇
  2001年   129225篇
  2000年   132177篇
  1999年   111224篇
  1998年   31583篇
  1997年   28199篇
  1996年   28404篇
  1995年   27562篇
  1994年   25220篇
  1993年   23533篇
  1992年   85396篇
  1991年   81751篇
  1990年   78983篇
  1989年   76217篇
  1988年   69628篇
  1987年   68147篇
  1986年   63679篇
  1985年   60643篇
  1984年   45019篇
  1983年   38039篇
  1982年   22547篇
  1981年   20096篇
  1979年   39064篇
  1978年   27533篇
  1977年   23302篇
  1976年   21552篇
  1975年   22856篇
  1974年   26857篇
  1973年   25422篇
  1972年   23798篇
  1971年   22011篇
  1970年   20220篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Summary To evaluate the potential effect of androgens on the development and growth of human colorectal adenomas, the prevalence and concentration of cytosolic androgen receptors (AR) were analysed in 26 adenomas and 19 samples of normal colonic mucosa by a hybrid ligand receptor-binding assay. AR were detected in 7 of the adenomas (26.9%), and in 6 of the normal mucosa samples (31.6%). In the adenomas, AR levels demonstrated were low, ranging from 6 to 31 fmol/mg cytosol protein, and dissociation constants (Kds) ranged from 0.17–2.7x10-9 M. Of 13 adenomas excised from men, 6 (46%) had positive receptor activity, whereas only 1 of 13 (7.7%) from women was positive (P=0.03, Fisher's exact test). There was no correlation between AR titre and patient age, or between adenoma size and histological type or degree of dysplasia. In normal mucosa, AR levels ranged from 7 to 33 fmol/mg and Kds ranges from 0.24–3.1x10-9 M. There was no significant difference between either AR prevalence or levels in the adenomas and normal mucosa. The sex difference was exclusive to the adenoma. Endogenous androgen may play a role in adenoma development early in the promotional process.  相似文献   
993.
994.
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   
995.
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   
996.
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   
997.
998.
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   
999.
1000.
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   
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