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   1799727篇
  免费   127506篇
  国内免费   4030篇
耳鼻咽喉   23500篇
儿科学   58699篇
妇产科学   48433篇
基础医学   255203篇
口腔科学   52397篇
临床医学   157743篇
内科学   359253篇
皮肤病学   41936篇
神经病学   139472篇
特种医学   66221篇
外国民族医学   243篇
外科学   269894篇
综合类   39500篇
现状与发展   4篇
一般理论   564篇
预防医学   134507篇
眼科学   42519篇
药学   130671篇
  7篇
中国医学   4955篇
肿瘤学   105542篇
  2021年   14850篇
  2019年   15848篇
  2018年   24006篇
  2017年   17592篇
  2016年   18828篇
  2015年   21419篇
  2014年   28961篇
  2013年   42190篇
  2012年   60320篇
  2011年   63469篇
  2010年   36811篇
  2009年   33509篇
  2008年   57924篇
  2007年   61658篇
  2006年   61634篇
  2005年   58905篇
  2004年   56302篇
  2003年   53391篇
  2002年   51301篇
  2001年   94616篇
  2000年   96937篇
  1999年   79429篇
  1998年   20101篇
  1997年   17517篇
  1996年   17643篇
  1995年   16933篇
  1994年   15444篇
  1993年   14220篇
  1992年   58352篇
  1991年   56126篇
  1990年   53704篇
  1989年   51362篇
  1988年   46650篇
  1987年   45448篇
  1986年   42738篇
  1985年   40419篇
  1984年   29678篇
  1983年   25157篇
  1982年   14017篇
  1979年   25815篇
  1978年   17753篇
  1977年   15075篇
  1976年   14053篇
  1975年   14805篇
  1974年   17917篇
  1973年   17254篇
  1972年   15921篇
  1971年   14733篇
  1970年   13683篇
  1969年   12767篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
AIM: The present meta-analysis aims to compare short-term and long-term outcomes in patients undergoing laparoscopic or open subtotal colectomy for benign and malignant disease. METHODS: A literature search of Medline, Ovid, Embase and Cochrane databases was performed to identify studies published between 1992 and 2005, comparing laparoscopic (LSC) and open (OSC) subtotal colectomy. A random effect meta-analytical technique was used and sensitivity analysis performed on studies published since the beginning of 2000, higher quality papers, those reporting on more than 40 patients, and those studies reporting on adult cases or acute colitis. RESULTS: A total of eight studies satisfied the criteria for inclusion. These included outcomes on 336 patients, 143 (42.6%) of whom had undergone laparoscopic resection, with an overall conversion rate to open surgery of 5% (range 0-11.8%). Operative time was significantly longer in the laparoscopic group by 86.2 min (P < 0.001) and throughout subgroup analysis, although it was only in patients with acute colitis that this finding was without significant heterogeneity. Operative blood loss was less in the laparoscopic group by 57.5 millilitres in high quality and studies published since 2000, and 65.3 millilitres in those reporting on more than 40 patients. There was no significant difference in early or long-term complications between the groups. A statistically significant reduction in length of postoperative stay was observed in the laparoscopic groups by 2.9 days (P < 0.001). CONCLUSION: Laparoscopic subtotal colectomy was associated with longer operating times but a reduced length of stay compared to open surgery. Although short-term outcomes were equivalent in both groups, the suggested benefits in terms of reduced long-term obstructive complications were not supported by this meta-analysis.  相似文献   
993.
BACKGROUND: Stress can aggravate the allergic inflammation, but determinants of disturbed immune regulation are largely unknown. OBJECTIVE: To determine systemic immunological, local inflammatory and functional airway responses to stress in healthy and atopic individuals. METHODS: Forty-one undergraduate students, 22 with allergy of whom 16 had asthma, and 19 healthy controls, were studied in a low-stress period and in association with a large exam. Subjects completed questionnaires on stress and health behaviours, underwent lung function tests, bronchial methacholine challenge, measurements of exhaled nitric oxide and urine cortisol. Blood cells were phenotyped, and cytokines from mononuclear blood cells were analysed. RESULTS: Perceived stress and anxiety increased in both groups during the exam period while cortisol increased only in the atopy group. Cytokine production decreased broadly in response to stress in both groups, which was paralleled by an increase in the proportion of regulatory T cells (CD4(+)CD45RO(+)CD25(bright)). Interestingly, atopic individuals, but not controls, reacted with a decreased T-helper type 1/T-helper type 2 (Th1/Th2) ratio and a decrease in natural killer (NK) cell numbers in response to stress. In control subjects only, exhaled nitric oxide decreased and forced expiratory volume in one second increased during stress. CONCLUSION: Atopic and non-atopic subjects shared some immune changes in response to stress, such as a dramatic decline in cytokines and an increase in the number of regulatory T cells in peripheral blood. However, other stress-induced immune changes were unique to atopic individuals, such as a skewed Th1/Th2 ratio and reduced NK cell numbers, indicating that some pathogenic mechanisms in atopics may be more strongly affected by stress than others.  相似文献   
994.
995.
996.
997.
998.
999.
1000.
The inhibitory effect of polysaccharide on mumps virus multiplication   总被引:12,自引:12,他引:0  
Polysaccharides derived from type-specific Friedl?nder bacilli cause inhibition of the multiplication of mumps virus in the allantoic sac of the chick embryo. As little as 5 microg. of polysaccharide is effective as an inhibitor. Inhibition of multiplication is obtained when polysaccharide is injected as long as 4 days after inoculation of virus. Chemical studies have shown that the structural configurations of the polysaccharide responsible for specific serological activity are not identical with those which determine the inhibitory effect relative to mumps virus. The possible mechanisms of the inhibition of viral multiplication by means of polysaccharides are discussed.  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