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   266764篇
  免费   22704篇
  国内免费   16141篇
耳鼻咽喉   2354篇
儿科学   3368篇
妇产科学   5159篇
基础医学   31148篇
口腔科学   4637篇
临床医学   34164篇
内科学   43406篇
皮肤病学   3036篇
神经病学   14743篇
特种医学   9601篇
外国民族医学   106篇
外科学   29410篇
综合类   38280篇
现状与发展   52篇
一般理论   47篇
预防医学   16729篇
眼科学   7266篇
药学   26861篇
  189篇
中国医学   12336篇
肿瘤学   22717篇
  2024年   782篇
  2023年   3810篇
  2022年   9523篇
  2021年   12487篇
  2020年   9158篇
  2019年   8325篇
  2018年   8766篇
  2017年   7704篇
  2016年   7383篇
  2015年   11137篇
  2014年   13990篇
  2013年   13044篇
  2012年   19097篇
  2011年   21127篇
  2010年   12949篇
  2009年   10355篇
  2008年   14030篇
  2007年   14138篇
  2006年   13667篇
  2005年   13697篇
  2004年   9563篇
  2003年   8656篇
  2002年   7532篇
  2001年   6778篇
  2000年   6813篇
  1999年   7081篇
  1998年   4028篇
  1997年   4131篇
  1996年   3089篇
  1995年   2855篇
  1994年   2436篇
  1993年   1660篇
  1992年   2505篇
  1991年   2188篇
  1990年   1829篇
  1989年   1602篇
  1988年   1387篇
  1987年   1303篇
  1986年   1051篇
  1985年   819篇
  1984年   538篇
  1983年   407篇
  1982年   241篇
  1981年   218篇
  1980年   216篇
  1979年   288篇
  1978年   163篇
  1977年   119篇
  1976年   109篇
  1974年   135篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
Endothelial cell antigens recognized by xenoreactive human natural antibodies.   总被引:10,自引:0,他引:10  
Hyperacute rejection of vascularized, discordant xenografts is generally though to be initiated when natural antibodies of the recipient bind to endothelial cells of the donor organ. While rejection of such xenografts always occurs, the molecular targets of natural antibodies have not been elucidated. The aim of the experiments reported herein was to identify the molecules on porcine endothelial cells that would be recognized by human natural antibodies if a porcine organ were to be transplanted into a human (or rhesus). Toward the end, it was shown that the major components recognized by human serum on porcine endothelial cells are glycoproteins of 115kDa, 125kDa, and 135kDa (gp115/135). Reactivity with these glycoproteins was abrogated by enzymatic cleavage of N-linked oligosaccharides or of subterminal beta-D-gal residues suggesting that the determinants are located on oligosaccharides rather than on the polypeptide cores. The biological relevance of gp115/135 was suggested by experiments in which a similar series of components was shown to be recognized by rhesus natural antibodies and by the absorption of such antibodies by perfusion of porcine kidneys. The gp115/135 antigens were present on porcine platelets but not porcine RBC or lymphocytes. Nevertheless, purified RBC and lymphocytes absorbed human anti-gp115/135, suggesting that human natural antibodies recognize the same or crossreactive carbohydrate determinants expressed on the surface of a variety of cells.  相似文献   
64.
Monoamine oxidase (MAO) A and B play an important role in regulating levels of biogenic amines. MAO A and B cDNAs have been cloned and the deduced amino acids share 73% sequence identity. The genes for MAOA and B are comprised of 15 exons interspersed by 14 introns, span at least 60 kb and exhibit identical exon-intron organization. These findings suggest that the MAOA and MAOB genes are derived from the duplication of a common ancestral gene. The core promoter region of MAOA is comprised of two 90 bp repeats, each of which contains two Spl elements and lacks a TATA box. The MAOB core promoter region contains two sets of overlapping Spl sites which flank a CACCC element all upstream of a TATA box. The different organization of the MAOA and MAOB promoters may underlie their different cell and tissue specific expression.  相似文献   
65.
不同术后镇痛模式对红细胞免疫功能的影响   总被引:4,自引:1,他引:3  
目的探讨不同术后镇痛模式对红细胞免疫功能的影响。方法50例妇科手术患者,按术后不同镇痛模式分为硬膜外自控镇痛(PCEA)组和静脉自控镇痛(PCIA)组。并分别于术前、术后1、3、7 d采静脉血样检测红细胞C3b受体花环率(RCR)、红细胞免疫复合物花环率(RICR)、红细胞免疫粘附促进因子(RFER)和红细胞免疫粘附抑制因子(RFIR)。结果与术前比,PCEA组术后1 d RCR、RFER显著上升(P<0.05),RFIR显著下降(P<0.05),术后3 d RCR、RFER仍显著上升(P<0.05),而RICR显著下降(P<0.05);PCIA组术后1 d RCR、RFER显著下降(P<0.05),RFIR、RICR显著上升(P<0.05);PCIA组术后1、3 d RCR、RFER比PCEA组显著降低(P<0.05),而RICR显著上升(P<0.05);两组各参数在术后7 d基本恢复至术前水平。结论PCEA对红细胞免疫功能的稳定和恢复作用明显强于PCIA。  相似文献   
66.
67.
合同制护士存在的问题分析与对策   总被引:1,自引:1,他引:0  
陈维荣 《护理研究》2007,21(33):3079-3080
科学技术飞速发展的今天,在知识经济市场与服务竞争的大潮中,每个行业都在寻求新的机遇,面对新的挑战,存在新的危机,合同制护士表现尤为突出,存在着工资收入低、工作压力大、工作稳定性差等问题。现就其现状作一分析,提出相应对策。1合同制护士的现状分析近年来,合同制一词在人们生活中已不再陌生,并逐渐被人们接受。合同制护士在医院的护理队伍中工资收入、职称晋升、医疗保险、福利待遇等方面均与正式在编护士有着很大的差异。由于近年来护理专业毕业生急剧增长,面对当前就业难的压力和激烈的竞争环境,她们相继到各大医院竞聘,而医院招工…  相似文献   
68.
We report a case of calcified chronic encapsulated intracerebral haematoma (ICH) in a 29-year-old female who presented with progressive left sided weakness and intermittent seizures since childhood. The preoperative magnetic resonance (MR) imaging of the head initially suggested that a partially thrombosed aneurysm or vascular malformation was present. However, no vascular stain was found on the digital subtraction angiography (DSA) of both the carotid and vertebral arteries. The excised mass was histologically diagnosed as a chronic ICH. We traced the patient's medical history and found that at the age of one she sustained a head injury after a fall. So far, to our knowledge, no case of epilepsy secondary to a calcified chronic encapsulated ICH occurring 28 years after head injury has been reported. Calcified chronic encapsulated ICH concomitant with new bone formation within is even rarer. The possible pathogenesis of this case is discussed.  相似文献   
69.
谈耳鼻喉科教学中多媒体技术的应用   总被引:3,自引:0,他引:3  
多媒体教学技术应用于耳鼻喉科教学,具有直观性好、动态感强、信息量大等优点,能使教学信息直接、形象、具体、生动地展现给学生,让学生体会到学习的乐趣,是耳鼻喉科现代化教学的理想模式.  相似文献   
70.
In 1998, an epithermal neutron test beam was designed and constructed at the Tsing Hua Open-Pool Reactor (THOR) for the purpose of preliminary dosimetric experiments in boron neutron capture therapy (BNCT). A new epithermal neutron beam was designed at this facility, and is currently under construction, with clinical trials targeted in late 2004. Depth dose-rate distributions for the THOR BNCT test beam have been measured by means of activation foil and dual ion chamber techniques. Neutron and structure-induced gamma spectra measured at the test beam exit were configured into a source function for the Monte Carlo-based treatment planning code NCTPlan. Dose-rate scaling factors (DRSFs) were determined to normalize computationally derived dose-rate distributions with experimental measurements in corresponding mathematical and physical phantoms, and to thus enable accurate treatment planning using the NCTPlan code. A similar approach will be implemented in characterizing the new THOR epithermal beam in preparation for clinical studies. This paper reports the in-phantom calculated and experimental dosimetry comparisons and derived DRSFs obtained with the THOR test beam.  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