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   48328篇
  免费   4372篇
  国内免费   1795篇
耳鼻咽喉   311篇
儿科学   871篇
妇产科学   1362篇
基础医学   10150篇
口腔科学   1693篇
临床医学   3910篇
内科学   5220篇
皮肤病学   1268篇
神经病学   2934篇
特种医学   1077篇
外国民族医学   20篇
外科学   3312篇
综合类   7340篇
现状与发展   12篇
一般理论   12篇
预防医学   3822篇
眼科学   955篇
药学   5683篇
  20篇
中国医学   1088篇
肿瘤学   3435篇
  2024年   45篇
  2023年   484篇
  2022年   804篇
  2021年   1489篇
  2020年   1326篇
  2019年   1350篇
  2018年   1352篇
  2017年   1475篇
  2016年   1572篇
  2015年   1606篇
  2014年   2543篇
  2013年   3485篇
  2012年   2560篇
  2011年   2840篇
  2010年   2485篇
  2009年   2278篇
  2008年   2231篇
  2007年   2415篇
  2006年   2267篇
  2005年   2057篇
  2004年   1883篇
  2003年   1707篇
  2002年   1460篇
  2001年   1269篇
  2000年   1122篇
  1999年   998篇
  1998年   944篇
  1997年   873篇
  1996年   835篇
  1995年   793篇
  1994年   679篇
  1993年   630篇
  1992年   559篇
  1991年   509篇
  1990年   383篇
  1989年   378篇
  1988年   324篇
  1987年   259篇
  1986年   229篇
  1985年   386篇
  1984年   333篇
  1983年   222篇
  1982年   254篇
  1981年   206篇
  1980年   158篇
  1979年   101篇
  1978年   101篇
  1977年   64篇
  1976年   62篇
  1975年   35篇
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
101.
增溶分光光度法测定人发中铝   总被引:1,自引:0,他引:1  
目的:建立一种测定人发中铝的新方法。方法:以铬天青S-溴化十六烷基三甲铵为表面活性剂增溶分光光度法测定人发中铝。结果:方法检出限为0.006μg/ml,相对标准偏差小于1.3%,加标回收率在91%-104%之间。结论:方法简便,不需要特殊仪器,易于推广使用。  相似文献   
102.
103.
104.
医疗仪器的人因工程学设计   总被引:6,自引:2,他引:4  
人因工程学是一门边缘性应用科学,对医疗仪器的设计有重要的指导作用;本文论述了医疗仪器设计中必须考虑的人因工程学因素,包括人体对作业负荷的耐受性、人体尺度、人体的生物力学特性、人的适宜劳动姿势、人机界面、作业空间、安全性和维修性等。  相似文献   
105.
目的探讨环境致癌物苯并(a)芘代谢物反式二羟环氧苯并芘(BPDE)对人支气管上皮细胞HER2/neu基因表达的影响。方法利用半定量RT-PCR、SYBR GreenI实时定量RT-PCR(QRT-PCR)、Western blot及免疫细胞化学方法分别检测经2.0μmol/L反式BPDE诱发人支气管上皮细胞恶性转化细胞(16HBE-T)与对照DMSO溶剂组未恶性转化细胞(16HBE-N)之间HER2/neu基因mRNA和蛋白表达水平的差异,及两组细胞内HER2/neu蛋白表达定位分析。结果经几种不同方法检测反式BPDE恶性转化人支气管上皮细胞中HER2/neu基因mRNA和蛋白水平都比对照溶剂组细胞(16HBE-N)表达显著升高(P<0.05)。HER2/neu蛋白定位在胞膜。结论反式BPDE诱发人支气管上皮细胞恶性转化存在HER2/neu表达增高,其可能与原癌基因HER2/neu被激活作用有关。  相似文献   
106.
Attempts have been made to culture the mucosa from various parts of the gastrointestinal tract. In this study, using an explant culture method, epithelial cells have been successfully cultured from all major regions of the gastrointestinal tract. The success rate, as judged by outgrowth of epithelial cells for at least 4 weeks, varied with the tissue studied with 19/50 colonic biopsies, 5/11 small intestinal biopsies, 9/12 stomach biopsies and 42/47 gallbladder biopsies yielding outgrowth of epithelial cells. Differentiation of the epithelial cells along the mucus cell pathway could be demonstrated on the monolayer cultures using Periodic acid Schiff or Alcian blue staining. Because the cultures were very heterogeneous and many morphological cell types were present in most cultures, differentiation along the other known differentiation pathways of the gastrointestinal mucosa, such as development of absorptive cells and endocrine cells, could not be excluded.
The problem of bacterial contamination, which has hindered previous studies on tissue from these sites, was overcome by decontaminating the biopsy by soaking in dilute sodium hypochlorite (0.04%).  相似文献   
107.
Objectives. To describe nurse migration patterns in the Philippines and their benefits and costs.
Principal Findings. The Philippines is a job-scarce environment and, even for those with jobs in the health care sector, poor working conditions often motivate nurses to seek employment overseas. The country has also become dependent on labor migration to ease the tight domestic labor market. National opinion has generally focused on the improved quality of life for individual migrants and their families, and on the benefits of remittances to the nation. However, a shortage of highly skilled nurses and the massive retraining of physicians to become nurses elsewhere has created severe problems for the Filipino health system, including the closure of many hospitals. As a result, policy makers are debating the need for new policies to manage migration such that benefits are also returned to the educational institutions and hospitals that are producing the emigrant nurses.
Conclusions and Recommendations. There is new interest in the Philippines in identifying ways to mitigate the costs to the health system of nurse emigration. Many of the policy options being debated involve collaboration with those countries recruiting Filipino nurses. Bilateral agreements are essential for managing migration in such a way that both sending and receiving countries derive benefit from the exchange.  相似文献   
108.
Background Dendritic cells (DC) mediate inflammation in rodent models of allergic airway disease, but the role played by human respiratory‐tract DC (hRTDC) in atopic asthma remains poorly defined. Recent data suggest that CD1 antigen presentation by hRTDC may contribute to asthma pathogenesis. Objective To investigate the influence of hRTDC on the balance between atopy and allergic asthma in human subjects and to determine whether CD1 expression by hRTDC is modulated during asthmatic inflammation. Methods Sputum cells were induced from steroid‐naïve, allergen‐challenged and allergen‐naïve subjects (atopic asthmatics, atopic non‐asthmatics and non‐atopic controls). hRTDC were identified using monoclonal antibody labelling and analysis by flow cytometry. Results hRTDC stained HLA‐DR+ (negative for markers of other cell lineages) were predominantly myeloid and comprised ∼0.5% of viable sputum cells. Sputum cells were potent stimulators of allogeneic CD4+ naïve T cells and enrichment/depletion experiments correlated stimulatory potency with DC numbers. Sputum contained cells that exhibited typical dendritic morphology when analysed by electron microscopy. Myeloid hRTDC were endocytically active, but uptake of FITC‐dextran was enhanced in cells from asthmatics (P<0.001). Despite their increased endocytic capacity, asthmatic myeloid hRTDC appeared mature and expressed increased levels of maturation markers (P<0.05–P<0.001), CD1c, CD1d and langerin (P<0.05). CD1c expression by asthmatic myeloid hRTDC was enhanced upon in vivo allergen challenge (three to ninefold within 24 h; P<0.05). CD11cCD123high hRTDC were only detected in asthmatic sputum and were increased in number following allergen challenge. Conclusion Despite limited cell numbers, it proved possible to analyse human RTDC in induced sputum, providing evidence that increased antigen uptake and enhanced CD1 presentation by activated hRTDC may contribute to allergic airway disease. CD1 presentation by hRTDC in atopic asthma may therefore constitute a novel target for future intervention strategies.  相似文献   
109.
PURPOSE: To provide a primer for novice nurse scientists about the increasingly regulated human research environment. ORGANIZING CONSTRUCTS: Federal regulations and international guidelines about protection of human research participants are discussed, with particular attention to institutional review boards for human research. CONCLUSION: Understanding the processes used by institutional review boards to foster ethical human research promotes collaborative interactions and supports compliant research work.  相似文献   
110.
A novel metalloproteinase, recombinant fibrinogenase IV (rFIV(a)), was expressed and purified from Deinakistrodon acutus venom. It was a single chain protein with an apparent molecular weight 27 kDa and an isoeletric point of pH 7.1. RFIV(a) cleaved preferentially the Aalpha-chain and also cleaved Bbeta, gamma-chains of fibrinogen when the incubation time was prolonged. The proteolytic activity was inhibited by EDTA, l-cysteine, and DTT, indicating rFIV(a) was a metalloproteinase requiring disulfide bonds for its activity. It kept above 85% of the initial activity from pH 4.5-11, showed an equal maximum activity at the temperature range from 30 to 50 degrees C, and was inactivated by Zn2+, Cu2+ and Cd2+. Homology modeling of rFIV(a) showed that two highly conserved disulfide bonds (Cys159-Cys164 and Cys117-Cys197) was maintained from its structure, and it exhibited the characteristic conserved motif H142E143XXH146XXGXXH152, whose three histidine residues were involved in binding of the catalytically essential zinc ion. This work demonstrates the expression, purification and characterization of recombinant fibrinogenase IV, which belongs to class P-I metalloproteinase from D. acutus venom.  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