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   498729篇
  免费   49703篇
  国内免费   30918篇
耳鼻咽喉   5014篇
儿科学   7772篇
妇产科学   3354篇
基础医学   32584篇
口腔科学   9366篇
临床医学   60282篇
内科学   44691篇
皮肤病学   5151篇
神经病学   13287篇
特种医学   20068篇
外国民族医学   34篇
外科学   44895篇
综合类   133745篇
现状与发展   120篇
一般理论   1篇
预防医学   55870篇
眼科学   6970篇
药学   59816篇
  781篇
中国医学   50398篇
肿瘤学   25151篇
  2024年   2523篇
  2023年   6647篇
  2022年   16965篇
  2021年   21002篇
  2020年   17787篇
  2019年   10243篇
  2018年   11179篇
  2017年   14255篇
  2016年   11028篇
  2015年   20148篇
  2014年   25404篇
  2013年   30957篇
  2012年   45508篇
  2011年   48085篇
  2010年   42116篇
  2009年   36956篇
  2008年   38789篇
  2007年   38071篇
  2006年   33471篇
  2005年   26953篇
  2004年   18665篇
  2003年   15691篇
  2002年   12246篇
  2001年   10879篇
  2000年   8687篇
  1999年   4049篇
  1998年   1630篇
  1997年   1487篇
  1996年   1233篇
  1995年   1062篇
  1994年   1053篇
  1993年   619篇
  1992年   638篇
  1991年   574篇
  1990年   478篇
  1989年   388篇
  1988年   295篇
  1987年   314篇
  1986年   268篇
  1985年   175篇
  1984年   102篇
  1983年   114篇
  1982年   79篇
  1981年   34篇
  1965年   38篇
  1964年   37篇
  1963年   38篇
  1959年   62篇
  1958年   49篇
  1957年   38篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
StudyontheRelationshipbetweenCytogeneticsandPhenotypicEffectinTurner'sSyndromeHUXiaofeng(胡晓峰);ZHUBaosheng(朱宝生);LINHanhua(林汉华)...  相似文献   
972.
OBJECTIVE: To analyse the clinical characteristics of patients who died on the Stanford heart transplant waiting list and to develop a method for risk stratifying status 2 patients (outpatients). METHODS: Data were reviewed from all patients over 18 years, excluding retransplants, who were accepted for heart transplantation over an eight year period from 1986 to 1994. RESULTS: 548 patients were accepted for heart transplantation; 53 died on the waiting list, and 52 survived on the waiting list for over one year. On multivariate analysis only peak oxygen consumption (peak VO2: 11.7 (SD 2.7) v 15.1 (5.2) ml/kg/min, P = 0.02) and cardiac output (3.97 (1.03) v 4.79 (1.06) litres/min, P = 0.04) were found to be independent prognostic risk factors. Peak VO2 and cardiac index (CI) were then analysed in the last 141 consecutive patients accepted for cardiac transplantation. All deaths and 88% of the deteriorations to status 1 on the waiting list occurred in patients with either a CI < 2.0 or a VO2 < 12. In those with a CI < 2.0 and a VO2 < 12, 38% died or deteriorated to status 1 in the first year on the waiting list. Patients with CI > or = 2.0 and a VO2 > or = 12 all survived throughout follow up. Using a Cox's proportional hazards model with CI and peak VO2 as covariates, tables were constructed predicting the chance of surviving for (a) 60 days and (b) 1 year on the waiting list. CONCLUSIONS: These data provide a basis for risk stratification of status 2 patients on the heart transplant waiting list.  相似文献   
973.
应用单向免疫扩散法测定了流行性出血热(EHF)患者的7种补体成份和血浆素原(Pg).结果表明,CT脂酶抑制剂在少尿期、多尿期和恢复期均高于正常(P<0.01);补体C_1q在多尿期高于正常(P<0.01);补体C_4在发热期和少尿期低于正常(P<0.01),以后逐渐恢复正常;补体C_3,C_5和C_9的变化与C_4相似;B因子在少尿期低于正常(P<0.01),在多尿期高于正常(P<0.05);Pg始终高于正常水平但在少尿期有回降.说明EHF患者不仅有补体经典途径的识别阶段、活化阶段和膜攻击阶段的变化,而且亦有旁路激活,其活化程度与病情有关.  相似文献   
974.
血管内氧合器的研制   总被引:2,自引:0,他引:2  
为了探索呼吸辅助的新方法,我们采用国产聚丙烯中空纤维,自行设计、制造模具,研制出一种血管内氧合器。该氧合器是一个小的、细长的可经单侧股静脉或颈静脉切开,置入腔静脉内的装置。氧合器有效长度40cm,膜交换面积0.09m^2。经负压调节通过血管内氧合器的氧流量,以防止纤维破裂造成的血管内气栓的危险。一根双腔导气管使气体经同一静脉切开部位循环,气体经内芯管流经血管内氧合器尖端,然后经中空纤维束流出。目前  相似文献   
975.
作者报告经病理诊断消化道恶性肿瘤患者30例及手术切除肿瘤患者15例的血浆胃动素水平,并以健康成人31例作为对照。消化道恶性肿瘤的胃动素水平373.4±123.7ng/L,显著高于正常对照组(162.3±52.3ng/L,P<0.001),而消化道恶性肿瘤患者术前及术后胃动素水平无显著差异。消化道恶性肿瘤患者胃动素水平增高的原因可能是肿瘤刺激神经所致。胃癌和结肠癌细胞可产生胃泌素样物质,它可刺激胃动素的释放。  相似文献   
976.
Cell-cell adhesion is essential for many immunological functions and is believed to be important in the regulation of hematopoiesis. Adhesive interactions between human endothelial cells and megakaryocytes were characterized in vitro using the CMK megakaryocytic cell line as well as marrow megakaryocytes. Although there was no adhesion between unactivated human umbilical vein endothelial cells (HUVEC) and megakaryocytes, treatment of HUVEC with inflammatory cytokines such as IL-1 beta, tumor necrosis factor alpha, INF-gamma, or the phorbol ester phorbol myristate acetate (PMA) resulted in a time- and dose-dependent increase in adhesion. Stimulation of marrow megakaryocytes or CMK cells with the cytokines IL-1 beta, GM-CSF, IL-6, IL-3, or PMA augmented their adhesion to endothelium. Monoclonal antibodies against the LFA-1 subunit of the leukocyte adherence complex CD18 inhibited the binding of marrow megakaryocytes or CMK cells to HUVEC. Adhesion blocking experiments also demonstrated that the VLA-4/VCAM-1 pathway was important for megakaryocyte attachment to HUVEC. Adhesion promoted maturation of megakaryocytic cells as measured by increased expression of glycoproteins GpIb and GpIIb/IIIa and by increased DNA content. These observations suggest that alterations in megakaryocyte adhesion may occur during inflammatory conditions, mediated by certain cytokines, resulting in augmented megakaryocyte maturation.  相似文献   
977.
本研究主要对El Tor型霍乱弧菌(Vibrio cholerae biotvpe eltor,EVC)L型的某些生物学特性如生化反应、抗生素敏感性及超微结构等进行了探讨.研究发现EVC不稳定L型的生化性状与EVC流行株的非常相似,而稳定L型则变化很大.抗生素敏感性试验显示EVC稳定L型对某些作用于细胞壁的抗生素的敏感性减弱,而对大多数作用于蛋白质合成的抗生素的敏感性增强.与流行株相比,EVC稳定L型和不稳定L型的超微结构的改变很明显.此外,本文还讨论了产生这些改变的可能机制.  相似文献   
978.
原发性干燥综合征与人类组织相容性抗原—DRβ基因   总被引:1,自引:0,他引:1  
原发性干燥综合征(PSS)的病因未明,其中可能涉及遗传因素。用序列特异性引物聚合酶链反应(PCR-SSP)法对70例PSS患者和136名正常人进行人类组织相容性抗原(HLA)-DRβ基因分型。发现PSS患者群体的HLA-DR3、DR52及DR2的基因频率明显高于正常对照组,而HLA-DR5及DR9的基因频率则相反,提示PSS的发病与DR3、DR52及DR2呈正相关;而和DR9、DR5呈负相关。2个PSS患者家族的姐妹与患者具有相同的遗传因素,且和PSS患者群体测定的正相关基因相一致。PSS患者的主要自身抗体(抗SSA抗体及抗SSB抗体)与HLA-DR52之间有明显的相关性,因而表明PSS的发病和遗传因素有关。  相似文献   
979.
Population toxicokinetics of tetrachloroethylene   总被引:1,自引:0,他引:1  
 In assessing the distribution and metabolism of toxic compounds in the body, measurements are not always feasible for ethical or technical reasons. Computer modeling offers a reasonable alternative, but the variability and complexity of biological systems pose unique challenges in model building and adjustment. Recent tools from population pharmacokinetics, Bayesian statistical inference, and physiological modeling can be brought together to solve these problems. As an example, we modeled the distribution and metabolism of tetrachloroethylene (PERC) in humans. We derive statistical distributions for the parameters of a physiological model of PERC, on the basis of data from Monster et al. (1979). The model adequately fits both prior physiological information and experimental data. An estimate of the relationship between PERC exposure and fraction metabolized is obtained. Our median population estimate for the fraction of inhaled tetrachloroethylene that is metabolized, at exposure levels exceeding current occupational standards, is 1.5% [95% confidence interval (0.52%, 4.1%)]. At levels approaching ambient inhalation exposure (0.001 ppm), the median estimate of the fraction metabolized is much higher, at 36% [95% confidence interval (15%, 58%)]. This disproportionality should be taken into account when deriving safe exposure limits for tetrachloroethylene and deserves to be verified by further experiments. Received: 20 April 1995/Accepted: 24 August 1995  相似文献   
980.
氧氟沙星及其胶囊的HPLC测定   总被引:7,自引:1,他引:6  
改进了氧氟沙星及其胶囊的HPLC测定条件。与卫生部药品标准方法相比,柱放大为提高,拖尾现象减小。  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