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   39294篇
  免费   2607篇
  国内免费   2307篇
耳鼻咽喉   285篇
儿科学   912篇
妇产科学   511篇
基础医学   5095篇
口腔科学   878篇
临床医学   3939篇
内科学   7025篇
皮肤病学   1227篇
神经病学   1512篇
特种医学   922篇
外国民族医学   6篇
外科学   2435篇
综合类   6646篇
现状与发展   3篇
预防医学   2142篇
眼科学   403篇
药学   6790篇
  13篇
中国医学   1727篇
肿瘤学   1737篇
  2024年   117篇
  2023年   566篇
  2022年   1370篇
  2021年   1603篇
  2020年   1471篇
  2019年   1130篇
  2018年   1110篇
  2017年   1204篇
  2016年   1165篇
  2015年   1211篇
  2014年   2473篇
  2013年   2212篇
  2012年   2180篇
  2011年   2563篇
  2010年   2086篇
  2009年   1864篇
  2008年   2017篇
  2007年   2103篇
  2006年   1782篇
  2005年   1769篇
  2004年   1401篇
  2003年   1329篇
  2002年   1139篇
  2001年   1018篇
  2000年   950篇
  1999年   854篇
  1998年   810篇
  1997年   739篇
  1996年   577篇
  1995年   610篇
  1994年   524篇
  1993年   388篇
  1992年   358篇
  1991年   242篇
  1990年   172篇
  1989年   120篇
  1988年   113篇
  1987年   107篇
  1986年   83篇
  1985年   106篇
  1984年   109篇
  1983年   85篇
  1982年   83篇
  1981年   69篇
  1980年   51篇
  1979年   42篇
  1978年   23篇
  1977年   35篇
  1976年   34篇
  1973年   14篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
The inhibiting compounds were separated by micro-column liquid chromatography in the mobile phase containing the natural substrate acetylcholine. A home-made packed bed microbioreactor system containing immobilized enzyme acetylcholinesterase (ACHE) in human red blood cell membrane and choline oxidase (CHO) from alcaligenes was used for the post-column conversion of acetylcholine to hydrogen peroxide which was detected by an electrochemical detector. The inhibition effect of the solutes caused a decrease in the acetylcholinesterase activity, a decrease in the formation of hydrogen peroxide and also a decrease in the response corresponding to the concentration of the solutes. The rate of the enzyme regeneration was also recorded. The micro-system was compared with a conventional LC system comprising commercially prepared enzyme reactor. The stability of the enzymes is at least 3 weeks at ambient temperature. The limit of detection depends on biological activity of inhibition and for galanthamine was 1 pmol.  相似文献   
102.
The nitric oxide synthase (NOS) gene is thought to be associated with essential hypertension (EH), because NO is implicated in endothelium-mediated vasodilation. We investigated the possible association between the alleles of simple tandem repeat DNA polymorphism of the endothelial constitutive NOS (cNOS) gene and EH in Japanese subjects. In all, 100 patients with EH and 123 subjects with normal blood pressure were studied. Polymerase chain reaction was used to amplify the CA repeat site in the endothelial cNOS gene and alleles based on the CA repeat number were determined. The allele frequencies in the hypertensive group and normotensive group were then compared. Twenty-three alleles were identified in this study of Japanese subjects. The overall distributions of allele frequencies in the two groups were not significantly different. However, comparing the allele frequencies in the EH group without left ventricular hypertrophy (LVH) and the normotensive group, the overall distributions were significantly different (p = 0.019). The 33-repeat allele was found more frequently in the EH group without LVH than in the normotensive group (p = 0.000047, Odds ratio = 3.71). In conclusion, the 33-repeat allele of the endothelial cNOS gene is associated with EH without LVH, and may be a genetic marker of EH in Japanese subjects.  相似文献   
103.
104.
去白细胞输血预防非溶血性发热性输血反应的临床应用   总被引:14,自引:5,他引:9  
目的:评价临床输注法去白细胞红细胞悬液和浓缩血小板预防非溶血性发热性输血反应(FNHTR)的效果。方法:选择100例肝硬化、胃溃疡和胃癌等病人输注去白细胞红细胞悬液,对照组相类似50例病人输注普通红细胞悬液。240例急慢性白血病、再生障碍性贫血、多发性骨髓瘤、血小板减少性紫癜、糖尿病、肝硬化、上消化道出血、重症肝炎、烧伤、癌症放、化疗等患者分为两组,各组120例随机接受去白细胞血小板或未去白细胞血小板悬液。观察这些患者FNHTR的发生率。结果:在100例接受去白细胞红细胞悬液的患者中未发生FNHTR,对照组50例患者中有8例发生FNHTR,发生率为16%;血小板输注的患者中,去白细胞和未去白细胞的FNHTR发生7例和25例,发生率分别为5.83%和20.83%。结论:去白细胞输血可防止或减低FNHTR的发生。  相似文献   
105.
Summary The efficiency of cold storage red blood cells (CSRBC) or whole blood at −80 °C used in 27 Rh(D) negative patients during surgical operation was reported. The Rh(D) negative patients received the transfusion of CSRBC or whole blood stored at −80 °C for 180 to 360 days. The changes in the indexes, such as blood TB, DB, K+, Na+, BUN, Cr, urine protein (URPO), UOB, Hb, HCT, serum total protein, relative to hemolytic reaction and blood volume before and after transfusion were observed. The results showed that after transfusion of CSRBC or whole blood 27 cases were negative for urine protein and UOB, and the levels of BUN and Cr were normal (P>0.05). Blood TB, DB, Hb, and HCT were increased, while pH, blood K+ and blood Na+ was normal with the difference being not significant before and after operation (P>0.05). Plasma protein was decreased, but there was no significant difference before and after operation (P>0.05). It was suggested that CSRBC or whole blood at −80 °C could be safely infused to the Rh(D) negative patients without side effects during the surgical operation. YU Zhongqing, male, born in 1957, Technician in Charge  相似文献   
106.
The purpose of the present study was to determine whether lymphokine activated killer (LAK) cells were involved in the development of coxsackievirus B3 (CB3) myocarditis in both the acute viremic (Experiment I) and the subacute aviremic (Experiment II) stages. To induce LAK cells, recombinant human interleukin-2 (IL-2) was administered to CB3-infected mice subcutaneously daily, starting on day 0 in Experiment I and on day 7 in Experiment II for 7 days, respectively. The treated groups were compared to infected controls. Splenic lymphocytes of IL-2 treated mice were further cultured in vitro in IL-2 containing medium for 7 days, and LAK cell activity, i.e., cytotoxic activity of the lymphocytes against EL-4 tumor cells and against cultured fetal myocytes, was assayed by51Cr-release method. In Experiment I, histologic scores, myocardial virus titers, and LAK cell activity did not differ significantly between IL-2 treated and untreated groups. In contrast, in Experiment II, there were more cellular infiltration associated with severe necrosis and higher LAK cell activity against EL-4 cells and cultured myocytes in IL-2 treated than in untreated groups. The presence of LAK cells was demonstrated in the subacute stage of murine CB3 myocarditis. Thus, the behavior of LAK cell activity may vary with the course of myocarditis, and enhanced LAK cell activity may be involved in the development of the disease.This work was supported by research grants from the Conference on Coronary Artery Disease, Japanese Education of Science and Walfare (Nos. 08877110 and 09470164), Kanae Shinyaku Foundation, and Japan Cardiovascular Research Foundation.  相似文献   
107.
The effects of concurrent graft-versus-host reaction (GvHR) on the course of Giardia infection in CBA x BALB/c F1 mice have been examined, to test the hypothesis that T-cell-mediated immunity, in the form of a local DTH reaction, alters the host-parasite relationship in favour of the host by changing the physical environment of the parasite. GvHR did not enhance immunity, indeed mice infected with Giardia at a late stage of GvHR had significantly higher faecal cyst excretion and prolongation of the plateau phase of infection, indicating a degree of immunodeficiency.  相似文献   
108.
男性不育症患者中YRRM2基因缺陷的研究   总被引:2,自引:1,他引:1  
YRRM基因是控制精子生成与成熟的一个重要因素,一旦该基因缺陷,将会造成无精或少精。本研究对340例无精与少精患者的外周血标本进行了PCR基因扩增筛查,结果发现7例为该基因缺陷,占2%。证明YRRM2的缺陷也是造成中国人群男性不育的一个原因,从而可作为指导医生采用适当治疗方法的一个可靠指标。在实验过程中,采用直接加热白细胞提取基因组DNA,并以此作为模板对YRRM2基因进行扩增,既节省时间和经费,又保持良好的扩增效果,使之可用于临床医院作为常规检查。  相似文献   
109.
The clinical and electrophysiological features of a truncal myoclonus in a 55-year-old man are described. The electromyographic characteristics point toward propriospinal myoclonus. It is suggested that a myoclonic generator was released after use of ciprofloxacin, by antagonising the gamma-aminobutyric acid metabolism.  相似文献   
110.
不同脑保护方法中炎症反应对脑组织的影响   总被引:1,自引:1,他引:0  
目的 通过观察体外循环中采用不同脑保护方法时脑组织中各种炎性细胞因子的变化,探讨脑保护对炎症反应的影响。方法 将18只健康成年杂种犬随机均分为3组:常温体外循环组(normothermic cardiopulmonary bypass,NCPB组),深低温停循环组(deep hypothermic circulatory arrest,DHCA组),深低温停循环+间断选择性顺行性脑灌注组(intermittent selective antegrade cerebral perfusion,ISACP,DHCA+ISACP组)。术后检测犬脑组织的含水量,分离并取出海马,制备脑组织匀浆,采用放射免疫法测定白细胞介素-1β(IL-1β)和肿瘤坏死因子-α(TNF—α)的含量。在透射电子显微镜(TE)下检测海马脑组织的细胞形态学变化。结果 DHCA组的IL-1β和TNF—α含量明显高于NCPB组和DHCA+ISACP组(P〈0.01),但NCPB组与DHCA+ISACP组间比较差别无统计学意义(P〉0.05);TNF—α和IL-1β含量与脑水肿的程度呈正相关(r=0.987,0.942;P〈0.01)。TE检查显示DHCA组超微结构破坏较严重,而NCPB组和DHCA+ISACP组破坏较轻。结论 长时间DHCA会造成脑损伤,DHCA+ISACP有一定的脑保护作用,IL-1β和TNF—α在长时间DHCA中对脑损伤起一定的作用。  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