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   172975篇
  免费   16662篇
  国内免费   9949篇
耳鼻咽喉   1373篇
儿科学   3074篇
妇产科学   1068篇
基础医学   10800篇
口腔科学   3265篇
临床医学   21694篇
内科学   15807篇
皮肤病学   1942篇
神经病学   4275篇
特种医学   5934篇
外国民族医学   9篇
外科学   14538篇
综合类   46465篇
现状与发展   43篇
一般理论   4篇
预防医学   20852篇
眼科学   2354篇
药学   21387篇
  228篇
中国医学   16175篇
肿瘤学   8299篇
  2024年   786篇
  2023年   2118篇
  2022年   5287篇
  2021年   6623篇
  2020年   5962篇
  2019年   3618篇
  2018年   3642篇
  2017年   4788篇
  2016年   3768篇
  2015年   6704篇
  2014年   9069篇
  2013年   10706篇
  2012年   15383篇
  2011年   16317篇
  2010年   14755篇
  2009年   13258篇
  2008年   13589篇
  2007年   13211篇
  2006年   12022篇
  2005年   9529篇
  2004年   7005篇
  2003年   5767篇
  2002年   4463篇
  2001年   4098篇
  2000年   3023篇
  1999年   1298篇
  1998年   442篇
  1997年   443篇
  1996年   350篇
  1995年   253篇
  1994年   255篇
  1993年   168篇
  1992年   134篇
  1991年   92篇
  1990年   87篇
  1989年   82篇
  1988年   48篇
  1987年   64篇
  1986年   46篇
  1985年   47篇
  1984年   28篇
  1983年   32篇
  1982年   29篇
  1981年   18篇
  1980年   11篇
  1979年   11篇
  1975年   10篇
  1959年   15篇
  1958年   19篇
  1957年   14篇
排序方式: 共有10000条查询结果,搜索用时 36 毫秒
51.
Objective To study on adsorption effect of cadusafos and atropine sulfate by hemoperfusion.Method Hemoperfusions were performed for sheep blood samples with cadusafos and atropineby through imitated extracorporeal closed circulating perfusion apparatus.Residual cadusafos was determined by gas chromatography and residual atropine was determined by high performance liquid chromatography.Result Dose of adsorption agent was 0.5,1.0 and 1.5 g,respectively.Two hours after hemoperfusion with membrane coated activated charcoal,clearance rate of cadusafos in 3 groups all exceeded 90%.and clearance rate of atropine sulfate was 61.9%,84.9%,88.9%,respectively.One and a half hours after hemoperfusion with HA230 absorption resin,clearance rate of eadusafos in 3 groups all exceeded 90%,and clearance rate of atropine sulfate was 88.0%,97.2%,98.4%,respectively.Three hours after hemoperfusion with membrane coated activated charcoal,The concentration ratio of cadusafos and atropine sulfate in blood promoted to 10.1 times,and the ratio was 6.7 times after hemoperfusion with HA230 absorption resin.Conclusion It suggested that cadusafos were mostly removed from blood after 1.5~2.0hours hemoperfusion with membrane activated charcoal or HA230 absorption resin.The concentration ratio of cadusafos and atropine sulfate in blood will increased after hemoperfusion.  相似文献   
52.
180例根管治疗术失败原因分析   总被引:3,自引:0,他引:3  
根管治疗术是治疗牙髓病、根尖周病,保留患牙的最重要的治疗方法。临床上由于医务人员对牙体解剖形态以及根管治疗术的常规操作掌握不够熟练,操作失误常常导致患牙治疗失败。本文总结了我院自2002年5月至今接诊的156例病例,对180例根管治疗失败病例进行分析。现将结果报告如下。  相似文献   
53.
In order to improve 8-hydroxyguanine (8-OH-Gua) detection in DNA, we digested isolated DNA with nuclease P1 and analyzed for 8-hydroxydeoxyguanosine 5'-monophosphate (8-OH-dGMP) using a high-performance liquid chromatography system equipped with an electrochemical detector (HPLC-ECD). The amount of 8-OH-Gua in the DNA was expressed as the ratio of 8-OH-dGMP to deoxycytidine monophosphate (dCMP). Using this analysis, the background level of 8-OH-Gua in DNA from human lung carcinoma cells (A549) was several-fold lower than that obtained by a previous method. A549 cells were exposed to 20-60 Gy of gamma-radiation and an increase in 8-OH-Gua concentration was observed with increasing gamma-ray dose (0.3 residues per 10(7) dCMP per Gy). Moreover, by an immunohistochemical procedure using a commercial FITC-kit, 8-OH-Gua was clearly detected in A549 cells and the fluorescence intensity of cells with oxidative DNA damage increased with the doses of gamma-irradiation. Using an endonuclease nicking assay, we also found that gamma-rays decreased 8-OH-Gua repair activity. The results indicate that 8-OH-dGMP is a useful and sensitive marker for estimating oxidative damage in DNA.  相似文献   
54.
为了考察海藻酸钙/聚组氨酸微胶囊的毒性特征,我们利用MTT比色法和小鼠尾静脉注射法,分别考察了该微胶囊的细胞毒性和急性全身毒性。结果表明:微胶囊浓度≤1.0mg/mL时,材料对L929细胞生长无明显抑制作用;微胶囊浸提液即使在高浸提比(10.0mg/mL)下,浸提产物也无细胞毒性作用。急性全身毒性试验结果显示:微胶囊浸提液不引起急性全身毒性反应,表明微胶囊浸提液无有毒的沥滤物和降解产物产生。说明海藻酸钙/聚组氨酸微胶囊无明显毒性。  相似文献   
55.
目的:临床评价增殖性瘢痕的颜色需要定量测量.本实验主要研究增殖性瘢痕色度的测量方法,实现瘢痕颜色的定量测量,为临床诊治提供量化依据.材料与方法:采用以光电积分式测量原理设计的色彩分析仪对增殖性瘢痕患者19人,共65个测试点按不同部位分为四组进行色度测量,并与正常组对照.用CIE-XYZ色度标准表达测量值,配合色度图直接观察瘢痕的疗效.结果:增殖性瘢痕各部位组的色度坐标值与相应的对照组比较均有显著性差异(P<0.05).结论:本实验的测量方法是有效的,能准确、定量反映增殖性瘢痕颜色的变化.可用量化指标总结、分析、报告治疗结果.  相似文献   
56.
冷冻切片常遇到的问题及解决对策   总被引:4,自引:0,他引:4  
目的 提高制作冷冻切片质量,确保实验结果科学性。方法 通过对切片机工作室温度设置选择,防卷板的调整应用及切片常遇到的问题分析,阐述提高制作高质量冷冻切片的方法。结果 通过对冷冻切片机有关参数的设定,提高了切片质量。结论 冷冻切片常遇到的问题,通过及时调整切片机相应设置,可以便捷解决。  相似文献   
57.
Cell cycle “checkpoints” help to ensure the integrity of normal cellular functions prior to replicative DNA synthesis and/or cell division. Cell kinetic abnormalities, particularly arrests at the G1/S and G2/M cell cycle checkpoints, are induced following exposure to ionizing radiationin vitro. Following irradiation, cellular signaling pathways may lead to G1 arrest and/or apoptosis at the G1/S cell cycle transition point. Transfection of cyclin D1, a G1/S cyclin, into a rat embryo cells (REC) results in cellular populations that overexpress cyclin D1, are transformed morphologically, demonstrate an increased incidence of apoptosis, and are tumorigenic in immune-deficient mice. Despite such phenotypic changes, transfected cell populations maintain the itegrity of the G1 checkpoint following ionizing radiation. The transfected cells overexpressing Cyclin D1 have a statistically significant increase in the incidence of apoptosis as compared to parental REC strains or mock-transfected REC. The work provides further evidence of Cyclin D1 playing a critical role in maintaining the integrity of the G1/S checkpoint, via the activation of apoptotic pathways following exposure to ionizing radiationin vitro.  相似文献   
58.
Objective To evaluate the effect on myocardial protection of adenosine preconditioning in different route of administration through right jugular vein and left ventricle.Methods 48 SD rats were randomly divided into ischemia reperfusion group(blank control),ischemic preconditioning group(IP,positive control),adenosine venous infusion group,adenosine in ventricular group,normal saline(NS)venous infusion group(negative control I)and NS in ventricular group(negative control Ⅱ).The ischemia reperfusion rats model were established in vivo,and then changes of heart function,serum cardiac troponin T (cTnT),superoxide dismutase(SOD),malondialdehyde(MDA)and expression of nuclear factor KB(NF-kB) were observed.Results SOD in IP[(208.63±23.88)U/ml],adenosine venous infusion group [(178.27±11.56) U/ml]and adenosine in ventricular group[(191.31±28.14)U/ml]were significantly higher than that in the ischemia reperfusion group[(145.05±23.18)U/ml](P<0.05),cTnT,MDA and expression of NF-kB were lower than that in the ischemia reperfusion group (P<0.05).Heart function was significantly better than that in the ischemia reperfusion group(P<0.05);SOD in adenosine in ventricular group was significantly higher than that in adenosine venous infusion group(P<0.05).cTnT,MDA and expression of NF-kB were lower than that in adenosine venous infusion group (P<0.05).Conclusion Adenosine preconditioning may mimic protective effect of ischemic preconditioning. The effect on myocardial protection of adenosine in ventricular group was better than that of adenosine venous infusion group.  相似文献   
59.
目的从基因水平调查了中国华南、华北地区人群HLA-DQB1等位基因频率,并研究比较两地区人群HLA-DQB1多态性分布。方法采用深圳益生堂生物企业有限公司研制开发的“HLA-DQB1低分辨率分型基因芯片检测试剂盒”,应用聚合酶链反应.序列特异性引物+序列特异性寡核苷酸探针芯片检测技术,对700名南方地区的中国人和320名北方地区的中国人进行基因分型。结果鉴定了10个HLA-DQB1等位基因,获得了一组准确、科学的统计数据。结论得到了中国华南、华北地区人群HLA-DQB1等位基因频率差异的数据,证明中国人群HLA-DQB1*02,05,0601,0602,0603的分布南北差异有统计学意义(P〈0.05),为疾病相关性研究、人文科学研究提供了可靠的遗传学数据。  相似文献   
60.
目的探讨Fas蛋白在糖尿病大鼠脑缺血再灌注海马区神经元损伤中的表达及意义。方法健康雄性Wister大鼠60只,随机分为4组:①正常对照组,②假手术组,③脑缺血再灌注组(NIR),④糖尿病脑缺血再灌注组(DIR组);采用STZ诱导糖尿病和线栓法建立大脑中动脉闭塞(MCAO)模型,HE法观察海马CA1神经元缺失,用免疫组化方法检测Fas在糖尿病大鼠脑缺血再灌注海马神经元损伤中的表达。结果HE染色:正常对照与假手术组未见神经元缺失和细胞凋亡,DIR组与脑缺血再灌注组均见神经元缺失和神经细胞凋亡,而DIR组比脑缺血再灌注组神经元缺失严重(P<0.05)。正常对照与假手术组极少见Fas免疫染色阳性细胞,DIR组与脑缺血再灌注组明显见Fas免疫染色阳性细胞,且DIR组比脑缺血再灌注组多(P<0.05)。结论Fas介导的细胞凋亡可能是糖尿病脑缺血再灌注损伤后海马区神经元损伤的机制之一。  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