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   48214篇
  免费   3644篇
  国内免费   2450篇
耳鼻咽喉   259篇
儿科学   1363篇
妇产科学   471篇
基础医学   11258篇
口腔科学   390篇
临床医学   3657篇
内科学   13235篇
皮肤病学   581篇
神经病学   1216篇
特种医学   622篇
外国民族医学   7篇
外科学   2093篇
综合类   6296篇
现状与发展   18篇
预防医学   7042篇
眼科学   386篇
药学   2460篇
  12篇
中国医学   849篇
肿瘤学   2093篇
  2024年   46篇
  2023年   553篇
  2022年   1491篇
  2021年   2132篇
  2020年   1654篇
  2019年   1454篇
  2018年   1469篇
  2017年   1444篇
  2016年   1705篇
  2015年   2022篇
  2014年   2829篇
  2013年   2993篇
  2012年   2757篇
  2011年   3239篇
  2010年   2678篇
  2009年   2436篇
  2008年   2384篇
  2007年   2531篇
  2006年   2273篇
  2005年   2000篇
  2004年   1764篇
  2003年   1542篇
  2002年   1219篇
  2001年   1186篇
  2000年   962篇
  1999年   863篇
  1998年   755篇
  1997年   772篇
  1996年   631篇
  1995年   634篇
  1994年   597篇
  1993年   477篇
  1992年   357篇
  1991年   307篇
  1990年   270篇
  1989年   244篇
  1988年   231篇
  1987年   168篇
  1986年   143篇
  1985年   289篇
  1984年   181篇
  1983年   136篇
  1982年   123篇
  1981年   100篇
  1980年   70篇
  1979年   58篇
  1978年   51篇
  1977年   32篇
  1976年   31篇
  1975年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
The correlation between microscopic changes with cellular localization of viral antigens was studied in the ileum of 16 cases infected with bovine viral diarrhea virus (BVDV). Microscopic lesions in the ileum included multifocal erosive and ulcerative ileitis, severe congestion and hemorrhage, crypt dilation and mucus engorgement, epithelial debris and leukocytes, lymphoid depletion of Peyer’s patches, herniation of mucosal epithelium into depleted Peyer’s patches, and fibrinoid vasculitis of submucosal vessels. BVDV antigen was detected by immunohistochemistry in macrophages, dendritic cells, smooth muscle cells, endothelial cells, epithelial cells of crypts, and mucosal epithelium, together with other mononuclear cells including lymphocytes, plasma cells, fibroblasts, and intramural ganglial cells. No consistent correlation between the presence of BVDV antigen and vascular lesions in the ileum was identified. The intensity and distribution of the immunoperoxidase stain in the ileum was graded as highly positive (18.7%), moderately positive (56.3%), and mildly positive (25%). In conclusion, the pattern and density of distribution and localization of BVDV antigen in the ileum was not consistently correlated with the severity of microscopic lesions.  相似文献   
112.
Major Depressive Disorder (MDD) is among the most prevalent but underdiagnosed psychiatric disorders in persons with HIV infection. Given the known adverse impact of comorbid MDD on HIV disease progression and health‐related quality of life, it is important both for research and for efficient, effective clinical care, to validate existing screening measures that may discriminate between MDD and the somatic symptoms of HIV (such as fatigue). In the current study, we evaluated the concurrent predictive validity of the Profile of Mood States (POMS) Depression‐Dejection scale in detecting current MDD in 310 persons with HIV infection. The Structured Clinical Interview for DSM‐IV (SCID) diagnosis of MDD and the Cognitive‐Affective scale from the Beck Depression Inventory (BDI‐CA) served as comparative diagnostic and severity measures of depression, respectively. Results demonstrated that the POMS Depression‐Dejection scale accurately classified persons with and without MDD SCID diagnoses, with an overall hit rate of 80%, sensitivity of 55%, specificity of 84%, and negative predictive power of 91% using a recommended cutpoint of 1.5 standard deviations above the normative mean. Moreover, the POMS performed comparably to the BDI‐CA in classifying MDD. Findings support the predictive validity of the POMS Depression‐Dejection scale as a screening instrument for MDD in persons with HIV disease. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
113.
We studied 44 cases of Hodgkin's disease for the presence of Epstein-Barr virus (EBV) DNA, its localization and the expression of the EBV receptor on the tumour cells. EBV DNA was found in 52% (16/31) of the Hodgkin's lymphomas using the polymerase chain reaction. With a very sensitive non-radioactive DNA in situ hybridization technique in combination with immunohistochemistry for CD 30 or CD 15 antigens, EBV DNA was localized to Reed-Sternberg cells and its mononuclear variants. The relationship between the presence of EBV DNA and the expression of the EBV-receptor CR2 (CD 21) on Reed-Sternberg cells was studied using the same techniques and two different monoclonal anti-CD 21 antibodies. CR2 could be detected on a substantial number of the Reed-Sternberg cells in EBV DNA positive Hodgkin's lymphomas (9/12; 75%), whereas in EBV negative cases positivity with anti-CD 21 was rare (1/13; 8%). The results indicate that CR2 expression on Reed-Sternberg cells and the presence of EBV DNA sequences are frequently associated in Hodgkin's lymphomas.  相似文献   
114.
刘伟  赵伟  罗婵 《陕西医学杂志》2004,33(12):1099-1101
目的 :检测不明原因持续肝功能异常患者肝组织和其外周血单核细胞中 HBVDNA。方法 :采用原位分子杂交技术 ,分别检测随机选择的 40例不明原因持续肝功能异常患者外周血单核细胞和其肝组织中 HBV DNA。结果 :40例不明原因持续肝功能异常患者肝组织中 HBV DNA阳性 2 4例 ,阳性率为 5 8% ;外周血单核细胞中 HBV DNA阳性 1 8例 ,阳性率为 45 % ;两者比较 ,差异无显著性。结论 :对肝组织和外周血单核细胞进行 HBVDNA检测 ,有助于诊断隐性 HBV感染 ,后者对患者侵袭性小 ,取样简便。  相似文献   
115.
D2-43病毒E蛋白在酵母细胞表面的展示   总被引:2,自引:0,他引:2  
目的:在酵母细胞表面展示登革2型病毒43株(D2—43)的E基因,探索利用酵母表面展示系统建立DNA改组筛选平台的可行性。方法:通过RT-PCR扩增获得D2-43的E基因,将该基因亚克隆至T载体后,再克隆至酵母表面展示载体pYDI,于酿酒酵母EBY100中利用半乳糖进行诱导表达。表达产物采用间接免疫荧光法和FACS进行检测。结果:酵母表面展示产物可与D2-43的腹水抗体特异性地结合;在半乳糖诱导后24h,展示E蛋白的酵母细胞百分数达22.07%。结论:本研究为建立基于酵母表面展示系统的DNA改组筛选平台奠定了基础。  相似文献   
116.
The seroepidemiological profile of HBV and HDV was investigated in 640 male haemophiliacs. Twenty-seven of forty-four HBsAg carriers were anti-HDV-IgG positive, 22 were also anti-HDV-IgM positive. A markedly lower prevalence of HDV infection was found in patients with anti-HBc in the absence of HBsAg and anti-HBs (6/41). Repeated detection of anti-HDV-IgM in 5/41 individuals of this group indicates that circulating HBsAg is not an absolute prerequisite for chronic HDV infection. Overall, chronically active HDV infection was detected more frequently in quiescent than in active chronic HBV infections. Anti-HDV-IgM was not detected in the absence of anti-HDV-IgG antibodies. Anti-HDV-IgG may disappear after resolution of HDV infection, as indicated by the low prevalence (1/42) in such individuals with past HBV infection as well as by loss of anti-HDV-IgG observed in two patients.  相似文献   
117.
目的 探讨血清乙型肝炎病毒标志物不同表现模式对肾移植受者长期存活的影响。方法 对 62例血清乙型肝炎病毒标志物阳性者及 1 96例血清乙型肝炎病毒标志物全阴性者肾移植术后的肝功能、人肾均存活的存活率等指标进行随访和回顾性分析。结果 术后早期血清乙型肝炎病毒标志物阳性组与血清乙型肝炎病毒标志物阴性组比较 ,肝功能异常发生率的差异无显著性 (P >0 .0 5) ;术后中远期 ,HBsAg、HBeAg及抗 HBc阳性者的肝功能受损率明显高于血清乙型肝炎病毒标志物阴性组及HBsAg、抗 HBe、抗 HBc阳性者 (P <0 .0 5) ,其人肾均存活的存活率也最低 (P <0 .0 5)。结论 对HBsAg、抗 HBe及抗 HBc阳性者进行肾移植应慎重 ,而HBsAg、HBeAg及抗 HBc阳性者则不适宜接受肾移植  相似文献   
118.
臭氧水对SARS病毒的灭活效果观察   总被引:7,自引:0,他引:7  
为了观察电解法产生的臭氧水对SARS病毒的灭活效果,采用悬液灭活试验法进行了试验。结果,以臭氧含量为27.73mg/L,作用4min可完全灭活SARS病毒;以臭氧含量为17.82mg/L,作用4min和4.86mg/L作用10min,均可使SARS病毒的灭活率达100%。结论,电解法产生的臭氧水含臭氧量达到4.86mg/L以上,对悬液内SARS病毒具有很强的灭活效果。  相似文献   
119.
Employing HPLC fluorometry, gas-liquid chromatography (GLC) and a novel enzymelinked immunosorbent assay (ELISA) based on a monoclonal antibody, 40 corn samples, each collected in 1993 from agricultural stocks for human consumption in Haimen (Jiangsu County) and Penlai (Shandong Province), high- and low-risk areas for primary liver cancer (PLC) in China, respectively, were analysed for fumonisins (FBs), aflatoxins (AFs) and trichothecenes. Levels and positive rates of FBs and deoxynivalenol (DON) were significantly higher in Haimen than in Penlai. ELISA of the 40 corn samples harvested in the two areas in 1994 revealed that FB contamination levels and rates in these areas were comparable to those observed in 1993 in Haimen. ELISA analysis of 1993 and 1994 products revealed a wide occurrence of AFB1 but the positive rates as well as levels were not significantly different between these areas. ELISA of the same sample number of corn harvested in 1995 revealed that FB contamination in Haimen was significantly higher than in Penlai. These 3-yearly surveys of corn samples (240 in total) demonstrated that corn harvested in Haimen was highly contaminated with FBs and that the contamination level, as well as positive rate in 1993 and 1995, were 10–50-fold higher than those in Penlai, suggesting FBs as a risk factor for promotion of PLC in endemic areas, along with the trichothecene DON. Co-contamination with AFs, potent hepatocarcinogens, was assumed to play an important role in the initiation of hepatocarcinogenesis.  相似文献   
120.
以地高辛甙元随机引物法标记HBV-DNA探针,以此探针检测慢性乙型肝炎患者的血清、肝组织,同时以ELISA法检测血清HBeAg、HBcAb。结果:血清NBeAg阳性率27%(10/37),血清HBV-DNA检出率57.1%(20/35),两者有显著性差异。血清HBcAb阳性率78.4%(29/37),肝组织HBV-DNA检出率83.8%(31/37),两者无显著性差异。血清与肝组织HBV-DNA检出率有显著性差异。提示:血清HBV-DNA检测是较HBeAg更为准确客观反映血液带毒状况的指标。而准确反映肝脏带毒状况的指标是肝组织HBV-DNA检测。当HBeAg阴转,血清HBV-DNA阴性而肝组织HBV-DNA阳性时,需注意肝硬化及肝癌的发生。  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