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   47836篇
  免费   3622篇
  国内免费   2441篇
耳鼻咽喉   254篇
儿科学   1356篇
妇产科学   471篇
基础医学   11209篇
口腔科学   387篇
临床医学   3642篇
内科学   13022篇
皮肤病学   578篇
神经病学   1215篇
特种医学   620篇
外国民族医学   7篇
外科学   2085篇
综合类   6275篇
现状与发展   18篇
预防医学   7014篇
眼科学   385篇
药学   2454篇
  12篇
中国医学   848篇
肿瘤学   2047篇
  2024年   45篇
  2023年   552篇
  2022年   1247篇
  2021年   2124篇
  2020年   1650篇
  2019年   1449篇
  2018年   1466篇
  2017年   1439篇
  2016年   1703篇
  2015年   2015篇
  2014年   2815篇
  2013年   2985篇
  2012年   2752篇
  2011年   3228篇
  2010年   2672篇
  2009年   2431篇
  2008年   2382篇
  2007年   2524篇
  2006年   2265篇
  2005年   1997篇
  2004年   1761篇
  2003年   1534篇
  2002年   1216篇
  2001年   1184篇
  2000年   961篇
  1999年   861篇
  1998年   754篇
  1997年   770篇
  1996年   627篇
  1995年   631篇
  1994年   594篇
  1993年   473篇
  1992年   354篇
  1991年   302篇
  1990年   269篇
  1989年   244篇
  1988年   231篇
  1987年   167篇
  1986年   142篇
  1985年   287篇
  1984年   180篇
  1983年   134篇
  1982年   120篇
  1981年   98篇
  1980年   68篇
  1979年   58篇
  1978年   51篇
  1977年   31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
101.
湖南省乙肝病毒基因型分布及临床意义   总被引:1,自引:0,他引:1  
目的 :研究湖南省乙肝病毒 (HBV)基因型分布及临床意义。方法 :选择湖南省HBVDNA阳性慢性乙肝病人共 185例 ,其中病毒携带者 (ASC) 4 2例 ,慢性轻、中度肝炎 (CH) 38例 ,重型肝炎 (FHF) 80例 (伴有肝硬化者 4 9例 ) ,肝细胞癌 (HCC) 2 5例 ,采用聚合酶链反应 限制性片段长度多态性 (PCR RFLP)方法检测HBV基因型。结果 :基因型B136例 (73.5 % ) ,基因型C 4 9例 (2 6 .5 % )。基因型B在FHF中占绝对优势 (83.7% ) ,其次为HCC(76 % ) ,与ASC(5 7.1% )比较 ,差异有显著性 (P <0 .0 1)。与基因型B相比 ,基因型C在垂直传播感染者中多见 (38.8%与 13.2 % ,P <0 .0 0 1) ;HBeAg阳性率明显增高 (5 7.1%与 30 .9% ,P <0 .0 0 1) ;抗HBe阳性率明显下降 (36 .9%与 6 6 .2 % ,P <0 .0 0 1)。与基因型C相比 ,基因型B感染者ALT水平明显增高 (2 6 4 .5± 2 5 6 .5与 10 0± 12 0 .6 ,P <0 .0 0 1)。结论 :湖南省存在乙肝病毒基因型B和基因型C ;基因型B为优势基因型并与肝脏疾病活动性相关 ,基因型C与母婴垂直传播感染有关  相似文献   
102.
Antibodies against nerve growth factor (NGF) in sera were detected by enzyme-linked immunosorbent assays (ELISA), by their isolation after passage of sera through NGF immunoadsorbent columns and by their specificity to bind and immunoprecipitate mouse NGF as well as to stain by immunohistochemical methods cellular sites of NGF synthesis. Increased levels of anti-NGF antibodies were found in sera of herpes simplex virus (HSV)-infected patients but not in HSV-inoculated rabbits. As HSV latency is known to be promoted by NGF in vitro, these results may suggest that anti-NGF antibodies modulate the cytokine function of NGF and thus might play a role in HSV infection. The biological function of circulating antibodies against NGF, in general, is now open to future investigation.  相似文献   
103.
本文通过免疫荧光(IF)和电镜(EM)技术对新疆出血热(XHF)及流行性出血热(EHF)病毒的生物学特性在Vero E_6及LLC-MK_2两株传代细胞上进行了比较。两种病毒感染两株细胞后免疫荧光染色有两种不同的荧光形态特征,两种病毒对细胞的敏感性明显不同,XHF病毒在LLC-MK_2细胞上感染后6~8天可出现明显的细胞病变,而EHF病毒感染此细胞后则不引起病变。电镜观察到两种病毒在LLC-MK_2细胞中都能形成与布尼病毒相似的形态特征。  相似文献   
104.
Different doses of hepatitis B virus vaccine—prepared by Korea Green Cross Corporation, were given to healthy infants born to HBsAg-negative mothers at birth, 1 and 6 months of age. A dose of 2 μg was administered intradermally in Group A and, in the three other groups, the vaccine was given intramuscularly (i.m.). An adequate follow-up observation was possible for 9 months after birth in 22, 25, 23 and 21 infants in Groups A, B, C and D, respecvely.
Group C (5 μg, i.m.) produced seroconversion most rapidly, showing the highest rate (96%) at 9 months of age. The lowest seroconversion rate (5%) was found at the age of 1 month in Group A subjects, but the rate increased to 91% after a booster dose was given at 6 months of age.
While it can be concluded that a 5 μg i.m. dose of vaccine at 0, 1 and 6 months of age is optimum for the immunization of infants in efficacy and economy, a 2 μg intradermal dose can also be considered as an immunogenic and economical regimen, though the immune response is slower and a special technique is required for immunization.  相似文献   
105.
以国内外发表的文献为材料,简述甘草酸在抗病毒方面研究进展。对甘草酸抗肝炎病毒、疱疹属病毒、HIV病毒及SAS病毒等机制进行了综述。甘草酸抗病毒活性强,能抑制多种不相关的DNA、RNA病毒的生长,并且不影响正常细胞的活性。但由于其脂溶性和生物利用度低,及长期使用会引起一些不良反应,而限制了它的应用。总的来说,甘草酸在抗病毒方面的前景良好,有其独特优势,但其抗病毒机制复杂,很多方面有待进一步研究。  相似文献   
106.
Summary.  Hepatitis B virus (HBV) circulates in blood as closely related, but genetically diverse molecules called quasispecies. During replication, HBV production may approach 1011 molecules/day, although during peak activity this rate may increase 100–1000 times. Generally, DNA polymerases have excellent fidelity in reading DNA templates because they are associated with an exonuclease which removes incorrectly added nucleotides. However, the HBV-DNA polymerase lacks fidelity and proofreading function partly because exonuclease activity is either absent or deficient. Thus, the HBV genome and especially the envelope gene, is mutated with unusually high frequency. These mutations can affect more than one open reading frame because of overlapping genes. The S gene contains an exposed major hydrophilic region (residues 110–155), which encompasses the 'a' determinant that is important for inducing immunity. Nucleotide substitutions in this region are common and result in reduced binding or failure to detect hepatitis B surface antigen (HBsAg) in diagnostic assays. Adaptive immunity also depends on the recognition of HBsAg by specific antibody and variants pose a threat if they interfere with binding to antibody. Finally, genomic hypervariability allows HBV to escape selection pressures imposed by antiviral therapies, vaccines and the host immune system, and is responsible for creating genotypes, subgenotypes and subtypes.  相似文献   
107.
With the introduction of more potent immunosuppressive agents, rejection has decreased in simultaneous pancreas/kidney transplant (SPK) recipients. However, as a consequence, opportunistic infections have increased. The purpose of this report is to outline the course of SPK patients who developed polyomavirus-associated nephropathy (PVAN). A retrospective review of 146 consecutive SPK recipients from January 1, 1996 to December 31, 2002 was performed. Immunosuppression, rejection and development of PVAN were reviewed. Nine patients were identified. All received induction with either OKT3 or thymoglobulin. Immunosuppression included tacrolimus/cyclosporine, MMF/azathioprine and sirolimus/prednisone. Two patients were treated for kidney rejection prior to the diagnosis of PVAN. Time to diagnosis was an average of 359.3 days post-transplantation. Immunosuppression was decreased but five ultimately lost function. However, none developed pancreatic abnormalities as demonstrated by normal glucose and amylase. Two underwent renal retransplantation after PVAN diagnosis and both have normal kidney function. PVAN was the leading cause of renal loss in SPK patients in the first 2 years after transplantation and is a serious concern for SPK recipients. The pancreas, however, is spared from evidence of infection, and no pancreatic rejection occurred when immunosuppression was decreased.  相似文献   
108.
目的构建并产生肿瘤血管抑制肽alphastatin(Al)重组腺伴随病毒(rAAV)载体。方法将目的基因alphastatin插入载体质粒pSSHG-巨细胞病毒(CMV)的EcoRI和BamHI位点,构建重组质粒pSSHG-CMV/NT4-Al。用腺病毒辅助质粒pFG140代替野生型腺病毒,包装质粒pAAV/Ad及已构建的重组腺伴随病毒载体质粒,使用三质粒共转染法转染293细胞,包装得到腺伴随病毒(AAV)-Al。采用氯仿抽提、聚乙二醇沉淀回收纯化,斑点杂交方法测定重组病毒滴度。结果重组病毒rAAV-Al滴度约为2×1012颗粒/ml。结论成功制备了重组病毒rAAV-Al,提供了一种生产足量安全的rAAV-Al简单易行的方法,为肿瘤的基因治疗实验奠定了基础。  相似文献   
109.
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   
110.
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   
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