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   16636篇
  免费   1005篇
  国内免费   81篇
耳鼻咽喉   132篇
儿科学   428篇
妇产科学   418篇
基础医学   2627篇
口腔科学   662篇
临床医学   1380篇
内科学   3692篇
皮肤病学   341篇
神经病学   1966篇
特种医学   450篇
外科学   1460篇
综合类   41篇
一般理论   5篇
预防医学   1027篇
眼科学   274篇
药学   1351篇
中国医学   57篇
肿瘤学   1411篇
  2024年   18篇
  2023年   171篇
  2022年   398篇
  2021年   596篇
  2020年   361篇
  2019年   478篇
  2018年   577篇
  2017年   453篇
  2016年   525篇
  2015年   652篇
  2014年   739篇
  2013年   937篇
  2012年   1475篇
  2011年   1569篇
  2010年   781篇
  2009年   743篇
  2008年   1175篇
  2007年   1096篇
  2006年   1020篇
  2005年   928篇
  2004年   834篇
  2003年   754篇
  2002年   642篇
  2001年   75篇
  2000年   54篇
  1999年   70篇
  1998年   105篇
  1997年   94篇
  1996年   60篇
  1995年   57篇
  1994年   42篇
  1993年   30篇
  1992年   19篇
  1991年   16篇
  1990年   12篇
  1989年   23篇
  1988年   15篇
  1987年   22篇
  1986年   14篇
  1985年   14篇
  1984年   11篇
  1983年   15篇
  1982年   13篇
  1981年   12篇
  1980年   5篇
  1979年   5篇
  1978年   4篇
  1975年   3篇
  1973年   6篇
  1961年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
We describe two unrelated patients with cytogenetically visible deletions of 21q22.2-q22.3 and mild phenotypes. Both patients presented minor dysmorphic features including thin marfanoid build, facial asymmetry, downward-slanting palpebral fissures, depressed nasal bridge, small nose with bulbous tip, and mild mental retardation (MR). FISH and molecular studies indicated common deleted areas but different breakpoints. In patient 1, the breakpoint was fine mapped to a 5.2 kb interval between exon 5 and exon 8 of the ETS2 gene. The subtelomeric FISH probe was absent on one homologue 21 indicating a terminal deletion spanning approximately 7.9 Mb in size. In patient 2, the proximal breakpoint was determined to be 300-700 kb distal to ETS2, and the distal breakpoint 2.5-0.3 Mb from the 21q telomere, indicating an interstitial deletion sized approximately 4.7-7.3 Mb. The 21q- syndrome is rare and typically associated with a severe phenotype, but different outcomes depending on the size and location of the deleted area have been reported. Our data show that monosomy 21q of the area distal to the ETS2 gene, representing the terminal 7.9 Mb of 21q, may result in mild phenotypes comprising facial anomalies, thin marfanoid build, and mild MR, with or without signs of holoprosencephaly.  相似文献   
22.
23.
Sponge immunocyte identification is of interest to comparative immunologists since characterizing these cells will allow investigations into the mechanisms of non-self recognition in the oldest animal phylum. Here, we report that polyclonal antibodies raised against the core protein of a proteoglycan involved in cell adhesion in the marine sponge Microciona prolifera are specific markers for archaeocytes, the totipotent sponge cells. Archaeocytes are mobilized upon allogeneic contact and they accumulate in the contact zone. A second type of cell, the gray cells, are specifically recognized by monoclonal antibodies raised against CD44, a hyaluronan receptor. Gray cells do also accumulate in the contact area. Specific staining of a third sponge cell type, the rhabdiferous cells, shows that these do not accumulate upon allografting. These specific cell markers allow tracking of archaeocytes and gray cells, and show that they play an active role in sponge allogeneic reactions.  相似文献   
24.
25.
26.
27.
We report a new case of mesothelioma that presented with an isolated lingual metastasis 14 months after initial diagnosis. The patient was a 71-year-old man with a history of pleural decortication and chemotherapy for epithelioid mesothelioma who recently complained of chronic bleeding from a nodular consolidation of tongue. There was no clinical or instrumental evidence of extrathoracic tumor spread. Microscopic examination of a lingual biopsy specimen revealed nests of atypical polygonal cells with moderate cytoplasm, immunopositive for keratins, epithelial membrane antigen, vimentin, thrombomodulin, and calretinin. This case provides additional evidence that mesothelioma could rarely, but not exceptionally, metastatize, to unusual sites such as the tongue. In that location it can mimic primary poorly differentiated squamous carcinoma or adenocarcinoma as well as a number of other metastatic malignancies. In addition to obvious medicolegal implication, metastatic mesothelioma should be correctly recognized so as to avoid useless radical treatment.  相似文献   
28.
Although the haemagglutination inhibition assay is considered the "gold standard" for antigenic characterisation of influenza viruses, some limitations of this technique are well known. A new microneutralisation assay, as a tool for antigenic characterisation of influenza B viruses, has been standardised and its performance evaluated in comparison with the haemagglutination inhibition test in the light of molecular characterisation of the haemagglutinin. Twelve B viruses belonging to the two lineages and the four sub-lineages discriminated by phylogenetic analysis of HA were tested. The microneutralisation assay clearly distinguishes viruses belonging to different lineages and, in addition, discriminates strains belonging to different sub-lineages that are poorly or not discriminated using the haemagglutination inhibition test. This new microneutralisation assay could provide a useful tool for antigenic characterisation of circulating influenza viruses and contribute, together with the haemagglutination inhibition test and sequence analysis of the haemagglutinin and neuraminidase, in the choice of the strain for use in vaccine composition.  相似文献   
29.
E-selectin, an adhesion molecule of the selectin family, is involved in leukocyte adhesion to the endothelium and in the cellular immunological reactions. Expression of this molecule, in fact, is physiologically absent, but it becomes evident on sinusoidal lining cells during inflammatory liver disease. The aim of this study was to evaluate the behavior of E-selectin in chronic hepatitis C (CH-C) patients with persistently normal transaminase in comparison to patients with CH-C and elevated transaminase, and its changes during alpha-interferon therapy. Immunohistochemical localization of E-selectin was also performed on liver tissue specimens of both groups. Fifty-eight subjects were divided into 3 groups: group A included 18 patients with CH-C and persistently normal transaminase; group B 20 patients with CH-C and persistently elevated transaminase levels and group C included 20 healthy subjects, representing the control group. The first two groups were treated with r-IFN at a dose of 6 MU 3 times a week for 3 months and followed-up with 3 MU 3 times a week for another 3 months. Serum baseline values of E-selectin in groups A and B were significantly higher than those in group C (P < 0.04), but there was no difference between groups A and B. Furthermore, there was a trend toward higher E-selectin values as histological severity increased (r = 0.69; P < 0.0001). Post-treatment E-selectin serum values showed a moderate decrease in both groups, but only among responder patients; while E-selectin levels were unchanged in non responders. Immunohistochemical localization showed no staining for E-selectin in normal liver specimens, while there was a quite similar staining for E-selectin in the two groups of patients. In conclusion, this study shows that serum E-selectin levels in patients with CH-C and persistently normal transaminase are higher than in controls and they are associated with severity of liver disease. Liver of these patients express E-selectin molecules, suggesting an activation of the immune system almost identical to that of patients with CH-C and elevated transaminase. In both groups only responder patients showed a moderate decrease below baseline serum values.  相似文献   
30.
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