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   8677篇
  免费   490篇
  国内免费   58篇
耳鼻咽喉   74篇
儿科学   199篇
妇产科学   108篇
基础医学   1127篇
口腔科学   289篇
临床医学   556篇
内科学   2170篇
皮肤病学   118篇
神经病学   549篇
特种医学   362篇
外科学   1712篇
综合类   23篇
现状与发展   1篇
预防医学   227篇
眼科学   80篇
药学   575篇
中国医学   10篇
肿瘤学   1045篇
  2023年   84篇
  2022年   162篇
  2021年   278篇
  2020年   151篇
  2019年   205篇
  2018年   254篇
  2017年   217篇
  2016年   218篇
  2015年   215篇
  2014年   265篇
  2013年   295篇
  2012年   446篇
  2011年   498篇
  2010年   267篇
  2009年   235篇
  2008年   394篇
  2007年   408篇
  2006年   400篇
  2005年   402篇
  2004年   379篇
  2003年   386篇
  2002年   324篇
  2001年   229篇
  2000年   217篇
  1999年   211篇
  1998年   91篇
  1997年   75篇
  1996年   73篇
  1995年   67篇
  1994年   60篇
  1993年   62篇
  1992年   156篇
  1991年   118篇
  1990年   141篇
  1989年   134篇
  1988年   116篇
  1987年   93篇
  1986年   105篇
  1985年   104篇
  1984年   72篇
  1983年   60篇
  1979年   52篇
  1978年   35篇
  1974年   34篇
  1973年   42篇
  1971年   35篇
  1970年   34篇
  1969年   34篇
  1967年   36篇
  1966年   34篇
排序方式: 共有9225条查询结果,搜索用时 15 毫秒
51.
52.
53.
The activities of RNase (RNase-U and RNase-C) were determined in the serum and leukocytes of 277 patients with 14 cases of various kinds of eosinophilia (not less than 10(3)/microliters), 28 cases of chronic myelocytic leukemia (CML), using polyuridylic acid and polycytidylic acid as synthetic substrates according to the method of Raddi et al. Serum RNase-U activity, serum RNase-C activity and the activity ratio (U/C x 10(-3)) were 55 +/- 14 U, 1,280 +/- 235 U and 44 +/- 11 (mean +/- SD), 196 +/- 137, 1,992 +/- 1,134 U and 97 +/- 38, and 110 +/- 50 U, 1,854 +/- 625 U and 65 +/- 13 for normal subjects, eosinophilia and CML (untreated), respectively. U/C ratio in eosinophilia and CML (untreated) showed a highly significant positive correlation (p less than 0.001) with peripheral eosinophil count; the activity of serum RNase-U per cells in the supernatant of eosinophil homogenate rose significantly (p less than 0.001) compared with that of lymphocytes or granulocytes. Besides, serum and eosinophil RNase-U had a similar optimal pH. These results suggested that serum RNase-U in eosinophilia originated mostly from eosinophils and its rise was correlated strongly with the increase in eosinophils.  相似文献   
54.
Summary Human cells doubly transformed by Rous sarcoma virus and SV40 (RSb cells) formed syncytia by cocultivation with Mason-Pfizer monkey virus (MPMV)-producing cells. This cell fusion was blocked by anti-MPMV serum indicating that the phenomenon is MPMV specific. The RSb cells were successfully used for MPMV infectivity assay in the same manner as KC cells.With 1 Figure  相似文献   
55.
The altered patterns of transfer RNA in SV40-infected and transformed cells   总被引:4,自引:0,他引:4  
T Sekiya  K I Oda 《Virology》1972,47(1):168-180
  相似文献   
56.
57.
58.
59.
A rare case of primary pulmonary synovial sarcoma with polypoid endobronchial growth in a 42-year-old Japanese woman is described. Left upper sleeve lobectomy was performed for the polypoid tumor measuring 2.5 cm in the left major bronchus and the patient was treated with adjuvant chemotherapy. Three years later, a recurrent tumor was discovered. Microscopically, this tumor was characterized by a proliferation of oval to spindle-shaped cells arranged in sheets and fascicles and covered by the thin normal bronchial epithelium. Immunohistochemically, tumor cells were positive for vimentin, and focally positive for pancytokeratin recognized by AE1/AE3, cytokeratin 7 and epithelial membrane antigen. A chimera gene, SYT-SSX1, was detected. Recently, primary pulmonary synovial sarcoma is an increasingly recognized clinical entity; however, most of these tumors present as a parenchymal mass. The present case is a unique example of primary synovial sarcoma of endobronchial polypoid type. This case suggests that pulmonary synovial sarcoma might originate from bronchial submucosal stromal tissue.  相似文献   
60.
We investigated the aberrant promoter hypermethylation of p16, p15 and p14 genes and loss of heterozygosity (LOH) at 9p21-22 in 48 cases of adenocarcinoma of the lung. The frequencies of hypermethylation of genes were as follows: p16, 25.0%; p15, 22.9%; and p14, 18.8%. The frequency of LOH at chromosome 9p21-22 was 60.9%. The frequency of two-hit inactivation of the p16 gene by hypermethylation and LOH was 21.7%. Two-hit inactivation of the p16 gene showed loss of protein expression and was significantly correlated with tumor size, tumor grade and the Ki-67 labeling index. Hypermethylation of the p16 gene was not significantly correlated with hypermethylation of the p15 and p14 genes, both of which are close to the p16 gene locus, suggesting that hypermethylation of these genes occurs selectivity. In conclusion, biallelic inactivation of the p16 gene by hypermethylation and LOH might cause loss of p16 expression and play an important role in the development of adenocarcinoma of the lung. Therefore, controlling and monitoring for hypermethylation of the p16 gene may be partially useful for treatment and early diagnosis of adenocarcinoma of the lung.  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