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   25217篇
  免费   2213篇
  国内免费   80篇
耳鼻咽喉   233篇
儿科学   510篇
妇产科学   352篇
基础医学   3492篇
口腔科学   763篇
临床医学   2730篇
内科学   5076篇
皮肤病学   362篇
神经病学   2253篇
特种医学   1272篇
外科学   3871篇
综合类   406篇
一般理论   22篇
预防医学   1963篇
眼科学   684篇
药学   1677篇
中国医学   19篇
肿瘤学   1825篇
  2023年   145篇
  2022年   285篇
  2021年   595篇
  2020年   361篇
  2019年   505篇
  2018年   577篇
  2017年   461篇
  2016年   510篇
  2015年   632篇
  2014年   804篇
  2013年   1042篇
  2012年   1668篇
  2011年   1712篇
  2010年   998篇
  2009年   937篇
  2008年   1432篇
  2007年   1529篇
  2006年   1360篇
  2005年   1326篇
  2004年   1195篇
  2003年   1139篇
  2002年   949篇
  2001年   532篇
  2000年   547篇
  1999年   458篇
  1998年   237篇
  1997年   214篇
  1996年   173篇
  1995年   159篇
  1994年   159篇
  1993年   146篇
  1992年   308篇
  1991年   291篇
  1990年   268篇
  1989年   251篇
  1988年   244篇
  1987年   249篇
  1986年   207篇
  1985年   239篇
  1984年   207篇
  1983年   164篇
  1982年   136篇
  1981年   119篇
  1979年   200篇
  1978年   130篇
  1977年   134篇
  1976年   107篇
  1973年   132篇
  1972年   116篇
  1971年   116篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
The cattle major histocompatibility complex (MHC) class II DR gene product is a heterodimer encoded by the BoLA-DRA and -DRB3 genes. Several groups have isolated cDNA and genomic clones for these genes, but their full genomic organization has not been described. We used a combination of long-range polymerase chain reaction (PCR), cloning and sequencing to define the organization of the DRB3 gene on existing genomic clones and in genomic DNA. We estimate the size of the coding region to be 11.4 kbp. Sequencing of full-length PCR clones from two different haplotypes confirmed that they carried complete DRB3 genes and allowed the design of probes and primers to isolate and characterize the DRB3 promoter and 3' end. Fragments carrying the 5' end of the DRB3 gene and its promoter were identified on bacterial artificial chromosome (BAC) clones carrying the BoLA-DR genes. A 10-kbp promoter fragment was subcloned from one clone and a 1.7-kbp region including exon 1 and the promoter was sequenced. A 3-kbp fragment encoding exons 4-6 and the entire 3' untranslated region of the DRB3 gene was isolated from lambda clone A1 and sequenced. This provides us with improved characterization of the DRB3*0101 and DRB3*2002 alleles, and also subcloned 5' and 3' flanking regions of the polymorphic DRB3 gene for use in functional studies.  相似文献   
92.
93.
94.
95.
96.
The sonographic appearances in postpartum thyroiditis.   总被引:2,自引:0,他引:2  
During the postpartum period about 50% of women with circulating thyroid autoantibodies develop a transient autoimmune thyroiditis. To determine the sonographic appearances in postpartum thyroiditis (PPT), serial ultrasound (US) scans of the thyroid were performed in 135 postpartum women who were divided into three clinical groups: Group 1, 37 antibody positive subjects who developed PPT; Group 2, 28 antibody positive subjects in whom thyroid function remained normal; Group 3, 70 antibody negative controls. Thyroid hypoechogenicity was observed in 14/31 patients (45%) who were scanned between 4 and 8 weeks postpartum and who subsequently developed PPT (Group 1) compared with 4/24 patients (17%) in Group 2 (P less than 0.05) and 1/65 patients (1.5%) in Group 3 (P less than 0.001). In antibody positive patients, the positive predictive value of an abnormal scan during this period was 78%. Between 15 and 25 weeks postpartum thyroid hypoechogenicity was present in 32/37 patients (86%) in Group 1 compared with 11/28 patients (39%) in Group 2 (P less than 0.001) and 2/70 patients (3%) in Group 3 (P less than 0.001). Sonographic abnormality persisted beyond 32 weeks postpartum in 36/41 antibody positive patients (87%) who had exhibited thyroid hypoechogenicity earlier during the study and who had late scans. The characteristic US appearance in PPT is thyroid hypoechogenicity. The role of sonography in the prediction, diagnosis and follow up of patients with PPT is discussed.  相似文献   
97.
Summary Salvage radical retroperitoneal node dissection for large residual masses remaining after chemotherapy for testicular cancer was performed in 41 patients. In 10 instances it was possible to carry out a radical removal and attempt to preserve the sympathetic chain on one side. Ejaculation was preserved in 8 of these cases. Where removal of the mass was complete (33 cases) active cancer was present in 6, only one of whom developed tumor recurrence. Salvage node dissection is worthwhile, and in about 25% of cases can be performed with preservation of ejaculation.  相似文献   
98.
Sixty Sprague-Dawley rats were pair-fed one of three nutritionally identical diets. One diet contained “low-fiber” (3.8% crude fiber); the others contained “high fiber” (28.7% crude fiber) composed of either cellulose or lignin. Although both “high fiber” diets had similar stool bulking effects, only the cellulose diet was associated with a reduction in 1,2-dimethylhydrazine (DMH)-induced colon neoplasms. The cellulose diet was also associated with distinct changes in the gut bacterial profile and with a lowered serum cholesterol. © 1993 Wiley-Liss, Inc.  相似文献   
99.
100.
IgA nephropathy and polycystic kidney disease   总被引:1,自引:0,他引:1  
We report a patient with polycystic kidney disease, advanced renal failure, and nephrotic-range proteinuria. Kidney biopsy revealed IgA nephropathy with lesions of focal and segmental glomerular sclerosis. This association had not been previously described and is probably coincidental. This case supports the assumption that the nephrotic-range proteinuria observed in some polycystic patients could be the consequence of another superimposed glomerular disease. This glomerulopathy can worsen the course of azotemia in these patients.  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