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   530696篇
  免费   27719篇
  国内免费   497篇
耳鼻咽喉   6686篇
儿科学   16933篇
妇产科学   12551篇
基础医学   92681篇
口腔科学   12354篇
临床医学   48578篇
内科学   95679篇
皮肤病学   11897篇
神经病学   34055篇
特种医学   19814篇
外国民族医学   53篇
外科学   78142篇
综合类   7615篇
现状与发展   2篇
一般理论   107篇
预防医学   38574篇
眼科学   11939篇
药学   41447篇
  1篇
中国医学   1127篇
肿瘤学   28677篇
  2021年   3907篇
  2018年   5754篇
  2017年   4140篇
  2016年   4882篇
  2015年   5383篇
  2014年   7131篇
  2013年   10514篇
  2012年   15611篇
  2011年   17434篇
  2010年   9992篇
  2009年   8841篇
  2008年   15749篇
  2007年   17475篇
  2006年   16971篇
  2005年   16287篇
  2004年   15897篇
  2003年   15279篇
  2002年   14791篇
  2001年   22453篇
  2000年   22999篇
  1999年   18942篇
  1998年   5250篇
  1997年   4369篇
  1996年   4408篇
  1995年   4135篇
  1992年   14435篇
  1991年   15844篇
  1990年   15969篇
  1989年   15643篇
  1988年   14325篇
  1987年   14211篇
  1986年   13176篇
  1985年   12694篇
  1984年   9399篇
  1983年   8003篇
  1982年   4180篇
  1979年   8941篇
  1978年   6386篇
  1977年   5152篇
  1976年   5507篇
  1975年   6616篇
  1974年   7426篇
  1973年   7164篇
  1972年   6601篇
  1971年   6311篇
  1970年   5888篇
  1969年   5468篇
  1968年   5163篇
  1967年   4621篇
  1966年   3963篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
Abstract

This study was undertaken to compare the concentrations of pro- and anti-angiogenic growth factors, nitric oxide (NO) stable metabolites in maternal serum and embryonic left ventricular (LV) isovolumic relaxation time (IRT, ms) during the first trimester in two groups of women: with pregnancy conceived by assisted reproductive technologies (ART, n?=?39) and normally conceived (control group, n?=?68) pregnancy. The concentration of vasoconstrictor endothelin 1 was 45.5 times more in ART than in control group. On the contrary, the concentrations of NO stable metabolites in ART were 1.9 times less than in control women. The assessment of angiogenic suppressors in ART women demonstrates the decrease in s-endoglin concentration was 1.6 times and in soluble receptor to vascular endothelial growth factor concentration was 2.0 times in comparison with control group. There was a significant increase in LV IRT in ART embryos in comparison to control ones. These data suggest significant changes in pro- anti-angiogenic factors balance and increase in vascular impedance in ART-conceived embryos.  相似文献   
4.
We report the case of a littoral‐cell angioma of the spleen, a recently described benign vascular tumour, whose imaging and pathological characteristics have been discussed only by a few authors. The diagnosis was made after elective splenectomy. The CT images, scintigraphy and histological specimens are presented, and differential diagnoses discussed.  相似文献   
5.
6.
7.
Medullary thyroid carcinoma (MTC) is a rare form of thyroid cancer representing about 10% of all thyroid malignancies. It occurs mostly as a sporadic tumor or in association with autosomal dominant inherited cancer syndromes--multiple endocrine neoplasia (MEN) types 2A and 2B and familial MTC. Germline mutations in exons 8, 10, 11, 13, 14, 15 and 16 of the RET proto-oncogene are found in most of the familial cases. There are only a few published data reporting multiple germline mutations in the RET proto-oncogene. We have detected double germline mutations in 2 different exons on the same RET allele in two MEN 2 families. In the MEN 2A family, double germline mutation in exons 10 (Cys620Phe) and 13 (Tyr791Phe) was detected. In the MEN 2B family, beside the classical germline mutation in exon 16 (Met918Thr) a second germline mutation in exon 13 (Tyr791Phe) was found. This study revealed that MEN 2 syndromes can also be caused by double germline mutations in the RET proto-oncogene and these families can be added to small worldwide cohort of families with multiple germline mutations.  相似文献   
8.
9.
The clinical outcome and appropriate management for patients showing 'borderline changes' on allograft biopsy after renal transplantation is still controversial. In an attempt to identify predictive factors of clinical outcome of patients with such lesions, we reviewed the clinical course of 91 patients with borderline changes. Multivariate analysis revealed significant and independent effects of histological stage (i + t < or = or > 2) and time to borderline changes (< or = or > 3 months after transplant) on serum creatinine levels at 1 year from borderline changes episodes (respectively, p = 0.04 and p = 0.02) and only a significant effect of time to borderline changes on serum creatinine levels at 2 years (p = 0.005). Renal function at 1 year and 2 years as 5- and 8-year graft survival were not significantly different in the group of patients treated with antirejection therapy (T group, n = 49) compared with the untreated group (UT group, n = 42). This study strongly suggests that borderline changes with histological score (i + t) > 2 and late episodes of borderline changes should be considered to be of poor prognosis.  相似文献   
10.
Endoscopic clips have been used mainly for control of gastrointestinal (GI) bleeding and occasionally for closure of GI perforations. However, closure of spontaneous esophageal perforation (Boerhaave's syndrome) by clipping has not been reported. We described successful non-surgical closure of spontaneous esophageal perforation by endoscopic clipping in a patient with bilateral pyopneumothorax and septicemia.  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