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   556690篇
  免费   27318篇
  国内免费   498篇
耳鼻咽喉   6916篇
儿科学   17589篇
妇产科学   13074篇
基础医学   95850篇
口腔科学   12954篇
临床医学   51348篇
内科学   100411篇
皮肤病学   12211篇
神经病学   36358篇
特种医学   20498篇
外国民族医学   53篇
外科学   81157篇
综合类   8154篇
现状与发展   2篇
一般理论   122篇
预防医学   41021篇
眼科学   12390篇
药学   43414篇
  13篇
中国医学   1155篇
肿瘤学   29816篇
  2021年   4307篇
  2019年   4328篇
  2018年   6137篇
  2017年   4460篇
  2016年   5170篇
  2015年   5717篇
  2014年   7613篇
  2013年   11232篇
  2012年   16642篇
  2011年   18479篇
  2010年   10596篇
  2009年   9348篇
  2008年   16654篇
  2007年   18563篇
  2006年   17977篇
  2005年   17341篇
  2004年   16830篇
  2003年   16264篇
  2002年   15687篇
  2001年   23073篇
  2000年   23624篇
  1999年   19475篇
  1998年   5500篇
  1997年   4582篇
  1996年   4598篇
  1995年   4359篇
  1992年   14900篇
  1991年   16277篇
  1990年   16361篇
  1989年   16053篇
  1988年   14698篇
  1987年   14588篇
  1986年   13508篇
  1985年   13092篇
  1984年   9747篇
  1983年   8284篇
  1982年   4445篇
  1979年   9250篇
  1978年   6655篇
  1977年   5349篇
  1976年   5731篇
  1975年   6812篇
  1974年   7682篇
  1973年   7430篇
  1972年   6816篇
  1971年   6508篇
  1970年   6027篇
  1969年   5631篇
  1968年   5285篇
  1967年   4741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