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   534082篇
  免费   27866篇
  国内免费   512篇
耳鼻咽喉   6730篇
儿科学   17036篇
妇产科学   12607篇
基础医学   93111篇
口腔科学   12769篇
临床医学   48812篇
内科学   96293篇
皮肤病学   11936篇
神经病学   34297篇
特种医学   19850篇
外国民族医学   53篇
外科学   78551篇
综合类   7623篇
现状与发展   2篇
一般理论   107篇
预防医学   39020篇
眼科学   12017篇
药学   41695篇
  1篇
中国医学   1148篇
肿瘤学   28802篇
  2021年   4053篇
  2019年   4032篇
  2018年   5899篇
  2017年   4247篇
  2016年   4979篇
  2015年   5537篇
  2014年   7335篇
  2013年   10716篇
  2012年   15894篇
  2011年   17786篇
  2010年   10177篇
  2009年   8960篇
  2008年   15949篇
  2007年   17702篇
  2006年   17133篇
  2005年   16451篇
  2004年   16019篇
  2003年   15373篇
  2002年   14885篇
  2001年   22493篇
  2000年   23038篇
  1999年   18968篇
  1998年   5245篇
  1997年   4373篇
  1996年   4419篇
  1995年   4132篇
  1992年   14442篇
  1991年   15840篇
  1990年   15959篇
  1989年   15635篇
  1988年   14320篇
  1987年   14203篇
  1986年   13176篇
  1985年   12695篇
  1984年   9400篇
  1983年   8007篇
  1982年   4181篇
  1979年   8941篇
  1978年   6385篇
  1977年   5151篇
  1976年   5508篇
  1975年   6616篇
  1974年   7422篇
  1973年   7160篇
  1972年   6597篇
  1971年   6314篇
  1970年   5888篇
  1969年   5470篇
  1968年   5164篇
  1967年   4625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