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   637413篇
  免费   33090篇
  国内免费   631篇
耳鼻咽喉   8392篇
儿科学   21747篇
妇产科学   16205篇
基础医学   107378篇
口腔科学   15040篇
临床医学   56215篇
内科学   115711篇
皮肤病学   14965篇
神经病学   42324篇
特种医学   24474篇
外国民族医学   85篇
外科学   95669篇
综合类   9106篇
现状与发展   2篇
一般理论   132篇
预防医学   43956篇
眼科学   15142篇
药学   48803篇
  1篇
中国医学   1416篇
肿瘤学   34371篇
  2018年   6530篇
  2017年   4827篇
  2016年   5869篇
  2015年   6477篇
  2014年   8589篇
  2013年   12701篇
  2012年   18393篇
  2011年   20251篇
  2010年   11770篇
  2009年   10561篇
  2008年   18646篇
  2007年   20625篇
  2006年   20265篇
  2005年   19721篇
  2004年   19296篇
  2003年   18559篇
  2002年   18047篇
  2001年   28859篇
  2000年   29396篇
  1999年   24355篇
  1998年   6744篇
  1997年   5800篇
  1996年   5643篇
  1995年   5237篇
  1994年   4686篇
  1992年   17908篇
  1991年   19136篇
  1990年   19221篇
  1989年   18681篇
  1988年   17067篇
  1987年   16844篇
  1986年   15783篇
  1985年   15115篇
  1984年   11195篇
  1983年   9473篇
  1982年   5059篇
  1981年   4680篇
  1979年   10640篇
  1978年   7653篇
  1977年   6194篇
  1976年   6401篇
  1975年   7734篇
  1974年   8570篇
  1973年   8288篇
  1972年   7582篇
  1971年   7234篇
  1970年   6722篇
  1969年   6208篇
  1968年   5871篇
  1967年   5229篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.

Objective

Low psoas muscle area is shown to be an indicator for worse postoperative outcome in patients undergoing vascular surgical. Additionally, it has been associated with longer durations of hospital stay in patients with cancer who undergo surgery and subsequently greater health care costs in Europe and the United States. We sought to evaluate this effect on hospital expenditure for patients undergoing vascular repair in a health care system with universal access.

Methods

Skeletal muscle mass was assessed on preoperative abdominal computed tomography scans of patients undergoing open aortic aneurysm repair in a retrospective fashion. The skeletal muscle index (SMI) was used to define low muscle mass. Health care costs were obtained for all patients and the relationship between a low SMI and higher costs was explored using linear regression and cross-sectional analysis.

Results

We included 156 patients (81.5% male) with a median age of 72 years undergoing elective surgery for infrarenal abdominal aortic aneurysm in this analysis. The median SMI for patients with low skeletal muscle mass was 53.21 cm2/kg and for patients without, 70.07 cm2/kg. Hospital duration of stay was 2 days longer in patients with low skeletal muscle mass as compared with patients with normal (14 days vs 11 days; P = .001), as was duration of intensive care stay (3 days vs 1 day; P = .01). The median overall hospital costs were €10,460 higher for patients with a low SMI as compared with patients with a normal physical constitution (€53,739 [interquartile range, €45,007-€62,471] vs €43,279 [interquartile range, €39,509-€47,049]; P = .001). After confounder adjustment, a low SMI was associated with a 14.68% cost increase in overall hospital costs, for a cost increase of €6521.

Conclusions

Low skeletal muscle mass is independently associated with higher hospital as well as intensive care costs in patients undergoing elective aortic aneurysm repair. Strategies to reduce this risk factor are warranted for these patients.  相似文献   
4.
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   
5.
Chronic transplant dysfunction is a complex dynamic pathogenic process. Clinically, a decrease in glomerular filtration rate (GFR) becomes apparent leading to chronic renal insufficiency and dialysis or death from cardiovascular events. Chronic transplant dysfunction can develop into a chronic alIograft nephropathy (CAN) as a specific entity with dynamic progression. CAN includes a collection of immunologic and non-immunologic factors, rejection, ischemia time, donor and recipient characteristics and toxicity of calcineurin inhibitors. Despite improvements in immunosuppression, the long-range prognosis of renal allografts has not improved. Whether modern immunosuppressive concepts with reduction or avoidance of calcineurin inhibitors and a therapy based on antimetabolites, such as mycophenolate or mTOR-inhibitors could lead to a prolongation of transplant survival, remains to be seen.  相似文献   
6.
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   
7.
8.
9.
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   
10.
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