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   861501篇
  免费   71530篇
  国内免费   1838篇
耳鼻咽喉   12799篇
儿科学   24624篇
妇产科学   25106篇
基础医学   124229篇
口腔科学   25507篇
临床医学   75331篇
内科学   164621篇
皮肤病学   17008篇
神经病学   70120篇
特种医学   35213篇
外国民族医学   171篇
外科学   136264篇
综合类   24604篇
现状与发展   2篇
一般理论   263篇
预防医学   66869篇
眼科学   20537篇
药学   64700篇
中国医学   1595篇
肿瘤学   45306篇
  2018年   7337篇
  2015年   7727篇
  2014年   11113篇
  2013年   16781篇
  2012年   22717篇
  2011年   23843篇
  2010年   13870篇
  2009年   13062篇
  2008年   22570篇
  2007年   24626篇
  2006年   24505篇
  2005年   24156篇
  2004年   23724篇
  2003年   22842篇
  2002年   21941篇
  2001年   35838篇
  2000年   36481篇
  1999年   30905篇
  1998年   9227篇
  1997年   8553篇
  1996年   8479篇
  1995年   8015篇
  1994年   7728篇
  1992年   26682篇
  1991年   26115篇
  1990年   25625篇
  1989年   24698篇
  1988年   23232篇
  1987年   22890篇
  1986年   21746篇
  1985年   21106篇
  1984年   16398篇
  1983年   14006篇
  1982年   8859篇
  1981年   8204篇
  1980年   7672篇
  1979年   16742篇
  1978年   12115篇
  1977年   10182篇
  1976年   9329篇
  1975年   10150篇
  1974年   12643篇
  1973年   12137篇
  1972年   11543篇
  1971年   10692篇
  1970年   10227篇
  1969年   9917篇
  1968年   8908篇
  1967年   8233篇
  1966年   7654篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Background Free tissue transfer using microvascular surgery has become a safe a reliable means to repair soft tissue and/or bony defects of the head and neck. Operative success reaches 98%, however the incidence of significant post‐operative complication is also relatively high (32%). One common and often severe complication is haematoma formation at either donor or recipient sites. The incidence of recipient site haematoma is reported at 6%, however the causes and outcomes of haematomas have not been well investigated. A retrospective historical analysis of both donor and recipient site wound haematoma was performed to identify causative factors and the effect on patient outcome. Methodology A five year review was conducted for microvascular free tissue transfer to defects in the head and neck at The Royal Melbourne Hospital, for the period from February 2001 until February 2006. The medical records of these 150 patients were reviewed for donor and recipient site wound haematoma and outcomes. Results Significant factors for the development of post‐operative haematomas included lood pressure control during the first post‐operative, correlating with the likelihood of developing either a donor or recipient site haematoma (p value < 0.001), drain‐tube outputs (both high and low), smoking and the use of pre‐operative NSAIDs. Conclusion There are significant reversible factors that contribute to the development of post‐operative haematomas in head and neck surgery. Close monitoring of patient blood pressure by theatre and recovery nursing staff, close monitoring of drain outputs, and pre‐operative counselling on the use of NSAIDs and smoking may all be useful in the prevention of haematoma formation.  相似文献   
992.
993.
994.
Reduced bone mineral density (BMD) was sporadically reported in patients with Marfan syndrome. This may or may not place the Marfan patient at increased risk for bone fracture. In comparing the BMDs of our patients with those reported in the literature, it seemed that agreement between values, and hence the degree of osteoporosis or osteopenia reported, was dependent on the instrumentation used. The objective of this study was to statistically assess this impression. Bone mineral density measurements from our previously published study of 30 adults with Marfan syndrome performed on a Lunar DPXL machine were compared with studies published between 1993–2000 measured using either Lunar or Hologic bone densitometry instruments. The differences of our measurements compared with those made on other Lunar machines were not statistically significant, but did differ significantly with published results from Hologic machines (P < 0.001). Before progress can be made in the assessment of BMD and fracture risk in Marfan patients and in the evidence-based orthopedic management of these patients, standardization of instrumental bone density determinations will be required along with considerations of height, obesity, age, and sex.  相似文献   
995.
In contrast to vasculogenesis, angiogenesis is defined as the formation of new vessels from preexisting ones. Physiologically, this multistep process occurs in adults during the reproductive cycle and during pregnancy, pathophysiologically it can be found in wound healing, inflammation and carcinogenesis. The underlying mechanisms are vasodilatation and increasing permeability, destabilization of vessel walls and degradation of extracellular matrix, followed by the proliferation and migration of endothelial cells. Migrated endothelial cells form vascular tubes at sites of ischemia and these tubes are finally stabilized by pericytes and smooth muscle cells. This process is controlled by a complex interaction of angiogenic and angiostatic factors. In contrast to carcinogenesis, the role of angiogenesis for the pathogenesis and therapy of rheumatic diseases is less understood. Two examples for pathologically disturbed angiogenesis, rheumatoid arthritis and systemic sclerosis, are discussed in this review with respect to therapeutic options.  相似文献   
996.
Interleukin (IL)-13 plays a central role in asthma pathogenesis by binding to the IL-13 receptor, which is a heterodimer composed of the IL-13 receptor alpha1 subunit (IL-13Ralpha1) and IL-4Ralpha. The genetic diversity at the IL-13Ralpha1 gene (IL13RA1) locus on chromosome Xq24 was characterised and the association of identified polymorphisms with asthma and atopy phenotypes examined. The promoter and coding region of IL13RA1 were screened for common genetic variants, and polymorphisms found were genotyped in a large cohort of 341 asthmatic Caucasian families (each containing at least two asthmatic siblings) and 182 nonasthmatic control subjects. Genetic association was determined using case-control and transmission disequilibrium test analyses. Two common polymorphisms were identified, a newly found thymidine (T) to guanine (G) transition of nucleotide -281 (-281T>G) single nucleotide polymorphism in the IL13RA1 promoter and the previously described 1365A>G variant in the IL13RA1 proximal 3' untranslated region. No significant association of either -281T>G or 1365A>G with risk of asthma or atopy phenotypes was found, apart from a suggestive association between the IL13RA1 -281T/1365A haplotype and raised total serum immunoglobulin E levels in adult female asthmatics. These findings indicate that the interleukin-13 receptor alpha1 subunit gene -281T>G and 1365A>G polymorphisms do not contribute to asthma susceptibility or severity, although the interleukin-13 receptor alpha1 subunit gene locus might be involved in the control of immunoglobulin E production.  相似文献   
997.
998.
999.
1000.
Zusammenfassung Die Fasern des primären optischen Systems lassen sich bei allen Wirbeltieren in zwei Gruppen einteilen, welche der vorderen und hinteren Retinahälfte entstammen und sich bis zu ihren Endstationen morphologisch nachweisen lassen. Es wurde versucht, dieses anatomische Verhalten mit einigen physiologischen Eigenschaften des Auges in Verbindung zu bringen.Mit 17 zum Teil farbigen Textabbildungen.  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