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   254865篇
  免费   54673篇
  国内免费   3409篇
耳鼻咽喉   3783篇
儿科学   7268篇
妇产科学   4406篇
基础医学   41454篇
口腔科学   8360篇
临床医学   29932篇
内科学   55317篇
皮肤病学   11696篇
神经病学   25748篇
特种医学   11348篇
外国民族医学   7篇
外科学   36957篇
综合类   7292篇
现状与发展   9篇
一般理论   103篇
预防医学   15485篇
眼科学   6186篇
药学   21896篇
  18篇
中国医学   4667篇
肿瘤学   21015篇
  2023年   1307篇
  2022年   3900篇
  2021年   7452篇
  2020年   8136篇
  2019年   14472篇
  2018年   14746篇
  2017年   14725篇
  2016年   16238篇
  2015年   17966篇
  2014年   19375篇
  2013年   21190篇
  2012年   18476篇
  2011年   18189篇
  2010年   16937篇
  2009年   12107篇
  2008年   12492篇
  2007年   11248篇
  2006年   10502篇
  2005年   9872篇
  2004年   8629篇
  2003年   7891篇
  2002年   7000篇
  2001年   5932篇
  2000年   5329篇
  1999年   4034篇
  1998年   1663篇
  1997年   1326篇
  1996年   1206篇
  1995年   1070篇
  1994年   947篇
  1993年   775篇
  1992年   1711篇
  1991年   1705篇
  1990年   1479篇
  1989年   1336篇
  1988年   1232篇
  1987年   1093篇
  1986年   1072篇
  1985年   921篇
  1984年   666篇
  1983年   572篇
  1982年   412篇
  1981年   398篇
  1980年   352篇
  1979年   535篇
  1978年   412篇
  1977年   392篇
  1976年   346篇
  1974年   363篇
  1973年   332篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
992.
993.
The goal of endoscopic mucosal resection (EMR) is to allow the endoscopist to obtain tissue or resect lesions not previously amenable to standard biopsy or excisional techniques and to remove malignant lesions without open surgery. In this article, we describe the results of conventional EMR and EMR using an insulation‐tipped (IT) electrosurgical knife (submucosal dissection method) for large colorectal mucosal neoplasms and discuss the problems and future prospects of these procedures. At present, conventional EMR is much more feasible than EMR using IT‐knife from the perspectives of time, money, complication, and organ preservation. However, larger lesions tend to be resected in a piecemeal fashion; and it is difficult to confirm whether EMR has been complete. For accurate histopathological assessment of the resected specimen en bloc EMR is desirable although further experience is needed to establish its safety and efficacy. Further improvements of in EMR with special knife techniques are required to simply and safely remove large colorectal neoplasms.  相似文献   
994.
995.
Background/aims  Surgical resection of choledochal cysts (CC) has become standard treatment. However, surgery is not universally recommended in early infancy and/or asymptomatic patients. In order to investigate the optimal timing of CC excision, we analyzed clinicopathological data and surgical results from different age groups. Material and methods  This retrospective review included 107 patients (77 females, 30 males) who underwent CC resection at the National Taiwan University Hospital between January 1988 and December 2005. Patient demographic, clinical, and surgical data were collected and analyzed. Results  The patients were divided into three groups according to age at the time of surgery: <1 year old (group I, n = 26), 1−16 years old (group II, n = 48), and >16 years old (group III, n = 33). About two thirds of the patients in group I had jaundice, while abdominal pain related to inflammation was the commonest symptom in groups II and III. Group I suffered significantly fewer surgical complications and less severe liver fibrosis than groups II or III. Conclusion  CC surgery in infancy and in asymptomatic patients is safe and may prevent the complications of this condition. The results support a recommendation for early excision.  相似文献   
996.
Aims and Methods: The pulmonary and vascular effects of endothelin‐1 receptor activation were studied in isolated perfused and ventilated lung preparations from rat. The responses to endothelin‐1 (ET‐1) and the endothelin B (ETB) receptor agonist sarafotoxin 6c (S6c) were characterized using the endothelin A (ETA)‐receptor antagonist FR 139317, the ETB‐receptor antagonist BQ 788 and the combined ETA/ETB‐receptor antagonist Bosentan. The respiratory parameter airway conductance (Gaw) and the vascular parameter perfusion flow were analysed simultaneously. Results: Concentration–response curves for ET‐1 administered intra‐arterially revealed that its most potent effect was on the vascular side while S6c had a more potent effect on airway conductance. ET‐1, given as a bolus dose intra‐arterially (100 μL of 0.2 nm ), induced a strong‐ and long‐lasting contraction of the vasculature while only a less pronounced contraction was seen in the airways. Neither of the antagonists had a significant effect per se on Gaw or perfusion flow. FR 139317 reduced the effect of ET‐1 on perfusion flow by about 50%, while airway conductance was augmented. BQ 788 enhanced the decrease in perfusion flow by ET‐1 while Gaw was not influenced. The combined ETA/ETB antagonist Bosentan powerfully prevented the ET‐1‐induced decrease in Gaw but did not alter its reduction in perfusion flow. Conclusions: The potent effect of ET‐1 on the vascular side of the lung is mediated mainly through ETA receptors, whereas both ETA and ETB receptors are involved in Gaw in the rat lung.  相似文献   
997.
目的探讨第一、二鳃弓综合征面部不对称畸形的整形外科矫治方法。方法根据第一、二鳃弓综合征患者临床及X线所示面部双侧不对称情况,采用健侧下颌骨外板去除、颧骨截骨降低;患侧下颌体、颧骨应用健侧下颌骨外板贴附植骨或高密度多孔聚乙烯(Medpor)假体置入等术式,配合颏部水平截骨颏成形术,以缩小面部双侧宽度的差异,矫治颜面不对称畸形。结果共矫治23例,经6个月至3年的术后随访观察,双侧面部宽度差异明显缩小,正面观面部不对称明显改善。结论第一、二鳃弓综合征面部骨骼发育畸形是三维方向的,双侧面骨宽度的差异,是造成正面观面部不对称的重要因素,根据受术者的具体情况,采用以上术式的组合,扩充患侧或同时缩窄健侧骨骼,进行面部骨性支架重建,可以取得良好的矫治效果。  相似文献   
998.
Non-selective inhibition of monoamine oxidase (MAO) enzymes (ie, isoforms A and B) in the brain are associated with clinically significant antidepressant effects. In the US, the selegiline transdermal system (STS; EMSAM) is the first antidepressant transdermal delivery system to receive Food and Drug Administration (FDA) approved labeling for the treatment of major depressive disorder (MDD). Currently, the use of orally administered MAO inhibitor antidepressants (eg, phenelzine, tranylcypromine) is limited by the risk of tyramine-provoked events (eg, acute hypertension and headache, also known as the “cheese reaction”) when combined with dietary tyramine. The selegiline transdermal system is the only MAOI available in the US for the treatment of MDD that does not require dietary restriction at the clinically effective dose of 6 mg/24 hours. Delivery of selegiline transdermally (EMSAM®) bypasses hepatic first pass metabolism, thereby avoiding significant inhibition of gastrointestinal and hepatic MAO-A activity (ie, reduced risk of tyramine-provoked events) while still providing sufficient levels of selegiline in the brain to produce an antidepressant effect. At dosages of 6–12 mg/24 hours, EMSAM has been shown to improve symptoms of depression, have good tolerability, and have high rates of medication adherence. However, at higher doses of EMSAM (ie, 9 mg/24 hours or more), dietary restriction of tyramine intake is recommended. The introduction of EMSAM overcomes many of the safety concerns affiliated with the conventional oral MAO inhibitors and EMSAM may be considered another strategy for the treatment of MDD, especially in patients who cannot tolerate oral antidepressants, are poorly adherent, who present with atypical depressive symptoms, or have failed other antidepressants.  相似文献   
999.
1000.
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