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   5363篇
  免费   231篇
  国内免费   44篇
耳鼻咽喉   38篇
儿科学   60篇
妇产科学   68篇
基础医学   669篇
口腔科学   93篇
临床医学   328篇
内科学   1375篇
皮肤病学   36篇
神经病学   409篇
特种医学   155篇
外科学   954篇
综合类   14篇
预防医学   98篇
眼科学   203篇
药学   339篇
中国医学   15篇
肿瘤学   784篇
  2024年   7篇
  2023年   46篇
  2022年   88篇
  2021年   164篇
  2020年   89篇
  2019年   113篇
  2018年   126篇
  2017年   95篇
  2016年   113篇
  2015年   134篇
  2014年   145篇
  2013年   197篇
  2012年   317篇
  2011年   368篇
  2010年   212篇
  2009年   150篇
  2008年   341篇
  2007年   323篇
  2006年   333篇
  2005年   373篇
  2004年   331篇
  2003年   327篇
  2002年   316篇
  2001年   59篇
  2000年   50篇
  1999年   75篇
  1998年   76篇
  1997年   68篇
  1996年   73篇
  1995年   68篇
  1994年   63篇
  1993年   42篇
  1992年   41篇
  1991年   28篇
  1990年   36篇
  1989年   21篇
  1988年   27篇
  1987年   26篇
  1986年   16篇
  1985年   19篇
  1984年   16篇
  1983年   18篇
  1982年   8篇
  1981年   21篇
  1980年   15篇
  1979年   7篇
  1977年   11篇
  1972年   6篇
  1969年   8篇
  1966年   6篇
排序方式: 共有5638条查询结果,搜索用时 15 毫秒
961.
Human herpesvirus 6 (HHV-6) has been reported to be involved in bone marrow failure after bone marrow transplantation (BMT). To elucidate the role of HHV-6 in the marrow failure, we examined the comparative effect of two variants of HHV-6 (HHV-6A and HHV-6B) and human herpesvirus 7 (HHV-7) on in vitro colony formation of hematopoietic progenitor cells in methylcellulose semi-solid media. Progenitor cells prepared from cord blood mononuclear cells (CBMNCs) were infected with one of these viruses at various multiplicity of infection (MOI), and were subjected to methylcellulose colony assay. Formation of both granulocyte/macrophage (CFU-GM) and erythroid (BFU-E) colonies was MOI-dependently suppressed after infection with the Z29 strain of HHV-6B. Although HHV-6A suppressed the formation of BFU-E colonies as efficiently as HHV-6B, the former did not exhibit significant suppressive effect on the formation of CFU-GM colonies at an MOI 1. HHV-7 had no effect on hematopoietic colony formation at all. Based on frequent positivity of viral DNA in single colonies obtained from HHV-6-infected progenitor cells by polymerase chain reaction and in situ hybridization, direct effects of HHV-6 on the hematopoietic progenitor cells are suggested as the cause of the suppression rather than indirect effects via accessory cells of the bone marrow. J. Med. Virol. 52:406–412, 1997. © 1997 Wiley-Liss, Inc.  相似文献   
962.
Total arch replacement using the frozen elephant trunk procedure is performed for true lumen expansion of the descending aorta in patients with type A acute aortic dissection. However, the remodelling effect of the frozen elephant trunk on the dissected descending aorta is unclear. We aimed to evaluate the effect of the frozen elephant trunk on postoperative descending aortic remodelling after surgery. Between December 2012 and January 2020, we retrospectively investigated 24 patients who underwent total arch replacement using the frozen elephant trunk for type A acute aortic dissection. Remodelling of the descending aorta was evaluated using computed tomography. The aortic remodelling effect, based on aortic true lumen ratio, was determined for (i) DeBakey type (type I versus type III retrograde); (ii) thoracic endovascular aneurysm repair reintervention status (reintervention versus no reintervention); and (iii) stent length of the frozen elephant trunk (60 vs 90 mm). Postoperative true lumen ratio significantly increased in the type I dissection group. The true lumen ratio in the no-reintervention group, which had many patients with the type I dissection, significantly increased after the frozen elephant trunk. Aortic remodelling due to the frozen elephant trunk can be expected after type I acute aortic dissections.  相似文献   
963.
Prolonged tracheotomy and endotracheal intubation often induce symptoms of airway obstruction and delay decannulation and extubation. Bronchoscopic examination of patients undergoing these treatments usually shows the presence of exuberant (pseudopapillary or nodular) granulation tissue occupying the airway lumen. An immunohistochemical analysis was undertaken of vascular endothelial growth factor (VEGF) expression in exuberant tracheal granulation tissue (n=17) obtained from children treated with prolonged tracheotomy or endotracheal intubation. Increased levels of VEGF protein and mRNA were expressed mainly by tracheal epithelial cells that migrated to cover the granulation tissue and partly by pericapillary macrophages in this tissue, whereas normal tracheal epithelium did not express VEGF. The VEGF expression level correlated significantly with the severity of the exuberant granulation tissue response (p=0·0018). As VEGF induces angiogenesis and vascular permeability, characteristics of granulation tissue, and plays a pivotal role in granulation tissue development, enhanced VEGF expression may be involved in the development of exuberant tracheal granulation tissue. Copyright © 1999 John Wiley & Sons, Ltd  相似文献   
964.

Study Objective

To evaluate a new magnetic resonance imaging (MRI) grading system for preoperative differentiation between benign and variant-type uterine leiomyomas including smooth muscle tumors of uncertain malignant potential (STUMPs).

Design

Retrospective analysis (Canadian Task Force classification III).

Setting

Teaching hospital (Teine Keijinkai Hospital).

Patients

Three-hundred thirteen patient medical records were retrospectively reviewed if treated for uterine myomas and diagnosed with variant type leiomyomas or STUMPs (n?=?27) or benign, typical leiomyomas (n?=?286) and treated between January 2012 and December 2014.

Intervention

Uterine myoma classifications using MRI findings according to a 5-grade system (grades I–V) based on 3 elements.

Measurements and Main Results

Uterine myoma MRI classifications were based on 3 elements: T2-weighted imaging (high or low), diffusion-weighted imaging (high or low), and apparent diffusion coefficient values (high or low; apparent diffusion coefficient?<?1.5?×?10?3 mm2/sec was considered low). Grades I to II were designated as typical or benign leiomyomas, grade III as degenerated leiomyomas, and grades IV to V as variant type leiomyomas or STUMPs. Accuracy levels were 98.9%, 100%, 94.3%, 58.8%, and 41.9% for grades I through V lesions, respectively. The grades were divided into 2 groups to discriminate benign leiomyomas and STUMPs (grades I–III were considered negative and grades IV–V positive). Grades IV to V scored 85.2% for sensitivity, 91.3% for specificity, 47.9% positive predictive value, 98.5% negative predictive value, a 9.745 positive likelihood ratio, and a .162 negative likelihood ratio.

Conclusion

This novel MRI grading system for uterine myomas may be beneficial in differentiating benign leiomyomas from STUMPs or variant type leiomyomas and could be a future effective presurgical assessment tool.  相似文献   
965.
966.
967.
A 69-year-old man with advanced esophageal cancer and 2 early gastric cancers received chemoradiotherapy and was scheduled to undergo subtotal esophagectomy after gastric endoscopic submucosal dissection(ESD). However, left lower esophageal perforation induced by vomiting suddenly occurred, and he urgently underwent esophago-proximal gastrectomy and gastrostomy without reconstruction. The resected specimen showed a complete response of pretreatment for the esophageal cancer and radical resection of one gastric cancer. Radical resection of the other gastric lesion was necessary before reconstruction. The fistula of gastrostoma was gradually dilated from 6.7 to 9.3 mm in order to pass the endoscope. At nine months after emergent operation, gastric ESD was performed via only the gastrostoma. A hemoclip with thread was attached to the specimen, and the thread was pulled out of the gastrostoma. The specimen was able to be removed en bloc, resulting in radical resection. Gastric tube reconstruction through the posterior sternal route was performed at six months after the ESD. He has not developed recurrence of the esophageal or gastric cancer in the two years since the emergent operation.  相似文献   
968.
We report a case of vimentin-positive early gastric adenocarcinoma arising in a hyperplastic polyp (HP). A 72-year-old Japanese man was admitted for the detailed examination of a gastric polyp. He had a subtotal gastrectomy due to acute abdomen 12 years ago. Upper endoscopy revealed a pedunculated polyp measuring approximately 2 cm on the greater curvature of upper body of the remnant stomach. Magnifying endoscopy revealed that the microsurface pattern was irregular and partially absent accompanied with irregular microvessels at the upper end of the polyp. We speculated that the lesion was an adenocarcinoma arising in the HP. Endoscopic submucosal dissection (ESD) was performed. Histological examination of the ESD specimen revealed that the lesion consisted of well- to poorly differentiated adenocarcinoma at the protruding lesion and foveolar hyperplastic epithelia at the base of the polyp. Immunohistochemically, most of tumor cells that comprised poorly-differentiated adenocarcinoma were positive for both cytokeratin and vimentin. Although carcinomas have occasionally been found in HPs, the histological features of the present case are considered extremely unusual. To the best of our knowledge, this is the first case of vimentin-positive early gastric carcinoma arising in a HP.  相似文献   
969.
970.
Background: Intracranial arterial stenosis (ICAS) is an important cause of ischemic stroke worldwide due to its higher risk of recurrence with medical therapy. Although some large randomized studies failed to show the superiority of surgical treatment compared with medical therapy, the results of medical therapy are not sufficient. There are patients who still benefit from surgical treatment. This retrospective analysis aimed to evaluate the long-term efficacy of surgical therapy with percutaneous transluminal angioplasty and/or stenting (PTA/PTAS) or extracranial-intracranial (EC/IC) bypass surgery for patients with ICAS. Methods: Between October 2005 and December 2016, 55 ICAS patients were treated with PTA/PTAS or EC-IC bypass surgery. Their electronic medical records were retrospectively reviewed and analyzed. The primary outcome was all adverse events beyond 30 days after a revascularization procedure. Results: We performed 21 cases (35%) of PTA, 4 cases (7%) of PTAS, and 34 cases (58%) of EC-IC bypass surgery and the median follow-up duration was 66 months (range 1-144 months). The occurrence rate of the primary outcome was 10.2% and only 1 patient (1.8%) experienced ipsilateral disabling ischemic stroke beyond 30 days. The long-term functional independent survival rate was 83.6%. Conclusions: We demonstrated a long-term favorable outcome of combined surgical intervention for ICAS patients with PTA/PTAS and EC-IC bypass surgery, and the result was better than previously reported outcomes of medical therapy. Additional multicenter studies are required to draw firm conclusions on the efficacy of reduction of recurrent stroke in patients with ICAS.  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