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   3227篇
  免费   255篇
  国内免费   75篇
耳鼻咽喉   6篇
儿科学   89篇
妇产科学   48篇
基础医学   478篇
口腔科学   29篇
临床医学   381篇
内科学   882篇
皮肤病学   45篇
神经病学   216篇
特种医学   280篇
外国民族医学   1篇
外科学   340篇
综合类   88篇
一般理论   6篇
预防医学   233篇
眼科学   29篇
药学   186篇
中国医学   18篇
肿瘤学   202篇
  2023年   16篇
  2022年   34篇
  2021年   71篇
  2020年   35篇
  2019年   58篇
  2018年   66篇
  2017年   48篇
  2016年   42篇
  2015年   63篇
  2014年   66篇
  2013年   117篇
  2012年   176篇
  2011年   194篇
  2010年   122篇
  2009年   103篇
  2008年   128篇
  2007年   192篇
  2006年   134篇
  2005年   122篇
  2004年   132篇
  2003年   105篇
  2002年   99篇
  2001年   97篇
  2000年   102篇
  1999年   68篇
  1998年   85篇
  1997年   71篇
  1996年   89篇
  1995年   57篇
  1994年   55篇
  1993年   72篇
  1992年   60篇
  1991年   50篇
  1990年   61篇
  1989年   60篇
  1988年   72篇
  1987年   61篇
  1986年   50篇
  1985年   56篇
  1984年   31篇
  1983年   29篇
  1982年   25篇
  1981年   30篇
  1980年   29篇
  1979年   22篇
  1978年   18篇
  1977年   19篇
  1976年   14篇
  1975年   14篇
  1974年   8篇
排序方式: 共有3557条查询结果,搜索用时 15 毫秒
41.
42.
43.

Background

Endoscopic submucosal dissection (ESD) is a technically demanding procedure, and exposure of the submucosa depends on the action of gravity and submucosal injection. The aim of the study was to investigate the effectiveness of the Endolifter® as a traction device for enhancing submucosal visualization during ESD.

Methods

This was a prospective ex vivo comparative study conducted between September 2010 and March 2011 in the Prince of Wales Hospital. Consecutive ESDs were performed by four experienced endoscopists in an ex vivo ESD model with or without the Endolifter®. The Endolifter® allows simultaneous grasping, retracting and lifting of the mucosa during ESD, resulting in exposure of the submucosa. Each of the procedures were recorded and reviewed later by two independent assessors. The outcome measures included the proportion of time that the submucosa was visualized during the procedures (SM ratio), procedural times, perforation rates, amount of submucosal injections, and the difficulty of the procedure.

Results

Forty-eight gastric ESD procedures were performed on the model. The SM ratio was higher in the Endolifter® group (P = 0.007), particularly for lesions located at the antrum (P < 0.001). The time required for submucosal dissection and the total procedural time were also less in the Endolifter® group. The endoscopists rated the ESD procedures in the Endolifter® group as less difficult (P = 0.033).

Conclusions

The Endolifter® improved submucosal visualization during gastric ESD and reduces the difficulty of performing the procedures. The device may improve the ease of performing ESD in low-volume centers or large mucosal lesions.  相似文献   
44.
BackgroundHistorical studies of lymphatic drainage of the breast have suggested that the lymphatic drainage of the breast was to lymph nodes lying in the antero-pectoral group of nodes in the axilla just lateral to the pectoral muscles. The purpose of this study was to confirm this is not correct.MethodsThe hybrid imaging method of SPECT/CT allows the exact anatomical position of the sentinel lymph node (SLN) in the axilla to be documented during pre-operative lymphoscintigraphy (LS) in patients with breast cancer. We have done this in a series of 741 patients. The Level I axillary nodes were defined as anterior, mid or posterior. This was related to the anatomical location of the primary cancer in the breast.ResultsA SLN was found in the axilla in 97.8% of our patients. Just under 50% of SLNs located in the axilla were not in the anterior group and lay in the mid or posterior group of Level I axillary nodes. There was a SLN in a single node field in 460 patients (63%), two node fields in 261(36%), three node fields in 6 and four node fields in 1 patient.ConclusionAxillary lymphatic drainage from the breast is not exclusively to the anterior (or antero-pectoral) group of Level I nodes.SynopsisSPECT/CT lymphoscintigraphy shows that the breast does not always drain to the anterior group of Level I lymph nodes in the axilla but may drain to the mid axilla and/or posterior group in about 50% of patients with breast cancer regardless of the location of the cancer in the breast. These data redefine lymph drainage from the breast to axillary lymph nodes.  相似文献   
45.
Provision of adequate nutrition is a cornerstone of the management of infants and very young children with chronic kidney disease (CKD). Very young children with CKD frequently have poor spontaneous nutritional intake. Because growth depends strongly on nutrition during early childhood, growth in very young children with CKD is often suboptimal. In this review we will consider the mechanisms and manifestations of inadequate nutritional status in very young children with CKD, mechanisms mediating inadequate nutritional intake, and the optimal nutritional management of this special population. In addition, we suggest an approach to the assessment of nutritional status, including the use of body mass index in infants. Five major nutritional components are considered: energy, macronutrients, fluids and electrolytes, micronutrients, and calcium/phosphorus/vitamin D. The use of adjunctive therapies, including appetite stimulants, treatment of gastroesophageal reflux and gastric dysmotility, enhanced dialytic clearance, and growth hormone, is also briefly discussed.  相似文献   
46.

Purpose

This article is a narrative review regarding the usage and effectiveness of introducers or catheters to facilitate tracheal intubation through a supraglottic airway (SGA) as an alternative intubation technique in normal and difficult airway management.

Sources

Relevant articles were obtained through Medline (1948-July 2011). The articles were subsequently cross-referenced for additional literature, and only articles published in English were included.

Principal findings

In this review, we consider 32 reports using the LMA Classic?, LMA Unique?, LMA ProSeal?, LMA Supreme?, AuraOnce?, and i-gel? as SGA conduits for intubation. In 13 articles, the use of an Aintree Intubation Catheter was described as an intubation introducer and resulted in high success rates in both elective and emergent situations. Eight studies used a guidewire exchange catheter technique. Although blind intubation using a guidewire resulted in a high failure rate, these studies found that using a bronchoscope improved successful intubation. Ten studies showed that insertion of a gum elastic bougie with a bronchoscope as an intubation introducer has high success rates compared with blind bougie insertion. One article described the use of a small endotracheal tube as an intermediary for tracheal intubation.

Conclusions

In failed intubation scenarios, supraglottic airways, such as the LMA Classic? or LMA ProSeal? can serve as a conduit for tracheal intubation. A number of techniques using introducers or catheters can facilitate the insertion of an adequately sized endotracheal tube, particularly guided by a bronchoscope. Usage of introducers or catheters through a supraglottic airway may be a useful alternative intubation technique in difficult airway management.  相似文献   
47.
前列腺增生症术后性功能障碍   总被引:1,自引:0,他引:1  
前列腺增生症术后性功能障碍孔良王伟明叶敏我们调查了247例因良性前列腺增生症(BPH)行耻骨上前列腺摘除术(SPP)或经尿道前列腺切除术(TURP)患者术后性功能障碍的发生率,并探讨其可能的原因。病人与方法:本组247例中SPP114例,TURP13...  相似文献   
48.
Glucocorticoids exert both anabolic and catabolic effects on bone. Previously, we reported that endogenous glucocorticoids control mesenchymal lineage commitment and osteoblastogenesis through regulation of Wnt signaling in osteoblasts. Here, we investigated the effects of glucocorticoids on Wnt expression in mature osteoblasts. Mature osteoblasts and their immature progenitors were separately isolated from Col2.3-GFP transgenic mice in which mature osteoblasts are identifiable through GFP expression. mRNA levels of Wnt2, Wnt2b, Wnt4, Wnt5a, Wnt10b, and Wnt11 were 4- to 12-fold higher in osteoblasts compared to their progenitors (P < 0.05). Expression of Wnt7b and Wnt10b in osteoblasts was modulated by corticosterone (CS), in a biphasic fashion with 3- to 3.5-fold upregulation at 10 nM CS (P < 0.01) and 50% downregulation at 100 nM CS (P < 0.05). CS 100 nM also increased expression of the Wnt inhibitors sFRP-1 and DKK-1 two- to threefold (P < 0.05). We conclude that the contrasting anabolic and catabolic effects of glucocorticoids on bone are, at least in part, mediated through the regulation of Wnt expression and its inhibitors in mature osteoblasts.  相似文献   
49.
The authors studied the impact of edge enhancement and gray scale polarity reversal on the detection of subtle lung cancers. Three experienced readers reviewed 46 biopsy-proved subtle lung cancers and 46 normal controls on chest radiographs that had been digitized into a 1,024 X 1,536-pixel matrix 8 bits deep. Receiver-operating characteristics (ROC) analysis of 1,656 pooled observations indicated that performance was best with the unmodified images (ROC area = 0.83), degraded by moderate enhancement of medium frequencies (ROC area = 0.80), and markedly impaired by severe enhancement of low frequencies (ROC area = 0.69). Gray scale polarity reversal further degraded performance (unenhanced ROC area = 0.74; moderately enhanced ROC area = 0.76; severely enhanced ROC area = 0.76). The authors conclude that edge enhancement and gray scale polarity reversal can impair the detectability of subtle lung cancers on digitized radiographs of medium resolution.  相似文献   
50.
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