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   2502篇
  免费   140篇
  国内免费   55篇
耳鼻咽喉   30篇
儿科学   80篇
妇产科学   40篇
基础医学   285篇
口腔科学   240篇
临床医学   206篇
内科学   553篇
皮肤病学   47篇
神经病学   152篇
特种医学   165篇
外科学   331篇
综合类   11篇
预防医学   204篇
眼科学   12篇
药学   264篇
  1篇
中国医学   11篇
肿瘤学   65篇
  2023年   18篇
  2022年   36篇
  2021年   65篇
  2020年   62篇
  2019年   61篇
  2018年   68篇
  2017年   60篇
  2016年   74篇
  2015年   60篇
  2014年   86篇
  2013年   129篇
  2012年   159篇
  2011年   169篇
  2010年   102篇
  2009年   80篇
  2008年   125篇
  2007年   161篇
  2006年   114篇
  2005年   91篇
  2004年   78篇
  2003年   67篇
  2002年   53篇
  2001年   55篇
  2000年   56篇
  1999年   59篇
  1998年   53篇
  1997年   60篇
  1996年   62篇
  1995年   48篇
  1994年   40篇
  1993年   34篇
  1992年   18篇
  1991年   28篇
  1990年   20篇
  1989年   27篇
  1988年   30篇
  1987年   31篇
  1986年   18篇
  1985年   21篇
  1984年   10篇
  1983年   14篇
  1982年   12篇
  1981年   10篇
  1980年   16篇
  1979年   9篇
  1978年   9篇
  1977年   13篇
  1975年   6篇
  1974年   5篇
  1967年   3篇
排序方式: 共有2697条查询结果,搜索用时 15 毫秒
51.
In the auditory brain, some populations of neurons exhibit stimulus-specific adaptation (SSA), whereby they adapt to frequently occurring stimuli but retain sensitivity to stimuli that are rare. SA has been observed in auditory structures from the midbrain to the primary auditory cortex (A1) and has been proposed to be a precursor to the generation of deviance detection. SSA is strongly expressed in non-lemniscal regions of the medial geniculate body (MGB), the principal nucleus of the auditory thalamus. In this account we review the state of the art of SSA research in the MGB, highlighting the importance of this auditory centre in detecting sounds that may be relevant for survival.  相似文献   
52.
To better understand the recent success/emergence of Salmonella enterica serotype 4,[5],12:i:- we characterized the population diversity, fljAB deletion patterns, antibiotic resistance features and associated genetic elements of a comprehensive collection obtained in the last decade from Portugal (2002–2010). One hundred thirty-one isolates from human clinical specimens, food, environment and piggeries, verified by PCR as S. 4,[5],12:i:-, were studied for clonality (Pulsed-Field Gel Electrophoresis and Multilocus Sequence Typing), antibiotic resistance by phenotypic (disk diffusion and/or agar dilution) and genotypic (PCR/Restriction Fragment Length Polymorphism and sequencing, genomic location) methods and fljAB-deletions (PCR). Plasmid analysis included determination of size, content and characterization of the incompatibility group (PCR-Based Replicon Typing and I-CeuI/S1-hybridization). Results showed three multidrug-resistant (MDR) clones circulating and causing infections, associated with particular phenotypic and genotypic features. Most of the isolates belonged to the widespread European (ASSuT phenotype, RR1-RR2 resistance regions, ST34) and Spanish (carrying a sul3-type III integron within IncA/C plasmids, ST19) clones circulating in Europe. A third clone, here designated Southern European clone (carrying a sul3-type I integron within IncR plasmids, ST19), presents a fljAB region different from the previous clones and similar to the US strains, despite differences in the MDR mobile genetic platforms. The success of S. 4,[5],12:i:- might be related to the selective advantage offered by MDR profiles associated with stable genetic elements, also carrying virulence features, along with well adapted clones to the animal food production and causing human infections.  相似文献   
53.
Ileal intussusception is the invagination of the small intestine within itself and accounts for 1% of cases of acute obstruction. However, physicians do not initially consider intussusception as a possible diagnosis of obstruction due to its rarity in adults. Herein, we report the case of a 22-year-old male who was admitted to the Emergency Department with continuous abdominal pain. Ultrasonography and computed tomography revealed an ileal intussusception. The patient underwent surgical removal of the segment of the small bowel. Unexpectedly, pathology revealed that the invagination occurred due to a parasite egg, with features suggestive of Schistosoma species. Schistosomiasis, although considered a parasitic disease in tropical countries, is not absent from Europe and though it is highly improbable, it may be responsible for cases of intussusception in adults.  相似文献   
54.
Ecotoxicology - This study aimed to investigate the mode of action of cadmium (Cd) toxicity at cell level, especially at early stages of plant exposure. Tomato seedlings were cultivated in growth...  相似文献   
55.
Two cases of swallowing of foreign material related to dental implants during dental practice are described. A conservative approach by clinical-radiographic follow-up was performed in both cases; however, one of the patients required colonoscopy under general anesthesia for the removal of the impacted foreign body from the intestinal region. These complications not only have associated economic cost but also carry the risk of malpractice litigation against the professional; thus, the surgeon was responsible for all the costs of hospital and surgery management of this case. Details of the clinical signs, radiographic examinations, type of treatment, and follow-up are presented.  相似文献   
56.

Background  

Glioblastoma remains one of the most devastating human malignancies, and despite therapeutic advances, there are no drugs that significantly improve the patient survival. Altered expression of the Aurora kinases was found in different malignancies, and their inhibition has been studied in cancer therapy. In this study, we analyzed the expression of Aurora A and Aurora B in glioblastoma samples and also analyzed whether the effects of Aurora kinase inhibition were associated with temozolomide or not on cell lines and primary cultures of glioblastoma.  相似文献   
57.
58.
该文旨在介绍Beth Israel医疗中心采用大剂量术中放疗(HDR-IORT)治疗复发头颈癌的经验。对2001-2010年间头颈癌局部复发接受大剂量HDR-IORT的患者进行回顾分析。结果,76例患者的87个部位在肿瘤切除后接受了治疗。术后2年控制率为62%。平均总生存期为19个月,其中42%的患  相似文献   
59.
60.

Introduction

In vitro hydrodynamic characterization of prosthetic heart valves provides important information regarding their operation, especially if performed by noninvasive techniques of anemometry. Once velocity profiles for each valve are provided, it is possible to compare them in terms of hydrodynamic performance. In this first experimental study using laser doppler anemometry with mechanical valves, the simulations were performed at a steady flow workbench.

Objective

To compare unidimensional velocity profiles at the central plane of two bi-leaflet aortic prosthesis from St. Jude (AGN 21 - 751 and 21 AJ - 501 models) exposed to a steady flow regime, on four distinct sections, three downstream and one upstream.

Methods

To provide similar conditions for the flow through each prosthesis by a steady flow workbench (water, flow rate of 17L/min. ) and, for the same sections and sweeps, to obtain the velocity profiles of each heart valve by unidimensional measurements.

Results

It was found that higher velocities correspond to the prosthesis with smaller inner diameter and instabilities of flow are larger as the section of interest is closer to the valve. Regions of recirculation, stagnation of flow, low pressure, and flow peak velocities were also found.

Conclusions

Considering the hydrodynamic aspect and for every section measured, it could be concluded that the prosthesis model AGN 21 - 751 (RegentTM) is superior to the 21 AJ - 501 model (Master Series). Based on the results, future studies can choose to focus on specific regions of the these valves.  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