全文获取类型
收费全文 | 172183篇 |
免费 | 16624篇 |
国内免费 | 11671篇 |
专业分类
耳鼻咽喉 | 1515篇 |
儿科学 | 2296篇 |
妇产科学 | 1931篇 |
基础医学 | 18594篇 |
口腔科学 | 3233篇 |
临床医学 | 21630篇 |
内科学 | 23506篇 |
皮肤病学 | 1938篇 |
神经病学 | 8441篇 |
特种医学 | 6814篇 |
外国民族医学 | 82篇 |
外科学 | 17496篇 |
综合类 | 31044篇 |
现状与发展 | 36篇 |
一般理论 | 25篇 |
预防医学 | 13137篇 |
眼科学 | 5145篇 |
药学 | 18722篇 |
134篇 | |
中国医学 | 11054篇 |
肿瘤学 | 13705篇 |
出版年
2024年 | 614篇 |
2023年 | 2484篇 |
2022年 | 6308篇 |
2021年 | 8200篇 |
2020年 | 6397篇 |
2019年 | 5580篇 |
2018年 | 5809篇 |
2017年 | 5461篇 |
2016年 | 5244篇 |
2015年 | 7608篇 |
2014年 | 9643篇 |
2013年 | 9513篇 |
2012年 | 13583篇 |
2011年 | 14229篇 |
2010年 | 10119篇 |
2009年 | 8286篇 |
2008年 | 9926篇 |
2007年 | 9779篇 |
2006年 | 9578篇 |
2005年 | 8440篇 |
2004年 | 6822篇 |
2003年 | 6638篇 |
2002年 | 5560篇 |
2001年 | 4595篇 |
2000年 | 3640篇 |
1999年 | 3265篇 |
1998年 | 1931篇 |
1997年 | 1960篇 |
1996年 | 1437篇 |
1995年 | 1308篇 |
1994年 | 1141篇 |
1993年 | 698篇 |
1992年 | 782篇 |
1991年 | 670篇 |
1990年 | 629篇 |
1989年 | 513篇 |
1988年 | 467篇 |
1987年 | 382篇 |
1986年 | 320篇 |
1985年 | 242篇 |
1984年 | 151篇 |
1983年 | 110篇 |
1982年 | 52篇 |
1981年 | 57篇 |
1980年 | 33篇 |
1979年 | 66篇 |
1978年 | 24篇 |
1974年 | 29篇 |
1973年 | 18篇 |
1968年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Conventional computerized tomography (CT) technique is based on the absorption contrast. In recent years, X-ray phase-contrast CT (PCCT) has been developing rapidly. It uses the phase information to reconstruct the object and provide high contrast and spatial resolution. Diffraction enhanced imaging (DEI) method is one of the three phase-sensitive X-ray imaging techniques. DEI method employs an analyzer crystal to extract the object's refraction information which can be used for CT. However, when DEI refraction CT is combined with the conventional CT algorithm, it should be satisfied that the refraction information of an arbitrary point in the object is invariable at every projection view. In this paper, the invariance condition of refraction information is analyzed and two feasible methods are provided for reconstruction. Using these two methods, two samples of weak absorption are reconstructed with the experimental data obtained at Beijing Synchrotron Radiation Facility (BSRF). 相似文献
62.
Julia Yu-Fong Chang Jeng-Tzung Wang Yi-Ping Wang Bu-Yuan Liu Andy Sun Chun-Pin Chiang 《台湾医志》2003,102(12):876-882
BACKGROUND AND PURPOSE: Odontoma is the most common odontogenic tumor. It includes 2 types, the compound and complex odontomas. There has not been a series study of the clinical and histologic features of odontomas from Taiwan. This study evaluated the clinicopathologic features of odontoma in Taiwanese. METHODS: Cases of odontoma treated from 1998 to 2002 identified from medical records were included. The microscopic features, radiographic features, and clinical history of the patients were reviewed and analyzed. RESULTS: A total of 81 odontomas in 81 patients (36 males and 45 females) were included. There were 62 compound and 19 complex odontomas. The mean age of the patients was 18 years with the majority of odontomas occurring in the first (32%) and second decade (38%) of life. Odontomas had a marked predilection for the maxilla (70%) and for the anterior region of the jaw (83%), particularly for the anterior maxilla (62%). Sixty four (79%) of the 81 odontomas were associated with 80 impacted teeth, including 71 permanent teeth, 2 deciduous teeth, and 7 supernumerary teeth. Of the 71 impacted permanent teeth, the maxillary central incisor (27%) was most commonly affected, followed by the maxillary canine (26%) and mandibular canine (24%). Histologic examination revealed enamel matrix in 90%, dentin in 100%, cementum in 88%, pulp tissue in 96%, fibrous capsule in 93%, ghost cells in 83%, reduced enamel epithelium in 86%, and nests of odontogenic epithelium in 58% of odontomas. Dentigerous cyst was associated with 9% of odontomas. CONCLUSIONS: In this series, odontomas occurred most often in the first and second decade of life. Although complex odontomas are usually found in the posterior jaw, in this Taiwanese series they were most commonly found in the anterior maxilla. Odontoma is frequently associated with an impacted tooth and occasionally with a dentigerous cyst. No recurrence of odontomas was found after surgical excision with follow-up of 1 to 15 years. 相似文献
63.
脉络膜黑色素瘤脱色素处理后Caspase-3的免疫组化研究 总被引:4,自引:0,他引:4
目的 观察凋亡基因Caspase-3在脉络膜黑色素瘤(choroidal melanoma)中的表达及分型与细胞凋亡的关系。方法 收集20例脉络膜黑色素瘤标本,对其进行Caspase-3免疫组织化学染色,观察表达情况及染色强度。结果 Caspase-3在脉络膜黑色素瘤有较好的表达,在梭形细胞型中5例/6例呈阳性表达,在混合型中6例/8例呈阳性表达,在上皮样瘤细胞型中3例/4例呈阳性表达,在坏死型中1例/2例呈阳性表达,且在各型之间没有显著性差异(P>0.05)。结论 凋亡在脉络膜黑色素瘤中存在;Caspase-3在脉络膜黑色素瘤的发生发展中起重要作用。 相似文献
64.
1.5T超导磁共振制冷系统的工作原理及日常维护 总被引:1,自引:0,他引:1
介绍GE 1.5T超导磁共振制冷系统的组成和工作原理,讨论日常维护的要点及其必要性。 相似文献
65.
66.
67.
68.
可切除原发性十二指肠恶性肿瘤X线征象分析 总被引:2,自引:0,他引:2
目的 :对可切除的原发性十二指肠恶性肿瘤X线征象进行分析。方法 :对 2 6例原发性十二指肠恶性肿瘤胃肠道造影及CT征象进行了回顾性对比分析总结。结果 :全部病例均经手术病理证实 ,其中腺癌 2 2例 ,平滑肌肉瘤 3例 ,非何杰金氏淋巴瘤 1例。描述包括肿瘤的部位 ,造影X线表现 (黏膜破坏 ,充盈缺损及龛影 ,管腔不规则狭窄 ,肠腔外改变等 )及CT表现 (肠壁增厚肠腔狭窄 ,局部肿块 ,梗阻性改变及转移 )。不能手术切除的影像学征象为 :肿瘤直径大于 6cm ;腹腔、系膜淋巴结成团肿大 ;腔静脉、肠系膜动静脉等重要血管管径被包绕大于 2 / 3时。结论 :CT与X线造影对肿瘤的位置、大小、形态 ,肿瘤的继发征象的术前评价 ,能够提供能否手术切除的重要依据。 相似文献
69.
70.