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   4275983篇
  免费   350918篇
  国内免费   15286篇
耳鼻咽喉   60884篇
儿科学   132905篇
妇产科学   111702篇
基础医学   654593篇
口腔科学   118694篇
临床医学   387519篇
内科学   774781篇
皮肤病学   103190篇
神经病学   366199篇
特种医学   170505篇
外国民族医学   912篇
外科学   651554篇
综合类   126085篇
现状与发展   23篇
一般理论   2581篇
预防医学   361980篇
眼科学   100384篇
药学   301659篇
  24篇
中国医学   11353篇
肿瘤学   204660篇
  2021年   55649篇
  2020年   35458篇
  2019年   58564篇
  2018年   73148篇
  2017年   55851篇
  2016年   62160篇
  2015年   75467篇
  2014年   110183篇
  2013年   175501篇
  2012年   117209篇
  2011年   120217篇
  2010年   122742篇
  2009年   125945篇
  2008年   107454篇
  2007年   113946篇
  2006年   123493篇
  2005年   118663篇
  2004年   119612篇
  2003年   110340篇
  2002年   100952篇
  2001年   154278篇
  2000年   150438篇
  1999年   139513篇
  1998年   71248篇
  1997年   67734篇
  1996年   65621篇
  1995年   61483篇
  1994年   55564篇
  1993年   51595篇
  1992年   103556篇
  1991年   98942篇
  1990年   94045篇
  1989年   91678篇
  1988年   85298篇
  1987年   83768篇
  1986年   79461篇
  1985年   77902篇
  1984年   65933篇
  1983年   58843篇
  1982年   48128篇
  1981年   44869篇
  1980年   42162篇
  1979年   57821篇
  1978年   47028篇
  1977年   41590篇
  1976年   38651篇
  1975年   37843篇
  1974年   42413篇
  1973年   40547篇
  1972年   38014篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Aim : The study was designed to determine the effect of computerized nutrition information on consumer food choice in two workplace restaurants, one in which customers had to pay for their lunch and the other providing a free lunch. Methods : Customers entering the restaurants were asked to make selections from the menu on a computer screen. The energy, saturated fatty acids, non-milk extrinsic sugars and non-starch polysaccharide content of the meal selected was displayed graphically in proportion to the dietary reference values. They were given the opportunity to change their selected meal and the composition of all meals was recorded. Results : The nutritional composition of the first meal provoked 16% of customers to make a second selection. The proportion of energy in the first selection had been 31% higher for saturated fatty acids and 23% higher for non-milk extrinsic sugars than the first selection made by people who were satisfied with their first choice. In their second attempt they succeeded in reducing both nutrients to levels similar to those present in the meals selected by people who had been satisfied with their first selection. Customers>> selections for non-starch polysaccharide and energy did not differ between the groups. The main changes made by customers to achieve improved second choices were to omit dishes (44%), add dishes (19%), make changes within a menu category (46%), and make changes from one menu category to another (26%). Conclusion : It was concluded that provision of graphical nutrition information on a computer screen could be used by a subset of the users of both restaurants to enable them to improve their menu selections to a similar composition to that selected by the other people who used the computer system.  相似文献   
992.
993.
为研究包钢的原料中所含天然钍对作业工人健康的影响,对5985人的暴露队列进行了17年的流行病学调查。结果发现,作业工人外周血淋巴细胞染色体畸变率随年附加有效剂量的增加而升高(与对照组比较P<0.01)。工龄为5~14年者增加较快,15年后增加缓慢,趋于平衡。尘肺分析结果提示,天然钍可能增强SiO2的致肺纤维化作用。肿瘤死亡率除胃癌外,其余RR均大于1,但无统计学意义。相距一年的两次植物血球凝集素(PHA)皮试反应均有增强,但外周血淋巴细胞离体照射后,染色体畸变未见适应性。女工妊娠期从事钍作业,其所生子女的智力发育无明显异常。  相似文献   
994.
995.
996.
Image-directed color Doppler ultrasonography (ICDUS) studies of 86 patients with superficial solid masses yielded significantly lower resistive index (RI) values in acute inflammatory lesions, but no significant difference between the maximum systolic flow velocities (S) of the patient groups with malignant, benign, and acute inflammatory lesions. When analyzed separately, the malignant soft-tissue tumor subgroup was shown to have significantly higher mean RI compared to that of the malignant node subgroup. We conclude that RI may be useful in the differentiation of acute inflammatory masses from other pathological entities. Malignant soft-tissue tumors, especially sarcomas, may have different Doppler features from those of carcinomatous tumors. © 1995 John Wiley & Sons, Inc.  相似文献   
997.
998.
999.
Dantrolene seems to be the causal therapy in malignant hyperthermia (MH) crisis but the complex mechanisms of MH and dantrolene therapy are still not fully understood. The influence of dantrolene on ryanodine-induced contractures has been reported in animal studies only. In the present study 20 patients from] 7 families were tested for MH using the protocol of the European Malignant Hyperthermia Group. In addition ryanodine-induced contractures were evaluated following bolus application of 10.0 μmol · 1-1 ryanodine. After pretreatment with 1 μimol · 1-1 dantrolene ryanodine-provoked contractures developed significantly later in MHS (15.8±1.8 min) and MHN (46.0±4.2 min) muscle specimens than after ryanodine alone (MHS 4.8±0.7 min), (MHN 13.7±0.9 min). They were no longer observed in either group after pretreatment with 5 μimol · 1-1 dantrolene. We conclude that dantrolene is able to attenuate ryanodine-induced contractures dose-dependendy, and therefore it is speculated that dantrolene could specifically act at the ryanodine receptor binding site.  相似文献   
1000.
PURPOSE: This study was undertaken to clarify the importance of bleeding vascular ectasia of the colon as the etiology of massive lower gastrointestinal hemorrhage in patients 40 years of age or younger. METHODS: An otherwise healthy 21-year-old male was admitted to a tertiary medical center with massive lower gastrointestinal hemorrhage. Technetium-labeled red blood cell scan, selective visceral angiography, and colonoscopy identified the source of bleeding as vascular abnormality of the descending colon. Segmental colonic resection was performed. RESULTS: Histologic review of the specimen demonstrated a vascular ectasia. The patient recovered uneventfully and has had no further stigmata of hemorrhage. A review of the literature was undertaken to make clear the significance of vascular ectasia as the source for massive colonic hemorrhage in the young adult. CONCLUSION: This is the first report that documents histologically a vascular ectasia as the source of massive lower gastrointestinal hemorrhage in an otherwise healthy patient less than 40 years of age. Vascular ectasia is an uncommon cause of lower gastrointestinal hemorrhage in the young adult.The Chief, Bureau of Medicine and Surgery, Navy Department, Washington, DC, Clinical Investigation Program sponsored this report #84-16-1968-532, as required by HSETCINST 6000.41A. The views expressed in this article are those of the authors and do not reflect the official policy or position of the Department of the Navy, Department of Defense, or the United States Government.  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