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   15772篇
  免费   1477篇
  国内免费   578篇
耳鼻咽喉   65篇
儿科学   331篇
妇产科学   35篇
基础医学   1288篇
口腔科学   120篇
临床医学   2424篇
内科学   3190篇
皮肤病学   30篇
神经病学   950篇
特种医学   1533篇
外国民族医学   6篇
外科学   1845篇
综合类   1877篇
现状与发展   1篇
预防医学   723篇
眼科学   300篇
药学   1265篇
  25篇
中国医学   633篇
肿瘤学   1186篇
  2024年   51篇
  2023年   331篇
  2022年   700篇
  2021年   908篇
  2020年   750篇
  2019年   687篇
  2018年   663篇
  2017年   694篇
  2016年   637篇
  2015年   612篇
  2014年   1083篇
  2013年   1150篇
  2012年   845篇
  2011年   932篇
  2010年   775篇
  2009年   732篇
  2008年   694篇
  2007年   688篇
  2006年   657篇
  2005年   540篇
  2004年   462篇
  2003年   403篇
  2002年   336篇
  2001年   305篇
  2000年   254篇
  1999年   200篇
  1998年   189篇
  1997年   172篇
  1996年   169篇
  1995年   164篇
  1994年   122篇
  1993年   102篇
  1992年   126篇
  1991年   90篇
  1990年   85篇
  1989年   83篇
  1988年   54篇
  1987年   58篇
  1986年   39篇
  1985年   54篇
  1984年   39篇
  1983年   30篇
  1982年   28篇
  1981年   27篇
  1980年   20篇
  1979年   21篇
  1978年   18篇
  1977年   14篇
  1976年   11篇
  1975年   6篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
Three-dimensional imaging for the quantification of myocardial motion is a key step in the evaluation of cardiac disease. A tagged magnetic resonance imaging method that automatically tracks myocardial displacement in three dimensions is presented. Unlike other techniques, this method tracks both in-plane and through-plane motion from a single image plane without affecting the duration of image acquisition. A small z-encoding gradient is subsequently added to the refocusing lobe of the slice-selection gradient pulse in a slice following CSPAMM acquisition. An opposite polarity z-encoding gradient is added to the orthogonal tag direction. The additional z-gradients encode the instantaneous through plane position of the slice. The vertical and horizontal tags are used to resolve in-plane motion, while the added z-gradients is used to resolve through-plane motion. Postprocessing automatically decodes the acquired data and tracks the three-dimensional displacement of every material point within the image plane for each cine frame. Experiments include both a phantom and in vivo human validation. These studies demonstrate that the simultaneous extraction of both in-plane and through-plane displacements and pathlines from tagged images is achievable. This capability should open up new avenues for the automatic quantification of cardiac motion and strain for scientific and clinical purposes.  相似文献   
92.
佛山地区1991~2000年小儿消化道出血病因研究   总被引:3,自引:1,他引:2  
【目的】探讨佛山地区小儿消化道出血的临床特点,了解小儿消化道出血的病因。【方法】采用回顾性调查方法对1363例消化道出血患儿进行病因分析。【结果】1363例消化道出血患儿除全身疾病引起出血的146例外,消化道局部病变引起出血者1217例;属上消化道出血395例,确诊为溃疡病232例(57.3%),各种类型胃炎及十二指肠球炎共123例(30.4%),其次为食管静脉曲张、胃粘膜脱垂、食管贲门撕裂症、食管裂孔疝、十二指肠息肉等,明确病因372例(94.2%)。属下消化道出血822例,确诊为肠息肉526例(54.9%),结肠炎121例(12.6%),其次为溃疡性结肠炎、肠套叠、美克尔憩室、阿米巴结肠炎、小肠血管瘤、血管畸形、肠结核等,明确病因800例(97.3%)。【结论】小儿消化道出血应根据不同年龄、不同出血部位选择有效诊断方法,以提高病因诊断率,减少对患儿生长发育及身心健康的影响。  相似文献   
93.
头低位模拟失重状态对前庭功能的影响   总被引:4,自引:1,他引:3  
为研究头低位模拟失重对运动病症状、垂直视动眼震(VOKN)及体液重新分配的影响,在头低位-10°的模拟失重状态下,采用大视野的垂直视动刺激,观察18名正常人的运动病症状、VOKN、激素(AVP、VIP、CORT、ALDO)的反应特点。结果表明,头低位-10°状态下的大视野垂直视动刺激可以诱发出明显的运动病症状,头低位-10°的垂直视动刺激比坐位更容易诱发运动病。坐位状态VOKN慢相速度有明显的方向性不对称,敏感组VOKN方向性不对称有显著差异(P<0.05)。头低位-10°时VOKN的不对称现象不明显,向下方向运动的VOKN慢相速度显著增加。分析指出,头低位-10°状态下垂直视动刺激比坐位和秋千刺激的贡献率大。尿中CORT(皮质醇)在秋千和头低位的垂直视动刺激前后有显著性增加。提示:大视野的垂直视动刺激与头低位-10°两种刺激的结合可能成为预测空间运动病的方法之一.  相似文献   
94.
应用硫代乙酰胺灌胃复制暴发性肝功能衰竭大鼠模型,测定了大鼠胃肠推进运动的变化,结果:暴发性肝功能衰竭大鼠胃肠推进运动较正常大鼠显著减弱。肌肉注射胃复安、西沙必利或红霉素可显著增强肝功能衰竭大鼠的胃肠推进运动,这一效应可被皮下注射阿托品所完全阻断。表明这些药物可能通过迷走神经而使胃肠推进运动增强。  相似文献   
95.
Gastrointestinal involvement in von Recklinghausen's disease occurs in three principal forms: hyperplasia of the submucosal and myenteric nerve plexuses and mucosal ganglioneuromatosis which leads to disordered gut motility; gastrointestinal stromal tumours showing varying degrees of neural or smooth muscle differentiation; and a distinctive glandular, somatostatin-rich carcinoid of the periampullary region of the duodenum that contains psammoma bodies and which may be associated with phaeochromocytoma. This review describes the histopathological features of these lesions and discusses potential pitfalls in their differential diagnosis. Their accurate identification has significant implications for clinical management and may even provide the first pointer to the diagnosis of neurofibromatosis.  相似文献   
96.
BACKGROUND: Gastrointestinal spasms and cramps are common in children as well as in adults. Alternative medical practices such as chiropractice and homeopathy are becoming increasingly popular in Europe and the USA. The effectiveness and tolerability of the homeopathic preparation Spascupreel was compared with that of hyoscine butylbromide treatment in children <12 years of age. METHODS: An observational cohort study in 204 children <12 years was conducted over a 1 week treatment period. The efficacy of the respective therapies were evaluated on the effect on severity of spasms and clinical symptoms (pain/cramps, sleep disturbances, distress, eating or drinking difficulties and frequent crying). Compliance was evaluated on a four-point scale from 'very good' to 'low'. Evaluation was done by the practitioner based on information given by the patient or minder. RESULTS: The analysis showed comparative improvements with the homeopathic preparation and hyoscine butylbromide therapy on severity of spasms, pain/cramps, sleep disturbances, eating or drinking difficulties, and frequent crying, all as evaluated by the practitioner. Both treatments were very well tolerated. CONCLUSIONS: For patients opting for a homeopathic therapy, Spascupreel seems to be an effective and well tolerated alternative to conventional therapies in children suffering from gastrointestinal spasms.  相似文献   
97.
Gastrointestinal cancers account for 20% of all cancer incidences worldwide. Colorectal cancer is the second most common cause of all cancer-related mortality and is increasing in Western societies. Infection and inflammation contribute to 15–20% of all malignancies, and are predisposing risk factors for gastrointestinal cancers. Helicobacter pylori infection is commonly associated with gastric cancers, and chronic inflammation increases the risk of colorectal cancer by 1% per year. Micronutrient status and common genetic variations in human populations modify risk for gastrointestinal cancer. Chronic inflammation promotes carcinogenesis by inducing gene mutations, inhibiting apoptosis, and stimulating an-giogenesis and cell proliferation. Inflammation also induces epigenetic alterations that are associated with cancer development. Two key genes in the inflammatory process, cyclooxygenase-2 (COX-2) and nuclear factor-kappa B (NF-kB), provide a mechanistic link between inflammation and cancer and are targets for chemoprevention. Dietary components, and human genetic variation that affects nutrient utilization, can directly modify inflammatory processes and/or suppress genomic alterations that are the molecular antecedents of cancers. The present report focuses on the convergence of genetic, nutritional, and inflammatory factors in the initiation and progression of gastrointestinal cancers, and the emerging dietary strategies for cancer prevention.  相似文献   
98.
Cytokines are involved in fever and other symptoms of the acute phase response induced by endotoxins. The aim of this work was to study the involvement of central tumour necrosis factor-alpha (TNF-alpha) in the changes induced by lipopolysaccharide (LPS) on gastrointestinal (GI) motility in sheep. Body temperature and myoelectric activity of the antrum, duodenum and jejunum was recorded continuously. Intravenous (i.v.) administration of LPS (0.1 micro g kg-1)-induced hyperthermia, decreased gastrointestinal myoelectric activity and increased the frequency of the migrating motor complex (MMC). These effects started 40-50 min after LPS and lasted for 6-7 h. TNF-alpha (50 and 100 ng kg-1) mimicked these effects when injected intracerebroventricularly (i.c.v.) but not i.v. Pretreatment with soluble recombinant TNF receptor (TNFR:Fc, 10 micro g kg-1, i.c.v.) abolished the TNF-induced actions and reduced those evoked by LPS. Furthermore, the effects induced by either LPS or TNF were suppressed by prior i.c.v. injection of indomethacin (100 micro g kg-1). In contrast, the i.v. injections of TNFR:Fc or indomethacin were ineffective. Our data suggest that LPS disturbs GI motility in sheep through a central pathway that involves TNF-alpha and prostaglandins sequentially.  相似文献   
99.
Splanchnic ischaemia and its role in multiple organ failure   总被引:3,自引:0,他引:3  
Multiple organ failure remains the leading cause of death in the intensive care unit. Increasing numbers of investigators have focused their attention on the role of gastrointestinal tract in the pathogenesis of this syndrome. Their data indicate that inadequate gut perfusion leads to a measurable imbalance between oxygen delivery and the needs of the tissues, i.e., ischaemia. Gut ischaemia of sufficient duration impairs gastrointestinal tract barrier function, facilitating the passage of enteric bacterial endotoxin into the circulation. It has been hypothesized that production of tumor necrosis factor α, and other biologic mediators by endotoxin–stimulated macrophages, triggers a generalized and uncontrolled inflammatory response that ultimately leads to multiple organ failure.
Preliminary evidence suggests that survival can be improved significantly if gut ischaemia is promptly identifed and aggressively treated by administration of fluids and inotropic drugs, using gastric intramucosal pH as the therapeutic endpoint. Future studies are needed to determine whether additional treatment modalities can improve outcome once the inflammatory response has fully developed.  相似文献   
100.
目的:了解黏膜相关淋巴瘤的凋亡水平及其所涉及到的信号传导通路。方法:收集33例胃肠黏膜相关淋巴样组织(MALT)淋巴瘤病例,通过TUNEL技术原位检测MALT淋巴瘤肿瘤细胞的凋亡水平,通过逆转录聚合酶链反应(RT-PCR)和免疫组织化学染色检测肿瘤的凋亡抑制蛋白2编码基因(API2)和Caspase3 mRNA及蛋白,对API2和Caspase3水平作半定量和定量分析。根据凋亡检测结果将全部病例分为两组,即凋亡细胞数每50个高倍视野小于或等于2的病例组和大于2的病例组,比较2组的API2和Caspase3 mRNA及蛋白。结果:半数以上的MALT淋巴瘤中存在凋亡抑制;凋亡抑制的MALT淋巴瘤病例中API2 mRNA及蛋白水平明显高于没有明显凋亡抑制的病例,但Caspase3 mRNA及蛋白水平在两组病例中表达没有明显的差异。结论:MALT淋巴瘤中存在明显的凋亡抑制,其发生与凋亡抑制因子API2的表达上调有关,但API2对凋亡的调节与Caspase3有关的信号传导通路无明显相关。  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