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   8043篇
  免费   589篇
  国内免费   86篇
耳鼻咽喉   16篇
儿科学   236篇
妇产科学   149篇
基础医学   886篇
口腔科学   128篇
临床医学   1025篇
内科学   1689篇
皮肤病学   104篇
神经病学   610篇
特种医学   602篇
外科学   1324篇
综合类   263篇
一般理论   6篇
预防医学   754篇
眼科学   80篇
药学   423篇
中国医学   9篇
肿瘤学   414篇
  2022年   52篇
  2021年   101篇
  2020年   74篇
  2019年   117篇
  2018年   141篇
  2017年   95篇
  2016年   120篇
  2015年   117篇
  2014年   142篇
  2013年   282篇
  2012年   354篇
  2011年   392篇
  2010年   242篇
  2009年   203篇
  2008年   311篇
  2007年   371篇
  2006年   359篇
  2005年   296篇
  2004年   331篇
  2003年   295篇
  2002年   290篇
  2001年   275篇
  2000年   271篇
  1999年   237篇
  1998年   174篇
  1997年   153篇
  1996年   139篇
  1995年   103篇
  1994年   106篇
  1993年   108篇
  1992年   198篇
  1991年   201篇
  1990年   187篇
  1989年   193篇
  1988年   148篇
  1987年   154篇
  1986年   136篇
  1985年   148篇
  1984年   114篇
  1983年   94篇
  1982年   70篇
  1981年   55篇
  1980年   57篇
  1979年   74篇
  1978年   68篇
  1977年   58篇
  1976年   49篇
  1975年   45篇
  1974年   44篇
  1973年   42篇
排序方式: 共有8718条查询结果,搜索用时 15 毫秒
101.
Summary The results of the European Working Party for Hypertension in the Elderly Study showed that treatment of high blood pressure reduced the morbidity and mortality from strokes and myocardial infarction and reduced the incidence of heart failure in elderly patients. The largest number of hypertensive patients are elderly, and it is in this group of patients that the maximum benefit of treatment might be expected. The present study was designed to study in detail the efficacy and tolerability of ketanserin in an elderly population. Seventeen elderly (> 70 years) patients with a lying systolic blood pressure of 160 mmHg and/or a diastolic blood pressure of 90 mmHg were included in the study. For the 12 patients who completed the study, the mean blood pressure was significantly reduced on ketanserin compared with placebo (p<0.001) in the supine and erect positions. The mean net changes in blood pressure after 8 weeks were 21/17 mmHg and 23/16 mmHg erect. Heart rate was also significantly reduced (p<0.001) by a mean of 8 beats/min lying and 9 beats/min erect. Analysis of ambulatory 24-hour ECG tapes showed no significant effect of ketanserin on heart rhythms. Ketanserin therapy had no significant effect on routine hematology, plasma electrolytes, biochemistry, or urinalysis. Total exchangeable sodium and potassium and body weight were also unchanged. On ketanserin treatment, the overall quality of life score was significantly improved (p=0.002; analysis of variance on log transformed data) compared with the placebo phase.  相似文献   
102.
This research analyzes the effect which recent speed limit increases on rural interstate highways have had upon accidents that are alcohol-related. Although there has been considerable work on the separate highway safety effects of higher speed limits and alcohol-related accidents, surprisingly little work has explicitly examined the relationship between them. Based upon extensive county wide data on alcohol-related accidents and several theoretically important determinants of these accidents for the state of Indiana and over the period 1981 through 1989, fixed effects models were estimated. For the state as a whole, the analysis finds that the increase in rural interstate speed limits increased alcohol-related accidents and the magnitude of the effect was statistically significant. In addition, the relaxed speed limit led to a significant redistribution of alcohol-related accidents away from higher speed environments and towards lower speed environments. With few exceptions, this was true for every type of alcohol-related highway accident examined.  相似文献   
103.
SARS-CoV-2 NSP12, the viral RNA-dependent RNA polymerase (RdRp), is required for viral replication and is a therapeutic target to treat COVID-19. To facilitate research on SARS-CoV-2 NSP12 protein, we developed a rat monoclonal antibody (CM12.1) against the NSP12 N-terminus that can facilitate functional studies. Immunoblotting and immunofluorescence assay (IFA) confirmed the specific detection of NSP12 protein by this antibody for cells overexpressing the protein. Although NSP12 is generated from the ORF1ab polyprotein, IFA of human autopsy COVID-19 lung samples revealed NSP12 expression in only a small fraction of lung cells including goblet, club-like, vascular endothelial cells, and a range of immune cells, despite wide-spread tissue expression of spike protein antigen. Similar studies using in vitro infection also generated scant protein detection in cells with established virus replication. These results suggest that NSP12 may have diminished steady-state expression or extensive posttranslation modifications that limit antibody reactivity during SARS-CoV-2 replication.  相似文献   
104.
乔振军  黄裕新  王景杰 《医学争鸣》2000,21(10):1233-1233
1 病例报告 女 ,45岁 ,因吞咽困难 16 mo伴发热 15 d,于1999- 0 7- 12入院 .于 16 mo前与人争吵后出现吞咽困难 ,以进食馒头、面条为著 ,剑突下有时出现梗噎感 ,随即呕吐 ,呕出所进食物及粘液 ,情绪波动可诱发症状加重 ,伴食欲减退、返酸 .15 d前无诱因出现不规则发热 ,T38~ 39℃ ,上腹痛加重 ,全身酸困不适 ,乏力、头晕、消瘦 .追问病史 ,患者 5 a前双手、足疼痛麻木 ,尤以受凉、精神刺激后明显 ,手指初发白 ,继而发紫 ,变红 ,且麻木疼痛加重 ,手足小关节渐僵硬、畸形 .曾到多家医院就诊 ,诊断 :“雷诺病、类风湿性关节炎”.2 a前出现…  相似文献   
105.
106.
When a time-limited day treatment program was reconfigured to serve individuals with long-standing psychotic disorders, the number of treatment episodes exceeding six months rose to 70%. To justify this concentration of resources, the program needed methods to identify individuals for whom sustained treatment was appropriate. This report describes development of utilization review methods adapted to publicly funded day treatment of individuals with serious mental illness and training of clinicians in new documentation skills. Data from three years of operation suggest that symptom severity is not a reliable indicator of medical necessity in day treatment. As expected with a clinically based system, a composite measure of benefit and medical necessity indicators weighted toward functioning in living, learning, working, and socializing environments predicted physician reviewer denial of continued day treatment, but length of stay did not.  相似文献   
107.
Localized brain activation in response to moving visual stimuli was studied by functional magnetic resonance imaging (fMRI). Stimuli were 100 small white dots randomly arranged on a visual display. During the Motion condition, the dots moved along random, noncoherent linear trajectories at different velocities. During the Blink condition, the dots remained stationary but blinked on and off every 500 ms. The Motion and Blink conditions continuously alternated with 10 cycles per run and 6–8 runs per experiment. In half of the runs, the starting stimulus condition was Motion, while in the remaining runs it was Blink. A series of 128 gradient echo echoplanar images were acquired from 5–7 slices during each run using a 1.5 T GE Signa with an Advanced NMR echoplanar subsystem. The time series for each voxel were analyzed in the frequency domain. Voxels which demonstrated a significant spectral peak at the alternation frequency and whose phase changed in response to stimulus order were considered activated. These activated voxels were displayed upon high resolution anatomical images to determine the sites of activation and were also transformed into the coordinates of Talairach and Tournoux ([1988] Co-planar Stereotaxic Atlas of the Human Brain, New York: Thieme) for comparison to prior neuroimaging studies. Seven of ten subjects showed clusters of activation bilaterally at the junction of the temporal and occipital lobes (area 37) in response to moving stimuli. Most activated voxels were located within or adjacent to a region designated the parietal-temporal-occipital fossa, or PTOF. Five subjects also showed activation to moving stimuli in midline occipital cortex. The activated voxels in midline cortex had a significantly shorter phase delay in their MR signal change relative to voxels in PTOF. © 1995 Wiley-Liss, Inc. 1
  • 1 This article is a US Government work and, as such, is in the public domain in the United States of America
  •   相似文献   
    108.
    109.
    Recent major surgery is an exclusion criterion for thrombolysis. Six patients with acute ischemic stroke underwent intra-arterial thrombolysis after recent open heart surgery without clinically significant bleeding complications, although one patient developed a small, asymptomatic cerebellar hemorrhage. Intra-arterial thrombolysis may be an option for patients with cerebral embolism in the perioperative period.  相似文献   
    110.
    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