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   2692篇
  免费   164篇
  国内免费   115篇
耳鼻咽喉   10篇
儿科学   98篇
妇产科学   51篇
基础医学   338篇
口腔科学   50篇
临床医学   265篇
内科学   584篇
皮肤病学   53篇
神经病学   258篇
特种医学   416篇
外国民族医学   1篇
外科学   286篇
综合类   50篇
预防医学   178篇
眼科学   42篇
药学   148篇
中国医学   7篇
肿瘤学   136篇
  2023年   15篇
  2021年   31篇
  2020年   18篇
  2019年   39篇
  2018年   42篇
  2017年   32篇
  2016年   46篇
  2015年   51篇
  2014年   43篇
  2013年   95篇
  2012年   75篇
  2011年   85篇
  2010年   73篇
  2009年   82篇
  2008年   105篇
  2007年   139篇
  2006年   114篇
  2005年   127篇
  2004年   75篇
  2003年   73篇
  2002年   63篇
  2001年   69篇
  2000年   69篇
  1999年   67篇
  1998年   105篇
  1997年   104篇
  1996年   113篇
  1995年   71篇
  1994年   67篇
  1993年   72篇
  1992年   59篇
  1991年   48篇
  1990年   49篇
  1989年   62篇
  1988年   53篇
  1987年   67篇
  1986年   42篇
  1985年   68篇
  1984年   30篇
  1983年   23篇
  1982年   30篇
  1981年   25篇
  1980年   42篇
  1979年   20篇
  1978年   22篇
  1977年   21篇
  1976年   35篇
  1975年   21篇
  1973年   18篇
  1970年   15篇
排序方式: 共有2971条查询结果,搜索用时 15 毫秒
11.
A morphometric study of nucleolar organizer regions (NOR) was performed to analyze their distribution, volume, number and shape in the different strata of human normal oral mucosa epithelium and papilloma and in squamous cell carcinoma employing microphotographs of silver-stained paraffin sections. The different NOR-related parameters evidenced significant differences between normal mucosa, papilloma and squamous cell carcinoma. The functional polarity of normal mucosa epithelium and of papilloma is also evidenced in terms of NOR-related parameters. The discriminative value of certain NOR parameters was demonstrated.  相似文献   
12.
Thirty-five patients hospitalized for recent angiographically documented arterial occlusion in the legs (27 femoropopliteal arteries and eight grafts) benefited from local fibrinolytic therapy delivered at the site of the occlusion with a 4- or 5-F catheter. This therapy combined a continuous urokinase (UK) infusion of 1,000 U/kg/hour and a lysyl plasminogen (LYS-PLG) infusion of 15 microkatals every 30 minutes. Angiographically confirmed lysis was obtained in 85% of the cases. Only 3% of the patients had major and 6% had minor groin hematomas. Only two patients had concentrations of fibrinogen as low as 100 mg/dl. Intravascular infusion of UK-LYS-PLG is as effective as streptokinase. Its excellent tolerance makes it a good alternative in the treatment of acute ischemia in the lower limbs.  相似文献   
13.
Two middle-aged patients presented with rapidly progressive dementia and ataxia, nonspecific electroencephalography findings, and negative cerebrospinal fluid (CSF) protein 14-3-3. Both patients underwent brain magnetic resonance imaging (MRI) scans that demonstrated abnormalities on diffusion-weighted imaging (DWI) sequences, and both were later confirmed to have Creutzfeldt-Jakob disease. (CJD) by tissue examination. Because a recent position paper from the American Academy of Neurology characterized CSF protein 14-3-3 as a gold standard for clinically diagnosing CJD, the authors reviewed studies of CJD in which DWI-MRI imaging and CSF protein 14-3-3 studies were both performed. Among 19 reported cases of CJD with DWI-MRI lesions, CSF protein 14-3-3 was negative in 6 cases and positive in 2 others. The authors' findings suggest that multifocal cortical and subcortical hyperintensities confined to gray matter regions in DWI-MRI may be a more useful noninvasive diagnostic marker for CJD than CSF protein 14-3-3. These observations provide a compelling rationale for a prospective comparative study.  相似文献   
14.
Chronic rejection is the major hurdle to long-term survival after lung transplantation. Endobronchial infection with Pseudomonas aeruginosa is common in patients with chronic rejection and this may further contribute to deterioration of the allograft. Inhaled tobramycin is commonly used to treat P aeruginosa airways infection in patients with cystic fibrosis. The safety of inhaled tobramycin in transplant recipients, however, has not been established. We describe the first report of a lung transplant recipient who developed renal failure and vestibular injury after receiving inhaled tobramycin. We review the literature regarding the safety of inhaled tobramycin and discuss potential mechanisms that may promote systemic toxicity in transplant recipients.  相似文献   
15.
16.
In the present study we analysed the dynamics of serum humanchorionic gonadotrophin (HCG) charge isoform distribution throughoutnormal gestation and characterized some of the biological featuresof the several HCG glycoforms present in the circulation ofpregnant women. Blood samples were obtained from normal pregnantwomen at 10–11, 12–15, 23–26 and 35–38weeks of gestation. The sera were fractionated by preparativechromatofocusing and the separated HCG isoforms were identifiedand quantified by radioimmunoassay. The in-vitro biologicalactivity and the plasma half-life of the several circulatingHCG isoforms were determined by conventional methods. HCG isoformsbecame less acidic as pregnancy advanced. In samples taken at10–11 weeks of gestation, the most acidic HCG molecules(pH <3.7) comprised >80% of total HCG recovered afterchromatofocusing; this proportion decreased to 58, 60 and 47%in samples taken from weeks 12.1 to 38.4 of gestation. Meanwhile,the relative proportion of less acidic isoforms recovered withinpH values 6.49–4.50 increased at the end of the firsttrimester (12–15 weeks), remained constant until weeks23–26 and then increased further by the end of the thirdtrimester. Less acidic isoforms had higher in-vitro biologicalpotency per immunological unit than the more acidic analogues.Regardless of the trimester of pregnancy, the plasma half-lifeof the highly acidic (elution pH <3.7) isoforms varied from84.4 to 150 min (116.3 ± 23.0; mean ± SD), whereasthe corresponding half-life of mid-acidic (pH 4.25–5.31)and low-acidic (pH 5.74–6.50) HCG isoforms ranged from31.0 to 115.3 (75.5 ± 20.6) and 15.3 to 58.3 (41.2 ±14.3) min respectively (P <0.01, highly acidic versus mid-and low-acidic analogues and mid-acidic versus least acidicisoforms). The overall data indicate that the human trophoblastis able to regulate the exact intensity, biochemical compositionand duration of the gonadotrophic stimulus secreted during thecourse of normal gestation. They also suggest that the decreaseand maintenance of low serum HCG concentrations during the secondand third trimesters of gestation may be partially caused bychanges in the carbohydrate structure of the HCG molecule charge isoforms/human chorionic gonadotrophin/pregnancy  相似文献   
17.
Biochemical markers of nutritional status (albumin, transthyretin, insulin-like growth factor-I and zinc) were measured in slowly growing two- to five-year-old, low-income Parisian children whose weight-for-height or height-for-age z scores (WHZ or HAZ) were between — 1 and — 2 SD of the NCHS median. The results were compared to controls who were matched for age, sex, and ethnic origin with WHZ and HAZ between — 1 and + 2 SD. Mean serum levels of transthyretin, albumin and insulin-like growth factor-I and mean plasma zinc concentrations were significantly lower in the growth-impaired children than in the controls ( p = 0.002, p = 0.006, p = 0.015, and p = 0.035, respectively). While the height-retarded children had low mean serum insulin-like growth factor-I values, the weight-retarded subjects had decreased levels of albumin, transthyretin and zinc when compared to controls. Lower mean levels of nutritional markers in healthy, slowly growing children suggest that inadequate dietary intakes of zinc, protein and/or energy may result in marginal delays in weight and height gains.  相似文献   
18.
BACKGROUND: Equilibration of hemoglobin concentration after transfusion has been estimated to take about 24 hours, but some studies have shown that earlier measurements reflect steady-state values in persons who have not bled recently. This study was aimed at assessing the changes over time in hemoglobin concentration after transfusion in acutely anemic patients because of recent bleeding. STUDY DESIGN AND METHODS: Thirty-two normovolemic patients recovering from an acute bleeding episode who were no longer thought to be bleeding and who received a 2- unit red cell transfusion were studied. At baseline and 15, 30, 60, and 120 minutes and 24 hours after transfusion, hemoglobin concentration and hematocrit values were measured. RESULTS: The administration of 2 units of packed red cells elicited a 24-hour increase of 22.4 +/− 6.8 g per L in hemoglobin concentration. Hemoglobin values were not different at any of the defined posttransfusion times. Hematocrit levels experienced similar changes over time. Agreement between 15-minute and 24-hour values was excellent, as only 6 percent of patients exhibited a clinically significant difference (> 6 g/L) between the hemoglobin measurements. CONCLUSION: Hemoglobin and hematocrit values rapidly equilibrate after transfusion in normovolemic patients who are recovering from an acute bleeding episode. This fact would allow a rapid assessment of the effects of transfusion and of the recurrence of bleeding in patients remaining at risk.  相似文献   
19.
BACKGROUND: Cyclosporin has been shown to facilitate renal vasoconstriction and to have an antinatriuretic effect. The existence of an interference of cyclosporin with the vasodilating properties of endothelium mediated by nitric oxide production could mediate these effects. On the other hand, the infusion of the nitric oxide precursor L-arginine has been shown to induce renal vasodilatation and to facilitate natriuresis in normal volunteers. We have investigated the renal effects of the administration of an infusion of L-arginine in renal transplant patients chronically treated with cyclosporin. To facilitate the analysis of the data the effects of the administration of a similar dose of cyclosporin on renal function during the infusion of a vehicle were also investigated during the administration of a vehicle of L-arginine. DESIGN: Ten male renal transplant patients, chronically treated with cyclosporin and with a stable renal function were studied during 2 consecutive days after the administration of the usual morning dose of cyclosporin. The first day they received an intravenous infusion of vehicle and the second the infusion of graded doses of L-arginine (50, 100, 150 mg/kg/h) during 3 consecutive h. RESULTS: The first day, after cyclosporin administration a significant fall (P < 0.01) was observed in natriuresis and kaliuresis in the absence of changes in renal plasma flow and glomerular filtration rate. After the administration of L-arginine significant (P < 0.01) increases of renal plasma flow, glomerular filtration rate, and natriuresis were seen. The increase in blood levels of cyclosporin after its administration did not differ between days 1 and 2. CONCLUSION: These results indicate that L-arginine facilitates renal vasodilatation and natriuresis in renal transplant patients. Furthermore, the observed increase in sodium excretion could indicate that L-arginine counteracts the antinatriuretic effect of cyclosporin.   相似文献   
20.
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