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   17624篇
  免费   1491篇
  国内免费   28篇
耳鼻咽喉   245篇
儿科学   537篇
妇产科学   402篇
基础医学   2208篇
口腔科学   268篇
临床医学   2314篇
内科学   3413篇
皮肤病学   264篇
神经病学   1542篇
特种医学   443篇
外国民族医学   2篇
外科学   2240篇
综合类   272篇
一般理论   17篇
预防医学   2329篇
眼科学   430篇
药学   1032篇
中国医学   16篇
肿瘤学   1169篇
  2023年   166篇
  2022年   278篇
  2021年   620篇
  2020年   355篇
  2019年   543篇
  2018年   539篇
  2017年   401篇
  2016年   446篇
  2015年   486篇
  2014年   667篇
  2013年   873篇
  2012年   1253篇
  2011年   1207篇
  2010年   626篇
  2009年   577篇
  2008年   944篇
  2007年   907篇
  2006年   806篇
  2005年   849篇
  2004年   714篇
  2003年   659篇
  2002年   564篇
  2001年   321篇
  2000年   298篇
  1999年   302篇
  1998年   155篇
  1997年   118篇
  1996年   111篇
  1995年   100篇
  1994年   101篇
  1993年   90篇
  1992年   194篇
  1991年   179篇
  1990年   220篇
  1989年   172篇
  1988年   161篇
  1987年   164篇
  1986年   143篇
  1985年   148篇
  1984年   109篇
  1983年   102篇
  1982年   78篇
  1979年   102篇
  1978年   88篇
  1977年   71篇
  1976年   71篇
  1974年   81篇
  1973年   101篇
  1972年   76篇
  1969年   77篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
OBJECTIVE: To characterize dysfunctional labors that lead to cesarean delivery in the second stage and to assess the accuracy of diagnoses of abnormal fetal descent. METHODS: Thirty-one patients delivered by cesarean during the second stage because of abnormal labor or presumed cephalopelvic disproportion were studied and compared to 62 control cesarean cases delivered for the same indications in the first stage. The clinical diagnosis of dysfunctional labor that led to the cesarean was compared to the diagnosis made by retrospective analysis of the labor curves. RESULTS: Cases did not differ from controls delivered in the first stage in maternal age, race, parity, gestational age, weight gain, or the frequency of associated medical complications. The newborns were not significantly different in birth weight,ponderal index, sex, or the incidence of low Apgar scores. Among study patients, 94% had a second stage labor dysfunction determined by graphic labor analysis, predominantly arrest of descent (69%) and failure of descent (28%). In 79% of cases a dysfunctional first stage preceded the abnormal second stage. Among these first stage labor abnormalities, 68% were not recognized during the labor. CONCLUSION: Characteristics of patients delivered by cesarean during the second stage were similar to those delivered before full cervical dilatation. Second stage labor abnormalities were usually preceded by an abnormal first stage. There was considerable inaccuracy in the diagnosis of second stage labor dysfunction.  相似文献   
22.
23.
24.
This study was designed to describe the course of epilepsy (in terms of seizure frequency) and to assess the variables (antiepileptic therapy regimens and others) correlated to improvement. Seizure frequency (categories: seizure free, more than one seizure/year, monthly seizures, weekly seizures and daily seizures) and antiepileptic medication were retrospectively compared between 1992 and 2002 in a large cohort of 550 inpatients with chronic epilepsy and different degrees of intellectual disability or multiple handicaps. RESULTS: Seizure frequency decreased significantly (p<0.001). 218 of the 394 patients (55.3%) not seizure free in 1992 improved (changed into a better frequency category). The improvement rate was marginally higher in patients who had undergone a medication change (p=0.08). A high seizure frequency in 1992 (p=0.016) and older age (p=0.006), but not epilepsy syndrome or degree of intellectual disability, were predictors for improvement (stepwise logistic regression analysis). 56.4% of the improved patients were on combinations of two AEDs (17.4%, monotherapy; 20.2%, triple therapy). The most frequent therapy regimens in the improved patients were lamotrigine/valproate (48 patients), carbamazepine/phenobarbital (21) and carbamazepine only (19). Lamotrigine/valproate was effective in all kinds of epileptic syndromes. Most patients on lamotrigine had serum concentrations above 10microg/ml, approximately one half had dosages above 200mg/day. The rate of seizure freedom increased from 28.4 to 37.6%. The 84% of the patients seizure free in 1992 remained seizure free. Predictors for seizure freedom in 2002 were higher age (stepwise logistic regression, p<0.0005) and seizure freedom in 1992 (p<0.0005). CONCLUSIONS: Substantial improvement can be achieved even in intellectually disabled patients with chronic epilepsy. Although the rate of seizure freedom is reduced in comparison with a non-ID population, once seizure freedom has been achieved it is most likely to continue. For a majority of this patient population, monotherapy may not be sufficient. Lamotrigine/valproate appears to be a major therapeutic innovation.  相似文献   
25.
The interpretation of the total phenytoin (PT) concentration can be problematic if valproic acid (VPA) is given as a comedication, because VPA displaces PT from the protein binding sites and can increase the free fraction of PT. In order to estimate the free or unbound PT concentration (PTf) from the total PT concentration (PTt) and VPA concentration, a nomogram was constructed and evaluated. Data of 84 patients on combined therapy with PT and VPA were used in drawing up the regression equation (PTf = 0.0792.PTt + 0.000636.PTt.VPA) from which the nomogram was constructed. The predictions were checked using another 33 patients whose serum concentrations were determined in the morning and in addition several times during the day. The results show that using this method the PTf concentrations can be accurately estimated from the PTt and VPA concentrations.  相似文献   
26.
In recent years, epidemiologic and clinical studies, public and regulatory policy activity, and media coverage have focused on issues related to trans fats. To help increase awareness and understanding of trans fats and other fats, the American Heart Association (AHA) launched the “Face the Fats” national consumer education campaign in April 2007. The AHA commissioned a quantitative tracking survey between 2006 and 2007 to measure changes in consumer awareness, knowledge, and behaviors related fats and oils and their perceived impact on heart disease. The survey was conducted by Cogent Research. Data were collected during March 2006 and May 2007. At both time points, the survey included a representative sample of the American population age 18 to 65 years (n=1,000). The sampling plan for the survey was designed based on the 2000 and 2003 US Census. The margin of error was ±3.10 percentage points. Awareness of trans fats increased during the 1-year study period. In 2007, 92% of respondents were aware of trans fats, an increase from 84% in 2006 (P<0.05). The 2007 level was similar to the awareness of saturated fats (93%). Perceptions that certain fats and oils heighten the risk of heart disease increased for trans fats (73% in 2007 vs 63% in 2006; P<0.05), saturated fats (77% in 2007 vs 73% in 2006; P<0.05), and partially hydrogenated oils (56% in 2007 vs 49% in 2006; P<0.05). Knowledge about food sources of different fats remained low. On an unaided basis, 21% could name three food sources of trans fats in 2007, up from 17% in 2006 (P<0.05). Knowledge of food sources of saturated fat remained unchanged at 30% in 2007. Significantly more respondents in 2007 reported behavioral changes related to trans fat information, such as buying food products because they show “zero trans fat” on labels or packages (37% in 2007 vs. 32% in 2006; P<0.05). Between 2006 and 2007, consumer awareness about trans fats increased and attained awareness levels similar to saturated fats. The increased awareness is associated with improved self-reported behaviors in grocery shopping. Nonetheless, overall knowledge, especially regarding food sources of saturated and trans fats, remains relatively low, underscoring the need for heightened consumer education activities. The positive change in consumer awareness about trans fats is likely attributable to the wide range of messages available to them, including the AHA “Face the Fats” national consumer education campaign.  相似文献   
27.
Evaluation of students undertaking fieldwork education placements is a critical process in the health professions. As training programs and practice evolve, systems for assessing students need to be reviewed and updated constantly. In 1995, staff of the occupational therapy training program at the University of Queensland, Australia decided to develop a new tool for assessing student fieldwork performance. Using an action research methodology, a team developed the Student Placement Evaluation Form, a flexible and comprehensive criterion-referenced evaluation tool. The present paper examines action research as an appropriate methodology for considering real-life organisational problems in a systematic and participatory manner. The action research cycles undertaken, including preliminary information gathering, tool development, trial stages and current use of the tool, are detailed in the report. Current and future development of the tool is also described.  相似文献   
28.
Exhaled nitric oxide (FENO) is raised in atopy. The mechanism for this is unclear. The aim of this study was to investigate whether the number of AAT repeats in intron 20 of the NOS1 gene, recently associated with variations in FENO in adults with asthma and cystic fibrosis, was associated with the raised FENO in healthy atopic children. Eighty-seven healthy children (44 girls, 42 atopic, age range 6–18 years) underwent measurements of FENO, spirometry, airway responsiveness and skin prick testing. Genotyping was carried out to determine the number of AAT repeats. There was no association between the number of AAT repeats and FENO in either the whole sample of healthy children (n = 87) or in the subsample of healthy atopics (n = 42). However, a greater number of atopic children had two high repeat alleles compared with non-atopic children (33.3% vs. 13.6%, respectively, p = 0.03). This suggests that variations in the NOS1 gene may contribute to atopy without this relationship being reflected by FENO.  相似文献   
29.
The effect of prolonged, 22 h long, intracerebroventricular (i.c.v.) infusion of corticotropin-releasing hormone (CRF) on plasma cortisol, corticosterone and electrolyte concentrations, mean arterial blood pressure (MAP) and heart rate (HR) were investigated in conscious rabbits. During i.c.v. infusion of CRF, 1 and 3 μ/h, at a rate of 17 μl/h, plasma cortisol and corticosterone concentrations rose to the level noted after ACTH stimulation in rabbits. Plasma [Na] did not change, but plasma [K] was reduced and plasma osmolality increased during the infusion of CRF, 3 μ/h. MAP and HR, recorded continuously during i.c.v. infusion of CRF, changed only with the higher dose of CRF: MAP was elevated during the first 5 h of infusion, and then returned to the control level. HR was lower than control at the end of the first hour of infusion and again between 9 and 15 h of infusion. The prolonged rise of CRF concentration in the brain induced a sustained rise in circulating adrenal steroid hormones. MAP did not increase to the level noted after bolus i.c.v. injection of CRF and the rise in MAP was not sustained.  相似文献   
30.
Study Objective . To investigate the effect of simultaneously administered didanosine (ddI) on the absorption of a single dose of itraconazole. Design . Randomized, crossover, unblinded single-dose pharmacokinetic study in healthy volunteers. Comparisons of itraconazole alone and itraconazole with simultaneous ddI were performed on days 1 and 15. Setting . A university medical center. Patients . Seven healthy men and women. Six subjects (86%) completed the study; one was removed due to the development of a rash. Interventions . Volunteers received a single 200-mg oral dose of itraconazole or itraconazole with concomitant oral ddI 300 mg (two 150-mg tablets) dispersed in 240 ml water. Each regimen was separated by a 2-week washout period. Serum samples were obtained frequently for 12 hours after the dose. Measurements and Main Results . Concentrations of itraconazole were determined using a microbiologic assay. Individual concentrations in serum versus time data were evaluated by linear regression analysis. Peak serum concentration and time to peak were determined by visual inspection of each individual's serum concentration-time curve. A mean ± SD peak serum itraconazole concentration of 0.90 ± 0.30 μg/ml was observed at 3.0 ± 0.7 hours when itraconazole was administered alone, compared with undetectable levels in all patients during therapy with ddI. Conclusions . Simultaneous oral administration of ddI significantly decreases absorption of itraconazole. These drugs should not be administered concurrently.  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