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   15659篇
  免费   1050篇
  国内免费   77篇
耳鼻咽喉   127篇
儿科学   324篇
妇产科学   325篇
基础医学   1906篇
口腔科学   347篇
临床医学   1526篇
内科学   3086篇
皮肤病学   193篇
神经病学   1569篇
特种医学   627篇
外科学   2408篇
综合类   183篇
现状与发展   1篇
一般理论   28篇
预防医学   1347篇
眼科学   520篇
药学   1198篇
中国医学   25篇
肿瘤学   1046篇
  2024年   34篇
  2023年   145篇
  2022年   291篇
  2021年   624篇
  2020年   308篇
  2019年   461篇
  2018年   541篇
  2017年   398篇
  2016年   407篇
  2015年   501篇
  2014年   675篇
  2013年   806篇
  2012年   1302篇
  2011年   1272篇
  2010年   689篇
  2009年   644篇
  2008年   1009篇
  2007年   1011篇
  2006年   954篇
  2005年   961篇
  2004年   820篇
  2003年   741篇
  2002年   673篇
  2001年   125篇
  2000年   73篇
  1999年   103篇
  1998年   129篇
  1997年   100篇
  1996年   87篇
  1995年   75篇
  1994年   59篇
  1993年   52篇
  1992年   57篇
  1991年   44篇
  1990年   45篇
  1989年   44篇
  1988年   35篇
  1987年   34篇
  1986年   25篇
  1985年   21篇
  1984年   34篇
  1983年   29篇
  1982年   26篇
  1981年   35篇
  1980年   32篇
  1978年   17篇
  1977年   14篇
  1976年   16篇
  1975年   12篇
  1974年   12篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Gastrointestinal (GI) infections exert a significant public health burden in the United Kingdom and the numbers of episodes are increasing. Younger children are considered particularly vulnerable to infection, and can experience 2–3 GI infections episodes per year, with consequences being more severe for more disadvantaged children, who are much more likely to be admitted to hospital. Few qualitative studies have explored the lived experience of GI infection in the community in the UK. The aim of the study reported here was to contribute to addressing this evidence gap, by examining the consequences of GI infection for ‘normal’ family life. Eighteen mothers with young children who had recently experienced a gastrointestinal infection were recruited from two socioeconomically contrasting neighbourhoods in North West of England. The findings demonstrated that GI infections were particularly disruptive: experienced as disgusting, laborious and stressful and significantly impacted normal family routines. Women felt burdened by the heavy physical and emotional demands of caring for a GI infection, resulting in feelings of isolation and insufficient support in their caring role from male partners. Tensions also arose from interactions with external community organisations, particularly in complying with their regulations on infection which often undermined caregivers knowledge and expertise of what was best for their children. This study challenges assumptions that managing GI infections in the home is unproblematic and experienced by caregivers as a ‘minor ailment.’ Infection control measures need to incorporate insights gleaned from the day-to-day realities of caring for sick children in the community.  相似文献   
63.
In the past, the diagnosis of growing skull fracture or diastatic fracture has included a subset of injuries better referred to as cranial burst fracture. Cranial burst fracture, typically associated with severe injury in infants less than 1 year of age, is a closed, widely diastatic skull fracture accompanied by acute cerebral extrusion outside the calvarium. We treated 11 such infants at the LeBonheur Children's Medical Center and 2 at the Children's National Medical Center from January 1986 through December 1994. Infants ranged in age from 1 to 17 months, with an average age of 5.7 months. All presented with marked scalp swelling and a Glasgow Coma Scale score of 10 or less. Twelve had a history consistent with severe injury (motor vehicle accident, 7, abuse 5). The cause of injury in one patient remains unproven. Surgery (reduction of herniated cerebral tissue, repair of large dural laceration, and cranioplasty) was usually performed within 10 days of injury, a time period long enough to assure hemodynamic stability and resolution of acute cerebral swelling, yet sufficiently brief to avoid the chronic changes (scarring, parasitization of scalp vessels by damaged cortex) associated with a growing skull fracture. Prompt repair of cranial burst fracture may prevent ongoing brain injury such as has been neuropathologically demonstrated in patients with growing skull fracture. Magnetic resonance imaging establishes the diagnosis of cranial burst fracture in equivocal cases, rendering unnecessary a waiting period to see if scalp swelling resolves. Our experience, together with information in the neuropathological and neurosurgicla literature, suggests that cranial burst fracture is associated with severe trauma, requires expeditious treatment, and has been underdiagnosed in the past, leading to growing skull fracture, a condition requiring more extensive surgery.  相似文献   
64.
Six mainstream and twelve sidestream infrared carbon dioxide (CO2) analysers were tested for accuracy of the CO2 display value, alarm activation and the effects of nitrous oxide (N2O), oxygen (O2) and water vapour according to the ISO Draft International Standard (DIS) #9918. Mainstream analysers (M-type): Novametrix Capnogard 1265; Hewlett Packard HP M1166A (CO2module HP M1016A); Datascope Passport; Marquette Tramscope 12; Nellcor Ultra Cap N-6000; Heilige Vicom-sm SMU 611/612 ETC. Sidestream analysers: Brüel &; Kjaer Type 1304; Datex Capnomac II; Marquette MGA-AS; Datascope Multinex; Ohmeda 4700 OxiCap (all type S1: respiratory cycles not demanded); Biochem BCI 9000; Bruker BCI 9100; Dräger Capnodig and PM 8020; Criticare Poet II; Heilige Vicom-sm SMU 611/612 A-GAS (all type S2: respiratory cycles demanded). The investigations were performed with premixed test gases (2.5, 5, 10 vol%, error ?1% rel.). Humidification (37° C) of gases were generated by a Dräger Aquapor. Respiratory cycles were simulated by manually activated valves. All monitors complied with the tolerated accuracy bias in CO2 reading (≤ 12% or 4 mmHg of actual test gas value) for wet and dry test gases at all concentrations, except that the Marquette MGA-AS exceeded this accuracy limit with wet gases at 5 and 10 vol% CO2. Water condensed in the metal airway adapter of the HP M1166A at 37° C gas temperature but not at 3(P C. The Servomex 2500 (nonclinical reference monitor), Passport (M-type), Multinex (S1-type) and Poet II (S2-type) showed the least bias for dry and wet gases. Nitrous oxide and O2 had practically no effect on the Capnodig and the errors in the others were max. 3.4 mmHg, still within the tolerated bias in the DIS (same as above). The difference between the display reading at alarm activation and the set point was in all monitors (except in the Capnodig: bias 1.75 mmHg at 5 vol% CO2) below the tolerated limit of the DIS (difference ≤ 0.2 vol%). The authors conclude that the tested monitors are safe for clinical use (except those failing the DIS limits). The accuracy of the CO2-reading (average of mean absolute bias) is better in the M-type than in the S1- or S2- type analysers although no statistical (nor clinical) significant differences could be detected. Most manufacturers work with stricter limits than those proposed by the DIS.  相似文献   
65.
66.

Purpose

We assessed the ability of laser induced autofluorescence to differentiate malignant from nonmalignant bladder lesions.

Materials and Methods

We studied 53 patients with bladder cancer undergoing mucosal biopsies or transurethral resection of a bladder tumor. A quartz optical fiber was advanced through the working channel of a cystoscope and placed in gentle contact with the bladder. Tissue fluorescence was excited by 337 nm. light pulses (nitrogen laser). One fiber was used for transmission of the excitation and emission (fluorescence) light. An optical multichannel analyzer system was used to record fluorescence spectra of the sites of interest.

Results

We analyzed the fluorescence spectra of 114 bladder areas (1 carcinoma in situ as well as 28 malignant, 35 inflammatory, 7 dysplastic, 1 squamous metaplastic and 42 normal areas). These lesions included 44 difficult to diagnose suspicious tumors (11 malignant and 33 nonmalignant). We developed an algorithm that used the I385:I455 nm. fluorescence ratio to distinguish malignant from nonmalignant lesions, including inflammatory areas. By analyzing the data on all 114 lesions, we noted the sensitivity, specificity, and positive and negative predictive values of this method for differentiating malignant from nonmalignant bladder lesions to be 97, 98, 93 and 99 percent, respectively.

Conclusions

Under excitation with 337 nm. light a clear differentiation between malignant and nonmalignant bladder tissues can be made using the I385:I455 nm. autofluorescence ratio.  相似文献   
67.
Background: The pharmacokinetic variables of drug clearance and volume of distribution are usually corrected for body weight or surface area. Only recently have the relationships which exist between body size, physiologic function and pharmacokinetic variables been evaluated in the obese population. These effects are not widely known, and data on this and the effects of bariatric surgical procedures are scantily documented in the surgical literature. Methods: Literature review. Results: Drugs with a low or moderate affinity for adipose tissue have a moderate increase in the volume of distribution (Vd), and this correlates with the increase in lean body mass (LBM). Highly lipophilic drugs, with some exceptions, show the expected increase in Vd and prolongation of elimination half-life, indicating a marked distribution into adipose tissue. Drug absorption, in general, is slowed by delayed gastric emptying and is normal when gastric emptying is normal or increased. Most drug absorption occurs in the small intestine where duration of drug/mucosal contact is the most important factor. Conclusions: Drugs whose distribution is restricted to LBM should utilize a loading dose based on ideal body weight (IBW). For those drugs which distribute freely into adipose tissue, the loading dose should be based on total body weight (TBW). Adjustment of the maintenance dose depends on clearance rates. In a few cases dosage adjustment depends on pharmacodynamic data, since drug clearance does not conform to these recommendations, for reasons which remain to be defined. Following bariatric surgery, in the absence of delayed gastric emptying or uncontrolled diarrhea, drug absorption rates are usually comparable to the non-operated patient.  相似文献   
68.
BACKGROUND: No nationally representative data are available regarding use of eye care services by children. OBJECTIVES: To determine the proportion of children who receive specialty eye care and to evaluate the association of such care with age and other factors associated with health care utilization. METHODS: We used the 2000 National Health Interview Survey to estimate the proportion of nonblind children who received eye care in the preceding 12 months. The association between eye care and the factors of interest among children aged 6-17 years was measured through adjusted bivariate comparisons and logistic regression modeling. RESULTS: Eye care was received in the preceding 12 months by an estimated 7.3% (95% confidence interval [CI] 6.0-8.6) of the 22.8 million children aged 0-5 years and 24.8% (95% CI 23.5-26.2) of the 48.5 million children aged 6-17 years. Among children aged 6-17 years, girls had 29% greater odds than boys to have received eye care (P=.001). Among children <200% of the federal poverty level, those with public health insurance had greater odds of receiving eye care than did uninsured children or those with private health insurance (P<.001). Among children >200% of the federal poverty level, uninsured children had lower odds than did children with public or private health insurance (P<.004) to receive eye care. Well-child care was associated with increased eye care utilization among children aged 12-14 years (P<.001). CONCLUSIONS: Receipt of specialty eye care is common and increases with age. However, there are marked variations among school-aged children. Future studies should address the causes and effects of these findings.  相似文献   
69.
70.
The past decade has seen several innovations in the surgical techniques available for treatment of patients with sleep-disordered breathing. Outpatient techniques such as laser-assisted uvulopalatoplasty (LAUP) and more aggressive procedures designed to address hypopharyngeal and base of tongue obstruction (genioglossus advancement and hyoid myotomy) have been developed and proven successful. We describe the efficacy of LAUP for snoring (72.7%), upper airway resistance syndrome (81.8%), and mild (mean[±SD] respiratory disturbance index [RDI] = 12 ± 8.1) obstructive sleep apnea (41.7%) in 56 patients who underwent 132 LAUP procedures in a 26-month period. Thirty-two patients with more significant obstructive sleep apnea (mean RDI = 41.8 ± 23.1) underwent multilevel pharyngeal surgery consisting of genioglossus advancement and hyoid myotomy combined with uvulopalatopharyngoplasty. The surgical success rate in this group of patients was 85.7% when commonly accepted criteria were applied. We recommend a stratified surgical approach to patients with sleep-disordered breathing. Progressively worse airway obstruction marked by multilevel pharyngeal collapse and more severe sleep-disordered breathing is treated with incrementally more aggressive surgery addressing multiple areas of the upper airway.  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