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   19953篇
  免费   1274篇
  国内免费   36篇
耳鼻咽喉   120篇
儿科学   687篇
妇产科学   707篇
基础医学   2705篇
口腔科学   273篇
临床医学   3323篇
内科学   3722篇
皮肤病学   203篇
神经病学   1982篇
特种医学   290篇
外科学   1432篇
综合类   248篇
一般理论   31篇
预防医学   2788篇
眼科学   154篇
药学   1244篇
中国医学   13篇
肿瘤学   1341篇
  2023年   87篇
  2022年   141篇
  2021年   331篇
  2020年   212篇
  2019年   374篇
  2018年   387篇
  2017年   279篇
  2016年   356篇
  2015年   404篇
  2014年   602篇
  2013年   963篇
  2012年   1385篇
  2011年   1385篇
  2010年   769篇
  2009年   755篇
  2008年   1355篇
  2007年   1332篇
  2006年   1337篇
  2005年   1370篇
  2004年   1308篇
  2003年   1284篇
  2002年   1241篇
  2001年   150篇
  2000年   138篇
  1999年   172篇
  1998年   253篇
  1997年   219篇
  1996年   183篇
  1995年   196篇
  1994年   173篇
  1993年   165篇
  1992年   142篇
  1991年   127篇
  1990年   114篇
  1989年   112篇
  1988年   112篇
  1987年   111篇
  1986年   80篇
  1985年   83篇
  1984年   120篇
  1983年   92篇
  1982年   126篇
  1981年   105篇
  1980年   109篇
  1979年   62篇
  1978年   66篇
  1977年   45篇
  1976年   51篇
  1975年   36篇
  1974年   46篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
981.
982.
983.
Context  Hormone replacement therapy (HRT) and antioxidant vitamins are widely used for secondary prevention in postmenopausal women with coronary disease, but no clinical trials have demonstrated benefit to support their use. Objective  To determine whether HRT or antioxidant vitamin supplements, alone or in combination, influence the progression of coronary artery disease in postmenopausal women, as measured by serial quantitative coronary angiography. Design, Setting, and Patients  The Women's Angiographic Vitamin and Estrogen (WAVE) Trial, a randomized, double-blind trial of 423 postmenopausal women with at least one 15% to 75% coronary stenosis at baseline coronary angiography. The trial was conducted from July 1997 to January 2002 in 7 clinical centers in the United States and Canada. Interventions  Patients were randomly assigned in a 2 x 2 factorial design to receive either 0.625 mg/d of conjugated equine estrogen (plus 2.5 mg/d of medroxyprogesterone acetate for women who had not had a hysterectomy), or matching placebo, and 400 IU of vitamin E twice daily plus 500 mg of vitamin C twice daily, or placebo. Main Outcome Measure  Annualized mean (SD) change in minimum lumen diameter (MLD) from baseline to concluding angiogram of all qualifying coronary lesions averaged for each patient. Patients with intercurrent death or myocardial infarction (MI) were imputed the worst rank of angiographic outcome. Results  The mean (SD) interval between angiograms was 2.8 (0.9) years. Coronary progression, measured in mean (SD) change, worsened with HRT by 0.047 (0.15) mm/y and by 0.024 (0.15) mm/y with HRT placebo (P = .17); and for antioxidant vitamins by 0.044 (0.15) mm/y and with vitamin placebo by 0.028 (0.15) mm/y (P = .32). When patients with intercurrent death or MI were included, the primary outcome showed an increased risk for women in the active HRT group (P = .045), and suggested an increased risk in the active vitamin group (P = .09). Fourteen patients died in the HRT group and 8 in the HRT placebo group (hazard ratio [HR], 1.8; 95% confidence interval [CI], 0.75-4.3), and 16 in the vitamin group and 6 in the vitamin placebo group (HR, 2.8; 95% CI, 1.1-7.2). Death, nonfatal MI, or stroke occurred in 26 HRT patients vs 15 HRT controls (HR, 1.9; 95% CI, 0.97-3.6) and in 26 vitamin patients and 18 vitamin controls (HR, 1.5; 95% CI, 0.80-2.9). There was no interaction between the 2 treatment interventions. Conclusion  In postmenopausal women with coronary disease, neither HRT nor antioxidant vitamin supplements provide cardiovascular benefit. Instead, a potential for harm was suggested with each treatment.   相似文献   
984.
Sleep loss and fatigue in residency training: a reappraisal   总被引:13,自引:0,他引:13  
Veasey S  Rosen R  Barzansky B  Rosen I  Owens J 《JAMA》2002,288(9):1116-1124
Reduced sleep time is commonplace for many interns and residents. Recent studies, however, suggest that sleep loss and fatigue result in significant neurobehavioral impairments in healthy young adults. We reviewed studies addressing the effects of sleep loss on cognition, performance, and health in surgical and nonsurgical residents. We describe the effectiveness of countermeasures for sleepiness, including recent work-hour restrictions. A more complete understanding of the issues of sleep loss during residency training can inform innovative strategies to minimize the effects of sleepiness and fatigue on patient care and resident safety.   相似文献   
985.
986.
Neuropsychiatric complications of antiretroviral therapy.   总被引:1,自引:0,他引:1  
Neuropsychiatric adverse effects related to potent antiretroviral therapy are among the complications that can lead to poor adherence, treatment interruptions, or change of antiretroviral therapy regimens. For a historical perspective, we review early literature and case reports with CNS adverse effects attributed to antiretrovirals. The variability of the cerebrospinal fluid penetration of individual antiretrovirals may contribute to their potential for behavioural and psychiatric manifestations.The majority of neuropsychiatric complications related to potent antiretroviral therapy have been associated with the use of the efavirenz. Updates on the risk of neuropsychiatric manifestations with efavirenz use in patients with a history of psychiatric disorders or substance abuse are reviewed. We include a critical review of recently published data on the long-term CNS adverse effects with efavirenz. Special attention is given to the results of recent investigations on the relationship between the pharmacogenomics of genes responsible for efavirenz metabolism and the plasma concentration of efavirenz. It is important to note that there is no established direct correlation of efavirenz concentrations and symptoms. It is not recommended for practitioners to adjust efavirenz doses in order to prevent or alleviate CNS adverse effects. Patients may be placed at risk for virological failure and resistance if they receive suboptimal doses of efavirenz. The aim of this article is to give a concise review and an update on recent literature concerning neuropsychiatric effects of antiretroviral use in HIV-infected patients. Our intent is to present practitioners with data that can be used in a practical way to both educate and improve outcomes in the HIV-infected patient population.  相似文献   
987.
The Vaccine Research Center has developed a number of vaccine candidates for different diseases/infectious agents (HIV-1, Severe Acute Respiratory Syndrome virus, West Nile virus, and Ebola virus, plus a plasmid cytokine adjuvant-IL-2/Ig) based on a DNA plasmid vaccine platform. To support the clinical development of each of these vaccine candidates, preclinical studies were performed to screen for potential toxicities (intrinsic and immunotoxicities). All treatment-related toxicities identified in these repeated-dose toxicology studies have been confined primarily to the sites of injection and seem to be the result of both the delivery method (as they are seen in both control and treated animals) and the intended immune response to the vaccine (as they occur with greater frequency and severity in treated animals). Reactogenicity at the site of injection is generally seen to be reversible as the frequency and severity diminished between doses and between the immediate and recovery termination time points. This observation also correlated with the biodistribution data reported in the companion article (Sheets et al., 2006), in which DNA plasmid vaccine was shown to remain at the site of injection, rather than biodistributing widely, and to clear over time. The results of these safety studies have been submitted to the Food and Drug Administration to support the safety of initiating clinical studies with these and related DNA plasmid vaccines. Thus far, standard repeated-dose toxicology studies have not identified any target organs for toxicity (other than the injection site) for our DNA plasmid vaccines at doses up to 8 mg per immunization, regardless of disease indication (i.e., expressed gene-insert) and despite differences (strengths) in the promoters used to drive this expression. As clinical data accumulate with these products, it will be possible to retrospectively compare the safety profiles of the products in the clinic to the results of the repeated-dose toxicology studies, in order to determine the utility of such toxicology studies for signaling potential immunotoxicities or intrinsic toxicities from DNA vaccines. These data build on the biodistribution studies performed (see companion article, Sheets et al., 2006) to demonstrate the safety and suitability for investigational human use of DNA plasmid vaccine candidates for a variety of infectious disease prevention indications.  相似文献   
988.
The absorption, distribution, metabolism, and elimination of [3-14C] 8-2 fluorotelomer alcohol (8-2 FTOH, C7F1514CF2CH2CH2OH) following a single oral dose at 5 and 125 mg/kg in male and female rats have been determined. Following oral dosing, the maximum concentration of 8-2 FTOH in plasma occurred by 1 h postdose and cleared rapidly with a half-life of less than 5 h. The internal dose to 8-2 FTOH, as measured by area under the concentration-time curve to infinity, was similar for male and female rats and was observed to increase in a dose-dependent fashion. The majority of the 14C 8-2 FTOH (> 70%) was excreted in feces, and 37-55% was identified as parent. Less than 4% of the administered dose was excreted in urine, which contained low concentrations of perfluorooctanoate (approximately 1% of total 14C). Metabolites identified in bile were principally composed of glucuronide and glutathione conjugates, and perfluorohexanoate was identified in excreta and plasma, demonstrating the metabolism of the parent FTOH by sequential removal of multiple CF2 groups. At 7 days postdose, 4-7% of the administered radioactivity was present in tissues, and for the majority, 14C concentrations were greater than whole blood with the highest concentration in fat, liver, thyroid, and adrenals. Distribution and excretion of a single 125-mg/kg [3-14C] 8-2 FTOH dermal dose following a 6-h exposure in rats was also determined. The majority of the dermal dose either volatilized from the skin (37%) or was removed by washing (29%). Following a 6-h dermal exposure and a 7-day collection period, excretion of total radioactivity via urine (< 0.1%) and feces (< 0.2%) was minor, and radioactivity concentrations in most tissues were below the limit of detection. Systemic availability of 8-2 FTOH following dermal exposure was negligible.  相似文献   
989.
The Syracuse AUDIT (Assessment of Urban Dwellings for Indoor Toxics) project is a birth cohort study of wheezing in the first year of life in a low-income urban setting. Such studies are important because of the documented serious risks to children's health and the lack of attention and published work on asthma development and intervention in communities of this size. We studied 103 infants of mothers with asthma, living predominantly in inner-city households. Our study combines measurements of a large panel of indoor environmental agents, in-home infant assessments, and review of all prenatal and postnatal medical records through the first year of life. We found multiple environmental pollution sources and potential health risks in study homes including high infant exposure to tobacco smoke. The prevalence of maternal smoking during pregnancy was 54%; postnatal environmental tobacco smoke (ETS) exposure was nearly 90%. The majority (73%) of homes showed signs of dampness. Participants' lives were complicated by poverty, unemployment and single-parenthood. Thirty-three percent of fathers were not involved with their children, and 62% of subjects moved at least once during the study period. These socioeconomic issues had an impact on project implementation and led to modification of study eligibility criteria. Extensive outreach, follow up, and relationship-building were required in order to recruit and retain families and resulted in considerable work overload for study staff. Our experiences implementing the project will inform further studies on this and other similar populations. Future reports on this cohort will address the role of multiple environmental variables and their effects on wheezing outcome during the first year of life.Crawford, Hargrave, Liu, Anbar, Hall, Naishadham, Czerwinski, Webster, Lane, and Abraham are with the Department of Pathology, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA; Hunt is with the UNYSPEC Ltd., Baldwinsville, NY, USA.  相似文献   
990.
OBJECTIVE: To compare the number of surgical site infections (SSIs) registered after hospital discharge with respect to various surgical procedures and to identify the procedures for which postdischarge surveillance (PDS) is most important. DESIGN: Prospective SSI surveillance with voluntary PDS. Recommended methods for PDS in the Dutch national nosocomial surveillance network are addition of a special registration card to the outpatient medical record, on which the surgeon notes clinical symptoms and whether a patient developed an SSI according to the definitions; an alternative method is examination of the outpatient medical record. SETTING: Hospitals participating in the Dutch national nosocomial surveillance network between 1996 and 2004. RESULTS: We collected data on 131,798 surgical procedures performed in 64 of the 98 Dutch hospitals. PDS was performed according to one of the recommended methods for 31,134 operations (24%) and according to another active method for 32,589 operations (25%), and passive PDS was performed for 68,075 operations (52%). Relatively more SSIs were recorded after discharge for cases in which PDS was performed according to a recommended method (43%), compared with cases in which another active PDS method was used (30%) and cases in which passive PDS was used (25%). The highest rate of SSI after discharge was found for appendectomy (79% of operations), followed by knee prosthesis surgery (64%), mastectomy (61%), femoropopliteal or femorotibial bypass (53%), and abdominal hysterectomy (53%). CONCLUSIONS: For certain surgical procedures, most SSIs develop after discharge. SSI rates will be underestimated if no PDS is performed. We believe we have found a feasible and sensitive method for PDS that, if patients routinely return to the hospital for a postdischarge follow-up visit, might be suitable for use internationally.  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