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   9281篇
  免费   701篇
  国内免费   20篇
耳鼻咽喉   90篇
儿科学   286篇
妇产科学   174篇
基础医学   1176篇
口腔科学   127篇
临床医学   1311篇
内科学   1865篇
皮肤病学   134篇
神经病学   773篇
特种医学   247篇
外科学   1026篇
综合类   122篇
一般理论   4篇
预防医学   1143篇
眼科学   89篇
药学   571篇
中国医学   3篇
肿瘤学   861篇
  2023年   74篇
  2022年   78篇
  2021年   281篇
  2020年   142篇
  2019年   229篇
  2018年   249篇
  2017年   180篇
  2016年   194篇
  2015年   197篇
  2014年   272篇
  2013年   425篇
  2012年   629篇
  2011年   636篇
  2010年   331篇
  2009年   350篇
  2008年   518篇
  2007年   584篇
  2006年   575篇
  2005年   573篇
  2004年   516篇
  2003年   455篇
  2002年   423篇
  2001年   173篇
  2000年   167篇
  1999年   139篇
  1998年   89篇
  1997年   75篇
  1996年   85篇
  1995年   76篇
  1994年   62篇
  1993年   70篇
  1992年   91篇
  1991年   75篇
  1990年   89篇
  1989年   70篇
  1988年   82篇
  1987年   67篇
  1986年   58篇
  1985年   55篇
  1984年   64篇
  1983年   53篇
  1982年   36篇
  1981年   34篇
  1980年   24篇
  1979年   48篇
  1978年   28篇
  1977年   28篇
  1976年   23篇
  1975年   22篇
  1971年   19篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Tau protein is a major component of paired helical filaments (PHFs) which constitute the characteristic neurofibrillary tangle lesions observed in Alzheimer's disease. Two tau mAbs have been produced which show distinct patterns of immunoreactivity with intact human tau and with tau incorporated in PHFs. The mAb 423 recognises PHFs but not human tau on immunoblots whereas mAb 7/51 reacts with human tau but its epitope is buried within the PHF and is only exposed after formic acid treatment. A competitive ELISA has been developed for both of these mAbs and these have been used to quantify the two distinct tau epitopes in PHFs. Samples containing antigen are incubated with horseradish peroxidase-conjugated mAb at 4 degrees C for 16 h and non-adsorbed antibody then measured by binding, at 37 degrees C for 1 h, to a fragment of tau coated on microtitre plates. Bound enzyme-labelled antibody is measured kinetically using a spectrophotometer capable of automatically mixing the samples throughout a 2-min incubation with substrate and chromogen. The interfacing of the plate reader with a computer permits competitive curves to be plotted automatically using Softmax. Curves are fitted using a 4-parameter logistic algorithm which allows one to determine the relative immunoreactivity for different samples. The application of these assays to monitoring biochemical fractions and quantifying distinct immunochemical presentations of tau protein with these two mAbs is described.  相似文献   
82.
Based upon differences in open field and conflict behaviors, the MR/Har and MNRA/Har rat strains have been proposed as a genetically-based "animal model" for the study of emotionality and/or anxiety. The present study compared the MR/Har and MNRA/Har rat strains in the Defensive Burying paradigm. Prior to testing, female MR/Har and MNRA/Har rats were placed in a 40 X 30 X 40 cm Plexiglas chamber containing clay bedding material (5 cm deep) for 30 minute periods on each of four consecutive days. On the fifth day, a wire wrapped prod was placed at one end of the chamber. Rats were placed in the chamber singly and a 3 mA shock was delivered upon contact with the prod. Defensive Burying behavior (i.e., the moving of bedding material toward or over the prod) was recorded for each animal for 15 minutes postshock. There was no MR/Har versus MNRA/Har difference in the percent of animals exhibiting Defensive Burying, nor was there a MR/Har versus MNRA/Har difference in the latency to initiation or the duration of this behavior. Thus, these genetically-defined Maudsley rat strains do not appear to differ in all "animal models" for the study of anxiety or fear.  相似文献   
83.
Family history is the major risk factor in the aetiology of breast cancer. Breast screening is currently available to women from the age of 50 to 64 through the National Breast Screening Programme. There is, however, an equivalent risk of developing breast cancer below 50 for first degree relatives of women diagnosed with breast cancer premenopausally. We have estimated the risk of breast cancer for relatives of women affected at different ages and used these to establish a family cancer clinic offering breast screening based on individual risk. In three years we have seen 851 patients. Compliance for annual radiology was in excess of 83% over this period and of five cancers detected one had a lump at presentation, two developed interval breast lumps, and two were asymptomatic.  相似文献   
84.
Fifty-four patients with chronic progressive multiple sclerosis received prednisone plus oral low-dose cyclophosphamide and either true plasmapheresis (PP) or "sham" PP weekly for 20 weeks in a double-blind controlled study. Immunosuppressive drug therapy alone (sham PP group, n = 29) was associated with improvement (greater than or equal to one step in Kurtzke Disability Status Scale [DSS]; mean change of 1.5) in 8 and stabilization of MS in 18 patients, with this status sustained in 23 patients at follow-up, 11 months after entry. In contrast, 14 of 26 patients who received "true" PP improved (greater than or equal to one step in DSS; mean change of 2.6), and 11 more were stable, with these changes sustained in 23 of 26 patients at follow-up. These differences, overall, between the PP and sham PP groups were significant at p less than 0.007.  相似文献   
85.
Journal of Public Health - Each year, about 48 million people in the United States are affected by foodborne illnesses, with approximately 3000 of these cases resulting in death. In Texas, the...  相似文献   
86.
BackgroundChildren with intellectual disability (ID), characterized by impairments in intellectual functioning and adaptive behavior, benefit from early identification and access to services. Previous U.S. estimates used administrative data or parent report with limited information for demographic subgroups.ObjectiveUsing empiric measures we examined ID characteristics among 8-year-old children and estimated prevalence by sex, race/ethnicity, geographic area and socioeconomic status (SES) area indicators.MethodsWe analyzed data for 8-year-old children in 9 geographic areas participating in the 2014 Autism and Developmental Disabilities Monitoring Network. Children with ID were identified through record review of IQ test data. Census and American Community Survey data were used to estimate the denominator.ResultsOverall, 11.8 per 1,000 (1.2%) had ID (IQ ≤ 70), of whom 39% (n = 998) also had autism spectrum disorder. Among children with ID, 1,823 had adaptive behavior test scores for which 64% were characterized as impaired. ID prevalence per 1,000 was 15.8 (95% confidence interval [95% CI], 15.0–16.5) among males and 7.7 (95% CI, 7.2–8.2) among females. ID prevalence was 17.7 (95% CI, 16.6–18.9) among children who were non-Hispanic black; 12.0 (95% CI, 11.1–13.0), among Hispanic; 8.6 (95% CI, 7.1–10.4), among non-Hispanic Asian; and 8.0 (95% CI, 7.5–8.6), among non-Hispanic white. Prevalence varied across geographic areas and was inversely associated with SES.ConclusionsID prevalence varied substantively among racial, ethnic, geographic, and SES groups. Results can inform strategies to enhance identification and improve access to services particularly for children who are minorities or living in areas with lower SES.  相似文献   
87.
88.
The coronavirus disease pandemic has highlighted the key role epidemiologic models play in supporting public health decision-making. In particular, these models provide estimates of outbreak potential when data are scarce and decision-making is critical and urgent. We document the integrated modeling response used in the US state of Utah early in the coronavirus disease pandemic, which brought together a diverse set of technical experts and public health and healthcare officials and led to an evidence-based response to the pandemic. We describe how we adapted a standard epidemiologic model; harmonized the outputs across modeling groups; and maintained a constant dialogue with policymakers at multiple levels of government to produce timely, evidence-based, and coordinated public health recommendations and interventions during the first wave of the pandemic. This framework continues to support the state’s response to ongoing outbreaks and can be applied in other settings to address unique public health challenges.  相似文献   
89.
BackgroundTotal joint arthroplasty is the most common elective orthopedic procedure in the Veterans Affairs hospital system. In 2019, physical medicine and rehabilitation began screening patients before surgery to select candidates for direct transfer to acute rehab after surgery. The primary outcome of this study was to demonstrate that the accelerated program was successful in decreasing inpatient costs and length of stay (LOS). The secondary outcome was to show that there was no increase in complication, reoperation, and readmission rates.MethodsA retrospective review of total joint arthroplasty patients was conducted with three cohorts: 1) control (n = 193), 2) transfer to rehab orders on postop day #1 (n = 178), and 3) direct transfers to rehab (n = 173). To assess for demographic disparities between cohorts, multiple analysis of variance tests followed by a Bonferroni P-value correction were used. Differences between test groups regarding primary outcomes were assessed with analysis of variance tests followed by pairwise t-tests with Bonferroni P-value corrections.ResultsThere were no significant differences between the cohort demographics or comorbidities. The mean total LOS decreased from 7.0 days in the first cohort, to 6.9 in the second, and 6.0 in the third (P = .00034). The mean decrease in cost per patient was $14,006 between cohorts 1 and 3, equating to over $5.6 million in savings annually. There was no significant change in preintervention and postintervention short-term complications (P = .295).ConclusionsSignificant cost savings and decrease in total LOS was observed. In the current health care climate focused on value-based care, a similar intervention could be applied nationwide to improve Veterans Affair services.  相似文献   
90.
BackgroundAlthough frailty has been shown to be associated with adverse outcomes in patients undergoing total hip arthroplasty (THA) and total knee arthroplasty (TKA), prior studies have not examined how race/ethnicity might moderate these associations. We aimed to assess race/ethnicity as a potential moderator of the associations of frailty and functional status with arthroplasty outcomes.MethodsThe National Surgical Quality Improvement Program was queried for patients who underwent THA or TKA from 2011 to 2017. Frailty was assessed using the modified frailty index. Regression analyses were conducted to examine associations connecting frailty/functional status with 30-day readmission, adverse discharge, and length of stay (LOS). Further analyses were conducted to investigate race/ethnicity as a potential moderator of these relationships.ResultsWe identified 219,143 TKA and 130,022 THA patients. Frailty and nonindependent functional status were positively associated with all outcomes (P < .001). Compared to White non-Hispanic patients, Black non-Hispanic patients had higher odds for all outcomes after TKA (P < .001) and for adverse discharge/longer LOS after THA (P < .001). Similar associations were observed for Hispanics for the adverse discharge/LOS outcomes. Race/ethnicity moderated the effects of frailty in TKA for all outcomes and in THA for adverse discharge/LOS. Race/ethnicity moderated the effects of nonindependent function in TKA for adverse discharge/LOS and on LOS alone for THA.ConclusionDisparities for Black non-Hispanic and Hispanic patients persist for readmission, adverse discharge, and LOS. However, the effects of increasing frailty and nonindependent functional status on these outcomes were the most pronounced among White non-Hispanic patients.  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