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   4301篇
  免费   364篇
  国内免费   7篇
耳鼻咽喉   79篇
儿科学   132篇
妇产科学   45篇
基础医学   621篇
口腔科学   62篇
临床医学   504篇
内科学   728篇
皮肤病学   60篇
神经病学   512篇
特种医学   154篇
外国民族医学   1篇
外科学   708篇
综合类   27篇
一般理论   2篇
预防医学   342篇
眼科学   99篇
药学   277篇
中国医学   5篇
肿瘤学   314篇
  2024年   14篇
  2023年   76篇
  2022年   111篇
  2021年   245篇
  2020年   147篇
  2019年   217篇
  2018年   242篇
  2017年   170篇
  2016年   171篇
  2015年   197篇
  2014年   241篇
  2013年   267篇
  2012年   368篇
  2011年   362篇
  2010年   192篇
  2009年   164篇
  2008年   239篇
  2007年   215篇
  2006年   184篇
  2005年   122篇
  2004年   133篇
  2003年   88篇
  2002年   79篇
  2001年   21篇
  2000年   28篇
  1999年   17篇
  1998年   12篇
  1997年   13篇
  1996年   10篇
  1995年   12篇
  1994年   8篇
  1993年   6篇
  1992年   25篇
  1991年   34篇
  1990年   19篇
  1989年   16篇
  1988年   23篇
  1987年   16篇
  1986年   17篇
  1985年   25篇
  1984年   18篇
  1983年   15篇
  1982年   13篇
  1981年   12篇
  1979年   9篇
  1974年   5篇
  1973年   6篇
  1972年   5篇
  1971年   6篇
  1969年   5篇
排序方式: 共有4672条查询结果,搜索用时 12 毫秒
991.
ABSTRACT

Emergency contraceptive (EC) pills may be less effective for women with higher body mass index (BMI), but little is known about public response to the fact that EC may lose efficacy as weight increases. In November 2013, European authorities changed the label for a levonorgestrel EC product to warn of a reduction in effectiveness for women with higher BMI, garnering significant media coverage in the United States. Ulipristal acetate (UPA) EC may be more effective than levonorgestrel for women with BMI levels designated as obese. Among 8,019 women who received UPA from the online pharmacy KwikMed from 2011 to 2015 and self-reported their height, weight and reasons for seeking UPA online, we analyzed changes in the proportion of women in different BMI categories before and after the label change. For the 25 month-period after the label change, the proportion of women in the obese category rose by 26.7 percentage points relative to the 35 months before (B = 0.2665, p < .01). Mean BMI (25.5 versus 29.4, p < .001) and average weight (148.6 pounds versus 175.5 pounds, p < .001) of users were higher after the label change. Some women appear to have acted on the information that EC efficacy may be associated with body weight.  相似文献   
992.
993.
994.
Background: Common genetic variation in the arsenic methyltransferase (AS3MT) gene region is known to be associated with arsenic metabolism efficiency (AME), measured as the percentage of dimethylarsinic acid (DMA%) in the urine. Rare, protein-altering variants in AS3MT could have even larger effects on AME, but their contribution to AME has not been investigated.Objectives: We estimated the impact of rare, protein-coding variation in AS3MT on AME using a multi-population approach to facilitate the discovery of population-specific and shared causal rare variants.Methods: We generated targeted DNA sequencing data for the coding regions of AS3MT for three arsenic-exposed cohorts with existing data on arsenic species measured in urine: Health Effects of Arsenic Longitudinal Study (HEALS, n=2,434), Strong Heart Study (SHS, n=868), and New Hampshire Skin Cancer Study (NHSCS, n=666). We assessed the collective effects of rare (allele frequency <1%), protein-altering AS3MT variants on DMA%, using multiple approaches, including a test of the association between rare allele carrier status (yes/no) and DMA% using linear regression (adjusted for common variants in 10q24.32 region, age, sex, and population structure).Results: We identified 23 carriers of rare-protein-altering AS3MT variant across all cohorts (13 in HEALS and 5 in both SHS and NHSCS), including 6 carriers of predicted loss-of-function variants. DMA% was 6–10% lower in carriers compared with noncarriers in HEALS [β=9.4 (95% CI: 13.9, 4.8)], SHS [β=6.9 (95% CI: 13.6, 0.2)], and NHSCS [β=8.7 (95% CI: 15.6, 2.2)]. In meta-analyses across cohorts, DMA% was 8.7% lower in carriers [β=8.7 (95% CI: 11.9, 5.4)].Discussion: Rare, protein-altering variants in AS3MT were associated with lower mean DMA%, an indicator of reduced AME. Although a small percentage of the population (0.5–0.7%) carry these variants, they are associated with a 6–10% decrease in DMA% that is consistent across multiple ancestral and environmental backgrounds. https://doi.org/10.1289/EHP8152  相似文献   
995.

Purpose

External beam radiation therapy (EBRT) with low-dose-rate (LDR) brachytherapy boost has been associated with improved biochemical progression–free survival and overall survival (OS) compared with dose-escalated EBRT (DE-EBRT) alone for unfavorable-risk prostate cancer. However, it is not known whether high-dose-rate (HDR) boost provides a similar benefit. We compare HDR boost against LDR boost and DE-EBRT with respect to OS.

Methods

Using the National Cancer Database, we identified 122,896 patients who were diagnosed with National Comprehensive Cancer Network intermediate- or high-risk prostate cancer between 2004 and 2014 and treated with DE-EBRT (75.6–86.4 Gy), LDR boost, or HDR boost. We compared the OS among the three groups using multivariable Cox proportional hazards regression. Inverse probability treatment weighting was used to adjust for covariate imbalance.

Results

On multivariable Cox proportional hazards regression, HDR boost was associated with a similar OS to LDR boost (adjusted hazard ratio [AHR] 1.03 [0.96, 1.11]; p = 0.38) but significantly better OS than DE-EBRT (AHR 1.36 [1.29, 1.44]; p < 0.001). Inverse probability treatment weighting analysis yielded similar results. There was no significant difference between LDR and HDR boosts for National Comprehensive Cancer Network intermediate-risk (AHR 1.05 [0.96, 1.15]; p = 0.32) and high-risk (AHR 1.00 [0.89, 1.12]; p = 0.98) subgroups (p-interaction = 0.55).

Conclusions

Our results suggest that HDR brachytherapy boost yields similar OS benefits compared with LDR brachytherapy boost for unfavorable-risk prostate cancer. HDR boost may be a suitable alternative to LDR boost.  相似文献   
996.
Rumination syndrome is the non-purposeful regurgitation of recently ingested food from the stomach to the mouth, where it is either expelled or reswallowed. Adolescent rumination syndrome (ARS) is a rare condition of which many physicians are unaware. Patients often are misdiagnosed or undergo costly testing, and as a result, diagnosis and treatment are often delayed. While ARS is not life-threatening, it does have medical and emotional effects on the patient and the patient’s family. Diagnosis of ARS is based upon the Rome III diagnostic criteria. Antroduodenal manometry, while not required for a diagnosis, can be helpful to confirm the diagnosis. The pathogenesis of this disorder is complex and not well understood. However, because of its behavioral component, treatment of ARS requires a multidisciplinary approach that includes both medical management of symptoms and implementation of strategies that address behavioral, psychological, and general quality-of-life components of the disorder.  相似文献   
997.
998.
Lev's Syndrome is a rare, progressive cardiac conduction defect (PCCD) due to myocardial fibrosis first described by Maurice Lev in 1964. This condition, proposed to start in the fourth decade of life, involves a sclerotic fibro-fatty degeneration of the Bundle of His and Purkinje fibers, which Lev proposed caused increasing AV delay with age. With the prevalence of electrocardiogram (ECG) use in the emergency department (ED) for cardiac- and non-cardiac complaints, dysrhythmias can be incidentally found and confuse diagnosis and disposition. We highlight the case of an 84-year-old male who presented to the ED for acute onset of diffuse facial paresthesias with elevated blood pressure at home and was found to be significantly bradycardic on initial evaluation. On serial ECGs, the conduction rhythm changed from an initial new first-degree atrioventricular (AV) block with left bundle branch block (LBBB), to a later first-degree AV block without LBBB. Cardiology was consulted. Serial ECGs demonstrated an evolving conduction block arrhythmia consistent with Lev's Syndrome. Here we describe a case of symptomatic bradycardia found to be consistent with Lev's Syndrome.  相似文献   
999.
Diisocyanates (dNCOs) used in industrial applications are well known low molecular weight allergens. Occupational exposure is associated with adverse health outcomes including allergic sensitization and occupational asthma. In this study, we report the production and initial characterization of a dNCO-hapten specific murine IgM monoclonal antibody (mAb). Female BALB/c mice were immunized intraperitoneally with 25 μg of 4,4′-methylene diphenyl diisocyanate (MDI)-keyhole limpet hemocyanin. Following six biweekly booster immunizations, splenocytes were recovered and fused to Sp2/0-Ag14 murine myeloma cell line for hybridoma production. Hybridomas were then screened in a solid-phase indirect enzyme-linked immunosorbent assay (ELISA) against 40:1 4,4′-MDI– human serum albumin (HSA). mAb reactivity to dNCO-HSA conjugates and dNCO-HSA spiked human serum were characterized using a sandwich ELISA. One hybridoma produced a multimeric IgM mAb (15D4) that reacted with 4,4′-MDI-HSA. Sandwich ELISA analysis demonstrated comparable reactivity with other occupationally relevant dNCO-HSA adducts, including 2,4-toluene diisocyanate (TDI)-HSA, 2,6-TDI-HSA, and 1,6-hexamethylene diisocyanate (HDI)-HSA, but not other electrophilic chemical HSA conjugates. The limit of quantification (LOQ) of 4,4′-MDI-HSA, 2,4-TDI-HSA, 2,6-TDI-HSA, and 1,6-HDI-HSA sandwich ELISAs were 567.2, 172.7, 184.2, and 403.5 ng/mL (8.67, 2.60, 2.77, and 6.07 pmol/mL), respectively. In contrast, experiments using dNCO-supplemented human sera showed an increase in the detectable limit of the assay. A mAb has been produced that has potential utility for detecting mixed diisocyanate exposures in occupational environments. The mAb may have additional utility in the standardization of specific IgE detection immunoassays as well as chromatographic-mass spectrometric methods to enrich dNCO adducted HSA in the plasma of occupationally exposed workers.  相似文献   
1000.
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