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   5628篇
  免费   457篇
  国内免费   10篇
耳鼻咽喉   49篇
儿科学   119篇
妇产科学   101篇
基础医学   665篇
口腔科学   67篇
临床医学   754篇
内科学   1150篇
皮肤病学   92篇
神经病学   464篇
特种医学   162篇
外科学   975篇
综合类   43篇
一般理论   3篇
预防医学   490篇
眼科学   86篇
药学   424篇
中国医学   7篇
肿瘤学   444篇
  2023年   57篇
  2022年   37篇
  2021年   284篇
  2020年   180篇
  2019年   243篇
  2018年   269篇
  2017年   190篇
  2016年   165篇
  2015年   250篇
  2014年   256篇
  2013年   364篇
  2012年   461篇
  2011年   490篇
  2010年   236篇
  2009年   164篇
  2008年   291篇
  2007年   278篇
  2006年   298篇
  2005年   216篇
  2004年   206篇
  2003年   185篇
  2002年   156篇
  2001年   80篇
  2000年   64篇
  1999年   62篇
  1998年   23篇
  1997年   24篇
  1996年   27篇
  1995年   30篇
  1994年   12篇
  1993年   19篇
  1992年   44篇
  1991年   41篇
  1990年   41篇
  1989年   33篇
  1988年   28篇
  1987年   27篇
  1986年   24篇
  1985年   32篇
  1984年   27篇
  1983年   12篇
  1979年   15篇
  1978年   9篇
  1974年   11篇
  1973年   13篇
  1971年   13篇
  1970年   12篇
  1968年   14篇
  1967年   8篇
  1966年   13篇
排序方式: 共有6095条查询结果,搜索用时 46 毫秒
1.
Numerous studies showed that postural balance improves through light touch on a stable surface highlighting the importance of haptic information, seemingly downplaying the mechanical contributions of the support. The present study examined the mechanical effects of canes for assisting balance in healthy individuals challenged by standing on a beam. Sixteen participants supported themselves with two canes, one in each hand, and applied minimal, preferred, or maximum force onto the canes. They positioned the canes in the frontal plane or in a tripod configuration. Statistical analysis used a linear mixed model to evaluate the effects on the center of pressure and the center of mass. The canes significantly reduced the variability of the center of pressure and the center of mass to the same level as when standing on the ground. Increasing the exerted force beyond the preferred level yielded no further benefits, although in the preferred force condition, participants exploited the altered mechanics by resting their arms on the canes. The tripod configuration allowed for larger variability of the center of pressure in the task-irrelevant anterior–posterior dimension. High forces had a destabilizing effect on the canes: the displacement of the hand on the cane handle increased with the force. Given this static instability, these results show that using canes can provide not only mechanical benefits but also challenges. From a control perspective, effort can be reduced by resting the arms on the canes and by channeling noise in the task-irrelevant dimensions. However, larger forces exerted onto the canes can also have destabilizing effects and the instability of the canes needs to be counteracted, possibly by arm and shoulder stiffness. Insights into the variety of mechanical effects is important for the design of canes and the instructions of how to use them.  相似文献   
2.
3.
BackgroundProlonged emergency department (ED) wait times could potentially lead to increased morbidity and mortality. While previous work has demonstrated disparities in wait times associated with race, information about the relationship between experiencing homelessness and ED wait times is lacking.ObjectivesThe purpose of this study was to explore the relationship between residence status (undomiciled vs. domiciled) and ED wait times. We hypothesized that being undomiciled would be associated with longer wait times.MethodsWe obtained data from the National Hospital Ambulatory Medical Care Survey from 2014 to 2017. We compared wait times in each triage category using t tests. We used multivariate linear regression to explore associations between residence status and wait times while controlling for other patient- and hospital-level variables.ResultsOn average, undomiciled patients experienced significantly longer mean ED wait times than domiciled patients (53.4 vs. 38.9 min; p < 0.0001). In the multivariate model, undomiciled patients experienced significantly different wait times by 15.5 min (p = 0.0002). Undomiciled patients experienced increasingly longer waits vs. domiciled patients for the emergent and urgent triage categories (+33.5 min, p < 0.0001, and +22.7 min, p < 0.0001, respectively).ConclusionsUndomiciled patients experience longer ED wait times when compared with domiciled patients. This disparity is not explained by undomiciled patients seeking care in the ED for minor illness, because the disparity is more pronounced for urgent and emergent triage categories.  相似文献   
4.
5.
Nephrolithiasis is a common pathology encountered in the primary care and emergency department (ED) setting. In 2009 alone, there were over one million ED visits related to nephrolithiasis Higa et al. (2017) [1]. Emergent treatment options range from non-invasive pain control and patient education to lithotripsy and other invasive urologic procedures depending on stone location and related pathology. Urethral calculi are estimated to represent 0.3% of all urinary stone diseases Verit et al. (2006) [2]. There are very few case reports documenting distal urethral stone removal in the ED. Here we present a case of distal urethral stone impaction and the removal of this stone by ED providers, leading to expedited care and prevention of consultation and possible admission.  相似文献   
6.
7.
Journal of Neuro-Oncology - The most recent cIMPACT-NOW update highlighted the homozygous deletion of the Cyclin Dependent Kinase Inhibitor 2A (CDKN2A) gene as a clinically important molecular...  相似文献   
8.
PurposeAuto-contouring may reduce workload, interobserver variation, and time associated with manual contouring of organs at risk. Manual contouring remains the standard due in part to uncertainty around the time and workload savings after accounting for the review and editing of auto-contours. This preliminary study compares a standard manual contouring workflow with 2 auto-contouring workflows (atlas and deep learning) for contouring the bladder and rectum in patients with prostate cancer.Methods and MaterialsThree contouring workflows were defined based on the initial contour-generation method including manual (MAN), atlas-based auto-contour (ATLAS), and deep-learning auto-contour (DEEP). For each workflow, initial contour generation was retrospectively performed on 15 patients with prostate cancer. Then, radiation oncologists (ROs) edited each contour while blinded to the manner in which the initial contour was generated. Workflows were compared by time (both in initial contour generation and in RO editing), contour similarity, and dosimetric evaluation.ResultsMean durations for initial contour generation were 10.9 min, 1.4 min, and 1.2 min for MAN, DEEP, and ATLAS, respectively. Initial DEEP contours were more geometrically similar to initial MAN contours. Mean durations of the RO editing steps for MAN, DEEP, and ATLAS contours were 4.1 min, 4.7 min, and 10.2 min, respectively. The geometric extent of RO edits was consistently larger for ATLAS contours compared with MAN and DEEP. No differences in clinically relevant dose-volume metrics were observed between workflows.ConclusionAuto-contouring software affords time savings for initial contour generation; however, it is important to also quantify workload changes at the RO editing step. Using deep-learning auto-contouring for bladder and rectum contour generation reduced contouring time without negatively affecting RO editing times, contour geometry, or clinically relevant dose–volume metrics. This work contributes to growing evidence that deep-learning methods are a clinically viable solution for organ-at-risk contouring in radiation therapy.  相似文献   
9.
Because the peroxisome proliferator-activated receptor (PPAR) signaling pathway is involved in development and progression of pancreatic cancer, we investigated associations between genetic variants of the PPAR pathway genes and pancreatic cancer risk by using three published genome-wide association study datasets including 8477 cases and 6946 controls of European ancestry. Expression quantitative trait loci (eQTL) analysis was also performed for correlations between genotypes of the identified genetic variants and messenger RNA (mRNA) expression levels of their genes by using available databases of the 1000 Genomes, TCGA, and GTEx projects. In the single-locus logistic regression analysis, we identified 1141 out of 17 532 significant single-nucleotide polymorphisms (SNPs) in 112 PPAR pathway genes. Further multivariate logistic regression analysis identified three independent, potentially functional loci (rs12947620 in MED1, rs11079651 in PRKCA, and rs34367566 in PRKCB) for pancreatic cancer risk (odds ratio [OR] = 1.11, 95% confidence interval [CI], [1.06-1.17], P = 5.46 × 10−5; OR = 1.10, 95% CI, [1.04-1.15], P = 1.99 × 10−4; and OR = 1.09, 95% CI, [1.04-1.14], P = 3.16 × 10−4, respectively) among 65 SNPs that passed multiple comparison correction by false discovery rate (< 0.2). When risk genotypes of these three SNPs were combined, carriers with 2 to 3 unfavorable genotypes (NUGs) had a higher risk of pancreatic cancer than those with 0 to 1 NUGs. The eQTL analysis showed that rs34367566 A>AG was associated with decreased expression levels of PRKCB mRNA in 373 lymphoblastoid cell lines. Our findings indicate that genetic variants of the PPAR pathway genes, particularly MED1, PRKCA, and PRKCB, may contribute to susceptibility to pancreatic cancer.  相似文献   
10.
For inhalational studies and aerosol exposures to viruses, head-out plethysmography acquisition has been traditionally used for the determination of estimated inhaled dose in anesthetized nonhuman primates prior to or during an aerosol exposure. A pressure drop across a pneumotachograph is measured within a sealed chamber during inspiration/exhalation of the nonhuman primate, generating respiratory values and breathing frequencies. Due to the fluctuation of depth of anesthesia, pre-exposure respiratory values can be variable, leading to less precise and accurate dosing calculations downstream. Although an anesthesia infusion pump may help stabilize the depth of sedation, pumps are difficult to use within a sealed head-out plethysmography chamber. Real-time, head-out plethysmography acquisition could increase precision and accuracy of the measurements, but the bulky equipment needed for head-out plethysmography precludes real-time use inside a Class III biological safety cabinet, where most aerosol exposures occur. However, the respiratory inductive plethysmography (RIP) acquisition method measures the same respiratory parameters by detecting movement of the chest and abdomen during breathing using two elastic bands within the Class III biological safety cabinet. As respiratory values are relayed to a computer for software integration and analysis real-time, adjustment of aerosol exposure duration is based on the depth of sedation of the animal. The objective of this study was to compare values obtained using two methodologies (pre-exposure head-out plethysmography and real-time RIP). Transitioning to RIP technology with real-time acquisition provides more consistent, precise, and accurate aerosol dosing by reducing reported errors in respiratory values from anesthesia variability when using pre-exposure head-out plethysmography acquisition.  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