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   3254篇
  免费   302篇
  国内免费   118篇
耳鼻咽喉   14篇
儿科学   55篇
妇产科学   31篇
基础医学   395篇
口腔科学   107篇
临床医学   637篇
内科学   523篇
皮肤病学   6篇
神经病学   259篇
特种医学   236篇
外科学   294篇
综合类   283篇
预防医学   329篇
眼科学   167篇
药学   187篇
  3篇
中国医学   78篇
肿瘤学   70篇
  2024年   8篇
  2023年   91篇
  2022年   136篇
  2021年   234篇
  2020年   210篇
  2019年   191篇
  2018年   174篇
  2017年   134篇
  2016年   148篇
  2015年   120篇
  2014年   201篇
  2013年   325篇
  2012年   149篇
  2011年   181篇
  2010年   134篇
  2009年   153篇
  2008年   143篇
  2007年   133篇
  2006年   117篇
  2005年   92篇
  2004年   87篇
  2003年   66篇
  2002年   52篇
  2001年   47篇
  2000年   44篇
  1999年   30篇
  1998年   30篇
  1997年   24篇
  1996年   27篇
  1995年   32篇
  1994年   16篇
  1993年   15篇
  1992年   15篇
  1991年   11篇
  1990年   12篇
  1989年   14篇
  1988年   7篇
  1987年   8篇
  1986年   5篇
  1985年   11篇
  1984年   6篇
  1983年   6篇
  1982年   7篇
  1981年   9篇
  1980年   7篇
  1979年   2篇
  1978年   5篇
  1977年   2篇
  1976年   1篇
  1974年   2篇
排序方式: 共有3674条查询结果,搜索用时 15 毫秒
101.
102.
目的    应用锥形束CT(cone beam computed tomography,CBCT)测量上下颌牙列邻面接触区釉质厚度及邻接点距离牙合面和釉牙骨质界的垂直高度,为临床邻面去釉提供参考数据。方法    选取2019年6—10月于吉林大学口腔医院医学影像科行CBCT检查患者50例,根据纳入标准选取符合测量条件的牙齿145颗,运用Invivo软件测量每颗牙齿邻面接触区的釉质厚度及邻接点距离牙合面和釉牙骨质界的垂直高度。结果    从切牙至第一磨牙邻面接触区釉质厚度有逐渐增大的趋势;大多数牙位的远中邻面接触区釉质厚度大于近中(P < 0.05),仅有上颌第一前磨牙和下颌第一磨牙的近远中邻面接触区釉质厚度差异无统计学意义(P > 0.05);上下颌左右侧同名牙邻面接触区釉质厚度差异无统计学意义(P > 0.05);除上颌中切牙-侧切牙、上下颌侧切牙-尖牙邻面接触区外,其余相邻牙齿近远中邻面接触区釉质厚度相似,差异均无统计学意义(均P > 0.05);上颌邻面接触区平均釉质厚度大于下颌,差异有统计学意义(P < 0.05);上下颌近远中邻接点到牙合面的垂直距离均小于到釉牙骨质界的垂直距离(均P < 0.05)。结论    不同牙位近远中邻面接触区釉质厚度不同,邻接点距离牙合面和釉牙骨质界的垂直高度也不同,临床邻面去釉时不同牙位去釉量不能按照同一标准进行,应结合CBCT影像资料制定个体化治疗方案。  相似文献   
103.
目的研究曲面体层片与锥形束CT(cone beam computer tomography,CBCT)判断上颌后牙牙根与上颌窦关系的准确性,为临床医师根据曲面体层片信息治疗上颌后牙区相关疾病提供参考。方法纳入80例符合标准的患者(牙根数671个),以锥形束CT为标准,在曲面体层片及锥形束CT片上测量上颌后牙根尖到上颌窦的距离。结果当曲面体层片显示上颌窦的皮质骨连续,牙根距上颌窦存在明显距离、与上颌窦相切时,曲面体层片判断上颌后牙牙根与上颌窦关系的准确率分别为82.0%、70.0%;当曲面体层片显示上颌窦皮质骨中断,牙根突入上颌窦内时,曲面体层片判断上颌后牙牙根与上颌窦关系的准确率为48.5%。曲面体层片、锥形束CT均显示牙根突入上颌窦时,曲面体层片测量上颌后牙牙根突入上颌窦距离为(2.19±1.82)mm,而锥形束CT测量距离为(1.47±1.01)mm,两者差异具有统计学意义(P<0.05)。结论曲面体层片判断上颌后牙牙根未进入上颌窦的准确率较高,但判断上颌后牙牙根突入上颌窦的准确率较低。  相似文献   
104.
目的 应用高频超声测量未育女性在四个位置的腹直肌间距并分析相关因素,旨在初步制定正常腹直肌间距(IRD)的参考值范围。 方法 选取2019年6月至2019年9月在我院行健康体检的106名健康未育女性志愿者,体质量指数(BMI)均≤30kg/m2,应用高频超声分别于仰卧位静息状态及卷腹动作测量脐上3cm、脐部、脐下2cm和脐下3cm四个位置的IRD,应用百分位数法计算IRD参考值范围,并分析IRD与年龄、身高、体重、BMI指数之间的关系。 结果 未育女性仰卧位静息状态IRD正常值范围如下:脐上3cm为4~15mm,脐部为5~20mm,脐下2cm为0~7mm,脐下3cm为0~3mm。相关性分析显示IRD与年龄、身高无相关性,与体重和BMI指数呈较弱的正相关。 结论 本研究应用高频超声初步建立了未育女性IRD的参考值范围,为腹直肌分离的诊断提供了依据,IRD与体重和BMI指数呈较弱的正相关。  相似文献   
105.
目的:观察头针留针下天轨步行训练对脑卒中偏瘫患者下肢运动功能的影响。方法:将40例脑卒中偏瘫患者随机分为对照组、观察组每组各20例。在两组患者均予以常规内科基础治疗和康复治疗的基础上,对照组行头针治疗和天轨步行训练(两者分开进行),观察组行头针留针下天轨步行训练(两者同时进行)。治疗前、治疗4周后分别对两组患者进行Berg平衡量表、Fugl-Meyer量表下肢运动功能评分、FAC功能性步行量表、改良Barthel指数评分。结果治疗前两组患者一般资料及各项功能评分差异无统计学意义(P>0.05),具有可比性,治疗4周后两组患者各项功能评分较治疗前均明显改善(P<0.05),且观察组优于对照组(P<0.05)。结论:头针留针下天轨步行训练能够改善患者的平衡功能、运动功能、日常生活活动能力,利于脑卒中偏瘫患者下肢运动功能的恢复。  相似文献   
106.
The space between people, or ‘interpersonal distance’, creates and defines the dynamics of social interactions and is a salient cue signaling responsiveness and feeling comfortable. This distance is implicit yet clearly felt, especially if someone stands closer or farther away than expected. Increasing evidence suggests that Oxytocin (OT) serves as a social hormone in humans, and that one of its roles may be to alter the perceptual salience of social cues. Considering that empathic ability may shape the way individuals process social stimuli, we predicted that OT will differentially affect preferred interpersonal distance depending on individual differences in empathy. Participants took part in two interpersonal distance experiments: In the first, they had to stop a (computer visualized) protagonist when feeling most comfortable; in the second, they were asked to choose the room in which they would later discuss intimate topics with another. Both experiments revealed an interaction between the effect of OT and empathy level. Among highly empathic individuals, OT promoted the choice of closer interpersonal distances. Yet, OT had an opposite effect on individuals with low empathic traits. We conclude that the enhancement of social cues following OT administration may have opposite effects on individuals with different empathic abilities.  相似文献   
107.
ObjectivesThe aim of this study was to investigate the adverse impact of elevated postprocedural mitral valve pressure gradient (MPG) on outcome in a real-world population of patients with severe mitral regurgitation (MR) who underwent transcatheter mitral valve edge-to-edge repair (TEER).BackgroundTEER has become a routine treatment alternative for patients with severe MR at high surgical risk. The consequences of elevated MPG after TEER have been subject to controversial debates.MethodsAll consecutive patients undergoing TEER for either severe degenerative MR (DMR) or functional MR (FMR) at a high-volume center between September 2008 and January 2020 were prospectively included and followed periodically. Postprocedural MPG by discharge transthoracic echocardiography was considered elevated at ≥5 mm Hg. The primary combined endpoint was death or heart failure rehospitalization after 5 years.ResultsA total of 713 patients undergoing TEER (DMR, n = 265; FMR, n = 445) were included. Elevated postprocedural MPG was present in 37.0% of those with DMR (n = 98) and 22.0% of those with FMR (n = 98). In contrast to patients with FMR, 6-minute walk distance did not improve in patients with DMR with elevated MPG. Kaplan-Meier analyses did not demonstrate significant differences for the primary endpoint in patients with DMR (low vs elevated MPG, 67.3% vs 74.4%; P = 0.06) and those with FMR (78.6% vs 74.8%; P = 0.54). After adjustment, elevated MPG was an independent predictor of the primary endpoint in patients with DMR (HR: 1.59; 95% CI: 1.03-2.45; P = 0.034) but not in those with FMR (HR: 0.87; 95% CI: 0.63-1.22; P = 0.43).ConclusionsElevated postprocedural MPG is an independent predictor of adverse clinical and functional outcomes in patients with DMR but not in those with FMR  相似文献   
108.
OBJECTIVES: To investigate the association between different types of physical activity behavior and incident mobility limitation in older men and women and to examine whether muscle parameters mediate these associations. DESIGN: Cohort study with 4.5-year follow-up. SETTING: Metropolitan areas surrounding Pittsburgh, Pennsylvania, and Memphis, Tennessee. A random sample of white Medicare beneficiaries and all age-eligible blacks. PARTICIPANTS: Three thousand seventy-five black and white men and women aged 70 to 79 with no self-reported difficulty walking one-quarter of a mile or climbing 10 steps, enrolled in the Health, Aging and Body Composition (Health ABC) Study. MEASUREMENTS: Participants were classified as exercisers (reporting > or = 1,000 kcal/wk of exercise activity), lifestyle active (reporting < 1,000 kcal/wk of exercise activity and > or = 2,719 kcal/wk of total physical activity), or inactive (reporting < 1,000 kcal/wk of exercise activity and < 2,719 kcal/wk of total physical activity). The study outcome, incident mobility limitation, was defined as two consecutive, semiannual self-reports of any difficulty walking one quarter of a mile or climbing 10 steps. Thigh muscle area, thigh muscle attenuation (a marker of fat infiltration in muscle), appendicular lean soft tissue mass, and isokinetic knee extensor strength were examined as potential mediators. RESULTS: Over 4.5 years, 34.3% of men and 47.4% of women developed mobility limitation. Inactive persons had twice the risk of incident mobility limitation as exercisers (hazard ratio (HR)=2.08, 95% confidence interval (CI)=1.60-2.70, for men, HR=1.98, 95% CI=1.51-2.60, for women). Lifestyle-active men and women had an intermediate risk (HR=1.47 and 1.44, respectively). For the lifestyle active and inactive, absence of walking activity conferred an additional risk of mobility limitation. Muscle parameters did not mediate the relationship between physical activity and mobility limitation, except for knee extensor strength in men. CONCLUSION: Exercise and an active lifestyle that includes walking protect against mobility loss in older men and women. Activity effects on muscle parameters do not explain this association.  相似文献   
109.
BACKGROUND: Serum levels of C-reactive protein (CRP) are increased in patients with COPD and correlate modestly with variables predictive of outcomes. In epidemiologic studies, CRP level is associated with all-cause mortality in patients with mild-to-moderate disease. OBJECTIVE: To determine if CRP levels are associated with survival in patients with moderate to very severe COPD in comparison with other well-known prognostic parameters of the disease. METHODS: In 218 stable patients with COPD, we measured baseline serum CRP level, BODE (body mass index, obstruction, dyspnea, and exercise capacity) index and its components, arterial oxygenation (Pao(2)), inspiratory capacity (IC) to total lung capacity (TLC) ratio, and Charlson comorbidity score. We followed up the patients over time and evaluated the strength of the association between the variables and all-cause mortality. RESULTS: During the follow-up time (median, 36 months; 25th to 75th percentiles, 24 to 50 months), 54 patients (25%) died. CRP levels were similar between survivors and the deceased (median, 3.8 mg/L; 95% confidence interval, 1.9 to 8.1; vs median, 4.5 mg/L; 95% confidence interval, 2.1 to 11.5; p = 0.22) and was not significantly associated with survival. CONCLUSIONS: In this population of patients with clinically moderate to very severe COPD, the level of CRP level was not associated with survival compared with other prognostic clinical tools such as the BODE index, modified Medical Research Council scale, 6-min walk distance, percentage of predicted FEV(1), IC/TLC ratio < 0.25, and Pao(2). Other long-term studies of well-characterized patients with COPD could help determine the exact role of CRP levels as a biomarker in patients with clinical COPD.  相似文献   
110.
目的:分析男性新生儿肛门生殖器距离(AGD)与睾丸下降不全之间的关系,探索其可能存在的内在联系。方法:连续纳入哈尔滨市妇产医院及哈尔滨市双城区急救中心妇产科2013年9月至2014年9月出生的汉族男性新生儿350例,出生后24 h对所有新生儿测量AGD,排除有合并直肠肛门畸形及尿道下裂的患儿,由小儿外科医生进行体格检查,确定其是否存在睾丸下降不全,并根据睾丸位置分为阴囊上方型、腹股沟型及不可触及型。结果:350例新生儿中隐睾39例,隐睾新生儿的AGD长度显著短于非隐睾新生儿[(2.01±0.22)cm vs(2.35±0.19)cm;P0.01];在排除早产儿及低出生体重儿情况下该差异仍具有统计学意义[(2.32±0.14)cm vs(2.06±0.19)cm;(2.37±0.17)cm vs(2.12±0.12)cm,P均0.01];高位隐睾新生儿AGD较低位隐睾儿AGD有降低趋势,但无统计学意义(F=0.434,P0.05);单侧隐睾与双侧隐睾新生儿AGD值差异也无统计学意义[(1.96±0.13)cm vs(2.02±0.17)cm,P0.05)]。结论:在所研究的男性新生儿人群中,AGD值与睾丸下降不全具有相关性。AGD可以作为雄激素作用窗口期存在异常干扰的衡量指标。  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