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   24627篇
  免费   1704篇
  国内免费   73篇
耳鼻咽喉   372篇
儿科学   553篇
妇产科学   403篇
基础医学   3337篇
口腔科学   647篇
临床医学   2319篇
内科学   5547篇
皮肤病学   597篇
神经病学   1958篇
特种医学   1156篇
外国民族医学   2篇
外科学   3481篇
综合类   365篇
一般理论   19篇
预防医学   1665篇
眼科学   729篇
药学   1691篇
中国医学   50篇
肿瘤学   1513篇
  2022年   181篇
  2021年   347篇
  2020年   166篇
  2019年   321篇
  2018年   376篇
  2017年   317篇
  2016年   429篇
  2015年   467篇
  2014年   648篇
  2013年   1005篇
  2012年   1314篇
  2011年   1353篇
  2010年   776篇
  2009年   757篇
  2008年   1304篇
  2007年   1448篇
  2006年   1464篇
  2005年   1366篇
  2004年   1388篇
  2003年   1274篇
  2002年   1337篇
  2001年   480篇
  2000年   404篇
  1999年   496篇
  1998年   346篇
  1997年   317篇
  1996年   234篇
  1995年   261篇
  1994年   189篇
  1993年   195篇
  1992年   241篇
  1991年   242篇
  1990年   233篇
  1989年   225篇
  1988年   195篇
  1987年   194篇
  1986年   176篇
  1985年   209篇
  1984年   241篇
  1983年   231篇
  1982年   268篇
  1981年   262篇
  1980年   197篇
  1979年   166篇
  1978年   142篇
  1977年   185篇
  1976年   168篇
  1975年   163篇
  1974年   143篇
  1973年   148篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
PURPOSE: To evaluate qualitative wall motion assessment vs. quantitative wall thickening for the assessment of subtle changes in myocardial systolic function using cine MRI. METHODS: Cine MR images were obtained in 5 canines with a significant coronary artery stenosis and in 2 controls on a 1.5T scanner. Qualitative results were obtained using a numerical scoring system; quantitative analysis was performed using a semi-automatic segmentation program. The techniques were matched and compared using Spearman correlations. RESULTS: All correlations in the experimental group revealed significant but weak to moderate relationships between the qualitative and quantitative results (e.g., at-risk tissue rho = 0.363, p < 0.0001; remote tissue rho = 0.275, p = 0.0002), with each identifying changes in regional function that ensued following creation of the stenosis. Intra-observer variability was reasonable in both methods when repeat analysis on a subset of the data was performed, with both techniques showing a significant correlation between the repeated measurements (quantitative - rho = 0.52, p < 0.0001; qualitative - rho = 0.54, p < 0.0001). CONCLUSION: Both methods were able to detect very limited wall motion abnormalities present in the canines with significant stenosis and either method gives comparable results.  相似文献   
22.
Ohne ZusammenfassungD 2.Die Arbeit wurde mit Hilfe der Rockefeller-Foundation durchgeführt.  相似文献   
23.
There is growing evidence that obesity in women lead to a more severe form of hyperandrogenism and other endocrine abnormalities which may have some health implications later in life. Obese females are at higher risk for metabolic syndrome due to severe hyperandrogenemia. Calculated values for free testosterone are equivalent to those obtained by equilibrium dialysis, which is one of the reference measurement procedures (RMP) for estimation of free testosterone and may be capable of replacing values estimated using RMP's. For adult women correlations of body mass index (BMI) with calculated free (cFT) and bioavailable testosterone (cBT) are still rare, while these data are reported for peripubertal and adolescent girls. In this study we aimed to investigate the association between BMI and different androgen parameters (including calculated free and bioavailable testosterone, free androgen index, and sex hormone-binding globulin [SHBG]) in adult women with Hirsutism and with PCOS. In hirsute women with BMI > or = 25 kg/m2 measured total testosterone (TT) was significantly higher, SHBG was significantly lower and the calculated androgen parameter (FAI, cFT and cBT) were significantly higher compared to women with BMI < 25 kg/m2. In PCOS women with BMI > or = 25 kg/m2 TT was significantly higher, SHBG was significantly lower and the calculated androgen parameter (FAI, cFT and cBT) were also significantly higher compared to women with BMI < 25 kg/m2. In both the Hirsutism and PCOS-group there was a positive correlation between BMI and TT, cFT, and cBT, while BMI was negatively correlated with SHBG. In summary, in adult women with Hirsutism and PCOS obesity is associated with increased levels of TT and decreased levels of SHBG resulting in significant elevated calculated free and bioavailable testosterone levels. Obesity might lead to a more severe form of hyperandrogenism with elevated calculated free and bioavailable testosterone in the study population.  相似文献   
24.
25.
When the contrast polarity of a visual acuity chart is reversed by using bright letters on a dark background instead of dark on light, the shape and height of the resolution feature in the retinal image is identical but inverted compared with the normal situation. However, the contrast is different in the two cases because the background light level, which is a dividing factor when contrast is calculated, is much less when only the letters are bright. To the extent that contrast is a limiting factor in visual acuity, reversed-contrast acuity would be expected to be better, and proportionally more so in eyes where light scatter and aberrations widen and flatten the point-spread function. In a careful psychophysical study of Landolt C resolution, the minimum angle of resolution was found to be significantly smaller for white letters on a dark background than for the traditional dark on bright situation.  相似文献   
26.
27.
28.
29.
Eine 71-jährige, gesundheitsbewusste, zu einer Medizinerfamilie gehörige Patientin stellt sich zur Bewertung einer seit 10 Jahren bekannten Cholesterinerhöhung und der an anderer Stelle begonnenen Behandlung mit Mevinacor® (Lovastatin) vor.Im vorausgegangenen Jahr waren bei vielen Gelegenheiten Gesamtcholesterinkonzentrationen zwischen 289 und 345 mg/dl bestimmt worden. LDL wurde bis auf maximal 261 mg/dl erhöht gefunden, die HDL-Cholesterin-Werte lagen zwischen 40 und 48 mg/dl, die Triglyzeride zwischen 99 und 264 mg/dl.  相似文献   
30.
A group of 34 consecutive patients with coronary artery disease (n = 29) or dilated cardiomyopathy (n = 5) (3 women, 31 men, age 38-80 yr) who had severely impaired left ventricular function (left ventricular ejection fraction less than or equal to 40%) and high-grade ventricular ectopic activity (sustained or nonsustained ventricular tachycardia or ventricular fibrillation) were treated with amiodarone (mean dose: 206 mg/d) and followed for 1-117 (mean: 49) months. In the total group, there were seven sudden deaths, five deaths due to pump failure, one non-cardiac death, and two successful heart transplantations during follow-up. Thus the annual cardiac mortality in these carefully selected and followed patients was 8, 6%, the annual cardiac event rate was 10, 1%. The cumulative cardiac survival-rate was 62% after 5 years and 41% after 10 years. In five patients, treatment was interrupted after 10 to 43 months, three of the patients were alive at follow-up and two suffered cardiac death, resulting in an annual cardiac death rate of 12% in this subgroup of treatment. Based on the results of this retrospective analysis we conclude that in patients with low left ventricular ejection fraction and nonsustained or sustained ventricular tachycardia treated with low dose amiodarone, mortality was unexpectedly low. Thus, it may be the antiarrhythmic treatment to be considered in patients with ventricular tachycardia and severe left ventricular dysfunction.  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