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   6758篇
  免费   510篇
  国内免费   58篇
耳鼻咽喉   82篇
儿科学   413篇
妇产科学   91篇
基础医学   843篇
口腔科学   218篇
临床医学   496篇
内科学   1622篇
皮肤病学   121篇
神经病学   443篇
特种医学   329篇
外科学   682篇
综合类   262篇
一般理论   1篇
预防医学   441篇
眼科学   120篇
药学   482篇
中国医学   55篇
肿瘤学   625篇
  2023年   38篇
  2022年   87篇
  2021年   226篇
  2020年   117篇
  2019年   133篇
  2018年   155篇
  2017年   132篇
  2016年   154篇
  2015年   159篇
  2014年   255篇
  2013年   333篇
  2012年   436篇
  2011年   398篇
  2010年   283篇
  2009年   242篇
  2008年   280篇
  2007年   331篇
  2006年   267篇
  2005年   262篇
  2004年   239篇
  2003年   224篇
  2002年   200篇
  2001年   190篇
  2000年   182篇
  1999年   176篇
  1998年   146篇
  1997年   122篇
  1996年   99篇
  1995年   98篇
  1994年   79篇
  1993年   72篇
  1992年   114篇
  1991年   85篇
  1990年   100篇
  1989年   107篇
  1988年   94篇
  1987年   75篇
  1986年   73篇
  1985年   70篇
  1984年   58篇
  1983年   55篇
  1982年   32篇
  1981年   23篇
  1979年   43篇
  1978年   31篇
  1976年   28篇
  1975年   24篇
  1974年   22篇
  1973年   22篇
  1970年   22篇
排序方式: 共有7326条查询结果,搜索用时 15 毫秒
91.
92.
93.
Aims: The aim of the study was to determine whether increased physical activities (PA) affect frailty for old women, 75 years and older (OO), compared to 60–74 years old (YO). Methods: This cross-sectional study measured 19 frailty indicators (muscle strength and endurance, balance, gait characteristics, and function), using 46 community-dwelling women. PA were divided into three levels by caloric expenditure per week (<2,000 kcal/week, 2,000–3,999 kcal/week, >4,000 kcal/week). Results: As PA level increased, a gap (=difference) between OO and YO narrowed for step length and function, but for quadriceps strength and endurance, a gap widened. Conclusions: Frailty progresses with aging but older women who engage in a high level of physical activity (>4,000 kcal/week) can increase mobility and functional capacity, but not for muscle strength and endurance. Starting regular resistance training activities early in the aging process is critical to improve or maintain muscle quality to offset age-related frailty.  相似文献   
94.
Surgical emphysema is defined as gas or air trapped in the subcutaneous tissue plane. Here, we report a rare case of bilateral periorbital and cervicofacial subcutaneous emphysema following a vitreoretinal surgery for inadvertent globe perforation during the administration of peribulbar anesthesia. This condition, although self-resolving when restricted to the subcutaneous plane has the potential to spread into deeper tissue planes such as the retropharyngeal space. The presence of crepitus helps to distinguish it from angioneurotic edema. Ophthalmologists must be sensitive to the fact that surgical emphysema can be a very rare, but possible complication of an intraocular surgery following globe perforation.  相似文献   
95.
Clinical Rheumatology - Consensus on treatment of idiopathic inflammatory myositis (IIM), particularly with regard to flares and interstitial lung disease (ILD), does not exist. We studied the...  相似文献   
96.
97.
Cross-sectional and Doppler echocardiography are currently the most important non-invasive tests for the evaluation of mitral stenosis. Recent experience has, however, shown that parameters that are reliable before mitral valvotomy may not be valid after the procedure. We have studied the validity of estimation of the area of the mitral valve by echo-planimetry, by Doppler pressure half time and the transmitral end-diastolic pressure gradient calculated by continuous wave Doppler in 100 patients (aged 10-30 years) before and after balloon mitral valvoplasty (n = 70) or surgical closed mitral valvotomy (n = 30). These patients underwent cardiac catheterisation and echocardiographic studies before, immediately after and 8-12 (9.3 +/- 2.2) weeks following balloon valvoplasty or closed valvotomy. The area as estimated echocardiographically correlated well with that obtained by the Gorlin formula before (r = 0.80), but not immediately after (r = 0.67) or on follow up after mitral valvotomy. There was good correlation between Doppler pressure half time and the area as estimated by the Gorlin formula before (r = 0.89) and on follow up after valvotomy (r = 0.82), but the correlation was not as good in the immediate period after valvotomy (r = 0.60). The end-diastolic pressure gradients obtained by Doppler examination and at cardiac catheterisation correlated well with each other before (r = 0.94), immediately after valvotomy (r = 0.92) and on follow up (r = 0.94). Hence, the reliability of estimation of the area of the mitral valve by echo-planimetry and by Doppler pressure half time varies according to the time at which the examination is performed following commissurotomy.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
98.
Two hundred eighty patients (197 men and 83 women) with normal rest electrocardiograms and no history of prior myocardial infarction were referred for evaluation of chest pain. It was found that exercise-induced premature ventricular complexes had a lower sensitivity, specificity, positive predictive value and negative predictive value in predicting significant coronary artery disease than exercise-induced ST segment depression greater than or equal to 1 mm. The incidence of exercise-induced premature ventricular complexes was not significantly different in patients with no significant coronary artery disease, single vessel disease or multivessel disease. The site of origin of exercise-induced premature ventricular complexes was not helpful in predicting the presence or severity of coronary artery disease. At a mean follow-up period of 47.1 months, exercise-induced premature ventricular complexes did not predict coronary events (cardiac death or nonfatal myocardial infarction) in men or women.  相似文献   
99.
100.
Dexamethasone increased alkaline phosphatase levels up to 7-fold in the osteoblast-like rat osteosarcoma cell line ROS 17/2.8. This effect was associated with reduced cell growth and took place over several days in culture. The increase in enzyme activity was dose dependent, (half-maximum near 1 nM, with a hormone specificity suggesting glucocorticoid receptor mediation). Dexamethasone also increased enzyme activity in ROS 2/3 cells, but not in two nonosteoblastic osteosarcoma cell lines, indicating that among these cell lines, the effect is specific for osteoblast-like cells. Moreover, enzyme activity in both control and dexamethasone-treated cells correlated directly with levels of radioimmunoassayable bone-type isoenzyme. Increases in alkaline phosphatase activity in response to dexamethasone were detectable after about 5 h and were inhibited by both actinomycin D and cycloheximide. Thus glucocorticoids appear to increase de novo enzyme synthesis in ROS 17/2.8 cells. Finally, the cAMP-elevating agents PTH, isoproterenol, and 8-bromo-cAMP, which were previously shown to reduce alkaline phosphatase activity in osteoblast-like cells, antagonized the effects of dexamethasone. Moreover, in the presence of dexamethasone, lower concentrations of these agents were required for inhibitory effects on alkaline phosphatase.  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