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   2182388篇
  免费   168822篇
  国内免费   5208篇
耳鼻咽喉   28933篇
儿科学   73546篇
妇产科学   62253篇
基础医学   313274篇
口腔科学   60128篇
临床医学   197775篇
内科学   428212篇
皮肤病学   50452篇
神经病学   177697篇
特种医学   83159篇
外国民族医学   753篇
外科学   324944篇
综合类   51792篇
现状与发展   3篇
一般理论   823篇
预防医学   172852篇
眼科学   50024篇
药学   155241篇
  4篇
中国医学   4897篇
肿瘤学   119656篇
  2019年   17176篇
  2018年   24372篇
  2017年   18747篇
  2016年   21232篇
  2015年   23791篇
  2014年   33339篇
  2013年   50290篇
  2012年   67346篇
  2011年   71588篇
  2010年   42323篇
  2009年   40252篇
  2008年   66519篇
  2007年   70399篇
  2006年   71298篇
  2005年   68890篇
  2004年   66340篇
  2003年   63431篇
  2002年   61250篇
  2001年   105678篇
  2000年   108308篇
  1999年   90226篇
  1998年   25557篇
  1997年   23049篇
  1996年   23079篇
  1995年   22083篇
  1994年   20239篇
  1993年   18944篇
  1992年   69493篇
  1991年   67002篇
  1990年   64949篇
  1989年   62208篇
  1988年   56796篇
  1987年   56309篇
  1986年   52601篇
  1985年   50408篇
  1984年   38194篇
  1983年   32225篇
  1982年   19575篇
  1981年   17478篇
  1979年   34428篇
  1978年   24497篇
  1977年   20509篇
  1976年   19347篇
  1975年   20076篇
  1974年   24343篇
  1973年   23450篇
  1972年   21744篇
  1971年   20004篇
  1970年   18901篇
  1969年   17506篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
In order to determine if serial, noninvasive evaluation of polytetrafluoroethylene (PTFE) vascular access grafts could identify a subgroup of patients at risk for thrombosis, the authors studied flow characteristics, using duplex ultrasonic scanning, in 18 hemodialysis patients with forearm loop grafts. On average, five examinations were performed per patient over the 10-month study period. Seven episodes of thrombosis occurred in six patients. The mean Doppler flow in grafts that subsequently thrombosed was significantly lower than in those that did not (544 +/- 218 ml/min versus 843 +/- 391 ml/min, p less than 0.001). The interval from last examination to thrombosis ranged from 13 to 58 days. At a defined cut-off flow of 450 ml/min, this test yielded a sensitivity of 83% and a specificity of 75% for episodes of thrombosis occurring within 2 to 6 weeks. The authors conclude that episodes of thrombosis in PTFE arm loop grafts are usually preceded by significantly lower Doppler-measured flow than grafts that do not thrombose and that it may be possible, by this means, to identify grafts at risk.  相似文献   
982.
Two methods of separating human sperm were compared using twenty-two semen samples. The sperm were separated by a swim-up technique or by self-migration on a Percoll gradient followed by medium change. After separation, the sperm obtained were assessed for progressive motility, ATP content, energy charge index ([ATP + 0.5 ADP]/[ATP + ADP + AMP]) and morphology. In general, and especially for semen samples containing less than 20 X 10(6) sperm/ml, separation by Percoll gradient selected sperm that were superior to those separated by the swim-up technique. The relatively high energy charge index (greater than 0.8) showed that the sperm tolerated the separation conditions well. It is suggested that self-migration on a Percoll gradient should prove useful for obtaining sperm of high quality.  相似文献   
983.
984.
The records of 29 consecutive patients treated by a pure, open, anterior acromioplasty were reviewed retrospectively. Excluded from consideration were patients with the following pathologic diagnoses or histories: (1) previously attempted acromioplasty on the same shoulder; (2) intraoperatively confirmed rotator cuff tear; (3) any surgically treatable biceps tendon or acromioclavicular abnormality; (4) lost to follow-up study. Three different techniques were employed to perform the acromioplasties. The first technique required partial deltoid origin detachment with an osteotome. The second technique spared the deltoid origin, while again using an osteotome to perform the acromioplasty. The third technique also spared the deltoid origin but used a high-speed burr to perform the acromioplasty. Evaluated in terms of patient satisfaction, residual pain, length of convalescence, suboptimal results, and complications, the first technique proved to be the least effective. The second technique produced early, excellent results. The third technique, in which a burr was employed through an intact deltoid origin, was most effective; technically, the method was also relatively simple and reliable.  相似文献   
985.
Several reports in the literature suggest a relationship between lead intoxication and thermoregulatory capacity. To investigate the effects of lead on the control of body temperature, mice of the BALB/c strain were injected intraperitoneally with lead acetate (0 to 100 mg/kg) while colonic temperature was measured 30, 60, and 90 min post-injection at ambient temperatures (Ta) of 20 and 30 degrees C. Lead acetate caused a transient hypothermia, an effect which was augmented at cooler Ta's. In a second experiment, mice were injected with 100 mg/kg lead acetate and placed in a longitudinal temperature gradient to measure their preferred Ta. Lead acetate significantly reduced the preferred Ta during the first 30 min post-injection which augmented the lead-induced hypothermia. In a third experiment it was found that lead acetate-induced lethality was potentiated with increasing Ta. Hence, the hypothermic response to acute lead acetate treatment may be beneficial to survival.  相似文献   
986.
A case of Goldenhar’s Syndrome in a 10 year old girl is reported. The unusual features are the absence of epibulbar dermoid which is one of the major hallmarks of the Syndrome and the presence of an associated Cyanotic Heart disease.  相似文献   
987.
988.
989.
990.
Cibenzoline, a new class I antiarrhythmic drug, was compared with quinidine in an open crossover study of 20 patients with frequent (greater than 30/hr) premature ventricular depolarizations (PVDs). Eight patients treated with cibenzoline experienced more than 75% reduction in PVD frequency. Cibenzoline completely suppressed ventricular couplets in eight of 17 patients and inhibited ventricular tachycardia (VT) in four of 13 patients. Only four patients (20%) responded to quinidine with a similar reduction in PVDs. Quinidine completely suppressed ventricular couplets in eight of 17 patients and episodes of VT in six of 13 patients. Cibenzoline prolonged PR, QRS, and QTc intervals. Eight patients who had shown more than a 75% reduction of PVDs were treated with cibenzoline for an extended period. At the end of three months, only five of eight patients continued to have 75% or greater reduction of PVDs. At the end of six and 12 months, four of five patients continued to have 75% or greater reduction of PVDs. Cibenzoline was similarly effective in suppressing complex arrhythmias. Thus, cibenzoline was only slightly superior to quinidine in suppressing ventricular arrhythmias. With long-term use of cibenzoline, significant PVD suppression was noted at the end of three months but not afterward.  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