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   2338254篇
  免费   184652篇
  国内免费   7497篇
耳鼻咽喉   31990篇
儿科学   78445篇
妇产科学   64280篇
基础医学   326182篇
口腔科学   63885篇
临床医学   209042篇
内科学   471859篇
皮肤病学   53371篇
神经病学   188604篇
特种医学   94716篇
外国民族医学   883篇
外科学   362460篇
综合类   53123篇
现状与发展   3篇
一般理论   747篇
预防医学   183513篇
眼科学   51061篇
药学   168831篇
  7篇
中国医学   4189篇
肿瘤学   123212篇
  2018年   23681篇
  2017年   18254篇
  2016年   21205篇
  2015年   23821篇
  2014年   33213篇
  2013年   50335篇
  2012年   64951篇
  2011年   69480篇
  2010年   42582篇
  2009年   41084篇
  2008年   65616篇
  2007年   70264篇
  2006年   71347篇
  2005年   69139篇
  2004年   66735篇
  2003年   64968篇
  2002年   62705篇
  2001年   112434篇
  2000年   116354篇
  1999年   97949篇
  1998年   28446篇
  1997年   25592篇
  1996年   26523篇
  1995年   26123篇
  1994年   24525篇
  1993年   22885篇
  1992年   79855篇
  1991年   78053篇
  1990年   75479篇
  1989年   72110篇
  1988年   66574篇
  1987年   65338篇
  1986年   61358篇
  1985年   59032篇
  1984年   44863篇
  1983年   37791篇
  1982年   22917篇
  1981年   20703篇
  1980年   19106篇
  1979年   40402篇
  1978年   28825篇
  1977年   24480篇
  1976年   22550篇
  1975年   23938篇
  1974年   28140篇
  1973年   27011篇
  1972年   24895篇
  1971年   22897篇
  1970年   21231篇
  1969年   19574篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Chemical-shift imaging: a hybrid approach   总被引:1,自引:0,他引:1  
The hybrid technique of projection-reconstruction echo-planar (PREP) imaging for obtaining chemical-shift images is demonstrated experimentally using a fluorine sample. The technique which is a variation on echo-planar imaging (EPI) relies on a multipass procedure. It is nevertheless quite efficient and consequently chemical-shift images may be produced in a few minutes. The method produces images in 64 chemical-shift regions, each region mapped spatially by 64 X 64 pixels. The imaging time was just over 4 min. These 64 chemical-shifted images can be straightforwardly added together to form an undistorted image of the complete object. In addition the chemical-shift spectrum can be extracted and the various chemical-shift images can be unambiguously assigned to the spectral peaks.  相似文献   
992.
993.
994.
In acute experiments on anesthetized cats with total ischemia of the brain (15-minute arrest of blood autoperfusion of the cerebral vessels by a stable blood volume) it was shown that euphylline and no-shpa administered before ischemia or in the early period after ischemia inhibit or prevent the development of the postischemic phenomenon of non-recovery of the cerebral blood flow. The two drugs contributed to survival of albino rats following the brain ischemia produced by ligation of both carotid arteries.  相似文献   
995.
The dissociation of visuospatial neglect and neglect dyslexia.   总被引:5,自引:3,他引:2       下载免费PDF全文
A right-handed man with a left hemisphere lesion extending into the right hemisphere, with evidence of both a left-sided neglect dyslexia and right-sided visuospatial neglect is reported. When copying simple geometric designs he omitted to copy figures on the right-hand side of the page, when bisecting lines he tended to bisect the line to the left of the line's actual centre. He had a neglect dyslexia which was characterised by paralexic errors affecting the beginning (that is, left) of words. The occurrence of these two phenomena provides evidence of a dissociation of these forms of neglect. The findings are discussed in relation to the possible mechanisms of unilateral neglect.  相似文献   
996.
In a randomized study the clinical and bacteriologic effectiveness of imipenem was compared with the classical combination of netilmicin with clindamycin in patients who had surgery for an intraperitoneal infection, localized or generalized, with positive bacteriologic findings of the specimen taken at surgery. Excluded were all patients who received other antibiotics before surgery, or who died within 3 days after antibiotic therapy was started. Imipenem was given at a dose of 500 mg t.i.d., clindamycin 600 mg t.i.d., and netilmicin according to serum levels. The diagnoses ranged from postoperative peritonitis, gallbladder empyema, perforated gastroduodenal ulcer, small bowel perforation with and without obstruction, and perforated appendicitis to perforation of the colon. The bacteriologic work-up included examination of the primary specimen (aerobic and anaerobic), the urine, feces, and serologic testing for Candida albicans once or twice a week and after the course of antibiotic therapy. In addition, pH measurements of abscesses and drainage fluids were performed. Ninety-three patients entered the study. Forty-seven patients were treated with imipenem (test group), and 46 patients were treated with the combination therapy (control group). The two groups did not show significant differences in age, sex, diagnostic groups, risk factors, primary bacteriology, and duration of therapy (mean: 6.7 days). Thirty-eight patients (80.9%) treated with imipenem were cured, six patients (12.8%) were improved, and there were three (6.4%) failures. The respective numbers for the control group were 31 (67.4%), 10 (21.7%), and 5 (10.9%). The mean duration of hospitalization was 19 days for the test group and 24.5 days for the control group. There were four wound infections in the test group and 11 wound infections in the control group. Imipenem is at least as effective in the adjuvant therapy of intra-abdominal infections as the combination of netilmicin with clindamycin.  相似文献   
997.
The experiments were carried out on male albino rats trained and tested for retention (24 hr later) in a shuttle-box. Angiotensin II (AT II) 0.10 micrograms intracerebroventricularly (i.c.v.), gamma-aminobutyric acid (GABA) 100 micrograms i.c.v., bicuculline 0.5 and 1.0 mg/kg intraperitoneally (i.p.), and picrotoxin 0.5 and 1.0 mg/kg i.p. administered independently or in combinations immediately after training. AT II was found to improve retention. GABA also facilitated retention. Combination of AT II + GABA potentiated the memory-improving effect of AT II. Bicuculline and picrotoxin at a dose of 0.5 mg/kg did not affect retention, while at a dose of 1.0 mg/kg they improved it. Combinations of AT II + bicuculline (0.5 mg/kg) and AT II + picrotoxin (0.5 mg/kg) abolished the retention-improving effect of AT II. Bicuculline (0.5 mg/kg) or picrotoxin (0.5 mg/kg) abolished the retention-facilitating effect of the combination of AT II + GABA as well as the potentiating action of GABA on the memory effect of AT II. These results suggest the participation of GABAergic transmission in the CNS in the mechanisms of the long-term memory-improving effect of AT II.  相似文献   
998.
Two cases are presented in which the cause of small-bowel obstruction was enterolith originating in jejunal diverticula.  相似文献   
999.
Experience with the 'skew flap' below-knee amputation   总被引:3,自引:0,他引:3  
A review of 353 lower limb amputations over the last 7 years has been performed to assess the results of the skew flap myoplastic below-knee amputation which was introduced in April 1983 because of reported advantages in terms of wound healing and earlier ambulation. Comparing the first 3 1/2 year period with the second, the total number of amputations decreased by 31 per cent. The number of above-knee amputations remained similar in the two periods (82,62), whilst the number of Gritti-Stokes amputations fell from 79 to 21 (0.001 greater than P greater than 0.01). The proportion of below-knee (BK) amputations increased from 50 (23.7 per cent) to 59 (41.5 per cent) (0.01 greater than P greater than 0.025). The groups were comparable in terms of previous vascular surgery and co-existing medical conditions. The time to full stump healing was significantly shorter in the skew flap group compared with the earlier Burgess type BK amputation (P = 0.001), and there was a trend to fewer stump failures in the skew flap group. We therefore feel that the skew flap amputation gives superior results to the Burgess BK amputation in terms of healing and a lower complication rate, allowing a higher proportion of BK amputations to be performed. A prospective randomized trial of the two techniques is in hand to determine the accuracy of this hypothesis.  相似文献   
1000.
Ambient light affects pulse oximeters   总被引:1,自引:0,他引:1  
  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