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   1488095篇
  免费   108179篇
  国内免费   4505篇
耳鼻咽喉   19637篇
儿科学   49548篇
妇产科学   40362篇
基础医学   219845篇
口腔科学   40394篇
临床医学   141063篇
内科学   285682篇
皮肤病学   30722篇
神经病学   126335篇
特种医学   56329篇
外国民族医学   387篇
外科学   210335篇
综合类   29561篇
现状与发展   1篇
一般理论   497篇
预防医学   121210篇
眼科学   32941篇
药学   109487篇
  6篇
中国医学   3453篇
肿瘤学   82984篇
  2021年   12139篇
  2019年   12881篇
  2018年   18952篇
  2017年   14481篇
  2016年   16332篇
  2015年   18626篇
  2014年   24429篇
  2013年   37072篇
  2012年   51967篇
  2011年   54219篇
  2010年   31454篇
  2009年   28493篇
  2008年   49982篇
  2007年   53076篇
  2006年   53177篇
  2005年   51969篇
  2004年   49553篇
  2003年   47347篇
  2002年   46121篇
  2001年   65991篇
  2000年   67726篇
  1999年   56920篇
  1998年   16100篇
  1997年   14522篇
  1996年   14064篇
  1995年   13243篇
  1994年   12333篇
  1993年   11591篇
  1992年   43580篇
  1991年   42723篇
  1990年   41317篇
  1989年   39170篇
  1988年   36165篇
  1987年   35284篇
  1986年   33600篇
  1985年   32075篇
  1984年   24166篇
  1983年   20492篇
  1982年   12373篇
  1979年   22028篇
  1978年   15675篇
  1977年   12775篇
  1976年   12487篇
  1975年   13019篇
  1974年   15771篇
  1973年   15372篇
  1972年   14263篇
  1971年   13299篇
  1970年   12235篇
  1969年   11148篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
These experiments examined the effects, on retention, of posttraining intra-amygdala administration of norepinephrine (NE), and propranolol. Rats were trained on a one-trial step-through inhibitory avoidance task and tested for retention 24 h later. Injections were administered bilaterally (1.0 microliter/injection) through chronically-implanted cannulae. Low doses of NE (0.1 or 0.3 microgram) administered shortly after training enhanced retention while higher doses (1.0 or 5.0 micrograms) were ineffective. Retention was not affected by NE administered 3 h after training. The effect of intra-amygdala NE on retention is blocked by simultaneous administration of propranolol (0.2 microgram). This finding suggests that the memory-enhancing effect of NE may be mediated by beta-receptors. Posttraining intra-amygdala NE also attenuated the retention deficit produced by adrenal demedullation. Further, intra-amygdala injections of propranolol (0.2 microgram) blocked the enhancing effect, on retention, of posttraining s.c. injections of epinephrine. These findings suggest that activation of noradrenergic receptors in the amygdala may be involved in memory processing and may play a role in the memory-modulating effect of peripheral epinephrine.  相似文献   
993.
994.
Summary Maximal oxygen uptake was assessed in 101 randomly selected 8 and 13 year old children. In both age groups a significantly higher aerobic capacity was found in boys than in girls, both in absolute terms and when maximal oxygen uptake was related to body weight, lean body mass and lean leg volume. Among girls, maximal oxygen uptake per kg body weight was lower in the older than in the younger (p<0.05). Estimation of spontaneous physical activity, by means of a questionnaire and the actometry method, indicated that physical activity was greater in children with a high than in those with a low aerobic capacity.  相似文献   
995.
Stomatococcus mucilaginosus was isolated from the blood of a patient with endocarditis and a past history of drug abuse and aortic valve replacement. At autopsy, Gram stain of the aortic valve revealed gram-positive cocci. Our isolate was atypical for S. mucilaginosus in that colonies were nonmucoid and nonadherent to agar surfaces. Cellular capsules were demonstrated by light and electron microscopy. Phenotypic characteristics identified by conventional methods as well as profile numbers obtained by using two commercial identification systems for staphylococci, the API Staph-Ident and the dms Staph Trac, are presented. Practical tests that differentiate S. mucilaginosus from the genera Micrococcus and Staphylococcus include growth on nutrient agar containing salt and lysostaphin susceptibility. Additional tests that helped differentiate our isolate from group D streptococci included hydrolysis of L-pyrrolidonyl-beta-naphthylamide and streptococcal serogrouping.  相似文献   
996.
997.
Hallux rigidus (osteoarthritis leading to reduced motion) is one of the most common afflictions of the first metatarsophalangeal joint. The diagnosis is based on the presence of pain, specific physical findings, and certain radiologic features. In this essay, we illustrate the grades of radiologic changes, which are an integral part of the surgeon's preoperative evaluation, and show examples of the postoperative radiologic appearance.  相似文献   
998.
999.
Vitamin K1 functions in the conversion of glutamate residues, present in certain bone peptides, into the putatively active γ-carboxyglutamate form. We have shown previously that the circulating levels of vitamin K1 are depressed in osteoporotic patients. However, it is known that menaquinones (vitamin K2:MK) may be more effective than vitamin K1 in this conversion of the inactive to active form of glutamate residues. A procedure for measuring such menaquinones has now demonstrated a marked deficiency of MK-7 and MK-8 in patients with osteoporotic fractures. It is suggested that estimates of circulating levels of K1, MK-7, and MK-8 might provide a biochemical risk marker of osteoporotic fractures.  相似文献   
1000.
Tubulointerstitial alterations associated with chronic glomerulonephritis (CGN) are definitely dependent on the clinical type of CGN and are accompanied by a decrease of homeostatic functions (the rate of glomerular filtration, osmotic concentration and dilution of urine, hydruresis, the magnitude of CH2O, excretion of ammonium and hydrogen ions, the ratio of ammonium excretion to hydrogen ion excretion). Maximal osmotic concentration and ammonium excretion show an especially considerable decrease. The clinical type permitting one to diagnose rather than to reject the presence of alterations and the status of certain tubular functions, osmotic concentration in particular and, to a less degree, ammonium excretion, permitting to reject the presence of the tubulointerstitial component (TIC) are of known but restricted importance for TIC recognition. The TIC can be diagnosed more adequately in exploring definite pairs of renal functions, particularly osmotic concentration of urine and ammonium excretion and maximal hydruresis and excretion of hydrogen ions. This approach is both helpful in confirming and rejecting the presence of the TIC. Of special value is the combined assessment of the clinical type and maximal osmotic urine concentration data.  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