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   380327篇
  免费   24266篇
  国内免费   2812篇
耳鼻咽喉   5191篇
儿科学   8224篇
妇产科学   10089篇
基础医学   53305篇
口腔科学   11817篇
临床医学   30211篇
内科学   78551篇
皮肤病学   8577篇
神经病学   27351篇
特种医学   13973篇
外国民族医学   82篇
外科学   60746篇
综合类   9958篇
现状与发展   1篇
一般理论   64篇
预防医学   17532篇
眼科学   9445篇
药学   31062篇
  1篇
中国医学   2199篇
肿瘤学   29026篇
  2021年   2648篇
  2019年   2746篇
  2018年   4546篇
  2017年   3455篇
  2016年   3542篇
  2015年   4052篇
  2014年   5724篇
  2013年   7429篇
  2012年   10081篇
  2011年   10271篇
  2010年   6246篇
  2009年   5873篇
  2008年   9500篇
  2007年   10331篇
  2006年   10267篇
  2005年   9336篇
  2004年   8832篇
  2003年   8564篇
  2002年   8236篇
  2001年   28280篇
  2000年   28825篇
  1999年   23686篇
  1998年   5175篇
  1997年   4269篇
  1996年   3844篇
  1995年   3492篇
  1994年   3110篇
  1993年   2851篇
  1992年   16087篇
  1991年   14834篇
  1990年   14179篇
  1989年   13983篇
  1988年   12597篇
  1987年   12081篇
  1986年   11121篇
  1985年   10338篇
  1984年   6923篇
  1983年   5609篇
  1982年   2725篇
  1979年   5487篇
  1978年   3355篇
  1977年   2981篇
  1975年   2647篇
  1974年   3074篇
  1973年   2868篇
  1972年   2835篇
  1971年   2774篇
  1970年   2514篇
  1969年   2553篇
  1968年   2255篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
A series of 6-fluoro- and 6,8-difluoro-7-(azole substituted)-1,4-dihydro-4-oxo-3-quinolinecarboxylic acids were prepared. Structure-activity relationship studies indicated that the antibacterial potency was better when the 6,8-substituents were fluorine atoms and the 7-substituent was either 1-imidazolyl, 20, or 4-methyl-1-imidazolyl, 25. From the results of studies on pharmacokinetic profile and toxicity, 20 and 25 were found to possess excellent antibacterial activities and to show high blood levels after oral administration to mice with low toxicity.  相似文献   
63.
64.
This paper describes a method by which antianginal drugs can be evaluated in the dog heart in situ. Myocardial pH was measured continuously by a micro glass pH electrode inserted in the left ventricular endocardial layers of the dog anesthetized with pentobarbital. Occlusion of the left anterior descending coronary artery (LAD) decreased myocardial pH, and release of the LAD restored the pH. The myocardial acidosis induced by ischemia was metabolic in nature and accompanied by a decrease in the levels of adenosine triphosphate and creatine phosphate and an increase in the levels of lactate in the myocardium. Drugs were injected intravenously 30 min after incomplete (partial) occlusion ot the LAD, lasting until 60 min after drug injection. Propranolol, atenolol, and sotalol markedly attenuated the myocardial pH that had been decreased by LAD occlusion. Nitroglycerin, diltiazem, and nicorandil also attenuated the pH, but these drugs were less active in attenuating myocardial acidosis. Dipyridamole, nifedipine, and beta-2 adrenoceptor antagonists were least active in this regard. It is concluded that myocardial pH can be used as an indicator of myocardial regional ischemia and utilized for evaluation of antianginal drugs.  相似文献   
65.
Intracranial pathology is a common and important complication in extremely low birth weight babies. Lenticulostriate vasculopathy (LSV) is an abnormal finding on cranial ultrasounds of sick babies and has been associated with congenital infection, chromosomal aberration and twin-to-twin transfusion. We describe a previously unreported situation of LSV being detected in both donor and recipient twin. This pair of monochorionic, diamniotic twins was admitted to the Neonatal Intensive Care Unit at 28 weeks of gestation. The mother underwent an emergency caesarean section because ultrasound and Doppler studies showed stage III twin-to-twin transfusion syndrome. The first twin weighed 998 g and second twin weighed 600 g. The first twin had an uneventful stay, whereas the second twin needed prolonged continuous positive airway pressure and indomethacin for patent ductus arteriosus. Both of them developed LSV. The clinical significance of this condition on the neuro-developmental outcome of a neonate has not yet been fully determined.  相似文献   
66.
BACKGROUND: In allergic conditions, the degree of skin test reactivity does not always correlate with the severity of clinical symptoms. Additional factors may contribute to the reported symptom severity. OBJECTIVES: To investigate the association between the magnitude of the skin prick test (SPT) response and the reported symptom severity in patients with allergic rhinitis and the possible modifying role of psychological factors. METHODS: One hundred four patients with allergic rhinitis and 23 with non-allergic rhinitis, classified according to their SPT response to 19 aeroallergens, were asked to rate the severity of five symptoms and to indicate whether their symptoms intensified on exposure to five common aeroallergens. They also completed a psychological questionnaire. Results Reported symptom severity of allergic rhinitis did not correlate with weal size for any of the aeroallergens tested or with the number of positive responses on SPT. It was not related to patient age, sex, or education. The reported symptoms severity correlated positively (0.29, P < 0.01) with reported symptom intensification on exposure to allergens. Moreover, both outcomes were positively associated with the psychological factors of hypochondriasis (0.20, P < 0.05 and 0.18, P < 0.05, respectively), and somatic awareness (0.24, P < 0.05 and 0.33, P < 0.01, respectively), but not with neuroticism. CONCLUSIONS: The severity of symptoms experienced by patients with allergic rhinitis is apparently not related to the magnitude of SPT response, but rather to psychological factors of hypochondriasis and somatic awareness. Physicians should be aware of the contribution of psychological factors to patient perceptions of the intensity of symptoms and of the intensification of symptoms on their exposure to allergens.  相似文献   
67.
68.
69.
70.
Weaver mutant mice are characterized by a decrease in striatal dopamine (DA), which is associated with a progressive loss of DA neurones in the substantia nigra. This mutant thus provides the opportunity to examine the functional effects of DA neurones grafted to the striatum in a genetic model of parkinsonism. Ventral mesencephalic tissue from normal foetuses was placed on the surface of the right dorsal striatum of adult weaver mutants. After grafting, animals were tested for methamphetamine-induced circling behaviour. Mutants with DA containing grafts displayed a significant circling bias toward the left, non-grafted side. Mutants without grafts did not display any rotational bias to either side. These results demonstrate that grafted DA containing neurones establish a functional innervation of the weaver striatum and suggest that grafting of neural tissue is a viable approach in restoring function in genetic degenerative disorders of the nigrostriatal system.  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