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   2159758篇
  免费   153987篇
  国内免费   2838篇
耳鼻咽喉   29505篇
儿科学   70370篇
妇产科学   59061篇
基础医学   314901篇
口腔科学   60368篇
临床医学   197368篇
内科学   414252篇
皮肤病学   47892篇
神经病学   169156篇
特种医学   82242篇
外国民族医学   461篇
外科学   315848篇
综合类   44630篇
现状与发展   3篇
一般理论   781篇
预防医学   167088篇
眼科学   49359篇
药学   165371篇
  11篇
中国医学   4524篇
肿瘤学   123392篇
  2018年   22620篇
  2017年   17510篇
  2016年   19495篇
  2015年   22157篇
  2014年   30638篇
  2013年   45958篇
  2012年   62707篇
  2011年   66579篇
  2010年   38990篇
  2009年   37141篇
  2008年   62597篇
  2007年   66962篇
  2006年   67234篇
  2005年   64982篇
  2004年   62351篇
  2003年   59931篇
  2002年   57947篇
  2001年   104437篇
  2000年   106844篇
  1999年   89672篇
  1998年   23944篇
  1997年   21465篇
  1996年   21658篇
  1995年   20351篇
  1994年   18845篇
  1993年   17701篇
  1992年   69539篇
  1991年   67588篇
  1990年   66038篇
  1989年   63843篇
  1988年   58459篇
  1987年   57044篇
  1986年   54199篇
  1985年   51053篇
  1984年   38058篇
  1983年   32748篇
  1982年   18785篇
  1981年   16725篇
  1979年   35319篇
  1978年   24970篇
  1977年   21554篇
  1976年   19450篇
  1975年   21437篇
  1974年   25623篇
  1973年   25011篇
  1972年   23820篇
  1971年   22298篇
  1970年   20827篇
  1969年   19870篇
  1968年   18170篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
991.
Seventy seven antral biopsies were collected from patients attending endoscopy clinic at King Khalid University Hospital, Riyadh, Saudi Arabia during a period of six months between December 1988 to May 1989. Of these 69 (89.6%) showed chronic gastritis as well as Helicobacter-like organisms (HLOs) in the biopsy specimens while 63 (81.8%) of biopsies grew Helicobacter pylori on culture. These findings indicate a good correlation between the histological diagnosis of chronic gastritis and isolation of H. pylori on culture.  相似文献   
992.
993.
Evidence indicates that endogenous opioid peptides and glucocorticoids participate in the control of cardiovascular regulation during hemorrhagic shock. In the present study, we investigated a possible interaction between brain opioid peptides and adrenal corticosteroids regarding the control of arterial pressure during hemorrhage. The bleeding volumes required to lower arterial pressure to 80, 60 and 40 mmHg were studied in anesthetized sham-operated (SHAM) and adrenalectomized (ADX) rats. I.c.v. administration of 10 micrograms of naloxone resulted in a significant increase in the bleeding volume required to lower arterial pressure from 60 to 40 mmHg in SHAM animals, whereas no effect of naloxone was observed in ADX animals. Replacement therapy with a 100% corticosterone pellet (100 mg, s.c.), but not with a 12.5% corticosterone pellet (12.5 mg corticosterone and 87.5 mg cholesterol, s.c.), resulted in an effect of naloxone on the bleeding volume in ADX animals. The effect of replacement therapy could be inhibited by i.c.v. pretreatment with the synthetic glucocorticoid receptor antagonist, RU38486 (100 ng). These data suggest that (1) opioid mechanisms are involved in the regulation of blood pressure during hemorrhage, and (2) occupancy of glucocorticoid receptors is required for naloxone to exert its hemodynamic effect during hemorrhagic hypotension in ADX rats.  相似文献   
994.
Leukotriene C4 (LTC4) production in the guinea pig spinal cord following compression injury was determined by radioimmunoassay, in the same way thromboxane B2 (TXB2), a stable metabolite of thromboxane A2 (TXA2), was also measured. When the spinal cords were compressed under a 20 gram weight for 10 minutes, LTC4 levels reached peak values (2.2 +/- 0.4 pmol/g cord) 10 minutes after release, then gradually decreased until being undetectable 60 minutes later. TXB2 levels reached peak values (146.8 +/- 6.2 pmol/g cord) 5 minutes after the release from compression, the TXB2 level then gradually decreased, but remained at about 1/2 of the peak level even 60 minutes after the release. When the spinal cords were compressed with various weights, TXB2 production depended on the degree of compression, while LTC4 production was not affected by the compression injury. The LTC4 production confirmed in the injured spinal cords is suggestive of its relation to secondary disorders after spinal cord injury, spinal edema, in particular.  相似文献   
995.
Ninety-five patients out of total 190 cases of aluminium phosphide (ALP) poisoning, who exhibited ECG changes were studied for incidence, type and pattern of ECG abnormalities, their effect on mortality and their relationship with histopathology of heart. Its incidence in the present study was 50%. The arrhythmias, conduction disturbances and ischaemic pattern occurred more or less in equal frequency. Certain ECG abnormalities which had not been reported previously ie, early repolarisation syndrome, varied sino-atrial blocks, bradycardia-tachycardia syndrome and electrical alternans were observed in this study. The clinical profile of these cases was similar irrespective of whether patients had ECG abnormalities or not. Shock was the cardinal feature. There was no effect of ECG abnormalities on mortality. The mortality which was otherwise high, depended upon severity of poisoning, dose of poison consumed, duration of shock, failure of response of shock to resuscitative measures and severe hypomagnesaemia. The pathogenesis of ECG abnormalities is still obscure. Hypomagnesaemia was observed in all the 18 cases studied, irrespective of ECG abnormalities. However, these were common when hypomagnesaemia was severe. Hypoxaemia and shock were not the contributory factors for these abnormalities. Autopsy revealed stereotyped histopathological changes of toxic myocarditis independent of ECG findings.  相似文献   
996.
997.
Circulating immune complexes in pre-eclampsia.   总被引:3,自引:0,他引:3  
Serum samples from 20 non-pregnant women, 30 women with normal pregnancy and 50 women with pregnancy associated with pre-eclampsia were tested for circulating immune complexes using the polyethyleneglycol precipitation method. A highly significant positive correlation was found between circulating immune complexes and severe pre-eclampsia (BP greater than 140/90 mm Hg, albuminuria greater than 0.25 g/l). In contrast to this the difference in immune complex levels between non-pregnant subject, normal pregnancy cases and patients with mild pre-eclampsia was not statistically significant. A significant positive correlation was found between the level of circulating immune complexes and the severity of albuminuria. These findings suggest that circulating immune complexes, though not seeming to play an aetiological role in pre-eclampsia may very well be involved in its pathogenesis.  相似文献   
998.
A series of histamine H3 receptor agonists and the H3 receptor antagonist thioperamide were tested in the isolated guinea pig duodenum, to investigate the role of this new receptor subtype in the intestinal contractility. At the same time the selectivity of the different compounds for the various histamine receptor subtypes was investigated. In the presence of famotidine (10(-6) M) and thioperamide (10(-5) M), histamine, N alpha-methylhistamine (NMH) and (R)-alpha-methylhistamine (alpha-MH) exerted a concentration-dependent contractile effect through activation of H1 receptors; the ratio of potency was histamine = NMH greater than alpha-MH (this last compound was approximately 500 times less potent). In the presence of pyrilamine (10(-6) M) and thioperamide (10(-5) M), histamine, dimaprit and impromidine caused a slight contractile effect, showing a high degree of tachyphylaxis; this effect was abolished by tetrodotoxin (10(-6) M) and by famotidine (10(-6) M). alpha-MH was ineffective up to 10(-4) M. The H2 receptor agonists dimaprit (10(-4) to 10(-3) M) and impromidine (10(-6) to 10(-5) M) caused a relaxant effect on the contraction elicited by acetylcholine (ACh), BaCl2 and electrical stimulation. This effect, which was unaffected by famotidine, was not mimicked by alpha-MH and not reversed by thioperamide (10(-5) M). In the presence of pyrilamine (109-6) M) and famotidine (10(-6) M), histamine, NMH and alpha-MH inhibited the twitch responses to electrical stimulation, with EC50 values of 1.17 x 10(-7), 6.76 x 10(-8) and 2.45 x 10(-8) M, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
999.
1000.
Thirty outpatients with panic disorder (PD) were treated at an anxiety clinic using a symptom-focused approach. Thirteen (43%) had no history of major depressive disorder (MDD), 12 (40%) had a history of secondary MDD, and 5 (17%) had history of primary MDD. The outcome was equally good in patients with no history of MDD (77% had good or excellent outcomes) and patients with a history of secondary MDD (83% had good or excellent outcomes). Patients with a history of primary MDD had the worst outcomes. These findings agree with earlier studies showing that secondary MDD does not adversely affect prognosis of patients presenting for treatment of PD.  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