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   20600篇
  免费   1510篇
  国内免费   68篇
耳鼻咽喉   242篇
儿科学   679篇
妇产科学   486篇
基础医学   2994篇
口腔科学   956篇
临床医学   2386篇
内科学   3935篇
皮肤病学   402篇
神经病学   2007篇
特种医学   416篇
外科学   1853篇
综合类   263篇
一般理论   12篇
预防医学   2451篇
眼科学   439篇
药学   1366篇
中国医学   89篇
肿瘤学   1202篇
  2023年   197篇
  2022年   387篇
  2021年   738篇
  2020年   449篇
  2019年   670篇
  2018年   704篇
  2017年   515篇
  2016年   520篇
  2015年   618篇
  2014年   811篇
  2013年   1019篇
  2012年   1627篇
  2011年   1684篇
  2010年   864篇
  2009年   748篇
  2008年   1329篇
  2007年   1239篇
  2006年   1190篇
  2005年   1118篇
  2004年   952篇
  2003年   882篇
  2002年   864篇
  2001年   217篇
  2000年   216篇
  1999年   197篇
  1998年   182篇
  1997年   124篇
  1996年   124篇
  1995年   106篇
  1994年   102篇
  1993年   95篇
  1992年   123篇
  1991年   119篇
  1990年   121篇
  1989年   84篇
  1988年   107篇
  1987年   110篇
  1986年   96篇
  1985年   93篇
  1984年   89篇
  1983年   86篇
  1982年   56篇
  1981年   52篇
  1980年   44篇
  1979年   51篇
  1978年   44篇
  1977年   34篇
  1973年   31篇
  1972年   29篇
  1970年   34篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
The object of this enquiry was to obtain some idea of the mortality of untreated sleeping sickness in two non-adjacent districts in Northern Nigeria. The method employed was to obtain data, by methodical questioning of every householder, from which the crude death and other rates could be calculated over a preceding period, and be correlated with the known incidence of sleeping sickness. The figures were worked out village by village, and the villages then combined into groups of sufficient size to make the numbers significant.In the first district, Igabi, a close correlation was obtained, the death rate rising from 71.4 per 1,000 with a sleeping sickness incidence of 18.6 per cent., to 104 per 1,000 with a sleeping sickness incidence of 28.6 per cent. In other words an additional death occurred for approximately every additional three people infected. The infantile mortality rate also showed a close correlation with the sleeping sickness incidence. As infants were not found to be infected, this result was unexpected. The reasons for it are discussed. The birth rate showed no definite correlation.In the second district, Kankara, no correlation was found to exist, and the conclusion is drawn that, during the period under review, sleeping sickness was not fatal; the patients must either have harboured a mild chronic infection carrying no threat to life, or have been undergoing spontaneous cure.The clinical types of the cases found are described. They are similar in the two districts, and would not have been suspected of having so different a prognosis.It is pointed out that Igabi lies in the middle of a sleeping sickness belt, and it is suggested that the virulence of the disease in this district may be accounted for by the very free means of communication which exist, and by the movement in the past of large gangs of labour, tending to disseminate many different strains of trypanosome imported from outside. The infection in Kankara, on the other hand, was probably of later, though not very recent, introduction; and as the district is situated on the very edge of the belt and is traversed by no main roads or railways, the possibility of a multiplicity of strains existing is very much less. If this conclusion is correct, it emphasizes the necessity of careful sleeping sickness control measures in areas which may be opened up in the future.The mean birth rate found in Igabi was 64.7 per 1,000; and the mean death rate 84.2. The corresponding figures for Kankara were 44.1 and 23.6. The reliability of these figures is discussed.  相似文献   
32.
33.
INTRODUCTION: Angiotensin (Ang) IV enhances learning and memory in rats but there are strain differences in its effects in mice. Oxytocin (OT) also influences learning and memory in rats and mice and, in the light of the proposed effects of Ang IV on oxytocinase, the hypothesis that the effects of Ang IV on cognition in mice involve OT was tested. MATERIALS AND METHODS: The effects of Ang IV and OT, alone and combined, were determined in rat isolated uterine smooth muscle and in object recognition and forced swim tests in BKW mice. RESULTS: Ang potentiated the contractile effects of OT in the uterus. Neither peptide had any effect on object recognition nor locomotor activity. Ang IV had no effect in the forced swim test but abolished the effects of OT. CONCLUSIONS: Ang IV influences the actions of OT in vitro and in vivo, possibly by inhibition of oxytocinase, but the lack of effect of Ang IV on object recognition in BKW mice is unlikely to be a consequence of a deficiency endogenous OT. Unlike OT, Ang IV alone has no effect on learned helplessness in the forced swim test, an effect often used to predict potential antidepressant efficacy in humans.  相似文献   
34.
Short-chain alkyl esters of L-dopa were administered to rats and mice via oral and rectal routes. Plasma L-dopa esters and L-dopa were determined in the systemic and portal circulation by HPLC. A comparison of isopropyl, butyl, and 4-hydroxybutyl esters of L-dopa demonstrated significantly higher levels of the esters in both systemic and portal blood samples following rectal administration than following oral administration. In most cases, oral administration resulted in nondetectable (<0.01 µg/ml) levels of the esters in plasma. Correspondingly, the plasma levels of L-dopa itself were consistently higher following rectal administration. At very high oral doses (500 mg L-dopa equivalents/kg body weight), systemic plasma levels of the butyl ester could be detected (1.25 µg/ml at 10 min), which might indicate saturation of the esterase activity of the small intestine. These studies indicate that the systemic availability of L-dopa from short-chain alkyl esters of L-dopa may be best optimized by rectal administration, which avoids the relatively high esterase activity characteristic of the small intestine.  相似文献   
35.
36.
37.
Administration of an elemental diet to rats given methotrexate (MTX), 20 mg/kg intraperitoneally (ip), results in 100% mortality from severe enterocolitis. Previous studies indicate that glutamine (GLN), which is not present in elemental diets, is the preferred oxidative substrate for the gut and may facilitate intestinal recovery after injury. This study investigated the effects of a glutamine-supplemented elemental diet (GLN-ED) on nutritional status, intestinal morphometry, bacterial translocation and survival in this lethal model of intestinal injury. Three experiments were performed. In the first experiment, rats received an intragastric elemental diet supplemented with either 2% GLN or an equivalent amount of glycine (Control). After 4 days animals received either MTX, 20 mg/kg ip, or saline ip and were killed 3 days later. The GLN-ED resulted in significantly decreased weight loss, improved nitrogen retention, and increased mucosal weight, protein, and DNA content of the jejunum and colon. In the second experiment rats were assigned to diet as in the first experiment, but all animals received MTX. Control diet animals died within 120 hrs of MTX administration. The GLN-ED group had significantly longer survival time and decreased mortality. In the third experiment animals were assigned to diet and MTX as in the first experiment. Ninety-six hrs later aortic blood cultures revealed enteric bacteremia in animals administered MTX. GLN-ED resulted in a significant reduction in the incidence of bacteremia. These experiments showed that a GLN-ED significantly improved nutritional status, decreased intestinal injury, decreased bacterial translocation, and resulted in improved survival in a lethal model of enterocolitis.  相似文献   
38.
BACKGROUND: A subgroup of children with obsessive-compulsive and tic disorders are proposed to have an infectious trigger. The purpose of this study was to investigate the relationship between group A streptococcal titers and symptom fluctuations in children with a clinical course resembling that described for pediatric autoimmune neuropsychiatric disorders associated with streptococcus. METHODS: Twenty-five children with obsessive-compulsive disorder and/or tic disorder were evaluated for neuropsychiatric severity and group A streptococcal antibody titers (streptolysin O, deoxyribonuclease B, and carbohydrate A) at 6-week intervals for > or = six consecutive evaluations (total visits=277). RESULTS: Children with large symptom fluctuations (n=15) were compared with children without dramatic fluctuations (n=10). Co-movements of obsessive-compulsive/tic severity and group A streptococcal antibodies were assessed. In subjects with large symptom changes, positive correlations were found between streptococcal titers and obsessive-compulsive severity rating changes (p=.0130). These subjects were also more likely to have elevated group A streptococcal titers during the majority of observations (p=.001). Tic symptom exacerbations occurred more often in the fall/winter months than spring/summer months (p=.03). CONCLUSIONS: Patients with marked obsessive-compulsive/tic symptom changes may be characterized by streptococcal titer elevations and exhibit evidence of seasonal tic exacerbations.  相似文献   
39.
在了解及处理坚持用药的情况较差时,医生往往遇到很多困难。困扰医生的一个主要问题是,如何护理患有急性或危及生命的疾病而不能长期坚持治疗的儿童。对医生来说,更难的是如何了解父母何时不能为子女提供适当的护理。近30%~70%的患慢性疾病者,因为治疗时间长、服用的药物种类多及症状时有缓解而不能坚持用药。临床经验表明,患有慢性疾病,如囊性纤维化、癫痫、哮喘、糖尿病患者坚持用药的情况较差。  相似文献   
40.
PURPOSE: Hypothalamic hamartoma (HH) related epilepsy presents with gelastic seizures (GS), other seizure types and cognitive deterioration. Although seizure origin in GS has been well established, non-GS are poorly characterized. Their relationship with the HH and cognitive deterioration remains poorly understood. We analyzed seizure type, spread pattern in non-GS and their relationship with the epileptic syndrome in HH. METHODS: We documented all current seizure types in six adult patients with HH-epilepsy with video-EEG monitoring, characterized clinical-electrographic features of gelastic and non-gelastic seizures and correlated these findings with cognitive profile, as well as MRI and ictal SPECT data. RESULTS: Only four seizure types were seen: GS, complex partial (CPS), tonic seizures (TS) and secondarily generalized tonic-clonic seizures (sGTC). An individual patient presented either CPS or TS, but not both. GS progressed to CPS or TS, but not both. Ictal patterns in GS/TS and in GS/CPS overlapped, suggesting ictal spread from the HH to other cortical regions. Ictal SPECT patterns also showed GS/TS overlap. Patients with GS-CPS presented a more benign profile with preserved cognition and clinical-EEG features of temporal lobe epilepsy. Patients with GS-TS had clinical-EEG features of symptomatic generalized epilepsy, including mental deterioration. CONCLUSIONS: Video-EEG and ictal SPECT findings suggest that all seizures in HH-related epilepsy originate in the HH, with two clinical epilepsy syndromes: one resembling temporal lobe epilepsy and a more catastrophic syndrome, with features of a symptomatic generalized epilepsy. The epilepsy syndrome may be determined by HH size or by seizure spread pattern.  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