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   879篇
  免费   51篇
  国内免费   98篇
耳鼻咽喉   5篇
儿科学   46篇
妇产科学   5篇
基础医学   86篇
口腔科学   26篇
临床医学   145篇
内科学   245篇
皮肤病学   11篇
神经病学   68篇
特种医学   119篇
外科学   51篇
综合类   41篇
预防医学   46篇
眼科学   7篇
药学   92篇
肿瘤学   35篇
  2023年   3篇
  2021年   8篇
  2020年   3篇
  2019年   6篇
  2018年   6篇
  2017年   8篇
  2016年   10篇
  2015年   11篇
  2014年   18篇
  2013年   28篇
  2012年   29篇
  2011年   33篇
  2010年   42篇
  2009年   35篇
  2008年   24篇
  2007年   67篇
  2006年   29篇
  2005年   43篇
  2004年   13篇
  2003年   16篇
  2002年   19篇
  2001年   26篇
  2000年   23篇
  1999年   22篇
  1998年   45篇
  1997年   39篇
  1996年   31篇
  1995年   36篇
  1994年   29篇
  1993年   38篇
  1992年   19篇
  1991年   17篇
  1990年   27篇
  1989年   34篇
  1988年   32篇
  1987年   19篇
  1986年   21篇
  1985年   17篇
  1984年   10篇
  1983年   10篇
  1982年   8篇
  1981年   5篇
  1980年   10篇
  1979年   6篇
  1978年   6篇
  1977年   9篇
  1976年   9篇
  1973年   3篇
  1972年   4篇
  1967年   4篇
排序方式: 共有1028条查询结果,搜索用时 15 毫秒
11.
A 54-year-old man was treated with weekly 24-h infusion of high-dose 5-fluorouracil (2600 mg/m2) and leucovorin (100 mg/m2) for metastatic colon cancer. At first, he tolerated the treatment well and no significant toxicity was identified. After a total of eight courses of treatment, a stable disease was observed, but mild shortness of breath was found on occasion. The patient had no previous history of cardiac disease and the heart performance assessed by left ventricular ejection fraction before treatment was normal. Unfortunately, acute pulmonary edema with lethal cardiogenic shock occurred during the ninth course of treatment, in spite of intensive medical treatment. The chest X-ray showed extreme cardiomegaly. Repeated assessment of his heart function by echocardiogram and ventricular ejection fraction revealed a very poor cardiac performance. Toxic cardiogenic shock during weekly 24-h infusion of high-dose 5-fluorouracil and leucovorin is extremely rare. To the best of our knowledge, no case has been reported in the English literature. We report a case and the relevant literature about the incidence, clinical picture and possible pathophysiology on 5-fluorouracil-related cardioxicity is reviewed.   相似文献   
12.
A 30-year-old male patient with paranoid schizophrenia was on clozapine therapy for more than five years. Discontinuation of clozapine and an attempt to change his medication to sertindole has led to serious psychotic and somatic symptoms. After readministration of clozapine the psychotic symptoms rapidly disappeared. The patient was monitored by BPRS and PANSS positive and negative scale. Also clinical and labor parameters of the patient were monitored. The change of his medication from clozapine to sertindole was unsuccessful. This case report suggests that although atypical antipsychotics may be generally different from the classical neuroleptic drugs, there are also significant differences among the atypical antipsychotic drugs in their effects on the receptors of the central nervous system. Therefore the change of clozapine to another atypical antipsychotic medication in the clinical practice should be cross-tapered and the symptoms of withdrawal closely monitored.  相似文献   
13.
白首乌化学成分的研究   总被引:4,自引:0,他引:4  
自白首乌主要品种耳叶牛皮消(Cynanchum auriculatum Royle ex Wight)根中首次分得三个已知甾体酯型甙元:告达亭(caudatin),开德甙元(kidjolanin),萝藦甙元(Metaplexigenin)和一种新的二苯酮衍生物(Ⅳ),经光谱分析推定其结构为2,6,2′,5′-四羟基,3-乙酰基,6′-甲基二苯酮,命名白首乌二苯酮。  相似文献   
14.
Mangiferin (1,3,6,7-tetrahydroxy-2-[3,4,5-trihydroxy-6-(hydroxymethyl)oxan-2-yl] -xanthen-9-one, CAS 4773-96-0), a naturally occurring glucosylxanthone, is widely distributed in higher plants and a constituent of folk medicine. In the present study the effect of systemic administration of mangiferin on behavioural outcomes of neurological function in normal rats was investigated. A single intraperitoneal injection of mangiferin (10, 50 and 100 mg/kg body weight) immediately post-training produced an impairment of long-term memory for aversive training and a reduced freezing in a dose independent manner, when given immediately post-training. The administration of mangiferin 6 h post-training did not affect fear memory. The results indicate that mangiferin might induce deficits of emotionally motivated memory.  相似文献   
15.
白首乌化学成分的研究   总被引:11,自引:0,他引:11  
自白首乌主要品种耳叶牛皮消(Cynanchum auriculatum Royle ex Wight)根中首次分得三个已知甾体酯型甙元:告达亭(caudatin),开德甙元(kidjolanin),萝藦甙元(Metaplexigenin)和一种新的二苯酮衍生物(Ⅳ),经光谱分析推定其结构为2,6,2′,5′-四羟基,3-乙酰基,6′-甲基二苯酮,命名白首乌二苯酮。  相似文献   
16.
17.
The methane-rich, hydrothermally heated sediments of the Guaymas Basin are inhabited by thermophilic microorganisms, including anaerobic methane-oxidizing archaea (mainly ANME-1) and sulfate-reducing bacteria (e.g., HotSeep-1 cluster). We studied the microbial carbon flow in ANME-1/ HotSeep-1 enrichments in stable-isotope–probing experiments with and without methane. The relative incorporation of 13C from either dissolved inorganic carbon or methane into lipids revealed that methane-oxidizing archaea assimilated primarily inorganic carbon. This assimilation is strongly accelerated in the presence of methane. Experiments with simultaneous amendments of both 13C-labeled dissolved inorganic carbon and deuterated water provided further insights into production rates of individual lipids derived from members of the methane-oxidizing community as well as their carbon sources used for lipid biosynthesis. In the presence of methane, all prominent lipids carried a dual isotopic signal indicative of their origin from primarily autotrophic microbes. In the absence of methane, archaeal lipid production ceased and bacterial lipid production dropped by 90%; the lipids produced by the residual fraction of the metabolically active bacterial community predominantly carried a heterotrophic signal. Collectively our results strongly suggest that the studied ANME-1 archaea oxidize methane but assimilate inorganic carbon and should thus be classified as methane-oxidizing chemoorganoautotrophs.  相似文献   
18.
Emergency departments and crowding in United States teaching hospitals   总被引:27,自引:1,他引:27  
STUDY OBJECTIVES: To assess the extent and distribution of hospital and emergency department crowding nationally. DESIGN: The research design consisted of a mailed questionnaire disseminated in the fall of 1988 to the member institutions of the National Association of Public Hospitals (NAPH) and the Council of Teaching Hospitals (COTH). TYPE OF PARTICIPANTS: Study participants included hospital administrators and ED directors from 239 of the non-Veterans Administration, general acute care, US members of COTH and NAPH. MEASUREMENTS: Key measures of hospital and ED crowding including mean ED holding times for floor and ICU beds. MAIN RESULTS: Three fourths of responding hospitals reported increases in ED visits over the preceding three years. Mean ED holding times for admitted patients were 3.5 hours (median, 2.0 hours) for a floor bed and 2.9 hours (median, 1.5 hours) for an ICU bed. Half of all hospitals noted maximum waits for floor and ICU beds of ten hours or more and seven hours or more, respectively. Measures taken by hospitals to manage crowding during August 1988 included restricting access to some types of patients (mean, 3.6 days), actively transferring patients to other hospitals (mean, 2.2 days), transfer refusal (mean, 2.8 days), and total ambulance diversion (mean, 1.6 days). CONCLUSIONS: Our study strongly suggests that ED crowding is not an isolated phenomenon; ED crowding and its attendant problems appear to affect hospitals with similar adverse effects regardless of ownership. Although our results suggest that ED crowding is concentrated in metropolitan areas and in a smaller subset of hospitals, we found instances of crowding among hospitals nationwide.  相似文献   
19.
20.
BRCA1 and BRCA2 are major breast cancer susceptibility genes. Nineteen single nucleotide polymorphisms (SNPs) at 18 loci have been associated with breast cancer. We aimed to determine whether these predict breast cancer incidence in women with BRCA1/BRCA2 mutations. BRCA1/2 mutation carriers identified through the Manchester genetics centre between 1996 and 2011 were included. Using published odds ratios (OR) and risk allele frequencies, we calculated an overall breast cancer risk SNP score (OBRS) for each woman. The relationship between OBRS and age at breast cancer onset was investigated using the Cox proportional hazards model, and predictive ability assessed using Harrell's C concordance statistic. In BRCA1 mutation carriers we found no association between OBRS and age at breast cancer onset: OR for the lowest risk quintile compared to the highest was 1.20 (95% CI 0.82–1.75, Harrell's C = 0.54), but in BRCA2 mutation carriers the association was significant (OR for the lowest risk quintile relative to the highest was 0.47 (95% CI 0.33–0.69, Harrell's C = 0.59). The 18 validated breast cancer SNPs differentiate breast cancer risks between women with BRCA2 mutations, but not BRCA1. It may now be appropriate to use these SNPs to help women with BRCA2 mutations make maximally informed decisions about management options.  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