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   3111篇
  免费   202篇
  国内免费   21篇
耳鼻咽喉   33篇
儿科学   103篇
妇产科学   61篇
基础医学   456篇
口腔科学   33篇
临床医学   339篇
内科学   645篇
皮肤病学   21篇
神经病学   218篇
特种医学   176篇
外科学   607篇
综合类   26篇
现状与发展   1篇
预防医学   178篇
眼科学   45篇
药学   170篇
中国医学   3篇
肿瘤学   219篇
  2023年   13篇
  2022年   23篇
  2021年   62篇
  2020年   41篇
  2019年   66篇
  2018年   75篇
  2017年   63篇
  2016年   66篇
  2015年   92篇
  2014年   117篇
  2013年   158篇
  2012年   254篇
  2011年   255篇
  2010年   142篇
  2009年   140篇
  2008年   229篇
  2007年   217篇
  2006年   191篇
  2005年   209篇
  2004年   181篇
  2003年   164篇
  2002年   177篇
  2001年   26篇
  2000年   18篇
  1999年   15篇
  1998年   33篇
  1997年   16篇
  1996年   8篇
  1995年   20篇
  1994年   21篇
  1993年   16篇
  1992年   17篇
  1991年   7篇
  1990年   7篇
  1989年   8篇
  1988年   10篇
  1987年   9篇
  1986年   9篇
  1985年   10篇
  1984年   10篇
  1983年   8篇
  1982年   16篇
  1981年   10篇
  1980年   14篇
  1979年   9篇
  1978年   8篇
  1977年   6篇
  1976年   6篇
  1974年   6篇
  1961年   5篇
排序方式: 共有3334条查询结果,搜索用时 453 毫秒
51.
AIMS: To report the natural history of autochthonous hepatitis E and hepatitis E virus (HEV) IgG seroprevalence in Southwest England. METHODS: Patients with unexplained hepatitis were tested for hepatitis E and cases followed until recovery or death. Five hundred blood donors, 336 individuals over the age of 60 years and 126 patients with chronic liver disease were tested for HEV IgG. RESULTS: Forty cases of autochthonous hepatitis E (genotype 3) were identified. Hepatitis E was anicteric in 25% of cases and usually caused a self-limiting hepatitis predominantly in elderly Caucasian males. Six of 40 had a significant complication and three patients died, two of who had previously undiagnosed cirrhosis. Hepatitis E shows a seasonal variation with peaks in the spring and summer and no cases in November and December. HEV IgG prevalence increases with age, is more common in men and is 16% in blood donors, 13% in patients with chronic liver disease and 25% in individuals over 60 years. CONCLUSION: Autochthonous hepatitis E is more common than previously recognized, and should be considered in the differential diagnosis in patients with hepatitis, whatever their age or travel history. It carries a significant morbidity and when seen in the context of chronic liver disease carries an adverse prognosis.  相似文献   
52.
Clinical and angiographic or autopsy data, or both, on three children with a subdivided left atrium (cor triatriatum) and an associated endocardial cushion defect are reviewed. (One child had ostium primum defect, and two had complete atrioventricular [A-V] canal.) A fourth patient demonstrates the difficulties in differentiating subdivided left atrium from supravalve mitral stenosis in the presence of an endocardial cushion defect. The clinical findings are greatly influenced by the endocardial cushion defect. A pressure gradient between the pulmonary wedge and (left or right) ventricular end-diastolic pressures in patients with an endocardial cushion defect indicates pulmonary venous obstruction and should alert one to the possibility of these combined lesions. The exact diagnosis is made with injections of angiographic contrast medium into the proximal and distal left atrial chambers, to document the respective relations of the pulmonary veins, left atrial appendage and A-V valves to these atrial chambers. All three patients with an endocardial cushion defect and a subdivided left atrium had an associated patent ductus arteriosus. The common association of subdivided left atrium with intracardiac, pulmonary venous and aortic anomalies is again demonstrated.  相似文献   
53.
Five system barriers to achieving ultrasafe health care   总被引:1,自引:0,他引:1  
Although debate continues over estimates of the amount of preventable medical harm that occurs in health care, there seems to be a consensus that health care is not as safe and reliable as it might be. It is often assumed that copying and adapting the success stories of nonmedical industries, such as civil aviation and nuclear power, will make medicine as safe as these industries. However, the solution is not that simple. This article explains why a benchmarking approach to safety in high-risk industries is needed to help translate lessons so that they are usable and long lasting in health care. The most important difference among industries lies not so much in the pertinent safety toolkit, which is similar for most industries, but in an industry's willingness to abandon historical and cultural precedents and beliefs that are linked to performance and autonomy, in a constant drive toward a culture of safety. Five successive systemic barriers currently prevent health care from becoming an ultrasafe industrial system: the need to limit the discretion of workers, the need to reduce worker autonomy, the need to make the transition from a craftsmanship mindset to that of equivalent actors, the need for system-level (senior leadership) arbitration to optimize safety strategies, and the need for simplification. Finally, health care must overcome 3 unique problems: a wide range of risk among medical specialties, difficulty in defining medical error, and various structural constraints (such as public demand, teaching role, and chronic shortage of staff). Without such a framework to guide development, ongoing efforts to improve safety by adopting the safety strategies of other industries may yield reduced dividends. Rapid progress is possible only if the health care industry is willing to address these structural constraints needed to overcome the 5 barriers to ultrasafe performance.  相似文献   
54.
Objectives: To determine the risk of recurrent anal sphincter rupture (ASR), and compare the risk of anal incontinence (AI) after recurrent ASR, with that seen in women with previous ASR who deliver by caesarean section or vaginally without sustaining a recurrent ASR.

Methods: Women with recurrent ASR between January 2000 and June 2011 were identified at two delivery wards in Copenhagen. The women answered a questionnaire with a validated scoring system for AI (St. Mark`s score), and the results were compared with those obtained in two control groups: women with subsequent uncomplicated vaginal delivery or caesarean section.

Results: There were 93?437 vaginal deliveries. ASR occurred in 5.5% (n?=?2851) of the nulliparous and 1.5% (n?=?608) of the multiparous women. Recurrent ASR occurred in 8% (n?=?49) of whom 50% reported symptoms of AI. We found no difference in the occurrence of AI between women with recurrent ASR, and those who delivered vaginally without repeat ASR (p?=?0.37; OR?=?2.0) or by caesarean section (p?=?0.77; OR?=?1.3).

Conclusion: Women with a past history of ASR have an 8% risk of recurrence. AI affects half of the women with recurrent ASR. Larger studies are required to confirm our findings.  相似文献   

55.
Resistance toward imatinib and other BCR/ABL tyrosine kinase inhibitors remains an increasing clinical problem in the treatment of advanced stages of chronic myeloid leukemia (CML). We recently have identified the heat shock protein 32 (Hsp32)/heme oxygenase-1 (HO-1) as a BCR/ABL-dependent survival molecule in CML cells. We here show that silencing Hsp32/HO-1 in CML cells by an siRNA approach results in induction of apoptosis. Moreover, targeting Hsp32/HO-1 by either pegylated zinc protoporphyrine (PEG-ZnPP) or styrene maleic acid-micelle-encapsulated ZnPP (SMA-ZnPP) resulted in growth inhibition of BCR/ABL-transformed cells. The effects of PEG-ZnPP and SMA-ZnPP were demonstrable in Ba/F3 cells carrying various imatinib-resistant mutants of BCR/ABL, including the T315I mutant, which exhibits resistance against all clinically available BCR/ABL tyrosine kinase inhibitors. Growth-inhibitory effects of PEG-ZnPP and SMA-ZnPP also were observed in the CML-derived human cell lines K562 and KU812 as well as in primary leukemic cells obtained from patients with freshly diagnosed CML or imatinib-resistant CML. Finally, Hsp32/HO-1-targeting compounds were found to synergize with either imatinib or nilotinib in producing growth inhibition in imatinib-resistant K562 cells and in Ba/F3 cells harboring the T315I mutant of BCR/ABL. In summary, these data show that HO-1 is a promising novel target in imatinib-resistant CML.  相似文献   
56.
57.
Between January 1978 and December 1982 successful sequential chromosome analyses were carried out on bone marrow cells of five patients previously treated for Hodgkin's lymphoma (HL) presenting unexplained cytopenia or pancytopenia during follow-up. All patients had concurrent morphological examination of bone marrow specimens showing signs of dysplasia and/or hypoplasia, without leukaemic infiltrate. Six other patients treated for HL who had normal haematological parameters served as controls. All the patients with unexplained cytopenias had clonal chromosome abnormalities; monosomy for chromosome No. 5 was the most frequent. No abnormalities were detected in the control group. Two patients have evolved to resistant leukaemia, one died of sepsis before leukaemic conversion while severely neutropenic, and two are in full marrow and cytogenetic recovery after aggressive anti-leukaemic treatment in the pre-leukaemic phase. Our data suggest that cytogenetic studies may be of crucial value in detecting therapy-induced preleukaemia (t-PL) at an early stage of its evolution and in planning appropriate therapy before the establishment of overt leukaemia.  相似文献   
58.
Two cases of amyloidosis were observed in a personal series of 42 patients with the adult from of Still's disease. Two other cases have been previously reported in the literature. In the first case, amyloidosis occurred 18 months after the onset of the disease and involved the kidneys and gastrointestinal tract with a fatal outcome in 6 months. In the second case, renal amyloidosis was observed 4 years after the onset of Still's disease and progressed to renal failure in 7 months, necessitating chronic haemodialysis. These cases show that the adult form of Still's disease may rarely be complicated by amyloidosis, the prognosis of which is particularly poor.  相似文献   
59.
Ten groups of calves were used to study the changes in activity levels and distribution of seven hydrolases in the intestinal mucosa during development and weaning. The calves in the first group were sacrificed at birth while those in the remaining nine groups were either milk-fed until slaughter on days 2, 7, 28, 56, 70, and 119; or weaned between days 28 and 56 and then slaughtered on days 56, 70, and 119, respectively. The small intestine was immediately cut off and divided into five segments, ie, duodenum, proximal jejunum, median jejunum, distal jejunum, and ileum. In the milk-fed animals, the activity levels of aminopeptidases A and N, alkaline phosphatase, lactase, and isomaltase were maximum at 2 days of age, and then declined sharply between days 2 and 7 but did not change significantly thereafter. By contrast, the maltase activity increased between days 7 and 119, while no sucrase activity was detected. Weaning resulted in a decrease in the activity of lactase and an increase in that of aminopeptidase N, maltase, and isomaltase. The distribution of all these enzymes along the small intestine was slightly influenced by age but not at all by weaning.  相似文献   
60.
Venous ulcers are the most common form of leg ulcers, which induce lesion because of the loss of substances deposited on the damaged skin. Isosorbide dinitrate is a vasodilator with effects on both arteries and veins and induces opening of vascular layers. The objective is to study the effects of isosorbide dinitrate-spray in patients with chronic venous ulcers. Forty-five patients of both sexes with chronic venous ulcers were randomized to receive isosorbide dinitrate or placebo sprays daily for 3 months. The ulcers were measured and clinical characteristics were taken every 15 days during the treatment. Patients treated with isosorbide dinitrate showed an improvement of the ulcerated area (71.29%) compared with patients treated with placebo (54.35%). The histopathological study indicated an increment in the number of hypertrophic and hyperplasic capillaries. Macroscopically, the isosorbide dinitrate-treatment showed the best results, but it was only during the first 6 weeks of treatment. Patients with chronic venous ulcer receiving isosorbide dinitrate spray showed improvement.  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