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   1141篇
  免费   68篇
  国内免费   61篇
耳鼻咽喉   8篇
儿科学   51篇
妇产科学   14篇
基础医学   133篇
口腔科学   66篇
临床医学   131篇
内科学   328篇
皮肤病学   16篇
神经病学   22篇
特种医学   105篇
外科学   97篇
综合类   21篇
预防医学   67篇
眼科学   6篇
药学   98篇
中国医学   3篇
肿瘤学   104篇
  2020年   9篇
  2019年   20篇
  2018年   21篇
  2017年   12篇
  2016年   18篇
  2015年   22篇
  2014年   36篇
  2013年   40篇
  2012年   32篇
  2011年   44篇
  2010年   45篇
  2009年   30篇
  2008年   43篇
  2007年   84篇
  2006年   29篇
  2005年   30篇
  2004年   19篇
  2003年   29篇
  2002年   29篇
  2001年   22篇
  2000年   19篇
  1999年   32篇
  1998年   40篇
  1997年   42篇
  1996年   26篇
  1995年   25篇
  1994年   32篇
  1993年   22篇
  1992年   15篇
  1991年   16篇
  1990年   16篇
  1989年   31篇
  1988年   33篇
  1987年   21篇
  1986年   18篇
  1985年   21篇
  1984年   13篇
  1982年   16篇
  1981年   18篇
  1980年   15篇
  1979年   10篇
  1978年   10篇
  1977年   10篇
  1976年   13篇
  1975年   9篇
  1974年   7篇
  1971年   7篇
  1968年   9篇
  1961年   6篇
  1960年   6篇
排序方式: 共有1270条查询结果,搜索用时 31 毫秒
21.
22.

Background  

Breathlessness causes significant burden in our community but the underlying socio-demographic and lifestyle factors that may influence it are not well quantified. This study aims to define these predictors of chronic breathlessness at a population level.  相似文献   
23.
Summary The negative inotropic effect of antiarrhythmic drugs is a major drawback in antiarrhythmic drug therapy, especially in patients with reduced contractile function of the left ventricle. The circulatory and myocardial effects of the new class I antiarrhythmic drug (a Na+ antagonist), cibenzoline (2 mg/kg i.v.), were investigated in 47 open-chest rats with normal and postischemic myocardium (3×4 minutes of global ischemia). Hemodynamic measurements in the intact circulation and isovolumic registrations (peak isovolumic left ventricular systolic pressure and peak isovolumic dP/dtmax) were compared to saline controls. In rats with postischemic myocardium, cibenzoline caused a significant (p<0.001) decrease in the cardiac output for 38%, in the dP/dtmax for 30%, and in the peak isovolumic dP/dtmax for 19% at the end of infusion (compared to the control). The heart rate was reduced by 22% (p<0.001), the mean aortic pressure by 22% (p<0.001), and the calculated systemic resistance by 20% (p<0.001). In contrast to the results with postischemic myocardium, no important changes in the hemodynamics were detectable after an identical dose in normal animals without left ventricular dysfunction. The results indicate that standard doses of the Na+ antagonist cibenzoline may induce significant cardiodepressant effects on postischemic left ventricles with reduced function.  相似文献   
24.
Long-term bone marrow cultures (LTBMC) from patients with multiple myeloma (MM) and normal donors were analyzed for immunophenotype and cytokine production. Both LTBMC adherent cells from myeloma and normal donor origin expressed CD10, CD13, the adhesion molecules CD44, CD54, vascular cell adhesion molecule 1, very late antigen 2 (VLA-2), and VLA- 5, and were positive for extracellular matrix components fibronectin, laminin, and collagen types 3 and 4. LTBMC from myeloma patients and normal donors spontaneously secreted interleukin-6 (IL-6). However, levels of IL-6 correlated with the stage of disease; highest levels of IL-6 were found in LTBMC from patients with active myeloma. To identify the origin of IL-6 production, LTBMC from MM patients and normal donors were cocultured with BM-derived myeloma cells and cells from myeloma cell lines. IL-6 was induced by plasma cell lines that adhered to LTBMC such as ARH-77 and RPMI-8226, but not by nonadhering cell lines U266 and FRAVEL. Myeloma cells strongly stimulated IL-6 secretion in cocultures with LTBMC adherent cells from normal donors and myeloma patients. When direct cellular contact between LTBMC and plasma cells was prevented by tissue-culture inserts, no IL-6 production was induced. This implies that intimate cell-cell contact is a prerequisite for IL-6 induction. Binding of purified myeloma cells to LTBMC adherent cells was partly inhibited by monoclonal antibodies against adhesion molecules VLA-4, CD44, and lymphocyte function-associated antigen 1 (LFA-1) present on the plasma cell. Antibodies against VLA-4, CD29, and LFA-1 also inhibited the induced IL-6 secretion in plasma cell-LTBMC cocultures. In situ hybridization studies performed before and after coculture with plasma cells indicated that LTBMC adherent cells produce the IL-6. These results suggest that the high levels of IL-6 found in LTBMC of MM patients with active disease are a reflection of their previous contact with tumor cells in vivo. These results provide a new perspective on tumor growth in MM and emphasize the importance of plasma cell-LTBMC interaction in the pathophysiology of MM.  相似文献   
25.

Objective

We aimed to investigate the effect of known heart disease on post‐out‐of‐hospital cardiac arrest (OHCA) survival outcomes, and its association with factors influencing survival.

Methods

This was an observational, retrospective study involving an OHCA database from seven Asian countries in 2009–2012. Heart disease was defined as a documented diagnosis of coronary artery disease or congenital heart disease. Patients with non‐traumatic arrests for whom resuscitation was attempted and with known medical histories were included. Differences in demographics, arrest characteristics and survival between patients with and without known heart disease were analysed. Multivariate logistic regression was performed to identify factors influencing survival to discharge.

Results

Of 19 044 eligible patients, 5687 had known heart disease. They were older (77 vs 72 years) and had more comorbidities like diabetes (40.9 vs 21.8%), hypertension (60.6 vs 36.0%) and previous stroke (15.2 vs 10.1%). However, they were not more likely to receive bystander cardiopulmonary resuscitation (P = 0.205) or automated external defibrillation (P = 0.980). On univariate analysis, known heart disease was associated with increased survival (unadjusted odds ratio 1.16, 95% confidence interval 1.03–1.30). However, on multivariate analysis, heart disease predicted poorer survival (adjusted odds ratio 0.76, 95% confidence interval 0.58–1.00). Other factors influencing survival corresponded with previous reports.

Conclusions

Known heart disease independently predicted poorer post‐OHCA survival. This study may provide information to guide future prospective studies specifically looking at family education for patients with heart disease and the effect on OHCA outcomes.  相似文献   
26.
27.
p16INK4A and p15INK4B gene deletions in primary leukemias   总被引:4,自引:0,他引:4  
The 9p21 locus has been deleted at a high frequency in a wide variety of tumors. Recently, two genes, p16INK4A and p15INK4B (also called MTS1 and MTS2), have been localized in close proximity at the 9p21 locus, encoding cyclin-dependent kinases 4/6 inhibitors of relative molecular mass 16 kD and 15 kD, respectively and also found to be deleted at a high frequency in tumor cell lines. We analyzed p16INK4A and p15INK4B genes in 178 cases of primary leukemias including 81 cases of chronic lymphocytic leukemia (CLL), seven of hairy cell leukemia (HCL), seven of chronic myelogenous leukemia (CML), 43 of acute myelogenous leukemia (AML), 27 of acute lymphoblastic leukemia (ALL), and 13 of myelodysplastic syndrome (MDS) by Southern blot analyses. The ALL cases showed a relatively high frequency of homozygous deletions (22%, 6 of 27) at the p16INK4A gene locus. Interestingly, of the six cases with p16INK4A homozygous deletions, only three showed homozygous deletions at the p15INK4B gene. In 81 CLL patients, we detected one homozygous and five heterozygous deletions at both the p16INK4A and p15INK4B genes and two heterozygous deletions at the p16INK4A gene alone. Deletion of these two genes in AML cases is relatively low (9%). We did not detect deletions in any of the MDS, HCL, and CML cases examined. Sequence analyses of p16INK4A gene of six CLL cases with heterozygous deletion at this locus showed a 27-bp deletion at the splice acceptor site of intron 1 in one case and changes in the coding sequence in three other cases. The data presented in this report showed that (1) p16INK4A and p15INK4B genes are preferentially deleted homozygously in ALL and heterozygously in CLL cases with frequent mutation in the second allele, and (2) p16INK4A gene appears to be more frequently deleted than p15INK4B gene.  相似文献   
28.
The action of inosine (2.5, 5, or 10 mg.kg-1.min-1 iv) was investigated in open chest rats (n = 46) and guinea pigs (n = 16). Left ventricular and aortic pressures, dP/dtmax, and stroke volume were measured. Additionally, isovolumic peak pressure and peak dP/dtmax were measured during short occlusions of the aorta for assessing myocardial performance independent of circulatory changes. In rats inosine caused a dose dependent decrease in dP/dtmax (-5%, -21%, -40% of preinfusion values), heart rate (-7%, -23%, -55%), and mean aortic pressure. Additionally, a subgroup of seven rats was paced at their initial preinfusion heart rate, but independently from the heart rate there was a reduction in dP/dtmax (-15%). The isovolumic measurements confirmed the negative inotropic effect of inosine in rats. Peak dP/dtmax was reduced to 85% of preinfusion values with a dose of 2.5 mg.kg-1 min-1 (to 70% of preinfusion values with 10 mg.kg-1.min-1). Similarly, the maximum isovolumic pressure for a defined filling volume was decreased by 30 mmHg (at 350 microliter; 5 mg.kg-1.min-1; p less than 0.05). The mean aortic pressure decreased with 2.5 mg.kg-1.min-1 inosine indicating vasodilative properties. In contrast to the significant effects in rats even 10 mg.kg-1.min-1 inosine did not have an effect on heart rate, mean aortic pressure, or dP/dtmax in guinea pigs. The isovolumic peak left ventricular pressure in guinea pigs was also unchanged after inosine infusion. Thus the haemodynamic effects of inosine were species dependent.  相似文献   
29.

Background

Primary care is increasingly interested in the identification of frailty, as it selects the target population for integrated care. However, instruments for the identification of frailty specifically validated for use in primary care are scarce. This study developed the Easycare Two-step Older persons Screening (Easycare-TOS), which provides a valid, efficient, and pragmatic screening procedure to identify frail older people.

Aim

This paper aims to describe the development of the Easycare-TOS and the data from the pilot studies.

Design and setting

Observational pilot study in seven academic GP practices in and around Nijmegen, The Netherlands.

Method

The Easycare-TOS was developed in a cyclic process with the input of stakeholders. In every cycle, the requirements were first defined, then translated into a prototype that was tested in a pilot study. The Easycare-TOS makes optimal use of prior knowledge of the GP, and the professionals’ appraisal is decisive in the frailty decision, instead of a cut-off score. Further, it considers aspects of frailty, as well as aspects of the care context of the patient.

Results

The pilot data have shown that after step 1, two-thirds of the patients do not need further assessment, because they are judged as not frail, based on prior knowledge of the GP. The overall prevalence of frailty in this pilot study is 24%. Most professionals who participated in the pilot studies considered the time investment acceptable and the method to be of added value.

Conclusion

The Easycare-TOS instrument meets the predefined efficiency, flexibility, and acceptability requirements for use as an identification instrument for frailty in primary care.  相似文献   
30.
The endovenous revolution has accelerated the development of new techniques and devices for the treatment of varicose veins. The ClariVein® mechanochemical ablation device offers tumescentless treatment with a rotating ablation tip that can theoretically become stuck in tissue. We present the first report of retrograde stripping of the small saphenous vein without anaesthesia following attempted use of the ClariVein® device, without adverse sequelae.  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