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   5760篇
  免费   311篇
  国内免费   32篇
耳鼻咽喉   55篇
儿科学   129篇
妇产科学   58篇
基础医学   876篇
口腔科学   156篇
临床医学   549篇
内科学   1258篇
皮肤病学   163篇
神经病学   548篇
特种医学   254篇
外科学   867篇
综合类   22篇
一般理论   2篇
预防医学   354篇
眼科学   57篇
药学   412篇
中国医学   3篇
肿瘤学   340篇
  2022年   47篇
  2021年   101篇
  2020年   77篇
  2019年   101篇
  2018年   149篇
  2017年   113篇
  2016年   146篇
  2015年   123篇
  2014年   175篇
  2013年   248篇
  2012年   334篇
  2011年   361篇
  2010年   238篇
  2009年   218篇
  2008年   343篇
  2007年   344篇
  2006年   306篇
  2005年   299篇
  2004年   272篇
  2003年   266篇
  2002年   239篇
  2001年   78篇
  2000年   82篇
  1999年   75篇
  1998年   57篇
  1997年   51篇
  1996年   35篇
  1995年   27篇
  1994年   37篇
  1992年   39篇
  1991年   48篇
  1990年   45篇
  1989年   54篇
  1988年   40篇
  1987年   39篇
  1986年   39篇
  1985年   42篇
  1984年   45篇
  1983年   34篇
  1982年   29篇
  1981年   24篇
  1980年   27篇
  1979年   34篇
  1978年   45篇
  1977年   36篇
  1976年   25篇
  1975年   30篇
  1974年   27篇
  1972年   31篇
  1971年   29篇
排序方式: 共有6103条查询结果,搜索用时 15 毫秒
991.

Abstract

Background

The EuroCMR registry sought to evaluate indications, image quality, safety and impact on patient management of clinical routine CMR in a multi-national European setting. Furthermore, interim analysis of the specific protocols should underscore the prognostic potential of CMR.

Methods

Multi-center registry with consecutive enrolment of patients in 57 centers in 15 countries. More than 27000 consecutive patients were enrolled.

Results

The most important indications were risk stratification in suspected CAD/Ischemia (34.2%), workup of myocarditis/cardiomyopathies (32.2%), as well as assessment of viability (14.6%). Image quality was diagnostic in more than 98% of cases. Severe complications occurred in 0.026%, always associated with stress testing. No patient died during or due to CMR. In 61.8% CMR findings impacted on patient management. Importantly, in nearly 8.7% the final diagnosis based on CMR was different to the diagnosis before CMR, leading to a complete change in management. Interim analysis of suspected CAD and risk stratification in HCM specific protocols revealed a low rate of adverse events for suspected CAD patients with normal stress CMR (1.0% per year), and for HCM patients without LGE (2.7% per year).

Conclusion

The most important indications in Europe are risk stratification in suspected CAD/Ischemia, work-up of myocarditis and cardiomyopathies, as well as assessment of viability. CMR imaging is a safe procedure, has diagnostic image quality in more than 98% of cases, and its results have strong impact on patient management. Interim analyses of the specific protocols underscore the prognostic value of clinical routine CMR in CAD and HCM.

Condensed abstract

The EuroCMR registry sought to evaluate indications, image quality, safety and impact on patient management of clinical routine CMR in a multi-national European setting in a large number of cases (n > 27000). Based on our data CMR is frequently performed in European daily clinical routine. The most important indications in Europe are risk stratification in suspected CAD/Ischemia, work-up of myocarditis and cardiomyopathies, as well as assessment of viability. CMR imaging is a safe procedure, has diagnostic image quality in more than 98% of cases, and its results have strong impact on patient management. Interim analyses of the specific protocols underscore the prognostic value of clinical routine CMR in CAD and HCM.  相似文献   
992.
We investigated whether human umbilical cord blood mononuclear cells (HUCBC), which contain hematopoietic and mesenchymal progenitor cells, can limit myocardial cytokine expression and inflammatory cell infiltration in acute myocardial infarction. We permanently ligated the left coronary artery of rats and injected into the myocardium either Isolyte or 4 x 10(6) HUCBC in Isolyte and measured myocardial cytokines with antibody arrays at 2, 6, 12, 24, and 72 hours after infarction. We then measured with flow cytometry myocardial macrophages, neutrophils and lymphocytes at 12, 24, and 72 hours after infarctions in rats treated with either intramyocardial Isolyte or 4 x 10(6) HUCBC. In the Isolyte-treated hearts, between 2 and 12 hours after myocardial infarction, tumor necrosis factor-alpha increased from 6.7 +/- 0.9% to 52.3 +/- 4.7%, monocyte chemoattract protein increased from 9.5 +/- 1.2% to 39.8 +/- 2.1%, fractalkine increased from 11 +/- 1.5% to 28.1 +/- 1.3%, ciliary neurotrophic factor increased from 12.1 +/- 0.02% to 25.9 +/- 1.1%, macrophage inflammatory protein increased from 10.3 +/- 1.5% to 23.9.0 +/- 1.4%, interferon-gamma increased from 8.7 +/- 0.4% to 26.0 +/- 1.6%, interleukin-1beta increased from 6.1 +/- 0.04% to 19.0 +/- 1.2%, and IL-4 increased from 5.9 +/- 0.03% to 15 +/- 1.5% (all p < 0.001 compared with controls). The concentrations of fractalkine remained significantly increased at 72 hours after acute infarction. In contrast, the myocardial concentrations of these cytokines did not significantly change in HUCBC treated hearts at 2, 6, 12, 24, or 72 hours after infarction. The percentage of neutrophils increased from 0.04 +/- 0.2%/50,000 heart cells in the controls to 5.3 +/- 1.2%/50,000 heart cells 12 hours after infarction in Isolyte-treated hearts but averaged only 1.3 +/- 0.7%/50,000 heart cells in HUCBC treated hearts (p < 0.02). Thereafter, the percentages of neutrophils rapidly decreased at 24 and at 72 hours after infarction and averaged 0.6 +/- 0.2%/50,000 heart cells at 72 hours after infarction in Isolyte-treated hearts in contrast to 0.2 +/- 0.1%/50,000 cells in HUCBC hearts (p < 0.05). Moreover, the percentages of neutrophils at 24 and 72 hours in HUCBC hearts were not significantly different from controls. At 24 hours post infarction, the percentage of CD3 and CD4 lymphocytes were 10.7 +/- 1.4% and 6.3 +/- 1.1%/50,000 cells in Isolyte hearts in comparison with only 4.9 +/- 0.8% and 2.9 +/- 0.5% in HUCBC hearts (p < 0.005 for Isolyte versus HUCBC). The percentage of CD11b macrophages was 2.8 +/- 0.3% in Isolyte hearts and 1.9 +/- 0.2% in HUCBC treated hearts (p < 0.05). At 72 hours after infarction, the percentage of CD3 and CD4 lymphocytes averaged 8.0 +/- 1.1% and 5.1 +/- 0.8%/50,000 heart cells in Isolyte hearts in comparison with only 4.1 +/- 0.5% and 2.3 +/- 0.4%/50,000 heart cells in the HUCBC treated infarctions (p < 0.005). Left ventricular infarct sizes in Isolyte-treated hearts at 72 hours post infarction averaged 15.7 +/- 1.4% of the left ventricular muscle area in contrast to HUCBC treated infarctions that averaged 6.9 +/- 1.4% of the left ventricular muscle area (p < 0.02). Moreover in rats followed for 2 months post infarction, the LV ejection fractions decreased to 65.4 +/- 1.9% and 69.1 +/- 1.9% at 1 and 2 months after infarction in Isolyte-treated hearts and were significantly different from HUCBC treated hearts that averaged 72.1 +/- 1.3% and 75.7 +/- 1.4% (both p < 0.02). The present experiments suggest that an important mechanism whereby HUCBC limit infarct size and improve left ventricular ejection fraction is by significantly limiting inflammatory cytokines and inflammatory cells in infarcted myocardium.  相似文献   
993.
Low HPA-axis activity has been proposed as a risk factor for disruptive behaviors. However longitudinal data on this topic are practically lacking. In the present study we investigated if low HPA-axis activity predicted future disruptive behaviors. We included 1,399 boys and girls from the Dutch general population, initially aged 10-12 years. At the first assessment, basal cortisol levels were assessed. At the first assessment and at follow-up 2 years later disruptive behaviors were assessed with parent and self-report questionnaires. The results suggest that the association between low cortisol levels at 8.00 p.m. and future disruptive behaviors according to the parents was only present for boys. More importantly however, the results suggest that low HPA-axis activity is not a good predictor for disruptive behaviors, but could be valuable to identify those with a poor prognosis, once disruptive behaviors are present in preadolescence.  相似文献   
994.
995.
Adult articular cartilage has a limited capacity for self repair. Reproduction of a native structure and functional integrity in damaged cartilage remains a major problem in orthopaedic surgery. Strategies based on the implantation of genetically modified cells to sites of injury may provide workable options to treat articular cartilage lesions like those resulting from acute trauma or associated with the progression of osteoarthritis. Mesenchymal stem cells have remarkable properties that make them an attractive source of cells to treat cartilage disorders due to their self-renewal capability, stemness maintenance, and chondrogenic differentiation potential. For these reasons, such progenitor cells might be further modified by gene transfer protocols to reinforce their potency and consequently, to enhance the healing processes in damaged tissue following transplantation in sites of cartilage injury. Here, we propose an overview of the current approaches employed for cell- and gene-based treatment of articular cartilage disorders using mesenchymal stem cells.  相似文献   
996.
Adrenal growth and increased adrenal function occur in experimental diabetes. Previously, we have shown that phosphoribosyl pyrophosphate (PRPP) and PRPP synthetase increased rapidly between 3 and 7 days after induction of diabetes with streptozotocin (STZ), with less marked changes in enzymes of the pentose phosphate pathway. The present study examines the earlier phase of 1-3 days following induction of diabetes, seeking to elucidate whether control of PRPP production is a result of diabetic hyperglycaemia, or to a more general re-ordering of hormonal factors. To investigate this question, the role of insulin and two different long-acting somatostatin analogues, Angiopeptin and Sandostatin, were used in a well-established animal model. PRPP was chosen specifically as a target for these studies in view of its central role in nucleotide formation and nicotinamide mononucleotide synthesis via Nampt which is the rate-limiting step in the synthesis of NAD and which has been shown to have multiple roles in cell signalling in addition to its known function in glycolysis and energy production. Treatment with the somatostatin analogues ab initio effectively abolished the adrenal growth, the increase in PRPP formation and the rise of PRPP synthetase activity in the first 7 days of diabetes, without having any significant effect on blood glucose values. This suggests that elevated glucose per se is not responsible for the diabetic adrenal hypertrophy and implies that growth factors/hormones, regulated by somatostatin analogues, play a significant role in adrenal growth processes.  相似文献   
997.
998.
999.
Hibernation is an energy-conserving behavior consisting of periods of inhibited metabolism ('torpor') with lowered body temperature. Torpor bouts are interspersed by arousal periods, in which metabolism increases and body temperature returns to euthermia. In deep torpor, the body temperature typically decreases to 2-10 °C, and major physiological and immunological changes occur. One of these alterations constitutes an almost complete depletion of circulating lymphocytes that is reversed rapidly upon arousal. Here we show that torpor induces the storage of lymphocytes in secondary lymphoid organs in response to a temperature-dependent drop in plasma levels of sphingosine-1-phosphate (S1P). Regulation of lymphocyte numbers was mediated through the type 1 S1P receptor (S1P(1)), because administration of a specific antagonist (W146) during torpor (in a Syrian hamster at ~8 °C) precluded restoration of lymphocyte numbers upon subsequent arousal. Furthermore, S1P release from erythrocytes via ATP-binding cassette (ABC)-transporters was significantly inhibited at low body temperature (4 °C) but was restored upon rewarming. Reversible lymphopenia also was observed during daily torpor (in a Djungarian hamster at ± 25 °C), during forced hypothermia in anesthetized (summer-active) hamsters (at ± 9 °C), and in a nonhibernator (rat at ~19 °C). Our results demonstrate that lymphopenia during hibernation in small mammals is driven by body temperature, via altered plasma S1P levels. S1P is recognized as an important bioactive lipid involved in regulating several other physiological processes as well and may be an important factor regulating additional physiological processes in hibernation as well as in mediating the effects of therapeutic hypothermia in patients.  相似文献   
1000.
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