全文获取类型
收费全文 | 20742篇 |
免费 | 1144篇 |
国内免费 | 539篇 |
学科分类
医药卫生 | 22425篇 |
出版年
2024年 | 30篇 |
2023年 | 228篇 |
2022年 | 495篇 |
2021年 | 608篇 |
2020年 | 576篇 |
2019年 | 470篇 |
2018年 | 480篇 |
2017年 | 469篇 |
2016年 | 497篇 |
2015年 | 679篇 |
2014年 | 1328篇 |
2013年 | 1233篇 |
2012年 | 1129篇 |
2011年 | 1289篇 |
2010年 | 1169篇 |
2009年 | 1216篇 |
2008年 | 1214篇 |
2007年 | 1222篇 |
2006年 | 1213篇 |
2005年 | 998篇 |
2004年 | 776篇 |
2003年 | 716篇 |
2002年 | 587篇 |
2001年 | 510篇 |
2000年 | 469篇 |
1999年 | 396篇 |
1998年 | 322篇 |
1997年 | 264篇 |
1996年 | 206篇 |
1995年 | 218篇 |
1994年 | 183篇 |
1993年 | 122篇 |
1992年 | 126篇 |
1991年 | 119篇 |
1990年 | 99篇 |
1989年 | 93篇 |
1988年 | 79篇 |
1987年 | 77篇 |
1986年 | 52篇 |
1985年 | 71篇 |
1984年 | 48篇 |
1983年 | 33篇 |
1982年 | 48篇 |
1981年 | 27篇 |
1980年 | 33篇 |
1979年 | 34篇 |
1978年 | 44篇 |
1977年 | 23篇 |
1976年 | 30篇 |
1973年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
R. -M. Jolidon MD H. Knecht L. Humair A. de Torrente 《Journal of molecular medicine (Berlin, Germany)》1991,69(8):340-344
Summary A young man who had suffered several episodes of deep-vein thrombosis of the legs since the age of 20 had a myocardial infarction at the age of 33, at which time both a prolonged partial thromboplastin time (PTT), compatible with a lupus anticoagulant (LA), and decreased fibrinolytic capacity (FC) were found.His sister presented with deep-vein thrombosis of a leg and subsequent pulmonary embolism when she was 18 years old. She had a miscarriage three years later and developed a hemolytic-uremic syndrome at the age of 35. The PT and FC were normal. Laboratory investigations of the parents revealed positive antinuclear antibodies in the mother's serum but no anomaly in the father.This study suggests a familial tendency to develop autoimmune disorders associated with LA and thromboembolic complications related to decreased FC. 相似文献
72.
Summary The aim of the present study was to investigate the chronic effects of a dietetic antihypertensive treatment on blood pressure, ventricular dynamics and geometry of the pressure loaded heart. Spontaneously hypertensive rats (SHR) received a standard diet enriched with 10% mackerel oil, containing 30% polyunsaturated Q-3 fatty acids, over a period of 70 days. As described previously the diet reduced blood pressure permanently by 40-50 mm Hg. Despite this reduction, the degree of left ventricular hypertrophy was only slightly (statistically insignificantly) reduced. This was probably a result of an increase in sympathetic tone as indicated by a raised pulse rate. On the other hand, the treatment prevented the development of eccentric hypertrophy, typical to the SHR, without changing the elastic material properties of the myocardium. Since the age-matched controls did not show significant degenerative alterations, protective effects at the level of myocardial tissue could not be demonstrated. Furthermore, future investigations need to investigate why myocardial contractility of the treated animals diminishes as observed in this study. 相似文献
73.
H. W. Bonner C. K. Buffington J. J. Newman R. P. Farrar D. Acosta 《European journal of applied physiology》1978,39(1):1-6
Summary 5-day-old neonatal offspring of exercised or non-exercised pregnant Sprague Dawley rats were used to prepare primary cultures
of beating myocardial cells. The cells from the exercise group exhibited a slower beating rate for both single and aggregate
cells; a larger cell size; an increased percentage of contracting cells; a greater capacity to form confluent monolayers,
and a greater viability. It was concluded that exercise during the period of pregnancy produced morphological alterations
in the myocardium of the progeny. 相似文献
74.
Ken Dewitte Marc Claeys Emeline Van Craenenbroeck Koen Monsieurs Hein Heidbuchel Vicky Hoymans Tibor Stoop 《Pathophysiology》2019,26(1):53-59
Aims
We explored the effect of remote ischaemic conditioning (RIC) on endothelial function and on circulating mediators.Methods and results
In 20 healthy male volunteers (mean age 31?±?10 years), flow-mediated dilation (FMD) was measured before and after 20?min of arm ischaemia, followed by reperfusion. Remote ischaemic conditioning (RIC) was performed by applying 3 cycles of 5?min of ischaemia of the leg at the onset of index arm ischaemia. Each volunteer underwent the IR-induced vascular injury protocol with and without RIC in a crossover study design.In the control group, IR significantly reduced FMD (5.9?±?2.9% before IR vs. 2.2?±?3.7% after IR; p?<?0.001). This effect was significantly attenuated by performing RIC (FMD of 5.5?±?3.1% before IR vs. 4.0?±?3.4% % after IR; p for interaction?=?0.01). Serum levels of SOD and ADMA increased significantly whereas MCP-1 and VEGF levels decreased significantly.Only changes in SOD levels were significantly related to the degree of RIC induced protection (r²?=?0.34; p?=?0.018).Conclusion
RIC has protective effects against endothelial IR injury. Our biomarker study suggests that anti-oxidative stress mediators, such as SOD, seem to be more involved in the pathogenesis of RIC-induced protection in humans than angiogenesis factors or chemo-attractant cytokines. 相似文献75.
保留瓣下结构的几种机械瓣下游血流动力学多普勒超声研究 总被引:2,自引:0,他引:2
了解二尖瓣置换术mitralvalvereplacement,MVR保留瓣下结构对不同类型机械瓣下游血流动力学的影响,为合理选择术式以最大限度减少手术并发症提供科学依据。方法采用彩色多普勒超声结合计算机图像分析技术,对保留瓣下结构的不同类型机械瓣置换术后患者机械瓣下游湍流剪应力turbulentshearstress,TSS等指标进行体内定量研究。结果无论保留全瓣或后瓣,跨瓣血流边界位点TSS在两种不同构型机械瓣组间均存在显著性差异(P<0.05),单叶机械瓣(单叶瓣)TSS较双叶机械瓣(双叶瓣)高。对于单叶瓣,TSS在保留全瓣瓣下结构组(保留全瓣组)、保留后瓣瓣下结构组(保留后瓣组)与未保留瓣下结构组(未保留组)间均存在显著差异(P<0.05)。而对于双叶瓣,保留全瓣组TSS均高于其它2组(P<0.05)。结论保留瓣下结构可改善术后患者心功能,但却在一定程度上增加跨瓣血流扰动性,使下游TSS增大。这种影响以全瓣保留者为著,单叶瓣甚于双叶瓣。对于心功能较差,有必要保留全瓣瓣下结构者,可尽量使用双叶瓣,以减轻对人工心瓣下游血流动力学可能产生的不良影响。 相似文献
76.
H. M. Piper 《Journal of molecular medicine (Berlin, Germany)》1989,67(9):465-476
Summary After prolonged ischemia or hypoxia myocardial injury is not reversed but exacerbated by a resupply of the tissue with oxygen and substrates. The mechanism by which reversible ischemic or hypoxic myocardial injury becomes irreversible is not yet understood. It has been debated whether reperfusion injury merely uncovers pre-existing irreversible injury, or is indeed caused by the reperfusion/reoxygenation process. In recent years, three theories have been discussed that relate the onset of irreversibility either to: a critical energy loss; a critical accumulation of cellular calcium; or to the deleterious effects of free radical formation. In certain experimental models for each of these theories favourable results have been obtained. Current research suggests that absolute reversibility thresholds in energy depletion or calcium accumulation in the ischemic or hypoxic cell do not exist. A key role of free radical injury for reperfusion injury must also be questioned. There is, however, evidence that in tissue reversibility of ischemic cardiomyocyte injury is limited by conditions that make calcium-induced hypercontracture upon reoxygenation unavoidable. This occurs when, by hypercontracture, mutual mechanical disruption of the cells destroys the tissue. From isolated cardiomyocytes that are able to metabolically survive hypercontracture it has been observed that these metabolic conditions do not represent the last biological possibility to reverse injury. 相似文献
77.
Semenov SY Svenson RH Bulyshev AE Souvorov AE Nazarov AG Sizov YE Posukh VG Pavlovsky A Tatsis GP 《Annals of biomedical engineering》2000,28(1):55-60
The proposed dielectrical relaxation model of the myocardium in the microwave spectrum has been verified both on test solutions and on normal canine myocardium. Furthermore, the model was utilized to reconstruct the changes in tissue properties (including myocardial bulk resistance and water content) following myocardial acute ischemia and chronic infarction. It was shown that the reconstructed myocardial resistance and water content correlate dynamically with the process of the development of acute myocardial ischemic injury. In chronic cases the reconstructed resistance and water content of infarcted myocardium are significantly different from that of normal myocardium: the resistance is lower and water content is higher than in normal myocardium. © 2000 Biomedical Engineering Society.
PAC00: 8764-t, 8719Xx 相似文献
78.
The infrapyloric artery and cephalic pancreatoduodenectomy with pylorus preservation: preliminary study 总被引:1,自引:0,他引:1
Ph Wind JM Chevallier JJ Sarcy V Delmas PH Cugnenc 《Surgical and radiologic anatomy : SRA》1994,16(2):165-172
Summary Cephalic pancreatoduodenectomy (CPD) with pylorus preservation has been suggested to improve the functional and nutritional result of surgery. At operation, the first two centimeters of the duodenum are preserved, the vascular arch of the lesser gastric curvature is saved and the right gastroepiploic artery is resected at its origin. The aim of this study on 15 fresh cadavers was to determine the origin of the vascularization of the remaining duodenum and also the possibilities of preserving an optimal vascularization after CPD and pylorus preservation. All of the arteries supplying the remaining duodenum and arising either from the right gastric artery or the right gastroepiploic artery were identified. The distances between the origin of the infrapyloric artery and the termination of the gastroduodenal artery on the cranial and ventral pancreaticoduodenal artery and the left gastroepiploic artery were measured. At CPD with pylorus preservation, the study demonstrated that: 1) the cranial side of the remaining duodenum remains vascularized in 80% of the cases by one or two supraduodenal branches coming from the right gastric artery; 2) ligation of the right gastroepiploic artery eliminates all vascular supply to the caudal side of the remaining duodenum in almost half of the cases; 3) in these cases, the dissection of the bifurcation of the gastroduodenal artery and the vascular section beyond the origin of the infrapyloric artery allowed a direct vascular supply to the remaining duodenum to be preserved.This work was presented at the French Section of the European Association of Clinical Anatomy meeting, Bobigny, France, 1992 相似文献
79.
Jager F Taddei A Moody GB Emdin M Antolic G Dorn R Smrdel A Marchesi C Mark RG 《Medical & biological engineering & computing》2003,41(2):172-182
The long-term ST database is the result of a multinational research effort. The goal was to develop a challenging and realistic
research resource for development and evaluation of automated systems to detect transient ST segment changes in electrocardiograms
and for supporting basic research into the mechanisms and dynamics of transient myocardial ischaemia. Twenty-four hour ambulatory
ECG records were selected from routine clinical practice settings in the USA and Europe, between 1994 and 2000, on the basic
of occurrence of ischaemic and non-ischaemic ST segment changes. Human expert annotators used newly developed annotation protocols
and a specially developed interactive graphic editor tool (Semia) that supported paperless editing of annotations and facilitated international co-operation via the Internet. The database
contains 86 two- and three-channel 24h annotated ambulatory records from 80 patients and is stored on DVD-ROMs. The database
annotation files contain ST segment annotations of transient ischaemic (1155) and heart-rate related ST episodes and annotations
of non-ischaemic ST segment events related to postural changes and conduction abnormalities. The database is intended to complement
the European Society of Cardiology ST-T database and the MIT-BIH and AHA arrhythmia databases. It provides a comprehensive
representation of ‘real-world’ data, with numerous examples of transient ischaemic and non-ischaemic ST segment changes, arrhythmias,
conduction abnormalities, axis shifts, noise and artifacts. 相似文献
80.
Myocardial function is impaired by ischaemia, and it remains depressed during reperfusion following short periods of ischaemia (stunned myocardium). We tested whether ischaemic and reperfusion dysfunction, in particular the time course of its recovery, can be distinguished by postextrasystolic potentiation (PESP). In eight open-chest dogs, posterior systolic wall thickening (sonomicrometry) was reduced by graded occlusion of the left circumflex coronary artery (LCX) from 17.4±6.8% (SD) during control conditions to 10.7±1.3% (mild ischaemic dysfunction), 7.2±2.3% (moderate ischaemic dysfunction), 3.6±1.4% (severe ischaemic dysfunction), and -4.4±3.6% (complete coronary occlusion). Extrasystoles with constant prematurity and a fully compensated postextrasystolic interval were induced after at least 4 min steady-state ischaemia. After each ischaemic period full recovery of posterior systolic wall thickening was assured. During 8 h of reperfusion following a 15-min LCX occlusion, extrasystoles were induced when posterior systolic wall thickening was comparable to one degree of the preceding ischaemic dysfunction. The increases in posterior systolic wall thickening induced by PESP were 10.5±5.8% during control conditions, during ischaemia they were 11.5±3.5% (mild dysfunction), 12.3±4.6% (moderate dysfunction), 12.6±4.1% (severe dysfunction) and 10.4±4.4% (complete coronary occlusion), and during reperfusion they were 12.8±8.2% (severe dysfunction), 13.0±9.7% (moderate dysfunction) and 10.7±2.2% (mild dysfunction). These increments in systolic wall thickening as well as those in ejection thickening were not significantly different. PESP can thus not distinguish between ischaemic and reperfusion dysfunction nor between different degrees of myocardial dysfunction.This study was supported by the Deutsche Forschungsge-meinschaft (He 1320/3-2). cand. med. S. Schäfer was involved in some of these experiments and presented part of the data at the 56th Annual Meeting of the Deutsche Gesellschaft für Herz- und Kreislaufforschung in Mannheim (Z Kardiol 79 [Suppl 1]: 24,1990). Part of the data were also presented at the 11th Congress of the European Society of Cardiology in Nice (Eur Heart J 10 [Suppl]: 242, 1989) and at the 73rd Annual Meeting of the Federation of American Societies for Experimental Biology in New Orleans (FASEB J 3: A841, 1989) 相似文献