全文获取类型
收费全文 | 34623篇 |
免费 | 2396篇 |
国内免费 | 1432篇 |
专业分类
耳鼻咽喉 | 197篇 |
儿科学 | 262篇 |
妇产科学 | 54篇 |
基础医学 | 1839篇 |
口腔科学 | 57篇 |
临床医学 | 4738篇 |
内科学 | 13472篇 |
皮肤病学 | 59篇 |
神经病学 | 389篇 |
特种医学 | 1621篇 |
外科学 | 1637篇 |
综合类 | 7575篇 |
现状与发展 | 1篇 |
预防医学 | 925篇 |
眼科学 | 41篇 |
药学 | 3785篇 |
26篇 | |
中国医学 | 1709篇 |
肿瘤学 | 64篇 |
出版年
2024年 | 42篇 |
2023年 | 394篇 |
2022年 | 652篇 |
2021年 | 1224篇 |
2020年 | 1153篇 |
2019年 | 979篇 |
2018年 | 948篇 |
2017年 | 834篇 |
2016年 | 905篇 |
2015年 | 970篇 |
2014年 | 2049篇 |
2013年 | 2250篇 |
2012年 | 1702篇 |
2011年 | 1994篇 |
2010年 | 1689篇 |
2009年 | 1573篇 |
2008年 | 1704篇 |
2007年 | 1827篇 |
2006年 | 1760篇 |
2005年 | 1499篇 |
2004年 | 1307篇 |
2003年 | 1191篇 |
2002年 | 1031篇 |
2001年 | 1104篇 |
2000年 | 911篇 |
1999年 | 829篇 |
1998年 | 736篇 |
1997年 | 687篇 |
1996年 | 552篇 |
1995年 | 490篇 |
1994年 | 469篇 |
1993年 | 371篇 |
1992年 | 311篇 |
1991年 | 301篇 |
1990年 | 249篇 |
1989年 | 202篇 |
1988年 | 205篇 |
1987年 | 191篇 |
1986年 | 157篇 |
1985年 | 200篇 |
1984年 | 173篇 |
1983年 | 104篇 |
1982年 | 116篇 |
1981年 | 93篇 |
1980年 | 71篇 |
1979年 | 60篇 |
1978年 | 50篇 |
1977年 | 43篇 |
1976年 | 35篇 |
1975年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
采用正常搏动RR间期的标准差(SD)及心率变异指数(HRV index)作为指标,分析67例老年男性心肌缺血患者的心率变异,并与正常老年男性组及正常青壮年男性组进行了对比,发现前组的RR间期SD、HRVindex均明显低于后两组,其结果有显著性差异(P均〈0.01)。提示心肌缺血可破坏交感与迷走神经的均衡性,造成心率变异降低。 相似文献
72.
S. Aziz L. A. Soine S. L. Lewis A. P. Kruse W. C. Levy K. M. Wehe D. P. Fishbien M. D. Allen 《Transplant international》1997,10(6):446-450
A review of factors contributing to early mortality after cardiac transplantation revealed that up to 25 % of deaths were
due to primary graft dysfunction unrelated to rejection or infection. In light of this finding, evaluation of a donor heart
with regard to its suitability for transplantation takes on added importance. In an effort to screen the suitability of donor
hearts in the region covered by the Northwest Organ Procurement Agency (USA), all donors are evaluated by two-dimensional
transthoracic echocardiography as part of the initial evaluation. A total of 110 donor echocardiograms were reviewed and an
attempt was made to correlate the 30-day outcome with the parameters measured. An unexpected finding was that the presence
of left ventricular hypertrophy in the donor heart was associated with an increase in the incidence of donor heart dysfunction
compared with donors with normal echocardiographic profiles (33 % vs 3 %, P = 0.007).
Received: 12 February 1996 Received after resision: 27 June 1997 Accepted: 14 July 1997 相似文献
73.
1992~1993年间为180例冠脉病变的病人施行冠脉搭桥术,全部病人均采用核甙抑制剂利多氟嗪预处理和低温(28℃)间断缺血心停搏进行术中心肌保护。平均每例病人作冠状动脉端吻合3~4个,每个吻合口用9分钟,主动脉阻断累加时间约25分钟,体外循环时间90分钟,术后医院死亡率1.6%(3/180),无术后心梗发生。作者认为,冠脉搭桥术的术中心肌保护可采用核甙抑制剂和间断缺血心停搏方法,而不用心肌停搏液。 相似文献
74.
为了探讨常温体外循环下采用缺血预调行心肌保护的研究,通过建立犬的常温体外循环全心缺血预调模型,旨在探讨心内直视手术缺血预调保护心肌的可能性。预调组采用升主动脉阻断5分钟,放开10分钟,反复三次的方式预调心脏;对照纽简单并行循环45分钟,而后两组均接受30分钟缺血和60分钟再灌注。结果显示,预调组室颤发生率低(16.7 VS 83.3%P=0.04),无再灌注心律失常(0 VS66.7%P=0.03),心肌ATP消耗减慢(4.69 1.050 VS 2.35±0.86μmol/g wet wt P<0.01),乳酸积累减少(4.49±0.86 VS 9.80 5.53mg/g wet wtP<0.05),心肌细胞超微结构损伤轻。结论:常温体外循环下应用缺血预调保护犬的心肌是可行而有效的。 相似文献
75.
76.
Insights into the assessment of myocardial perfusion offered by different cardiac imaging modalities
Myocardial perfusion may be very broadly defined as the tightly regulated nutrient delivery to cardiac tissue. The different
components of perfusion are myocardial blood flow, oxygen delivery, myocardial oxygen consumption, and myocardial blood volume.
Historically, focus has been placed mostly on the assessment of blood flow. In many instances, knowledge of flow without information
about these other aspects is inadequate. This review discusses the various cardiac imaging techniques used for the assessment
of myocardial perfusion that represent diverse physiologic measures of “perfusion.” Their strengths and limitations are discussed
as is their relevance to specific clinicopathologic conditions. Significant work still needs to be performed before all the
aspects of myocardial perfusion can be precisely measured in human beings.
Supported in part by a grant (R01-HL48890) from the National Institutes of Health, Bethesda, Md. Dr. Lindner is the recipient
of a Fellowship Training Grant from the Virginia Affiliate of the American Heart Association, Glen Allen, Va. Dr. Kaul is
an Established Investigator of the National Center of the American Heart Association, Dallas, Texas. 相似文献
77.
Summary In this study, the99mTc-MIBI myocardial bullseye display of 31 healthy persons and 34 patients with myocardial ischemia and 17 patients with myocardial
infarction were analyzed quantitatively, and compared with the results of myocardial tomography analysis and qualitative bullseye
analysis. The sensitivities of the three methods were 88.2%, 91.2% and 94.1% respectively (P>0.05), and the specificities were 93.5%, 83, 9% and 83.9% respectively (P<0.05). On the other hand, the quantitative analysis obviously outperformed the other two methods in the detection of ischemic
segments of myocardhum near infarction zone (P<0.01). The quantitative analysis of99mTc-MLBI myocardial bullseye (quantitative bullseye) was an objective, specific and sensitive method for diagnosis of coronary
artery disease. 相似文献
78.
Bronwyn A. Kingwell Lisa Krause Stevo Julius 《Clinical and experimental pharmacology & physiology》1994,21(1):31-39
1. Left ventricular (LV) hypertrophy has been implicated in the reduction of baroreflex sensitivity present in hypertension. The aim of the current study was to investigate the mean arterial pressure-heart rate reflex (MAP-HR) in a model which induced left ventricular hypertrophy but no sustained blood pressure elevation. 2. Five mongrel dogs were exposed to transient blood pressure elevation of between 20 and 30 mmHg, through hindlimb compression using a pneumatic pressure suit, for 7 h per day, 6 days per week for 6 weeks. Resting blood pressure was not altered by the 6 week hindlimb compression intervention. 3. Echocardiographically determined LV mass (mean ± s.e.m.) was 116.0 ± 7.4 g prior to hindlimb compression (baseline) and elevated to 125.4 ± 8.1 g (P= 0.003) after 6 weeks of compression. A reduction in the early (E) to late (A) transmitral diastolic flow ratio (E/A) from 1.80 ± 0.06 at baseline to 1.54 ± 0.09 (P = 0.037) after the 6 week intervention suggested that cardiac compliance was reduced. 4. The maximum gain of the MAP-HR reflex, studied using the ‘steady-state’ drug technique, when blood pressure was normal, showed a trend for reduction from 3.85 ± 0.43 beats/min per mmHg at baseline to 3.10 ± 0.45 beats/min per mmHg (P= 0.067) after 6 weeks of compression. This gain reduction became significant after β-adrenoceptor blockade with propranolol (3.13 ± 0.55 vs 2.32 ± 0.25 beats/min per mmHg; P= 0.039). Covariant analysis showed a significant inverse correlation between LV mass and maximum gain (r= 0.96; P<0.001) during the 6 week compression period. 5. The MAP-HR reflex changes in this model mimic those present in hypertension and implicate cardiac hypertrophy as one possible mediator. 相似文献
79.
K. E. Anderson A. M. Dart E. A. Woodcock 《Clinical and experimental pharmacology & physiology》1994,21(2):141-144
1. Global myocariial ischaemia (MI) for periods greater tan 5 min caused an inhibition of phosphatidylinositol specific phospholipase C (PtdIns-PLC) activity. 2. Two min reperfusion following a 20 min MI period, a time point associated with reperfusion-induced arrhythmias, resulted in an activation of PtdIns-PLC activity, dependent on endogenous noradrenaline and mediated via al-adrenoceptors. 3. This 2 min reperfusion response, in contrast to healthy myocardium, resulted in: (i) enhanced PtdIns-PLC activity; (ii) increased sensitivity to endogenous noradrenaline; (iii) rapid increases in inositol(1,4,5)trisphosphate (Ins(1,4,5)P3); and (iv) PLC hydrolysis primarily of PtdIns(4,5)P2, such that the majority of InsP isomers derive from Ins(1,4,5)P3. 4. Together, these data suggest a functional role for Ins(1,4,5)P3 under postischaemic reperfusion conditions, and provide a possible link between al-adrenoceptor stimulation of the PtdIns turnover pathway and reperfusion injury. 相似文献
80.
本文测定了第1-7天急性心梗塞患者红细胞磷脂主要组分含量。结果表明,急性心肌梗塞患者红细胞膜的神经鞘磷含量较正常人明显增高;磷酯酰胆硷,磷脂酰丝氨酸、磷脂酰乙醇胺含量却较正常人明显降低。这说明急性心肌梗塞患者存在红细胞磷脂代谢紊乱,这时心肌缺血的重可能产生不良影响。 相似文献