全文获取类型
收费全文 | 19691篇 |
免费 | 1734篇 |
国内免费 | 443篇 |
专业分类
耳鼻咽喉 | 5篇 |
儿科学 | 360篇 |
妇产科学 | 38篇 |
基础医学 | 495篇 |
口腔科学 | 10篇 |
临床医学 | 4797篇 |
内科学 | 11406篇 |
皮肤病学 | 10篇 |
神经病学 | 329篇 |
特种医学 | 260篇 |
外科学 | 743篇 |
综合类 | 1954篇 |
预防医学 | 172篇 |
眼科学 | 11篇 |
药学 | 1058篇 |
7篇 | |
中国医学 | 184篇 |
肿瘤学 | 29篇 |
出版年
2024年 | 7篇 |
2023年 | 475篇 |
2022年 | 381篇 |
2021年 | 937篇 |
2020年 | 943篇 |
2019年 | 981篇 |
2018年 | 841篇 |
2017年 | 598篇 |
2016年 | 604篇 |
2015年 | 610篇 |
2014年 | 1212篇 |
2013年 | 1185篇 |
2012年 | 832篇 |
2011年 | 871篇 |
2010年 | 755篇 |
2009年 | 757篇 |
2008年 | 777篇 |
2007年 | 809篇 |
2006年 | 735篇 |
2005年 | 757篇 |
2004年 | 666篇 |
2003年 | 664篇 |
2002年 | 539篇 |
2001年 | 541篇 |
2000年 | 459篇 |
1999年 | 411篇 |
1998年 | 414篇 |
1997年 | 361篇 |
1996年 | 286篇 |
1995年 | 271篇 |
1994年 | 246篇 |
1993年 | 240篇 |
1992年 | 248篇 |
1991年 | 216篇 |
1990年 | 206篇 |
1989年 | 150篇 |
1988年 | 153篇 |
1987年 | 105篇 |
1986年 | 119篇 |
1985年 | 99篇 |
1984年 | 104篇 |
1983年 | 70篇 |
1982年 | 57篇 |
1981年 | 35篇 |
1980年 | 37篇 |
1979年 | 32篇 |
1978年 | 24篇 |
1977年 | 15篇 |
1976年 | 16篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 781 毫秒
71.
K. DAHLBORN J. HOSSAINI-HILALI S. BENLAMLIH B. E. KARLBERG 《Acta physiologica (Oxford, England)》1992,144(4):485-486
Human muscle samples were obtained with the percutaneous biopsy technique. The samples were membrane-hyperpermeabilized (skinned) using a chemical or freeze-drying technique. Short single fibre segments were dissected from the sample, transferred to an experimental chamber, connected to a force transducer and manipulator, and exposed to temperature-controlled solutions. The force generating-capacity, the sensitivity of the contractile apparatus to calcium and the caffeine threshold for calcium release from the sarcoplasmic reticulum could be studied in the short muscle fibre segments obtained from man with the percutaneous muscle biopsy technique. The average length of the fibre segments between the connectors was 0.44±0.21 mm. Thus, detailed studies of the contractile machinery can be made on human skinned muscle fibres with only minimal discomfort to the patient or subject during biopsy, which should be useful in studies of neuromuscular disease, muscle plasticity or in applied physiology. 相似文献
72.
BIRGITTA HOULTZ BÖRJE DARPÖ NILS EDVARDSSON† PER BLOMSTRÖM‡ JOHANNES BRACHMANN§ HARRY J.G.M. CRIJNS STEEN M. JENSEN¶ ELISABETH SVERNHAGE HANS VALLIN†† KARL SWEDBERG 《Pacing and clinical electrophysiology : PACE》1998,21(5):1044-1057
The aim of this study was to identify predictors of torsades de pointes (TdP) in patients with atrial fibrillation (AF) or flutter exposed to the Class III antiarrhythmic drug almokalant. TdP can be caused by drugs that prolong myocardial repolarization. One hundred patients received almokalant infusion during AF (infusion 1) and 62 of the patients during sinus rhythm (SR) on the following day (infusion 2). Thirty-two patients converted to SR. Six patients developed TdP. During AF, T wave alternans was more common prior to infusion (baseline) in patients developing TdP (50% vs 4%, P < 0.01). After 30 minutes of infusion 1, the TdP patients exhibited a longer QT interval (493 ± 114 vs 443 ± 54 ms [mean ± SD], P < 0.01), a larger precordial QT dispersion (50 ± 74 vs 27 ± 26 ms, P < 0.05), and a lower T wave amplitude (0.12 ± 0.22 vs 0.24 ± 0.16 mV. P < 0.01). After 30 minutes of infusion 2, they exhibited a longer QT interval (672 ± 26 vs 489 ± 74 ms, P < 0.001), a larger QT dispersion in precordial (82 ± 7 vs 54 ± 52 ms, P < 0.01) and extremity leads (163 ± 0 vs 40 ± 34 ms, P < 0.001), and T wave alternans was more common (100% vs 0%, P < 0.001). Risk factors for development of TdP were at baseline: female gender, ventricular extrasystoles, and treatment with diuretics; and, after 30 minutes of infusion: sequential bilateral bundle branch block, ventricular extrasystoles in bigeminy, and a biphasic T wave. Patients developing TdP exhibited early during almokalant infusion a pronounced QT prolongation, increased QT dispersion, and marked morphological T wave changes. 相似文献
73.
目的:探讨和鉴别心电图短P-R间期的产生原因,为临床诊断、治疗提供依据。方法:检测115例受检者的常规导联心电图(RLECG)、头胸导联心电图(HCECG)、食管导联心电图(ELECG),对其中55例临床可疑心律失常和RLECG示短P-R间期者行食管心房调搏电生理检查。结果:①P波出现率和振幅均值比较ELECG>HCECG>RLECG(P<0.01),出现率分别为100%、95%、91%。②HCECGP-R段均值(P<0.01)及变异系数<RLECG。③RLECG波幅低、图形多变是产生心电图短P-R间期的主要原因。结论:作为无创伤性检查方法,HCECG和ELECG可以对短P-R间期者进行初步筛选,而经食管心房调搏能检测ECG短P-R间期的电生理特性,对鉴别诊断有肯定价值。 相似文献
74.
PIERRE VULLIEMIN ALESSANDRO DEL BUFALO JURG SCHLAEPFER MARTIN FROMER LUKAS KAPPENBERGER 《Pacing and clinical electrophysiology : PACE》1994,17(8):1391-1398
Assuming that type I atrial flutter is a macroreentrant circuit, its cycle length should vary with the atrial dimensions. In order to test this hypothesis, flutter cycle length was measured while inducing atrial volume and pressure changes by postural and pharmacological means in seven patients undergoing a therapeutic programmed stimulation for type 1 atrial flutter conversion. Right atrial volume was estimated from B-mode echocardiography data. Basal values were compared with those obtained during inspiration, expiration, Valsalva maneuver, negative tilt (head down), and positive tilt (head up) with 0.8–1.6 mg p.o. nitroglycerin. The right atrial size increased slightly from 17.8 to 18.3 cm2 (P = 0.04) during the pressure load induced by negative tilt (+ 3 mmHg), with a corresponding lengthening of the flutter cycle length from 228 to 233 msec (P = 0.02). Similarly, pressure unloading of -2 mmHg by positive tilting and nitrates was accompanied by a decrease in right atrial size to 16.6 cm2 (P = 0.04), with a corresponding decrease in cycle length from 228 to 219 msec (P = 0.03). Respiratory maneuver yielded similar results with an inspiratory cycle lengthening, expiratory shortening, and further shortening during Valsalva maneuver. These experiments demonstrate a direct relation between cycle length and atrial volume in human type I atrial flutter. They underline the importance of the right heart preload and atrial size for the electrophysiological characteristics of type I atrial flutter. Beside its fundamental interest, this finding is important for the understanding of the mechanism of maintenance and therapeutic responses of this common arrhythmia. 相似文献
75.
Masayuki Mano Akira Sugawara Yasuo Nara Kazuwa Nakao Ryoichi Horie Jiro Endo Hiroo Imura Yukio Yamori 《Clinical and experimental pharmacology & physiology》1992,19(12):795-801
1. Effects of potassium (K) supplementation (100 mEq/day) on urinary sodium (Na) excretion and on the secretion of atrial natriuretic polypeptide (ANP) during salt loading (350 mEq/day) were studied in 12 healthy salt-resistant normotensives under strictly controlled metabolic ward conditions. 2. Urinary volume and Na excretion on the first day of the high salt period (HSP) were significantly greater in the K-supplemented group (KG) than in the control group (CG). 3. There was a significant gain in bodyweight after salt loading in both groups, with a significantly greater gain in CG on the second day of HSP. Haematocrit decreased significantly during salt loading in both groups, the degree of which was significantly greater in CG. 4. Plasma norepinephrine decreased significantly during salt loading in both groups, the degree of which was significantly less in KG than in CG. A significant increase in plasma ANP was observed in CG on and after the second day of HSP, while a significant increase in plasma ANP was observed on the fifth day of HSP in KG. 5. These findings indicate that K supplementation accelerates diuresis and natriuresis, resulting in moderate suppression of volume expansion induced by salt loading and that this accelerated diuresis and natriuresis is not a result of the action of ANP. 相似文献
76.
Invasive cardiac pacing has proved useful in the induction and termination of reentrant sustained tachycardias. In one of our two cases, programmed ventricular extra-stimulation was used to induce sustained ventricular tachycardia from the endocardial surface of the right ventricle. Induced ventricular tachycardia was terminated by burst ventricular pacing with an external cardiac pacemaker. In our second patient, external pacing was effective at inducing and terminating sustained supraventricular tachycardia. These patients illustrate that the principles of terminating sustained reentrant tachycardia with invasive pacing may also apply to noninvasive external pacing. The usefulness of this approach in treating reentrant tachycardias needs further evaluation. 相似文献
77.
78.
Ostial PV Isolation: 总被引:2,自引:0,他引:2
SABINE ERNST MATTHIAS ANTZ FEIFAN OUYANG THOMAS VOGTMANN MASAHIKO GOYA DIETMAR BÄNSCH ANSELM SCHAUMANN KARL-HEINZ KUCK 《Pacing and clinical electrophysiology : PACE》2003,26(7P2):1624-1630
Pulmonary vein (PV) isolation by elimination of spike potentials has been reported to cure drug refractory atrial fibrillation. Because of the heterogenous morphology of the PVs, sequential electroanatomic reconstruction of the PVs was performed in 39 patients (group A), who underwent subsequent PV isolation by interruption of all conductive myocardial fibers by distinct RF current applications using a "lasso" approach. In group B (157 patients), only biplane two-dimensional fluoroscopy was performed to guide the diagnostic and the ablation catheters. After reprocedures (in 7% of patients in group A and 22% of group B), which depicted a recurrence of a spike potential inside or at the ostium of >1 previously isolated PV in all restudied patients, stable sinus rhythm was documented in 69% of patients in group A and 60% of patients in group B. Reasons for the relapse of the previously eliminated spike potentials include a temporary ablation effect and a too distal interruption of the conducting myocardial fiber. Detailed knowledge of the individual three-dimensional morphology enhanced the clinical success rate of PV isolation but is time-consuming using CARTO (8.0 ± 1.7 vs 5.0 ± 1.6, P < 0.001) . Further technical improvement to fuse the individual three-dimensional anatomy and the electrophysiological markers to a composed "electroanatomic" map may overcome this limitation in the future. (PACE 2003; 26[Pt. II]:1624–1630) 相似文献
79.
80.
TODD J. COHEN M.D. ENRICO P. VELTRI M.D. MORTON M. MOWER M.D. 《Journal of cardiovascular electrophysiology》1988,2(4):352-358
Current antitachycardia systems such as the automatic implantable cardioverter/defibrillator (AICD), detect tachyarrhythmias primarily by sensing rate and thereby perform inadequately in differentiating hemodynamically stable from unstable arrhythmias. As a result, these devices may discharge during stable tachycardias (such as sinus tachycardia), causing discomfort to the patient and depleting the device's limited energy supply. If a parameter which could reflect the particular hemodynamic state of a tachycardia were incorporated into the sensing algorithm of these systems, function may be more hemodynamically precise and discharge specificity may be improved. 相似文献