全文获取类型
收费全文 | 7221篇 |
免费 | 460篇 |
国内免费 | 34篇 |
专业分类
耳鼻咽喉 | 107篇 |
儿科学 | 116篇 |
妇产科学 | 149篇 |
基础医学 | 1051篇 |
口腔科学 | 66篇 |
临床医学 | 575篇 |
内科学 | 1343篇 |
皮肤病学 | 286篇 |
神经病学 | 632篇 |
特种医学 | 594篇 |
外国民族医学 | 14篇 |
外科学 | 1043篇 |
综合类 | 42篇 |
一般理论 | 1篇 |
预防医学 | 346篇 |
眼科学 | 208篇 |
药学 | 401篇 |
中国医学 | 4篇 |
肿瘤学 | 737篇 |
出版年
2023年 | 39篇 |
2022年 | 45篇 |
2021年 | 127篇 |
2020年 | 107篇 |
2019年 | 149篇 |
2018年 | 160篇 |
2017年 | 160篇 |
2016年 | 153篇 |
2015年 | 185篇 |
2014年 | 209篇 |
2013年 | 317篇 |
2012年 | 475篇 |
2011年 | 491篇 |
2010年 | 283篇 |
2009年 | 283篇 |
2008年 | 471篇 |
2007年 | 451篇 |
2006年 | 435篇 |
2005年 | 435篇 |
2004年 | 432篇 |
2003年 | 418篇 |
2002年 | 315篇 |
2001年 | 101篇 |
2000年 | 80篇 |
1999年 | 101篇 |
1998年 | 89篇 |
1997年 | 80篇 |
1996年 | 60篇 |
1995年 | 55篇 |
1994年 | 53篇 |
1993年 | 32篇 |
1992年 | 61篇 |
1991年 | 44篇 |
1990年 | 46篇 |
1989年 | 42篇 |
1988年 | 44篇 |
1987年 | 36篇 |
1986年 | 51篇 |
1985年 | 38篇 |
1984年 | 32篇 |
1983年 | 36篇 |
1982年 | 31篇 |
1981年 | 22篇 |
1980年 | 21篇 |
1978年 | 30篇 |
1977年 | 26篇 |
1973年 | 25篇 |
1972年 | 20篇 |
1971年 | 27篇 |
1969年 | 21篇 |
排序方式: 共有7715条查询结果,搜索用时 15 毫秒
981.
Ventricular arrhythmias during a pacemaker follow-up have been previously reported, usually in conjunction with temporary asynchronous stimulation of a demand pacemaker through magnet application or by increased myocardial excitability, for example, following a myocardial infarction. The subject of this report, an 82-year-old pacemaker patient, had been VVI-paced without problems for the past 11 years. As an aid in determining the sensing threshold, the pacemaker lower rate was reduced from 70 to 40 beats/min. A ventricular tachycardia of 240 beats/min was induced, most likely following short-long cycles; syncope resulted. To our knowledge, this is the first report of induction of a ventricular tachycardia during pacemaker follow-up solely by reduction of pacing rate and not by asynchronous pacing. This case demonstrates an additional potential risk associated with pacemaker rate manipulation during pacemaker follow-up. 相似文献
982.
983.
984.
985.
The influence of meal composition on plasma serotonin and norepinephrine concentrations. 总被引:1,自引:0,他引:1
I Blum Y Vered E Graff Y Grosskopf R Don A Harsat O Raz 《Metabolism: clinical and experimental》1992,41(2):137-140
Reports concerning changes in plasma neurotransmitter values that result from dietary manipulations have not been published so far. The influence of various meal compositions on platelet-poor plasma (PPP) serotonin (5-HT) and norepinephrine (NE) levels was investigated. Healthy volunteers were subjected to three test meals: a carbohydrate-rich meal (86% carbohydrates), a protein-rich meal (70% protein), and a fat-rich meal (92% fat). After a carbohydrate-rich meal, PPP 5-HT values increased significantly (4.47-fold, P less than .02), whereas a smaller increase (1.66-fold, P = NS) was observed after a fat-rich meal. These effects on PPP 5-HT values could be correlated with insulin plasma levels. A protein-rich meal significantly reduced (P = 0.0011) PPP 5-HT to 28% of initial values, despite an increase in plasma insulin levels. This study has shown that (1) changes in meal compositions influence PPP 5-HT and, to a lesser extent, NE values; (2) the resulting changes in PPP 5-HT levels parallel those reported for brain neurotransmitters; and (3) these results seem to indicate that PPP 5-HT levels may be a model for brain synthesis and release of 5-HT. 相似文献
986.
987.
Claus Weiss Birgit Walter Micha F Dorsch Peter B?rtsch 《Blood coagulation & fibrinolysis》2006,17(7):563-568
The use of oral contraceptives (OC) is associated with an increased risk of thrombosis, suggesting OC exert procoagulant and/or antifibrinolytic effects. Given that physical exercise physiologically leads to an activation of blood coagulation and fibrinolysis, this study tested the hypothesis that OC might compromise the fibrinolytic response to exercise. Fibrinolytic variables were measured in 10 women (24 +/- 2 years) using OC (a formulation containing 30 micro g ethinylestradiol and 150 micro g desogestrel) and in 11 women without OC (mean +/- SD, 27 +/- 3 years) before, during and after a 1-h run on a treadmill at a velocity corresponding to an oxygen demand of 75-80% of maximum (anaerobic threshold). Exercise testing gave rise to considerable increases of tissue-type plasminogen activator antigen by seven-fold to eight-fold in women taking and not taking OC alike. In the presence of unchanged plasma levels of plasminogen activator inhibitor-1, exercise-induced release of tissue-type plasminogen activator led to enhanced plasmin formation with respect to plasmin-antiplasmin complexes, rising by (mean +/- standard error) 701 +/- 77 ng/ml (P < 0.001) in women using OC and by 695 +/- 117 ng/ml (P < 0.001 versus baseline; NS versus OC users) in controls. The fibrinolytic response to intensive physical exercise is preserved in women using OC and is similar to women not using OC. 相似文献
988.
I Grosskopf E Graff G Charach G Binyamin S Spinrad I Blum 《Human & experimental toxicology》1991,10(5):351-355
1. The study objective was to determine the hyperphosphataemic and hypocalcaemic effect of hypertonic phosphate enema. The study was conducted in a department of Internal Medicine at a University Medical Center. 2. Fourteen patients were studied. Patients' mean age (+/- s.d.) was 78.5 +/- 9 years. The creatinine clearance was 48.2 +/- 17.4 ml min-1 (mean +/- s.d.). 3. 500 ml (approx. 7 ml kg-1) of Fleet enema (FE - Na2HPO4.7H2O 224 mmol l-1 and NaH2PO4.H2O 1160 mmol l-1) were administered to each patient. Blood was drawn before FE administration and 1/2, 1, 3, 5, 12 and 24 h thereafter. Serum was analysed for levels of inorganic phosphorus and for calcium. 4. The serum inorganic phosphorus level rose from 1.01 +/- 0.3 mmol l-1 to 1.4 +/- 0.5 mmol l-1 (P = 0.001) 1 h after FE was administered. Serum calcium decreased from 2.32 +/- 0.12 mmol l-1 to 2.12 +/- 0.1 mmol l-1 (P less than 0.001) 12 h after FE was administered. 5. We conclude that FE carries a potential risk for acutely ill elderly patients. To avoid untoward effects due to hyperphosphataemia and hypocalcaemia, the phosphate load must be adjusted to the patient's renal function, i.e. enema volume is to be lowered when phosphate concentration is high, so that if renal function is compromised the amount of phosphate absorbed does not exceed renal excretion capacity. 相似文献
989.
Significant damage of the conduction system during cardioplegic arrest is due to necrosis not apoptosis. 总被引:1,自引:0,他引:1
Friedhelm Sayk Stefan Krüger J F Matthias Bechtel Alfred C Feller Hans H Sievers Claus Bartels 《European journal of cardio-thoracic surgery》2004,25(5):801-806
OBJECTIVES: Ventricular conduction disturbances following cardioplegic arrest remains a serious, yet unsolved problem. In the present study we examined whether myocardial conduction cells (MCC, Purkinje fibers) are more vulnerable to ischemia/reperfusion injury than working myocardial cells and whether the damage is due to necrosis or apoptosis. METHODS: Mini-pigs were subjected to 60 min of crystalloid (St Thomas; n = 15 group I) or blood (Buckberg; n = 6 group II) cardioplegic arrest followed by 3 h of reperfusion. Animals not subjected to either procedures served as controls (n = 5). Ventricular myocardial specimens were investigated by hematoxylin and eosin (HE) and periodic acid Schiff (PAS) staining and immunohistochemical labeling of apoptosis-associated proteins (Bax, Bcl-2, Caspase-3). DNA-breaks were visualized by in situ end labeling (terminal deoxynucleotidyl transferase dUTP-biotin nick-end labeling, TUNEL). Electron microscopy confirmed apoptosis or necrosis. RESULTS: MCC of control hearts intrinsically expressed Bax, Bcl-2, and Caspase-3 without signs of either apoptotic or necrotic damage. Subendocardial Purkinje fibers of groups I and II hearts exhibited focal damage, with reduced labeling of apoptosis-associated proteins, glycogen loss, karyopycnosis and increased eosinophilia (15/21 hearts). The majority of damaged MCC displayed nuclear TUNEL-positivity (2.8+/-2.5% of MCC), whereas the average TUNEL-rate of the adjacent working myocardium was low (<0.1%). Electron microscopy demonstrated ischemic changes in MCC consistent with cellular necrosis. CONCLUSIONS: Ischemia/reperfusion injury due to cardioplegic arrest inflicts significant damage on subendocardial MCC, but not on working myocardium. Ultrastructural and light-microscopic findings are consistent with coagulation necrosis, rather than apoptosis. 相似文献
990.
Klaus P. Aicher Michael Laniado Andreas F. Kopp Eckart Grnewller Stephan H. Duda Claus D. Claussen 《Journal of magnetic resonance imaging : JMRI》1993,3(5):731-737
Twenty patients with malignant liver lesions underwent magnetic resonance (MR) imaging with manganese (II) DPDP [N,N′-dipyridoxylethylenediamine-N,N′-diacetate 5,5′-bis(phosphate)] to evaluate the safety and efficacy of the contrast agent. In two groups of 10 patients each, 5 μmol/kg Mn-DPDP was administered intravenously (3 mL/min) at a concentration of either 50 or 10 μmol/mL. T1- and T2-weighted images were obtained with a 1.5-T imager. Six patients reported a total of eight instances of side effects (flush, feeling of warmth, metallic taste) of which seven occured at the 50 μmol/mL concentration. A significant decrease in alkaline phosphatase levels 2 hours after injection was recorded. On T1-weighted images, the 10 μmol/mL formulation yielded significantly greater increases in contrast-to-noise ratio (79.8%–137.5%) than the 50 μmol/mL formulation (46.2%–86.6%). In a blinded reader study of 10 patients with one to five lesions each, no lesion was missed on Mn-DPDP–enhanced T1-weighted images; however, four false-positive foci were identified. The authors conclude that slow administration of 5 μmol/kg Mn-DPDP at a concentration of 10 μmol/mL is safe and efficient enough to proceed to further clinical trials. 相似文献