全文获取类型
收费全文 | 1045篇 |
免费 | 0篇 |
专业分类
化学工业 | 7篇 |
机械仪表 | 1篇 |
能源动力 | 1篇 |
轻工业 | 2篇 |
一般工业技术 | 5篇 |
冶金工业 | 1029篇 |
出版年
2022年 | 1篇 |
2019年 | 1篇 |
2011年 | 2篇 |
2010年 | 2篇 |
2009年 | 1篇 |
2008年 | 1篇 |
2007年 | 1篇 |
2005年 | 4篇 |
2003年 | 1篇 |
1999年 | 18篇 |
1998年 | 307篇 |
1997年 | 202篇 |
1996年 | 117篇 |
1995年 | 68篇 |
1994年 | 59篇 |
1993年 | 54篇 |
1992年 | 7篇 |
1991年 | 15篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 19篇 |
1987年 | 13篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1978年 | 7篇 |
1977年 | 28篇 |
1976年 | 59篇 |
1975年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有1045条查询结果,搜索用时 0 毫秒
21.
22.
23.
24.
25.
26.
OBJECTIVES: To compare transesophageal atrial pacing stress echocardiography with dobutamine stress echocardiography for feasibility, safety, duration, patient acceptance and concordance in inducing wall motion abnormalities. BACKGROUND: Transesophageal atrial pacing is an effective method of increasing heart rate and has been used in the assessment of coronary artery disease. METHODS: Both tests were performed in sequence on the same patients in random order. Transesophageal atrial pacing stress echocardiography began at a heart rate of 10 beats/min above the baseline value and was increased by 20 beats/min every two min until 85% of the age-predicted maximum heart rate or another end point was reached. Dobutamine echocardiography was performed using three-min stages and a maximum dose of 40 microg/kg per min. Atropine (total dose < or =2 mg) was administered at the start of the 40 microg/kg per min stage if needed to augment heart rate or during pacing if Wenckebach heart block occurred. RESULTS: Transesophageal atrial pacing stress echocardiography was feasible in 100 of 104 patients (96%); the duration (8.6+/-3.6 min) was significantly shorter than that of dobutamine stress echocardiography (15.1+/-3.9 min) (p = 0.0001). With transesophageal atrial pacing stress echocardiography, the recovery period was shorter, symptoms and dysrhythmias were fewer, hypertension and hypotension were less common and target heart rate was more frequently achieved. No complications occurred with either test. Patient acceptance was satisfactory. Agreement between results of both tests was good for segmental wall motion scoring with a 16-segment model, scores 1 to 5 (kappa: rest, 0.79; peak, 0.57) and test interpretation (normal, ischemia, infarction or resting wall motion abnormality with ischemia) (kappa: 0.77). CONCLUSIONS: Transesophageal atrial pacing stress echocardiography is a feasible, well-tolerated alternative to dobutamine stress echocardiography. It can be performed rapidly and shows good agreement with dobutamine stress echocardiography in the induction of myocardial ischemia. 相似文献
27.
28.
29.
RA Dickson MV Seeman 《Canadian Metallurgical Quarterly》1997,154(12):1792; author reply 1793-1792; author reply 1794
30.
A new fluorogenic reagent, 2-methyl-3-oxo-4-phenyl-2,3-dihydrofuran-2-yl acetate, has been developed for the analysis of primary amines and aminated carbohydrates by means of HPLC, CE, and MALDI/MS. Peptides at 1 pmol (2 x 10(-7) M) levels were successfully labeled and analyzed through CE. The fluorescent derivatives have good stability in both acidic and basic solutions, making their further manipulation and structural analysis possible. The derivatives can be analyzed in reversed-phase HPLC due to the hydrophobic nature of this fluorescent tag. Characteristic elution intervals between the diastereomeric peaks of the chiral peptide derivatives may be used in structural verification. The labeled peptides and neutral oligosaccharides are also readily detectable through MALDI/MS in its positive mode. 相似文献