全文获取类型
收费全文 | 3178篇 |
免费 | 224篇 |
国内免费 | 12篇 |
学科分类
医药卫生 | 3414篇 |
出版年
2021年 | 27篇 |
2020年 | 25篇 |
2019年 | 26篇 |
2018年 | 55篇 |
2017年 | 36篇 |
2016年 | 45篇 |
2015年 | 49篇 |
2014年 | 60篇 |
2013年 | 104篇 |
2012年 | 113篇 |
2011年 | 120篇 |
2010年 | 84篇 |
2009年 | 70篇 |
2008年 | 115篇 |
2007年 | 124篇 |
2006年 | 115篇 |
2005年 | 112篇 |
2004年 | 122篇 |
2003年 | 111篇 |
2002年 | 113篇 |
2001年 | 97篇 |
2000年 | 99篇 |
1999年 | 100篇 |
1998年 | 75篇 |
1997年 | 61篇 |
1996年 | 41篇 |
1995年 | 30篇 |
1994年 | 26篇 |
1993年 | 29篇 |
1992年 | 68篇 |
1991年 | 82篇 |
1990年 | 87篇 |
1989年 | 71篇 |
1988年 | 71篇 |
1987年 | 67篇 |
1986年 | 57篇 |
1985年 | 67篇 |
1984年 | 42篇 |
1983年 | 47篇 |
1982年 | 33篇 |
1981年 | 43篇 |
1980年 | 27篇 |
1979年 | 42篇 |
1978年 | 50篇 |
1977年 | 40篇 |
1976年 | 24篇 |
1975年 | 30篇 |
1974年 | 47篇 |
1973年 | 27篇 |
1969年 | 21篇 |
排序方式: 共有3414条查询结果,搜索用时 15 毫秒
1.
Three cases of cervical epidural hematoma are reported. Acute neck pain usually associated with a mild effort, closely followed by radicular pain and a neurologic deficit below the lesion is the typical presentation of this extremely rare and difficult diagnosis. As prognosis depends on preoperative neurologic state, the authors emphasize the importance of prompt identification of this lesion. The diagnosis is confirmed by computed tomography, and emergency neurosurgical laminectomy is mandatory. 相似文献
2.
3.
4.
5.
(S)-Emopamil ((2S)-2-isopropyl-5-(methylphenethylamino)-2-phenylvaleronitril e hydrochloride) is a novel compound of the phenylalkylamine group of calcium antagonists. (S)-Emopamil was tested in comparison to verapamil and gallopamil for calcium and serotonin antagonism and for cerebroprotective activity in acute hypoxia/ischemia. In receptor binding studies with (S)-3H-devapamil, (S)-emopamil exhibited distinct affinity to the verapamil binding site of the calcium channel. In rat cerebrocortical membranes, its affinity (Ki = 38 nmol/l) equalled that of verapamil and gallopamil (Ki = 49 and 27 nmol/l, respectively), whereas it was somewhat weaker in guinea pig skeletal muscle membranes. Comparing (S)-emopamil to its (R)-enantiomer, there was no clear stereoselectivity. Additionally, (S)-emopamil showed very high affinity to the cerebral serotonin S2 receptor; its Ki value (4.4 nmol/l) for 3H-ketanserin displacement being substantially lower than that of verapamil and gallopamil (Ki = 177 and 242 nmol/l, respectively). This feature is clearly stereoselective; (S)-emopamil's affinity was distinctly higher than that of the (R)-enantiomer (Ki = 58 nmol/l). The functional significance of (S)-emopamil's receptor affinity was tested in rat aortic strips. (S)-Emopamil's serotonin antagonistic efficacy (EC50 = 4.5 nmol/l) was an order of magnitude higher than that of verapamil and gallopamil. (S)-Emopamil has a less potent calcium antagonistic effect (EC50 = 270 nmol/l) on the aorta than verapamil and gallopamil (EC50 = 35 and 14 nmol/l, respectively). In isolated electrically driven (1 Hz) left atria of guinea pigs, (S)-emopamil inhibited contractile force at a much higher concentration (EC50 = 29 mumol/l) than verapamil and gallopamil (EC50 = 1.1 and 0.19 mumol/l, respectively).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
6.
Contact of teen mothers with grandmothers and partners was studied as a predictor of maternal and middle childhood developmental outcomes. Mothers were interviewed yearly beginning in 1979 until 1986. Each child was given a developmental assessment in 1986. Black teens lived longer with their parents after the child's birth and white teens married earlier and had more disruptions in their relationships. Grandmother assistance with childcare was positively associated with the mother's ability to pursue her education. The findings suggested, however, that child developmental problems may occur when mothers routinely rely upon grandmother assistance into middle childhood, particularly for white families. In general, a male partner who had regular contact with the mother's child, more stimulation and support in the home environment, and higher educational level of the mother were associated with better child developmental outcomes. 相似文献
7.
E C Unger M S Cohen R A Gatenby M R Clair T R Brown S J Nelson J S McGlone 《Journal of computer assisted tomography》1988,12(4):575-583
Single breath-holding gradient echo techniques fast imaging with steady-state free precession (FISP) and fast low angle shot (FLASH) images were evaluated in the study of the abdomen in 16 patients (13 liver, two kidney, and one pancreas examinations). Gradient echo images were compared retrospectively with conventional spin echo images for image quality (depiction of pathology and representation of anatomic detail), and contrast characteristics were evaluated. All lesions were shown on gradient echo images, and in three of 16 cases gradient echo images were more diagnostic than spin echo images. On both FISP and FLASH images, most hepatic metastases were hyperintense relative to normal liver. The predicted flip angles for maximal contrast for the liver were modeled from signal intensity equations for FISP and FLASH and yielded predicted flip angles of approximately 40-55 degrees for FISP and 15-25 degrees for FLASH. Peak signal-to-noise ratio in liver of normal volunteers occurred at approximately 30 degrees for both FISP and FLASH. Single breath-holding gradient echo images are useful in the evaluation of abdominal structures and this study provides a framework for future work. 相似文献
8.
Ytterbium-DTPA was evaluated as a potential intravascular contrast agent. Ytterbium-DTPA was synthesized from ytterbium oxide and diethylene triamine penta-acetic acid (DTPA). CT scans of increasing concentrations of ytterbium and iodine showed that at 125 kVp, ytterbium was denser than an equal concentration of iodine. The LD50 of intravenous ytterbium-DTPA was 10 mM/kg (1.73 g ytterbium/kg) in rats. In enhanced CT scans and pulmonary angiography in dogs, ytterbium was visibly denser than iodine, and CT Hounsfield units showed greater enhancement of the aorta and inferior vena cava with ytterbium. The animals showed no sign of acute or delayed toxicity. Ytterbium-DTPA deserves further evaluation as a contrast agent for high kVp techniques. 相似文献
9.
Effect of converting enzyme inhibitors on tissue converting enzyme and angiotensin II: therapeutic implications 总被引:1,自引:0,他引:1
Local tissue renin-angiotensin systems have recently been discovered in various organs, and evidence is accumulating that inhibition of these local renin-angiotensin systems may contribute to the actions of converting enzyme (CE) inhibitors. Measurements of CE activity and angiotensin II concentrations revealed that after oral administration of CE inhibitors, CE was inhibited not only in lung vascular endothelium and blood, but also in the heart, kidney, vascular wall, brain and other organs. The functional significance of tissue CE inhibition is suggested first by the antihypertensive effect of brain CE inhibition in spontaneously hypertensive rats, second by the concomitant persistence of blood pressure decrease and CE inhibition in vascular wall and kidney after long-term oral CE inhibitor treatment and third by ex vivo experiments demonstrating marked effects of oral CE inhibitor pretreatment on cardiac function in isolated rat hearts. Local inhibition of tissue renin-angiotensin systems may be an important factor involved in the beneficial effects of CE inhibitors in such cardiovascular diseases as arterial hypertension, congestive heart failure and cardiac arrhythmias. 相似文献
10.
Lenka A. Taylor Jann Arends Arwen K. Hodina Clemens Unger Ulrich Massing 《Lipids in health and disease》2007,6(1):17