收费全文 | 1380篇 |
免费 | 87篇 |
国内免费 | 209篇 |
耳鼻咽喉 | 1篇 |
儿科学 | 70篇 |
妇产科学 | 10篇 |
基础医学 | 178篇 |
口腔科学 | 21篇 |
临床医学 | 198篇 |
内科学 | 289篇 |
皮肤病学 | 51篇 |
神经病学 | 48篇 |
特种医学 | 300篇 |
外科学 | 322篇 |
综合类 | 24篇 |
预防医学 | 40篇 |
眼科学 | 5篇 |
药学 | 60篇 |
中国医学 | 2篇 |
肿瘤学 | 57篇 |
2023年 | 4篇 |
2022年 | 3篇 |
2021年 | 9篇 |
2020年 | 9篇 |
2019年 | 9篇 |
2018年 | 17篇 |
2017年 | 3篇 |
2016年 | 8篇 |
2015年 | 14篇 |
2014年 | 18篇 |
2013年 | 42篇 |
2012年 | 31篇 |
2011年 | 24篇 |
2010年 | 41篇 |
2009年 | 57篇 |
2008年 | 33篇 |
2007年 | 83篇 |
2006年 | 51篇 |
2005年 | 46篇 |
2004年 | 40篇 |
2003年 | 60篇 |
2002年 | 58篇 |
2001年 | 50篇 |
2000年 | 43篇 |
1999年 | 52篇 |
1998年 | 84篇 |
1997年 | 86篇 |
1996年 | 113篇 |
1995年 | 69篇 |
1994年 | 60篇 |
1993年 | 54篇 |
1992年 | 22篇 |
1991年 | 26篇 |
1990年 | 27篇 |
1989年 | 45篇 |
1988年 | 40篇 |
1987年 | 36篇 |
1986年 | 46篇 |
1985年 | 40篇 |
1984年 | 9篇 |
1983年 | 17篇 |
1982年 | 14篇 |
1981年 | 9篇 |
1980年 | 12篇 |
1979年 | 8篇 |
1978年 | 12篇 |
1977年 | 9篇 |
1976年 | 13篇 |
1975年 | 13篇 |
1973年 | 2篇 |
Methods: Eight healthy volunteers received intrathecal injection of morphine (50 [mu]g) plus fentanyl (50 [mu]g) at a lower lumbar interspace. CSF was sampled through a needle in an upper lumbar interspace for 60-120 min. At the end of this time, a sample was taken from the lower lumbar needle, and both needles were withdrawn. CSF volume was determined by magnetic resonance imaging. Pharmacokinetic modeling was performed with NONMEM.
Results: Morphine and fentanyl peaked in CSF at the cephalad needle at similar times (41 +/- 13 min for fentanyl, 57 +/- 12 min for morphine). The ratio of morphine to fentanyl in CSF at the cephalad needle increased with time, surpassing 2:1 by 36 min and 4:1 by 103 min. CSF concentrations did not correlate with weight, height, or lumbosacral CSF volume. The concentrations of morphine and fentanyl at both sampling sites were well described by a simple pharmacokinetic model. The individual model parameters did not correlate with the distance between the needles, CSF volume, patient height, or patient weight. 相似文献
Methods: The withdrawal threshold to von Frey filament testing and withdrawal latency to hind-paw radiant heating were determined before and for various times after hind-paw incision in rats 2, 4, and 16 weeks of age. Control rats of these ages were observed serially without surgery.
Results: In control animals, younger rats were more sensitive to mechanical stimulation and less sensitive to thermal stimulation. Paw incision resulted in similar changes to both types of stimulation in all age groups, peaking 4 h after surgery. However, the return to normal sensitivity to mechanical stimulation, as measured by return of threshold to 80% of normal, occurred more quickly in 2-week-old than in 4- and 16-week-old animals. In contrast, there was no age difference for time to return to normal sensitivity to thermal stimulation after surgery. 相似文献
Methods: Gabapentin was administered orally and intracerebroventricularly to rats on the day after paw incision, and withdrawal threshold to paw pressure was measured. The authors also measured cerebrospinal fluid concentration of norepinephrine and postoperative morphine use after surgery in patients who received oral placebo or gabapentin.
Results: Both oral and intracerebroventricular gabapentin attenuated postoperative hypersensitivity in rats in a dose-dependent manner. This effect of gabapentin was blocked by intrathecal administration of the [alpha]2-adrenergic receptor antagonist idazoxan and the G protein-coupled inwardly rectifying potassium channel antagonist tertiapin-Q, but not by atropine. In humans, preoperative gabapentin, 1,200 mg, significantly increased norepinephrine concentration in cerebrospinal fluid and decreased morphine requirements. 相似文献
Methods: Female Sprague-Dawley rats were anesthetized, and the left L5 and L6 spinal nerves were ligated. Animals received either intrathecal saline or milnacipran (0.1-3 [mu]g), and withdrawal thresholds to mechanical testing in the left hind paw, using von Frey filaments, and visceral testing, using balloon colorectal distension, were determined.
Results: Nerve ligation resulted in decreases in threshold to withdrawal to somatic mechanical stimulation (from 13 +/- 1.8 g to 2.7 +/- 0.7 g) and also in decreases in threshold to reflex response to visceral stimulation (from 60 mmHg to 40 mmHg). Intrathecal milnacipran increased withdrawal threshold to somatic stimulation in a dose-dependent manner but failed to alter the response to noxious visceral stimulation. 相似文献