收费全文 | 7677篇 |
免费 | 354篇 |
国内免费 | 55篇 |
耳鼻咽喉 | 43篇 |
儿科学 | 124篇 |
妇产科学 | 94篇 |
基础医学 | 1370篇 |
口腔科学 | 100篇 |
临床医学 | 641篇 |
内科学 | 1178篇 |
皮肤病学 | 280篇 |
神经病学 | 906篇 |
特种医学 | 267篇 |
外科学 | 1056篇 |
综合类 | 48篇 |
一般理论 | 2篇 |
预防医学 | 377篇 |
眼科学 | 240篇 |
药学 | 667篇 |
中国医学 | 10篇 |
肿瘤学 | 683篇 |
2023年 | 24篇 |
2022年 | 58篇 |
2021年 | 98篇 |
2020年 | 51篇 |
2019年 | 92篇 |
2018年 | 84篇 |
2017年 | 68篇 |
2016年 | 97篇 |
2015年 | 143篇 |
2014年 | 167篇 |
2013年 | 286篇 |
2012年 | 405篇 |
2011年 | 439篇 |
2010年 | 279篇 |
2009年 | 265篇 |
2008年 | 472篇 |
2007年 | 547篇 |
2006年 | 502篇 |
2005年 | 583篇 |
2004年 | 490篇 |
2003年 | 538篇 |
2002年 | 492篇 |
2001年 | 98篇 |
2000年 | 89篇 |
1999年 | 117篇 |
1998年 | 142篇 |
1997年 | 100篇 |
1996年 | 83篇 |
1995年 | 69篇 |
1994年 | 63篇 |
1993年 | 76篇 |
1992年 | 44篇 |
1991年 | 77篇 |
1990年 | 48篇 |
1989年 | 45篇 |
1988年 | 32篇 |
1987年 | 35篇 |
1986年 | 39篇 |
1985年 | 36篇 |
1984年 | 36篇 |
1983年 | 33篇 |
1982年 | 42篇 |
1981年 | 37篇 |
1980年 | 34篇 |
1979年 | 32篇 |
1978年 | 33篇 |
1977年 | 31篇 |
1976年 | 22篇 |
1975年 | 27篇 |
1974年 | 26篇 |
Background
The efficacy of dexamethasone in extending the duration of local anaesthetic block is uncertain. In a randomised controlled triple blind crossover study in volunteers, we tested the hypothesis that neither i.v. nor perineurally administered dexamethasone prolongs the sensory block achieved with ropivacaine.Methods
Ultrasound-guided ulnar nerve blocks (ropivacaine 0.75% wt/vol, 3 ml, with saline 1 ml with or without dexamethasone 4 mg) were performed on three occasions in 24 male volunteers along with an i.v. injection of saline 1 ml with or without dexamethasone 4 mg. The combinations of saline and dexamethasone were as follows: control group, perineural and i.v. saline; perineural group, perineural dexamethasone and i.v. saline; i.v. group, perineural saline and i.v. dexamethasone. Sensory block was measured using a VAS in response to pinprick testing. The duration of sensory block was the primary outcome and time to onset of sensory block the secondary outcome.Results
All 24 subjects completed the trial. The median [inter-quartile range (IQR)] duration of sensory block was 6.87 (5.85–7.62) h in the control group, 7.37 (5.78–7.93) h in the perineural group and 7.37 (6.10–7.97) h in the i.v. group (P=0.61). There was also no significant difference in block onset time between the three groups.Conclusion
Dexamethasone 4 mg has no clinically relevant effect on the duration of sensory block provided by ropivacaine applied to the ulnar nerve.Clinical trial registration
DRKS, 00014604; EudraCT, 2018-001221-98. 相似文献Methods: By extension of a previously published interaction model, the authors propose a method to study drug interactions considering also their side effects. A general outcome parameter identified as patient's well-being is defined by superposition of positive and negative effects. Well-being response surfaces are computed and analyzed for varying drugs pharmacodynamics and interaction types. In particular, the existence of multiple maxima and of optimal drug combinations is investigated for the combination of two drugs.
Results: Both drug pharmacodynamics and interaction type affect the well-being surface and the deriving optimal combinations. The effect of the interaction parameters can be explained in terms of synergy and antagonism and remains unchanged for varying pharmacodynamics. For all simulations performed for the combination of two drugs, the presence of more than one maximum was never observed. 相似文献
Methods: Rats (n = 30) were injected with varying doses (0.625, 2.5, and 10 U) of botulinum toxin into the tibialis muscle. Control animals (n = 9) received an equivalent volume of saline. At 128 days after injection, neuromuscular function, pharmacodynamics of atracurium, and nAChRs were evaluated.
Results: Nerve-evoked tensions, including tetanic tension and muscle mass, were decreased on the toxin-injected side in a dose-dependent manner relative to saline-injected controls as well as the contralateral side. Specific muscle tension and specific tetanic muscle tension (tensions/muscle mass) were not reduced. The ED10 of atracurium was reduced, the ED50 was unchanged, and the ED90 was increased in the highest (10-U) dose of toxin group. The atracurium plasma concentration to maintain a steady state 50% paralysis was significantly reduced in the 10-U toxin group. The nAChR concentrations in the tibialis muscle were significantly increased in a dose-dependent manner in all experimental groups. 相似文献
Method: One hundred Enteritidis isolates dating from 1989 to 1994 which could be allocated epidemiologically to different sources or to small community outbreaks were investigated with ribotyping, a fingerprinting method in which bacterial DNA is hybridized with the biotin-labeled plasmid pKK 3535 containing a ribosomal RNA operon of Escherichia coli to determine the ribosomal RNA gene restriction patterns.
Results: Four different ribotyping patterns were found with the restriction endonuclease Sma I and nine with Sph I. Ribotypes of isolates which could be allocated epidemiologically to a common source usually corresponded. Almost 60% of the Enteritidis infections had the ribotyping pattern Sph I-A. In contrast, this pattern was not found in any of the five Enteritidis strains isolated in 1989. The suspicion that Enteritidis phage type 4 infections are caused by consumption of insufficiently heated eggs is supported by the fact that the ribotyping pattern Sph 1-A was found in isolates from eggs and from human specimens.
Conclusions: As patterns Sph I-A and Sma I-J appeared in 58% and 75% of the isolates, respectively, ribotyping cannot be used for the differentiation between various outbreaks with these two patterns. In cases where the Enteritidis strains showed less frequent patterns, ribotyping seems to be a practical tool for the identification of infection chains. In addition newly appearing ribotyping patterns can give information about the epidemiologic development of Enteritidis infection. 相似文献