全文获取类型
收费全文 | 8679篇 |
免费 | 534篇 |
国内免费 | 28篇 |
专业分类
耳鼻咽喉 | 141篇 |
儿科学 | 231篇 |
妇产科学 | 343篇 |
基础医学 | 1340篇 |
口腔科学 | 143篇 |
临床医学 | 785篇 |
内科学 | 1632篇 |
皮肤病学 | 90篇 |
神经病学 | 795篇 |
特种医学 | 357篇 |
外科学 | 895篇 |
综合类 | 57篇 |
一般理论 | 3篇 |
预防医学 | 835篇 |
眼科学 | 87篇 |
药学 | 793篇 |
中国医学 | 14篇 |
肿瘤学 | 700篇 |
出版年
2021年 | 89篇 |
2020年 | 56篇 |
2019年 | 101篇 |
2018年 | 125篇 |
2017年 | 67篇 |
2016年 | 95篇 |
2015年 | 129篇 |
2014年 | 190篇 |
2013年 | 280篇 |
2012年 | 387篇 |
2011年 | 448篇 |
2010年 | 226篇 |
2009年 | 206篇 |
2008年 | 416篇 |
2007年 | 420篇 |
2006年 | 436篇 |
2005年 | 453篇 |
2004年 | 445篇 |
2003年 | 422篇 |
2002年 | 358篇 |
2001年 | 216篇 |
2000年 | 181篇 |
1999年 | 183篇 |
1998年 | 110篇 |
1997年 | 108篇 |
1996年 | 116篇 |
1995年 | 106篇 |
1994年 | 102篇 |
1993年 | 109篇 |
1992年 | 159篇 |
1991年 | 187篇 |
1990年 | 146篇 |
1989年 | 125篇 |
1988年 | 128篇 |
1987年 | 104篇 |
1986年 | 105篇 |
1985年 | 108篇 |
1984年 | 119篇 |
1983年 | 102篇 |
1982年 | 78篇 |
1981年 | 77篇 |
1980年 | 81篇 |
1979年 | 89篇 |
1978年 | 65篇 |
1977年 | 59篇 |
1976年 | 69篇 |
1975年 | 64篇 |
1974年 | 84篇 |
1973年 | 83篇 |
1972年 | 58篇 |
排序方式: 共有9241条查询结果,搜索用时 0 毫秒
41.
42.
Arne Popma Robert Vermeiren Charlotte A M L Geluk Thomas Rinne Wim van den Brink Dirk L Knol Lucres M C Jansen Herman van Engeland Theo A H Doreleijers 《Neuropsychopharmacology》2007,61(3):405-411
BACKGROUND: In animals, strong evidence exists for an association between testosterone and aggression. In humans, and particularly in children and adolescents, findings have been less consistent. Previous research has suggested that this may partly be due to moderating effects of other factors, e.g., hormones. This study aims to investigate the moderating effect of cortisol on the relationship between testosterone and subtypes of aggression in delinquent male adolescents. METHODS: Participants were 103 boys (mean age 13.7) referred to a delinquency diversion program. Testosterone and cortisol levels were determined from saliva samples collected during resting conditions and related to self-report scores on overt and covert aggression. RESULTS: Linear regression analyses revealed a significant interaction between cortisol and testosterone in relation to overt aggression, with a significant positive relationship between testosterone and overt aggression in subjects with low cortisol levels but not in subjects with high cortisol levels. Using the same model for covert aggression, no significant effects of testosterone, cortisol, or testosterone x cortisol interaction were found. CONCLUSIONS: These results indicate a moderating effect of cortisol on the relationship between testosterone and overt aggression in delinquent male adolescents. Implications and directions for future research are discussed. 相似文献
43.
GABAergic Transmission in the Nucleus Accumbens Is Involved in the Termination of Ethanol Self-Administration in Rats 总被引:6,自引:0,他引:6
Clyde W. Hodge Ann M. Chappelle Herman H. Samson 《Alcoholism, clinical and experimental research》1995,19(6):1486-1493
Long-Evans rats ( n = 12) were trained to lever-press on a fixed-ratio 4 schedule of reinforcement with ethanol (10% v/v) presented as the reinforcer. After implantation of bilateral stainless-steel guide cannulae aimed at the nucleus accumbens, site-specific microinjections of muscimol (1–30 ng) and bicuculline (1–10 ng) were tested for effects on ethanol-reinforced responding. Baseline response patterns were characterized by initial high rates that terminated abruptly after ∼20 min. Muscimol administration in the nucleus accumbens decreased the total number of ethanol-reinforced responses and obtained reinforcers. Bicuculline also decreased ethanol-reinforced responses and reinforcers at the highest dose tested. When a dose of bicuculline (1 ng) that was ineffective by itself was coadministered with an effective dose of muscimol (10 ng), the muscimol-induced decreases in responding were blocked. Analysis of response patterns showed that muscimol decreased ethanol self-administration by terminating responding, normally lasting 20 min, after ∼10 min with no changes in local response rate. Bicuculline decreased total responding by producing parallel, but nonsignificant, changes in time course and response rate. These data suggest that GABAergic transmission in the nucleus accumbens is involved in the termination, but not the onset or maintenance of ethanol self-administration. The specificity of this effect gives emphasis to the importance of measuring behavioral parameters, as well as products of behavior (such as intake volume) in the study of ethanol self-administration. 相似文献
44.
45.
46.
Determining mechanisms that can increase ethanol consumption during a single drinking bout is central to understanding alcohol abuse. When rodents are used as models to study excessive drinking, most often limited and transient increases in bout size are found with various manipulations. In a variety of studies, investigators have reported that schedule-induced drinking can result in excessive consumption of either water or alcohol (ethanol) during a single drinking period in food-restricted rats. The question examined in this experiment was, Could a schedule-induction paradigm increase bout size in nondeprived rats already self-administering ethanol? After the rats were trained to self-administer a 10% (volume/volume) ethanol solution in a fixed daily drinking session, non-response-contingent presentation of a 10% (weight/volume) sucrose solution, on a fixed-time, 120-s schedule, was used to determine whether additional ethanol consumption could be induced. This was followed by the use of a fixed-time, 300-s schedule and then, by using the fixed-time, 120-s schedule, with the presentation of a 2% (weight/volume) sucrose solution. None of these conditions induced an increase in ethanol self-administration. The results indicate that factors that control ethanol bout size in the nondeprived rat are such that the standard schedule-induction condition seems to be ineffective if an ethanol bout has occurred in the recent past. 相似文献
47.
48.
GABAA receptor-mediated stimulation of non-adrenergic non-cholinergic neurones in the dog ileocolonic junction. 总被引:4,自引:4,他引:0 下载免费PDF全文
G. E. Boeckxstaens P. A. Pelckmans M. Rampart I. F. Ruytjens T. J. Verbeuren A. G. Herman Y. M. Van Maercke 《British journal of pharmacology》1990,101(2):460-464
1. The inhibitory effects of gamma-aminobutyric acid (GABA), the GABAA receptor agonist homotaurine and the GABAB receptor agonist (+/-)-baclofen were investigated on circular muscle strips of the dog terminal ileum and ileocolonic junction. 2. In the presence of atropine, GABA and homotaurine induced concentration-dependent relaxations, similar to the non-adrenergic non-cholinergic (NANC)-mediated relaxations evoked by electrical stimulation or by acetylcholine. The ileocolonic junction was more sensitive to GABA and homotaurine than the ileum. (+/-)-Baclofen had no effect. Cross desensitization only occurred between GABA and homotaurine. 3. The GABAA receptor antagonist bicuculline shifted the concentration-response curves to GABA and homotaurine to the right. The maximal relaxation to GABA remained unaffected. 4. GABA-induced relaxations were not inhibited by timolol, guanethidine, domperidone, hexamethonium and desensitization to ATP, but were abolished by tetrodotoxin. 5. Bicuculline, and pretreatment with GABA or (+/-)-baclofen had no effect on the NANC-evoked relaxations to electrical stimulation and acetylcholine. 6. In conclusion, GABA stimulates GABAA receptors located on inhibitory NANC neurones in the dog ileocolonic junction. Our results suggest that it is unlikely that GABA is the final inhibitory NANC neurotransmitter. 相似文献
49.
Altered swelling behavior of femoral cartilage following joint immobilization in a canine model. 总被引:3,自引:0,他引:3
Daria A Narmoneva Herman S Cheung Jean Y Wang David S Howell Lori A Setton 《Journal of orthopaedic research》2002,20(1):83-91
Periods of reduced joint loading have been shown to induce changes in the biochemical composition. metabolism and mechanics of articular cartilage. In this study, changes in cartilage swelling behavior were studied following a 4-week period of joint immobilization, using a recently developed osmotic loading technique [J. Biomech, 32 (1999) 401-408]. The magnitude and distribution of swelling strains were measured in cartilage-bone samples equilibrated in physiological and hypotonic saline, relative to a hypertonic reference NaCl solution. Physicochemical parameters (glycosaminoglycan fixed charge density and water volume fraction) were determined in site-matched cartilage samples. The experimental data for swelling strains, fixed charge density and water volume fraction were used with a triphasic mechano-chemical theory [J. Biomech. Eng. 113 (1991) 245-258] to determine the effect of joint immobilization on the tensile modulus of the cartilage solid matrix. Four weeks of immobilization resulted in a significant increase in the magnitude of swelling-induced strains, and a significant decrease in fixed charge density in cartilage, as compared with the contralateral controls. Joint immobilization also resulted in decreases in values for the modulus of cartilage, as compared with the contralateral controls. Our results suggest that 4 weeks of joint immobilization had a significant effect on cartilage mechanical function that may be linked to collagen changes in the cartilage extracellular matrix. 相似文献
50.