全文获取类型
收费全文 | 105021篇 |
免费 | 8750篇 |
国内免费 | 6163篇 |
专业分类
耳鼻咽喉 | 1114篇 |
儿科学 | 1561篇 |
妇产科学 | 2305篇 |
基础医学 | 12436篇 |
口腔科学 | 1962篇 |
临床医学 | 14073篇 |
内科学 | 16663篇 |
皮肤病学 | 908篇 |
神经病学 | 5677篇 |
特种医学 | 3676篇 |
外国民族医学 | 42篇 |
外科学 | 11245篇 |
综合类 | 14805篇 |
现状与发展 | 23篇 |
一般理论 | 20篇 |
预防医学 | 6127篇 |
眼科学 | 2864篇 |
药学 | 10742篇 |
56篇 | |
中国医学 | 4822篇 |
肿瘤学 | 8813篇 |
出版年
2024年 | 280篇 |
2023年 | 1503篇 |
2022年 | 3802篇 |
2021年 | 4970篇 |
2020年 | 3514篇 |
2019年 | 3232篇 |
2018年 | 3544篇 |
2017年 | 2923篇 |
2016年 | 2846篇 |
2015年 | 4418篇 |
2014年 | 5620篇 |
2013年 | 5015篇 |
2012年 | 7523篇 |
2011年 | 8268篇 |
2010年 | 4982篇 |
2009年 | 3821篇 |
2008年 | 5277篇 |
2007年 | 5555篇 |
2006年 | 5407篇 |
2005年 | 5705篇 |
2004年 | 3831篇 |
2003年 | 3401篇 |
2002年 | 3008篇 |
2001年 | 2443篇 |
2000年 | 2658篇 |
1999年 | 2718篇 |
1998年 | 1605篇 |
1997年 | 1512篇 |
1996年 | 1335篇 |
1995年 | 1186篇 |
1994年 | 1002篇 |
1993年 | 657篇 |
1992年 | 1015篇 |
1991年 | 815篇 |
1990年 | 696篇 |
1989年 | 618篇 |
1988年 | 611篇 |
1987年 | 537篇 |
1986年 | 434篇 |
1985年 | 344篇 |
1984年 | 212篇 |
1983年 | 167篇 |
1982年 | 92篇 |
1981年 | 106篇 |
1980年 | 90篇 |
1979年 | 118篇 |
1978年 | 61篇 |
1977年 | 70篇 |
1976年 | 53篇 |
1975年 | 48篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
M P Johnson X M Huang R Oberlender J F Nash D E Nichols 《European journal of pharmacology》1990,191(1):1-10
The present set of experiments was designed to examine the effects of extension of the alpha-methyl of p-chloroamphetamine (PCA) to an alpha-ethyl. Therefore, the alpha-ethyl homologue of PCA, 1-(4-chlorophenyl)-2-aminobutane (CAB), was compared to PCA in a number of pharmacological assays. CAB was 2-fold less potent than PCA at inhibiting synaptosomal uptake of [3H]5-hydroxytryptamine ([3H]5-HT), and 5-fold less potent at inhibiting uptake of [3H]dopamine ([3H]DA). In drug discrimination assays, CAB was approximately 3-fold less potent than PCA in animals trained to discriminate 3,4-methylenedioxymethamphetamine (MDMA) or its alpha-ethyl homologue, S-(+)-N-methyl-1-(1,3-benzodioxol-5-yl)-2-butanamine (S-(+)-MBDB), from saline. Monitoring with in vivo microdialysis, 10 mg/kg of PCA caused a large increase in extracellular DA and a significant decrease in 3,4-dihydroxyphenylacetic acid (DOPAC) in the striatum. In contrast, 11 mg/kg CAB caused no increase and 22 mg/kg CAB caused only a slight increase in extracellular DA. Both doses of CAB caused a decrease in extracellular DOPAC. The potential 5-HT neurotoxicity of CAB was examined by measuring monoamine and metabolite levels and [3H]paroxetine binding at one week following acute doses. A 10 mg/kg dose of PCA caused an 80% decrease in cortical and hippocampal serotonergic markers, while an equimolar dose of CAB decreased only hippocampal 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) levels. However, 22 mg/kg of CAB produced a 20-40% decrease in all serotonergic markers. Thus, extension of the alpha-alkyl significantly decreases the dopaminergic effects of PCA. The similar decrease in relative 5-HT neurotoxicity and the decreased ability to alter dopaminergic systems in vivo and in vitro supports the involvement of DA in the neurotoxicity of PCA. 相似文献
52.
53.
采用核桃仁泥外敷治疗138例(实验组)肌肉注射后皮下硬结,并与40例(对照组)采用新鲜土豆片外敷硬结法比较。结果表明:实验组患者治疗15天后Ⅰ度和Ⅱ度硬结治愈率分别为81.13%和42.25%,总有效率达92.03%,明显优于对照组(P<0.001)。 相似文献
54.
腹腔镜卵巢穿刺内凝治疗多囊卵巢不孕症的临床研究 总被引:2,自引:0,他引:2
目的探讨腹腔镜卵巢穿刺内凝对多囊卵巢不孕症的治疗价值。方法151例腹腔镜卵巢穿刺内凝术(实验组)和151例开腹卵巢楔切术(对照组)治疗多囊卵巢不孕症配对对比研究。结果实验组的手术时间33.1±7.2min,术中失血15.6±4.7ml,总排卵率92.05%,总妊娠率49.67%,均优于对照组(P<0.01);术后雄激素、LH/FSH下降幅度小于对照组(P<0.01)。随时间推移,两组术后排卵巢、妊娠率均有下降倾向,而术后雄激素、LH/FSH则有逐渐回升的倾向。结论腹腔镜卵巢穿刺内凝术对多囊卵巢不孕症有较好的治疗效果 相似文献
55.
红霉素对犬幽门括约肌压力影响及其与胃动素,生长抑素的关系 总被引:7,自引:2,他引:5
为探讨红霉素对犬幽门括约肌的作用及其机理,及其与血浆胃动素,生长抑素的关系。方法采用胃压力测量仪及放射免疫法,同步监测观察了10条犬静脉滴EM前后和使用拮抗剂后的幽门压力、血浆MTL,SS的变化,结论:EM具有增高犬胃幽门压力的作用,其作用机理除与血浆MTL有着密切的关系外,血浆SS也可能共同参与了其调节机制。 相似文献
56.
57.
The cellular and regional distribution of glutathione (GSH) and GSH-related enzyme systems involved in cellular defense against reactive oxygen species and electrophilic xenobiotics in the nervous system has been extensively studied. However, little is known about the subcellular distribution of GSH systems in brain tissue and cultured neural cells. The present study investigates the distribution of mitochondrial and cytosolic GSH and GSH-related enzymes in cultured cerebellar astrocytes and granule cells, and compares them with levels in the adult rat cerebellum. Cytosolic GSH levels and cytosolic activities of glutathione reductase (GR), glutathione peroxidase (GPx) and glutathione-S-transferase (GST) in astrocytes were 57, 153, 245, and 92% higher than those found in granule cells, respectively. In contrast, granule cells contained significantly higher mitochondrial GSH levels than astrocytes. Granule cells also demonstrated comparable mitochondria/cytosolic concentrations of GSH and GR, GPX and GST activities to those observed in the cerebellar tissue, whereas ratios in astrocytes were markedly lower. Although in vitro treatments with 100 μM ethacrynic acid depleted both cytosolic and mitochondrial GSH in cultured astrocytes and granule cells in a time-dependent fashion, cellular GSH in granule cells was more resistant to the GSH-depleting agent than astrocytes. These results suggest that although GSH and GSH-related enzymes are abundant in cytosolic compartments of astrocytes, mitochondrial pools are relatively small. Since brain mitochondria are sites of significant hydrogen peroxide generation, the mitochondrial localization of GSH and its associated enzymes in neural cells provide important defenses against toxic oxygen species in the nervous system. Differences in subcellular distribution of GSH systems in individual neural cell types may provide a basis for selective cellular and/or subcellular expression of neurotoxicity. 相似文献
58.
卡介苗激活杀伤细胞抗膀胱肿瘤作用研究 总被引:1,自引:0,他引:1
为了进一步探讨BCG抗膀胱肿瘤的作用机理,采取15例膀胱肿瘤患者外周血单个核细胞(PBMC),置于含BCG或IL2的培养基中培养,计算扩增倍数,检测培养细胞抗自体及异体膀胱癌细胞活性。结果:卡介苗激活杀伤细胞(BAK)与淋巴因子激活杀伤细胞(LAK)分别于培养第7和第3天达增殖高峰,对自体瘤杀伤率分别为36.2%和31.4%,差异有显著性(P<0.05);对异体瘤杀伤率分别为25.2%和28.3%,差异无显著性。结果表明:BAK细胞抗自体瘤活性高于LAK细胞,死BCG对PBMC无激活作用,BAK细胞抗肿瘤效应可能是BCG抗膀胱肿瘤重要作用机理之一。 相似文献
59.
60.
The prediction, based on unsteady diffusion kinetics, of the enhancement of reactivity and incorporation of 1-hexadecene in its copolymerization with propylene on adding a small amount of ethylene (increase from 5,2 mol-% to 10,8 mol-% when 2% of ethylene was added, and to 16, 1 mol-% when 5% was added) was verified in the terpolymerization of propylene/ 1-hexadecene/ ethylene on a commercial Solvay-type δ-TiCl3 catalyst. The catalyst efficiency was thus also increased. These augmentations originate from the increase in diffusion coefficient of 1-hexadecene at the catalyst surface when the PP crystallinity decreases on introduction of ethylene. Calculation based on unsteady diffusion kinetics showed that the order of diffusion coefficients ethylene > propylene > 1-hexadecene is reversed as the monomer concentration increases when the monomers are not at their equilibrium concentration. Sequence distribution as determined by means of 13C NMR revealed a tendency of blocky structure rather than a Bernoullian one. The terpolymer compositions obtained by means of an IR method developed in this work conform rather well with the NMR results. Results in this work not only support the unsteady diffusion kinetics but also provide a new route to prepare olefinic copolymer rubbers with heterogeneous titanium catalysts. 相似文献