全文获取类型
收费全文 | 47551篇 |
免费 | 4421篇 |
国内免费 | 75篇 |
专业分类
耳鼻咽喉 | 620篇 |
儿科学 | 1271篇 |
妇产科学 | 1329篇 |
基础医学 | 6843篇 |
口腔科学 | 1261篇 |
临床医学 | 5856篇 |
内科学 | 8338篇 |
皮肤病学 | 615篇 |
神经病学 | 3794篇 |
特种医学 | 2145篇 |
外国民族医学 | 1篇 |
外科学 | 6201篇 |
综合类 | 879篇 |
一般理论 | 23篇 |
预防医学 | 5281篇 |
眼科学 | 1094篇 |
药学 | 3545篇 |
2篇 | |
中国医学 | 56篇 |
肿瘤学 | 2893篇 |
出版年
2021年 | 664篇 |
2019年 | 643篇 |
2018年 | 757篇 |
2017年 | 638篇 |
2016年 | 615篇 |
2015年 | 716篇 |
2014年 | 964篇 |
2013年 | 1497篇 |
2012年 | 2140篇 |
2011年 | 2226篇 |
2010年 | 1217篇 |
2009年 | 996篇 |
2008年 | 1875篇 |
2007年 | 2025篇 |
2006年 | 2014篇 |
2005年 | 2008篇 |
2004年 | 1825篇 |
2003年 | 1670篇 |
2002年 | 1708篇 |
2001年 | 1610篇 |
2000年 | 1709篇 |
1999年 | 1450篇 |
1998年 | 640篇 |
1997年 | 521篇 |
1996年 | 526篇 |
1995年 | 525篇 |
1994年 | 445篇 |
1993年 | 446篇 |
1992年 | 1261篇 |
1991年 | 1162篇 |
1990年 | 1150篇 |
1989年 | 1074篇 |
1988年 | 990篇 |
1987年 | 995篇 |
1986年 | 916篇 |
1985年 | 915篇 |
1984年 | 717篇 |
1983年 | 627篇 |
1982年 | 451篇 |
1981年 | 392篇 |
1980年 | 408篇 |
1979年 | 660篇 |
1978年 | 525篇 |
1977年 | 417篇 |
1976年 | 405篇 |
1975年 | 377篇 |
1974年 | 451篇 |
1973年 | 441篇 |
1972年 | 450篇 |
1971年 | 424篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
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
33.
A. Robert Spitzer Shalom Stahl David Yarnitsky Ernest W. Johnson John R. Wilson R. A. C. Hughes Stefania Morino Giovanni Antonini Kiyotoshi Kaneko Yoji Ohnishi Tetsushi Atsumi Isao Hozumi Tadashi Miyatake Tetsuo Furukawa James P. Knochel Ikuo Mineo Seiichiro Tarui Francis O. Walker Andrew J. Gitter Walter C. Stolov Nicholas J. Capozzoli 《Muscle & nerve》1996,19(4):531-538
34.
35.
Ten patients with rheumatoid arthritis (RA) were evaluated in a placebo-controlled, double-blind study examining the clinical efficacy of a novel nonsteroidal anti-inflammatory agent: Tenidap (CP-66,248). RA patients receiving active drug therapy (n = 6) demonstrated clinically significant improvements in observer assessment of pain (p less than 0.025), painful joint count (p less than 0.010), and overall clinical assessment as based on a modified rheumatoid activity index, MRAI (p less than 0.025). In parallel laboratory assays, Tenidap was found to exhibit a significant in vitro dose-dependent inhibition of ionophore-stimulated neutrophil production of the 5-lipoxygenase product: [3H]leukotriene B4 (LTB4). Although more importantly, Tenidap was also found to exhibit an in vitro dose-dependent inhibition (IC50 20 microM) of the ionophore-stimulated release (deacylation) of the precursor [3H]arachidonic acid (AA) from membrane phospholipids. In further studies, Tenidap did not have any effect on fMLP-induced neutrophil chemotactic response. These results suggest that one of the possible mechanisms for the clinical effectiveness of this agent, may be through its effect at inhibiting the release of free AA from membrane phospholipids and therefore limiting its further metabolism into certain biologically-active inflammatory lipids. 相似文献
36.
This paper describes studies aimed at determining the acute anticholinergic and delayed neurotoxic potential of the organophosphate insecticide pirimiphos-methyl (O-2-diethylamino-6-methylpyrimidin-4-yl O,O-dimethyl phosphorothioate) in the hen. Delayed neuropathy was assessed by biochemical measurement of neuropathy target esterase (NTE) activities in the brain and spinal cord, clinical signs of neuropathy over two 21-day periods and histological assessment of nervous tissue. Acetylcholinesterase (AChE) activity was also determined in the brain and spinal cord. Hens were given a single oral dose of 100 mg kg-1 pirimiphos-methyl, which was followed by a repeated dose after 21 days. Tri-o-cresyl phosphate (TOCP), 500 mg kg-1, was used as a positive control. All pirimiphos-methyl-treated hens received prophylactic doses of N-methylpyridinium-2-aldoxime methanesulphonate (P2S) and atropine sulphate. Hens dosed with pirimiphos-methyl had very low AChE activities (less than 20% of control) in both the brain and spinal cord, 24 and 48 h after dosing. In the TOCP-treated hens, the activities were about 90% of control. NTE activities in the brain and spinal cord of pirimiphos-methyl-treated hens were identical to those in the controls, while they were profoundly inhibited (greater than 80%) in the TOCP-treated hens. All hens dosed with pirimiphos-methyl showed the expected signs of AChE inhibition and, following recovery, usually by Day 5, no clinical signs of delayed neuropathy were seen. The TOCP-treated hens developed clinical signs of neuropathy.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
37.
OBJECTIVES: The purpose of this study was to identify individual characteristics associated with types and frequency of milk consumption in older American adults. METHODS: A national probability-based sample (response rate = 91%) completed a telephone survey. Generalized logit and cumulative logit analyses were used to identify predictors of and barriers to fluid milk consumption in 494 elderly people. RESULTS: The likelihood of drinking skim or 1% milk rather than whole milk increased with nutrition knowledge, income, trying to reduce cholesterol intake, and being female (P < .05). Frequency of milk consumption was higher with nutrition knowledge, frequency of milk consumption during adolescence, and following a diabetic diet but was lower with milk intolerance. CONCLUSIONS: The present results could be used to develop intervention strategies for improving milk consumption rates among older adults. These strategies might focus on increasing elderly people's awareness of milk intolerance and lactose-reduced milk products and their concern about cholesterol. The relationship between current and adolescent milk consumption suggests that intervention strategies should begin early in life. 相似文献
38.
Patrick M. Rao M.D. A. John Kuta M.D. Michele H. Johnson M.D. 《Emergency radiology》1995,2(5):303-304
We present a case in which an open fracture of the ulna penetrated the skull and caused a comminuted, depressed skull fracture
with a large intraparenchymal hematoma containing bone fragments. 相似文献
39.
J M Johnson 《The Journal of the American Osteopathic Association》1990,90(4):346-351
Clinicians and researchers alike have questioned and studied the origin of schizophrenia for decades. Since the early 1900s, a genetic hypothesis has been suggested. This article reviews studies on a possible genetic cause of schizophrenia by use of various methods of comparison: twins, adoption, family history, family studies, and studies of biologic markers. Most researchers conclude that schizophrenia is likely caused by a genetic predisposition coupled with environmental influences. 相似文献
40.