全文获取类型
收费全文 | 5406933篇 |
免费 | 402334篇 |
国内免费 | 15625篇 |
专业分类
耳鼻咽喉 | 76807篇 |
儿科学 | 174082篇 |
妇产科学 | 144814篇 |
基础医学 | 801021篇 |
口腔科学 | 150328篇 |
临床医学 | 500010篇 |
内科学 | 985213篇 |
皮肤病学 | 127507篇 |
神经病学 | 445238篇 |
特种医学 | 208782篇 |
外国民族医学 | 1148篇 |
外科学 | 810059篇 |
综合类 | 147492篇 |
现状与发展 | 24篇 |
一般理论 | 3030篇 |
预防医学 | 449726篇 |
眼科学 | 129758篇 |
药学 | 386493篇 |
28篇 | |
中国医学 | 13860篇 |
肿瘤学 | 269472篇 |
出版年
2021年 | 57321篇 |
2019年 | 59547篇 |
2018年 | 77510篇 |
2017年 | 59485篇 |
2016年 | 66180篇 |
2015年 | 77944篇 |
2014年 | 112440篇 |
2013年 | 178102篇 |
2012年 | 157608篇 |
2011年 | 168886篇 |
2010年 | 136370篇 |
2009年 | 134184篇 |
2008年 | 153944篇 |
2007年 | 166197篇 |
2006年 | 172812篇 |
2005年 | 166771篇 |
2004年 | 166702篇 |
2003年 | 156058篇 |
2002年 | 144790篇 |
2001年 | 215323篇 |
2000年 | 213038篇 |
1999年 | 189661篇 |
1998年 | 77976篇 |
1997年 | 71783篇 |
1996年 | 69923篇 |
1995年 | 65228篇 |
1994年 | 59168篇 |
1993年 | 54727篇 |
1992年 | 140278篇 |
1991年 | 135433篇 |
1990年 | 131062篇 |
1989年 | 127653篇 |
1988年 | 117701篇 |
1987年 | 115375篇 |
1986年 | 108969篇 |
1985年 | 106002篇 |
1984年 | 84585篇 |
1983年 | 74360篇 |
1982年 | 53760篇 |
1981年 | 49699篇 |
1980年 | 46560篇 |
1979年 | 75197篇 |
1978年 | 58020篇 |
1977年 | 50575篇 |
1976年 | 47260篇 |
1975年 | 48902篇 |
1974年 | 55312篇 |
1973年 | 52940篇 |
1972年 | 49750篇 |
1971年 | 46495篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
目的:观察离体心脏左心室三层心肌的单相动作电位的改变,以探讨扩张型心肌病易发心室颤动与三层心肌跨室壁复极不均一性的关系。方法:用阿霉素制作扩张型心肌病家兔模型,测定其室颤阈值(VFT)以及心外膜、中层心肌和心内膜心肌细胞的单相动作电位复极90%时程(APD90)、跨室壁复极离散度(TDR)。结果:扩张型心肌病VFT明显降低(P<0.001),三层心肌细胞APD90均明显延长(P<0.001),中层心肌细胞较心外膜、心内膜下心肌细胞延长更为显著(P<0.05);扩张型心肌病跨室壁复极离散度增加(P<0.01)。结论:中层心肌细胞APD90明显延长、跨室壁复极离散度增加、三层心肌复极不均一性增加可能是扩张型心肌病容易发生心室颤动的重要原因。 相似文献
992.
993.
Iron Fortification of Flours in Venezuela 总被引:1,自引:0,他引:1
This paper reviews a conference about the impact of the iron fortification program in Venezuela; it was presented at the Pan American Health Organization regional technical meeting: "Iron Fortification: Where Are We in Terms of Iron Compounds," held in Washington January 10–12, 2001. Some of the data presented were published in the American Journal of Clinical Nutrition , including stimulating results about the impact of fortification of precooked corn and white wheat flours, as well as the prevalence of anemia and iron deficiency in the Venezuelan population. This article reports results from three surveys carried out in 1997, 1998, and 1999 on the same age and socioeconomic group that had been evaluated in 1990, 1992, and 1994. This article also shows the impact of iron fortification programs and the influence of other factors on the prevalence of iron deficiency and anemia during the last 7 years. 相似文献
994.
F Boomsma F A van der Hoorn A J Man in 't Veld M A Schalekamp 《Clinica chimica acta; international journal of clinical chemistry》1988,178(1):59-69
We report a reliable method for determining DOPA levels in plasma and cerebrospinal fluid. The method is based on complete conversion of DOPA to dopamine and quantification by HPLC-ECD of the dopamine formed. Lower limit of detection was 0.5 nmol/l. No differences in plasma DOPA levels were found between normal children (0-15 yr, n = 60), normal adults (n = 39) and patients with essential hypertension (n = 40) or Parkinson's disease (no DOPA therapy, n = 30). In normal individuals and in patients with essential hypertension venous plasma levels were higher than arterial levels (10.2 vs 9.3 nmol/l, p less than 0.001, V/A ratio 1.11 (SD 0.08), n = 15). Sympathetic stimuli (standing, tilting, bicycle exercise, tyramine) did not influence DOPA levels. In untreated depressed patients (n = 10) and in non-parkinsonian neurological patients (n = 12) cerebrospinal fluid levels of DOPA were 4.5 (SD 2.4) and 5.2 (SD 1.3) nmol/l respectively. A direct method for the measurement of DOPA by HPLC-ECD after deproteinization of plasma is also described and compared with the conversion method. Good agreement was found when plasma DOPA levels exceeded 0.25 mumol/l (y(conversion method) = 0.943x (direct method) + 0.118; n = 60; r = 0.985). The direct method, because of greater simplicity and the possibility of simultaneous measurement of the DOPA metabolite 3-O-methyldopa, is the method of choice with plasma samples from DOPA-treated patients. In non-DOPA treated individuals the conversion method is superior and has proved to be an accurate and sensitive method for the determination of DOPA levels in plasma and cerebrospinal fluid. 相似文献
995.
996.
997.
W. S. L. Stebbings M. J. G. Farthing J. R. Puddefoot Elizabeth Anderson G. P. Vinson J. M. A. Northover R. F. M. Wood 《Journal of cancer research and clinical oncology》1988,114(2):208-211
Summary To evaluate the potential effect of androgens on the development and growth of human colorectal adenomas, the prevalence and concentration of cytosolic androgen receptors (AR) were analysed in 26 adenomas and 19 samples of normal colonic mucosa by a hybrid ligand receptor-binding assay. AR were detected in 7 of the adenomas (26.9%), and in 6 of the normal mucosa samples (31.6%). In the adenomas, AR levels demonstrated were low, ranging from 6 to 31 fmol/mg cytosol protein, and dissociation constants (Kds) ranged from 0.17–2.7x10-9
M. Of 13 adenomas excised from men, 6 (46%) had positive receptor activity, whereas only 1 of 13 (7.7%) from women was positive (P=0.03, Fisher's exact test). There was no correlation between AR titre and patient age, or between adenoma size and histological type or degree of dysplasia. In normal mucosa, AR levels ranged from 7 to 33 fmol/mg and Kds ranges from 0.24–3.1x10-9
M. There was no significant difference between either AR prevalence or levels in the adenomas and normal mucosa. The sex difference was exclusive to the adenoma. Endogenous androgen may play a role in adenoma development early in the promotional process. 相似文献
998.
999.
Cytokines play a part in the control of cellular growth, differentiation and development. Given such pleiotropic activities, it is not unexpected that the expression of the cytokines is tightly regulated. When cytokine-mediated processes are altered by mutation and/or overexpression of some cytokine or cytokine receptor genes, oncogenic transformation can occur. Oncogenes which derive their transforming potential through this mechanism include sis, which represents the activated form of the platelet-derived growth factor B chain, hst1/K-fgflint-2, which share appreciable homology with the gene family of fibroblast growth factors, fms, which is related to the cell surface receptor for macrophage-colony stimulating factor, and erbB-1, which encodes a truncated form of the epidermal growth factor receptor. Cytokine treatment has resulted in modulation of aberrant oncogene activity in some model systems. 相似文献
1000.
百年乐与人参黄芪合剂对心血管系统的药理作用比较 总被引:1,自引:1,他引:0
百年乐和人参黄芪合剂对心血管系统的作用研究表明:百年乐能加速小鼠肠系膜微循环障碍的恢复,增加离体兔耳血管的流量,使主动脉平滑肌松弛,对抗心肌缺氧,抑制血栓形成,其作用强于人参黄芪合剂。 相似文献