全文获取类型
收费全文 | 1708522篇 |
免费 | 140206篇 |
国内免费 | 19350篇 |
专业分类
耳鼻咽喉 | 21455篇 |
儿科学 | 51109篇 |
妇产科学 | 47277篇 |
基础医学 | 240004篇 |
口腔科学 | 44043篇 |
临床医学 | 162870篇 |
内科学 | 330708篇 |
皮肤病学 | 37307篇 |
神经病学 | 134421篇 |
特种医学 | 64799篇 |
外国民族医学 | 605篇 |
外科学 | 243829篇 |
综合类 | 71173篇 |
现状与发展 | 58篇 |
一般理论 | 538篇 |
预防医学 | 129417篇 |
眼科学 | 40076篇 |
药学 | 128382篇 |
193篇 | |
中国医学 | 16167篇 |
肿瘤学 | 103647篇 |
出版年
2021年 | 22756篇 |
2020年 | 15598篇 |
2019年 | 19703篇 |
2018年 | 25401篇 |
2017年 | 20273篇 |
2016年 | 21422篇 |
2015年 | 26899篇 |
2014年 | 35970篇 |
2013年 | 45480篇 |
2012年 | 63338篇 |
2011年 | 68085篇 |
2010年 | 40006篇 |
2009年 | 36457篇 |
2008年 | 57401篇 |
2007年 | 60150篇 |
2006年 | 60814篇 |
2005年 | 59146篇 |
2004年 | 52700篇 |
2003年 | 50142篇 |
2002年 | 47462篇 |
2001年 | 81887篇 |
2000年 | 84055篇 |
1999年 | 70800篇 |
1998年 | 21735篇 |
1997年 | 19833篇 |
1996年 | 18999篇 |
1995年 | 17954篇 |
1994年 | 16077篇 |
1993年 | 14503篇 |
1992年 | 50338篇 |
1991年 | 47898篇 |
1990年 | 45471篇 |
1989年 | 43370篇 |
1988年 | 39807篇 |
1987年 | 38691篇 |
1986年 | 35974篇 |
1985年 | 34205篇 |
1984年 | 25818篇 |
1983年 | 21750篇 |
1982年 | 13129篇 |
1979年 | 22505篇 |
1978年 | 15681篇 |
1977年 | 13014篇 |
1976年 | 12230篇 |
1975年 | 12764篇 |
1974年 | 15298篇 |
1973年 | 14873篇 |
1972年 | 13945篇 |
1971年 | 12669篇 |
1970年 | 11989篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
991.
Measurements of the fetal eyeball and its pattern of growth 总被引:1,自引:0,他引:1
992.
993.
P A Fantoni C Baroni G Lazzarini M Astuni S Tognoli V Barbieri 《Minerva chirurgica》1986,41(10):923-930
994.
995.
D Bougle D Pepin M Delhaye J Chambaz C Ricour 《JPEN. Journal of parenteral and enteral nutrition》1986,10(2):216-219
In order to prevent essential fatty acid (EFA) deficiency induced by fat-free total parenteral nutrition (TPN), 10 infants on TPN were rubbed three times daily for 20 days using oenethera oil (80% EFA). Total EFA amount provided cutaneously was 1900 mg/kg/d. Plasma and red blood cells phospholipids were determined on days 1 and 20 in these 10 treated and six untreated infants on TPN and compared with those of normal control infants. On day 1, plasma nonessential FA including 20:3 n-9(p less than 0.01) were increased in both TPN groups while 18:2 n-6 and 18:3 n-3 (p less than 0.001 and p less than 0.01) were decreased. On the 20th day, EFA deficiency had worsened with a decrease in plasma level of 20:4 n-6 (p less than 0.02) and a higher than normal triene/tetraene ratio : 3.4 +/- 1.1 and 2.3 +/- 0.6 vs 0.1 +/- 0.1 (p less than 0.02). As for red blood cells phospholipids, 16:0 was increased and 18:2 n-6 and 20:3 n-6 were decreased (p less than 0.05) on day 1. On day 20, these FA were more abnormal while 20:3 n-9 became significantly increased (p less than 0.05). No difference was observed between the TPN groups at any time. These results show that cutaneous application of large amounts of EFA-rich oil is unable to prevent or cure TPN induced EFA deficiency. 相似文献
996.
C W Tabor H Tabor Q W Xie 《Proceedings of the National Academy of Sciences of the United States of America》1986,83(16):6040-6044
We have obtained Escherichia coli mutants lacking spermidine synthase (putrescine aminopropyltransferase) and have found that the mutated gene (speE) is located immediately upstream from the gene coding for S-adenosylmethionine decarboxylase (speD); these genes are located at 2.7 minutes on the E. coli chromosome. Both genes are present in a 1795-base-pair fragment of E. coli DNA that was cloned into pBR322. Deletion of 105 bases upstream of speE caused a coordinate loss of both activities, indicating that speE and speD constitute a single operon. speE and speD have also been cloned separately in a high-expression vector; strains carrying these plasmids overproduce the respective enzymes. 相似文献
997.
998.
The simultaneous determination of cerebrospinal fluid and plasma adenosine deaminase activity as a diagnostic aid in tuberculous meningitis 总被引:1,自引:0,他引:1
P R Donald C Malan A van der Walt J F Schoeman 《Suid-Afrikaanse tydskrif vir geneeskunde》1986,69(8):505-507
The simultaneous determination of cerebrospinal fluid (CSF) and plasma adenosine deaminase (ADA) activity was evaluated as a diagnostic aid in tuberculous meningitis (TBM). CSF and plasma ADA activity were determined in four groups of patients: (i) a 'no meningitis' group of 174 children investigated for possible meningitis, but found to be uninfected; (ii) an aseptic meningitis group of 40 children; (iii) a bacterial meningitis group of 31 children; and (iv) a TBM group of 27 patients (24 children and 3 adults). CSF ADA alone was determined in a further 23 children with aseptic meningitis, 19 with bacterial meningitis and 13 children and 7 adults with TBM. Both the CSF/plasma ADA ratio and the absolute CSF ADA activity were raised in TBM (mean values 0,24 and 12,61 U/I respectively) and bacterial meningitis (mean values 0,59 and 15,43 U/I respectively), but not in the aseptic meningitis group (mean values 0,06 and 2,00 U/I) or the 'no meningitis' group (mean values 0,04 and 1,51 U/I). Both values will distinguish TBM from aseptic meningitis, but do not appear to hold any marked advantages over conventional CSF criteria in the diagnosis of TBM. 相似文献
999.
中药延胡索的炮制研究 总被引:6,自引:0,他引:6
本文采用容量法及电位测定法分别测定了延胡索生品及醋炒、醋蒸、醋煮、酒炒和盐炒5种延胡索炮制品中的总生物碱含量,另采用薄层扫描法及紫外分光光度法测定上述6种样品中的延胡索乙素含量,并对各种样品进行了小白鼠止痛试验。实验结果表明,延胡索用醋炮制或用酒炮制均能提高其水煎液中总生物碱和延胡索乙素的煎出量,并能增强其止痛作用,其中醋制法较为显著。实验结果与临床上多用醋制延胡索入药的经验相符合。 相似文献
1000.
本文报道用高效液相色谱-电化学检测器方法,研究了罂粟碱对大鼠脑内及心脏单胺神经递质代谢的影响。结果表明:罂粟碱能显著增加大鼠纹状体及边缘区多巴胺代谢物二羟苯乙酸(DOPAC)和高香草酸(HVA),升高约50-70%。5-羟色胺代谢物5-羟吲哚醋酸(5HIAA)增加约30%,而对脑及心脏内的单胺递质本身含量未见有明显影响。 相似文献