全文获取类型
收费全文 | 136961篇 |
免费 | 5812篇 |
国内免费 | 346篇 |
专业分类
耳鼻咽喉 | 2119篇 |
儿科学 | 4187篇 |
妇产科学 | 2876篇 |
基础医学 | 18280篇 |
口腔科学 | 4901篇 |
临床医学 | 8471篇 |
内科学 | 33934篇 |
皮肤病学 | 4217篇 |
神经病学 | 10814篇 |
特种医学 | 3142篇 |
外国民族医学 | 1篇 |
外科学 | 17378篇 |
综合类 | 725篇 |
一般理论 | 40篇 |
预防医学 | 13017篇 |
眼科学 | 3069篇 |
药学 | 9214篇 |
中国医学 | 654篇 |
肿瘤学 | 6080篇 |
出版年
2023年 | 892篇 |
2022年 | 736篇 |
2021年 | 2956篇 |
2020年 | 1501篇 |
2019年 | 3159篇 |
2018年 | 5266篇 |
2017年 | 3113篇 |
2016年 | 2908篇 |
2015年 | 3258篇 |
2014年 | 3802篇 |
2013年 | 5671篇 |
2012年 | 9943篇 |
2011年 | 10589篇 |
2010年 | 5348篇 |
2009年 | 3830篇 |
2008年 | 8461篇 |
2007年 | 8969篇 |
2006年 | 8316篇 |
2005年 | 8205篇 |
2004年 | 7269篇 |
2003年 | 6778篇 |
2002年 | 6369篇 |
2001年 | 3893篇 |
2000年 | 4524篇 |
1999年 | 3366篇 |
1998年 | 607篇 |
1997年 | 379篇 |
1996年 | 373篇 |
1995年 | 298篇 |
1994年 | 227篇 |
1992年 | 1288篇 |
1991年 | 1076篇 |
1990年 | 945篇 |
1989年 | 775篇 |
1988年 | 647篇 |
1987年 | 640篇 |
1986年 | 643篇 |
1985年 | 542篇 |
1984年 | 399篇 |
1983年 | 306篇 |
1979年 | 343篇 |
1975年 | 278篇 |
1974年 | 326篇 |
1973年 | 349篇 |
1972年 | 294篇 |
1971年 | 314篇 |
1970年 | 293篇 |
1969年 | 297篇 |
1968年 | 267篇 |
1967年 | 235篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
M. A. García-Pérez C. Climent P. Briones M. A. Vilaseca M. Rodés V. Rubio 《Journal of inherited metabolic disease》1997,20(6):769-777
Mutations P225L and P225R were identified in codon 225 of the gene for ornithine transcarbamylase (OTC) in two patients with the neonatal form of OTC deficiency. The mutations occur at a CpG dinucleotide and eliminate a unique MspI restriction site in exon 7 of the OTC gene. They do not alter existing splice sites or create new sites, as judged from the nucleotide sequence. Both mutations are associated with undetectable levels of OTC antigen in liver homogenates, and with either complete lack of OTC activity (P225R mutation) or very small residual activity (0.15% of normal in the P225L mutation). The residual activity observed with P225L exhibits normal pH dependence, little or no increases in the Km values for ornithine and carbamoyl phosphate and normal stability at either 37°C or, in the presence of 0.66 mol/L urea, at 0°C. The latter conditions were used to examine whether the P225L mutation favours dissociation of the active OTC trimer. Given the normal stability and lack of tendency to dissociation of the mutant enzyme, it appears likely that the dramatic reduction in the level of OTC protein is due to inefficient conversion of the mutant OTC precursor polypeptide (pOTC) into the correctly localized, appropriately folded, mature enzyme trimer, suggesting degradation of pOTC in transit to the mitochondria. 相似文献
22.
The present authors investigated the excretion, distribution and pharmacokinetics of the novel potential antirheumatic agent flobufen and its active metabolite after p.o. and i.v. doses of 2, 10 and 50 mg/kg administered to rats. The drug is resorbed well from the digestive tract and mostly it is metabolized to the principal metabolite M, which is only slowly excreted from the organism mainly by renal clearance. Within the whole dose range the kinetics of the drug is linear. Binding of flobufen and M to proteins is high (95-99%). The highest concentrations of radioactive metabolites (mostly M) were found in the plasma, liver, lungs, kidneys, connective tissue and inflammatory foci. The penetration of metabolites through the placenta and excretion in human milk are relatively important. 相似文献
23.
24.
25.
Melatonin, a pineal hormone, released photoperiodically, was administered systemically in rats, previously implanted with semimicroelectrodes into six different brain structures. The multiunit electrical activity of these structures was recorded for 10 min before and 60 min after melatonin administration in unanesthetized, freely moving rats. Different melatonin doses (100, 200, 500, and 1000 micrograms/kg) produced changes in the electrical activity of all tested structures. However, amygdala, rostral hypothalamus and mesencephalic reticular formation showed the most important changes. The main effect induced by melatonin was a dose-related decrease of the spontaneous electrical activity. The significance of these effects is discussed within the context of the behavioral and endocrinological effects of melatonin. 相似文献
26.
The study concerned the effects of acute and chronic clomipramine administration to male rats on exploratory activity in a novel environment (hole-board) and on immobility in the forced swimming test. Acute clomipramine administration did not alter either exploratory activity on a hole-board as measured 3 or 20 h after drug administration, or immobility in the forced swimming test as measured 20 h after drug administration. Approximately 20 h after the last injection of clomipramine, the rats chronically treated with the drug showed reduced exploratory activity on the hole-board. In contrast, chronic clomipramine treatment significantly increased the activity in the forced swimming test. The effects of the drug on exploratory and forced swimming activities persisted for 14 days after the cessation of clomipramine administration. These data indicate that chronic clomipramine administration exerted profound and long-lasting effects on central nervous system function. The long-lasting action of the drug on behaviour in the forced swimming test might explain the long-term beneficial effect of antidepressant drugs in counteracting behavioral depression. 相似文献
27.
28.
D Mezzano G E del Pino M Montesinos M E García E Aranda A Foradori 《Thrombosis and haemostasis》1991,66(2):254-258
Thrombocytopenia was induced in mongrel dogs by two mechanisms: immunologically, by intravenous injection of heterologous antiplatelet antibody, and non-immunologically, by circulating the blood through glass beads in anesthetized animals. The platelet content of 5-HT was monitored before and during the recovery of the blood platelet counts. This period is associated with the normalization of the mean platelet survival time and with a progressive increase in the mean age of the circulating platelet population. A continuous increment in platelet 5-HT closely followed the increase in platelet counts in both models of thrombocytopenia, and a strong correlation was found between the platelet age and 5-HT content. These findings support the concept that platelets accumulate 5-HT during their physiological aging process, contradicting the notion that a negative balance in 5-HT content results at the end of their physiological lifespan in circulation. These results are not in conflict with the concept that circulating platelets release and re-uptake 5-HT. 相似文献
29.
30.
Naiquan Zheng Rafael F Escamilla Glenn S Fleisig Kevin E Wilk James R Andrews 《中华骨科杂志》2002,29(1):697-700
结果 髌股关节的压力与应力随膝关节屈曲角度的增加而升高,随膝关节屈曲角度的减小而降低(图3~8).不同膝关节屈曲角度下弓步变化和跨步变化的髌股关节压力见表1. 相似文献