全文获取类型
收费全文 | 172961篇 |
免费 | 16641篇 |
国内免费 | 11508篇 |
专业分类
耳鼻咽喉 | 1819篇 |
儿科学 | 2414篇 |
妇产科学 | 1411篇 |
基础医学 | 15612篇 |
口腔科学 | 3054篇 |
临床医学 | 21068篇 |
内科学 | 21075篇 |
皮肤病学 | 2015篇 |
神经病学 | 6707篇 |
特种医学 | 6551篇 |
外国民族医学 | 68篇 |
外科学 | 17723篇 |
综合类 | 37837篇 |
现状与发展 | 50篇 |
一般理论 | 10篇 |
预防医学 | 15047篇 |
眼科学 | 3755篇 |
药学 | 18447篇 |
207篇 | |
中国医学 | 13551篇 |
肿瘤学 | 12689篇 |
出版年
2024年 | 691篇 |
2023年 | 2441篇 |
2022年 | 6248篇 |
2021年 | 8118篇 |
2020年 | 6574篇 |
2019年 | 4881篇 |
2018年 | 5310篇 |
2017年 | 5454篇 |
2016年 | 5119篇 |
2015年 | 8165篇 |
2014年 | 9924篇 |
2013年 | 10424篇 |
2012年 | 15109篇 |
2011年 | 16121篇 |
2010年 | 12308篇 |
2009年 | 10358篇 |
2008年 | 11479篇 |
2007年 | 11012篇 |
2006年 | 10213篇 |
2005年 | 8650篇 |
2004年 | 6146篇 |
2003年 | 5737篇 |
2002年 | 4717篇 |
2001年 | 3598篇 |
2000年 | 2781篇 |
1999年 | 2077篇 |
1998年 | 1192篇 |
1997年 | 1121篇 |
1996年 | 899篇 |
1995年 | 806篇 |
1994年 | 617篇 |
1993年 | 387篇 |
1992年 | 408篇 |
1991年 | 335篇 |
1990年 | 300篇 |
1989年 | 233篇 |
1988年 | 201篇 |
1987年 | 198篇 |
1986年 | 147篇 |
1985年 | 117篇 |
1984年 | 65篇 |
1983年 | 47篇 |
1982年 | 41篇 |
1981年 | 41篇 |
1980年 | 22篇 |
1979年 | 43篇 |
1977年 | 20篇 |
1976年 | 22篇 |
1974年 | 22篇 |
1973年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
71.
本文将对呼吸机以下两种常见故障进行简要分析:①呼吸机在抢救病人过程中出现自动切断电源②呼吸机气道口湿度报警。 相似文献
72.
Elizabeth R Seaquist Wei Chen Luke E Benedict Kamil Ugurbil Jae-Hwan Kwag Xiao-Hong Zhu Charles A Nelson 《Journal of cerebral blood flow and metabolism》2007,27(1):154-160
Functional magnetic resonance imaging (fMRI) based on blood oxygen level-dependent (BOLD) contrast has become an invaluable tool in the assessment of in vivo neuronal activation. Quantification of the BOLD response is determined by the hemodynamic and metabolic changes that occur in response to brain stimulation. However, these changes may vary by changes in insulin, a hormone known to be vasoactive in some tissues. To determine if insulin has an effect on fMRI, we measured the BOLD response to a visual stimulus in five normal volunteers in which insulin was first suppressed and then brought to a high physiological concentration. In addition, we also examined the effect of insulin on activation of the visual cortex as measured by the visual-evoked potential (VEP). We found that the BOLD response measured in the presence of insulin (serum insulin=236+/-29 pmol/L) was significantly lower (P<0.001) than that measured in its absence (serum insulin=8+/-2 pmol/L). Insulin was without effect on P100 amplitude or latency acquired in the presence or absence of insulin in 28 subjects using the same stimulus as that used for the fMRI experiments. Our observations suggest that insulin may have effects on cerebral blood flow and/or metabolism that affect the BOLD signal that are independent of its effects on neuronal activation identified by event related potentials (ERP). These findings highlight the complexity that must be considered when interpreting differences in fMRI responses between groups of subjects that differ in insulin concentration and/or insulin sensitivity. 相似文献
73.
目的 评价1.5T和3.0T两种不同的磁场强度对膝关节影像质量的影响.方法 采用同一厂家、同一系列、不同磁场强度的两种成像设备,对16位健康自愿者在1.5T和3.0T两种不同的磁场强度下,分别进行膝关节成像,序列使用相同的参数,不校正磁场强度的变化对TR的影响.分别测量半月板、肌肉、脂肪和骨骼的信噪比、对比噪声比和相对对比度,进行定量分析.结果 3.0T条件下膝关节图像的信噪比和对比噪声比明显优于1.5T,差异有统计学意义;3.0T条件下膝关节图像的相对对比度与1.5T比较,没有明显的统计学差异.结论 膝关节图像的信噪比和对比噪声比均随着场强的增加而提高,膝关节图像的相对对比度随场强的变化并不敏感. 相似文献
74.
75.
Injection of TFP (a specific antagonist of CaM) into the lateral ventricles of the rat brain on the fourth day of pregnancy causes marked antifertility effect in 83% of the rats (0% in the control group). Examination with the pontamone blue reaction for the implantation elucidated that the antifertitity effect was due to the blockage of implantation of the follicle. Injection of TFP into the lateral ventricles of the brain markedly reduced the concentration of CaM in hypothalamus, ovary and uterus. Serum progesterone was also reduced. However, injection glven on day 7 was ineffective to terminate the pregnancy. Injection given on certain time of pregnancy was able to reduce the cellular CaM content and to cause antifertitity. This finding demonstrated that CaM played an important rote during the course of pregnancy. 相似文献
76.
77.
锌离子对大鼠海马突触体Ca^2+—Mg^2+ATP酶活性及蛋白合成的影响 总被引:5,自引:0,他引:5
行为实验己经证明,锌过多或缺锌均可影响脑功能。锌作为体内重要的微量元素,影响多种酶的活性及蛋白质和核酸的台成。本实验通过体外分离大鼠脑海马突触体,观察不同浓度锌离子对Ca2 -Mg2 ATP酶的活性和3H-Leu掺入突触蛋白合成的影响.结果表明:1.锌离子浓度在25μmol/L时增加该酶的活性(<0.01),并促进3H-Leur掺入蛋白质的合成(<0.05)。2.锌离子在50,100,200μmol/L的较高浓度时对Co2 -M2 ATP酶的活性有显著的抑制作用(分别为:P<0.05.P<0.01,P<0.01),仅200μmol/L对3H—Leu掺入突触蛋白合成有抑制作用。本研究提示:适量的锌对突触体功能的维持是必要的,但剂量过高则起相反作用。 相似文献
78.
In various animal models of injury to skin, mucous membranes, muscle and brain, corticotropin-releasing factor (CRF) attenuated vascular leakage in the injured tissues. Here, the effects of CRF on a rat model of pulmonary oedema were examined. Male albino rats (220-290 g) received saline or CRF s.c., 30 min before pentobarbital anaesthesia, 60 mg/kg i.p., and 1 h before 1-epinephrine bitartrate (Epi), 30 micrograms/kg i.v. Within 30 min after Epi all (n = 27) saline-pretreated rats were dead from pulmonary oedema, but animals receiving human/rat CRF at doses of 7 to 57 micrograms/kg s.c. (n = 25) were all alive. Body wt, wet and dry wt of lungs were used to calculate an oedema index. This index increased from 3.6 +/- 0.1 to 9.6 +/- 0.3 after Epi but was inhibited by 87% after CRF 28 micrograms/kg s.c. The ED50 of CRF for reducing pulmonary oedema was 3.2 (1.3-7.4) micrograms/kg s.c. Mean arterial pressure increased from 119 +/- 4 to 167 +/- 2 mmHg after Epi 10 micrograms/kg i.v., but was not different (118 +/- 3 to 169 +/- 4 mmHg) after CRF pretreatment, 6 micrograms/kg s.c., a dose which reduced lung oedema. Pharmacokinetic estimates suggest that plasma levels of CRF sufficient to attenuate lung oedema in rats approximate those seen in pregnant women at delivery, raising the possibility that endogenous CRF may protect the maternal organism during parturition. 相似文献
79.
用9周-39周引产胎儿标本72例,取右耳廓石蜡切片,HE和Weitert弹性纤维染色,光镜观察其弹性软骨、弹性纤维、耳廓肌和结缔组织的发生。 相似文献
80.
"工欲善其事,必先利其器",具备抢救急重危患儿的能力,是每个儿科护士在护理危重患儿中的利器之一.因此,本文针对护理人员在急诊抢救护理过程中的问题进行分析,提出解决问题的相应对策,以提升护理专业素质. 相似文献