全文获取类型
收费全文 | 5119篇 |
免费 | 554篇 |
国内免费 | 75篇 |
专业分类
耳鼻咽喉 | 69篇 |
儿科学 | 35篇 |
妇产科学 | 8篇 |
基础医学 | 420篇 |
口腔科学 | 27篇 |
临床医学 | 188篇 |
内科学 | 144篇 |
皮肤病学 | 45篇 |
神经病学 | 368篇 |
特种医学 | 77篇 |
外科学 | 84篇 |
综合类 | 321篇 |
一般理论 | 1篇 |
预防医学 | 111篇 |
眼科学 | 3308篇 |
药学 | 384篇 |
中国医学 | 93篇 |
肿瘤学 | 65篇 |
出版年
2024年 | 31篇 |
2023年 | 93篇 |
2022年 | 161篇 |
2021年 | 211篇 |
2020年 | 207篇 |
2019年 | 180篇 |
2018年 | 206篇 |
2017年 | 208篇 |
2016年 | 214篇 |
2015年 | 203篇 |
2014年 | 238篇 |
2013年 | 522篇 |
2012年 | 217篇 |
2011年 | 289篇 |
2010年 | 232篇 |
2009年 | 239篇 |
2008年 | 224篇 |
2007年 | 217篇 |
2006年 | 195篇 |
2005年 | 162篇 |
2004年 | 159篇 |
2003年 | 130篇 |
2002年 | 107篇 |
2001年 | 106篇 |
2000年 | 73篇 |
1999年 | 64篇 |
1998年 | 76篇 |
1997年 | 64篇 |
1996年 | 43篇 |
1995年 | 51篇 |
1994年 | 34篇 |
1993年 | 36篇 |
1992年 | 26篇 |
1991年 | 30篇 |
1990年 | 33篇 |
1989年 | 29篇 |
1988年 | 31篇 |
1987年 | 24篇 |
1986年 | 28篇 |
1985年 | 61篇 |
1984年 | 60篇 |
1983年 | 43篇 |
1982年 | 47篇 |
1981年 | 38篇 |
1980年 | 46篇 |
1979年 | 17篇 |
1978年 | 20篇 |
1977年 | 5篇 |
1976年 | 11篇 |
1969年 | 2篇 |
排序方式: 共有5748条查询结果,搜索用时 781 毫秒
61.
The magnetic flux normal to the scalp surface was measured with a whole-head neuromagnetometer while right-handed subjects (N = 15) were engaged in either an auditory word- or a tone-recognition task. Sources of the recorded magnetic fields were modeled as equivalent current dipoles at 4 ms intervals and the number of sources in the later portion of the magnetic response was used as an index of the degree of brain activation. Significantly more sources were found in the left as compared to the right hemisphere in the word but not the tone task on a group basis. On an individual basis, 13/15 subjects had more sources in the left as compared to the right hemisphere during the word task, while in the tone task 3/10 subjects showed this pattern. Sources of activity were found in the left superior and middle temporal gyri in all subjects with available MRI scans. Sources were also found in the supramarginal gyrus and in medial temporal areas, including the hippocampus, in the majority of cases. MEG appears to be a promising tool for detecting activity in cerebral areas specialized for language and memory function. 相似文献
62.
Troisi E Silvestrini M Matteis M Monaldo BC Vernieri F Caltagirone C 《Journal of neurology》1999,246(12):1172-1176
This study assessed the use of transcranial Doppler ultrasound in detecting selective changes in cerebral blood flow velocity
during emotional processes. The role of the respective hemispheres in emotional processing is controversial. Cerebral control
of emotional processing has previously been investigated by analysis of patients with unilateral brain damage, experiments
with selective stimulation of only one hemisphere, and more recently by imaging techniques measuring local cerebral blood
flow. We investigated mean flow velocity continuously and simultaneously in both the right and left middle cerebral arteries
(MCAs) in 16 healthy right-handed young subjects at rest and during the performance of three tasks: task 1: 15 slides with
nonemotional content; task 2: 15 slides with negative emotional content; task 3: 15 slides with nonemotional content with
different content from that in task 1. The three tasks produced significantly different effects on the right and left hemispheres.
During the two nonemotional tasks the increase in mean flow velocity over basal values was similar in the two MCAs (task 1:
left MCA = 3.27 ± 1.9%; right MCA = 3.63 ± 2.1%; task 3: left MCA = 2.42 ± 0.7%; right MCA = 2.56 ± 1.3%); the negative emotional
task was accompanied by a significantly higher increase in the right (11.31 ± 1.6%) than in the left MCA (4.72 ± 3.7%; analysis
of variance two-way interaction: side of recording x task, F = 43.6, P < 0.001). These results show the possibility of obtaining specific functional information from bilateral transcranial Doppler
ultrasound and suggest the involvement of the right hemisphere in emotional processing.
Received: 4 March 1999 Received in revised form: 29 June 1999 Accepted: 5 August 1999 相似文献
63.
Purpose: To investigate the compliance of the patients with ocular fundus diseases with recommendation for follow-up examination after laser treatment, and the underlying reasons for non-compliance.Methods: 53 patients with ocular fundus disease were asked to fill in a questionnaire which includes the socio-demographic characteristics, fear of the fundus disease, conception of the laser treatment and the motivation for staying healthy. Variables were compared for the compliers group and the non-compliers group by chi-square test. Result; Of the 53 subjects, 35 were classified as non-compliers and 18 were classified as compliers. There was no statistically significant difference between the two groups on all selected socio-demographic factors, conception of the laser treatment and the motivation for staying healthy. Significant difference was found between the two groups on two of those items concerning the fear of the diseases (P<0. 05). About half of the participants showed the lack of knowledge about 相似文献
64.
The acute and subchronic effects of hashish extract (20 mg 9-THC/kg) on the social interactions between two drug-treated residents and an untreated intruder male were investigated. In this analysis 28 different behavioral elements were recorded.A single drug application suppressed all categories of behavior, except submissive behavior and flight, in dominant and subordinate residents. Treated animals were less active than controls and immobility was very frequent. An elevated total activity, due to an increase in non-social activities, was observed in the untreated intruder males of this group. Social investigation as well as submissive behavior and flight were reduced in these animals.On introduction of an untreated male after the fourth drug treatment of the residents, the drugged males showed tolerance to the sedative and most of the other behavioral effects of the drug, and intruder males behaved quite normally.The formation of a dominant-subordinate relation within the group was influenced neither by a single nor by repeated drug treatment.The acute and subchronic effects of hashish extract on social, especially aggressive behavior of males are compared to those described in previous papers and the variation in the results of the different studies is discussed. 相似文献
65.
66.
Elevated ocular levels of vascular endothelial growth factor in patients with von Hippel-Lindau disease 总被引:1,自引:0,他引:1
M. Los C.J.M. Aarsman L. Terpstra D. Wittebol-Post C.J.M. Lips G.H. Blijham E.E. Voest 《Annals of oncology》1997,8(10):1015-1022
Background: Von Hippel–Lindau disease (VHL) is a rare autosomal dominant inherited disorder characterized by highly vascularized tumors in various organs. The abundant presence of endothelial cells in VHL tumors strongly suggest a role of the VHL tumor suppressor gene in the regulation of angiogenesis. Recently, in vitro studies have shown that the VHL tumor suppressor gene regulates the expression of vascular endothelial growth factor (VEGF). We investigated whether VHL patiens have increased levels of VEGF in their body fluids.Patients and methods: The concentration of VEGF was measured in fluid of the anterior chamber of the eye, serum, urine, and fluid from renal cysts of VHL patients and unaffected individuals by ELISA. In addition, levels of basic fibroblast growth factor (bFGF), interleukin-8 (IL-8) and endothelin-1 (ET-1) were measured in urine and serum of VHL patients and control subjects.Results: In 80% of the VHL patients VEGF was detectable in aqueous fluid of the anterior chamber of their eyes. A strong positive correlation (r = 0.90) was found between the age of VHL patients and ocular VEGF concentrations. At comparable age, VEGF levels in ocular fluid of VHL patients were significantly higher (P < 0.001) than in unaffected subjects. No correlation was found between VEGF concentration and the presence of retinal angiomas. A 10 and 16 fold increase of VEGF concentration was seen in fluid from two independent VHL-related cysts as compared with VEGF serum levels of the same patient. The mean concentration of VEGF in serum of VHL patients (n = 15) (319 ± 84 pg/ml) was higher than in matched controls (238 ± 68 pg/ml; P = NS). The mean concentration of VEGF in urine of VHL patients (128 ± 36 pg/ml) was lower than in matched controls (183 ± 25 pg/ml; P = NS). Concentrations of VEGF did not correlate with the presence of VHL-related tumors. No differences were observed between concentrations of bFGF, IL-8 and ET-1 in serum and urine of VHL patients and matched controls.Conclusions: These findings support a role for the VHL tumor suppressor gene in the in vivo regulation of VEGF. 相似文献
67.
目的:探讨针剌对家兔实验性高眼压的影响。方法:应用2%α糜蛋白酶注入家兔眼后房,形成实验性高眼压症。将已形成高眼压的25只家兔眼分为针剌组(10只眼)、西药组(10只眼)和对照组(5只眼)。各组在针剌和药物治疗前后均测量眼压。结果:治疗前针剌组、西药组和对照组的眼压分别为562kPa,629kPa和546kPa,3组之间无显著性差异(P>005)。针剌组针剌后在1~3小时内与对照组相比眼压均有明显降低(P<0001);西物组在药物治疗后1~3小时内与对照组相比眼压也有降低(P<005)。结论:针剌具有降低家兔实验性高眼压的作用。 相似文献
68.
目的观察人体于不同的头位倾斜条件下诱发的OCR反应特征,为建立其检测方法和实际应用提供依据.方法受试对象为地面人员22名和飞行人员11名,端坐于装有特制头托的座椅上,通过头位在冠状面内分别处于左右各倾斜30°、50°、70°的位置诱发静态OCR反应.采用红外视频眼动记录方法分别随机测定从头直位到左右各30°、50°、70°的眼动视频信号.最后以动头前即刻的眼球位置为零位,以眼球虹膜纹理为标志,对各时刻虹膜纹理与初始状态虹膜纹理进行互相关分析,找出相关度最大的一点为各时刻眼球位置,测量该时刻眼球与初始眼球位置的角度即为眼球扭转角度.结果头位倾斜引起的典型OCR反应曲线特征是,头位倾斜动作开始,首先引起一个幅度较大的与头动方向相反的眼球反方向旋转,随之,眼球反转角度逐渐减小,在头位倾斜到固定角度后,眼球反转角度在一定范围内波动或不变,未发现头位向同一方向倾斜不同角度引起的OCR有显著差异.飞行员与正常地面人群OCR反应未见显著差别.结论静态头位倾斜可以诱发出OCR反应,可用来评价耳石器功能. 相似文献
69.
目的:观察唯地息眼凝胶剂对兔芥子气角膜上皮损伤的治疗作用。方法:新西兰白兔8只,用200μL/L液态芥子气致伤双眼角膜5min,左眼为治疗组,用唯地息眼凝胶剂点眼,4次/d,右眼为对照组,用2.5g/L氯霉素眼液滴眼,4次/d,分别于染毒后2,8,16,24,36,48和72h对角膜荧光素着色区拍照,计算其上皮愈合速率和上皮破损率。结果:治疗组和对照组的角膜上皮愈合速率分别为(1.15±0.19)mm2/h和(1.03±0.12)mm2/h,两者有显著差异(P<0.05),角膜上皮破损率分别为44.4%和54.2%,两者差异显著(P<0.05)。结论:唯地息眼凝胶剂能促进芥子气染毒引起的兔眼角膜损伤的上皮愈合,也能减少角膜上皮反复破损。 相似文献
70.
色素上皮细胞衍生因子在眼科中的作用 总被引:3,自引:1,他引:3
色素上皮细胞衍生因子(pigmentepithelium-derivedfactor,PEDF)是由视网膜色素上皮细胞分泌的一种蛋白质,属于丝氨酸蛋白酶抑制基因家族,具有多种生物学活性,PEDF具有营养神经的功效,通过保护神经元免受神经毒性侵害而发挥神经营养因子之作用;PEDF还能抑制血管内皮细胞的移行,具有抗新生血管诱导因子的作用,它能够影响视网膜的分化,发育和成熟,对视网膜的机械损伤.光损伤和缺血性损伤有修复作用,是一种非常有前景的新生血管抑制剂。 相似文献