全文获取类型
收费全文 | 16694篇 |
免费 | 524篇 |
国内免费 | 324篇 |
专业分类
耳鼻咽喉 | 300篇 |
儿科学 | 36篇 |
妇产科学 | 27篇 |
基础医学 | 3675篇 |
口腔科学 | 180篇 |
临床医学 | 514篇 |
内科学 | 425篇 |
皮肤病学 | 12篇 |
神经病学 | 7853篇 |
特种医学 | 300篇 |
外科学 | 1238篇 |
综合类 | 1338篇 |
预防医学 | 123篇 |
眼科学 | 234篇 |
药学 | 1008篇 |
2篇 | |
中国医学 | 149篇 |
肿瘤学 | 128篇 |
出版年
2023年 | 143篇 |
2022年 | 239篇 |
2021年 | 369篇 |
2020年 | 288篇 |
2019年 | 260篇 |
2018年 | 242篇 |
2017年 | 285篇 |
2016年 | 282篇 |
2015年 | 296篇 |
2014年 | 489篇 |
2013年 | 553篇 |
2012年 | 573篇 |
2011年 | 680篇 |
2010年 | 597篇 |
2009年 | 610篇 |
2008年 | 646篇 |
2007年 | 579篇 |
2006年 | 618篇 |
2005年 | 470篇 |
2004年 | 455篇 |
2003年 | 489篇 |
2002年 | 408篇 |
2001年 | 355篇 |
2000年 | 351篇 |
1999年 | 351篇 |
1998年 | 393篇 |
1997年 | 398篇 |
1996年 | 364篇 |
1995年 | 345篇 |
1994年 | 290篇 |
1993年 | 339篇 |
1992年 | 261篇 |
1991年 | 278篇 |
1990年 | 261篇 |
1989年 | 249篇 |
1988年 | 282篇 |
1987年 | 293篇 |
1986年 | 353篇 |
1985年 | 518篇 |
1984年 | 483篇 |
1983年 | 337篇 |
1982年 | 332篇 |
1981年 | 272篇 |
1980年 | 265篇 |
1979年 | 160篇 |
1978年 | 115篇 |
1977年 | 67篇 |
1976年 | 61篇 |
1975年 | 45篇 |
1973年 | 47篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
目的 研究双侧丘脑底核(STN)脑深部电刺激术(DBS)治疗原发性肌张力障碍的长期疗效:方法 比较15例行舣侧STN—DBS治疗的原发性肌张力障碍患者,手术前后的Burke—Fahn—Marsden肌张力障碍评分改善程度及长期改善效果。结果 15例原发性肌张力障碍患者中12例在开启刺激器后症状即刻得到部分缓解,以不自主运动、异常姿势及躯体的扭转改善为主,其中9例在刺激1—3d后、3例刺激1,周后改善75%以上,6个月后平均改善92%;1例在2个月后开始改善,6个月后改善90%以上;2例在1个月开始出现轻微改善,6个月后改善了76%:15例患者的长期随访结果显示其疗效稳定,经过1—3次程控后不需经常调整刺激参数:所有患者未出现手术相关并发症及永久性副作用。结论 双侧丘脑底核脑深部电刺激术对原发性肌张力障碍有显著的治疗效果,且疗效持久、稳定,无并发症及永久性副作用。比较GPi—DBS而言,STN—DBS起效快、最件刺激化点及参数易于确定、刺激参数水平低、长期疗效稳定,可能是原发性肌张力障碍DBS治疗的理想靶点。 相似文献
42.
R P Vertes 《The Journal of comparative neurology》1992,326(4):595-622
The projections of the supramammillary nucleus (SUM) were examined in the rat by the anterograde anatomical tracer Phaseolus vulgaris leucoagglutinin (PHA-L). The majority of labeled fibers from SUM ascended through the forebrain within the medial forebrain bundle. SUM fibers were found to terminate heavily in the hippocampal formation, specifically within the granule cell layer and immediately adjoining molecular layer of the dentate gyrus. In addition, SUM fibers were shown to distribute densely to several structures with strong connections with the hippocampus, namely, the nucleus reunions of the thalamus, the medial and lateral septum, the entorhinal cortex, and the endopiriform nucleus. SUM fibers were also shown to project significantly to several additional subcortical and cortical sites. The subcortical sites were the dorsal raphe nucleus, the midbrain central gray, the fields of Forel/zona incerta, the dorsomedial hypothalamic area, midline/intralaminar nuclei of the thalamus (posterior paraventricular, rhomboid, central medial, intermediodorsal, and mediodorsal), the medial and lateral preoptic areas, the bed nucleus of the stria terminalis, the substantia innominata, the vertical limb of the diagonal band nucleus, and the claustrum. The cortical sites were the occipital, temporal, parietal, and frontal cortices. Some notable differences were observed in projections from the lateral as compared to the medial SUM. For example, fibers originating from the lateral SUM distributed heavily to the hippocampal formation and parts of the cortex, whereas those from the medial SUM projected sparsely to these two regions. The SUM projections to the hippocampal formation and associated structures may serve as the substrate for a SUM involvement in the generation of the theta rhythm of the hippocampus and the gating of information flow through the hippocampal formation. 相似文献
43.
大肠癌旁粘膜细胞的PCNA和AgNORs表达观察 总被引:2,自引:0,他引:2
用增殖细胞核抗原(PCNA)和核仁组成区嗜银蛋白(AgNORs)对35例大肠癌旁粘膜进行细胞增殖表达与观察。结果表明:癌旁粘膜的PCNA标记指数增多,标记增强,排列紊乱。AgNORs在癌旁粘膜中,颗粒增多、增大,形态多样,0 ̄1cm和2 ̄3cm组的标记指数与4 ̄5cm组的标记指数相比较,有显著或非常显著差异(P〈0.05或P〈0.01)。在DukeA、B期中,细胞标记指数增高增强,与癌的发生和患者 相似文献
44.
Recent evidence suggests that a variety of hypothalamic neuropeptides may mediate interneuronal communication to coordinate diverse neuroendocrine and behavioral functions. In this work, we describe the effects of neuropeptide Y (NPY) on feeding and sexual behaviors. We observed that central administration of bolus NPY stimulated a robust, dose-related feeding response in satiated male and female rats. Continuous NPY receptor activation also evoked dose-related, intermittent feeding in a manner normally observed during nocturnal feeding. It appears that the paraventricular nucleus in the hypothalamus may be the primary site of NPY action because the anticipated reciprocal changes in NPY concentrations, in response to food deprivation followed by ad libitum food intake, occurred only in this site. Additional findings revealed that NPY-induced feeding may follow either substantial reduction or complete restraint of an inhibitory influence on feeding mediated by alpha 2-adrenoreceptor systems in satiated rats. Further, NPY was found to suppress male and female sexual behaviors. The suppressive effects on sexual behavior were apparent prior to or at the time of the onset of feeding after NPY administration. These observations may provide a neurochemical basis for clinical and animal studies on disorders of feeding associated with diminished reproductive functions. 相似文献
45.
实验在15只家兔上进行。以玻璃微电极记录尾核头部(DHCN)痛相关单位,刺激扣带回,观察痛相关单位电活动的变化。在70只DHCN痛相关单位中,有44个对刺激扣带回表现兴奋反应(62.9%),17个呈抑制反应(24.3%),9个变化不明显(12.8%)。进一步观察了52只痛相关单位,在刺激扣带回后再施伤害刺激,43个原痛兴奋单位中15个转为抑制(34.9%),16个进一步兴奋(37.2%)12个无变化(27.9%);原9个痛抑制单位,8个转为兴奋,1个变化不明显。提示,扣带回可通过其下行活动,调制伤害性冲动在尾核水平上的传递。 相似文献
46.
The primary general visceral nucleus in goldfish (Carassius auratus) and catfish (Ictalurus punctatus) is located at the ventroposterior boundary of the vagal gustatory lobe and receives coelomic visceral, but not gustatory inputs. The neuronal tracer horseradish peroxidase (HRP) was employed to visualize sources of input to and ascending projections from the primary general visceral nucleus in these species. In addition, immunocytochemical techniques were utilized to define the cytological divisions within the pontine gustatory-visceral complex. The pontine secondary visceral nuclei in both catfish and goldfish contains numerous somata and fibers immunoreactive for calcitonin gene-related peptide (CGRP). In contrast, the secondary gustatory nuclei are devoid of fibers and cells immunoreactive for CGRP. In both the goldfish and the channel catfish, the primary general visceral nucleus receives input from the vagal gustatory lobe, as well as the medullary reticular formation. In the channel catfish, the primary general visceral nucleus projects bilaterally to the secondary visceral nucleus, which lies rostrolateral to the secondary gustatory nucleus in the dorsal pons. Fibers cross the midline via the rostral part of the isthmic commissure. Injection of HRP into the primary general visceral nucleus of a goldfish labels ascending fibers that project to a secondary visceral nucleus situated ventral, lateral, and rostral to the secondary gustatory complex. In general, the results indicate that general visceral systems ascend in parallel to gustatory systems within the brainstem, and that general visceral but not gustatory nuclei are immunoreactive for the peptide CGRP. 相似文献
47.
本文用Di1荧光染料作轴突示踪剂,主要在大鼠死后固定脑组织上研究双侧脑桥尾侧网状核间联系。结果发现:大量标记纤维聚集成小束,自一侧脑桥尾侧网状核越过中线至对侧同名核,标记纤维呈桔红色、强荧光,直径约1-2微米,纤维主要集中该核的腹侧区。当这些纤维达对侧网状结构内的脑桥尾侧网状部位,其中有些纤维分为上升、下降技。下降纤维行于两侧网状结构的内侧部,同侧约可追踪4-7毫米,对侧约2毫米左右,纤维在下降过程中逐渐减少。活体注射后,可见少量越过中线纤维,并在两侧网状结构内侧部见到少量纤维和散在的终末样纤维。双侧锥体束内均见大量标记纤维,除少数例子外,对侧荧光强度强于同侧。少量交叉纤维入对侧锥体束后入脑桥尾侧网状核。本文还对新近使用于神经解剖研究的荧光染料Dil的优、缺点进行了探讨。 相似文献
48.
During the development of binocular maps in the tectum of Xenopus laevis, axons that relay input from the ipsilateral eye via the nucleus isthmi undergo a prolonged period of shifting connections. This shifting accompanies the dramatic change in eye position that takes place as the laterally placed eyes of the tadpole move dorsofrontally. There is a concomitant expansion of the proportion of tectum that receives contralateral retinotectal input corresponding to the binocular portion of the visual field. Electrophysiological recording demonstrates that ipsilateral units are present in those rostral tectal zones, and anatomical methods show that the isthmotectal axons arborize densely in the rostral region but also extend sparser branches into the caudal zone, which is occupied by contralateral inputs with receptive fields in the monocular zone of the visual field. A mechanism that aligns the ipsilateral and contralateral maps is activity-dependent stabilization of isthmotectal axons that exhibit firing patterns correlated with those of nearby retinotectal axons. In order for activity patterns to function in stabilizing correct connections and promoting the withdrawal of incorrect connections, synaptic communication of some sort is hypothesized to be essential. We have investigated whether isthmotectal axons make morphologically identifiable synapses during development and where such synapses are located. We find evidence for morphologically identifiable synapses in all regions of the tectum, along with many growth cones and structures that are probably immature synapses. As in the adult, the synapses contain round, clear vesicles, have asymmetric specializations, and terminate on structures that appear to be dendrites. In both adult and tadpole, the rarity of serial synapses involving isthmotectal terminals suggests that the interactions between retinotectal and isthmotectal inputs are mediated by postsynaptic dendrites. 相似文献
49.
目的采用电刺激大鼠上矢状窦(SSS)区硬脑膜,观察颈上交感神经节(SCG)摘除术前后在延髓和上颈段三叉神经脊束核一氧化氮合酶(NOS)阳性神经元数目的变化,以探讨交感神经系统在血管源性头痛(如偏头痛)涉及的伤害觉信息传递中的作用。方法以雄性SD大鼠(体重为220~250g)为实验对象,行颈上交感神经节摘除术后再手术暴露其SSS,然后电刺激SSS区硬脑膜,应用免疫组织化学染色技术,观察延髓和上颈段三叉神经脊束核NOS表达的变化。结果NOS免疫反应阳性神经元主要分布在三叉神经脊束核和上颈段脊髓的第Ⅰ、Ⅱ板层,双侧对称。假手术对照组、SCG摘除组每张切片的NOS阳性神经元数分别为150.2±10.3、223.0±11.6,SCG摘除组NOS阳性神经元数目较假手术对照组明显增加(P<0.05)。结论颈交感神经系统参与了头部血管源性疼痛(如偏头痛)中伤害性感觉信息导致的疼痛的产生、传导及调节过程。 相似文献
50.
D.R. Pina S.B. Duarte J. Morceli T. Ghilardi Netto 《Applied radiation and isotopes》2006,64(12):1623-1630
We present the construction of a homogeneous phantom to be used in simulating the scattering and absorption of X-rays by a standard patient chest and skull when irradiated laterally. This phantom consisted of lucite and aluminium plates with their thickness determined by a tomographic exploratory method applied to the anthropomorphic phantom. Using this phantom, an optimized radiographic technique was established for chest and skull of standard sized patient in lateral view. Images generated with this optimized technique demonstrated improved image quality and reduced radiation doses. 相似文献