全文获取类型
收费全文 | 39851篇 |
免费 | 4015篇 |
国内免费 | 998篇 |
专业分类
耳鼻咽喉 | 191篇 |
儿科学 | 817篇 |
妇产科学 | 253篇 |
基础医学 | 4376篇 |
口腔科学 | 815篇 |
临床医学 | 5082篇 |
内科学 | 3190篇 |
皮肤病学 | 400篇 |
神经病学 | 2033篇 |
特种医学 | 1838篇 |
外国民族医学 | 3篇 |
外科学 | 1653篇 |
综合类 | 7809篇 |
现状与发展 | 2篇 |
一般理论 | 3篇 |
预防医学 | 7879篇 |
眼科学 | 1389篇 |
药学 | 4398篇 |
153篇 | |
中国医学 | 1601篇 |
肿瘤学 | 979篇 |
出版年
2024年 | 141篇 |
2023年 | 656篇 |
2022年 | 1268篇 |
2021年 | 1655篇 |
2020年 | 1671篇 |
2019年 | 1519篇 |
2018年 | 1424篇 |
2017年 | 1635篇 |
2016年 | 1795篇 |
2015年 | 1549篇 |
2014年 | 2857篇 |
2013年 | 3152篇 |
2012年 | 2968篇 |
2011年 | 2993篇 |
2010年 | 2370篇 |
2009年 | 1993篇 |
2008年 | 2217篇 |
2007年 | 2235篇 |
2006年 | 1882篇 |
2005年 | 1356篇 |
2004年 | 1131篇 |
2003年 | 893篇 |
2002年 | 747篇 |
2001年 | 623篇 |
2000年 | 569篇 |
1999年 | 429篇 |
1998年 | 315篇 |
1997年 | 306篇 |
1996年 | 253篇 |
1995年 | 287篇 |
1994年 | 245篇 |
1993年 | 211篇 |
1992年 | 189篇 |
1991年 | 154篇 |
1990年 | 146篇 |
1989年 | 118篇 |
1988年 | 110篇 |
1987年 | 115篇 |
1986年 | 65篇 |
1985年 | 133篇 |
1984年 | 106篇 |
1983年 | 94篇 |
1982年 | 70篇 |
1981年 | 52篇 |
1980年 | 49篇 |
1979年 | 33篇 |
1978年 | 24篇 |
1977年 | 13篇 |
1976年 | 17篇 |
1973年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
本文对西宁地区新生儿缺氧缺血性脑病(HIE)颅脑超声诊断分析脑缺氧缺血产生的原因、脑实质损伤程度及预后评估。提出对围产期窒息导致脑缺血性损害的预防措施。 相似文献
52.
目的 探讨大学生睡眠质量、负性情绪在错失恐惧与社交媒体倦怠间的中介作用。 方法 采用错失恐惧量表、社交媒体倦怠量表、匹兹堡睡眠质量指数量表、抑郁-焦虑-压力量表简体中文版对306名大学生进行调查。 结果 错失恐惧、社交媒体倦怠、睡眠质量和负性情绪之间呈两两正相关;错失恐惧能正向预测社交媒体倦怠;睡眠质量和负性情绪在错失恐惧和社交媒体倦怠之间起单独中介作用,且睡眠质量和负性情绪在错失恐惧与社交媒体倦怠之间起链式中介作用,负性情绪各维度效应皆成立。 结论 睡眠质量和负性情绪能够为错失恐惧对社交媒体倦怠的影响提供一个解释机制,大学生的错失恐惧既可以直接影响其社交媒体倦怠水平,也可以通过睡眠质量、负性情绪的独立中介效应以及睡眠质量-负性情绪的链式中介效应间接影响。 相似文献
53.
Virginia Attanasio Frank Andrasik Edward B. Blanchard John G. Arena 《Journal of behavioral medicine》1984,7(2):247-257
The Psychosomatic Symptom Checklist (PSC), a questionnaire assessing psychosomatic symptoms, was administered to two separate samples of college students. For Sample 1 (N=698),the questionnaire was readministered to three separate subsets at intervals of either 1 week (N=143),4 weeks (N=74),or 8 weeks (N=48).Each subset of subjects recompleted the PSC on only one of the three retest intervals. Based on the initial administration an analysis of the normative data revealed a mean total score of 23.7, suggesting a relatively low degree of psychosomatic symptoms in this group. Although total scores decreased slightly over time, test-retest correlations remained high (r>0.80, P<0.0001).Individual item correlations varied and also decreased across time; however, the majority of correlations was greater than r=0.50 throughout. Sample 2 (N=249)completed the PSC, Beck Depression Inventory (BDI), State-Trait Anxiety Inventory (STAI-X), and Rathus Assertiveness Scale (RAS), and intercorrelations were computed between these measures. This analysis revealed little overlap between the psychosomatic complaints assessed by the PSC and other commonly used measures of psychological distress. Finally, a factor analysis revealed one major factor on which all but 2 of the 17 questionnaire items loaded significantly. These results suggest that the PSC is sensitive to psychosomatic distress and remains reliable over time.This reaserch was supported in part by Grants NS-15235 and NS-16891 from NINCDS. 相似文献
54.
Functional aspects of serotonin transmission in the basal ganglia: a review and an in vivo approach using the push-pull cannula technique 总被引:4,自引:0,他引:4
Peripheral deafferentation of the rodent olfactory bulb results in loss of dopamine content, tyrosine hydroxylase activity and immunocytochemical staining for tyrosine hydroxylase in juxtaglomerular dopamine neurons. Reinnervation of the bulb by afferent neurons results in the return of all parameters to control levels suggesting that the dopamine neurons did not degenerate but that the expression of tyrosine hydroxylase enzyme was transneuronally regulated in a static population of juxtaglomerular cells. To evaluate this possibility, we determined the activity and immunocytochemical localization of the second enzyme in the dopamine biosynthetic pathway, DOPA decar?ylase. At a time when tyrosine hydroxylase activity was reduced to 25% of control values, DOPA decar?ylase activity in the lesioned bulb was maintained at about 65% of that in the unlesioned bulb. Immunocytochemical staining with antibodies to both enzymes, performed sequentially in the same sections, demonstrated that in the unlesioned bulb tyrosine hydroxylase and DOPA decar?ylase are co-localized in the same population of juxtaglomerular neurons. Similar results were obtained in adjacent sections each stained with one of the two antibodies. In contrast, in the deafferented bulb, about three times as many neurons were stained with DOPA decar?ylase as with tyrosine hydroxylase antibodies. The DOPA decar?ylase activity measurements and immunocytochemistry argue for the continued presence, in the lesioned olfactory bulb, of a population of tyrosine hydroxylase deficient dopamine neurons.The data suggest that olfactory receptor cell innervation transneuronally regulates the expression of tyrosine hydroxylase by mechanisms separate from those controlling the levels of DOPA decar?ylase. 相似文献
55.
A developmentally immature sleep pattern has been identified in infants with a recent history of an unexplained life-threatening episode of sleep apnoea who are considered at risk for SIDS. In these infants there is a persistence of Sleep Onset REM Periods (SOREMPS) after prolonged wakefulness when compared to controls matched for age, sex, birthweight and race. This sleep characteristic has not been previously reported. 相似文献
56.
基于线性调频信号的高帧率超声成像系统 总被引:5,自引:0,他引:5
基于有限衍射波束的高帧率超声成像系统能实现快速成像,但由于仅通过一次发射事件成像,信噪比较低,本研究针对该问题提出一种改进方案。它采用合成孔径雷达中所使用的线性调频信号作为激励信号,在接收端则利用线性调频信号的脉冲压缩比等于信号的时间带宽积的特征,将接收信号通过匹配滤波器处理。结果表明该方案不仅能显著提高成像系统的信噪比,改善重构图像的质量,增加成像深度,而且不损失分辨率。 相似文献
57.
Martina Adler Frank Rittig Stefan Becker Harald Pasch 《Macromolecular chemistry and physics.》2005,206(22):2269-2277
Summary: The chromatographic analysis of hydrophilic copolymers is complicated due to the fact that in most cases aqueous eluents must be used. In aqueous eluents different polar and ionic effects may disturb the selective interactions between the macromolecules and the stationary phase making it impossible to separate such copolymers with regard to chemical composition. Therefore, 2D chromatography combining a separation according to composition with a separation according to molar mass has been applied mostly to polymers that are soluble in organic solvents. The present contribution describes experimental approaches to analyze such hydrophilic copolymers by 2D‐chromatography. For a model polymer system resulting from the copolymerization of methacrylic acid and a poly(ethylene glycol) macromonomer, it is shown that different analytical techniques including SEC, LC‐CC, MALDI‐TOF MS and 2D chromatography can be used to analyze the different parameters of molecular heterogeneity of such copolymers.
58.
Objective To study on adsorption effect of cadusafos and atropine sulfate by hemoperfusion.Method Hemoperfusions were performed for sheep blood samples with cadusafos and atropineby through imitated extracorporeal closed circulating perfusion apparatus.Residual cadusafos was determined by gas chromatography and residual atropine was determined by high performance liquid chromatography.Result Dose of adsorption agent was 0.5,1.0 and 1.5 g,respectively.Two hours after hemoperfusion with membrane coated activated charcoal,clearance rate of cadusafos in 3 groups all exceeded 90%.and clearance rate of atropine sulfate was 61.9%,84.9%,88.9%,respectively.One and a half hours after hemoperfusion with HA230 absorption resin,clearance rate of eadusafos in 3 groups all exceeded 90%,and clearance rate of atropine sulfate was 88.0%,97.2%,98.4%,respectively.Three hours after hemoperfusion with membrane coated activated charcoal,The concentration ratio of cadusafos and atropine sulfate in blood promoted to 10.1 times,and the ratio was 6.7 times after hemoperfusion with HA230 absorption resin.Conclusion It suggested that cadusafos were mostly removed from blood after 1.5~2.0hours hemoperfusion with membrane activated charcoal or HA230 absorption resin.The concentration ratio of cadusafos and atropine sulfate in blood will increased after hemoperfusion. 相似文献
59.
大学生个体印象管理对其社会网络质量的影响 总被引:1,自引:0,他引:1
目的:研究个体印象管理对其社会网络质量的影响。方法:选用社会网络调查法、大学生印象管理量表,对46名大学生进行调查。结果:印象管理建构的提高不利于朋友网和沟通网的强联系人数量的增加(β分别为-1.04和-1.33,P分别小于0.05和0.01;F值分别为4.19和6.45,P分别小于0.05和0.01),而印象管理动机对强联系人的数量并没有影响,并且印象管理动机和印象管理结构都不影响个体为中心网络的紧密性。结论:只有个体印象管理的建构部分不利于其社会网络中的强联系人数量的增加。其他部分对社会网络无明显影响。 相似文献
60.
Distribution of galanin immunoreactivity in the central nervous system and the responses of galanin-containing neuronal pathways to injury 总被引:18,自引:0,他引:18
J L Ch'ng N D Christofides P Anand S J Gibson Y S Allen H C Su K Tatemoto J F Morrison J M Polak S R Bloom 《Neuroscience》1985,16(2):343-354
Radioimmunoassay and immunocytochemistry were used to study the distribution of galanin, a novel 29 amino acid porcine intestinal peptide, in the central nervous system of the rat and pig. The pattern of distribution was similar in the two species, with the highest concentrations of galanin-like immunoreactivity found in the neurohypophysis, hypothalamus and sacral spinal cord. Immunocytochemical studies of these regions localized galanin-like immunoreactivity to cell bodies in the paraventricular and supraoptic nuclei of the hypothalamus, to fibres in the pars nervosa and to numerous cell bodies and fibres in the dorsal horn of the spinal cord. On both gel and high pressure liquid chromatography, galanin-like immunoreactivity in rat and pig nervous tissue eluted as a single peak in a position similar to purified procine intestinal galanin standard. Surgical and pharmacological manipulations in the rat suggest the presence of galanin in afferent fibres. An increase of galanin-like immunoreactivity was observed in the sacral spinal cord of the rat following thoracic spinal cord transection. Thus galanin-like immunoreactivity in the brain is mainly localized in the hypothalamopituitary region. The decrease of galanin-like immunoreactivity in the dorsal horn of the spinal cord, following dorsal rhizotomy and pre-treatment of rats with capsaicin, indicates that many of the fibres, which are of small diameter, may well be derived from spinal sensory neurones. 相似文献