全文获取类型
收费全文 | 22779篇 |
免费 | 2413篇 |
国内免费 | 750篇 |
专业分类
耳鼻咽喉 | 527篇 |
儿科学 | 569篇 |
妇产科学 | 94篇 |
基础医学 | 3471篇 |
口腔科学 | 384篇 |
临床医学 | 2417篇 |
内科学 | 3122篇 |
皮肤病学 | 258篇 |
神经病学 | 3909篇 |
特种医学 | 408篇 |
外国民族医学 | 3篇 |
外科学 | 1535篇 |
综合类 | 2213篇 |
现状与发展 | 1篇 |
预防医学 | 1929篇 |
眼科学 | 946篇 |
药学 | 2714篇 |
3篇 | |
中国医学 | 584篇 |
肿瘤学 | 855篇 |
出版年
2024年 | 54篇 |
2023年 | 443篇 |
2022年 | 636篇 |
2021年 | 933篇 |
2020年 | 1022篇 |
2019年 | 1069篇 |
2018年 | 1068篇 |
2017年 | 989篇 |
2016年 | 945篇 |
2015年 | 878篇 |
2014年 | 1393篇 |
2013年 | 1497篇 |
2012年 | 1284篇 |
2011年 | 1467篇 |
2010年 | 1164篇 |
2009年 | 988篇 |
2008年 | 1042篇 |
2007年 | 955篇 |
2006年 | 924篇 |
2005年 | 781篇 |
2004年 | 686篇 |
2003年 | 664篇 |
2002年 | 519篇 |
2001年 | 520篇 |
2000年 | 436篇 |
1999年 | 384篇 |
1998年 | 297篇 |
1997年 | 246篇 |
1996年 | 207篇 |
1995年 | 221篇 |
1994年 | 201篇 |
1993年 | 177篇 |
1992年 | 193篇 |
1991年 | 161篇 |
1990年 | 161篇 |
1989年 | 140篇 |
1988年 | 117篇 |
1987年 | 99篇 |
1986年 | 78篇 |
1985年 | 139篇 |
1984年 | 127篇 |
1983年 | 78篇 |
1982年 | 96篇 |
1981年 | 84篇 |
1980年 | 97篇 |
1979年 | 73篇 |
1978年 | 42篇 |
1977年 | 33篇 |
1976年 | 43篇 |
1973年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
目的对弱视儿童不同部位所记录的视觉诱发电位(VEP)进行比较研究。方法分析52只弱视眼常规视觉刺激时于O1、O2、Oz三点记录的VEP,并以66只健康眼的VEP作比较。结果弱视眼三个点VEP的异常率:Oz一个点23%,O1、O2两点为75%,Oz、O1和O2三个点为81%。与正常眼比较,弱视眼此三点VEP的潜伏期均显著延长,Oz点波幅显著降低,O1、O2点波幅则无显著差异。弱视眼的VEPO1和O2点潜伏期较其Oz点显著延长,波幅亦显著降低。结论对VEP的评价,必须考虑到有无弱视和记录部位这两个因素。 相似文献
992.
对12例臂丛神经损伤患者进行了磁刺激运动诱发电位(MEP)的测定,并与同时进行的肌电图(EMG)、神经传导速度(NCV)进行了比较,结果发现MEP的阳性率与EMG近似,对臂丛神经损伤的定位及鉴别诊断有意义。 相似文献
993.
酒依赖高发家系成员听觉P3的对照研究 总被引:2,自引:0,他引:2
为了验证事件相关电位P3波幅降低是酒依赖的遗传标志的假说,作者在5个酒依赖高发家系32名18周岁以上成员(其中有14名酒依赖者)和8个无酒依赖的对照家系45名18周岁以上成员中采用Oddbal方法测查了听觉P3,结果发现,高发家系中的酒依赖者、非酒依赖者与对照家系成员之间的P3波幅和潜伏期差异均无统计学显著性。作者探讨了假说未得到验证的原因。 相似文献
994.
目的:(1)探讨白内障囊外摘除术前术后及人工晶体植入术后视觉诱发电位幅值及潜时变化特征;(2)探讨白内障囊外摘除术术前P—VEP,F—VEP,F—ERG联合预测的必要性。方法:采用重庆泰克医电仪器公司产TEC—100C视觉电生理仪。对白内障患者实行分组测量。术前均测F—ERG,P—VEP,部分病例增测F—VEP。结果:114例术前F—ERG正常,P—VEP测量其P_(100)波幅值潜时均异常:P_(100)波幅值降低,潜时延长,术后及人工晶体植入后幅值,潜时都有所改善,而并发性白内障,代谢性白内障变化不明显。结论:据视觉诱发电位的变化,老年性白内障组,外伤性白内障组术后应及时装入人工晶体,并发性白内障组,代谢性白内障组装入人工晶体临床意义不大。术前联合测试(VEP ERG)对视力预后、以及眼底病变的定量诊断意义重大。 相似文献
995.
Peer Arts Jessica Garland Alicia B. Byrne Tristan S.E. Hardy Milena Babic Jinghua Feng Paul Wang Thuong Ha Sarah L. King‐Smith Andreas W. Schreiber April Crawford Nick Manton Lynette Moore Christopher P. Barnett Hamish S. Scott 《American journal of medical genetics. Part A》2020,182(5):1273-1277
Autosomal dominant (de novo) mutations in PBX1 are known to cause congenital abnormalities of the kidney and urinary tract (CAKUT), with or without extra‐renal abnormalities. Using trio exome sequencing, we identified a PBX1 p.(Arg107Trp) mutation in a deceased one‐day‐old neonate presenting with CAKUT, asplenia, and severe bilateral diaphragmatic thinning and eventration. Further investigation by droplet digital PCR revealed that the mutation had occurred post‐zygotically in the father, with different variant allele frequencies of the mosaic PBX1 mutation in blood (10%) and sperm (20%). Interestingly, the father had subclinical hydronephrosis in childhood. With an expected recurrence risk of one in five, chorionic villus sampling and prenatal diagnosis for the PBX1 mutation identified recurrence in a subsequent pregnancy. The family opted to continue the pregnancy and the second affected sibling was stillborn at 35 weeks, presenting with similar severe bilateral diaphragmatic eventration, microsplenia, and complete sex reversal (46, XY female). This study highlights the importance of follow‐up studies for presumed de novo and low‐level mosaic variants and broadens the phenotypic spectrum of developmental abnormalities caused by PBX1 mutations. 相似文献
996.
《Pathology, research and practice》2020,216(5):152914
DNA methylation is one of the epigenetic mechanisms to regulate gene expression and frequently occurs in human cancer cells. T-cadherin (CDH13) is a new member of the cadherin superfamily and possesses multiple functions. Our study included 26 normal controls (NCs), 65 chronic hepatitis B patients (CHB), 14 liver cirrhosis patients (LC) and 157 hepatocellular carcinoma patients (HCC). We mainly focused on the mRNA expression and methylation status of CDH13 in peripheral blood mononuclear cells (PBMCs), which were detected by semi-quantitative real-time polymerase chain reaction (RT-qPCR) and methylation-specific polymerase chain reaction (MSP) respectively. The CDH13 mRNA level was lower in HCC, especially in early-stage of HCC than in NCs and CHB groups (p < 0.05). Methylation frequency of the CDH13 promoter was significantly higher in HCC patients than in the NCs and CHB groups (67.52 % vs 0.00 %, p < 0.001, 67.52 % vs 52.31 %, p < 0.05, respectively). CDH13 mRNA level was significantly and relatively lower in methylated groups than in unmethylated groups among the whole participants. The methylation level of CDH13 promoter in HCC might be influenced or partly influenced by some critical factors such as TBil, ALB and AFP (p < 0.05). As an important factor in signaling pathway regulating by CDH13 to promote carcinogenesis, JNK level was significantly higher in HCC which had a higher methylation frequency than in NCs, CHB and LC (p < 0.05). Furthermore, the combination of the methylated CDH13 level and AFP level showed a better score: AUC = 0.796 (SE = 0.031, 95 %CI 0.735–0.857; p < 0.001) in male and AUC = 0.832 (SE = 0.057, 95 %CI 0.721–0.944; p < 0.001) in female compared to AFP alone for diagnosing HCC from NCs, CHB and LC. The methylation of CDH13 promoter was an independent predictor for assessing the prognosis of HCC patients (r=-1.378 p < 0.05). In conclusion, hypermethylation of CDH13 in PBMCs was associated with the underexpression of mRNA and the high risk of HCC. The methylation status of the CDH13 promoter in PBMCs was a potential noninvasive biomarker to predict the prognosis of HCC patients. 相似文献
997.
目的利用体感诱发电位及运动功能评分,评价医用自交联透明质酸钠凝胶预防椎板切除术后硬膜外粘连的安全性。方法将L5全椎板切除的新西兰兔24只随机分为4组,A组为对照组:术区生理盐水冲洗后关闭切口;B组、C组、D组均为实验组:均在术区硬脊膜暴露区覆盖医用自交联透明质酸钠凝胶,而覆盖剂量各不相同,分别为0.5、0.75和1.0ml。分别于麻醉后,椎板切除术后,闭合手术切口之后,术后8周这4个时间点进行体感诱发电位监测并记录潜伏期值。并分别于术前,术后1d,术后8周对各组动物进行后肢运动功能评分。结果麻醉后和椎板切除术后各组潜伏期值无统计学差异(P0.05)。在关闭切口后测定各组的潜伏期值显示:A组和B组潜伏期值均无延迟(P0.05),C组和D组潜伏期值出现明显延迟(P0.05)。在术后8周复测各组潜伏期值,均处于正常范围(P0.05)。运动功能评分结果:术前所有动物评分均正常。在术后1d,A组和B组动物的评分仍然正常,C组和D组的动物评分下降。在术后8周,各组动物的运动功能评分均再次正常。结论体感诱发电位是测定脊髓损伤的敏感指标;椎板切除术后局部覆盖预防粘连剂有剂量的要求,0.5ml的医用自交联透明质酸钠凝胶不会对该动物模型的脊髓的电生理功能及后肢运动功能产生影响。 相似文献
998.
Chronic Psychophysiological Insomnia: Hyperarousal and/or Inhibition Deficits? An ERPs Investigation 总被引:1,自引:0,他引:1
STUDY OBJECTIVES: Chronic primary insomnia has been hypothesized to result from conditioned arousal or the inability to initiate normal sleep processes. The event-related potentials (ERPs) N1, P2, and N350 are useful indexes of arousal. The objective is to compare these ERPs in primary chronic psychophysiological insomniacs (INS) and good sleepers (GS) during multiple recordings. PARTICIPANTS: Participants were 15 INS (mean age = 46 years, SD = 7.5) and 16 GS (mean age = 37 years, SD = 10.1). METHODS AND PROCEDURE: Following a multistep clinical evaluation, INS and GS participants underwent 4 consecutive nights of PSG recordings (N1 to N4). ERPs were recorded on the 3rd and 4th nights in the sleep laboratory (N3 and N4). ERPs recordings were made during wake on both nights (in the evening and upon awakening), with the addition of sleep-onset recordings on N4. Auditory stimuli consisted of "standard" and "deviant" tones. STATISTICAL ANALYSIS: Repeated measures ANOVAs were computed for each ERP for each recording for each type of stimulus. RESULTS: The amplitude of P2 and N350 was greater for the deviant than for the standard stimulus in both groups. The amplitude of N1 was larger in INS than GS in the morning and the evening. While the amplitude of N350 was larger in GS than in INS at sleep onset, the amplitude of P2 was greater in INS than in GS at that time. CONCLUSION: Signs of greater cortical arousal in psychophysiological insomnia individuals are observed, especially upon awakening in the morning. However, at sleep onset, difficulties from disengaging from wake processes and some inability at initiating normal sleep processes appear also present in individuals with insomnia compared to good sleepers. 相似文献
999.
D. R. Curtis B. D. Gynther G. Lacey D. T. Beattie 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1997,113(3):520-533
In the ventral horn of the lumbar spinal cord of cats anaesthetised with pentobarbitone sodium, microelectrophoretically
administered (–)-baclofen, but not (+)-baclofen, reversibly reduced the duration of the orthodromic action potential of muscle
group Ia afferent terminations, but not those of muscle group I afferent myelinated fibres. The presumably submicromolar concentrations
are already known to reversibly reduce excitatory transmitter release from muscle group Ia afferent terminations. Action potential
durations were estimated from threshold recovery curves after an orthodromic impulse using an extracellular microstimulation
technique. Both of these presynaptic effects of (–)-baclofen were blocked by baclofen antagonists, and neither appeared to
be reduced by the potassium channel blocking agents tetraethylammonium and 4-aminopyridine. Tetraethylammonium and 4-aminopyridine
also did not significantly modify the reduction by (–)-baclofen of monosynaptic field potentials in the lumbar cord of rats
anaesthetised with pentobarbitone sodium. In the cat the maximum reduction by (–)-baclofen of termination action potentials
was considerably less than that produced by cadmium ions, which, unlike (–)-baclofen, also reduced the action potential duration
of group I myelinated fibres. These findings are consistent with a reduction by (–)-baclofen of the influx of calcium through
voltage-activated channels in the membrane of group Ia terminations, a proposal which also accounts for the reduction by (–)-baclofen
of the release of GABA at axo-axonic depolarizing synapses on these terminations. The results are discussed in relation to
the mode of action of (–)-baclofen and the different sensitivities of transmitter release at various central synapses.
Received: 30 May 1996 / Accepted: 11 September 1996 相似文献
1000.
Thomas Frodl-Bauch Norbert Kathmann Hans-Jürgen Möller Ulrich Hegerl 《Brain topography》1997,10(1):3-8
The mismatch negativity (MMN) is an event related potential component elicited by changes in duration, frequency or intensity of the stimuli during repetitive series of equal standard stimuli. In the present study we compared duration and frequency MMN using dipole source analysis concerning both the test-retest reliability of MMN-amplitudes and the locations of the potential sources. Furthermore, the influence of attention for test-retest-reliability was studied. Therefore, two groups of healthy subjects were investigated with different attentional manipulations. Twenty-one healthy subjects had to perform a visual attention task during the recording and 21 healthy subjects had no additional task to perform. All subjects were studied twice with a time interval of 3 weeks. Test-retest reliability was sufficiently high for the frequency but slightly lower for the duration MMN. The locations of the frequency and duration MMN-dipoles were in the auditory cortex with a more anterior and caudal location for the frequency MMN-dipoles. The latter finding supports the hypothesis that the frequency and duration MMNs have separate neuronal generators. 相似文献