首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   47002篇
  免费   3679篇
  国内免费   2371篇
耳鼻咽喉   299篇
儿科学   869篇
妇产科学   733篇
基础医学   6041篇
口腔科学   930篇
临床医学   3879篇
内科学   7597篇
皮肤病学   461篇
神经病学   2981篇
特种医学   1173篇
外国民族医学   13篇
外科学   4028篇
综合类   8540篇
现状与发展   6篇
预防医学   1501篇
眼科学   2284篇
药学   6794篇
  8篇
中国医学   2366篇
肿瘤学   2549篇
  2024年   31篇
  2023年   366篇
  2022年   593篇
  2021年   1091篇
  2020年   961篇
  2019年   926篇
  2018年   1060篇
  2017年   1154篇
  2016年   1292篇
  2015年   1401篇
  2014年   2390篇
  2013年   3114篇
  2012年   2637篇
  2011年   3210篇
  2010年   2681篇
  2009年   2899篇
  2008年   3043篇
  2007年   3102篇
  2006年   2816篇
  2005年   2729篇
  2004年   2473篇
  2003年   2307篇
  2002年   1977篇
  2001年   1736篇
  2000年   1494篇
  1999年   1212篇
  1998年   990篇
  1997年   781篇
  1996年   564篇
  1995年   430篇
  1994年   334篇
  1993年   226篇
  1992年   155篇
  1991年   107篇
  1990年   99篇
  1989年   69篇
  1988年   66篇
  1987年   52篇
  1986年   52篇
  1985年   80篇
  1984年   81篇
  1983年   57篇
  1982年   40篇
  1981年   47篇
  1980年   35篇
  1979年   31篇
  1978年   25篇
  1977年   9篇
  1976年   10篇
  1973年   7篇
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
31.
《Cancer cell》2021,39(9):1279-1291.e3
  1. Download : Download high-res image (205KB)
  2. Download : Download full-size image
  相似文献   
32.
ObjectivesRegular physical exercise is known to protect endothelial integrity. It has been proposed that acute exercise-induced changes of the (anti-)oxidative system influence early (glycocalyx shedding) and sustained endothelial activation (shedding of endothelial cells, ECs) as well as endothelial-cell repair by circulating hematopoietic stem and progenitor cells (HPCs). However, results are not conclusive and data in trained participants performing different exercise modalities is lacking.DesignEighteen healthy, well-trained participants (9 runners, 9 cyclists; age: 29.7 ± 4.2 yrs) performed a strenuous acute exercise session consisting of 4 bouts of 4-min high-intensity with decreasing power profile and 3-min low-intensity in-between.MethodsAverage power/speed of intense phases was 85% of the peak achieved in a previous incremental test. Before and shortly after exercise, total oxidative and antioxidative capacities (TAC), shedding of syndecan-1, heparan sulfate, hyaluronan, ECs, and circulating HPCs were investigated.ResultsTAC decreased from 1.81 ± 0.42 nmol/L to 1.47 ± 0.23 nmol/L post-exercise (p = 0.010) only in runners. Exercise-induced early and sustained endothelial activation were enhanced post-exercise- syndecan-1: 103.2 ± 63.3 ng/mL to 111.3 ± 71.3 ng/mL, heparan sulfate: from 2637.9 ± 800.1 ng/mL to 3197.1 ± 1416.3 ng/mL, both p < 0.05; hyaluronan: 84.3 ± 21.8 ng/mL to 121.4 ± 29.4 ng/mL, ECs: from 6.6 ± 4.5 cells/μL to 9.5 ± 6.2 cells/μL, both p < 0.01; results were not different between exercise modalities and negatively related to TAC concentrations post-exercise. HPC proportions and self-renewal ability were negatively, while EC concentrations were positively associated with circulating hyaluronan concentrations.ConclusionsThese results highlight the importance of the antioxidative system to prevent the endothelium from acute exercise-induced vascular injury – independent of exercise modality – in well-trained participants. Endothelial-cell repair is associated with hyluronan signaling, possibly a similar mechanism as in wound repair.  相似文献   
33.
目的 探讨应用丙泊酚持续静脉泵注麻醉对接受手术治疗的原发性肝癌(PLC)患者血管内皮糖萼和脑代谢的影响。方法 2017年8月~2020年7月在我院行微波消融术治疗的PLC患者78例,其中一半患者接受异丙酚麻醉,另一半接受地佐辛麻醉。在术前(T0)、术后1 d(T1)和术后7 d(T2),行血气分析,计算脑氧摄取率(CEO2),采用ELISA法检测硫酸乙酰肝素酶(HS)和多配体蛋白聚糖-1。结果 异丙酚麻醉组诱导时间和苏醒时间分别为(40.3±3.2) s和(6.5±0.8)min,显著短于地佐辛麻醉组【分别为(52.0±3.1) s和(9.8±1.1) min, P<0.05】;在T1和T2,异丙酚麻醉组HS分别为(17.3±2.1)pg/ml和(8.2±0.4)pg/ml,显著低于地佐辛麻醉组【分别为(37.2±5.6)pg/ml和(16.0±2.5)pg/ml,P<0.05】,血清多配体蛋白聚糖-1水平分别为(8.2±0.1)pg/ml和(3.8±0.1)pg/ml, 显著低于地佐辛麻醉组【分别为(11.7±1.4)pg/ml和(5.9±0.2) pg/ml,P<0.05】,CEO2分别为(28.0±2.4)%和(32.7±3.7)%,显著高于地佐辛麻醉组【分别为(25.0±3.1)%和(29.7±4.1)%,P<0.05】。结论 应用异丙酚持续静脉泵注麻醉在接受微波消融治疗的PLC患者能抑制血管内皮糖萼的激活,改善脑代谢,提高麻醉效果,减少并发症的发生。  相似文献   
34.
目的构建靶向血管内皮生长因子受体2(VEGFR2)可调控活性的小分子门控嵌合抗原受体T(smgCAR-T)细胞系统并在体外验证其抗肿瘤和可调节活性。方法采用基因全长合成和磷酸钙转染法构建smgCAR-T及其阳性(CAR+-T)和阴性(CAR--T)对照细胞。同时构建表达VEGFR2的小鼠结直肠癌细胞(MCA38VEGFR2+)。验证并筛选构建成功的细胞后再体外验证CAR-T细胞靶向结合能力。在不同的效靶比下检测白细胞介素-2和肿瘤坏死因子-γ的浓度来评估CAR-T细胞的体外分泌功能,用乳酸脱氢酶浓度评估CAR-T细胞的体外抗肿瘤活性。组间的比较采用t检验或单因素方差分析。结果基因测序和流式细胞术证实CAR-T细胞和靶细胞构建成功。与对照组比较,CAR+-T细胞+MCA38VEGFR2+组具有最强的靶细胞杀伤能力。在smgCAR-T细胞+MCA38VEGFR2+组中,随着C16-(S)-3-甲基吲哚雷帕霉素(Rapalog)滴度升高靶细胞杀伤率逐渐升高;当Rapalog为40 nmol/L时杀伤率达到最大值,为(66.25±13.20)%。分别向smgCAR-T细胞+MCA38VEGFR2+细胞组(A和B组)加入40 nmol/L的Rapalog后,在24 h时可观察到两组杀伤率出现同步升高[(44.25±6.24)%比(49.25±5.56)%,t=1.197,P>0.05],差异无统计学意义。在置换培养基后,再次添加了Rapalog的A组中观察到靶细胞杀伤率升高明显;而未再次添加Rapalog的B组中靶细胞杀伤率升高缓慢;此时,A和B组杀伤率差异有统计学意义[(89.00±3.16)%比(56.50±6.61)%,t=8.873,P<0.01]。结论构建的smgCAR-T细胞在体外展现出一定的抗肿瘤活性,且其活性受小分子化合物Rapalog的可逆调控。  相似文献   
35.
36.
《Brain stimulation》2021,14(4):927-937
BackgroundIncreases in the volume of the amygdala and hippocampus after electroconvulsive therapy (ECT) are among the most robust effects known to the brain-imaging field. Recent advances in the segmentation of substructures of these regions allow for novel insights on the relationship between brain structure and clinical outcomes of ECT.ObjectiveWe aimed to provide a comprehensive synthesis of evidence available on changes in brain structure after ECT, including recently published data on hippocampal subfields.MethodsA meta-analysis of published studies was carried out using random-effects models of standardized mean change of regional brain volumes measured with longitudinal magnetic resonance imaging of depressive patients before and after a series of ECT.ResultsData from 21 studies (543 depressed patients) were analysed, including 6 studies (118 patients) on hippocampal subfields. Meta-analyses could be carried out for seven brain regions for which data from at least three published studies was available. We observed increases in left and right hippocampi, amygdalae, cornua ammonis (CA) 1, CA 2/3, dentate gyri (DG) and subicula with standardized mean change scores ranging between 0.34 and 1.15. The model did not reveal significant volume increases in the caudate. Meta-regression indicated a negative relationship between the reported increases in the DG and relative symptom improvement (−0.27 (SE: 0.09) per 10%).ConclusionsECT is accompanied by significant volume increases in the bilateral hippocampus and amygdala that are not associated with treatment outcome. Among hippocampal subfields, the most robust volume increases after ECT were measured in the dentate gyrus. The indicated negative correlation of this effect with antidepressant efficacy warrants replication in data of individual patients.  相似文献   
37.
《Clinical neurophysiology》2021,132(12):3104-3115
ObjectiveWe aimed to establish an objective neurophysiological test protocol that can be used to assess the somatosensory nervous system.MethodsIn order to assess most fiber subtypes of the somatosensory nervous system, repetitive stimuli of seven different modalities (touch, vibration, pinprick, cold, contact heat, laser, and warmth) were synchronized with the electroencephalogram (EEG) and applied on the cheek and dorsum of the hand and dorsum of the foot in 21 healthy subjects and three polyneuropathy (PNP) patients. Latencies and amplitudes of the modalities were assessed and compared. Patients received quantitative sensory testing (QST) as reference.ResultsWe found reproducible evoked potentials recordings for touch, vibration, pinprick, contact-heat, and laser stimuli. The recording of warm-evoked potentials was challenging in young healthy subjects and not applicable in patients. Latencies were shortest within Aβ-fiber-mediated signals and longest within C-fibers. The test protocol detected function loss within the Aβ-fiber and Aδ-fiber-range in PNP patients. This function loss corresponded with QST findings.ConclusionIn this pilot study, we developed a neurophysiological test protocol that can specifically assess most of the somatosensory modalities. Despite technical challenges, initial patient data appear promising regarding a possible future clinical application.SignificanceEstablished and custom-made stimulators were combined to assess different fiber subtypes of the somatosensory nervous system using modality-specific evoked potentials.  相似文献   
38.
39.

Objective

Hypertonic saline (HTS) has potent immune and vascular effects. We assessed recipient pretreatment with HTS on allograft function in a porcine model of heart transplantation and hypothesized that HTS infusion would limit endothelial and left ventricular (LV) dysfunction following transplantation.

Methods

Heart transplants were performed after 6 hours of cold ischemic storage. Recipient pigs were randomized to treatment with or without HTS (7.5% NaCl) before cardiopulmonary bypass (CPB). Using a myograft apparatus, coronary artery endothelial-dependent (Edep) and -independent (Eind) relaxation was assessed. LV performance was determined using pressure-volume loop analysis. Pulmonary interleukin (IL)-2, IL-6, and tumor necrosis factor (TNF)-α expression was measured.

Results

Weaning from CPB and LV performance after transplantation were improved in HTS-treated animals. Successful weaning from CPB was greater in the HTS-treated hearts (8 of 8 vs 2 of 8; P < .05). Mean LV functional recovery was improved in the HTS-treated animals, as assessed by preload recruitable stroke work (65 ± 10% vs 27 ± 10%; P < .001) and end-systolic elastance (55 ± 7% vs 37 ± 4%; P < .001). Treatment with HTS resulted in improved Edep (mean maximum elastance [Emax], 56 ± 5% vs 37 ± 7%; P < .001) and Eind (mean Emax%, 77 ± 6% vs 52 ± 4%; P < .001) vasorelaxation compared with control. Pulmonary expression of IL-2, IL-6, and TNF-α increased following transplantation, whereas HTS therapy attenuated IL production (P < .001). Transplantation increased plasma TNF-α levels and LV TNF-α expression, whereas HTS prevented this up-regulation (P < .001).

Conclusions

Recipient HTS pretreatment preserves allograft vasomotor and LV function, and HTS therapy limits CPB-induced injury. HTS may be a novel recipient intervention to prevent graft dysfunction.  相似文献   
40.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号