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   39886篇
  免费   4506篇
  国内免费   3008篇
耳鼻咽喉   435篇
儿科学   406篇
妇产科学   329篇
基础医学   3797篇
口腔科学   688篇
临床医学   5095篇
内科学   5354篇
皮肤病学   502篇
神经病学   1758篇
特种医学   1945篇
外国民族医学   11篇
外科学   4883篇
综合类   8070篇
现状与发展   14篇
一般理论   2篇
预防医学   3282篇
眼科学   881篇
药学   4320篇
  34篇
中国医学   2696篇
肿瘤学   2898篇
  2024年   209篇
  2023年   901篇
  2022年   2024篇
  2021年   2448篇
  2020年   1968篇
  2019年   1463篇
  2018年   1518篇
  2017年   1478篇
  2016年   1325篇
  2015年   2010篇
  2014年   2415篇
  2013年   2529篇
  2012年   3244篇
  2011年   3528篇
  2010年   2581篇
  2009年   2122篇
  2008年   2288篇
  2007年   2271篇
  2006年   1982篇
  2005年   1819篇
  2004年   1201篇
  2003年   979篇
  2002年   834篇
  2001年   650篇
  2000年   586篇
  1999年   555篇
  1998年   321篇
  1997年   349篇
  1996年   293篇
  1995年   244篇
  1994年   218篇
  1993年   129篇
  1992年   106篇
  1991年   98篇
  1990年   112篇
  1989年   100篇
  1988年   85篇
  1987年   69篇
  1986年   61篇
  1985年   43篇
  1984年   30篇
  1983年   15篇
  1982年   35篇
  1981年   40篇
  1980年   18篇
  1979年   13篇
  1978年   16篇
  1977年   19篇
  1976年   17篇
  1975年   14篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
Tail-welded blanks (TWBs) are widely used in automotive bodies to improve the structural performance and reduce weight. The stiffness and modal lightweight design optimisation of TWBs for automotive doors was performed in this study. The finite element model was validated through physical experiments. An L27 (312) Taguchi orthogonal array was used to collect the sample points. The multi-objective optimisation problem was transformed into a single-objective optimisation problem based on the grey relational degree. The optimal combination of structural design parameters was obtained for a tail-welded door using the proposed method, and the weight of the door structure was reduced by 2.83 kg. The proposed optimisation method has fewer iterations and a lower computational cost, enabling the design of lightweight TWBs.  相似文献   
132.
目的:观察蜗神经发育不良的患儿人工耳蜗植入术后的效果,探讨术前HRCT和MRI对蜗神经发育不良的诊断及评估价值。方法:回顾性分析10例蜗神经发育不良患儿的术前影像学资料及人工耳蜗植入术后对声音的反应和语训效果。结果:3例(6耳)HRCT提示双侧内耳道狭窄,耳蜗、前庭和半规管发育正常,MRI提示蜗神经发育不良。7例(14耳)HRCT提示双侧内耳道正常,其中1例IP-Ⅰ型,伴前庭半规管发育不良,6例双侧耳蜗、前庭和半规管发育正常;7例MRI提示蜗神经发育异常。10例患儿均行人工耳蜗植入,经过12~32个月的随访,3例学会简单语言,MAIS量表、CAP分数及SIR分级较前提高;1例虽能讲话,但口齿含糊;4例对声音有反应,仅能说"爸爸"、"妈妈"等单音节词;2例无反应(1例取出)。10例蜗神经发育不良患儿同其他蜗神经发育正常儿童相比,术后康复情况明显落后。结论:对蜗神经缺陷患儿,术前仅做颞骨HRCT检查易漏诊,结合内耳道MRI(含内耳道斜矢状位重建)已成必须。若发现疑似病例,应慎重筛选,告知行人工耳蜗植入效果不佳的巨大可能性,严格掌握手术指征。  相似文献   
133.

目的:分析永存原始玻璃体增生症(PHPV)和先天性纤维血管瞳孔膜(CFPM)的临床特征异同。

方法:回顾性分析2006-03/2021-12在空军军医大学西京医院眼科接受手术治疗的PHPV(PHPV组)和CFPM患儿(CFPM组)的眼部生物测量参数、临床表现、病变的形态学特点。

结果:纳入PHPV患儿56例61眼,CFPM患儿24例25眼; PHPV和CFPM的发病年龄相似、无性别差异,均以单眼患病为主,其占比分别为91%和96%。PHPV合并白内障患眼可有多种并发症和眼发育异常,CFPM主要为不同程度的瞳孔区堵塞及形态异常。PHPV组和CFPM组单眼患病患儿患眼前房深度(ACD)均小于对侧眼,手术年龄≤24月龄患儿患眼眼轴长度(AL)均小于对侧眼(P<0.05); PHPV组单眼患病患儿患眼角膜直径(CD)小于对侧眼、眼压高于对侧眼(均P<0.05); CFPM组单眼患病患儿患眼与对侧眼CD、IOP比较均无显著差异(P>0.05)。PHPV组患儿患眼ACD小于CFPM组患眼(P<0.05)。术中发现PHPV纤维血管膜组织位于晶状体后、玻璃体腔内,而CFPM纤维血管膜位于虹膜与晶状体前囊膜之间,很少累及晶状体。

结论:PHPV和CFPM有非常相似的临床特点,提示PHPV和CFPM可能是永存胚胎血管(PFV)的不同表现形式,但PHPV病变范围更广、病情更复杂。  相似文献   

134.
Cornuside is an iridoid glycoside from Cornus officinalis, with the activities of anti-inflammatory, antioxidant, anti-mitochondrial dysfunction, and neuroprotection. In the present research, a triple-transgenic mice model of AD (3 × Tg-AD) was used to explore the beneficial actions and potential mechanism of cornuside on the memory deficits. We found that cornuside prominently alleviated neuronal injuries, reduced amyloid plaque pathology, inhibited Tau phosphorylation, and repaired synaptic damage. Additionally, cornuside lowered the release of interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and nitric oxide (NO), lowered the level of malondialdehyde (MDA), and increased the activity of superoxide dismutase (SOD) and the level of glutathione peroxidase (GSH-Px). Cornuside also significantly reduced the activation of astrocytes and modulated A1/A2 phenotypes by the AKT/Nrf2/NF-κB signaling pathway. We further confirmed that LY294002 and Nrf2 silencing could block the cornuside-mediated phenotypic switch of C6 cells induced by microglia conditioned medium (MCM) in response to lipopolysaccharide (LPS), which indicated that the effects of cornuside in astrocyte activation are dependent on AKT/Nrf2/NF-κB signaling. In conclusion, cornuside may regulate the phenotypic conversion of astrocytes, inhibit neuroinflammation and oxidative stress, improve synaptic plasticity, and alleviate cognitive impairment in mice through the AKT/Nrf2/NF-κB axis. Our present work provides an experimental foundation for further research and development of cornuside as a candidate drug for AD management.  相似文献   
135.
通过对新疆维吾尔药成药专利申请及研究学术文献发表情况进行系统性分析,旨在研究目前维药成药研究的现代化进展。研究发现目前维药成药专利申请多为组方类专利,学术研究文献则主要集中在临床观察等方面,而这两方面涉及到的维药都主要集中在皮肤病,风湿病等少数几个治疗领域。  相似文献   
136.
AIM OF THE STUDY: Chi-Zhi-Huang decoction (PGR) is one of the traditional Chinese medicine (TCM) preparations with unique effect on withdrawing jaundice and has been used to treat icteric patients in China for many years. In this research, we aim at to evaluate the potential activity of PGR in restoring hepatic drug metabolism in a damaged liver. MATERIALS AND METHODS: A cocktail approach with caffeine (10mg/kg), dapsone (10mg/kg) and chlorzoxazone (20mg/kg) respectively as probe drug of cytochrome P450 (CYP) isoform of CYP 1A2, 3A4 and 2E1 was used to evaluate its possible effects on Phase I oxidative metabolism. Pretreated with three dosages of PGR water extract (0.75, 1.5 and 3g/kg, po) for 5 days, male Wistar rats (220-240 g) were intoxicated by phenylisothiocyanate (PITC, 100mg/kg, po) 24h before probes intravenous injection. The pharmacokinetics of the probes in the blood was determined simultaneously by HPLC, and their non-compartmental parameters were used to evaluate the metabolic difference among the groups. Moreover, the levels of liver enzymes (ALT, AST, ALP) and bilirubins were also measured for insight of liver function. RESULTS: The findings in this study suggest that PGR induces CYP 3A4, does not have much effect on CYP 2E1, and inhibits CYP 1A2 at high dosage. CONCLUSION: The current pharmacokinetic approach allowed the protective effects of PGR on oxidative drug metabolism in damaged liver to be systemically examined and will certainly help in the explanation of synergistic effect of the composites formula.  相似文献   
137.
OBJECTIVE: To establish a simple and quick method that could be used to predict the occurrence of hypoxic ischemic encephalopathy (HIE) as early as possible by investigating the variations of nucleated red blood cells per 100 white blood cell (NRBC/100 WBC) counts and lactate levels in cord blood. METHODS: In 46 cases of acute fetal distress (AFD) and 54 cases of chronic fetal distress (CFD) neonates we measured the percentage (NRBCs/100 WBC) and lactate in the umbilical blood. RESULTS: Both lactate levels and NRBC/100WBC counts were higher in CFD and AFD groups than in controls (both P<0.01). The numbers of NRBC/100 WBC and the values of lactate in moderate-severe HIE group were higher than in mild-HIE group (P=0.002 and P=0.042, respectively). The combined sensitivity and specificity was 94% and 96% at 15NRBC/100WBC and 4.25 mmol/L level by combined detecting NRBC and lactate to predict HIE. Three infants (including 1 death and 2 survivors) had the highest levels of NRBC/100WBC and lactate in cord blood, and the 2 survivors had the lowest mental development index (MDI) and psychomotor development index (PDI). CONCLUSIONS: Combined detection with NRBC/100WBC and lactate allows early prediction of development and severity of HIE. The levels of these parameters are related to the neurodevelopment outcome of HIE infants.  相似文献   
138.
Approximately 60% to 70% of epithelial ovarian cancers are diagnosed at an advanced stage. Treatment of advanced disease involves cytoreductive surgery followed by systemic treatment with paclitaxel and platinum. Overall response rates are high, ranging from 70-80%; however, 70-80% of responders will relapse and require further systemic chemotherapy. Patients who experience disease relapse with platinum-free interval of less than 6 months are considered as platinum-refractory/resistant individuals. In this clinical setting, agents with non-cross-resistance to first-line therapy and favorable toxicity profiles are usually chosen. In the management of relapsed patients with platinum-free interval over 6 months, the generally accepted recommendation is retreatment with a platinum plus paclitaxel combination. In general, treatment of recurrent disease is palliative and is initiated with the goals of controlling disease-related symptoms, limiting treatment-related toxicity, maintaining or improving quality of life, delaying time to progression, and prolonging survival. A number of currently available and novel investigating agents in recurrent epithelial ovarian cancer will be reviewed in this context.  相似文献   
139.
BACKGROUND: The pre-eclampsia is characterized by placental defective angiogenesis and maternal vascular/endothelial dysfunction. Recently, the decrease and senescence of endothelial progenitor cells (EPC) has been observed in maternal circulation with pre-eclampsia. Given the essential involvement of EPC in neovascularization and reendothelialization, we investigate whether or not the depletion of EPC is existent in placental/fetal circulation with maternal pre-eclampsia. METHODS: Samples of venous cord blood were collected during the labor of preeclamptic mothers (n = 14) and normotensive controls (n = 10). Circulating EPC were enumerated as AC133+/KDR+ cells via fluorescence-activated cell sorting (FACS) analysis. Additionally, EPC were expanded in vitro and identified by DiI-acLDL uptake and lectin staining by direct fluorescent staining under a laser scanning confocal microscope. EPC proliferation, migration and vasculogenesis activities were determined by MTT, modified Boyden chamber assay and in vitro vasculogenensis assay. RESULT: The placental/fetal circulating EPC numbers were significantly decreased in the pre-eclampsia group compared with the control (median, 200; range, 100-440 cells/mL vs 390; 270-440 cells/mL, P < 0.001), and after in vitro cultivation the numbers of EPC also decreased in pre-eclampsia group (19.5; 5.0-32.0 vs 39.5; 31.2-52.0 EPC/x200 field; P < 0.001). Both circulating EPC and cultivated EPC were inversely correlated with cord blood level of soluble fms-like tyrosine kinase 1 (sFlt-1). In addition, the EPC from patients with pre-eclampsia were significantly impaired in their proliferation, migration and vasculogenesis capacities. CONCLUSION: The present study documented the decrease and dysfunction of placental/fetal circulating EPC in patients with pre-eclampsia. The alteration is probably associated with the increased sFlt-1 levels in the umbilical cord blood.  相似文献   
140.
IntroductionWhile sexual dysfunctions are closely related to overall well-being, epidemiological data based on population-based surveys remain scant.AimTo investigate the prevalence and correlates for sexual dysfunctions in urban China.MethodsOf the 4,157 urbanites sampled nationally, 3,159 participants completed the interview, giving a response rate of 76%. The focus was on 78% of these participants (2,478 adults aged 20–64) who were sexually active within a stable sexual relationship, typically with the spouse.Main Outcome MeasurePrevalence and correlates for sexual dysfunctions.ResultsFully 35% of women and 21% of men had at least one persistent sexual dysfunction. Prevalence by age was similar to the results from Western developed countries. With sharp differences for men and women, the correlates for distress in China were multiple, with aging and physical issues accounting for only a portion of the total set of mental health, stress, relationship, and values and knowledge issues related to reports of sexual dysfunctions.ConclusionsBoth the prevalence and correlates for sexual dysfunctions in urban China were similar to those in other societies. Mental distress, age, and poor communication (producing the report that “my partner does not understand my sexual needs”) were the correlates shared by both men and women. Other correlates were more distinct by gender. The multiplicity of correlates for men and women suggests a need for a holistic approach to sexual dysfunctions. Parish WL, Laumann EO, Pan S, and Hao Y. Sexual dysfunctions in urban China: A population-based national survey of men and women.  相似文献   
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