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   6384篇
  免费   566篇
  国内免费   185篇
耳鼻咽喉   87篇
儿科学   132篇
妇产科学   53篇
基础医学   519篇
口腔科学   809篇
临床医学   506篇
内科学   564篇
皮肤病学   33篇
神经病学   710篇
特种医学   401篇
外科学   1266篇
综合类   722篇
现状与发展   2篇
预防医学   168篇
眼科学   63篇
药学   485篇
  3篇
中国医学   329篇
肿瘤学   283篇
  2024年   17篇
  2023年   142篇
  2022年   156篇
  2021年   267篇
  2020年   290篇
  2019年   286篇
  2018年   255篇
  2017年   252篇
  2016年   234篇
  2015年   208篇
  2014年   407篇
  2013年   467篇
  2012年   346篇
  2011年   366篇
  2010年   301篇
  2009年   287篇
  2008年   279篇
  2007年   260篇
  2006年   256篇
  2005年   213篇
  2004年   180篇
  2003年   156篇
  2002年   165篇
  2001年   133篇
  2000年   108篇
  1999年   90篇
  1998年   85篇
  1997年   95篇
  1996年   65篇
  1995年   78篇
  1994年   67篇
  1993年   65篇
  1992年   60篇
  1991年   64篇
  1990年   45篇
  1989年   48篇
  1988年   49篇
  1987年   24篇
  1986年   31篇
  1985年   26篇
  1984年   47篇
  1983年   18篇
  1982年   27篇
  1981年   31篇
  1980年   16篇
  1979年   22篇
  1978年   21篇
  1977年   13篇
  1976年   8篇
  1972年   3篇
排序方式: 共有7135条查询结果,搜索用时 62 毫秒
31.
《Clinical neurophysiology》2019,130(12):2231-2237
ObjectiveThe clinical and neurophysiological characteristics of myoclonus in Angelman syndrome (AS) have been evaluated in single case or small cohorts, with contrasting results. We evaluated the features of myoclonus in a wide cohort of AS patients.MethodsWe performed polygraphic EEG-EMG recording in 24 patients with genetically confirmed AS and myoclonus. Neurophysiological investigations included jerk-locked back-averaging (JLBA), cortico-muscular coherence (CMC) and generalised partial directed coherence (GPDC). CMC and GPDC analyses were compared to those obtained from 10 healthy controls (HC).ResultsTwenty-four patients (aged 3–35 years, median 20) were evaluated. Sequences of quasi-continuous rhythmic jerks mostly occurred at alpha frequency or just below (mean 8.4 ± 1.4 Hz), without EEG correlate. JLBA did not show any clear transient preceding the jerks. CMC showed bilateral over-threshold CMC in alpha band that was prominent on the contralateral hemisphere in the patient group as compared to HC group. GPDC showed a significantly higher alpha outflow from both hemispheres toward activated muscles in the patient group, and a significantly higher beta outflow from contralateral hemisphere in the HC group.ConclusionsThese neurophysiological findings suggest a subcortical generator of myoclonus in AS.SignificanceMyoclonus in AS has not a cortical origin as previously hypothesised.  相似文献   
32.
BackgroundDiagnostic coagulation testing is vulnerable to factors of the pre-analytical phase such as sample centrifugation. Despite this, centrifugation conditions differ widely among European laboratories. Here we use samples from patients referred for Activated partial thromboplastin time (APTT) testing to investigate if different centrifugation conditions result in platelet-poor plasma (PPP) (plasma platelet count < 10 × 109/L) and how the variation in centrifugation conditions affect APTT measurements.MethodsCentrifugation of 2000g (10 min) were compared with 3000g (10 min) using samples from patients referred for APTT testing (n = 70). Plasma platelet count and APTT were measured to investigate the influence of the centrifugation conditions. Differences were evaluated using Bland Altman Plots and Student’s t-test.ResultsCentrifugation at 3000g for 10 min produced PPP for more of the samples (64%) than centrifugation at 2000g (6%) (p < 0.001). No statistically significant difference for APTT (p = 0.265) was found for samples with APTT < 37 s while samples with prolonged APTT (>37 s) showed a statistically significant difference (p = 0.025). The Bland Altman plot did not reveal a clinically significant difference (mean difference 0.30 s/0.68%) when compared to a maximum acceptable bias of 10%.ConclusionNone of the centrifugation conditions used in this study adequately secured PPP for all samples. Despite a statistically significant difference between samples with prolonged APTT, no clinically significant difference was observed when comparing all APTT measurements.  相似文献   
33.
摘 要 目的:探讨黄芪汤加减治疗慢性阻塞性肺疾病急性加重期(AECOPD)的临床疗效。方法:采用随机数字表法将166例AECOPD患者随机分为常规组和观察组各83例。常规组采用常规西医方法治疗,观察组在常规组的基础上给予黄芪汤加减治疗。观察两组治疗前后第1秒用力呼气量(FEV1)、用力肺活量(FVC)、FEV1占FVC的百分比(FEV1/FVC%)、动脉血氧分压(PaO2)、动脉血二氧化碳分压(PaCO2)、肿瘤坏死因子 α(TNF α)、白细胞介素 1β(IL 1β)、白细胞介素 6(IL 6)水平。结果:两组治疗后FEV1、FEV1/FVC、PaO2水平与治疗前相比较均显著升高(P<0.05),且观察组与同期常规组相比较均显著升高(P<0.05);两组治疗后PaCO2、TNF α、IL 1β、IL 6水平与治疗前相比较均显著降低(P<0.05),且观察组与同期常规组相比较均显著降低(P<0.05)。结论:黄芪汤加减治疗AECOPD可降低患者炎症反应水平,改善动脉血气和肺功能,提高治疗效果,值得临床应用。  相似文献   
34.
35.
36.
经典名方泽泻汤的HPLC指纹图谱及多指标含量测定研究   总被引:2,自引:0,他引:2  
目的建立经典名方泽泻汤的HPLC指纹图谱,结合化学模式识别技术对其进行分析,并测定泽泻汤中3种成分23-乙酰泽泻醇B、23-乙酰泽泻醇C和白术内酯Ⅲ的含量,为泽泻汤质量控制提供科学依据。方法采用Waters WAT054275C18色谱柱(250 mm×4.6 mm,5μm),以乙腈-水为流动相进行梯度洗脱,建立15批泽泻汤的HPLC指纹图谱,并采用"中药色谱指纹图谱相似度评价系统"、SPSS22.0及SIMCA14.1软件对15批泽泻汤的HPLC指纹图谱进行相似度评价及聚类分析(CA)、偏最小二乘判别分析(PLS-DA)等化学模式识别。同时测定23-乙酰泽泻醇B、23-乙酰泽泻醇C和白术内酯Ⅲ的含量。结果建立了15批泽泻汤的HPLC指纹图谱,相似度均0.94,标定了18个共有峰,指认出3个色谱峰,分别为11号峰白术内酯Ⅲ、15号峰23-乙酰泽泻醇C、16号峰23-乙酰泽泻醇B,CA和PLS-DA将15批泽泻汤样品分为2类,同时15批泽泻汤中23-乙酰泽泻醇B、23-乙酰泽泻醇C和白术内酯Ⅲ的质量分数分别为0.321~0.569、0.075~0.139、0.106~0.142 mg/g。结论 HPLC指纹图谱结合多成分同时测定的方法,快速、简便、重复性好,为泽泻汤及其制剂的质量评价提供参考。  相似文献   
37.
The role of fast activity as a potential biomarker in localization of the epileptogenic zone (EZ) remains controversial due to recently reported unsatisfactory performance. We recently identified a “fingerprint” of the EZ as a time‐frequency pattern that is defined by a combination of preictal spike(s), fast oscillatory activity, and concurrent suppression of lower frequencies. Here we examine the generalizability of the fingerprint in application to an independent series of patients (11 seizure‐free and 13 non‐seizure‐free after surgery) and show that the fingerprint can also be identified in seizures with lower frequency (such as beta) oscillatory activity. In the seizure‐free group, only 5 of 47 identified EZ contacts were outside the resection. In contrast, in the non‐seizure‐free group, 104 of 142 identified EZ contacts were outside the resection. We integrated the fingerprint prediction with the subject's MR images, thus providing individualized anatomical estimates of the EZ. We show that these fingerprint‐based estimates in seizure‐free patients are almost always inside the resection. On the other hand, for a large fraction of the nonseizure‐free patients the estimated EZ was not well localized and was partially or completely outside the resection, which may explain surgical failure in such cases. We also show that when mapping fast activity alone onto MR images, the EZ was often over‐estimated, indicating a reduced discriminative ability for fast activity relative to the full fingerprint for localization of the EZ.  相似文献   
38.
Introduction:Subchromosomal deletions and duplications could currently be detected by noninvasive preliminary screening (NIPS). However, NIPS is a screening test that requires further diagnosis. Here we report a fetus with an autosomal abnormality revealed by NIPS and conventional karyotype combined with copy number variations sequencing (CNV-seq) confirmed the fetus with an unbalanced translocation.Patient concern:This was the fourth pregnancy of a 30-year-old woman who underwent 2 spontaneous abortions and gave birth to a child with a normal phenotype. The woman and her husband were healthy and nonconsanguineous. NIPS indicated a repeat of about 19-Mb fragment at the region of 16q22.1-q22.4 at 17-week gestation.Diagnoses:The combination of traditional karyotype and CNV-seq could better locate the abnormal chromosomal region and further identify the source of fetal chromosomal abnormalities. Simultaneously, we evaluated the fetal morphology by ultrasound examination. The karyotype of the fetus was 46,XX,der(7)t(7;16)(p22;q23) and CNV-seq results showed an approximately 20.96-Mb duplication in 16q22.1-q24.3 (69200001-90160000) and an approximately 3.86-Mb deletion in 7p22.3-p22.2 (40001-3900000). Prenatal ultrasound revealed the fetal micrognathia. The paternal karyotype was 46,XY, t (7;16) (p22;q23), while the maternal was normal. The fetus inherited an abnormal chromosome 7 from its father.Interventions:No treatment for the fetus.Outcomes:Pregnancy was terminated.Conclusions:To our knowledge, the occurrence of de novo partial trisomy 16q (16q22.1-qter) and partial monosomy 7p (7p22.2-pter) has not previously been reported up to now. Here, we present the perinatal findings of such a case and a review of the literatures. CNV-seq combined with karyotype is a useful tool for chromosomal abnormalities indicated by NIPS.  相似文献   
39.
40.
The purpose of this study was to compare the complications of patients treated for a benign parotid tumour (BPT) by extracapsular dissection (ECD) vs. partial superficial parotidectomy (PSP). A comprehensive literature investigation was conducted by searching electronic databases. A systematic review and meta-analysis of comparative studies were performed to assess ECD and PSP for the treatment of BPTs with fixed-effects models. The outcomes analysed were transient or permanent facial nerve injury, Frey syndrome, recurrence rate, infection, and salivary fistula/sialocele. A total of 1641 patients from seven studies (1120 ECD-treated and 521 PSP-treated patients) were included in this meta-analysis. Transient facial nerve injury (odds ratio (OR) = 0.28, 95% confidence interval (CI): 0.11–0.71; p = 0.008) and Frey syndrome (OR = 0.12, 95% CI: 0.03–0.48; p = 0.003) were less prevalent in the ECD group. The rates of permanent facial nerve injury (OR = 0.77, 95% CI: 0.35–1.70; p = 0.520), recurrence rate (OR = 0.17, 95% CI: 0.02–1.75; p = 0.14), infection (OR = 0.70, 95% CI: 0.07–6.67; p = 0.76), and salivary fistula/sialocele (OR = 0.40, 95% CI: 0.06–2.66; p = 0.350) were similar in both groups. Although there was a trend that ECD showed a reduced risk for complications, the present results are not sufficient to conclude that ECD is more beneficial than PSP.  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