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   2886篇
  免费   190篇
  国内免费   16篇
耳鼻咽喉   10篇
儿科学   113篇
妇产科学   42篇
基础医学   530篇
口腔科学   77篇
临床医学   202篇
内科学   673篇
皮肤病学   95篇
神经病学   193篇
特种医学   66篇
外科学   295篇
综合类   9篇
预防医学   198篇
眼科学   68篇
药学   226篇
中国医学   14篇
肿瘤学   281篇
  2023年   26篇
  2022年   38篇
  2021年   74篇
  2020年   46篇
  2019年   64篇
  2018年   65篇
  2017年   71篇
  2016年   74篇
  2015年   79篇
  2014年   80篇
  2013年   120篇
  2012年   184篇
  2011年   200篇
  2010年   115篇
  2009年   125篇
  2008年   187篇
  2007年   184篇
  2006年   217篇
  2005年   196篇
  2004年   189篇
  2003年   146篇
  2002年   152篇
  2001年   23篇
  2000年   16篇
  1999年   35篇
  1998年   36篇
  1997年   23篇
  1996年   18篇
  1995年   22篇
  1994年   24篇
  1993年   24篇
  1992年   21篇
  1991年   23篇
  1990年   21篇
  1989年   16篇
  1988年   11篇
  1987年   21篇
  1986年   15篇
  1985年   19篇
  1984年   11篇
  1983年   9篇
  1982年   9篇
  1981年   7篇
  1980年   9篇
  1978年   8篇
  1977年   4篇
  1976年   3篇
  1974年   8篇
  1973年   4篇
  1971年   3篇
排序方式: 共有3092条查询结果,搜索用时 47 毫秒
71.
BackgroundAtopic dermatitis (AD) is a chronic inflammatory skin disease that affects 20% of children worldwide. Environmental factors including weather and air pollutants have been shown to be associated with AD symptoms. However, the time‐dependent nature of such a relationship has not been adequately investigated. This paper aims to assess whether real‐time data on weather and air pollutants can make short‐term prediction of AD severity scores.MethodsUsing longitudinal data from a published panel study of 177 paediatric patients followed up daily for 17 months, we developed a statistical machine learning model to predict daily AD severity scores for individual study participants. Exposures consisted of daily meteorological variables and concentrations of air pollutants, and outcomes were daily recordings of scores for six AD signs. We developed a mixed‐effect autoregressive ordinal logistic regression model, validated it in a forward‐chaining setting and evaluated the effects of the environmental factors on the predictive performance.ResultsOur model successfully made daily prediction of the AD severity scores, and the predictive performance was not improved by the addition of measured environmental factors. Potential short‐term influence of environmental exposures on daily AD severity scores was outweighed by the underlying persistence of preceding scores.ConclusionsOur data does not offer enough evidence to support a claim that weather or air pollutants can make short‐term prediction of AD signs. Inferences about the magnitude of the effect of environmental factors on AD severity scores require consideration of their time‐dependent dynamic nature.  相似文献   
72.
73.
This study describes a novel technique for skeletonization and isolation of Glissonean and venous branches during liver surgery using a harmonic scalpel (HS). Hepatic resections with HS were performed with the skeletonization and isolation technique in 50 patients (HS group). Variables evaluated were blood loss, operative time, biliary leak, and morbidity. The results were compared with 50 hepatic resections that were performed using a previously established technique: Cavitron ultrasonic surgical aspirator with electric cautery, ligatures, and hemoclips (NHS group). The HS group had shorter total operative times (285 versus 358 minutes; P = 0.01), less blood loss (389 versus 871 mL; P = 0.034), and less crystalloid infusion (2744 versus 3299 mL; P = 0.027) compared with the NHS group. Postoperative liver function and complication rates were similar when comparing the two groups. These data demonstrate that HS is a simple, easy, and effective instrument for the skeletonization and isolation of vessels during liver transection.Key words: Liver resection, Ultrasonic scalpel, Skeletonization, Cavitation effectVarious devices are available for liver transection, but the availability of comparative data for transection techniques is limited by the diversity of operative procedures. Clamp crushing (CC) and a Cavitron ultrasonic surgical aspirator are widely used for splitting the liver parenchyma,1,2 and hemostasis is achieved by bipolar coagulation, ligatures, or hemoclips. Various coagulating devices, such as Ligasure,3 Tissuelink,4 and the Harmonic Scalpel (HS),57 have recently been developed to aid in liver splitting. The choice of instrument is often based on individual surgeon preference. Higami et al8,9 described a novel technique to skeletonize and harvest the internal thoracic artery with the HS, and the present study capitalizes on their experience to describe a unique method to skeletonize and isolate the Glissonean and venous branches using an HS.  相似文献   
74.
75.
We report on molecular and clinical findings in 10 Japanese patients (four males and six females) from eight families (two pairs of siblings and six isolated cases) with Antley-Bixler syndrome accompanied by abnormal genitalia and/or impaired steroidogenesis. Direct sequencing was performed for all the 15 exons of cytochrome P450 oxidoreductase gene (POR), showing two missense mutations (R457H and Y578C), a 24-bp deletion mutation resulting in loss of nine amino acids and creation of one amino acid (L612_W620delinsR), a single bp insertion mutation leading to frameshift (I444fsX449), and a silent mutation (G5G). R457H has previously been shown to be a pathologic mutation, and computerized modeling analyses indicated that the 15A>G for G5G could disturb an exonic splicing enhancer motif, and the remaining three mutations should affect protein conformations. Six patients were compound heterozygotes, and three patients were R457H homozygotes; no mutation was identified on one allele of the remaining one patient. Clinical findings included various degrees of skeletal features, such as brachycephaly, radiohumeral synostosis, and digital joint contractures in patients of both sexes, normal-to-poor masculinization during fetal and pubertal periods in male patients, virilization during fetal life and poor pubertal development without worsening of virilization in female patients, and relatively large height gain and delayed bone age from the pubertal period in patients of both sexes, together with maternal virilization during pregnancy. Blood cholesterol was grossly normal, and endocrine studies revealed defective CYP17A1 and CYP21A2 activities. The results suggest that Antley-Bixler syndrome with abnormal genitalia and/or impaired steroidogenesis is caused by POR mutations, and that clinical features are variable and primarily explained by impaired activities of POR-dependent CYP51A1, CYP17A1, CYP21A2, and CYP19A1.  相似文献   
76.
Background Seasonality characterizing influenza epidemics suggests susceptibility to climate variation. El Niño southern oscillation (ENSO), which involves two extreme events, El Niño and La Niña, is well‐known for its large effects on inter‐annual climate variability. The influence of ENSO on several diseases has been described. Objectives In this study, we attempt to analyze the possible influence of ENSO on the timing of the annual influenza activity peak using influenza‐like illness report data in Japan during 1983–2007. Materials Influenza surveillance data for 25 influenza epidemics, available under the National Epidemiological Surveillance of the Infectious Diseases, was used in this study. ENSO data were obtained from the Japan Meteorological Agency. Results Influenza‐like illness peak week varied largely during the study period, ranging between 4th and 11th weeks (middle of winter to early spring). The average of peak week during ENSO cycles (n = 11, average = 4·5 ± 0·9) was significantly earlier than in non‐ENSO years (n = 14, average = 7·6 ± 2·9; P = 0·01), but there was no significant difference in the peak timing between hot (El Niño) and cold (La Niña) phases. Earlier peaks of influenza activity were observed in 16, out of 25, epidemics. These coincided with 10 (90·9%) out of 11 ENSO and 6 (85·7%) out of seven large‐scale epidemics. Conclusion Influenza activity peak occurred earlier in years associated with ENSO and/or large scale epidemics.  相似文献   
77.
OBJECTIVES: To assess the myocardium-reperfusing effect of a distal protection device, GuardWire Plus (GuardWire Plus), in patients with acute myocardial infarction (AMI). BACKGROUND: Distal embolization may result in reduced myocardial perfusion, increasing the risk of non-Q-wave myocardial infarction and death. Distal protection devices may protect the microcirculation from embolic debris, improving short- and long-term clinical outcomes. METHODS: From February 2002 to July 2003, a total of 341 AMI patients at 22 institutions in Japan were enrolled in the present, multicenter, prospective, randomized trial. Patients experiencing AMI within 12 hr of symptom onset, who were considered treatable by stenting and who met the inclusion criteria, were eligible for randomization. Stenting with and without GuardWire Plus was conducted to examine whether the device provides faster and more complete ST-segment resolution, smaller infarct size, and improved myocardial blush score. RESULTS: The rates of slow flow and no-reflow immediately after PCI were 5.3 and 11.4% in the GuardWire Plus and control groups, respectively (P = 0.05). Blush score 3 acquisition rates immediately after PCI were 25.2 and 20.3% in the GuardWire Plus and control groups, respectively (P = 0.26), and the rates at 30 days after PCI were 42.9 and 30.4%, respectively (P = 0.035). CONCLUSIONS: A significant difference was found between the GuardWire Plus and control groups with respect to the total incidence of distal embolization, indicating that GuardWire Plus angiographically improved myocardial perfusion without demonstrating the preventive effect of myocardial damage.  相似文献   
78.
79.
80.
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