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   24440篇
  免费   1661篇
  国内免费   543篇
耳鼻咽喉   264篇
儿科学   550篇
妇产科学   470篇
基础医学   2811篇
口腔科学   399篇
临床医学   2860篇
内科学   2980篇
皮肤病学   220篇
神经病学   1618篇
特种医学   789篇
外国民族医学   3篇
外科学   1731篇
综合类   3681篇
现状与发展   6篇
预防医学   3143篇
眼科学   354篇
药学   2569篇
  32篇
中国医学   569篇
肿瘤学   1595篇
  2024年   73篇
  2023年   505篇
  2022年   903篇
  2021年   1222篇
  2020年   1181篇
  2019年   926篇
  2018年   896篇
  2017年   845篇
  2016年   975篇
  2015年   978篇
  2014年   2021篇
  2013年   1866篇
  2012年   1656篇
  2011年   1739篇
  2010年   1306篇
  2009年   1205篇
  2008年   1199篇
  2007年   1013篇
  2006年   867篇
  2005年   702篇
  2004年   589篇
  2003年   495篇
  2002年   439篇
  2001年   365篇
  2000年   291篇
  1999年   255篇
  1998年   226篇
  1997年   171篇
  1996年   159篇
  1995年   155篇
  1994年   151篇
  1993年   105篇
  1992年   120篇
  1991年   109篇
  1990年   96篇
  1989年   81篇
  1988年   94篇
  1987年   89篇
  1986年   46篇
  1985年   95篇
  1984年   82篇
  1983年   65篇
  1982年   53篇
  1981年   41篇
  1980年   47篇
  1979年   42篇
  1978年   20篇
  1976年   15篇
  1974年   11篇
  1972年   11篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
The efficacy of supravital staining in the detection of malignancies in oro and oropharyngeal lesions and its role in the detection of malignant changes in premalignant lesions were studied. This prospective study comprises 90 cases of clinically suspicious lesions and it was done over a period of 3 years. Most of the patients had multiple risk factors for the development of malignancy. All underwent staining with a modified solution of 1% toluidine blue (TB). In our study the overall sensitivity was 97.29% and the specificity was 62.5%.  相似文献   
82.
介绍了基于bq2050电池容量检测电路的设计,实测结果表明此电池容量检测电路设计合理,实用有效,且精度高、体积小、功耗低,适合生命探测仪使用。  相似文献   
83.
84.
The feedback concealed information test (fCIT) is a novel form of the CIT, providing participants with feedback regarding their memory concealment performance. The fCIT utilizes event‐related potentials (recognition‐P300 and feedback‐related event‐related potentials) and has been shown to provide high efficiency in detecting information concealment. However, it is unclear how well the fCIT performs in the presence of mental countermeasures. To address this question, participants were trained to use countermeasures during fCIT. Results showed that the recognition‐P300 efficiency decreased when participants used countermeasures. However, the efficiencies of feedback‐related negativity and feedback‐P300 were unchanged, with feedback‐P300 still showing a high detection efficiency (AUC = 0.86) during countermeasures. These findings demonstrate the potential of fCIT for subverting countermeasures.  相似文献   
85.
Previous studies have demonstrated a frequent occurrence of screw/K-wire malpositioning during surgical fracture treatment under 2D fluoroscopy and a correspondingly high revision rate as a result of using intraoperative 3D imaging. In order to facilitate and accelerate the diagnosis of implant malpositioning in 3D data sets, this study investigates two versions of an implant detection software for mobile 3D C-arms in terms of their detection performance based on comparison with manual evaluation. The 3D data sets of patients who had received surgical fracture treatment at five anatomical regions were extracted from the research database. First, manual evaluation of the data sets was performed, and the number of implanted implants was assessed. For 25 data sets, the time required by four investigators to adjust each implant was monitored. Subsequently, the evaluation was performed using both software versions based on the following detection parameters: true-positive-rate, false-negative-rate, false-detection-rate and positive predictive value. Furthermore, the causes of false positive and false negative detected implants depending on the anatomical region were investigated. Two hundred fourteen data sets with overall 1767 implants were included. The detection parameters were significantly improved (p<.001) from version 1 to version 2 of the implant detection software. Automatic evaluation required an average of 4.1±0.4 s while manual evaluation was completed in 136.15±72.9 s (p<.001), with a statistically significant difference between experienced and inexperienced users (p=.005). In summary, version 2 of the implant detection software achieved significantly better results. The time saved by using the software could contribute to optimizing the intraoperative workflow.  相似文献   
86.
局部脑组织氧饱和度(regional cerebral oxygenation,rSO2)监测的应用范围很广,不受温度和搏动血流影响,是一种监测脑组织氧合状态的新方式,但目前在新生儿方面的研究较少.本文针对不同病理状况对新生儿生后早期rSO2的影响进行综述,阐明新生儿rSO2监测的重要临床意义并对其未来应用范围进行展望.  相似文献   
87.
88.
Objective: To evaluate prospectively the incidence of early pregnancy losses (before menstruation occurs) in IVF and ovum donation cycles.

Design: Prospective case-control study.

Setting: Tertiary care, university-associated center.

Patient(s): One hundred forty-five patients undergoing IVF and 92 undergoing oocyte donation were recruited. The control group for IVF consisted of 15 ovum donors who had no ET and were instructed to avoid intercourse. The control group for oocyte donation included 10 women undergoing a mock cycle of steroid replacement.

Intervention(s): Starting on day 6 after ET, the women were instructed to collect the first urine sample of the day every 2 days. Each patient collected six different specimens of urine (days 6, 8, 10, 12, 14, and 16 after ET for cases or the same days without ET for controls.

Main Outcome Measure(s): β-HCG was measured with a standardized microparticle enzyme immunoassay, and IVF reproductive outcome was assessed.

Result(s): For IVF, positive implantation was registered in 88 of 145 cycles of embryo replacement (60.7%). Only 30 (20.7%) resulted in viable pregnancies, whereas the remaining 58 miscarried. Forty-two of these miscarriages (72.4%) were early pregnancy losses and 13 (22.4%) were classified as clinical abortions. In ovum donation, positive implantation was recorded in 64 of 92 cycles of ET (69.6%). A total of 30 (32.6%) ended in viable pregnancies, whereas the remaining 34 (37.0%) were miscarriages. Early pregnancy loss accounted for 70.6% of pregnancy losses, whereas biochemical pregnancies and clinical abortions accounted for 11.8% and 17.6%, respectively.

Conclusion(s): Our results demonstrate that patients undergoing assisted reproductive technology have an increased rate of early pregnancy loss compared with fertile patients. In addition, these data indicate that implantation is more frequently impaired in IVF than in oocyte donation cycles, resulting in a high incidence of early pregnancy loss. This suggests that implantation may be subjected to abnormal conditions in assisted reproduction.  相似文献   

89.
炔诺酮肟对大鼠抗着床抗早孕作用机理的形态学研究   总被引:1,自引:0,他引:1  
大鼠从妊娠第一天开始每日灌服炔诺酮肟4mg/kg,共3天。结果能引起早孕大鼠黄体细胞滑面内质网减少;脂滴大量积贮;抑制卵巢3β-羟基甾体脱氢酶活性,从而使卵巢孕酮生物合成受阻。药物还能引起早孕大鼠子宫蜕膜的病理改变,蜕膜细胞出现变性,坏死,宫腔内大量出血,白细胞浸润,胚胎发育不良,蜕膜细胞内糖原及碱性磷酸酶含量均下降。本文还讨论了药物引起卵巢孕酮生物合成受阻与蜕膜变化的关系。  相似文献   
90.
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