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   2809篇
  免费   208篇
  国内免费   85篇
耳鼻咽喉   110篇
儿科学   83篇
妇产科学   26篇
基础医学   541篇
口腔科学   99篇
临床医学   347篇
内科学   574篇
皮肤病学   38篇
神经病学   232篇
特种医学   55篇
外科学   210篇
综合类   283篇
预防医学   351篇
眼科学   2篇
药学   90篇
  1篇
中国医学   29篇
肿瘤学   31篇
  2024年   7篇
  2023年   40篇
  2022年   115篇
  2021年   136篇
  2020年   107篇
  2019年   96篇
  2018年   104篇
  2017年   89篇
  2016年   90篇
  2015年   99篇
  2014年   124篇
  2013年   154篇
  2012年   114篇
  2011年   117篇
  2010年   103篇
  2009年   103篇
  2008年   118篇
  2007年   110篇
  2006年   103篇
  2005年   101篇
  2004年   85篇
  2003年   85篇
  2002年   63篇
  2001年   52篇
  2000年   80篇
  1999年   75篇
  1998年   56篇
  1997年   60篇
  1996年   46篇
  1995年   48篇
  1994年   41篇
  1993年   39篇
  1992年   42篇
  1991年   29篇
  1990年   29篇
  1989年   27篇
  1988年   34篇
  1987年   22篇
  1986年   22篇
  1985年   15篇
  1984年   12篇
  1983年   9篇
  1982年   19篇
  1981年   12篇
  1980年   12篇
  1979年   10篇
  1978年   15篇
  1977年   6篇
  1976年   14篇
  1975年   5篇
排序方式: 共有3102条查询结果,搜索用时 15 毫秒
81.
The extracellular mass/body cell mass ratio (ECM/BCM ratio) is a novel indicator of nutritional and hydration status in hemodialysis (HD) patients. This study aimed to explore the ECM/BCM ratio as a predictor of mortality risk with nutritional-inflammatory markers in HD patients. A prospective observational study was conducted in 90 HD patients (male: 52.2%; DM: 25.60%). Clinical and biochemical parameters [serum albumin, serum C-reactive protein (s-CRP), interleukine-6 (IL-6)] were analysed and bioelectrical impedance analysis (BIA) was performed. Protein-energy wasting syndrome (PEW) was diagnosed using malnutrition-inflammation score (MIS). Based on BIA-derived measurements, the ECM/BCM ratio with a cut-off point of 1.20 was used as a PEW-fluid overload indicator. Comorbidity by Charlson index and hospital admissions were measured. Out of 90 HD patients followed up for 36 months, 20 patients (22.22%) died. PEW was observed in 24 survivors (34.28%) and all non-survivors. The ECM/BCM ratio was directly correlated with MIS, s-CRP, Charlson index and hospital admissions but was negatively correlated with phase angle and s-albumin (all, p < 0.001). Values of the ECM/BCM ratio ≥ 1.20 were associated with higher probability of all-cause mortality (p = 0.002). The ECM/BCM ratio ≥ 1.20, IL-6 ≥ 3.1 pg/mL, s-CRP and s-albumin ≥ 3.8 g/dL and Charlson index were significantly associated with all-cause mortality risk in multivariate adjusted analysis. This study demonstrates that the ECM/BCM ratio ≥ 1.20 as a nutritional marker and/or fluid overload indicator had a significant prognostic value of death risk in HD patients.  相似文献   
82.
基于电阻抗成像的均质头模型研究   总被引:2,自引:0,他引:2  
目的 评估低电导率的颅骨对人脑阻抗成像的影响.方法 基于适用于头部的优化的硬件系统和反投影算法,在建立的一个圆筒形和一个半球形的包含"颅骨"的均质头模型上,对多种扰动目标进行成像研究.结果 现有系统对含均质"颇骨"的头部物理模型内电导率、位置和尺寸不同的简单扰动目标成功地进行了图像重建.结论 "颅骨"的存在对重构图像产生了显著的影响,揭示了脑电阻抗图像监护的可行性,为动物实验提供了依据.  相似文献   
83.
This study seeks prevent and alleviate the failure of magnesium alloy anodes in pipelines, which we suspect is a problem related to SRB. The electrochemical corrosion behaviour of two kinds of magnesium alloys, AZ31B and AZ63B, in 3.5 wt.% NaCl solution with sulphide or phosphide—the two main inorganic metabolites of sulphate-reducing bacteria—were studied by electrochemical tests combined with other characterisation methods such as scanning electron microscopy and X-ray diffraction. The results show that the corrosion film formed by inorganic metabolites of SRB’s initial stage of corrosion (1–3 d) can lead to the corrosion of magnesium alloys. However, the loose and porous corrosion product film cannot protect the substrate effectively. The inorganic metabolites in the solution can accelerate the corrosion of the surface of magnesium alloy after the corrosion products have fallen off. This study provides a theoretical basis for alleviating the premature failure of magnesium alloy anodes and for corrosion protection in the future.  相似文献   
84.
85.
Approximately 6.3 million fractures occur each year in the United States alone. Accurately monitoring the progression of fracture healing is essential to be able to advise patients when it is safe to return to normal activity. The most common method used to confirm and monitor fracture healing is the acquisition of multiple radiographic images over the many months required for healing. This imaging method uses large expensive equipment and exposes patients to high levels of ionizing radiation. In the study described here, we tested another technology for monitoring fracture healing that could minimize the need for multiple radiographic images. We tested a piezoelectric transducer fixed to the surface of a bone that uses electromechanical impedance spectroscopy to measure simulated fractures and transmits the measurement data to an acoustic receiver located externally on the skin surface.  相似文献   
86.
87.
88.
89.
90.
Blood samples from 33 dogs, 28 cats, 24 horses and 25 cattle were analysed in duplicate on the Coulter Counter S-Plus IV and the Baker 9000 multichannel haematology analysers. The precisions of each instrument and the correlations between the instruments were evaluated. The precisions of both systems were good but, the Baker 9000 system showed more variability between duplicate determinations for all parameters. The Baker 9000 had better precision for white blood cell count, haemoglobin concentration, and MCV. Correlations between the two instruments were excellent except for MCHC. Neither analyser reliably provided feline platelet counts and the Baker 9000 also failed to report error messages for 8 of 10 apparently false platelet counts. The Coulter instrument consistently reported higher haemoglobin concentrations and higher feline and lower canine white blood cell counts than the Baker 9000.  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