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   752篇
  免费   38篇
  国内免费   14篇
耳鼻咽喉   11篇
儿科学   34篇
妇产科学   26篇
基础医学   59篇
口腔科学   35篇
临床医学   49篇
内科学   137篇
皮肤病学   23篇
神经病学   33篇
特种医学   147篇
外科学   123篇
综合类   25篇
预防医学   24篇
眼科学   13篇
药学   34篇
肿瘤学   31篇
  2022年   3篇
  2021年   8篇
  2020年   3篇
  2019年   5篇
  2018年   12篇
  2017年   7篇
  2016年   9篇
  2015年   22篇
  2014年   16篇
  2013年   29篇
  2012年   23篇
  2011年   29篇
  2010年   35篇
  2009年   35篇
  2008年   26篇
  2007年   53篇
  2006年   49篇
  2005年   46篇
  2004年   36篇
  2003年   23篇
  2002年   18篇
  2001年   34篇
  2000年   11篇
  1999年   3篇
  1998年   23篇
  1997年   37篇
  1996年   21篇
  1995年   23篇
  1994年   16篇
  1993年   6篇
  1992年   6篇
  1991年   3篇
  1990年   8篇
  1989年   14篇
  1988年   9篇
  1987年   15篇
  1986年   9篇
  1985年   10篇
  1984年   5篇
  1983年   9篇
  1982年   7篇
  1981年   10篇
  1980年   12篇
  1979年   1篇
  1978年   4篇
  1977年   7篇
  1976年   8篇
  1975年   5篇
  1974年   1篇
排序方式: 共有804条查询结果,搜索用时 156 毫秒
81.
Ohne Zusammenfassung  相似文献   
82.
Abstrakt 1. Hinsichtlich der Frage der Anerkennung einer Heilmethode kommt es nicht darauf an, ob eine Methode von der überwiegenden Mehrheit der sogenannten Schulmediziner anerkannt wird, aber auch nicht, ob die betreffende Methode „therapieimmanent“, also von denjenigen, die diese Methode entwickelt haben oder sie anwenden, als wirksam eingesch?tzt wird. Entscheidend ist vielmehr auf die Anerkennung derjenigen Personen abzustellen, die sich von dritter Seite als Wissenschaftler in einem wissenschaftlichen Verfahren mit der Frage der Wirksamkeit der betreffenden Methode auseinandergesetzt haben. 2. Der Wirkmechanismus der Bioresonanztherapie ist nach strengen naturwissenschaftlichen Untersuchungen nicht zu erkl?ren. Diese Methode ist jedoch von der Hufelandgesellschaft, die sich aus 25 ?rztegesellschaften zusammensetzt, die allesamt auch Naturheilverfahren betreiben, anerkannt. (Leits?tze des Bearbeiters)  相似文献   
83.
84.
痢止蒿化学成分的研究   总被引:3,自引:0,他引:3  
王爱国  吕扬  冯孝章 《药学学报》1994,29(12):899-904
自云南产痢止蒿(Ajuga forrestii Diels)全草的乙醇提取物中分得5个单体,其中化合物Ⅰ和Ⅱ经波谱分析和化学方法鉴定为新的松香烷型二萜类化合物,分别命名为痢止蒿甲素(ajuforrestin A,I)和痢止蒿乙素(ajuforrestin B,II),其余3个是黄酮类化合物:洋芹素(apigenin)、金合欢素(acacetin)和买麻藤乙素(gnetifolin B)。  相似文献   
85.
86.
87.
Quadricuspid aortic valve is a rare congenital malformation of the aortic valve. Most cases are discovered incidentally at autopsy or at aortic valve replacement. Recent advances in echocardiography epecially transesophageal echocardiography led to diagnosis of more cases before surgery. Two cases of quadricuspid aortic valve are presented.  相似文献   
88.
Fairbanks  VF; Nepo  AG; Beutler  E; Dickson  ER; Honig  G 《Blood》1980,55(2):216-220
Two large and unrelated families were investigated for hereditary nonspherocytic hemolytic anemia associated with deficiency of erythrocyte glucose-6-phosphate dehydrogenase (G6PD). In both families, the kinetic and electrophoretic features of the G6PD variants resembled those of G6PD Chicago. Further investigation revealed that members of one of these families previously had been characterized as having the G6PD variants Chicago and Cornell. However, it is clear that each of these terms has been applied to the same variant in this single large kindred. In the second family, we describe a newly identified variant with unique characteristics, which we have designated G6PD Pea Ridge. G6PD Pea Ridge resembles G6PD Chicago but differs in electrophoretic mobility and in a few kinetic parameters. It exhibits an unusually high Ki for NADPH and thus appears to be insensitive to product inhibition. As other cases previously considered to be the Chicago variant become more fully characterized, this probably will be shown to be a heterogeneous group of variants.  相似文献   
89.
In this work, a pioneering study on the electrical properties of composite carbon nanofibres (CNFs) using current-sensitive atomic force microscopy (CS-AFM) has been demonstrated. CNFs are highly interesting materials which are usable in a wide array of applications e.g. electrode materials for biosensors, lithium ion batteries, fuel cells and supercapacitors. CNFs offer a high specific surface area and thus have a high contact area for charge transfer. CNFs can be produced using spinnable polyacrylonitrile (PAN) as a precursor for carbonisation. For the purpose of developing efficient CNFs with high conductivity and power density, silver nanoparticle (AgNPs)-containing PAN solutions were electrospun to form composite nanofibres which was followed by heat treatment. The applied voltage of the spinning setup and the content of both PAN and the silver nanoparticles in the spinning solution were varied in order to study their influence on the morphology and the electrical properties of the nanofibres. The resultant morphologies and fibre diameters were determined by scanning electron microscopy (SEM). The formation of silver nanoparticles was characterised in solution by UV-visible absorption spectroscopy and dynamic light scattering (DLS), while energy-dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM) were carried out to investigate the presence as well as the average diameter of the AgNPs. The electrical properties of the CNFs were investigated using CS-AFM. This technique gives us the possibility to explore the electrical properties of single fibers and hence derive relationships between the structural features and the electrical properties. Our results show that the composite CNFs have a higher electrical conductivity than the neat CNFs and both the average diameter of the fibers and the electrical conductivity increase with an increasing AgNP content.

In this work, a pioneering study on the electrical properties of composite carbon nanofibres (CNFs) using current-sensitive atomic force microscopy (CS-AFM) has been demonstrated.  相似文献   
90.
Objectives The purpose of this study was to investigate coronary blood flow properties in patients with diffuse coronary artery ectasia (CAE) associated with exercise-induced myocardial ischemia.Methods Seventeen patients with diffuse CAE and without coexisting coronary artery stenosis were enrolled in the study (CAE group). CAE was defined as luminal dilatation 1.5 to 2 times that of the adjacent normal coronary artery segment or the diameter of the corresponding coronary artery of the control group when there was no normal segment. The age- and sex-matched control group (n = 20) comprised patients with normal epicardial coronary arteries. Coronary blood flow velocities were obtained invasively by use of Doppler scanning flow wire. Coronary flow reserve (CFR) was measured by administration of intracoronary papaverine as the hyperemic stimulus. Volumetric coronary blood flow was estimated by multiplying the velocity time integral of coronary blood flow with the cross-sectional area of the coronary artery and the heart rate.Results Fifteen patients with CAE, but none of the patients in the control group, had electrocardiographic signs of myocardial ischemia at peak exercise on ergometry. Baseline average peak velocities (APVs) of coronary blood flow were similar in the 2 groups. Peak hyperemic APVs of coronary blood flow were lower in the CAE group than in the control group (17.5 ± 7.4 cm/s vs 41.5 ± 12.6 cm/s, respectively, P < .001). Volumetric coronary blood flow was significantly higher in the CAE group than in the control group, both at rest and at hyperemia (146.3 ± 71.2 cm3/min vs 45.1 ± 16.1 cm3/min, respectively, P < .001, and 202 ± 87.3 cm3/min vs 104.1 ± 37.6 cm3/min, respectively, P < .003). The mean CFR of the CAE group was significantly reduced compared with that of the control group (1.51 ± 0.31 vs 2.67 ± 0.52, respectively, P < .001).Conclusions The CFR is significantly reduced in patients with diffuse CAE compared to a matched control group. Although volumetric coronary blood flow is significantly higher in CAE, microcirculatory dysfunction that is reflected as depressed CFR may be the underlying cause of exercise-induced myocardial ischemia. (Am Heart J 2003;145:66-72.)  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