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   747篇
  免费   45篇
  国内免费   7篇
耳鼻咽喉   3篇
儿科学   30篇
妇产科学   3篇
基础医学   62篇
口腔科学   40篇
临床医学   60篇
内科学   242篇
皮肤病学   8篇
神经病学   38篇
特种医学   65篇
外科学   74篇
综合类   34篇
预防医学   50篇
药学   24篇
中国医学   4篇
肿瘤学   62篇
  2023年   5篇
  2022年   6篇
  2021年   18篇
  2020年   9篇
  2019年   13篇
  2018年   14篇
  2017年   6篇
  2016年   13篇
  2015年   19篇
  2014年   29篇
  2013年   43篇
  2012年   40篇
  2011年   42篇
  2010年   41篇
  2009年   23篇
  2008年   31篇
  2007年   32篇
  2006年   31篇
  2005年   22篇
  2004年   41篇
  2003年   24篇
  2002年   10篇
  2001年   15篇
  2000年   15篇
  1999年   9篇
  1998年   25篇
  1997年   15篇
  1996年   22篇
  1995年   8篇
  1994年   16篇
  1993年   12篇
  1992年   12篇
  1991年   14篇
  1990年   7篇
  1989年   11篇
  1988年   14篇
  1987年   19篇
  1986年   12篇
  1985年   8篇
  1984年   8篇
  1983年   4篇
  1982年   9篇
  1981年   3篇
  1980年   6篇
  1979年   3篇
  1977年   3篇
  1976年   7篇
  1975年   2篇
  1972年   2篇
  1971年   3篇
排序方式: 共有799条查询结果,搜索用时 15 毫秒
41.
42.
BACKGROUND: The sex differential in coronary heart disease (CHD) risk, which is not explained by male/female differences in lipid and lipoprotein concentrations, narrows with age. We examined whether this differential CHD risk might, in part, be attributable to the sizes of lipoprotein particles or concentrations of lipoprotein subclasses. METHODS: We analyzed frozen plasma samples from 1574 men and 1692 women from exam cycle 4 (1988-1990) of the Framingham Offspring Study. Nuclear magnetic resonance (NMR) spectroscopy was used to determine the subclass concentrations and mean sizes of VLDL, LDL, and HDL particles. Concentrations of lipids and apolipoproteins were measured by standard chemical methods. RESULTS: In addition to the expected sex differences in concentrations of triglycerides, LDL-cholesterol, and HDL-cholesterol, women also had a lower-risk subclass profile consisting of larger LDL (0.4 nm) and HDL (0.5 nm) particles. The sex difference was most pronounced for HDL, with women having a twofold higher (8 vs 4 micromol/L) concentration of large HDL particles than men. Furthermore, similar to the narrowing of the sex difference in CHD risk with age, the observed male/female difference in HDL particle size also decreased with age. Although lipoprotein particle sizes were highly correlated with lipid and lipoprotein concentrations, the sex differences in the mean sizes of lipoprotein particles persisted (P <0.001) even after adjustment for lipid and lipoprotein concentrations. CONCLUSIONS: Women have a less atherogenic subclass profile than men, even after accounting for differences in lipid concentrations.  相似文献   
43.
44.
45.
46.
OBJECTIVE: To demonstrate that employees can gain understanding of the financial constraints involved in designing health insurance benefits. BACKGROUND: While employees who receive their health insurance through the workplace have much at stake as the cost of health insurance rises, they are not necessarily prepared to constructively participate in prioritizing their health insurance benefits in order to limit cost. DESIGN: Structured group exercises. SETTING AND PARTICIPANTS: Employees of 41 public and private organizations in Northern California. INTERVENTION: Administration of the CHAT (Choosing Healthplans All Together) exercise in which participants engage in deliberation to design health insurance benefits under financial constraints. MAIN OUTCOME MEASURES: Change in priorities and attitudes about the need to exercise insurance cost constraints. RESULTS: Participants (N = 744) became significantly more cognizant of the need to limit insurance benefits for the sake of affordability and capable of prioritizing benefit options. Those agreeing that it is reasonable to limit health insurance coverage given the cost increased from 47% to 72%. CONCLUSION: It is both possible and valuable to involve employees in priority setting regarding health insurance benefits through the use of structured decision tools.  相似文献   
47.
Abstract – The occurrence of supra- and subgingival calculus, gingival inflammation, periodontal pockets ( 5 mm) and alveolar bone loss was determined in children (10-19 yr) with Down's syndrome (D-S) and in an aged- and sex-matched control group ( n = 39). Of D-S children ( n = 71), 39 of the patients (mean age 15.5 yr) cooperated in a clinical and roentgenologic examination. Alveolar bone loss was determined around incisors and first molars on intraoral radiographs when the distance between cementoenamel junction (GEJ) to alveolar crest (AC) exceeded 2.0 mm. Alveolar bone loss was diagnosed in 39% of the D-S children compared to 3% in the control group ( P <0.001). Of the total number of sites examined on radiographs the distance from CEJ to AC exceeded 2.0 mm in 8% in the D-S group compared to 0.2% in the control group ( P <0.001). The frequency of sites with alveolar bone loss in D-S children was significantly ( P <0.001) higher around the mandibular incisors compared to first molars. The study shows that early signs of periodontitis are frequently seen in D-S children as early as 11 yr of age and the lesions are first diagnosed in the mandibular anterior region.  相似文献   
48.
In vitro and ex vivo effects of indobufen on red blood cell deformability   总被引:1,自引:0,他引:1  
Summary We have studied the effect of indobufen, a cyclo-oxygenase blocking agent which has proved useful in patients with obstructive vascular disease, on red blood cell (RBC) filterability in vitro and in a pilot study ex vivo.The addition of indobufen in vitro to blood samples from 10 healthy volunteers did not significantly modify RBC deformability.We evaluated the ex vivo effect of indobufen (200 mg bd) in 14 patients with obstructive vascular disease. A significant improvement in RBC deformability was noted on the 5th, 14th, and 28th days of treatment, 2 h after the morning dose. Acetylsalicylic acid given to 6 similar patients had no effect suggesting that the positive haemorheological effect of indobufen is probably not linked to its cyclooxygenase blocking effect.  相似文献   
49.
Color Doppler flow imaging or compression ultrasound (US) was used to prospectively determine frequency of thrombosis at 54 venous insertion sites (47 in common femoral veins, seven in right internal jugular veins) after percutaneous placement of Greenfield filters for interruption of the inferior vena cava. Fifty-one filters were successfully placed in 51 patients with a dilator set or a balloon angioplasty catheter. Nine focal thrombi were detected in the common femoral vein (19%) and one in the right internal jugular vein (14%). Use of dilators induced eight thrombi (24%), compared with two (10%) from balloon catheters. The left common femoral vein had a high frequency of thrombosis, regardless of dilation technique (five of nine). Of nine patients with acute common femoral vein thrombosis, four became symptomatic within 10 days after the procedure. Patients may remain asymptomatic or have delayed symptoms; thus, US is valuable for determining patients at risk of thrombosis of the common femoral vein.  相似文献   
50.
Myocardial tagging in polar coordinates with use of striped tags   总被引:1,自引:0,他引:1  
Bolster  BD  Jr; McVeigh  ER; Zerhouni  EA 《Radiology》1990,177(3):769-772
Regional deformation abnormalities in the heart wall provide a good indicator of ischemia. Myocardial tagging with magnetic resonance imaging is a new method of assessing heart wall motion during contraction. Current methods of myocardial tagging either do not provide two-dimensional information or lack a coordinate system well adapted to the morphology of the heart. In this article, the authors describe a new tagging method that provides a true polar coordinate system, with both radial and angular dimensions. This is accomplished with use of a section-selective version of spatially modulated magnetization resulting in striped tags (STAGs). These STAG planes are placed in the myocardium in a star pattern so that they intersect on the long axis of the heart and stripes appear through the width of the heart wall. In the short-axis view during contraction, rotation around the long axis yields angular information such as shear and twist, while separation of the stripes within the myocardium permits measurement of radial thickening. Therefore, this method provides a coordinate system for calculating two-dimensional strain that is adapted to the morphology of the left ventricle.  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