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   1586088篇
  免费   126330篇
  国内免费   3901篇
耳鼻咽喉   20291篇
儿科学   51163篇
妇产科学   44396篇
基础医学   223259篇
口腔科学   41582篇
临床医学   143103篇
内科学   321239篇
皮肤病学   35716篇
神经病学   133792篇
特种医学   59555篇
外国民族医学   477篇
外科学   237481篇
综合类   35761篇
现状与发展   5篇
一般理论   750篇
预防医学   126708篇
眼科学   35222篇
药学   110847篇
  2篇
中国医学   3647篇
肿瘤学   91323篇
  2021年   13611篇
  2019年   14415篇
  2018年   19865篇
  2017年   15335篇
  2016年   17060篇
  2015年   19372篇
  2014年   27474篇
  2013年   40819篇
  2012年   56159篇
  2011年   59619篇
  2010年   34899篇
  2009年   33157篇
  2008年   55496篇
  2007年   58813篇
  2006年   58946篇
  2005年   57880篇
  2004年   55303篇
  2003年   52527篇
  2002年   50532篇
  2001年   74604篇
  2000年   75780篇
  1999年   63312篇
  1998年   19312篇
  1997年   17403篇
  1996年   17417篇
  1995年   16393篇
  1994年   14877篇
  1993年   13963篇
  1992年   46889篇
  1991年   44490篇
  1990年   42408篇
  1989年   40390篇
  1988年   37062篇
  1987年   36248篇
  1986年   33736篇
  1985年   32242篇
  1984年   25090篇
  1983年   21308篇
  1982年   13780篇
  1981年   12195篇
  1979年   21411篇
  1978年   15387篇
  1977年   12874篇
  1976年   12079篇
  1975年   12217篇
  1974年   14567篇
  1973年   14070篇
  1972年   13011篇
  1971年   11792篇
  1970年   11211篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Levels of the soluble form of the triggering receptor expressed on myeloid cells (sTREM)-1 are elevated in severe sepsis. However, it is not known whether sTREM-1 measurements can distinguish milder bacterial infections from noninfectious inflammation. The present authors studied whether serum sTREM-1 levels differ in community-acquired pneumonia, exacerbations of chronic obstructive pulmonary disease (COPD), asthma and controls, and whether sTREM-1 may be used as a surrogate marker for the need for antibiotics. Serum sTREM-1 levels in 150 patients with pneumonia, COPD and asthma exacerbations and 62 healthy controls were measured. Serum sTREM-1 levels were significantly elevated in pneumonia (median 295.2 ng x mL(-1)), COPD (280.3 ng x mL(-1)) and asthma exacerbations (184.0 ng x mL(-1)) compared with controls (83.1 ng x mL(-1)). Levels were higher in pneumonia and Anthonisen type 1 COPD exacerbations than in type 2 and 3 COPD and asthma exacerbations. The area under the receiver operating characteristics curve for sTREM-1 as a surrogate marker for the need for antibiotics was 0.77. Serum levels of the soluble form of the triggering receptor expressed on myeloid cells-1 were elevated predominantly in pneumonia and Anthonisen type 1 COPD exacerbations versus type 2 and 3 chronic obstructive pulmonary disease exacerbations, asthma and controls. Serum levels of the soluble form of the triggering receptor expressed on myeloid cells-1 has moderate but insufficient accuracy as a surrogate marker for the need for antibiotics in lower respiratory tract infections.  相似文献   
22.
Ninety-seven inpatients with tardive dyskinesia (average AIMS score = 13), the majority of whom were schizophrenic, were studied. Forty patients were Caucasian, and 57 were African-American. The APOE genotypes of these patients were compared to previously published genotypes of controls and with previously published studies of APOE genotypes in patients with schizophrenia. There were no significant differences in APOE allele frequencies comparing the African-American tardive dyskinesia population and the African-American control groups. In contrast, significant (< 0.05) P values were obtained comparing the Caucasian tardive dyskinesia population to the Caucasian controls, when comparing allele frequencies and genotypic frequencies. This study suggests that Caucasians bearing an APOE2 allele are at increased risk of developing tardive dyskinesia, whereas African-Americans are not. APOE genotype-specific risks of both tardive dyskinesia and Alzheimer's disease that vary across populations could be due to recruitment of patients or controls or could be due to modifying effects of differing genetic or environmental backgrounds. The mechanism by which the APOE2 allele increases risk of tardive dyskinesia is not known. Further information about the mechanisms of increased risk of tardive dyskinesia could result in stratification of prescribing practices weighing the costs of medications against the relative risk of side effects.  相似文献   
23.
24.
25.
26.
27.
B.  Greg  Brown  John  Growley  宋善俊 《美国医学会杂志》2006,25(2):124-126
过去15年来,有关动脉粥样硬化的流行病学、基础生物学和实验研究均支持下述假设:抗氧化剂可通过抑制动脉壁低密度脂蛋白的氧化而抑制动脉粥样硬化的发生。这种作用机制可抑制胆固醇酯通过巨噬细胞清除受体在动脉斑块内发生病理性沉积。胆固醇酯病理沉积是一种可引起斑块破裂及心血管事件的过程。同样,生物机制亦已确定,癌基因可被抗氧化剂阻断。  相似文献   
28.
29.
30.
OBJECTIVE: To establish reference intervals for the fetal right, left and total lung volumes and heart volume between 12 and 32 weeks of gestation. METHODS: Fetal lung and heart volumes were measured using three-dimensional (3D) ultrasound in 650 normal singleton pregnancies at 12-32 weeks. The VOCAL (Virtual Organ Computer-aided AnaLysis) technique was used to obtain a sequence of six sections of each lung and the heart around a fixed axis, each after a 30 degrees rotation from the previous one. The rotation axis for the lungs extended from the apex to the upper limit of the diaphragm dome, and the rotation axis for the heart extended from its apex to its connection to the great vessels. The contour of each of these organs was drawn manually in the six different rotation planes to obtain the 3D volume measurement. In 60 cases the fetal lungs and heart volumes were measured by the same sonographer twice and also by a second sonographer once in order to compare the measurements and calculate intra- and interobserver agreement. RESULTS: The total lung volume and heart volume increased with gestation, from respective mean values of 1.6 and 0.6 mL at 12 weeks to 10.9 and 4.3 mL at 20 weeks and 49.3 and 26.6 mL at 32 weeks. The right to left lung volume ratio did not change significantly with gestation (median, 0.7), whereas the heart to total lung volume ratio increased with gestation from about 0.3 at 12 weeks to 0.5 at 32 weeks. In the Bland-Altman plot, the difference between paired measurements by two sonographers was, in 95% of the cases, less than 0.05, 0.5 and 1.9 mL for each lung at 12-13, 19-22 and 29-32 weeks, respectively, and the corresponding values for the heart volumes were 0.04, 0.4 and 2.3 mL. CONCLUSIONS: In normal fetuses the lung and heart volumes increase between 12 and 32 weeks of gestation. The extent to which in pathological pregnancies possible deviations in these measurements from normal prove to be useful in the prediction of outcome remains to be determined.  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