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   1075175篇
  免费   71832篇
  国内免费   1366篇
耳鼻咽喉   15020篇
儿科学   34616篇
妇产科学   28627篇
基础医学   153459篇
口腔科学   29558篇
临床医学   94974篇
内科学   203701篇
皮肤病学   24391篇
神经病学   81464篇
特种医学   42972篇
外国民族医学   201篇
外科学   163128篇
综合类   21752篇
现状与发展   1篇
一般理论   264篇
预防医学   74651篇
眼科学   24541篇
药学   86160篇
  7篇
中国医学   2805篇
肿瘤学   66081篇
  2019年   7760篇
  2018年   11305篇
  2017年   8907篇
  2016年   10098篇
  2015年   11267篇
  2014年   15276篇
  2013年   22210篇
  2012年   30558篇
  2011年   32304篇
  2010年   18964篇
  2009年   17824篇
  2008年   29959篇
  2007年   32088篇
  2006年   32710篇
  2005年   31039篇
  2004年   29737篇
  2003年   28575篇
  2002年   27559篇
  2001年   60034篇
  2000年   61493篇
  1999年   50946篇
  1998年   12445篇
  1997年   11001篇
  1996年   11017篇
  1995年   10325篇
  1994年   9348篇
  1993年   8863篇
  1992年   37801篇
  1991年   36280篇
  1990年   35757篇
  1989年   34296篇
  1988年   30871篇
  1987年   29991篇
  1986年   28221篇
  1985年   26457篇
  1984年   19192篇
  1983年   16120篇
  1982年   8828篇
  1979年   17037篇
  1978年   11409篇
  1977年   10236篇
  1976年   8842篇
  1975年   10070篇
  1974年   11658篇
  1973年   11281篇
  1972年   10757篇
  1971年   10097篇
  1970年   9261篇
  1969年   8944篇
  1968年   7918篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Glutathione-S-transferase (GST) genes encode a family of detoxification enzymes that offer protection against endogenous and exogenous sources of reactive oxygen species (ROS). Germline variations in GST genes may alter the catalytic efficiency of GST isoenzymes leading to a potential increase in susceptibility to the genotoxic effects of ROS and electrophilic substances. A nested case-control study design was used to examine the association between the polymorphic GST genes and prostate cancer risk among Finnish male smokers of the ATBC Cancer Prevention Study. A case-case analysis was used to determine the association between these genetic polymorphisms and prostate cancer progression. Germline DNA was obtained from 206 prostate cancer cases and 194 controls frequency matched on age, intervention group and study clinic. Cases and controls were genotyped for three GST genes using MALDI-TOF mass spectrometry or multiplex polymerase chain reaction (PCR). Relative to the wild-type genotype, we observed a 36% reduction in prostate cancer risk associated with the GST-M1-null genotype (odds ratio (OR) 0.64, 95% confidence interval (CI) 0.43, 0.95). Unlike GST-M1, GST-T1-null (OR 0.74, 95% CI 0.42, 1.33) and GST-P1*B (OR 1.10, 95% CI 0.72, 1.69) were not strongly associated with prostate cancer risk. We did not observe any significant associations between the selected polymorphic GST genes and tumour grade or stage. In conclusion, we did not observe a direct association between polymorphic GST-T1 or GST-P1 and prostate cancer risk. Our observation of a relatively strong inverse association between the GST-M1-null genotype and prostate cancer risk needs to be confirmed in larger association studies.  相似文献   
22.
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   
23.
24.
25.
26.
27.
28.
29.
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   
30.
We report the case of a 38-year-old woman who presented with chronic lower abdominal pain. Her past medical history included a splenectomy due to abdominal trauma. Ultrasound examination revealed four pelvic tumors which, upon laparotomy, were found to be the result of splenosis. Approximately 100 cases of splenosis have been reported but only a minority of them have been published in the gynecological literature. Our case indicates that those involved in pelvic scanning (even of asymptomatic women) and/or treating those complaining of lower abdominal pain or presenting with pelvic tumors should be aware of splenosis as a possible diagnosis.  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