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   4383篇
  免费   445篇
  国内免费   5篇
耳鼻咽喉   46篇
儿科学   281篇
妇产科学   119篇
基础医学   540篇
口腔科学   38篇
临床医学   542篇
内科学   713篇
皮肤病学   43篇
神经病学   313篇
特种医学   336篇
外科学   616篇
综合类   91篇
预防医学   502篇
眼科学   58篇
药学   267篇
中国医学   2篇
肿瘤学   326篇
  2021年   56篇
  2019年   47篇
  2018年   49篇
  2017年   50篇
  2016年   54篇
  2015年   57篇
  2014年   83篇
  2013年   121篇
  2012年   137篇
  2011年   185篇
  2010年   98篇
  2009年   137篇
  2008年   186篇
  2007年   236篇
  2006年   219篇
  2005年   192篇
  2004年   186篇
  2003年   150篇
  2002年   135篇
  2001年   139篇
  2000年   172篇
  1999年   139篇
  1998年   68篇
  1997年   47篇
  1996年   46篇
  1995年   56篇
  1994年   52篇
  1993年   49篇
  1992年   108篇
  1991年   112篇
  1990年   127篇
  1989年   122篇
  1988年   93篇
  1987年   97篇
  1986年   96篇
  1985年   100篇
  1984年   60篇
  1983年   51篇
  1982年   36篇
  1980年   39篇
  1979年   54篇
  1978年   44篇
  1977年   42篇
  1976年   43篇
  1975年   38篇
  1974年   54篇
  1973年   31篇
  1971年   28篇
  1970年   29篇
  1969年   25篇
排序方式: 共有4833条查询结果,搜索用时 31 毫秒
991.
992.
In an effort to develop radiopharmaceuticals useful for the diagnostic imaging of steroid receptor-positive breast tumors, we have radiolabeled an analog of the antiprogestin RU486 (mifepristone), modified to incorporate an N2S2 chelate system in the 11 beta-position, with 99Tc, 99mTc, and 186Re. For the 99Tc-labeled analogs (3), a syn pair and two individual antidiastereomers (linker methylene versus metal-oxo, relative to the N2S2 plane) were isolated. In competitive radiometric binding assays, the syn pair (3syn1,2) had affinity for the progesterone receptor that was 25% that of (promegestone) R5020 (or 161% that of progesterone), and the individual anti-diastereomers had affinities of 47% (3anti1) and 7% (3anti2) that of R5020 (or 303% and 45% that of progesterone). The specific-to-nonspecific binding ratio of the 99mTc (4) and 186Re (5) 11 beta-linked syn systems are 75/25 and 54/46, respectively. In vivo, conjugates 4 and 5 showed progesterone receptor-mediated uptake in rat uterus, but also high uptake in non-target tissues, presumably because of the high lipophilicity of the metal complexes. Modified systems may be useful in vivo as receptor-directed agents for diagnostic imaging or treatment of steroid receptor-positive tumors.  相似文献   
993.
Four healthy male subjects received single oral doses of 15, 30 and 60 mg of codeine and pholcodine according to a balanced cross-over design with an interval of 7 days between the six treatments. Blood samples were collected for 8 h after each drug administration. In phase 2 of the study six different male volunteers received single oral doses of 60 mg of codeine and pholcodine with a 14 day interval between successive drug treatments. Blood was sampled for 12 h after codeine and 121 h after pholcodine administration. Plasma concentrations of free (unconjugated) and total (unconjugated plus conjugated) codeine, pholcodine and morphine were determined by radioimmunoassay and selected pharmacokinetic parameters were derived from these data. Pharmacokinetics of both drugs were independent of dose. Codeine was absorbed and eliminated relatively rapidly [elimination t1/2 = 2.3 +/- 0.4 h (mean +/- s.d.)]. While codeine kinetics were adequately described by a one-compartment open model with first-order absorption, a two-compartment model was required to describe pholcodine elimination from plasma (t1/2,z = 37.0 +/- 4.2 h). Plasma concentrations of conjugated codeine were much greater than those of the unconjugated alkaloid. By contrast, pholcodine appeared to undergo little conjugation. Biotransformation of codeine to morphine was evident in all subjects, although the extent of this metabolic conversion varied considerably between subjects. Morphine was not detectable in the plasma of any subject after pholcodine administration.  相似文献   
994.
995.
996.
997.
Prevalence of seasonal affective disorder at four latitudes   总被引:10,自引:0,他引:10  
The Seasonal Pattern Assessment Questionnaire (SPAQ) was mailed to a sample population balanced for sex and randomly selected from local telephone directories in four areas: Nashua, NH, New York, NY, Montgomery County, MD, and Sarasota, FL. On the basis of responses to this questionnaire, prevalence rates of winter seasonal affective disorder (winter SAD), summer seasonal affective disorder (summer SAD), and subsyndromal winter SAD were estimated for the four areas. Rates of winter SAD and subsyndromal SAD were found to be significantly higher at the more northern latitudes, while no correlation was found between latitude and summer SAD. The positive correlation between latitude and prevalence of winter SAD applied predominantly to the age groups over 35.  相似文献   
998.
999.
1000.
Fifty healthy children were included in the study; tracheal and laryngeal aspirations were performed after oral endotracheal intubation during minor surgery. The aspirates were evaluated and examined in the same way as aspirates from children suspected of pneumonia; 31 samples were accepted for the final analysis. After culturing, specimens from 30 children exhibited growth of potential pathogenic bacteria either from the larynx, the trachea or both. Prior to culture, bacteria were seen by microscopy in 24 samples from 30 children. These results indicate that the majority of healthy children carry potential pathogenic bacteria, not only in the larynx but also to a certain extent in the trachea. We conclude that aspirates from the larynx and the trachea are of limited value in the diagnosis of bacterial pneumonia in children.  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