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   3413篇
  免费   9篇
  国内免费   3篇
电工技术   1篇
综合类   3篇
化学工业   45篇
金属工艺   42篇
机械仪表   2篇
建筑科学   15篇
能源动力   2篇
轻工业   57篇
水利工程   2篇
石油天然气   2篇
无线电   15篇
一般工业技术   60篇
冶金工业   3140篇
原子能技术   5篇
自动化技术   34篇
  2023年   3篇
  2022年   9篇
  2021年   8篇
  2019年   4篇
  2018年   5篇
  2017年   5篇
  2016年   5篇
  2015年   3篇
  2014年   4篇
  2013年   8篇
  2012年   7篇
  2011年   9篇
  2010年   7篇
  2009年   8篇
  2008年   7篇
  2007年   7篇
  2006年   5篇
  2005年   11篇
  2004年   10篇
  2003年   13篇
  2002年   9篇
  2001年   7篇
  2000年   10篇
  1999年   107篇
  1998年   921篇
  1997年   513篇
  1996年   331篇
  1995年   184篇
  1994年   155篇
  1993年   182篇
  1992年   33篇
  1991年   44篇
  1990年   46篇
  1989年   50篇
  1988年   61篇
  1987年   63篇
  1986年   48篇
  1985年   43篇
  1984年   10篇
  1983年   14篇
  1982年   18篇
  1981年   22篇
  1980年   46篇
  1979年   9篇
  1978年   15篇
  1977年   99篇
  1976年   217篇
  1975年   10篇
  1973年   6篇
  1972年   4篇
排序方式: 共有3425条查询结果,搜索用时 15 毫秒
131.
132.
133.
134.
135.
136.
In comparison with pyeloplasty, endourologic procedures for the treatment of ureteropelvic junction obstruction offer good success rates with less morbidity and a shorter hospitalization; however, studies have found lower success rates and increased complications in patients with crossing vessels. Conventional diagnostic angiography and intravenous urography have both been used to identify crossing vessels at the UPJ; but, a reliable, less invasive, less costly, and simpler preoperative procedure to identify crossing vessels is needed. Helical CT with CT angiography is a promising noninvasive technique for the identification of crossing vessels at the ureteropelvic junction, which can be used for surgical planning of endourologic treatment of UPJ obstruction.  相似文献   
137.
Cell density-dependent inhibition of growth and neural differentiation in the human neuroblastoma cell line SK-N-MC are associated with a ganglioside sialidase-mediated increase of GM1 and lactosylceramide at the cell surface. Because these glycolipids expose galactose residues, we have initiated the study of the potential role of galectins in such cellular events. Using specific antibodies, galectin-1 but not galectin-3 was found to be present at the cell surface. Assessment of carbohydrate-dependent binding revealed a saturable amount of ligand sites approaching 2.6 x 10(6) galectin-1 molecules bound/cell. Presence during cell culture of the sialidase inhibitor 2-deoxy-2,3-dehydro-N-acetylneuraminic acid or of the GM1-binding cholera toxin B subunit effected a decrease of the presentation of galectin-1 ligands by 30-50%. The assumption that GM1 is a major ligand for galectin-1 was reinforced by the correlation between the number of carbohydrate-dependent 125I-iodinated GM1-neoganglioprotein binding sites and the amount of immunoreactive surface galectin-1, the marked sensitivity of probe binding to the presence of anti-galectin-1 antibody, and the inhibition of cell adhesion to surface-immobilized GM1 by the antibody. The results open the possibility that the carbohydrate-dependent interaction between ganglioside GM1 and galectin-1 may relay sialidase-dependent alterations in this cell system.  相似文献   
138.
139.
140.
BACKGROUND: Recent reports suggest that gamma-glutamyl transferase (GGT) decreases with coffee intake. The aim of this study was to examine the joint influence of alcohol, tobacco, cotinine, coffee, and caffeine on biological markers of heavy drinking in an alcoholic population. METHODS: Subjects were 160 alcohol-dependent inpatients. Biological assessments, performed at admission, were plasma levels of GGT, apolipoprotein AI, aspartate aminotransferase, and mean corpuscular volume (MCV), and urine cotinine and caffeine indexes. Years of alcohol abuse and of smoking, alcohol and coffee intake, and smoking rate were estimated in a semistructured interview, and Fagerstr?m Tolerance Questionnaire was completed by inpatients. RESULTS: Coffee intake, but not caffeine, correlated negatively with biological markers of heavy drinking, after controlling for alcohol and tobacco intake. Years of smoking correlated positively to MCV, after controlling for alcohol and coffee intake. CONCLUSIONS: Concerning the effect of coffee, the most likely hypothesis is that noncaffeine coffee fractions have a protective effect on liver cells. Concerning the effect of smoking, one can propose that the increase of MCV with smoking could be a consequence of carbon monoxide inhalation, leading to hypoxemia, or of folate deficiency.  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