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   2834篇
  免费   23篇
  国内免费   1篇
电工技术   15篇
化学工业   132篇
金属工艺   34篇
机械仪表   23篇
建筑科学   23篇
矿业工程   2篇
能源动力   20篇
轻工业   132篇
水利工程   5篇
石油天然气   2篇
无线电   92篇
一般工业技术   164篇
冶金工业   2074篇
原子能技术   37篇
自动化技术   103篇
  2021年   7篇
  2019年   10篇
  2018年   11篇
  2017年   11篇
  2016年   6篇
  2015年   9篇
  2014年   11篇
  2013年   46篇
  2012年   27篇
  2011年   40篇
  2010年   36篇
  2009年   30篇
  2008年   35篇
  2007年   23篇
  2006年   22篇
  2005年   27篇
  2004年   31篇
  2003年   26篇
  2002年   29篇
  2001年   32篇
  2000年   29篇
  1999年   60篇
  1998年   530篇
  1997年   333篇
  1996年   221篇
  1995年   131篇
  1994年   120篇
  1993年   134篇
  1992年   27篇
  1991年   32篇
  1990年   32篇
  1989年   34篇
  1988年   31篇
  1987年   23篇
  1986年   25篇
  1985年   38篇
  1984年   8篇
  1983年   22篇
  1982年   27篇
  1981年   36篇
  1980年   42篇
  1979年   21篇
  1978年   20篇
  1977年   111篇
  1976年   211篇
  1975年   17篇
  1974年   6篇
  1973年   6篇
  1972年   7篇
  1971年   8篇
排序方式: 共有2858条查询结果,搜索用时 0 毫秒
921.
Study of the hormonal activity of the gonads of 97 males suffering from chronic alcoholism was undertaken to investigate the effects on hormonal secretion. An increased synthesis of androgens and estrogens was noted. The regularity of this increased with the duration of alcoholism. It is thought that the increased synthesis of sex hormones in chronic alcoholism is a defense adaptation directed to reducing the unfavorable effects of high concentration of alcohol in the blood. Alcoholism treatment involving teturam along with abstinence of alcohol caused a decrease in the functional activity of gonads, indicating the reversibility of this effect. The nature of functional alteration in the synthesis of sex hormones shows that it plays an essential role in the genesis of sexual impotence in alcoholism, through dyshormonal disruption of the endocrinal system.  相似文献   
922.
923.
The classical concept concerning the character of development of the blastomatose process in the brain is frequently altered when applied to children and adolescents with supratentorial newgrowths. An analysis of 102 cases with verified newgrowths of a different histological nature and localization in the supratentorial space permitted to distinquish 4 types of a clinical development of this kind of pathology: (1) with an acute onset and short-term development of the tumor process; 2) with a gradual, progressive increase of symptoms, but with expressed and long-term remissions; 3) with a slowly progressive development of the disease and a sudden severe syndrome of decompensation or terminal state; 4) with acute clinical signs of a newgrowth and a replacement by a subsequent progressive remittent development.  相似文献   
924.
925.
926.
927.
928.
Bacteriochlorophyll a reaction-center complex I from Chlorobium limicola f. thiosulfatophilum 6230 (Tassajara) was incubated in 2 M guanidine - HCl and then chromatographed on cross-linked dextran or agarose gel. Two principal components were separated: a larger component with photochemical activity (bacteriochlorophyll a reaction-center complex II) and a smaller component without activity (bacteriochlorophyll a protein). Complex II contains carotenoid, bacteriochlorophyll a, reaction center(s), and cytochromes b and c, but lacks the well characterized bacteriochlorophyll a protein contained in Complex I. Complex II carries out a light-induced reduction of cytochrome b along with an oxidation of cytochrome c.  相似文献   
929.
930.
The life expectancy of males in the United States is lower than that of males in most of the developed countries and in some of the not-so-developed ones. U.S. females, by contrast, do much better in international ranking. This study compares the mortality of U.S. white males with that of Swedish males who have had the highest reported male life expectancies in the world since the early 1960s. Life expectancy at birth in 1969-71 was 67.9 for U.S. white males compared with 71.9 for Swedish males. Greater U.S. white male mortality is found at all ages from birth through ages 75-79. At the upper ages there is a reversal of the differential with U.S. white males having lower mortality than their Swedish counterparts. The greatest relative differentials between the two male populations is found at ages under 1, ages 20-24, and ages 50-59. At ages under 1 the greater U.S. white male mortality is accounted for mainly by higher death rates from infectious diseases, at ages 20-24 by higher rates from the external causes of death (specifically accidents and homicide), and at ages 50-59 from most of the major organic causes of death.  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