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   2784篇
  免费   12篇
  国内免费   2篇
电工技术   8篇
综合类   1篇
化学工业   52篇
金属工艺   7篇
机械仪表   8篇
建筑科学   19篇
矿业工程   1篇
能源动力   5篇
轻工业   32篇
水利工程   5篇
无线电   57篇
一般工业技术   40篇
冶金工业   2527篇
原子能技术   2篇
自动化技术   34篇
  2022年   5篇
  2021年   5篇
  2020年   6篇
  2019年   7篇
  2018年   5篇
  2017年   6篇
  2016年   4篇
  2013年   23篇
  2012年   15篇
  2011年   13篇
  2010年   10篇
  2009年   11篇
  2008年   16篇
  2007年   18篇
  2006年   7篇
  2005年   13篇
  2004年   13篇
  2003年   16篇
  2002年   13篇
  2001年   12篇
  2000年   4篇
  1999年   74篇
  1998年   828篇
  1997年   437篇
  1996年   295篇
  1995年   165篇
  1994年   122篇
  1993年   155篇
  1992年   22篇
  1991年   22篇
  1990年   26篇
  1989年   29篇
  1988年   26篇
  1987年   30篇
  1986年   27篇
  1985年   20篇
  1984年   2篇
  1983年   7篇
  1982年   15篇
  1981年   12篇
  1980年   19篇
  1979年   3篇
  1978年   6篇
  1977年   54篇
  1976年   158篇
  1975年   3篇
  1966年   4篇
  1964年   2篇
  1963年   2篇
  1955年   2篇
排序方式: 共有2798条查询结果,搜索用时 15 毫秒
131.
132.
133.
Thyramine, a polypeptide factor from thymus, at wide range of concentrations increased the cAMP content in rat thymocytes. Increase in the cAMP content was less distinct in spleen lymphoid cells. Thyramine decreased the cGMP content in thymocytes; minimal nucleotide level was found within 15 min of incubation. The data obtained suggest that the rate of lymphocyte maturation is important for response of the cells to the effect of immunoregulating agents.  相似文献   
134.
135.
136.
137.
Four random samples representing populations at low (volunteer blood donors), intermediate, (VD clinic patients), high (family contacts of chronic antigen carriers) and very high (male homosexuals) risk of exposure to HBV were surveyed. Among HBsAg and anti-HBs negative individuals an average of 3.3% were found to be anti-HBc positive, and among those with anti-HBs, 19.4% were anti-HBc positive. Anti-HBc, with concurrent anti-HBs and without, was detected more frequently in the high risk samples than in the low risk. Individuals was a past history of acute viral hepatitis were more frequently anti-HBc positive than those without such a history, and anti-HBc positivity was frequently accompanied by serum transaminase elevation. Anti-HBc may persist for many years after an episode of acute hepatitis. In households of carriers, the highest frequency of anti-HBc was observed among spouses, which would argue for the possibility of sexual transmission. A significant excess of females with both types of antibody was observed in families of carriers. Anti-HBc determinations in conjunction with other HBV markers, provide a useful new tool for epidemiologic studies.  相似文献   
138.
Upon exposure to specific antigen in tissue culture, sensitive lymphocytes released macrophage migration inhibition factor and other lymphokines into the supernatant culture medium. Migration of peritoneal macrophages from nonsensitive animals was inhibited in the presence of such supernatants. However, with previous techniques it was found that an inhibitory effect was present at only low low titers (less than 10(2)). It is therfore of great interest that by increasing cellular density, the total number of cells being kept constant, inhibitory activity can be amplified by a factor as great as 10(10). This amplification was observed only when lymphocytes and macrophages were loosely packed, as by spontaneous sedimentation in a conical test tube. The effect was abolished by dispersing the cell suspension in a flat-bottomed flask or, alternatively, by shaking the test tube so that intimate prolonged intercellular contact was prevented.  相似文献   
139.
140.
On examination of the thumbs of 20 dissected preparations of ligaments and joints, of ten dry skeletons and of a number of living hands, apoposition (from apo = away from) was distinguished as a position in which the first carpometacarpal joint is fully abducted and laterally rotated and in which one or both distal joints of the thumb are flexed. Apoposition is commonly used in writing and it has a specific osteoligamentous basis for its stability: (1) a Y-shaped intermetacarpal ligament is attached by two crura to the base of the second metacarpal bone and by a common stem to the first metacarpal. Together with the palmar and dorsal oblique ligaments it becomes taut at abduction and establishes thereby a fixed center for the circumduction. Stability is enhanced as the circumduction takes place in the radial flat part of the joint away from the center; (2) of the two palmar prominences of the head of the first metacarpal bone the radial is the larger. At 25-30 degrees flexion in the metacarpophalangeal joint the prominence fits into an excavation on the base of the proximal phalanx in a manner which together with the ulnar collateral ligament locks the joint against mutual abduction and lateral rotation, and (3) the radial part of the trochlea of the interphalangeal joint is larger than the ulnar and secures, together with the ulnar collateral ligament, the joint against a radial luxation. Apoposition does not require activity of the thumb muscles; it is brought about by applying an external force to the ulnar side of the thumb and it is checked by ligaments and the shape of the joints.  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