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   488篇
  免费   14篇
  国内免费   13篇
电工技术   3篇
综合类   3篇
化学工业   18篇
金属工艺   18篇
机械仪表   7篇
建筑科学   19篇
矿业工程   2篇
能源动力   3篇
轻工业   69篇
水利工程   1篇
石油天然气   1篇
无线电   23篇
一般工业技术   18篇
冶金工业   297篇
自动化技术   33篇
  2022年   5篇
  2021年   5篇
  2018年   4篇
  2017年   3篇
  2016年   2篇
  2015年   2篇
  2014年   2篇
  2013年   43篇
  2012年   4篇
  2011年   7篇
  2010年   5篇
  2009年   7篇
  2008年   11篇
  2007年   10篇
  2006年   10篇
  2005年   10篇
  2004年   6篇
  2003年   2篇
  2001年   4篇
  2000年   3篇
  1999年   8篇
  1998年   70篇
  1997年   64篇
  1996年   34篇
  1995年   18篇
  1994年   12篇
  1993年   19篇
  1992年   11篇
  1991年   5篇
  1990年   6篇
  1989年   5篇
  1988年   10篇
  1987年   7篇
  1986年   8篇
  1985年   11篇
  1984年   2篇
  1983年   2篇
  1982年   5篇
  1981年   3篇
  1980年   5篇
  1977年   9篇
  1976年   35篇
  1967年   1篇
  1966年   1篇
  1965年   1篇
  1964年   2篇
  1963年   1篇
  1959年   2篇
  1957年   2篇
  1956年   3篇
排序方式: 共有515条查询结果,搜索用时 15 毫秒
61.
62.
Six patients with a total of nine gonadoblastomas are presented; three--and possibly a fourth--had dysgerminomatous overgrowth which was massive in two patients. Calcification detected by abdominal films was present in three sufficient for preoperative diagnosis. All patients were found to have a Y stem line on peripheral leukocyte chromosome cultures except one patient, who had a 46 XX/45 XO karyotype. She was found to have Y chromatin bodies in the germ cells of her tumor which was in a normal ovary found at exploration for an ectopic pregnancy. Three were found in virilized phenotypic females investigated for amenorrhea, and two for therapy of pelvic masses due to dysgerminomatous overgrowth. Y chromatin studies are reported on gonadal tissue.  相似文献   
63.
64.
A case of isolated dislocation of the carpal scaphoid is presented and the literature on the subject reviewed. An analysis has been made of the cases reported and attention is drawn to certain features which are common to most of the cases.  相似文献   
65.
66.
This prospective cohort study was designed to test whether a distinct fatigue syndrome existed after the onset of glandular fever. Two hundred and fifty primary care patients, with either glandular fever or an ordinary upper respiratory tract infection (URTI) were interviewed three times in the 6 months after the clinical onset of their infection. At each interview a standardized psychiatric interview was given and physical symptoms were assessed. There were 108 subjects with and Epstein-Barr virus (EBV) infection; 83 subjects had glandular fever not caused by EBV and 54 subjects had an ordinary URTI. Five subjects were excluded because they had no evidence of an infection. Principal components analyses of symptoms supported the existence of a fatigue syndrome, particularly in the two glandular fever groups. The addition of symptoms not elicited by the standard interviews gave the full syndrome. This included physical and mental fatigue, excessive sleep, psychomotor retardation, poor concentration, anhedonia, irritability, social withdrawal, emotional lability, and transient sore throat and neck gland swelling with pain. A fatigue syndrome probably exists after glandular fever.  相似文献   
67.
68.
In this series of gonadoblastomas it appeared that the germ cells were the motivating force underlying either tumor proliferation or regression. The ultrastructural morphology confirmed the presence of undifferentiated gonadal cells with active steroid synthesis by the interstitial cells. The Call-Exner-like bodies which showed extensive calcification were composed of basement membrane material containing a sulfated mucosubstance. A histochemical comparison with the noncalcifying Call-Exner bodies of a granulosa-cell tumor differed only in their glycoprotein content. The calcium deposits were identified as oriented hydroxyapatite crystals by electron diffraction, and it is proposed that the basement membrane material serves as a nucleation site for calcification. High serum testosterone levels were correlated with the presence solely of interstitial cells in one case. The finding of a gonadoblastoma without the presence of a Y chromosome contradicts earlier proposals concerning the requirement of a Y chromosome for germ cell proliferation.  相似文献   
69.
The structure of a natural small-angle boundary in a magnetite bicrystal was investigated by X-ray diffraction. This boundary was a "general" type with a mixed twist and tilt character. The grain-boundary reflections observed around an 040 matrix reflection were in good agreement with those predicted by Boll-mann's O-lattice theory. These extra reflections appear to arise from a predominantly planar dislocation network. The structural width of the boundary, determined from the length of the relrods of the grain-boundary reflections, was of the order of four unit cells, close to the average spacing of the expected dislocation network.  相似文献   
70.
在市區進行夜間隧道鑽挖工程所產生的土傳噪音及震動,容易引起投訴。現時的技術難以準確預測噪音及震動的級數,而隧道工程的進度也常因進行隧道鑽挖工程時產生過大的土傳噪音及震動而延誤。本文所提述的新技術,可以更準確地量度及預測鑽機震動強度及土壤傳震的特性@個技術包括測量單位衝擊力及隧道鑽機摩擦力所產生的震動級數鋵嵲珈?80於代,美國政府運輸部門(U.S.DeptofTransportationFederalTransitAdministrative)已研發相關的技術,並將該技術應用於鐵路土傳噪音量度及預測上。本文報告隧道鑽機所產生的土傳噪音及震動級數1/3倍頻帶數值的量度及預測。比較地面震動峰值速度(PPV)、最高(Lmax)噪聲和振動級數按快速和緩慢的時間常數和整體百分比(Percentile)數值列出。  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