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   2029篇
  免费   6篇
电工技术   2篇
综合类   1篇
化学工业   25篇
金属工艺   2篇
机械仪表   4篇
建筑科学   3篇
轻工业   48篇
无线电   3篇
一般工业技术   10篇
冶金工业   1923篇
自动化技术   14篇
  2021年   3篇
  2020年   3篇
  2018年   3篇
  2017年   3篇
  2015年   3篇
  2013年   4篇
  2012年   4篇
  2011年   5篇
  2010年   3篇
  2008年   3篇
  2007年   2篇
  2006年   3篇
  2005年   5篇
  2003年   7篇
  2000年   2篇
  1999年   53篇
  1998年   563篇
  1997年   317篇
  1996年   220篇
  1995年   137篇
  1994年   117篇
  1993年   100篇
  1992年   9篇
  1991年   23篇
  1990年   30篇
  1989年   25篇
  1988年   30篇
  1987年   23篇
  1986年   23篇
  1985年   22篇
  1983年   3篇
  1982年   4篇
  1981年   8篇
  1980年   14篇
  1978年   9篇
  1977年   66篇
  1976年   130篇
  1975年   4篇
  1972年   2篇
  1970年   2篇
  1968年   4篇
  1967年   2篇
  1966年   3篇
  1964年   3篇
  1962年   3篇
  1961年   4篇
  1960年   5篇
  1959年   5篇
  1958年   2篇
  1956年   2篇
排序方式: 共有2035条查询结果,搜索用时 15 毫秒
71.
72.
This study was undertaken to compare the fixation of the semitubular blade plate with that of the AO T plate. Cadaveric humeri (n=12 pairs) from an elderly population (41 to 89 years) had either a blade plate (n=12) or a T plate (n=12) fixed to them, subsequent to which a transverse osteotomy was performed. Mechanical testing in tension was performed in 1 series (n=5, blade plate; n=5, T plate) by applying a single maximal load to failure and in a second series (n=7, blade plate; n=7, T plate) by applying submaximal cyclic loading before failure was induced. Results showed that the fixation provided by the semitubular blade plate was significantly better (P < .05) than that of the T plate in those specimens subjected to submaximal cyclic loading before failure (series 2). This latter testing method contains some component of the clinical situation compared with monotonic distraction to failure. Based on these results plus favorable clinical results reported in the literature, the semitubular blade plate is possibly a better alternative to the T plate in the management of proximal humeral fractures that require open reduction and internal fixation.  相似文献   
73.
The finding of heat-stable enzymes or the engineering of moderately thermostable enzymes into more stable ones by random or site-directed mutagenesis has become a main priority of modern biotechnology. We report here for the first time a heat-stable phytase able to withstand temperatures up to 100 degrees C over a period of 20 min, with a loss of only 10% of the initial enzymatic activity. The gene (phyA) encoding this heat-stable enzyme has been cloned from Aspergillus fumigatus and overexpressed in Aspergillus niger. The enzyme showed high activity with 4-nitrophenyl phosphate at a pH range of 3 to 5 and with phytic acid at a pH range of 2.5 to 7.5.  相似文献   
74.
75.
Three fundamental criteria are defined by means of which test data are being judged relative to their information content. They must be UNIQUE, RELEVANT, and PREDICTIVE. The degree to which these criteria are met depends on the mechanistic understanding of the underlying corrosion or inhibition processes. It will be shown that of all the routine tests the Wheel Test procedure is the worst in that it does not meet is main objectives and cannot rank different inhibitors predictively. Comparative tests to establish the corrosion kinetics and performance/concentration curves for inhibitors were run in highly agitated kettles and small autoclaves. Corrosion rates were determined by iron analyses and weightloss determinations. The problem of the constantly changing pH in solution was eliminated by pH-stating. The inhibitor performance in some cases is strongly dependent on pH and CO2 partial pressure. All evaluations were done on AISI-1020 or AISI-1018 metal.  相似文献   
76.
77.
Compliance of the lungs and thorax was studied in 65 pregnant women during cesarean section. The measurements were carried out in a group of healthy controls and in patients with preeclampsia. The detected changes indicated increased rigidity of the lungs even in normal pregnancy. Comparison of the results indicates an appreciable increase of rigidity of the lungs in patients with preeclampsia, this permitting us to regard it as a status involving interstitial pulmonary hyperhydration.  相似文献   
78.
Forty-five cases of gastroschisis and 85 of omphalocele were reviewed. The survival of gastroschisis has dramatically improved over the past 20 years, however, that of omphalocele still remained in the lower value, because the size of the defect and the presence of associated anomalies are prognostic factors. The primary fascial closure was first employed for the patients with gastroschisis and a silo chimney was used for limited cases. On the other hand, for the patients with omphalocele, primary closure was possible in 34 cases, silo chimney was used in 17, and 45 cases had nonoperative management with epithelialization. Among them, nonoperative management using painting was the most reliable therapeutic for omphalocele.  相似文献   
79.
80.
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