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   248篇
  免费   8篇
电工技术   6篇
化学工业   121篇
金属工艺   13篇
机械仪表   2篇
建筑科学   8篇
轻工业   26篇
石油天然气   1篇
无线电   6篇
一般工业技术   50篇
冶金工业   6篇
原子能技术   10篇
自动化技术   7篇
  2023年   1篇
  2022年   1篇
  2021年   3篇
  2020年   2篇
  2019年   2篇
  2018年   4篇
  2017年   2篇
  2016年   3篇
  2015年   2篇
  2014年   2篇
  2013年   8篇
  2012年   7篇
  2011年   14篇
  2010年   9篇
  2009年   13篇
  2008年   7篇
  2007年   9篇
  2006年   11篇
  2005年   2篇
  2004年   3篇
  2003年   5篇
  2002年   7篇
  2001年   7篇
  2000年   4篇
  1999年   10篇
  1998年   5篇
  1997年   4篇
  1996年   3篇
  1995年   5篇
  1994年   4篇
  1993年   5篇
  1992年   4篇
  1991年   14篇
  1990年   8篇
  1989年   4篇
  1988年   8篇
  1987年   13篇
  1986年   8篇
  1985年   10篇
  1984年   7篇
  1983年   3篇
  1982年   4篇
  1981年   1篇
  1980年   2篇
  1973年   2篇
  1970年   1篇
  1968年   1篇
  1967年   2篇
排序方式: 共有256条查询结果,搜索用时 0 毫秒
71.
Previously we reported that serum CA125 level is elevated in cases of pericardial effusion. We report three cases in which serum CA125 measurement is useful for assessing clinical status. In case 1, a 19-year-old came to our hospital for cardiac tamponade. Moderate degree of pericardial effusion and high CA125 level were observed. After the pericardectomy the serum CA125 level was normalized and pericardial effusion disappeared. Case 2, a 50-year-old man with mesothelioma and in whom serum CA125 level was elevated with pericardial effusion. After cardiac drainage his condition improved, with decreased CA125 level. However, later the CA125 level rose and recurrent localized pericardial effusion with worsening condition was observed. In case 3, in a 78-year-old woman with pericardial effusion no recurrence was observed after pericardial drainage. Her CA125 value was normal. These results indicated that measurement of CA125 value is a useful marker for assessing the clinical course of this disease.  相似文献   
72.
A novel characterization method was applied to study the morphological changes of large pores in a ceramic green body during the early stage of densification at 1100°C for 1–64 h. Large processing pores were present in the green body. They were preserved after densification up to a relative density of 83.9% with their shape and size unchanged significantly. The pore size distribution determined by mercury porosimetry showed the growth of matrix pores of small size, but failed to show the change of large processing pores with densification.  相似文献   
73.
The dehydrochlorination of a syndiotacticity-enriched poly(vinyl chloride) (s-PVC) gave polyene materials and the structure and properties of dehydrochlorinated specimens were studied. The results were compared with those obtained for polyene materials formed from a commercial poly(vinyl chloride) (c-PVC). The crystallinity of the s-PVC was higher than that of the c-PVC as revealed by the infrared analysis and X-ray diffraction studies. The dehydrochlorinated specimens from the s-PVC were crystalline to some extent while those from the c-PVC were amorphous. The molecular orientation in the original films was preserved in the dehydrochlorinated specimens. The polyene films from the s-PVC had larger conductivities and showed better doping properties as compared with those from the c-PVC. These results were explained in terms of the larger crystallinity and the increased structural regularity of the s-PVC as compared with those of the c-PVC.  相似文献   
74.
The combination of a filter cake forming process and hot isostatic pressing was applied to prepare hydroxyapatite composites containing dispersed tetragonal zirconia polycrystal (TZP) with high strength and toughness. Fine TZP powder was dispersed into as-synthesized hydroxyapatite slurry, formed with the filter cake process and hot isostatically pressed at 800–1150 °C at 100 MPa for 2 h. The temperature needed for densification increased with increasing TZP content; 1100 °C was needed to fully densify the composite with 26.8 wt% TZP. No phase change was found in TZP nor in the hydroxyapatite phase up to the maximum temperature examined in hot isostatic pressing. Significant phase change was found in specimens annealed in air at 1200 °C. The strength and toughness achieved were respectively 190 MPa and 2.3 MPa m1/2. These values were approximately 20% and 100% higher than the corresponding values for hydroxyapatite ceramics without TZP particle dispersion.  相似文献   
75.
The dynamic moduli of isotactic polypropylene (PP) filled with ultrafine SiO2 and micron sized glass particles are measured in the temperature range 30–130°C at frequency 10 Hz. The storage moduli of PP composites, E′c, increase with filler content and decreasing filler size in the whole range of temperature. The loss moduli of PP composites, E″c, increase with filler content and decreasing filler size above 40°C. The intensity of the broad despersion which appears at ca. 60°C increases with filler content and decreasing filler size. By assuming that the energy is not dissipated in the effective volume, namely, filler volume plus that of immobilized interfacial region, the effective volume fraction is evaluated from the relative loss modulus, E″cE″0 at 60°C. The effective volume fraction increases with filler content and decreasing filler size. The effect of addition of ultrafine particles on the broad dispersion at ca. 60°C resembles the effect of increasing crystallinity of pure PP. It is concluded that the broad dispersion which appeared at ca. 60°C seemed to be assigned to the grain boundary of PP composities or crystalline boundary of pure PP.  相似文献   
76.
Homopolymer of 2-methyl-N-vinylimidazole and copolymer of the monomer with acrylamide were coupled with some aromatic diazonium compounds to give polymeric azo dyes. The dyestuff prepared from the homopolymer was soluble in water only when it was coupled with diazonium component containing sulfonic acid group, but the dyestuffs prepared from the copolymer were soluble. The reactivity, chemical structure, color, and dyeability of the polymeric dyes are discussed by comparing them with those of the corresponding monomeric dyes. The color fastness of the polymeric dyes was found to be in a high class; the rubbing and dry-cleaning fastness were especially excellent.  相似文献   
77.
A new preparation method is introduced to reveal intracellular structures in the scanning electron microscope and its application to mitotic cells in root meristems of Vicia faba is demonstrated. The root tips are fixed with a mixture of formaldehyde and glutaraldehyde and the fixed tissues are frozen and fractured in liquid nitrogen. They are then incubated successively in dilute solutions of aldehyde (formaldehyde or glutaraldehyde) and osmium tetroxide. By this treatment, the excess cell-matrix is removed from the fractured surface of the cell, and a deep view into the cell-interior can be obtained with the scanning electron microscope. Varied levels of substructure are observed on the surface of chromosomes.  相似文献   
78.
79.
80.
Characterization of processing defects in structural ceramics is very important for the investigation of mechanical property, because processing defects are origin of fracture and govern the strength of products. The relationship between defects and strength is represented by simple equation which contains factor of defect size. In this study, size of defects in alumina ceramics was measured by optical microscopy with sintered body thinned to about 150 μm. The size distribution was used for strength calculation based on linear fracture mechanics. Average and Weibull modulus of calculated strength were very agreed with experimentally measured them. The result shows that defects in sintered body govern the strength and are quantitatively related to strength by fracture mechanics.  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