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   582篇
  免费   19篇
  国内免费   4篇
电工技术   19篇
综合类   2篇
化学工业   109篇
金属工艺   5篇
机械仪表   19篇
建筑科学   10篇
能源动力   11篇
轻工业   42篇
水利工程   5篇
石油天然气   3篇
无线电   26篇
一般工业技术   66篇
冶金工业   265篇
原子能技术   5篇
自动化技术   18篇
  2024年   3篇
  2022年   10篇
  2021年   13篇
  2020年   6篇
  2019年   17篇
  2018年   14篇
  2017年   11篇
  2016年   6篇
  2015年   17篇
  2014年   15篇
  2013年   24篇
  2012年   22篇
  2011年   15篇
  2010年   24篇
  2009年   13篇
  2008年   18篇
  2007年   9篇
  2006年   8篇
  2005年   4篇
  2004年   3篇
  2003年   5篇
  2002年   3篇
  2001年   3篇
  2000年   3篇
  1999年   18篇
  1998年   65篇
  1997年   47篇
  1996年   44篇
  1995年   26篇
  1994年   25篇
  1993年   25篇
  1992年   6篇
  1991年   8篇
  1990年   4篇
  1989年   6篇
  1988年   3篇
  1987年   6篇
  1986年   8篇
  1985年   5篇
  1984年   5篇
  1983年   3篇
  1982年   3篇
  1981年   6篇
  1980年   6篇
  1978年   2篇
  1977年   4篇
  1976年   8篇
  1974年   2篇
  1969年   1篇
  1967年   1篇
排序方式: 共有605条查询结果,搜索用时 15 毫秒
1.
2.
In-service fracture of helicopter windshields was studied. Simulated catastrophic fracture tests were conducted by firing alumina and steel spheres onto stationary tempered and as-received glass panels. The results were studied by Hertzian analysis and modified Auerbach's relations. Thermally tempered glass shows much higher impact resistance than that estimated from superposition of residual stresses. Subcritical impact sites exhibit slow crack growth in tempered plates, eventually leading to fracture of the entire plate.  相似文献   
3.
Attachment between parent and child plays a crucial role in the healthy development of the child. Accordingly disturbances in parental bonding will be linked with the development of mental disorders later in life. The present study examines the relationship between parental bonding and mental health in healthy adolescents. Participants were 847 Israeli high school students who completed the Parental Bonding Instrument (PBI), the Brief Symptom Inventory (BSI), the General Well-Being (GWB), the Perceived Social Support (PSS), and the Social Desirability scale (SDS). In general, Israeli adolescents reported more parental care and less control than did Australian adolescents and adults. Female subjects reported more maternal care than did males. Subjects who reported high care and low control (optimal bonding) reported less distress, better general well-being and better social support that did all other groups. In contrast, those who reported low care and high control (affectionless control bonding) had the highest BSI scores and the lowest GWB and PSS scores. These results are in line with Bowlby's theory of attachment. They also show that specific configuration of parental bonding are linked with distress and isolation in adolescents.  相似文献   
4.
In this paper the implementation of a suggested stand-alone PV system, for maximum-power point tracking (MPPT), is carried out. Also, this paper presents a comparative study, through experimental work, between the conventional PI controller and the fuzzy logic controller (FLC) under different atmospheric conditions. The implemented system with both the PI controller and the FLC gives a good maximum-power operation of the PV array, but the tracking capability for different optimum operating points is better and faster for the case of using the FLC compared to the case of using the PI controller.  相似文献   
5.
Phospholipid transfer protein (PLTP) was purified from lipoprotein-free human plasma, obtained upon treatment of plasma with dextran sulfate and Ca2+, by employing a series of column chromatography. Upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the purified PLTP showed a single main band, corresponding to the molecular mass of 78 kDa. However, isoelectric focusing of the purified preparation gave multiple bands with pI ranging from 4.3 to 5.1, indicative of microheterogeneity. Purified PLTP was shown to possess not only phospholipid transfer activity, but also high density lipoprotein (HDL) conversion activity (Tu, A.-Y., Nishida, H. I., and Nishida, T. (1990), FASEB J. 4, A2148; Jauhiainen, M., Metso, J., Pahlman, R., Blomqvist, S., van Tol, A., and Ehnholm, C. (1993) J. Biol. Chem. 268, 4032-4036). Isolated HDL3 was enlarged to the size of HDL2b upon incubation with purified PLTP for 6 h at 37 degrees C at the PLTP/HDL3 molar ratio of approximately 1:45. Both the HDL conversion and the phosphatidylcholine transfer activities of purified PLTP were effectively inhibited by rabbit anti-PLTP immunoglobulin G. The primary importance of PLTP in the HDL enlargement that occurs in human plasma upon incubation at 37 degrees C was shown by the strong inhibitory effect of the anti-PLTP immunoglobulin G. The process of PLTP-mediated HDL enlargement was accompanied by the release of apoproteins, primarily apoA-I. HDL3 enlargement mediated by PLTP was effectively inhibited by the addition of free fatty acids.  相似文献   
6.
7.
8.
9.
We present a method for unified statistical analysis of short and long range correlations between various nucleotides in genomic DNA strands. The approach is based on the mutual study of Fourier structure factor spectra and pair correlation functions. The analysis of cross correlations in the different ranges of structural spectra permits identification of the main sources of correlations, namely, the coherent point mutations, coincident periodicities or large scale density variations. The technique for assessment of structural coupling between various genes in the genome is also described.  相似文献   
10.
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