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   3469篇
  免费   257篇
  国内免费   11篇
电工技术   49篇
综合类   4篇
化学工业   862篇
金属工艺   106篇
机械仪表   123篇
建筑科学   171篇
矿业工程   10篇
能源动力   272篇
轻工业   652篇
水利工程   14篇
石油天然气   27篇
无线电   187篇
一般工业技术   517篇
冶金工业   140篇
原子能技术   65篇
自动化技术   538篇
  2024年   17篇
  2023年   50篇
  2022年   98篇
  2021年   177篇
  2020年   124篇
  2019年   125篇
  2018年   208篇
  2017年   187篇
  2016年   211篇
  2015年   126篇
  2014年   190篇
  2013年   426篇
  2012年   213篇
  2011年   239篇
  2010年   248篇
  2009年   211篇
  2008年   146篇
  2007年   167篇
  2006年   68篇
  2005年   40篇
  2004年   30篇
  2003年   31篇
  2002年   34篇
  2001年   16篇
  2000年   17篇
  1999年   9篇
  1998年   36篇
  1997年   18篇
  1996年   25篇
  1995年   16篇
  1994年   13篇
  1993年   10篇
  1992年   10篇
  1991年   8篇
  1990年   9篇
  1989年   9篇
  1988年   6篇
  1987年   14篇
  1986年   12篇
  1985年   7篇
  1984年   23篇
  1983年   9篇
  1982年   8篇
  1980年   14篇
  1979年   7篇
  1978年   13篇
  1977年   8篇
  1976年   20篇
  1975年   10篇
  1972年   4篇
排序方式: 共有3737条查询结果,搜索用时 15 毫秒
1.
2.
Metal Science and Heat Treatment - The effect of solid boronizing at 950°C for 2 and 4 h on the phase composition, microstructure, hardness and abrasive wear of steel AISI 304L is studied...  相似文献   
3.
4.
Alkyd resins are generally used in the production of printing inks. All industries look for alternative raw materials in the production of ink with the growing inclination toward using natural products. Resins forming the vehicle of the ink to be obtained from natural resources will provide benefits for the environment, nature, and living creatures. The aim of the study was to promote the use of natural resin in the ink system. Natural Pinus pinaster resin was added into vegetable and mineral oil-based solvents in pure form with alkyd resin in different amounts and ink varnishes of different combinations were prepared. Then, printing inks were produced from these varnishes in pure and hybrid form. Following the assessment of the rheological properties of the inks prepared, printing tests were conducted to assess the printing quality parameters. Ideal mixing ratios of the natural resins in the ink were determined for printability. The environmental importance and advantages of the use of natural resins were discussed. Recommendations were given in line with the results to encourage widespread use of natural resins in near future.  相似文献   
5.
6.
7.
8.
9.
In this study, the relationship between stunning techniques and protein oxidation which are accepted as the main cause of food spoilage was investigated. For this purpose, the antioxidant status, in vivo myofibrillary protein (MP) oxidation and sensitivity, and postmortem oxidation (inducted with hydroxyl radical system) of rainbow trout (Oncorhynchus mykiss) fillets killed by hitting to head (T1), neck crushing (T2), and convulsion (T3) methods, were investigated. Statistically significant differences (p < .05) were found among all parameters examined and it was observed that the most stressing technique was the convulsion method. It was determined that in protein profiles myosin were influenced too much from stunning technique and in actin observed oxidation-induced reductions. Reductions in S-S and S-H were also found to be increased in carbonyl concentrations, but the most effective values in both processes were determined by the convulsive technique. Our results show that short-term stunning techniques (hitting to head, neck crushing) give better meat quality results in terms of O. mykiss welfare and low MP oxidation rates. In general, we can say that T3 group fillets are more sensitive to oxidative damage, while T1 and T2 groups give better results in maintaining meat quality with low MP oxidation rates.  相似文献   
10.
We derive an expression for transmittivity (TSHG) of second harmonic generation (SHG) signals from a ferroelectric (FE) film. Intensities of up and down fields in the medium are investigated in relation to TSHG. The derivations are made based on undepletion of input fields and nonlinear wave equation derived from the Maxwell equations. We present two cases: film without mirrors and with partial mirrors. Expressions for the newly derived nonlinear susceptibility coefficients of SHG for real crystal symmetry [J. Opt. Soc. Am. B 19 (2002) 2007] are used to get more realistic results. Variations in TSHG with respect to film thickness are illustrated.  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