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   74771篇
  免费   707篇
  国内免费   689篇
电工技术   1430篇
综合类   47篇
化学工业   11163篇
金属工艺   3445篇
机械仪表   2637篇
建筑科学   1640篇
矿业工程   504篇
能源动力   1852篇
轻工业   6385篇
水利工程   846篇
石油天然气   2303篇
武器工业   41篇
无线电   7193篇
一般工业技术   16440篇
冶金工业   12408篇
原子能技术   2628篇
自动化技术   5205篇
  2022年   575篇
  2021年   904篇
  2020年   698篇
  2019年   777篇
  2018年   1549篇
  2017年   1562篇
  2016年   1761篇
  2015年   945篇
  2014年   1555篇
  2013年   3562篇
  2012年   2356篇
  2011年   2817篇
  2010年   2367篇
  2009年   2639篇
  2008年   2616篇
  2007年   2551篇
  2006年   2182篇
  2005年   1912篇
  2004年   1837篇
  2003年   1787篇
  2002年   1703篇
  2001年   1676篇
  2000年   1669篇
  1999年   1562篇
  1998年   3667篇
  1997年   2599篇
  1996年   1934篇
  1995年   1523篇
  1994年   1326篇
  1993年   1348篇
  1992年   994篇
  1991年   1050篇
  1990年   1071篇
  1989年   1050篇
  1988年   940篇
  1987年   874篇
  1986年   877篇
  1985年   934篇
  1984年   777篇
  1983年   766篇
  1982年   675篇
  1981年   689篇
  1980年   661篇
  1979年   646篇
  1978年   620篇
  1977年   773篇
  1976年   930篇
  1975年   580篇
  1974年   551篇
  1973年   543篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
A rheological equation of state for wood which allows for the running values of its porosity and humidity is considered.  相似文献   
33.
The pyroelectric properties of lithium sulfate have been studied theoretically on the hypothesis of a pseudosymmetry of the structure of its polar phase. Analytical expressions are proposed for the temperature dependences of its pyroelectric polarization and pyroelectric coefficient at low temperatures and near the polymorphic transformation. The pyroelectric and piezoelectric coefficients of a polar crystal are shown to be in direct proportion.  相似文献   
34.
Magnetic roll separators on rare-earth magnets are suitable for removing iron impurities from various materials. The advantages of these magnetic separators over traditional ones are demonstrated. __________ Translated from Steklo i Keramika, No. 5, p. 33, May, 2005.  相似文献   
35.
New functionalized styrene–maleimide copolymers were prepared by free radical copolymerization of styrene (St) and N‐4‐carboxybutylmaleimide (NBMI) in chloroform, using 2,2′‐azobisisobutyronitrile (AIBN) as initiator. Monomer and copolymer characterization was carried out by 1H‐ and 13C‐NMR. Copolymer composition was determined by elemental analysis and Fourier‐transform infrared (FTIR) spectroscopy. The glass transition temperature (from DSC) and the thermogravimetric analysis (TGA) of the copolymers were consistent with the thermal behavior and stability observed for alternating St–maleimide copolymers. St–NBMI copolymers crosslinked with divinylbenzene (DVB) were also synthesized and their cation exchange properties evaluated in order to assess the capacity of the new copolymers to bind metallic ions. Copyright © 2005 Society of Chemical Industry  相似文献   
36.
37.
In this study, an aluminum based metallic matrix (Al-2wt.% Cu) was reinforced with SiC particulates using a conventional casting technique and a new disintegrated melt deposition technique. Microstructural characterization studies conducted on the samples taken from disintegrated melt deposition technique revealed a more uniform distribution of SiC particulates and good interfacial integrity between SiC particulates and metallic matrix when compared to the conventionally cast composite samples. Results of ambient temperature mechanical tests demonstrate an increase in 0.2% YS and ultimate tensile strength of samples taken from disintegrated melt deposition technique when compared with the unreinforced and conventionally cast composite samples. The results of microstructural characterization and mechanical testing were finally rationalized in terms of the nature of processing technique employed to reinforce Al-2wt.% Cu metallic matrix with SiC particulates.  相似文献   
38.
A set of divergent forms of heat-transfer equations are presented. New laws are established that govern the behavior of the temperature field behind the front of a strong discontinuity. Comparison of theoretical and experimental data on the propagation of nonlinear waves in a sapphire crystal and liquid helium is carried out. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 2, pp. 318–325, March–April 1997.  相似文献   
39.
40.
For pt.I see IEEE Trans. Neural Networks, vol.1, p.167-78 (1990). Parallel, self-organizing, hierarchical neural networks (PSHNNs) involve a number of stages with error detection at the end of each stage, i.e., rejection of error-causing vectors, which are then fed into the next stage after a nonlinear transformation. The stages operate in parallel during testing. Statistical properties and the mechanisms of vector rejection of the PSHNN are discussed in comparison to the maximum likelihood method and the backpropagation network. The PSHNN is highly fault tolerant and robust against errors in the weight values due to the adjustment of the error detection bounds to compensate errors in the weight values. These properties are exploited to develop architectures for programmable implementations in which the programmable parts are reduced to on-off or bipolar switching operations for bulk computations and attenuators for pointwise operations  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