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   74779篇
  免费   710篇
  国内免费   689篇
电工技术   1429篇
综合类   47篇
化学工业   11166篇
金属工艺   3445篇
机械仪表   2636篇
建筑科学   1649篇
矿业工程   503篇
能源动力   1852篇
轻工业   6388篇
水利工程   845篇
石油天然气   2304篇
武器工业   41篇
无线电   7193篇
一般工业技术   16439篇
冶金工业   12405篇
原子能技术   2627篇
自动化技术   5209篇
  2022年   573篇
  2021年   905篇
  2020年   699篇
  2019年   779篇
  2018年   1550篇
  2017年   1562篇
  2016年   1761篇
  2015年   944篇
  2014年   1556篇
  2013年   3564篇
  2012年   2356篇
  2011年   2820篇
  2010年   2367篇
  2009年   2639篇
  2008年   2615篇
  2007年   2551篇
  2006年   2183篇
  2005年   1912篇
  2004年   1839篇
  2003年   1786篇
  2002年   1704篇
  2001年   1676篇
  2000年   1669篇
  1999年   1562篇
  1998年   3665篇
  1997年   2600篇
  1996年   1934篇
  1995年   1521篇
  1994年   1325篇
  1993年   1351篇
  1992年   994篇
  1991年   1051篇
  1990年   1072篇
  1989年   1051篇
  1988年   941篇
  1987年   874篇
  1986年   877篇
  1985年   935篇
  1984年   777篇
  1983年   766篇
  1982年   676篇
  1981年   690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 0 毫秒
111.
Hachkevych  O. R.  Musii  R. S.  Stasyuk  H. B. 《Materials Science》2003,39(5):682-690
We determine the temperature fields and stresses formed in a long hollow conducting cylinder under the action of pulsed electromagnetic fields specified by the values of the axial component of the vector of intensity of a uniform magnetic field on the inner and outer surfaces. We consider the case where the electromagnetic action obeys the law of damped sinusoid on the inner and outer surfaces of the cylinder.  相似文献   
112.
Self-pulsation at 45 GHz repetition frequency has been demonstrated in 1.5 /spl mu/m monolithic single-section quantum dot Fabry-Perot semiconductor lasers without saturable absorber. The mode-beating exhibits a narrow linewidth below 100 kHz, demonstrating high phase correlation between these modes. Such modelocked lasers open ways to low timing-jitter components for clock recovery or millimetre-wave generation in wireless transmission applications.  相似文献   
113.
We study the degradation of the mechanical and corrosion properties of 17G1S steel in gas mains as a result of operation for 28–40 yr. We reveal the simultaneous decrease in its strength and hardness, on the one hand, and impact toughness and crack resistance, on the other hand. The indicated parameters prove to be most sensitive to the in-service degradation of the metal. The degradation of steel leads to the increase in the strain-hardening coefficient and the appearance of the yield plateau in the tensile stress-strain diagram and causes the appearance of sensitivity to hydrogen embrittlement increasing in the process of operation. We analyze the role of absorbed hydrogen affecting the mechanism of strain aging and responsible for the appearance of defects. It is shown that the polarization resistance can be used not only for monitoring of the corrosion state of gas pipelines but also for the prediction of changes in their mechanical properties in the process of operation. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 43, No. 5, pp. 97–104, September–October, 2007.  相似文献   
114.
115.
A rheological equation of state for wood which allows for the running values of its porosity and humidity is considered.  相似文献   
116.
Scanning and transmission electron microscopy have been combined with x-ray diffraction to examine the phase equilibria in the Al - Pd - Re system at 1000°C for compositions from 50 to 100 at.% Al, and the corresponding isothermal section has been constructed. The binary monoclinic Al3 Re phase has been observed for the first time. It is confirmed that there is a stable icosahedral phase in this system. The boundaries to its homogeneity region have been determined and the phase equilibria in which it participates.  相似文献   
117.
118.
Conclusions The chemical mutagenesis method is recommended for use in local purification installations for cleaning up of caprolactam-containing wastewater.Use of this method permits one to carry out a biochemical clean-up of wastewater having a caprolactam content up to 600 mg/liter while increasing the oxidative power of the aeration tank by a factor of two.Translated from Khimicheskie Volokna, No. 6, p. 46, November–December, 1985.  相似文献   
119.
Dynamic processes are studied in media with softly and hardly internal destroyable configurations. A method is examined for the measurement of properties of media with spatial separation of the chemical transformation stages and thermal hydrodynamic measurements.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 5, pp. 781–789, November, 1987.  相似文献   
120.
The results are presented of the fabrication of strain-relaxed graded Si1 − x Gex/Si(001) buffer layers with a maximum Ge fraction of about 0.25 that have a low density of threading dislocations (<106 cm−2) and low surface roughness. The buffer layers are grown by atmospheric-pressure hydride CVD. It is found that chemical mechanical polishing can reduce their surface roughness to a level comparable with that of the original Si(001) substrates. It is shown that the polished buffer layers can serve as substrates for MBE-grown SiGe/Si heterostructures.__________Translated from Mikroelektronika, Vol. 34, No. 4, 2005, pp. 243–250.Original Russian Text Copyright © 2005 by Vostokov, Drozdov, Krasil’nik, Kuznetsov, Novikov, Perevoshchikov, Shaleev.  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