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   334504篇
  免费   18016篇
  国内免费   338篇
电工技术   5074篇
综合类   235篇
化学工业   66995篇
金属工艺   16365篇
机械仪表   11770篇
建筑科学   7373篇
矿业工程   3887篇
能源动力   5832篇
轻工业   24803篇
水利工程   4849篇
石油天然气   13310篇
武器工业   35篇
无线电   28666篇
一般工业技术   81533篇
冶金工业   42917篇
原子能技术   11356篇
自动化技术   27858篇
  2021年   4591篇
  2020年   4682篇
  2019年   7032篇
  2018年   10073篇
  2017年   10613篇
  2016年   11542篇
  2015年   8080篇
  2014年   10740篇
  2013年   18702篇
  2012年   12965篇
  2011年   14145篇
  2010年   12171篇
  2009年   12645篇
  2008年   12194篇
  2007年   11516篇
  2006年   9348篇
  2005年   8087篇
  2004年   7837篇
  2003年   7640篇
  2002年   7241篇
  2001年   6680篇
  2000年   6588篇
  1999年   5371篇
  1998年   10500篇
  1997年   8005篇
  1996年   5857篇
  1995年   4517篇
  1994年   4102篇
  1993年   4313篇
  1992年   3482篇
  1991年   3619篇
  1990年   3676篇
  1989年   3581篇
  1988年   3497篇
  1987年   3453篇
  1986年   3328篇
  1985年   3502篇
  1984年   3419篇
  1983年   3277篇
  1982年   3148篇
  1981年   3207篇
  1980年   3258篇
  1979年   3341篇
  1978年   3576篇
  1977年   3743篇
  1976年   4519篇
  1975年   3269篇
  1974年   3346篇
  1973年   3425篇
  1972年   3011篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
971.
The results of the oxidation of carbon nanofibers and materials obtained on their basis are presented; these results demonstrate that the nanofibers were formed by carbon with different degrees of crystal structure ordering. The experimental data supported previous hypotheses that amorphous carbon results from the decomposition of metal carbides. The subsequent formation of spatial structures and the appearance of crystalline carbon species resulted from catalytic graphitization. It was demonstrated that sorbents can be prepared based on carbon nanofibers after pyrolytic consolidation followed by activation, and these sorbents are more effective than well-known sorbents.  相似文献   
972.
Impregnants prepared from shale phenols for cellular materials had a cohesive strength of 2.4–18.5 J/m2 and a specific elongation of 160–170%. The adhesive strength toward a metal was 3.5–6.0 J/m2; in the case of concrete, it was greater than the concrete strength.  相似文献   
973.
The results of investigation of the modification of the Armenian minerals with fluorine-containing oligomers show that a modified product appears when the mineral fillers are treated with fluoroalkanes. The product preserves the structure of the fillers with a “grafted” fluoroalkane layer in which chlorine atoms locate mainly over their periphery. The composite materials based on heterochained polymers and the modified fillers possess a stronger wear resistance and a low friction coefficient.  相似文献   
974.
The recent researches and technological developments of middle and long wavelength infrared HgCdTe photovoltaic detectors are presented. Structure, topology, design and performance of HgCdTe photodiodes, silicon readout electronics, Focal Plane Arrays both staring and time delay and integration types, thermal imagers are discussed. Negative differential conductance, bistability and high frequency oscillations under background infrared radiation in HgCdTe photodiodes are reported.  相似文献   
975.
The problem of synthesizing trajectories, planning and implementing the motion of a mobile robot is investigated. The statement of the problem is motivated by the need for designing an optimal control of robots with two wheels controlled independently. Mobile robots with this kinematic scheme are called robots with “differential drive.”  相似文献   
976.
This work characterized the elemental composition of the pigments used in decorative paintings from the sarcophagus cartonnage fragments of an Egyptian mummy, using μXRF with Synchrotron Radiation. This female mummy (n.158) is considered one of the most important pieces of the National Museum (Rio de Janeiro, Brazil) because of its unconventional embalming with legs and arms swathed separately. The measurements were performed at the XRF beamline D09B of the Brazilian Synchrotron Light Laboratory (LNLS), using white beam and a Si(Li) detector with resolution of 165 eV at 5.9 keV. The elements found in the samples were: Si, S, Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, As, Sr, Hg and Pb.  相似文献   
977.
The task of ascertaining minimal semantic-syntactic text units within the framework of the task of the semantic analysis of texts in the Russian language is considered. The use of the DSM-method for producing rules for ascertaining the meanings of syntaxemes is described, the setting of the goal of producing rules in DSM-method terminology is presented. The analysis of the results of computer experiments and the causes of the presence of contradictory rules are given.  相似文献   
978.
This article is devoted to work done in 2002–2006 as part of the unified project Reabilitatsiya to rehabilitate radiation hazardous objects and sections of the radioactively contaminated territory of the Russian Science Center Kurchatov Institute. The main objects of the rehabilitation work were old storage sites built for radioactive wastes on the territory of the Institute when military and civilian nuclear technologies were under development. The structural features of the storage sites, including the volumes and characteristics of the wastes stored, are presented. The salient aspects of the disposal sites, taken into account during the rehabilitation work, are discussed. The organization of the rehabilitation operations and the sequence in which they are performed, the special features of the technical design solutions used, the technological methods, and ways for conducting the work are described. __________ Translated from Atomnaya énergiya, Vol. 102, No. 5, pp. 300–306, May, 2007.  相似文献   
979.
The effect of tempering temperature on the structure, wear resistance, and corrosive properties of steel 08Kh14AN4MDB is studied. The results of mechanical and corrosion tests are used for constructing an optimization matrix for determining the optimum tempering temperature. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 29–32, February, 2007.  相似文献   
980.
The effect of the oxygen partial pressure on the spinodal decomposition in the Ba2YCu3O6—Ba2YCu3O7 system has been studied. A decrease in the oxygen partial pressure was found to increase the decomposition rate. The most probable cause of the effect consists in the decrease of oxygen concentration in the near-boundary regions of grains.  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