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   411984篇
  免费   4907篇
  国内免费   1708篇
电工技术   6888篇
综合类   2869篇
化学工业   58095篇
金属工艺   20538篇
机械仪表   16141篇
建筑科学   9703篇
矿业工程   2734篇
能源动力   8749篇
轻工业   26484篇
水利工程   4854篇
石油天然气   7353篇
武器工业   43篇
无线电   47141篇
一般工业技术   86061篇
冶金工业   57740篇
原子能技术   8618篇
自动化技术   54588篇
  2021年   2398篇
  2020年   1812篇
  2019年   2242篇
  2018年   22696篇
  2017年   22288篇
  2016年   16174篇
  2015年   3690篇
  2014年   4948篇
  2013年   12650篇
  2012年   12056篇
  2011年   24735篇
  2010年   21157篇
  2009年   19293篇
  2008年   20261篇
  2007年   22608篇
  2006年   8223篇
  2005年   11519篇
  2004年   9853篇
  2003年   9375篇
  2002年   7815篇
  2001年   7045篇
  2000年   6831篇
  1999年   6911篇
  1998年   16422篇
  1997年   11683篇
  1996年   9045篇
  1995年   6912篇
  1994年   6091篇
  1993年   6127篇
  1992年   4460篇
  1991年   4258篇
  1990年   4091篇
  1989年   4067篇
  1988年   3775篇
  1987年   3403篇
  1986年   3404篇
  1985年   3752篇
  1984年   3467篇
  1983年   3223篇
  1982年   3028篇
  1981年   3043篇
  1980年   3039篇
  1979年   2831篇
  1978年   2871篇
  1977年   3143篇
  1976年   4099篇
  1975年   2420篇
  1974年   2381篇
  1973年   2398篇
  1972年   2022篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
Polymer Bulletin - Jute and glass composites of epoxy resin of (2E, 6E)-bis(4-hydroxybenzylidene)cyclohexanone (EBHBC) were prepared by compressing molding technique using three different hardeners...  相似文献   
152.
Equipment of the Krasnoyarsk HPP is considered as an example to analyze the dependence of crack formation in runner blades on the operating conditions of t  相似文献   
153.
154.
The heat capacity of ytterbium orthovanadate was first measured by adiabatic calorimetry in the temperature range T?=?12.28–344.06?K. No obvious anomalies were observed on the curve obtained. The values of standard thermodynamic functions in the temperature range T?=?0–400 K were calculated. Based on low-temperature calorimetry data obtained, previously published data on the high-temperature heat capacity of ytterbium orthovanadate were corrected. The anomalous contribution to heat capacity for YbVO4 was compared with the data known for YbPO4.  相似文献   
155.
156.
The influence of the temperature gradient over the thickness of the cladding of a fuel element of a fast-neutron reactor on the migration of point defects formed in the cladding material due to neutron irradiation has been studied. It has been shown that, under the action of the temperature gradient, the flux of vacancies onto the inner surface of the cladding is higher than the flux of interstitial atoms, which leads to the formation of a specific concentration profile in the cladding with a vacancy-depleted zone near the inner surface. The experimental results on the spatial distribution of pores over the cladding thickness have been presented with which the data on the concentration profiles and vacancy fluxes have been compared.  相似文献   
157.
The Raman spectrum of water adsorbed on a metallic silver surface reveals an anomalously large shift of the vibrational frequency as compared to that in the bulk. The results are compared to data reported by other researchers, and possible interpretations of the observed phenomenon are discussed.  相似文献   
158.
The behavior of a superelastic Cu?14.2% Al?4%Ni single crystal in the case of high reversible strains under a longitudinal bending force was investigated. The effect of strain confinement along the crystal length was revealed and studied. The highest reversible strains (up to 10%) were shown to be confined within the central part of the bent crystal.  相似文献   
159.
X-ray diffraction analysis has been used to study the structure of the α-Zr matrix phase and the precipitation of β-Nb particles upon the annealing of a Zr–2.5% Nb deformed alloy. It has been found that the process of the precipitation of the strengthening β-Nb particles in the alloy is accompanied by the appearance of fields of elastic interphase deformations in the matrix α phase of the alloy due to the difference in the specific atomic volumes of the crystal structures of the matrix and precipitated phases. It has been shown experimentally that, as a result of the presence of interphase deformations in the alloy, the bcc crystal structure of the precipitating β-Nb particles undergoes monoclinic distortions.  相似文献   
160.
Over the last decade there has been much interest in the applications of diglycolamide (DGA) ligands for the extraction of the trivalent lanthanide and actinide ions from PUREX high active raffinates or dissolved spent nuclear fuel. Of the DGAs, the N,N,N’,N’-tetraoctyldiglycolamide (TODGA) is the best known and most widely studied. A number of new actinide separation processes have been proposed based on extraction with TODGA. This review covers TODGA-based processes and extraction data, specifically focusing on how phase modifiers have been used to increase metal loading and thus enhance the operating process envelopes. Effects of third phase formation and the organic phase speciation are reviewed in this context. Relevant aspects of the extraction chemistry of important solvents (TODGA-modifier-diluent combinations) are described and their performances demonstrated by a consideration of the published flowsheet tests. It is seen that modifiers are successfully enabling the use of TODGA in actinide separation processes but to date the identification and testing of suitable modifiers has been rather empirical. There is a growing understanding of the fundamental chemistry occurring in the organic phase and how that affects extractant speciation and metal loading capacity but studies are still needed if TODGA-based flowsheets are to become an industrially deployable option for minor actinide (MA) recovery processes.  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