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   25354篇
  免费   3343篇
  国内免费   1194篇
电工技术   815篇
综合类   1465篇
化学工业   5577篇
金属工艺   4605篇
机械仪表   1744篇
建筑科学   878篇
矿业工程   1018篇
能源动力   942篇
轻工业   1141篇
水利工程   280篇
石油天然气   743篇
武器工业   184篇
无线电   2253篇
一般工业技术   4846篇
冶金工业   2668篇
原子能技术   292篇
自动化技术   440篇
  2024年   137篇
  2023年   819篇
  2022年   763篇
  2021年   1050篇
  2020年   1169篇
  2019年   1127篇
  2018年   886篇
  2017年   1033篇
  2016年   931篇
  2015年   936篇
  2014年   1334篇
  2013年   1535篇
  2012年   1582篇
  2011年   1595篇
  2010年   1153篇
  2009年   1250篇
  2008年   1118篇
  2007年   1463篇
  2006年   1434篇
  2005年   1334篇
  2004年   1049篇
  2003年   1121篇
  2002年   886篇
  2001年   732篇
  2000年   693篇
  1999年   529篇
  1998年   452篇
  1997年   328篇
  1996年   304篇
  1995年   233篇
  1994年   202篇
  1993年   159篇
  1992年   122篇
  1991年   98篇
  1990年   84篇
  1989年   74篇
  1988年   40篇
  1987年   24篇
  1986年   19篇
  1985年   21篇
  1984年   18篇
  1983年   18篇
  1982年   11篇
  1981年   4篇
  1980年   3篇
  1979年   2篇
  1978年   2篇
  1977年   4篇
  1975年   4篇
  1951年   5篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
1.
2.
大型连杆流线简易试验方法   总被引:1,自引:1,他引:0  
介绍了一种大型连杆流线的简易试验方法及其评价原则。该方法可清晰显示流线,并适合任何尺寸和形状的锻造连杆的流线试验。  相似文献   
3.
4-Amino-3-thio-1,24-triazolidine (L1) and 4-amino-5-thio-1,3,4-thiadiazole (LII) as well as their metal complexes of the general formulae MLI·2H2O and MLIICl (M; Pb(II), Cd(II) and Zn(II)) were prepared. With Sn(II), we obtained Sn(LI)2·2H2O and SnLIICl, respectively. The structures of the compounds were identified through elemental analysis, and IR and UV spectra measurements, in addition to thermal analysis in case of the metal complexes. The antifouling properties of the compounds were tested by their incorporation into paint formulations which were applied to PVC substrates and tested in water from Alexandria western harbour. When the compounds were added at 17·5% by volume, the coated panels were fouled after 3 months of immersion. The addition of 6·7% by volume of tributyltin oxide to 15·8% of the prepared compounds in one formulation elevated the paint efficiency and prevented fouling for 11 months. Paint containing solely tributyltin oxide at the same concentration was inactive against algae.  相似文献   
4.
磷矿中七种金属元素的光谱法测定   总被引:2,自引:0,他引:2  
陈名樑 《山西冶金》2004,27(1):36-37
研究了磷矿样品中7种金属元素锰、钴、镍,锌、铬、钼及铋的分析方法,选择了灵敏度高干扰少的谱线,绘制出工作曲线,对样品进行了科学处理,不必进行化学分离即可对七种元素同时测定,经合成样分析、回收实验及样品测定,证明此方法精确可靠,其回收率在98%-102%之间。  相似文献   
5.
本文分析了锌基合金模具制造及使用过程中容易出现热裂、翘曲、收缩的问题,并提出了解决这些问题的措施。  相似文献   
6.
The sorption of toxic metals by fungal mycelia grown in clay‐containing medium is reported in this work. Biomass of melanin‐producing microfungi of the genus Cladosporium (C cladosporioides, C resinae and C herbarum) and Aureobasidium pullulans, clay minerals and fungal mycelia grown in clay‐containing medium were compared for their equilibrium Cu and Cd uptake from pH‐buffered solutions using experimental sorption isotherms. Bentonite (Cherkassy) in the natural form was shown to be the best Cu sorbent compared with the other clays and clay minerals tested. Cu sorption isotherms fitted the Langmuir sorption model for all cases. Comparison of Cu and Cd uptake for biomass and bentonite showed a lower biomass uptake capacity but a considerably higher affinity of the biosorbent for the solute. The presence of kaolinite and palygorskite in the medium generally reduced both Cu and Cd sorption capacity and the metal‐binding ability of the fungal–clay mixtures. In contrast, addition of bentonite into the medium did not appreciably alter the Cd sorption ability but increased the sorption of Cu by A pullulans and C cladosporioides grown in this medium. A common feature for all fungi grown in the presence of bentonite was an increase in the Cu sorption capacity (Qmax) of the biomineral sorbents and a reduction in their affinity (Langmuir parameter b) compared with control biomass. A difference between predicted and experimental data obtained for biomass grown on bentonite medium was also observed. The connection between the sorption capacity of biomass grown in clay‐containing medium, mycelial morphology and the structure of fungal pellets is discussed and a mechanism for the changed sorption capacity of the combined biomineral sorbents is proposed which involves blocking or modification of binding sites on biotic and abiotic components of the ‘biomineral’ association. © 2002 Society of Chemical Industry  相似文献   
7.
Micro‐porous syntactic foams were produced by means of integration of glass bubbles into aluminium and zinc matrices. Preforms of glass bubbles were pressure infiltrated with the alloys AlSi9Cu9 ans ZnAl4Cu using squeeze casting. The preforms were sintered thermically without the use of bonding agents. Using the combination of different sintering steps syntactic foams with locally different densities could be produced. The mechanical properties of the foams were tested indicating a high compression strength of the foams and a very good compression energy absorption. Furthermore, corrosion behaviour and behaviour at higher temperatures were investigated.  相似文献   
8.
A number of copolymers were synthesised by condensing the 2,4-dinitrophenylhydrazone of resacetophenone with substituted benzoic acids/ phenols and formaldehyde in the presence of sodium hydroxide or hydrochloric acid. The decomposition temperature, solubility and viscosity of the polymers have been determined. The ion-exchange properties have been studied by using a batch equilibrium method. The distribution of a number of metal ions between an aqueous solution and the resin have been measured. A wide range of pH and variable ionic strengths have been investigated.  相似文献   
9.
10.
为了继承和发扬错金工艺,从其定义出发,探讨了该工艺在中国古代及国外的发展与应用以及笔者对该工艺的实验研究。针对在错金工艺实践过程中出现的问题,在查阅了相关的资料后,对传统错金工艺的实现方法提出了质疑。  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