全文获取类型
收费全文 | 25354篇 |
免费 | 3343篇 |
国内免费 | 1194篇 |
专业分类
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 |
出版年
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
程里 《理化检验(物理分册)》2004,40(9):457-458
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.
Maher M. Osman Mounir M. Abd El-Malek Aida B. Tadros Atef M. Michael 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,62(1):46-52
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
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.
Marina Fomina Geoffrey M Gadd 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2003,78(1):23-34
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.
J. Weise Dr.‐Ing. O. Yezerska M. Busse M. Haesche V. Zanetti‐Bueckmann M. Schmitt 《Materialwissenschaft und Werkstofftechnik》2007,38(11):901-906
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