全文获取类型
收费全文 | 12648篇 |
免费 | 901篇 |
国内免费 | 918篇 |
专业分类
电工技术 | 503篇 |
综合类 | 590篇 |
化学工业 | 2607篇 |
金属工艺 | 3385篇 |
机械仪表 | 386篇 |
建筑科学 | 82篇 |
矿业工程 | 300篇 |
能源动力 | 1076篇 |
轻工业 | 176篇 |
水利工程 | 15篇 |
石油天然气 | 286篇 |
武器工业 | 93篇 |
无线电 | 1192篇 |
一般工业技术 | 2324篇 |
冶金工业 | 1007篇 |
原子能技术 | 177篇 |
自动化技术 | 268篇 |
出版年
2024年 | 42篇 |
2023年 | 287篇 |
2022年 | 326篇 |
2021年 | 429篇 |
2020年 | 485篇 |
2019年 | 417篇 |
2018年 | 368篇 |
2017年 | 418篇 |
2016年 | 423篇 |
2015年 | 454篇 |
2014年 | 630篇 |
2013年 | 702篇 |
2012年 | 759篇 |
2011年 | 890篇 |
2010年 | 653篇 |
2009年 | 779篇 |
2008年 | 684篇 |
2007年 | 807篇 |
2006年 | 710篇 |
2005年 | 571篇 |
2004年 | 477篇 |
2003年 | 490篇 |
2002年 | 513篇 |
2001年 | 443篇 |
2000年 | 378篇 |
1999年 | 308篇 |
1998年 | 204篇 |
1997年 | 228篇 |
1996年 | 152篇 |
1995年 | 101篇 |
1994年 | 102篇 |
1993年 | 50篇 |
1992年 | 45篇 |
1991年 | 36篇 |
1990年 | 31篇 |
1989年 | 23篇 |
1988年 | 20篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1975年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
介绍了高可靠电镀Ni/Au工艺在PTFE微波印制电路上的应用,并分析了氨基磺酸盐镀软镍和亚硫酸盐镀软金工艺的影响因素及提高Ni/Au镀层之间附着力的措施。通过实验及应用证明了与直接镀金工艺相比,在软基材PTFE敷铜箔板上镀Ni/Au工艺能大大提高微波电路的可焊性,高温稳定性和长期可靠性,并且用其所制作的微波器件的高频性能也优于直接镀金工业。 相似文献
13.
The partial oxidation of methanol to formaldehyde was studied over YBa2Cu3O7-x catalyst in a flow reactor. The structural change of YBa2Cu3O7-x before and after the reaction was measured by means of XRD and iodometric titration method. The catalytic characteristics
of YBa2Cu3O7-x for the partial oxidation of methanol to formaldehyde was due to copper ions. It was found that Cu+2 was responsible for the higher selectivity for formaldehyde. 相似文献
14.
将空气中烧成的镍导体用于散热制冷片制作工艺中,可降低成本,提高合格率。通过实验得到的最佳值为:镍导体中4号玻璃(SiO2>30,B2O3>10,PbO<55,TiO2少许)的含量4.5%,化学镀镍时间50min,方阻47.5mΩ/□,附着力8.1N/mm2。 相似文献
15.
Songping Wu 《Materials Letters》2007,61(16):3526-3530
In this paper, non-agglomerated monodispersed ultra-fine copper metallic powders have been synthesized with chemical reduction method. Fine lead-free glass powders were also prepared by solid synthesis process. Thick film paste prepared by above-mentioned copper metallic powders and lead-free glass powders was applied as conductive paste of MLCC. Mixture of glass and zinc oxide give the thick film a high adhesion strength which is attributed to the rough interface from interfacial reaction between glass and chip, and a good densification. Diffusion of metal between copper thick film and nickel thick film is clear. Ni-Cu solid solution appears under high temperature firing. 相似文献
16.
17.
Magnesiumandmagnesiumalloyshavebeenin vestigatedashydrogenstoragematerialsforseveralde cadesbecausefarmorehydrogenbyweightcanbestoredinthemthaninmostoftheothercurrentlyknownhydrogenstoragealloys .Moreover ,thehighnaturalabundanceofMg ,itslightmassandenviron mentalcompatibilitypotentiallymakemagnesiumoneofthemostprospectivecandidatesforfuturehydrogenstoragematerials .Unfortunately ,thepracticalappli cationofMganditsalloyshasbeenlimitedonlytocertainstoragedevicebecauseoftheirpoorhydriding dehydr… 相似文献
18.
Two-phase (B2+L12) nickel aluminide intermetallic compounds were synthesized by the pressure-assisted volume combustion synthesis (CS). The production and characterization of the samples containing NiAl+Ni3Al were investigated. Aluminum (99% pure, 15 μm) and carbonyl nickel (99.8 pure, 4-7 μm) powders were used. The production of intermetallic compound was carried out at 1050 °C under 150 MPa uniaxial pressure in open air atmosphere in an electrical resistance furnace for 60 min. The formation temperature of intermetallic compound was determined by differential scanning calorimeter (DSC) analysis, and exothermic temperature of powder mixture was determined as 653 °C. The characterization of samples was confirmed by optical microscope, SEM and XRD analysis. It was observed that the structure of compound has very low porosity and the formation of NiAl was completed successfully. The relative density of test materials measured according to Archimedes’ principle was 98.04%. The microhardness of test materials was about 351 HVN1. 相似文献
19.
The removal of Cu(II) by adsorption on fly ash has been found to be concentration, pH and temperature dependent. The kinetics of adsorption indicates the process to be diffusion controlled. The Langmuir constants have been calculated at different temperatures, and the adsorption has been found to be endothermic (ΔH = 15.652 kcal mol?1). The maximum removal is observed at pH 8.0, and variation in adsorption with pH has been explained on the basis of surface ionisation and complexation. 相似文献
20.
A semi-empirical mathematical model for the acid-oxygen pressure leaching of Ni–Cu matte is presented, based on data from batch leaching experiments. The primary controlling factor in the leaching process is found to be galvanic inhibition of the more highly oxidized copper and nickel sulfide species by less oxidized species, particularly Ni alloy and Ni3S2. The leaching rate of many species is greatly reduced by the presence of one or both of these phases, and others will not commence leaching until neither is present. The mathematical model is based on first-order chemical reaction controlled rate expressions, as the reactions occurring are electrochemical in nature. Mass transfer effects are included only empirically. Some possibly diffusion-related phenomena are noted, although the model is not extended to incorporate these effects on a fundamental level. The model is verified and extended by the inclusion of several different factors that were tested experimentally. The effects of variations in O2 flow rate and partial pressure, initial particle size, reaction pulp density and initial acid concentration were all studied, and included in the model. Variations in O2 flow rate and partial pressure are found to affect the reaction rates via the dissolved oxygen concentration in the solution phase. 相似文献