全文获取类型
收费全文 | 12954篇 |
免费 | 680篇 |
国内免费 | 464篇 |
专业分类
电工技术 | 137篇 |
技术理论 | 1篇 |
综合类 | 438篇 |
化学工业 | 1521篇 |
金属工艺 | 3362篇 |
机械仪表 | 564篇 |
建筑科学 | 1878篇 |
矿业工程 | 303篇 |
能源动力 | 389篇 |
轻工业 | 196篇 |
水利工程 | 53篇 |
石油天然气 | 222篇 |
武器工业 | 51篇 |
无线电 | 683篇 |
一般工业技术 | 1696篇 |
冶金工业 | 2301篇 |
原子能技术 | 98篇 |
自动化技术 | 205篇 |
出版年
2024年 | 20篇 |
2023年 | 182篇 |
2022年 | 223篇 |
2021年 | 274篇 |
2020年 | 327篇 |
2019年 | 216篇 |
2018年 | 246篇 |
2017年 | 255篇 |
2016年 | 364篇 |
2015年 | 388篇 |
2014年 | 595篇 |
2013年 | 718篇 |
2012年 | 810篇 |
2011年 | 1127篇 |
2010年 | 702篇 |
2009年 | 780篇 |
2008年 | 687篇 |
2007年 | 819篇 |
2006年 | 760篇 |
2005年 | 652篇 |
2004年 | 564篇 |
2003年 | 537篇 |
2002年 | 470篇 |
2001年 | 397篇 |
2000年 | 336篇 |
1999年 | 329篇 |
1998年 | 257篇 |
1997年 | 263篇 |
1996年 | 184篇 |
1995年 | 214篇 |
1994年 | 169篇 |
1993年 | 79篇 |
1992年 | 38篇 |
1991年 | 29篇 |
1990年 | 24篇 |
1989年 | 18篇 |
1988年 | 18篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980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
151.
采用离子束溅射沉积了不同厚度的Co膜和Cu膜,利用四电极法测量了薄膜的电阻率,从而得到了Co膜和Cu膜的电导率随薄膜厚度的变化关系。实验结果表明,Co膜和Cu膜的电学特性都具有明显的尺寸效应。比较了同时考虑表面散射和晶界散射的电导理论得到的电导率公式与实验结果,不同薄膜厚度电导率的理论结果与实验结果符合较好。提出了厚度作为金属薄膜生长从不连续膜进入连续膜的一个特征判据,并利用原子力显微镜(AFM)观测了膜厚在特征厚度附近的Co膜和Cu膜的表面形貌。 相似文献
152.
杭州湾跨海大桥钢管桩的涂层防护 总被引:3,自引:0,他引:3
杭州湾跨海大桥采用钢管桩沉桩基础。钢管桩的腐蚀问题采用涂层加阴极保护的防护体系,其中涂层部分采用单层/双层/三层重防腐环氧粉末喷涂防护方案解决。介绍了三种涂层结构及其用途。 相似文献
153.
In situ imaging techniques in conjunction with electrochemical measurements were used to study the behavior of steel surfaces in simple chloride solutions. The imaging method detected the presence of significantly thicker uniform layers than the original passive oxide. The layers were found to form in chloride after the steel was anodically polarized following reduction of the passive oxide film. The growth of the layer depended on the degree of prior passive oxide reduction. Formation of the layer was also sensitive to underlying structure and enabled rapid location of regions of higher corrosion rate across laser welds in steels. 相似文献
154.
化学镀Ni-Cu-P添加剂的研究 总被引:5,自引:0,他引:5
通过对化学镀Ni-Cu-P合金的稳定剂、表面活性剂、光亮剂对镀层性能及镀液稳定性的影响研究,得出最佳实验配方。 相似文献
155.
A. Amara A. Ferdi A. Drici J.C. Bernde M. Morsli M. Guerioune 《Catalysis Today》2006,113(3-4):251-256
Co-evaporation technique from three sources was used to prepare Cu(In, Ga)Se2 polycrystalline thin films for photovoltaic conversion. Their conductivity was studied in the range 20–300 K. The grain boundary scattering mechanism is mainly responsible for the diffusion process in the latter materials. In the low temperature region, we interpret the data in terms of Mott law and the analysis is very consistent with the variable range hopping. However, thermoionic emission is predominant at high temperatures. When the conductivity deviates from the classical grain boundary conduction models, inhomogeneity is then considered and parameters such as the standard deviation and the mean potential barrier height are derived. Transmittance measurements yielded band gap values of 1.07 and 1.64 eV for CuInSe2 and CuGaSe2, respectively. 相似文献
156.
LI Hongxia 《中国耐火材料》2006,15(1):3-8
This paper introduces the developing tendency of refractories for iron and steel industry combined with the new metallurgical techniques applied in iron and steel industry in China. Refractories for blast furnace long service life, smelting reduction iron-making process, secondary refining metallurgies and clean steel making, near net shape continuous casting are described respectively. To meet the requirement of iron and steel industry, the high quality, multi-functions and environment-friendly refractories with long service llfe will be focused and developed in the future. In addition, high grade refractories in China have great developing space and potential market. 相似文献
157.
158.
Polyaniline (PANi), poly(2-chloroaniline) (PClANi), and poly(aniline-co-2-chloroaniline) (co-PClANi) films were synthesized by electrochemical deposition on 304-stainless steel (SS) from an acetonitrile solution. The structural properties of these polymer films were characterized by spectroscopic (FTIR and UV–vis) and electrochemical (cyclic voltammetry) methods. Open circuit potential–time (Eocp–time) curves, potentiodynamic polarization, and electrochemical impedance (EIS) measurements showed that these films have significant protective performance against corrosion of SS in 0.5 M HCl solution. It was found that co-PClANi film has acted as a passivator as well as barrier for cathodic reduction reaction in a similar manner as PANi film. However, PClANi film has behaved only as barrier for corrosion protection of SS in 0.5 M HCl. 相似文献
159.
Vapor-Phase Alkylation of Toluene with Isopropanol over Mg/Al, Ni/Al and Cu/Al Hydrotalcites (Layered Double Hydroxide) 总被引:1,自引:0,他引:1
Vapor-phase isopropylation of toluene has been carried out over Mg/Al, Ni/Al and Cu/Al calcined hydrotalcites (CHTs). Reaction conditions were optimized for alkylation by varying temperature, weight hourly space velocity and reactant mole ratio. Side-chain alkylation is found to be more predominant than ring alkylation over Mg/Al CHT, while Ni/Al and Cu/Al CHTs favored ring alkylation. The main products were isobutylbenzene and cymene. The combined participation of acidic and basic sites of the materials is found to be crucial for both side-chain and ring alkylation of toluene with isopropanol. An X-ray diffraction pattern of the resulting oxide indicates a diffuse MgO structure. The incorporation of small amounts of Al3+ to MgO generates new surface Lewis acid--base pair sites. 相似文献
160.
NO
x
reduction with a combination of catalysts, Pd catalyst, NO
x
storage reduction (NSR) catalyst and Cu/ZSM-5 in turn, was investigated to elucidate for the high NO
x
reduction activity of this catalyst combination under oxidative atmosphere with periodic deep rich operation. The catalytic
activity was evaluated using the simulated exhaust gases with periodically fluctuation between oxidative and reductive atmospheres,
and it was found that the NO
x
reduction activity with this catalyst combination was apparently higher than that of the solely accumulation of these individual
activities, which was caused by the additional synergic effect by this combination. The Pd catalyst upstream of the NSR catalyst
improved NO
x
storage ability by NO2 formation under oxidative atmosphere. The stored NO
x
was reduced to NH3 on the NSR catalyst, and the generated NH3 was adsorbed on Cu/ZSM-5 downstream of the NSR catalyst under the reductive atmosphere, and subsequently reacted with NO
x
on the Cu/ZSM-5 under the oxidative atmosphere. 相似文献