全文获取类型
收费全文 | 45187篇 |
免费 | 3231篇 |
国内免费 | 1976篇 |
专业分类
电工技术 | 653篇 |
技术理论 | 1篇 |
综合类 | 2886篇 |
化学工业 | 24705篇 |
金属工艺 | 1617篇 |
机械仪表 | 801篇 |
建筑科学 | 317篇 |
矿业工程 | 395篇 |
能源动力 | 1126篇 |
轻工业 | 1550篇 |
水利工程 | 59篇 |
石油天然气 | 5136篇 |
武器工业 | 439篇 |
无线电 | 1885篇 |
一般工业技术 | 5475篇 |
冶金工业 | 1057篇 |
原子能技术 | 202篇 |
自动化技术 | 2090篇 |
出版年
2024年 | 94篇 |
2023年 | 494篇 |
2022年 | 812篇 |
2021年 | 1061篇 |
2020年 | 1036篇 |
2019年 | 988篇 |
2018年 | 990篇 |
2017年 | 1098篇 |
2016年 | 1384篇 |
2015年 | 1359篇 |
2014年 | 2189篇 |
2013年 | 2249篇 |
2012年 | 2863篇 |
2011年 | 3359篇 |
2010年 | 2596篇 |
2009年 | 2813篇 |
2008年 | 2480篇 |
2007年 | 3104篇 |
2006年 | 2858篇 |
2005年 | 2600篇 |
2004年 | 2206篇 |
2003年 | 2088篇 |
2002年 | 1807篇 |
2001年 | 1551篇 |
2000年 | 1339篇 |
1999年 | 1064篇 |
1998年 | 878篇 |
1997年 | 626篇 |
1996年 | 541篇 |
1995年 | 407篇 |
1994年 | 351篇 |
1993年 | 278篇 |
1992年 | 227篇 |
1991年 | 146篇 |
1990年 | 125篇 |
1989年 | 65篇 |
1988年 | 51篇 |
1987年 | 38篇 |
1986年 | 22篇 |
1985年 | 27篇 |
1984年 | 32篇 |
1983年 | 17篇 |
1982年 | 15篇 |
1981年 | 12篇 |
1980年 | 8篇 |
1979年 | 15篇 |
1978年 | 9篇 |
1977年 | 5篇 |
1975年 | 2篇 |
1951年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
K Madhusudan Reddy Sunkara V Manorama R.D.K Misra 《Materials Research Bulletin》2004,39(10):1491-1498
A comparative study of gas sensing behavior of nanocrystalline nickel ferrite synthesized by micro-emulsion and hydrothermal method to liquefied petroleum gas (LPG) is presented. Nanocrystalline nickel ferrite synthesized by hydrothermal method indicated higher electrical conductivity and gas sensitivity at low operating temperature compared to nanocrystalline nickel ferrite synthesized by reverse micelle technique. This difference in the gas sensing behavior can be attributed to the presence of more oxygen vacancies (i.e. non-stoichiometry) in the hydrothermally synthesized nickel ferrite. Incorporation of palladium had a catalytic effect and the operating temperature was significantly reduced in both the samples. The higher operating temperature of the reverse micelle nickel ferrite material makes the sensor response speed faster (∼10 s) compared to the hydrothermally synthesized material (∼1 min). 相似文献
102.
The thick film of Zn-Sb-O was prepared by coating the paste of nanoparticles mixture (Sb2O3:ZnO=1:3) on the alumina substrate, followed by sintering at 500-900 °C for 2 h in air. The electrical resistance and gas-sensing properties to benzene, alcohol and acetone of Zn-Sb-O films were found to be dependent on the change of phase structure caused by sintering temperature. 相似文献
103.
G. N. Churilov R. B. Weisman N. V. Bulina N. G. Vnukova A. P. Puzir L. A. Solovyov S. M. Bachilo D. A. Tsyboulski G. A. Glushenko 《Fullerenes, Nanotubes and Carbon Nanostructures》2003,11(4):371-382
The addition of metallic Ir and Pt to a fullerene-forming, atmospheric-pressure plasma reactor was found to influence the generation of carbonaceous products. It was observed that the added metals were efficiently dispersed into the plasma and that their presence increased the yield of fullerenes. The addition of Ir led to a noticeable shift in the fullerene distribution towards C60, whereas the addition of Pt increased the proportion of C60 oxides and decreased the proportion of higher fullerenes. Addition of Ir also caused a reduction of the soot particle size and the formation of a considerable quantity of carbon nanotubes. 相似文献
104.
高纯铝箔通常通过电化学扩面后用作铝电解电容器的阳极材料。利用铝箔(100)面隧道孔制备纳米模板。这种纳米模板的特点是制作简单、模板面积大,纳米阵列材料形状可控性强。还利用两步电化学侵蚀铝箔的特殊工艺,研制出纵横交错的TiO2纳米有序阵列材料。 相似文献
105.
Lei Liu Ying Kong Hong Xu Jin P. Li Jin X. Dong Zhi Lin 《Microporous and mesoporous materials》2008,115(3):624-628
A three-dimensional zinc phosphate compound with DFT topology, designated as ZnPO4-EU1, has been synthesized by an ionothermal approach from the system HF-ZnO–P2O5-choline chloride-imidazolidone. Ethylenediamine, derived from decomposition of the imidazolidone component of the deep-eutectic solvent (DES) itself, is delivered to the synthesis and serves as an appropriate template for ZnPO4-EU1. Experiments in which the synthesis conditions were varied showed that ZnPO4-EU1 may be prepared over a wide molar ratio of P/Zn = 0.55–13.0. Powder X-ray diffraction patterns have been obtained at intervals to track the crystallization process of this material. The experimental data show that Zn3(PO4)2 · 4H2O (a dense phase) was first isolated from the DES after reaction for 1 h. Subsequently, the pure phase of ZnPO4-EU1 was obtained with increasing crystallization time from 12 h to 72 h. The experimental results show that the nucleation and crystallization take place with relatively low levels of solvent degradation, demonstrating that zinc phosphate with a three-dimensional framework can be synthesized by in situ generation of an appropriate template using an unstable DES at high temperatures (150–200 °C). 相似文献
106.
多测井曲线的综合处理合成 总被引:9,自引:0,他引:9
测井曲线是地质分层的基础,但在利用单一测井曲线解决复杂地质问题时也存在多解性和局限性。为克服多解性,人们采用多种测井曲线进行地质分层,提高了分层的精度。本文在此基础上提出把多条曲线分别赋予不同的加权因子,然后进行归一化处理,形成一条标准综合参数测井曲线。此综合参数曲线突出了所选的多条测井曲线的公共信息,减少或削弱了单一测井曲线中的偶然误差,提高了综合后测井资料的可信度。该方法可应用于地质分层、岩性分析、含油气预测等诸多领域。应用时要注意,并非所选择的测井曲线种类越多越好,而是要选择那些最能反映地层单元特征信息的测井曲线。 相似文献
107.
The present study presents the synthesis of unsaturated polyester resins using only one glycol i.e., ethylene glycol. Polyesters of inorganic solubility in styrene were prepared. Properties of the resins in the noncrosslinked state in the process of crosslinking and after curing were studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3143–3150, 2006 相似文献
108.
Calculations and detailed first principle and thermodynamic analyses have been performed to understand the formation mechanism of K2Ti6O13 nanowires (NWs) by a hydrothermal reaction between bulk Na2Ti3O7 crystals and a KOH solution. It is found that direct ion exchange between K+ and Na+ plus H+ interactions with [TiO6] octahedra in Na2Ti3O7 promote the formation of an intermediate H2K2Ti6O14 phase. The large lattice mismatch between this intermediate phase and the bulk Na2Ti3O7 structure, and the large energy reduction associated with the formation of this intermediate phase, drive the splitting of the bulk crystal into H2K2Ti6O14 NWs. However, these NWs are not stable because of large [TiO6] octahedra distortion and are subject to a dehydration process, which results in uniform K2Ti6O13 NWs with narrowly distributed diameters of around 10 nm. 相似文献
109.
对重油催化裂化过程中的环境影响因素、硫分布状况及硫平衡等进行了分析,指出了重油催化裂化过程中的环境污染问题;从对装置污染源的分析出发,提出了相关的治理措施。 相似文献
110.