全文获取类型
收费全文 | 19940篇 |
免费 | 1863篇 |
国内免费 | 642篇 |
专业分类
电工技术 | 363篇 |
综合类 | 857篇 |
化学工业 | 8191篇 |
金属工艺 | 1173篇 |
机械仪表 | 286篇 |
建筑科学 | 582篇 |
矿业工程 | 412篇 |
能源动力 | 362篇 |
轻工业 | 5206篇 |
水利工程 | 52篇 |
石油天然气 | 614篇 |
武器工业 | 54篇 |
无线电 | 600篇 |
一般工业技术 | 2210篇 |
冶金工业 | 1148篇 |
原子能技术 | 174篇 |
自动化技术 | 161篇 |
出版年
2024年 | 130篇 |
2023年 | 394篇 |
2022年 | 586篇 |
2021年 | 796篇 |
2020年 | 679篇 |
2019年 | 708篇 |
2018年 | 688篇 |
2017年 | 868篇 |
2016年 | 908篇 |
2015年 | 758篇 |
2014年 | 989篇 |
2013年 | 1290篇 |
2012年 | 1271篇 |
2011年 | 1560篇 |
2010年 | 1041篇 |
2009年 | 1043篇 |
2008年 | 932篇 |
2007年 | 1039篇 |
2006年 | 933篇 |
2005年 | 738篇 |
2004年 | 688篇 |
2003年 | 677篇 |
2002年 | 628篇 |
2001年 | 460篇 |
2000年 | 424篇 |
1999年 | 348篇 |
1998年 | 318篇 |
1997年 | 235篇 |
1996年 | 186篇 |
1995年 | 191篇 |
1994年 | 145篇 |
1993年 | 120篇 |
1992年 | 114篇 |
1991年 | 102篇 |
1990年 | 90篇 |
1989年 | 41篇 |
1988年 | 38篇 |
1987年 | 43篇 |
1986年 | 33篇 |
1985年 | 35篇 |
1984年 | 43篇 |
1983年 | 24篇 |
1982年 | 41篇 |
1981年 | 9篇 |
1980年 | 21篇 |
1979年 | 5篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1975年 | 9篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Use of the Retarded Solution-Reprecipitation Process to Attain a Higher Initial Permeability in MnZn Ferrites 总被引:1,自引:0,他引:1
Miha Drofenik rej nidari Darko Makovec 《Journal of the American Ceramic Society》2003,86(9):1601-1604
We investigated the effect of various amounts of liquid phase on microstructure development during sintering and the resulting magnetic permeability of MnZn ferrite (MZF) samples. Our results revealed that the microstructure and the final magnetic permeability depend on the thickness of the liquid-phase film during sintering. The solution-reprecipitation (S-R) process, which is associated with an intensive microstructure development in MZF, starts when a continuous liquid-phase film of critical thickness δo , which wets the MZF grains, is formed. The solid-state sintering that takes place before the formation of the continuous liquid-phase film is essential for the final microstructure of MZF. 相似文献
2.
Marcia Cristina Kaezer Fran a Rosane Aguiar da Silva San Gil Jean-Guillaume Eon 《Catalysis Today》2003,78(1-4):105-115
γ-Al2O3 supported vanadium oxides were modified by tungsten and molybdenum oxides in order to improve dispersion and selectivity towards olefins in propane oxidative dehydrogenation (ODH). Both vanadium–tungsten and vanadium–molybdenum catalysts were obtained by adsorption of mixed isopolyanions (VW5O195−, V2W4O194−, VMo5O195− and V2Mo4O194−) from aqueous solutions. The isopolyanion solutions were characterized by UV-Vis and 51V NMR spectroscopy. Vanadium, vanadium–tungsten and vanadium–molybdenum precursors and catalysts were also characterized by UV-Vis (diffuse reflectance) and solid state 51V NMR spectroscopy. An improved selectivity to propene in the presence of tungsten and molybdenum in VOx/γ-Al2O3 was observed and attributed to dilution of vanadium by tungsten or molybdenum oxides on the γ-Al2O3 surface. 相似文献
3.
A.V. GomonnaiI.M. Voynarovych A.M. SolomonYu.M. Azhniuk A.A. KikineshiV.P. Pinzenik M. Kis-VargaL. Daroczy V.V. Lopushansky 《Materials Research Bulletin》2003,38(13):1767-1772
Lattice structure and rod-like shaped SbSI nanocrystals obtained by ball milling with rod thickness down to 70 nm, as estimated from X-ray diffraction (XRD) and electron microscopy, is similar to that of the bulk crystals. The dependence of the grain size on the milling duration is discussed in view of the chain-like crystalline structure of SbSI. Possible factors, responsible for the observed Raman line broadening, are discussed, scattering by surface phonons being considered the predominant one. 相似文献
4.
5.
本文运用一典型的人工神经网络模型─“反向传播”模型,对高氧化态(Ⅱ─Ⅳ)三核金属簇合物的构型分布进行了分析,得到了较好的分类、预报结果为化合物结构分析提供了新的工具。 相似文献
6.
JFC磷酸酯的合成和应用 总被引:2,自引:0,他引:2
详述了JFC磷酸酯的合成工艺路线,以及它在织物前处理精练工艺中的应用。与其它磷酸酯类精练剂性能对比,证明它可作为一种性能优良的精练剂中的添加剂。 相似文献
7.
ABSTRACT: The traditional small-scale production of boucané, a cured smoked pork-belly product from Réunion, involves several unit operations that are performed in a single step. The aim of this study was to highligh the impact of 4 unit operations (salting, drying, cooking, and smoking) on stability, color, and flavor development in processed pork. These characateristics are the 3 main criteria of boucané's quality. Mass transfer, color, and volatile compounds were measured, analyzed, and compared in 4 products. Results indicated that a major quantity of volatile compounds detected in the processed meat were derived from the smoking process. Color variations were mainly explained by muscle pigment modification due to the cooking process, and by the input of volatile compounds of smoke. 相似文献
8.
简述国内磷酸二铵的建设情况及不同的生产工艺、原有磷酸二铵装置改造选用的工艺及生产情况 ,重点介绍 Incro工艺在云南红河州磷肥厂年产 12万吨磷铵装置中的改造情况 ,经过比较认为原采用预中和槽流程磷酸二铵装置增产改造时选用 Incro工艺比较合适 相似文献
9.
TeMxMo1.7O mixed oxides (M = V and/or Nb; x = 0-1.7) have been prepared by calcination of the corresponding salts at 600 °C in an atmosphere of N2. A new crystalline phase, with a Te/V/Mo atomic ratio of 1/0.2-1.5/1.7, has been isolated and characterised by XRD and IR spectroscopy. This phase is observed in the TeVMo or TeVNbMo mixed oxide but not in the TeNbMo mixed oxide. The new crystalline phase shows an XRD pattern similar to Sb4Mo10O31 and probably corresponds to the M1 phase recently proposed by Aouine et al. (Chem. Commun. 1180, 2001) to be present in the active and selective MoVTeNbO catalysts. Although these catalysts present a very low activity in the propane oxidation, they are active and selective in the oxidation of propene to acrolein and/or acrylic acid. However, the product distribution depends on the catalyst composition. Acrolein or acrylic acid can be selectively obtained from propene on Nb-free or Nb-containing TeVMo catalysts, respectively. The presence of both V and Nb, in addition to Mo and Te, appears to be important in the formation of acrylic acid from propene. 相似文献
10.
Significant increases in the activity of vanadium(III) amidinate catalysts for ethylene polymerization have been obtained by immobilization on a MgCl2‐based support prepared by reaction of AlEt3 with a MgCl2/ethanol adduct. Catalyst immobilization and activation on this type of support prevents the rapid decay in activity observed under homogeneous polymerization conditions with unsupported catalysts. Stable polymerization activity is also observed with analogous titanium(III) complexes. Polyethylene with narrow molecular weight distribution and spherical particle morphology is obtained without reactor fouling. Copyright © 2005 Society of Chemical Industry 相似文献