全文获取类型
收费全文 | 122606篇 |
免费 | 4920篇 |
国内免费 | 2314篇 |
专业分类
电工技术 | 3219篇 |
技术理论 | 3篇 |
综合类 | 4930篇 |
化学工业 | 17810篇 |
金属工艺 | 6930篇 |
机械仪表 | 5395篇 |
建筑科学 | 5098篇 |
矿业工程 | 1691篇 |
能源动力 | 2196篇 |
轻工业 | 6158篇 |
水利工程 | 2035篇 |
石油天然气 | 2839篇 |
武器工业 | 380篇 |
无线电 | 14021篇 |
一般工业技术 | 20831篇 |
冶金工业 | 4378篇 |
原子能技术 | 653篇 |
自动化技术 | 31273篇 |
出版年
2024年 | 239篇 |
2023年 | 827篇 |
2022年 | 1510篇 |
2021年 | 2050篇 |
2020年 | 1521篇 |
2019年 | 1149篇 |
2018年 | 15618篇 |
2017年 | 14657篇 |
2016年 | 11044篇 |
2015年 | 2262篇 |
2014年 | 2368篇 |
2013年 | 2586篇 |
2012年 | 5822篇 |
2011年 | 12258篇 |
2010年 | 10810篇 |
2009年 | 7654篇 |
2008年 | 9036篇 |
2007年 | 9783篇 |
2006年 | 2113篇 |
2005年 | 2935篇 |
2004年 | 2244篇 |
2003年 | 2121篇 |
2002年 | 1455篇 |
2001年 | 895篇 |
2000年 | 969篇 |
1999年 | 1015篇 |
1998年 | 806篇 |
1997年 | 619篇 |
1996年 | 607篇 |
1995年 | 477篇 |
1994年 | 402篇 |
1993年 | 269篇 |
1992年 | 248篇 |
1991年 | 197篇 |
1990年 | 129篇 |
1989年 | 99篇 |
1988年 | 95篇 |
1987年 | 52篇 |
1986年 | 47篇 |
1985年 | 37篇 |
1968年 | 45篇 |
1967年 | 34篇 |
1966年 | 44篇 |
1965年 | 44篇 |
1959年 | 38篇 |
1958年 | 37篇 |
1957年 | 36篇 |
1956年 | 34篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
971.
Atom transfer radical polymerization of n‐butyl methacrylate (BMA) was conducted in an aqueous dispersed system with different kinds of copper complexes. The partitioning behavior of the copper complexes, including CuCl/4,4′‐di(5‐nonyl)‐2,2′‐bipydine (dNbpy), CuCl2/dNbpy, CuCl/2,2′‐bipydine (bpy), CuCl2/bpy, CuCl/bis(N,N′‐dimethylaminoethyl)ether (bde), and CuCl2/bde between the monomer (BMA), and water was studied in detail with ultraviolet‐visible spectroscopy. The results show that with a less hydrophobic ligand, such as bpy or bde, most of the Cu(I) or the Cu(II) complexes migrated from the BMA phase to the aqueous phase, the atom transfer equilibrium was destroyed, and the polymerization was nearly not controlled; it converted to classical emulsion polymerization. As to the very hydrophobic ligand dNbpy, although the partitioning study of the copper complexes indicated that not all the copper species were restricted to the organic phase, the linear correlation between the molecular weight and the monomer conversion and the narrow polydispersities confirmed that the polymerization was still quite well controlled. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3175–3179, 2003 相似文献
972.
973.
Electrochemical cell current requirements for toxic organic waste destruction in Ce(IV)-mediated electrochemical oxidation process 总被引:1,自引:0,他引:1
Vasily V. Kokovkin Sang Joon Chung Subramanian Balaji Manickam Matheswaran Il-Shik Moon 《Korean Journal of Chemical Engineering》2007,24(5):749-756
The electrochemical cell for cerium oxidation and reactor for organic destruction are the most important operation units for
the successful working mediated electrochemical oxidation (MEO) process. In this study, electrochemical cells with DSA electrodes
of two types, single stack and double stack connected in series, were used. The performances towards the electrochemical generation
of Ce(IV) in nitric acid media at 80 °C were studied. The current-voltage curves and cerium electrolysis kinetics showed the
dependence on number of cell stacks needed to be connected in series for the destruction of a given quantity of organic pollutant.
The presence of an optimum region for Ce(III) oxidation with a contribution of oxygen evolution, especially at low Ce(III)
concentration (high conversion ratios), was found. The cells were applied for the Ce(IV) regeneration during the organic destruction.
The cell and reactor processes were fitted in a simple model proposed and used to calculate the current needed in terms of
Ce(III) oxidation rate and the number of cell stacks required for maintaining Ce(IV)/Ce(III) ratio at the same level during
the organic destruction. This consideration was based on the kinetic model previously developed by us for the organic destruction
in the MEO process. 相似文献
974.
Ti‐based Ziegler–Natta catalysts supported on MgCl2 doped with AlCl3 were prepared by the reaction of MgCl2/AlCl3–ethanol adduct with TiCl4. No AlCl3 crystallites were found in the AlCl3‐doped catalysts by WAXD analysis, suggesting that AlCl3/MgCl2 solid solution was formed. The effect of doping on the catalyst performance in ethylene polymerization was investigated. The results showed that the catalysts based on AlCl3‐doped MgCl2 support exhibited a slightly higher activity than did the MgCl2‐supported catalyst and the molecular weight distribution (MWD) of polyethylene (PE) markedly increased (from 10.8 to 47.9) with the increase of AlCl3 content in catalysts. The changes in catalyst's active center distribution were studied based on nonlinear fitting of the polymer GPC curves by multiple Flory functions. It was found that increase of types of active centers by introducing AlCl3 into the support should be responsible for the broadening of MWD of PE. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1768–1772, 2006 相似文献
975.
Edward Kostansek 《Journal of Coatings Technology and Research》2004,1(1):41-44
Coagulation of latex particles is most often carried out in the diffusion limited aggregation (DLA) regime where the time
for coagulation to take place is on the millisecond timescale. This process produces aggregates of low density, irregular
shape, and a broad particle size distributions. When the coagulation is carried out in the reaction limited aggregation (RLA)
regime, a coagulation time of about 1–120 sec, the system can be controlled by mixing to yield dense, spheroidal aggregates
with a very narrow particle size distribution. The important variables in the RLA process for butyl acrylate/methyl methacrylate
(BA/MMA) latexes were found to be mixing intensity, latex copolymer composition, and coagulation temperature. Dried aggregates
formed in the RLA process were found to have excellent powder flow properties and low dustiness. 相似文献
976.
977.
978.
979.
In this study, the reaction kinetics of asymmetric polymer-polymer interface was experimentally and theoretically studied. A new rheological method correlating the change of rheological property of reactive system with the conversion of the in situ formed copolymers was applied to study the reaction kinetics of PBT/epoxy reactive system. Then, the new method was proved to be useful by comparing its results with that obtained from the conventional endgroup determination method. Moreover, the conversion of PBT/epoxy reactive system from rheological method could be well fitted by the numerical analysis, from which the kinetic constant and the diffusion constant of epoxy in PBT could be determined simultaneously. 相似文献
980.