全文获取类型
收费全文 | 51364篇 |
免费 | 4839篇 |
国内免费 | 2350篇 |
专业分类
电工技术 | 1485篇 |
综合类 | 2979篇 |
化学工业 | 15818篇 |
金属工艺 | 2420篇 |
机械仪表 | 2938篇 |
建筑科学 | 2527篇 |
矿业工程 | 1594篇 |
能源动力 | 852篇 |
轻工业 | 2526篇 |
水利工程 | 802篇 |
石油天然气 | 1698篇 |
武器工业 | 259篇 |
无线电 | 4545篇 |
一般工业技术 | 9635篇 |
冶金工业 | 899篇 |
原子能技术 | 505篇 |
自动化技术 | 7071篇 |
出版年
2024年 | 221篇 |
2023年 | 1001篇 |
2022年 | 1293篇 |
2021年 | 1753篇 |
2020年 | 1808篇 |
2019年 | 1711篇 |
2018年 | 1478篇 |
2017年 | 1765篇 |
2016年 | 1954篇 |
2015年 | 2168篇 |
2014年 | 2866篇 |
2013年 | 2997篇 |
2012年 | 3453篇 |
2011年 | 3932篇 |
2010年 | 3001篇 |
2009年 | 3172篇 |
2008年 | 2700篇 |
2007年 | 3083篇 |
2006年 | 2784篇 |
2005年 | 2612篇 |
2004年 | 2314篇 |
2003年 | 2214篇 |
2002年 | 1978篇 |
2001年 | 1228篇 |
2000年 | 1088篇 |
1999年 | 929篇 |
1998年 | 722篇 |
1997年 | 504篇 |
1996年 | 423篇 |
1995年 | 321篇 |
1994年 | 276篇 |
1993年 | 187篇 |
1992年 | 164篇 |
1991年 | 95篇 |
1990年 | 62篇 |
1989年 | 67篇 |
1988年 | 32篇 |
1987年 | 29篇 |
1986年 | 31篇 |
1985年 | 32篇 |
1984年 | 20篇 |
1983年 | 20篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1979年 | 6篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1959年 | 3篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Epoxy novolac/anhydride cure kinetics has been studied by differential scanning calorimetry under isothermal conditions. The system used in this study was an epoxy novolac resin (DEN431), with nadic methyl anhydride as hardener and benzyldimethylamine as accelerator. Kinetic parameters including the reaction order, activation energy and kinetic rate constants, were investigated. The cure reaction was described with the catalyst concentration, and a normalized kinetic model developed for it. It is shown that the cure reaction is dependent on the cure temperature and catalyst concentration, and that it proceeds through an autocatalytic kinetic mechanism. The curing kinetic constants and the cure activation energies were obtained using the Arrhenius kinetic model. A suggested kinetic model with a diffusion term was successfully used to describe and predict the cure kinetics of epoxy novolac resin compositions as a function of the catalyst content and temperature. Copyright © 2003 Society of Chemical Industry 相似文献
2.
A cell vertex finite volume method for the solution of steady compressible turbulent flow problems on unstructured hybrid
meshes of tetrahedra, prisms, pyramids and hexahedra is described. These hybrid meshes are constructed by firstly discretising
the computational domain using tetrahedral elements and then by merging certain tetrahedra. A one equation turbulence model
is employed and the solution of the steady flow equations is obtained by explicit relaxation. The solution process is accelerated
by the addition of a multigrid method, in which the coarse meshes are generated by agglomeration, and by parallelisation.
The approach is shown to be effective for the simulation of a number of 3D flows of current practical interest.
Sponsored by The Research Council of Norway, project number 125676/410
Dedicated to the memory of Prof. Mike Crisfield, a respected colleague 相似文献
3.
This paper describes the methodology for simulating a reprographic ink with a ceramic ink based on a commercially available zirconia powder for direct ceramic ink-jet printing. Of over-riding importance was matching viscosity and this was tested systematically by using a mineral oil–hexane binary system. Of secondary importance was adjustment of the pressure defect behind the nozzle to compensate for small differences in surface tension. The inks tested in the wide array print-head were based on low electrical conductivity liquids to avoid damage to the electroding system. The organic binder for the zirconia ink was paraffin wax and the dispersant was a hydroxystearic acid based polyester. 相似文献
4.
5.
6.
串行和并行接口模式是A/D转换器诸多分类中的一种,但却是应用中器件选择的一个重要指标.在同样的转换分辨率及转换速度的前提下,不同的接口方式不但影响了电路结构,更重要的是将在高速数据采集的过程中对采样周期产生较大影响.本文通过12位串行ADC ADS7822和并行ADC ADS774与AT89C51的接口电路,给出二者采样时间的差异性. 相似文献
7.
8.
A.L. Pan H.G. ZhengZ.P. Yang F.X. Liu Z.J. Ding Y.T. Qian 《Materials Research Bulletin》2003,38(5):789-796
Small Ag particles or clusters dispersed mesoporous SiO2 composite films were prepared by a new method: First the matrix SiO2 films were prepared by sol-gel process combined with the dip-coating technique, then they were soaked in AgNO3 solutions followed by irradiation of γ-ray at room temperature and in ambient pressure. The structures of these films were examined by X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), and optical absorption spectroscopy. It has been shown that the Ag particles grown within the porous SiO2 films are very small, and they are isolated and dispersed from each other with very narrow size distributions. With increasing the soaking concentration and an additional annealing, an opposite peakshift effect of the surface plasmon resonance (SPR) was observed in the optical absorption measurements. 相似文献
9.
加快塑料技术中心建设提高新产品开发水平 总被引:2,自引:2,他引:0
对中国石油化工集团公司(简称中国石化)合成树脂生产及加工应用技术的现状进行了分析,指出中国石化应加快建设塑料加工应用技术中心,为塑料产品的加工用户提供高技术水平和快捷周到的技术服务,在合成树脂新产品开发和产品结构调整中发挥积极作用,以提高合成树脂产品的市场竞争力。 相似文献
10.
激光水下成像技术及其进展 总被引:6,自引:0,他引:6
介绍了近年发展起来的三种主要的激光水下成像方法,即常规水下激光成像、高分辨率水下激光三维成像和偏振激光成像,分析了它们各自的工作原理、特点以及各自的发展状况。 相似文献