全文获取类型
收费全文 | 411512篇 |
免费 | 46806篇 |
国内免费 | 32940篇 |
专业分类
电工技术 | 36178篇 |
技术理论 | 4篇 |
综合类 | 43625篇 |
化学工业 | 51721篇 |
金属工艺 | 28676篇 |
机械仪表 | 28905篇 |
建筑科学 | 30723篇 |
矿业工程 | 17304篇 |
能源动力 | 10710篇 |
轻工业 | 45662篇 |
水利工程 | 13331篇 |
石油天然气 | 14920篇 |
武器工业 | 5927篇 |
无线电 | 43527篇 |
一般工业技术 | 35346篇 |
冶金工业 | 17881篇 |
原子能技术 | 6945篇 |
自动化技术 | 59873篇 |
出版年
2024年 | 2544篇 |
2023年 | 6934篇 |
2022年 | 15974篇 |
2021年 | 20630篇 |
2020年 | 14553篇 |
2019年 | 10338篇 |
2018年 | 11052篇 |
2017年 | 13078篇 |
2016年 | 11706篇 |
2015年 | 18396篇 |
2014年 | 23012篇 |
2013年 | 27212篇 |
2012年 | 33588篇 |
2011年 | 35459篇 |
2010年 | 33290篇 |
2009年 | 31473篇 |
2008年 | 32839篇 |
2007年 | 31652篇 |
2006年 | 27612篇 |
2005年 | 22815篇 |
2004年 | 16242篇 |
2003年 | 11093篇 |
2002年 | 10534篇 |
2001年 | 9280篇 |
2000年 | 7504篇 |
1999年 | 3427篇 |
1998年 | 1559篇 |
1997年 | 1264篇 |
1996年 | 1142篇 |
1995年 | 932篇 |
1994年 | 768篇 |
1993年 | 644篇 |
1992年 | 507篇 |
1991年 | 391篇 |
1990年 | 333篇 |
1989年 | 287篇 |
1988年 | 210篇 |
1987年 | 141篇 |
1986年 | 111篇 |
1985年 | 77篇 |
1984年 | 63篇 |
1983年 | 54篇 |
1982年 | 63篇 |
1981年 | 84篇 |
1980年 | 118篇 |
1979年 | 73篇 |
1976年 | 9篇 |
1965年 | 8篇 |
1959年 | 72篇 |
1951年 | 76篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
回顾了水口山有色金属集团有限公司的发展历程,概述了取得的技术进步和主要成就.提出了企业今后的发展方向。 相似文献
82.
The bonding of β'-Al2O3 and pyrex glass to Al matrix composites by anodic bonding process is achieved. The microstructure of the bonded interface and the joining mechanisms are analyzed with scanning electron microscope (SEM), energy dispersive X-ray fluorescence spectrometer (EDX). It is observed that the bonding region across the interface consists of the metal layer, oxide transitional layer and the ceramic layer, with the transitional layer composed of surface region and sub-surface region. The bonding process can mainly be categorized into anodic bonding process and solid state diffusing process. The pile-up of the ions and its drift in the interface area are the main reasons for anode oxidation and joining of the interface. The temperature, voltage and the drift ions in the ceramic or glass during the bonding process are the essential conditions to solid state diffusing and oxide bonding at the interface. The voltages, temperature, pressure as well as the surface state are the main factors that influence the anodic bonding. 相似文献
83.
84.
86.
The cooling and solidification of melted drops during their movement in an immiscible cooling medium is widely employed for granulation in the chemical industry, and a study of these processes to provides a basis for the design of the granulation tower height and the temperature of the cooling medium is reported. A physical model of the cooling and solidification of the drop is established and the numerical calculation is performed. The influences of the key factors in the solidification, i.e., Bi number, drop diameter, temperature of the cooling medium, etc. are presented. The cooling and solidification during wax granulation in a water‐cooling tower and during urea granulation in an air‐cooling tower (spraying tower) are described in detail. Characteristics of the solidification and temperature distribution within the particle at different times are shown. The model and calculations can be used for structure design of the granulation tower and optimization of the operation parameters. 相似文献
87.
Biodegradable multiblock poloxamers (BMPs) with gel duration of 8 h to several weeks were prepared by varying their molecular weights from 4000 to 40 000 g mol?1. The molecular weight of the BMP was controlled by changing the poloxamer to coupling agent ratio. Assuming a micelle packing model of the BMP gel, as in the case of a poloxamer gel, the micelle properties and critical gel concentration of BMPs were investigated on the basis of the scaling concept. The findings suggest that the control of molecular weight by hydrolyzable groups can be a facile approach to optimize the gel properties for biomedical applications. Copyright © 2005 Society of Chemical Industry 相似文献
88.
Colour Centres and Energy Transfer in BaF2-xClx:Eu2+ Phosphors 总被引:1,自引:1,他引:0
The optical absorption spectra of BaF2-xClx:Eu2 after ultraviolet (UV) light excitation were investigated.The differences between the absorption spectra after and before excitation (DAS) were observed.The DAS increase at both the high and the low energy side of F band in BaF2-xClx:Eu2 after 245 nm UV light excitation.The bleach effect of UV light and the absorption of electrons in the valence band may account for the former and the formation of Fa centres (association of F(Cl-) centres), whose absorption band matches the HeNe laser better, may explain the latter.In the write-in process, the transfer of electrons is via tunneling.In the readout process, the transfer of electrons captured in F(F-) and Fa centres is more likely via tunneling, and that of F(Cl-) centres is more likely via conduction band. 相似文献
89.
借鉴模型参考控制器的设计思想,采用经过线性二次型输出反馈控制后的系统作为参考模型,以它的输出作为期望输出,让实际输出跟随这个期望输出;二者的误差信号反馈到原系统的输入端,设计出一种模型参考控制器.经该控制器优化后,电视导引头系统的快速性可得到较大提高.参考模型可由RC网络或计算机软件来实现. 相似文献
90.
氨氮监测采用预蒸馏处理后,比色测定结果明显偏低。在样品预蒸馏处理过程中,硼酸作为吸收液,使显色时溶液pH值偏低,导致显色不充分是其主要影响因素。通过采取增加显色剂加入量的方法,解决了显色pH值偏低的问题,得到满意的测定结果。 相似文献