全文获取类型
收费全文 | 100030篇 |
免费 | 9476篇 |
国内免费 | 5170篇 |
专业分类
电工技术 | 3323篇 |
技术理论 | 10篇 |
综合类 | 8047篇 |
化学工业 | 13241篇 |
金属工艺 | 19032篇 |
机械仪表 | 4852篇 |
建筑科学 | 19088篇 |
矿业工程 | 1650篇 |
能源动力 | 5668篇 |
轻工业 | 2292篇 |
水利工程 | 1491篇 |
石油天然气 | 3032篇 |
武器工业 | 598篇 |
无线电 | 2842篇 |
一般工业技术 | 10695篇 |
冶金工业 | 14481篇 |
原子能技术 | 1182篇 |
自动化技术 | 3152篇 |
出版年
2024年 | 246篇 |
2023年 | 1223篇 |
2022年 | 2631篇 |
2021年 | 3015篇 |
2020年 | 3142篇 |
2019年 | 2583篇 |
2018年 | 2186篇 |
2017年 | 3019篇 |
2016年 | 3223篇 |
2015年 | 3618篇 |
2014年 | 6053篇 |
2013年 | 5931篇 |
2012年 | 7034篇 |
2011年 | 8125篇 |
2010年 | 6129篇 |
2009年 | 6284篇 |
2008年 | 5329篇 |
2007年 | 6625篇 |
2006年 | 5997篇 |
2005年 | 5206篇 |
2004年 | 4285篇 |
2003年 | 3821篇 |
2002年 | 3221篇 |
2001年 | 2648篇 |
2000年 | 2296篇 |
1999年 | 1845篇 |
1998年 | 1552篇 |
1997年 | 1430篇 |
1996年 | 1231篇 |
1995年 | 963篇 |
1994年 | 796篇 |
1993年 | 596篇 |
1992年 | 547篇 |
1991年 | 371篇 |
1990年 | 333篇 |
1989年 | 291篇 |
1988年 | 202篇 |
1987年 | 117篇 |
1986年 | 91篇 |
1985年 | 75篇 |
1984年 | 82篇 |
1983年 | 59篇 |
1982年 | 45篇 |
1981年 | 27篇 |
1980年 | 52篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1966年 | 7篇 |
1959年 | 25篇 |
1951年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
介绍了对大桥的风向、风力和交通流量的测试依据和内容,分析了风向、风力的测试结果以及梁体在风力及交通流量等作用下的受力情况,指出钢箱梁体主要受到的力是风力。 相似文献
82.
Gas/liquid mass transfer has been investigated using a stirred vessel gas/liquid contactor using non‐Newtonian media and carbon dioxide as absorbent and gas phase, respectively. The volumetric mass transfer coefficients at different operational variables have been determined. Non‐Newtonian media (liquid phase) were prepared as aqueous solutions of sodium carboxymethyl cellulose salt. The influence of the rheological properties, polymer concentration, stirring rate, and gas flow rate on mass transfer was studied for these liquid phases. Kinematic viscosity and density experimental data were used to calculate the average molecular weight corresponding to the polymer employed. The Ostwald model has been used to fit the rheological behavior of aqueous solutions of the polymer employed as absorbent phase. Reasonably good agreement was found between the predictions of the proposed models and the experimental data of mass transfer coefficients. 相似文献
83.
84.
85.
86.
结合工程实例,阐述了在输水水质腐蚀性不大的情况下,输水钢管的内壁防腐采用水泥砂浆衬里的必要性和优点,并介绍了设计要点和安装施工注意事项。 相似文献
87.
G. Casalbore‐Miceli M.C. Gallazzi S. Zecchin N. Camaioni A. Geri C. Bertarelli 《Advanced functional materials》2003,13(4):307-312
Voltammetric and spectrophotometric measurements of poly(3,3″‐dipentoxy‐3′‐dicyanoethenyl‐2,2′:5′,2″‐terthiophene) (polyCN) films, in connection with other experimental evidence, reveal a normal oxidative, but a peculiar reductive behavior consisting of trapping of the negative charge during the cathodic scan. Another interesting property of polyCN films is the tendency to form strong intramolecular and intermolecular associations, probably charge‐transfer (CT) complexes. These properties could account for the fact that the photovoltaic performance does not improve when polyCN is blended with a polythiophene donor. 相似文献
88.
This article presents a method that can be applied to molten AA-6101 alloy to improve electrical properties of the aluminium part of the optical ground wire (OPGW) used in overhead transmission lines to protect phase conductors from lightning strike and to transmit signals and data. AA-6101 alloy in casting of the log as 6 m length and 178 mm diameter for extrusion has been inoculated by AlB2 to decrease detrimental effects of Cr, Ti, V, and Zr on the conductivity of the material. After inoculation, improved billets were extruded as 9.5 mm diameter feedstock. Required wires drawn from the feedstock according to the construction types of OPGW to be tested were exposed to aging at 175°C, 6 h (T-8). Upon completion of the back-twist and performing-type stranding process, resistance, and short-circuit current capacity and breaking load of the OPGW 88/44 constructions with other metal combinations have been examined and tested to show improvement. Results are summarized in tables and graphically. 相似文献
89.
Hiroshi Takamatsu Hikaru Yamashiro Nobuo Takata Hiroshi Honda 《International Journal of Refrigeration》2003,26(6):79
Heat and mass transfer in a falling film vertical in-tube absorber was studied experimentally with LiBr aqueous solution. The presented results include the effect of solution flow rate, solution subcooling and cooling water temperature on the absorption in a smooth copper tube 16.05 mm I.D. and 400 mm long. The experimental data in the previous report for a 1200-mm-long tube was also re-examined and compared. It was demonstrated by the observation of the flow in the tube that the break down of the liquid film into rivulets leads to deterioration of heat and mass transfer at lower film Reynolds number or in longer tubes. An attempt to evaluate physically acceptable heat and mass transfer coefficients that are defined with estimated temperature and concentration at the vapor–liquid interface was also presented. 相似文献
90.