全文获取类型
收费全文 | 830925篇 |
免费 | 12967篇 |
国内免费 | 2480篇 |
专业分类
电工技术 | 15057篇 |
综合类 | 840篇 |
化学工业 | 125832篇 |
金属工艺 | 30158篇 |
机械仪表 | 23472篇 |
建筑科学 | 22039篇 |
矿业工程 | 3238篇 |
能源动力 | 22688篇 |
轻工业 | 76194篇 |
水利工程 | 7499篇 |
石油天然气 | 10891篇 |
武器工业 | 49篇 |
无线电 | 98476篇 |
一般工业技术 | 155960篇 |
冶金工业 | 164315篇 |
原子能技术 | 14449篇 |
自动化技术 | 75215篇 |
出版年
2021年 | 6943篇 |
2020年 | 5003篇 |
2019年 | 6384篇 |
2018年 | 10590篇 |
2017年 | 10380篇 |
2016年 | 11093篇 |
2015年 | 8145篇 |
2014年 | 13331篇 |
2013年 | 39150篇 |
2012年 | 21699篇 |
2011年 | 30366篇 |
2010年 | 23812篇 |
2009年 | 26753篇 |
2008年 | 27863篇 |
2007年 | 27713篇 |
2006年 | 24577篇 |
2005年 | 22560篇 |
2004年 | 21707篇 |
2003年 | 21387篇 |
2002年 | 20419篇 |
2001年 | 20304篇 |
2000年 | 18785篇 |
1999年 | 20086篇 |
1998年 | 49872篇 |
1997年 | 35476篇 |
1996年 | 27520篇 |
1995年 | 21067篇 |
1994年 | 18533篇 |
1993年 | 18094篇 |
1992年 | 13156篇 |
1991年 | 12444篇 |
1990年 | 12092篇 |
1989年 | 11728篇 |
1988年 | 11027篇 |
1987年 | 9678篇 |
1986年 | 9484篇 |
1985年 | 11110篇 |
1984年 | 10404篇 |
1983年 | 9143篇 |
1982年 | 8578篇 |
1981年 | 8608篇 |
1980年 | 8154篇 |
1979年 | 7990篇 |
1978年 | 7552篇 |
1977年 | 9076篇 |
1976年 | 12136篇 |
1975年 | 6458篇 |
1974年 | 6135篇 |
1973年 | 6136篇 |
1972年 | 4993篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
V. E. Gromov A. M. Glezer K. V. Morozov Yu. F. Ivanov K. V. Volkov 《Russian Metallurgy (Metally)》2015,2015(13):1094-1097
A layer-by-layer analysis of the structures, the phase compositions, and the defect substructures of differentially hardened rails has been carried by optical and transmission electron microscopy. It is found that the material volume of the rail head fillet is cooled faster than the volume located along the central axis. 相似文献
94.
Quality enhancement of the abundant under‐valued crustacean,lobster krill (Munida spp.), during its chilled storage 下载免费PDF全文
Bibiana García‐Soto José M. Miranda Jorge Barros‐Velázquez Santiago P. Aubourg 《International Journal of Food Science & Technology》2015,50(3):708-716
Lobster krill (Munida genus) represents an under‐valued crustacean frequently caught on European fishing banks. In this work, its sensory, microbiological and biochemical qualities were evaluated during chilled storage. Additionally, the effects of a prestorage antimelanosic treatment consisting of soaking in sodium metabisulphite (SMB) solutions at two different concentrations (0.25% and 0.75%) were also studied. SMB prestorage treatment provided lobster specimens that still exhibited acceptable sensory quality after 10 days of storage, while control specimens were unacceptable at that time. SMB treatment also resulted in a significant (P < 0.05) inhibition of microbial growth, mainly of Enterobacteriaceae, psychrotrophes and proteolytic bacteria. Low lipid oxidation levels were observed for all batches; however, a significantly higher (P < 0.05) retention of polyunsaturated fatty acids was found in SMB‐treated lobster, especially in the 0.75% SMB batch. The results presented here open the way to the potential commercialisation of currently under‐utilised lobster krill as a chilled product. 相似文献
95.
Babilas R. Łoński W. Młynarek K. Bajorek A. Radoń A. 《Metallurgical and Materials Transactions A》2020,51(8):4215-4227
Metallurgical and Materials Transactions A - The influence of the chemical composition on the crystallization process, amorphous phase formation, and the anticorrosion properties of Al-Zr-Ni-Fe-Y... 相似文献
96.
Strength of Materials - The use of a damping system is one of the seismic protection systems that improve the seismic response of structures. The proposed methodology estimates the location (which... 相似文献
97.
Loboda P. I. Minitsky A. V. Byba Ye. G. Sysoev M. O. Radchuk S. V. 《Powder Metallurgy and Metal Ceramics》2020,58(11-12):651-656
Powder Metallurgy and Metal Ceramics - The infiltration of aluminum melts into porous metal skeletons produced by powder metallurgy methods, including 3D printing, under a pressure gradient was... 相似文献
98.
As a solid state joining process, ultrasonic spot welding has been proven to be a promising technique for joining copper alloys. However, challenges still remain in employing ultrasonic spot welding to join copper alloys. This article comprehensively reviews the current state of ultrasonic spot welding of copper alloys with a number of critical issues including materials flow, plastic deformation, temperature distribution, vibration, relative motion, vertical displacement, interface friction coefficient, online monitoring technique, coupled with the macrostructure and microstructure, the mechanical properties and electrical conductivity. In addition, the future trends in this field are provided. 相似文献
99.
Measurement Techniques - A method is proposed for transferring the unit of mean power of laser radiation by means of measuring high-intensity power (kilowatts), with the possibility of constant... 相似文献
100.
Kevin J. Hanley 《International journal for numerical methods in engineering》2020,121(21):4865-4877
An algorithm is presented for discrete element method simulations of energy-conserving systems of frictionless, spherical particles in a reversed-time frame. This algorithm is verified, within the limits of round-off error, through implementation in the LAMMPS code. Mechanisms for energy dissipation such as interparticle friction, damping, rotational resistance, particle crushing, or bond breakage cannot be incorporated into this algorithm without causing time irreversibility. This theoretical development is applied to critical-state soil mechanics as an exemplar. It is shown that the convergence of soil samples, which differ only in terms of their initial void ratio, to the same critical state requires the presence of shear forces and frictional dissipation within the soil system. 相似文献