全文获取类型
收费全文 | 566350篇 |
免费 | 9625篇 |
国内免费 | 2576篇 |
专业分类
电工技术 | 11258篇 |
技术理论 | 5篇 |
综合类 | 2314篇 |
化学工业 | 87838篇 |
金属工艺 | 20513篇 |
机械仪表 | 16145篇 |
建筑科学 | 14699篇 |
矿业工程 | 2833篇 |
能源动力 | 13796篇 |
轻工业 | 53379篇 |
水利工程 | 5538篇 |
石油天然气 | 9078篇 |
武器工业 | 254篇 |
无线电 | 63166篇 |
一般工业技术 | 103019篇 |
冶金工业 | 112827篇 |
原子能技术 | 10187篇 |
自动化技术 | 51702篇 |
出版年
2021年 | 4898篇 |
2019年 | 4223篇 |
2018年 | 7176篇 |
2017年 | 7159篇 |
2016年 | 8010篇 |
2015年 | 5991篇 |
2014年 | 9081篇 |
2013年 | 24807篇 |
2012年 | 16246篇 |
2011年 | 21626篇 |
2010年 | 15933篇 |
2009年 | 17588篇 |
2008年 | 18523篇 |
2007年 | 18466篇 |
2006年 | 16374篇 |
2005年 | 17263篇 |
2004年 | 15678篇 |
2003年 | 14667篇 |
2002年 | 13358篇 |
2001年 | 13414篇 |
2000年 | 12262篇 |
1999年 | 12781篇 |
1998年 | 32573篇 |
1997年 | 23357篇 |
1996年 | 17923篇 |
1995年 | 13423篇 |
1994年 | 12124篇 |
1993年 | 11725篇 |
1992年 | 8602篇 |
1991年 | 8218篇 |
1990年 | 8202篇 |
1989年 | 8018篇 |
1988年 | 7730篇 |
1987年 | 6473篇 |
1986年 | 6669篇 |
1985年 | 7534篇 |
1984年 | 7017篇 |
1983年 | 6566篇 |
1982年 | 5913篇 |
1981年 | 6289篇 |
1980年 | 5821篇 |
1979年 | 5811篇 |
1978年 | 5558篇 |
1977年 | 6663篇 |
1976年 | 9059篇 |
1975年 | 4896篇 |
1974年 | 4576篇 |
1973年 | 4681篇 |
1972年 | 3925篇 |
1971年 | 3498篇 |
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
101.
102.
103.
104.
105.
Semiconductors - We found bulk n-GaAs layers grown by liquid phase epitaxy to be irregularly stressed. Deformation created by this stress causes a small but detectable quadrupole splitting of... 相似文献
106.
Bakhale Mugdha Hemalatha V. Dhanalakshmi Samiappan Kumar R. Siddharth Jain M. 《Wireless Personal Communications》2020,110(2):573-592
Wireless Personal Communications - A relatively new area of research and development is Swarm Robotics. It is a part of the swarm intelligence field. In the proposed paper, we shall use swarm... 相似文献
107.
Giorgio Benedek Joseph R. Manson Salvador Miret-Artés 《Advanced materials (Deerfield Beach, Fla.)》2020,32(25):2002072
Atom scattering is becoming recognized as a sensitive probe of the electron–phonon interaction parameter λ at metal and metal-overlayer surfaces. Here, the theory is developed, linking λ to the thermal attenuation of atom scattering spectra (in particular, the Debye–Waller factor), to conducting materials of different dimensions, from quasi-1D systems such as W(110):H(1 × 1) and Bi(114), to quasi-2D layered chalcogenides, and high-dimensional surfaces such as quasicrystalline 2ML-Ba(0001)/Cu(001) and d-AlNiCo(00001). Values of λ obtained using He atoms compare favorably with known values for the bulk materials. The corresponding analysis indicates in addition, the number of layers contributing to the electron–phonon interaction, which is measured in an atom surface collision. 相似文献
108.
Anjan Biswas Sonmezoglu Abdullah Ekici Mehmet Alzahrani Abdullah Khamis Belic Milivoj R. 《Journal of Communications Technology and Electronics》2020,65(12):1384-1398
Journal of Communications Technology and Electronics - This paper implements mathematically rigorous extended trial function algorithm to address cubic–quartic optical solitons in... 相似文献
109.
Strength of Materials - The paper presents a procedure for determining the design parameters of multilayer thick-walled structures with a local load on the inner surface portion located near the... 相似文献
110.
Isaac Isarn Leïla Bonnaud Lluís Massagus ngels Serra Francesc Ferrando 《Polymer International》2020,69(3):280-290
The enhancement of the thermal conductivity, keeping the electrical insulation, of epoxy thermosets through the addition of pristine and oxidized carbon nanotubes (CNTs) and microplatelets of boron nitride (BN) was studied. Two different epoxy resins were selected: a cycloaliphatic (ECC) epoxy resin and a glycidylic (DGEBA) epoxy resin. The characteristics of the composites prepared were evaluated and compared in terms of thermal, thermomechanical, rheological and electrical properties. Two different dispersion methods were used in the addition of pristine and oxidized CNTs depending on the type of epoxy resin used. Slight changes in the kinetics of the curing reaction were observed in the presence of the fillers. The addition of pristine CNTs led to a greater enhancement of the mechanical properties of the ECC composite whereas the oxidized CNTs presented a greater effect in the DGEBA matrix. The addition of CNTs alone led to a marked decrease of the electrical resistivity of the composites. Nevertheless, in the presence of BN, which is an electrically insulating material, it was possible to increase the proportion of pristine CNTs to 0.25 wt% in the formulation without deterioration of the electrical resistivity. A small but significant synergic effect was determined when both fillers were added together. Improvements of about 750% and 400% in thermal conductivity were obtained in comparison to the neat epoxy matrix for the ECC and DGEBA composites, respectively. © 2019 Society of Chemical Industry 相似文献