全文获取类型
收费全文 | 67164篇 |
免费 | 4348篇 |
国内免费 | 2735篇 |
专业分类
电工技术 | 2919篇 |
技术理论 | 2篇 |
综合类 | 2548篇 |
化学工业 | 10205篇 |
金属工艺 | 4798篇 |
机械仪表 | 3868篇 |
建筑科学 | 3479篇 |
矿业工程 | 1342篇 |
能源动力 | 2127篇 |
轻工业 | 3980篇 |
水利工程 | 797篇 |
石油天然气 | 2836篇 |
武器工业 | 342篇 |
无线电 | 8125篇 |
一般工业技术 | 12439篇 |
冶金工业 | 6291篇 |
原子能技术 | 794篇 |
自动化技术 | 7355篇 |
出版年
2024年 | 250篇 |
2023年 | 926篇 |
2022年 | 1637篇 |
2021年 | 2352篇 |
2020年 | 1706篇 |
2019年 | 1704篇 |
2018年 | 1913篇 |
2017年 | 1921篇 |
2016年 | 1887篇 |
2015年 | 2239篇 |
2014年 | 2814篇 |
2013年 | 4187篇 |
2012年 | 3649篇 |
2011年 | 4508篇 |
2010年 | 3542篇 |
2009年 | 3683篇 |
2008年 | 3717篇 |
2007年 | 3442篇 |
2006年 | 3401篇 |
2005年 | 2850篇 |
2004年 | 2167篇 |
2003年 | 1977篇 |
2002年 | 1863篇 |
2001年 | 1708篇 |
2000年 | 1640篇 |
1999年 | 1723篇 |
1998年 | 2288篇 |
1997年 | 1747篇 |
1996年 | 1531篇 |
1995年 | 1087篇 |
1994年 | 860篇 |
1993年 | 648篇 |
1992年 | 464篇 |
1991年 | 448篇 |
1990年 | 325篇 |
1989年 | 322篇 |
1988年 | 219篇 |
1987年 | 173篇 |
1986年 | 115篇 |
1985年 | 110篇 |
1984年 | 74篇 |
1983年 | 68篇 |
1982年 | 55篇 |
1981年 | 52篇 |
1980年 | 42篇 |
1979年 | 25篇 |
1978年 | 23篇 |
1976年 | 37篇 |
1975年 | 21篇 |
1973年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Flotation is a water treatment alternative to sedimentation, and uses small bubbles to remove low-density particles from potable water and wastewater. The effect of zeta potential, bubble size and particle size on removal efficiency of the electro-flotation process was investigated because previous model-simulations indicated that these attributes are critical for high collision efficiency between micro-bubbles and particles. Solutions containing Al3+ as the metal ion were subjected to various conditions. The zeta potentials of bubbles and particles were similar under identical conditions, and their charges were influenced by metal ion concentration and pH. Maximum removal efficiency was 98 and 12% in the presence and absence of flocculation, respectively. Removal efficiency was higher when particle size was similar to bubble size. These results agree with modelling simulations and indicate that collision efficiency is greater when the zeta potential of one is negative and that of the other is positive and when their sizes are similar. 相似文献
2.
A new excimer laser annealing (ELA) process that uses a floating amorphous-Silicon (a-Si) thin film with a multichannel structure is proposed for high-performance poly-Si thin-film transistors (TFTs). The proposed ELA method produces two-dimensional (2-D) grain growth, which can result in a high-quality grain structure. The dual-gate structure was employed to eliminate the grain boundaries perpendicular to the current flow in the channel. A multichannel structure was adapted in order to arrange the grain boundary to be parallel to the current flow. The proposed poly-Si TFT exhibits high-performance electrical characteristics, which are a high mobility of 504 cm/sup 2//Vsec and a low subthreshold slope of 0.337 V/dec. 相似文献
3.
4.
H. L. Du S. R. Rose Z. D. Xiang P. K. Datta X. Y. Li 《Materialwissenschaft und Werkstofftechnik》2003,34(4):421-426
The oxidation/sulphidation behaviour of a Ti‐46.7Al‐1.9W‐0.5Si alloy with a TiAl3 diffusion coating was studied in an environment of H2/H2S/H2O at 850oC. The kinetic results demonstrate that the TiAl3 coating significantly increased the high temperature corrosion resistance of Ti‐46.7Al‐1.9W‐0.5Si. The SEM, EDX, XRD and TEM analysis reveals that the formation of an Al2O3 scale on the surface of the TiAl3‐coated sample was responsible for the enhancement of the corroison resistance. The Ti‐46.7Al‐1.9W‐0.5Si alloy was also modified by Nb ion implantation. The Nb ion implanted and as received sampels were subjected to cyclic oxidation in an open air at 800oC. The Nb ion implantation not only increased the oxidation resistance but also substantially improved the adhesion of scale to the substrate. 相似文献
5.
Shi-Jin Ding Hang Hu Lim H.F. Kim S.J. Yu X.F. Chunxiang Zhu Li M.F. Byung Jin Cho Chan D.S.H. Rustagi S.C. Yu M.B. Chin A. Dim-Lee Kwong 《Electron Device Letters, IEEE》2003,24(12):730-732
For the first time, we successfully fabricated and demonstrated high performance metal-insulator-metal (MIM) capacitors with HfO/sub 2/-Al/sub 2/O/sub 3/ laminate dielectric using atomic layer deposition (ALD) technique. Our data indicates that the laminate MIM capacitor can provide high capacitance density of 12.8 fF//spl mu/m/sup 2/ from 10 kHz up to 20 GHz, very low leakage current of 3.2 /spl times/ 10/sup -8/ A/cm/sup 2/ at 3.3 V, small linear voltage coefficient of capacitance of 240 ppm/V together with quadratic one of 1830 ppm/V/sup 2/, temperature coefficient of capacitance of 182 ppm//spl deg/C, and high breakdown field of /spl sim/6 MV/cm as well as promising reliability. As a result, the HfO/sub 2/-Al/sub 2/O/sub 3/ laminate is a very promising candidate for next generation MIM capacitor for radio frequency and mixed signal integrated circuit applications. 相似文献
6.
Towards intelligent dressing 总被引:1,自引:0,他引:1
Egana I. Mendikute A. Urionaguena X. Alberdi H. 《IEEE instrumentation & measurement magazine》2006,9(3):38-43
The aim of this article is to state the principles of an intelligent monitoring and control system for the grinding machine, comprising the dressing process as well as grinding stability. 相似文献
7.
Douay M. Xie W.X. Taunay T. Bernage P. Niay P. Cordier P. Poumellec B. Dong L. Bayon J.F. Poignant H. Delevaque E. 《Lightwave Technology, Journal of》1997,15(8):1329-1342
A comprehensive survey of photosensitivity in silica glasses and optical fiber is reviewed. Recent work on understanding the mechanisms contributing to germanium or aluminum doped fiber photosensitivity is discussed within the framework of photoelastic densification models 相似文献
8.
本文首先给出了一种新的2.5D 实体表示法,然后在此基础上提出了“原型”的概念。原型法的思想运用在结构库的管理中主要体现在它将模具结构与构成这种结构的零件之间的强联系变成弱联系,结构库面向的对象是一个具有整体性和可运算性的结构原型。这样的原型结构库基本上达到了通用性与开放性的要求。 相似文献
9.
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
10.
Xiang‐Dan Li Zhen‐Xin Zhong Sang‐Hoon Han Seung Hee Lee Myong‐Hoon Lee 《Polymer International》2005,54(2):406-411
From chloromethylated polyimide, a useful starting material for modification of aromatic polyimides, a thermocurable transparent polyimide having acrylate side groups was prepared. In the presence of 1,8‐diazabicyclo[5,4,0]undec‐7‐ene, chloromethylated polyimide was esterified with acrylic acid to synthesize poly(imide methylene acrylate). The polymer was soluble in organic solvent, which makes it possible to prepare a planar film by spin coating. The polymer film became insoluble after thermal treatment at 230 °C for 30 min. Optical transparency of the film at 400 nm (for 1 µm thickness) was higher than 98 % and not affected by further heating at 230 °C for 250 min. Adhesion properties measured by the ASTM D3359‐B method ranged from 4B to 5B. Preliminary results of planarization testing showed a high degree of planarization (DOP) value (>0.53). These properties demonstrate that poly(imide methylene acrylate) could be utilized as a thermocurable transparent material in fabricating display devices such as TFT‐LCD. Copyright © 2004 Society of Chemical Industry 相似文献