全文获取类型
收费全文 | 60616篇 |
免费 | 3165篇 |
国内免费 | 2180篇 |
专业分类
电工技术 | 2279篇 |
技术理论 | 2篇 |
综合类 | 2284篇 |
化学工业 | 8909篇 |
金属工艺 | 4310篇 |
机械仪表 | 3186篇 |
建筑科学 | 3398篇 |
矿业工程 | 962篇 |
能源动力 | 1732篇 |
轻工业 | 3407篇 |
水利工程 | 667篇 |
石油天然气 | 2951篇 |
武器工业 | 206篇 |
无线电 | 7270篇 |
一般工业技术 | 11213篇 |
冶金工业 | 5864篇 |
原子能技术 | 702篇 |
自动化技术 | 6619篇 |
出版年
2024年 | 146篇 |
2023年 | 672篇 |
2022年 | 1051篇 |
2021年 | 1580篇 |
2020年 | 1189篇 |
2019年 | 1126篇 |
2018年 | 1363篇 |
2017年 | 1529篇 |
2016年 | 1470篇 |
2015年 | 1691篇 |
2014年 | 2259篇 |
2013年 | 3694篇 |
2012年 | 3022篇 |
2011年 | 3801篇 |
2010年 | 3271篇 |
2009年 | 3275篇 |
2008年 | 3283篇 |
2007年 | 3250篇 |
2006年 | 3136篇 |
2005年 | 2774篇 |
2004年 | 2035篇 |
2003年 | 1814篇 |
2002年 | 1744篇 |
2001年 | 1586篇 |
2000年 | 1581篇 |
1999年 | 1814篇 |
1998年 | 2404篇 |
1997年 | 1857篇 |
1996年 | 1708篇 |
1995年 | 1179篇 |
1994年 | 995篇 |
1993年 | 749篇 |
1992年 | 575篇 |
1991年 | 495篇 |
1990年 | 347篇 |
1989年 | 336篇 |
1988年 | 253篇 |
1987年 | 185篇 |
1986年 | 135篇 |
1985年 | 116篇 |
1984年 | 94篇 |
1983年 | 61篇 |
1982年 | 63篇 |
1981年 | 53篇 |
1980年 | 34篇 |
1979年 | 19篇 |
1977年 | 15篇 |
1976年 | 26篇 |
1975年 | 13篇 |
1973年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
121.
122.
123.
S. Danto P. Houizot C. Boussard‐Pledel X.‐H. Zhang F. Smektala J. Lucas 《Advanced functional materials》2006,16(14):1847-1852
Conditions of formation of bulk tellurium chalcogenide glasses, containing 70–80 at % Te associated to Ga and Ge are described. The characteristic temperatures are measured: the glass‐transition temperature, Tg, is situated in the range 140–185 °C and the difference Tx – Tg, where Tx is the onset crystallization temperature, is in the range 76–113 °C. Moreover, the optical transmission window is exceptional, ranging from 1.99 μm in the bandgap up to 28 μm in the phonon region. Developed within the framework of requirements for the Darwin mission (a search for and study of extrasolar planets), feasibility of infrared optical fibers formed from these glasses is studied. Drawing experiments are conducted with the glass Ga2‐Ge3Te15, which possesses the maximum Tx – Tg, and a first optical fiber is presented. 相似文献
124.
An alternative method to compute the component fractions in the geometrical optical model: visual computing method 总被引:1,自引:0,他引:1
Hong-Bo Su Ren-Hua Zhang Xin-Zhai Tang Xiao-Min Sun Zhi-Lin Zhu Zhao-Liang Li 《Geoscience and Remote Sensing, IEEE Transactions on》2003,41(3):719-724
A method called visual computing was used to solve angular four-components' proportions and directional vegetation cover fraction for discrete canopies and continuous row-planted plants. It proved effective to predict the angular characteristics on pixel scale. The method could be an alternative way to a classical solution of geometrical optical models. A visual computing method would be effective especially when the canopies' spatial distribution and shapes were irregular and could not be described statistically. 相似文献
125.
Yu Lung Tang Po-Yo Chen Huei Wang 《Microwave and Wireless Components Letters, IEEE》2004,14(5):201-203
A broadband frequency doubler, based on distributed amplifier techniques, has been designed to operate from 11 to 21 GHz. In order to reject the fundamental signal over a broadband frequency range, the conventional low-pass drain line structure was replaced with the high-pass structure. This topology can suppress fundamental signals over broadband without any balanced structure so that the chip size can be more compact. Measured conversion losses of better than 10 dB from 11 to 21 GHz input frequencies are achieved with fundamental signal rejection better than 12 dB. To the best of our knowledge, this is the first demonstration of distributed doubler using the high-pass drain line topology. 相似文献
126.
Parity space approach and H2 approach are two important fault detection approaches. This paper studies the relationship between these two approaches, which reveals frequency domain characteristics of the optimal solution of the parity space approach on the one side and provides a numerical solution of the H2-optimal design of residual generators on the other side. 相似文献
127.
Ultraviolet (UV) disinfection is becoming increasingly popular as an alternative disinfection technology to chlorination in recent years. In this study, we investigated the photoreactivation of Escherichia coli following medium-pressure (MP) UV disinfection of synthetic water by a bench-scale collimated beam apparatus. The UV doses ranged from 1.6 -19.7 mWs/cm2 and photoreactivation was investigated for 6 hours under fluorescent light. In addition, chloramination was applied after UV disinfection to investigate its ability to control photoreactivation. It was found that photoreactivation occurred for all UV doses tested and the increase in bacteria numbers ranged from 0.04 to 1.35 log10. However, the degree of photoreactivation decreased with increased UV doses. Chloramination experiments revealed that the addition of 0.5 mg/l of monochloramine resulted in suppression of photoreactivation for 1 hour only. An increased monochloramine dose of 1 mg/l was found to prevent photoreactivation for the entire duration of the experiment. The results of this study have shown that photoreactivation occurs even after MP UV disinfection, although it is of a lesser extent at higher UV doses. This study has also established that secondary chloramination can effectively suppress and eliminate photoreactivation with a chloramine dose of 1 mg/l. 相似文献
128.
Elastic solutions of a cylindrical rod containing periodically distributed inclusions with axisymmetric eigenstrains 总被引:1,自引:0,他引:1
Summary. In this paper, we give the elastic solution for a special type of microstructure – a circular cylindrical rod containing periodically distributed inclusions along its axial direction. Each inclusion has the same uniform axisymmetric transformation strain (eigenstrain). Analytical elastic solutions are obtained for the displacements, stresses and elastic strain energy of the rod. The effects of microstructure and its evolution (growth of inclusions) on the elastic stress and strain fields as well as the strain energy of the rod are quantitatively demonstrated. As a result of such microstructure evolution nominal stress-strain relation with strain softening is derived for a rod under uniaxial tension. 相似文献
129.
Lianshan Yan Yeh C. Yang G. Lin L. Chen Z. Shi Y.Q. Willner A.E. Yao X.S. 《Lightwave Technology, Journal of》2003,21(7):1676-1684
We demonstrate the first programmable group-delay module based on polarization switching. With a unique binary tuning mechanism, the device can generate any differential group delay value from -45 to +45 ps with a resolution of 1.40 ps, or any true-time-delay value from 0 to 45 ps with a resolution of 0.7 ps. The delay varying speeds for both applications are under 1 ms and can be as fast as 0.1 ms. We evaluate both the dynamic and static performances of the device while paying special attention to its dynamic figures of merit for polarization-mode dispersion emulation and compensation applications. Our experiment shows that the device exhibits a negligible transient-effect induced power penalty (<0.2 dB) in a 10-Gb/s nonreturn-to-zero system. 相似文献
130.
In this paper, we report on a novel family of monodisperse thermo‐sensitive core–shell hydrogel microspheres that is featured with high monodispersity and positively thermo‐responsive volume phase transition characteristics with tunable swelling kinetics, i.e., the particle swelling is induced by an increase rather than a decrease in temperature. The microspheres were fabricated in a three‐step process. In the first step, monodisperse poly(acrylamide‐co‐styrene) seeds were prepared by emulsifier‐free emulsion polymerization. In the second step, poly(acrylamide) or poly[acrylamide‐co‐(butyl methacrylate)] shells were fabricated on the microsphere seeds by free radical polymerization. In the third step, the core–shell microspheres with poly‐ (acrylamide)/poly(acrylic acid) based interpenetrating polymer network (IPN) shells were finished by a method of sequential IPN synthesis. The proposed monodisperse core–shell microspheres provide a new mode of the phase transition behavior for thermo‐sensitive “smart” or “intelligent” monodisperse micro‐actuators that is highly attractive for targeting drug delivery systems, chemical separations, sensors, and so on. 相似文献