全文获取类型
收费全文 | 261104篇 |
免费 | 20326篇 |
国内免费 | 10665篇 |
专业分类
电工技术 | 14967篇 |
技术理论 | 18篇 |
综合类 | 15343篇 |
化学工业 | 44617篇 |
金属工艺 | 13694篇 |
机械仪表 | 15599篇 |
建筑科学 | 20696篇 |
矿业工程 | 6154篇 |
能源动力 | 7420篇 |
轻工业 | 16787篇 |
水利工程 | 4346篇 |
石油天然气 | 13426篇 |
武器工业 | 1806篇 |
无线电 | 32569篇 |
一般工业技术 | 33621篇 |
冶金工业 | 13185篇 |
原子能技术 | 2805篇 |
自动化技术 | 35042篇 |
出版年
2024年 | 1094篇 |
2023年 | 4029篇 |
2022年 | 7320篇 |
2021年 | 10024篇 |
2020年 | 7310篇 |
2019年 | 6359篇 |
2018年 | 6863篇 |
2017年 | 7851篇 |
2016年 | 7345篇 |
2015年 | 9570篇 |
2014年 | 12279篇 |
2013年 | 15603篇 |
2012年 | 15813篇 |
2011年 | 17876篇 |
2010年 | 15249篇 |
2009年 | 14780篇 |
2008年 | 14228篇 |
2007年 | 13576篇 |
2006年 | 13955篇 |
2005年 | 12302篇 |
2004年 | 8536篇 |
2003年 | 7659篇 |
2002年 | 7432篇 |
2001年 | 6550篇 |
2000年 | 6300篇 |
1999年 | 6846篇 |
1998年 | 6245篇 |
1997年 | 5151篇 |
1996年 | 4680篇 |
1995年 | 3962篇 |
1994年 | 3310篇 |
1993年 | 2588篇 |
1992年 | 1997篇 |
1991年 | 1510篇 |
1990年 | 1186篇 |
1989年 | 1020篇 |
1988年 | 799篇 |
1987年 | 567篇 |
1986年 | 449篇 |
1985年 | 372篇 |
1984年 | 241篇 |
1983年 | 214篇 |
1982年 | 182篇 |
1981年 | 165篇 |
1980年 | 146篇 |
1979年 | 105篇 |
1978年 | 63篇 |
1977年 | 63篇 |
1976年 | 85篇 |
1975年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
32.
33.
为确保特殊时期党政军指挥通信畅通,充分利用中国移动现网资源,将卫星通信与地面光缆、微波传榆。以及移动网络无缝衔接,共同构建中国移动天地一体应急通信平台。 相似文献
34.
TD-SCDMA直放站对网络性能的影响 总被引:1,自引:0,他引:1
TD-SCDMA直放站是用于TD-SCDMA移动通信网的全双工、线性射频放大设备.介绍了TD直放站不同于其它系统的同步的时分双工模式特点,并讨论了TD-SCDMA直放站的引入可能对网络性能造成的影响及其解决方法。 相似文献
35.
论文将Fermat素性检验的思想运用于不可约多项式的判断,给出了一个对于不可约判断问题的Monte Carlo 算法,分析了该算法的计算复杂度问题,并且给出了次数在200以内的检验结果。 相似文献
36.
Chun-Tsen Lu Kun-Wei Lin Huey-Ing Chen Hung-Ming Chuang Chun-Yuan Chen Wen-Chau Liu 《Electron Device Letters, IEEE》2003,24(6):390-392
A new and interesting Pd-oxide-Al/sub 0.3/Ga/sub 0.7/As MOS hydrogen sensor has been fabricated and studied. The steady-state and transient responses with different hydrogen concentrations has been measured at various temperatures. Based on the large Schottky barrier height and presence of oxide layer, the studied device exhibits a high hydrogen detection sensitivity and wide temperature operating regime. The studied device exhibits the low-leakage current and obvious current changes when exposed to hydrogen-contained gas. Even at room temperature, a very high hydrogen detection sensitivity of 155.9 is obtained when a 9090 ppm H/sub 2//air gas is introduced. Furthermore, when exposed to hydrogen-contained gas at 95/spl deg/C, both the forward and reverse currents are substantially increased with increased hydrogen concentration. In other words, the studied device can be used as a hydrogen sensor under the applied bidirectional bias. Under the applied voltage of 0.35 V and 9090 ppm H/sub 2//air hydrogen ambient, a fast adsorption response time about 10 s is found. The transient and steady-state characteristics of hydrogen adsorption are also investigated. 相似文献
37.
Jin Tae Kim Keun Byoung Yoon Choon-Gi Choi 《Photonics Technology Letters, IEEE》2004,16(7):1664-1666
A novel fabrication process using a hot embossing technique has been developed for micromechanical passive alignment of polymer planar lightwave circuit (PLC) devices. With only one step of embossing, single-mode waveguide straight channels and micropedestals for passive aligning are simultaneously defined on a polymer thin film with an accuracy of /spl plusmn/0.5 /spl mu/m. This process reduces the steps for fabricating alignment structures. A fabricated polymer PLC chip and fibers are combined on a v-grooved silicon optical bench (SiOB) in a flip-chip manner. The process provides a coupling loss as low as 0.67 dB per coupling face and a cost-effective packaging solution for various polymer PLC devices. 相似文献
38.
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
39.
The hydrogenated poly-silicon germanium (poly-SiGe:H) epitaxial film has been investigated using gold-induced lateral crystallization (Au-ILC) technology on a-SiGe:H layers at 10-h 350/spl deg/C annealing temperature and 60-sccm hydrogen (H/sub 2/) content. Using this optimal condition, the growth rate of the induced Au was as large as 15.9 /spl mu/m/h. With a low annealing temperature (/spl les/400/spl deg/C) and large growth rate, this novel technology will be noticeably useful for poly-SiGe:H pin IR-sensing fabrication on a conventional precoated indium tin oxide (ITO)-glass substrate. Under a 1-/spl mu/W IR-LED incident light (with peak wave length at 710 nm) and at a 5-V biased voltage, the poly-SiGe:H pin IR sensor developed by the Au-ILC technology, i.e., an Al (anode)/n poly-SiGe:H/i poly-SiGe:H/p poly-SiGe:H/ITO (cathode)/glass-substrate structure allowed for maximum optical gain and response speed. The optical gains and the response speeds were almost 600 and 130%, respectively, better than that of a traditional pin type. Meanwhile, the FWHM of a poly-SiGe:H pin sensor with Au-ILC technology was reduced from 280 to 150 nm. This reveals excellent IR-sensing selectivity. These IR-sensing trials demonstrated again that the proposed Au-ILC technology has very useful application in the field of low cost integrated circuits on optoelectronic applications. 相似文献
40.