全文获取类型
收费全文 | 84375篇 |
免费 | 8341篇 |
国内免费 | 4578篇 |
专业分类
电工技术 | 6379篇 |
技术理论 | 2篇 |
综合类 | 6018篇 |
化学工业 | 12513篇 |
金属工艺 | 5226篇 |
机械仪表 | 5958篇 |
建筑科学 | 5632篇 |
矿业工程 | 2220篇 |
能源动力 | 2724篇 |
轻工业 | 5893篇 |
水利工程 | 1967篇 |
石油天然气 | 3476篇 |
武器工业 | 1015篇 |
无线电 | 10852篇 |
一般工业技术 | 9957篇 |
冶金工业 | 4034篇 |
原子能技术 | 1078篇 |
自动化技术 | 12350篇 |
出版年
2024年 | 277篇 |
2023年 | 1006篇 |
2022年 | 2070篇 |
2021年 | 3113篇 |
2020年 | 2290篇 |
2019年 | 1878篇 |
2018年 | 2112篇 |
2017年 | 2588篇 |
2016年 | 2523篇 |
2015年 | 3314篇 |
2014年 | 4357篇 |
2013年 | 5220篇 |
2012年 | 6431篇 |
2011年 | 6872篇 |
2010年 | 6351篇 |
2009年 | 6180篇 |
2008年 | 6020篇 |
2007年 | 5568篇 |
2006年 | 5081篇 |
2005年 | 4211篇 |
2004年 | 3345篇 |
2003年 | 3070篇 |
2002年 | 3242篇 |
2001年 | 2784篇 |
2000年 | 1779篇 |
1999年 | 1322篇 |
1998年 | 934篇 |
1997年 | 753篇 |
1996年 | 597篇 |
1995年 | 440篇 |
1994年 | 358篇 |
1993年 | 258篇 |
1992年 | 182篇 |
1991年 | 150篇 |
1990年 | 130篇 |
1989年 | 121篇 |
1988年 | 70篇 |
1987年 | 73篇 |
1986年 | 45篇 |
1985年 | 36篇 |
1984年 | 26篇 |
1983年 | 20篇 |
1982年 | 18篇 |
1981年 | 20篇 |
1980年 | 11篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1975年 | 6篇 |
1959年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 36 毫秒
81.
介绍了一种新的探测雷达最小作用距离的方法,打破了传统的最小跟踪距离受发射脉宽局限的限制,重点介绍对发射线性调频信号的雷达的近距离探测方法,并给出了仿真计算结果。 相似文献
82.
83.
Kee S. Moon M. Levy Yong K. Hong H. Bakhru S. Bakhru 《Ferroelectrics Letters Section》2003,30(3):47-57
Advances in the fabrication of solid-solution single crystal relaxor ferroelectrics have made it possible to produce highly efficient piezoelectric crystals, and have attracted renewed interest in the use of these crystals for a new generation of piezoelectric transducers, actuators and sensors. Of particular interest is their incorporation into micro-electromechanical systems (MEMS). In this paper we report on the laser-induced wet chemical etching of lead zinc niobate-lead titanate (PZN-PT) in hydrochloric acid (HCl). Argon-ion laser radiation at power levels up to 4 W is focused to a spot diameter of about 15μm and results in the chemical etching of grooves at patterning speeds up to 5μm/sec. Crystal ion slicing, an ion-implant-based film separation technique, is used in combination with laser etching to form 5 to 10μm-thick patterned and freestanding films for incorporation into micro-electromechanical devices. 相似文献
84.
From its foundation until 2004, ETRI has registered over 1,000 US patents. This letter analyzes the characteristics of these patents and addresses the explanatory factors affecting their citation counts. For explanatory variables, research team related variables, invention specific variables, and geographical domain related variables are suggested. Zero‐altered count data models are used to test the impact of independent variables. A key finding is that technological cumulativeness, the scale of invention, outputs in the electronic field, and the degree of dependence on the US technology domain positively affect the citation counts of ETRI‐invented US patents. The magnitude of international presence appears to negatively affect the citation counts of ETRI‐invented US patents. 相似文献
85.
86.
87.
88.
A route to synthesize ZSM‐5 crystals with a bimodal micro/mesoscopic pore system has been developed in this study; the successful incorporation of the mesopores within the ZSM‐5 structure was performed using tetrapropylammonium hydroxide (TPAOH)‐impregnated mesoporous materials containing carbon nanotubes in the pores, which were encapsulated in the ZSM‐5 crystals during a solid rearrangement process within the framework. Such mesoporous ZSM‐5 zeolites can be readily obtained as powders, thin films, or monoliths. 相似文献
89.
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
90.
Jeong-Soo Lee Yang-Kyu Choi Daewon Ha Balasubramanian S. Tsu-Jae King Bokor J. 《Electron Device Letters, IEEE》2003,24(3):186-188
The hydrogen annealing process has been used to improve surface roughness of the Si-fin in CMOS FinFETs for the first time. Hydrogen annealing was performed after Si-fin etch and before gate oxidation. As a result, increased saturation current with a lowered threshold voltage and a decreased low-frequency noise level over the entire range of drain current have been attained. The low-frequency noise characteristics indicate that the oxide trap density is reduced by a factor of 3 due to annealing. These results suggest that hydrogen annealing is very effective for improving device performance and for attaining a high-quality surface of the etched Si-fin. 相似文献