全文获取类型
收费全文 | 359661篇 |
免费 | 27978篇 |
国内免费 | 15371篇 |
专业分类
电工技术 | 20339篇 |
技术理论 | 20篇 |
综合类 | 23778篇 |
化学工业 | 59715篇 |
金属工艺 | 18937篇 |
机械仪表 | 21843篇 |
建筑科学 | 28450篇 |
矿业工程 | 8985篇 |
能源动力 | 10436篇 |
轻工业 | 24445篇 |
水利工程 | 6340篇 |
石油天然气 | 18318篇 |
武器工业 | 2652篇 |
无线电 | 43137篇 |
一般工业技术 | 43431篇 |
冶金工业 | 18293篇 |
原子能技术 | 4230篇 |
自动化技术 | 49661篇 |
出版年
2024年 | 1426篇 |
2023年 | 5161篇 |
2022年 | 9465篇 |
2021年 | 13000篇 |
2020年 | 9795篇 |
2019年 | 8408篇 |
2018年 | 9198篇 |
2017年 | 10442篇 |
2016年 | 9772篇 |
2015年 | 12847篇 |
2014年 | 16874篇 |
2013年 | 21102篇 |
2012年 | 22422篇 |
2011年 | 24812篇 |
2010年 | 21589篇 |
2009年 | 21274篇 |
2008年 | 20489篇 |
2007年 | 19638篇 |
2006年 | 19739篇 |
2005年 | 17185篇 |
2004年 | 12504篇 |
2003年 | 11274篇 |
2002年 | 11482篇 |
2001年 | 10146篇 |
2000年 | 8992篇 |
1999年 | 9148篇 |
1998年 | 7936篇 |
1997年 | 6558篇 |
1996年 | 6009篇 |
1995年 | 5042篇 |
1994年 | 4073篇 |
1993年 | 3252篇 |
1992年 | 2512篇 |
1991年 | 1882篇 |
1990年 | 1563篇 |
1989年 | 1236篇 |
1988年 | 1038篇 |
1987年 | 722篇 |
1986年 | 571篇 |
1985年 | 476篇 |
1984年 | 324篇 |
1983年 | 280篇 |
1982年 | 231篇 |
1981年 | 191篇 |
1980年 | 178篇 |
1979年 | 133篇 |
1978年 | 82篇 |
1977年 | 93篇 |
1976年 | 107篇 |
1975年 | 54篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
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
43.
Studies on the deactivations and initiations of gas phase polymerizations of 1,3‐butadiene have been achieved by Monte Carlo simulation. Initiation and deactivation control the reaction before and after the peak of the polymerization rate, respectively. The influence of polymerization temperature has been studied. Monte Carlo modeling of polymerization kinetics and mechanism was confirmed by the agreement of experimental data and simulation results of polymerizations run with a temporary evacuation of monomer. The balance of catalysts and active chains is established by both initiation and chain transfer reactions with cocatalyst, which causes a ‘pseudo‐stability’ stage. © 2003 Society of Chemical Industry 相似文献
44.
45.
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
46.
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
47.
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
48.
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
49.
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
50.
随机激光器的最新进展 总被引:5,自引:2,他引:3
综述了近年来随机激光器的最新研究结果,包括随机激光产生的机制,随机增益介质的制备方法,随机激光器的激励与发光特性和随机激光理论。最后,介绍了随机激光器的应用前景。 相似文献