全文获取类型
收费全文 | 90464篇 |
免费 | 7824篇 |
国内免费 | 4080篇 |
专业分类
电工技术 | 5688篇 |
技术理论 | 2篇 |
综合类 | 5778篇 |
化学工业 | 14017篇 |
金属工艺 | 4956篇 |
机械仪表 | 5215篇 |
建筑科学 | 6721篇 |
矿业工程 | 1853篇 |
能源动力 | 2647篇 |
轻工业 | 7088篇 |
水利工程 | 1811篇 |
石油天然气 | 3878篇 |
武器工业 | 675篇 |
无线电 | 12040篇 |
一般工业技术 | 11651篇 |
冶金工业 | 4620篇 |
原子能技术 | 1029篇 |
自动化技术 | 12699篇 |
出版年
2024年 | 370篇 |
2023年 | 1372篇 |
2022年 | 2574篇 |
2021年 | 3563篇 |
2020年 | 2502篇 |
2019年 | 2106篇 |
2018年 | 2358篇 |
2017年 | 2801篇 |
2016年 | 2456篇 |
2015年 | 3396篇 |
2014年 | 4447篇 |
2013年 | 5665篇 |
2012年 | 6040篇 |
2011年 | 6751篇 |
2010年 | 5857篇 |
2009年 | 5650篇 |
2008年 | 5585篇 |
2007年 | 5347篇 |
2006年 | 5122篇 |
2005年 | 4178篇 |
2004年 | 2844篇 |
2003年 | 2349篇 |
2002年 | 2370篇 |
2001年 | 2025篇 |
2000年 | 1912篇 |
1999年 | 1940篇 |
1998年 | 1827篇 |
1997年 | 1578篇 |
1996年 | 1412篇 |
1995年 | 1185篇 |
1994年 | 923篇 |
1993年 | 761篇 |
1992年 | 607篇 |
1991年 | 462篇 |
1990年 | 386篇 |
1989年 | 298篇 |
1988年 | 252篇 |
1987年 | 182篇 |
1986年 | 152篇 |
1985年 | 139篇 |
1984年 | 100篇 |
1983年 | 75篇 |
1982年 | 68篇 |
1981年 | 59篇 |
1980年 | 51篇 |
1979年 | 35篇 |
1978年 | 32篇 |
1977年 | 32篇 |
1976年 | 54篇 |
1973年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
Yen-Shin Lai Juo-Chiun Lin 《Power Electronics, IEEE Transactions on》2003,18(5):1211-1219
A new hybrid fuzzy controller for direct torque control (DTC) induction motor drives is presented in this paper. The newly developed hybrid fuzzy control law consists of proportional-integral (PI) control at steady state, PI-type fuzzy logic control at transient state, and a simple switching mechanism between steady and transient states, to achieve satisfied performance under steady and transient conditions. The features of the presented new hybrid fuzzy controller are highlighted by comparing the performance of various control approaches, including PI control, PI-type fuzzy logic control (FLC), proportional-derivative (PD) type FLC, and combination of PD-type FLC and I control, for DTC-based induction motor drives. The pros and cons of these controllers are demonstrated by intensive experimental results. It is shown that the presented induction motor drive is with fast tracking capability, less steady state error, and robust to load disturbance while not resorting to complicated control method or adaptive tuning mechanism. Experimental results derived from a test system are presented confirming the above-mentioned claims. 相似文献
72.
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
73.
74.
厂内一台B25汽轮机,因振动超差,进行了20个月的分析、计算和试验,最后发现中心孔内有250 g左右的油水化合物,造成转子热弯曲,激发汽轮机出现振动严重超标. 相似文献
75.
76.
从稳态到动态的空气调节 总被引:1,自引:0,他引:1
分析传统空调所提供的稳态参数微气候环境不一定能达到人的舒适和健康的要求,提出符合人本身生理习惯的空调送风方式应该是动态空气调节.认为个人可调节和适宜的环境渐变能同时保证舒适和健康两方面需要. 相似文献
77.
78.
Hao Wang Ying Lin Biao Chen 《Signal Processing, IEEE Transactions on》2003,51(10):2613-2623
We investigate non data-aided channel estimation for cyclically prefixed orthogonal frequency division multiplexing (OFDM) systems. By exploiting channel diversity using only two receive antennas, a blind deterministic algorithm is proposed. Identifiability conditions are derived that guarantee the perfect channel retrieval in the absence of noise. In the presence of noise, the proposed method has the desired property of being data efficient-only a single OFDM block is needed to achieve good estimation performance for a wide range of SNR values. The algorithm is also robust to input symbols as it does not have any restriction on the input symbols with regard to their constellation or their statistical properties. In addition, this diversity-based algorithm is computationally efficient, and its performance compares favorably to most existing blind algorithms. 相似文献
79.
优化项目管理MIS系统方案设计 总被引:2,自引:0,他引:2
按照工程项目“五制”管理的要求 ,以规范管理和提升工程质量为系统开发的基础和前提 ,探索适合本行业使用的项目MIS系统设计方案 ,并对其功能模型、数据规划、构造处理模型、数学模型进行分析 相似文献
80.
Yang C.W. Fang Y.K. Lin C.S. Tsair Y.S. Chen S.M. Wang W.D. Wang M.F. Cheng J.Y. Chen C.H. Yao L.G. Chen S.C. Liang M.S. 《Electronics letters》2003,39(21):1499-1501
A novel technique to form high-K dielectric of HfSiON by doping base oxide with Hf and nitridation with NH/sub 3/, sequentially, is proposed. The HfSiON gate dielectric demonstrates excellent device performances such as only 10% degradation of saturation drain current and almost 45 times of magnitude reduction in gate leakage compared with conventional SiO/sub 2/ gate at the approximately same equivalent oxide thickness. Additionally, negligible flatband voltage shift is achieved with this technique. Time-dependent dielectric breakdown tests indicate that the lifetime of HfSiON is longer than 10 years at V/sub dd/=2 V. 相似文献