全文获取类型
收费全文 | 56958篇 |
免费 | 4814篇 |
国内免费 | 2933篇 |
专业分类
电工技术 | 3571篇 |
技术理论 | 4篇 |
综合类 | 4703篇 |
化学工业 | 8980篇 |
金属工艺 | 3483篇 |
机械仪表 | 3698篇 |
建筑科学 | 3398篇 |
矿业工程 | 1487篇 |
能源动力 | 1607篇 |
轻工业 | 5012篇 |
水利工程 | 1244篇 |
石油天然气 | 2323篇 |
武器工业 | 523篇 |
无线电 | 6905篇 |
一般工业技术 | 6091篇 |
冶金工业 | 3265篇 |
原子能技术 | 722篇 |
自动化技术 | 7689篇 |
出版年
2024年 | 159篇 |
2023年 | 526篇 |
2022年 | 1173篇 |
2021年 | 1588篇 |
2020年 | 1209篇 |
2019年 | 1095篇 |
2018年 | 1271篇 |
2017年 | 1366篇 |
2016年 | 1394篇 |
2015年 | 1990篇 |
2014年 | 2618篇 |
2013年 | 3491篇 |
2012年 | 3975篇 |
2011年 | 4267篇 |
2010年 | 3976篇 |
2009年 | 4029篇 |
2008年 | 4198篇 |
2007年 | 4133篇 |
2006年 | 3874篇 |
2005年 | 3196篇 |
2004年 | 2514篇 |
2003年 | 1906篇 |
2002年 | 1805篇 |
2001年 | 1533篇 |
2000年 | 1289篇 |
1999年 | 989篇 |
1998年 | 1007篇 |
1997年 | 790篇 |
1996年 | 608篇 |
1995年 | 500篇 |
1994年 | 447篇 |
1993年 | 333篇 |
1992年 | 230篇 |
1991年 | 206篇 |
1990年 | 150篇 |
1989年 | 173篇 |
1988年 | 123篇 |
1987年 | 90篇 |
1986年 | 75篇 |
1985年 | 52篇 |
1984年 | 51篇 |
1983年 | 37篇 |
1982年 | 30篇 |
1981年 | 38篇 |
1980年 | 29篇 |
1979年 | 23篇 |
1978年 | 24篇 |
1977年 | 21篇 |
1976年 | 34篇 |
1973年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
新型的芯片间互连用CMOS/BiCMOS驱动器 总被引:5,自引:2,他引:3
从改善不同类型 IC芯片之间的电平匹配和驱动能力出发 ,设计了几例芯片间接口 (互连 )用 CMOS/Bi CMOS驱动电路 ,并提出了采用 0 .5 μm Bi CMOS工艺 ,制备所设计驱动器的技术要点和元器件参数。实验结果表明所设计驱动器既具有双极型电路快速、大电流驱动能力的特点 ,又具备 CMOS电路低压、低功耗的长处 ,因而它们特别适用于低电源电压、低功耗高速数字通信电路和信息处理系统。 相似文献
42.
Young-Geun Han Sang Hyuck Kim Sang Bae Lee Un-Chul Paek Youngjoo Chung 《Electronics letters》2003,39(15):1107-1108
A novel fabrication method of the core mode blocker by exposing H/sub 2/-loaded Ge-B codoped fibres to local electric arc discharge for application to the LPFGs-based tunable all-fibre bandpass filter with 6.5 nm bandwidth and 40 nm tuning range is presented. 相似文献
43.
An Ping Zhao 《Microwave and Wireless Components Letters, IEEE》2004,14(5):248-249
For original paper see Wang and Teixeira (IEEE Microwave Wireless Comp. Lett., vol.13, p.72-4, 2003 February). In this paper, a more precise way to evaluate the actual performance of the perfectly matched layer (PML) used for the alternating direction implicit finite-difference time-domain (ADI-FDTD) method is presented. It is shown that the intrinsic numerical dispersion error of the ADI-FDTD method must be taken into account when the actual performance of the ADI-PML (as well as the ADI-FDTD method) is evaluated. Most importantly, it is demonstrated that the ADI-PMLs implemented with either the traditional manner or the way proposed in have almost the same level of accuracy when the performance of the ADI-PML is correctly evaluated. 相似文献
44.
45.
量子密码技术被认为是绝对安全的加密技术。近年来,在美国、德国、日本和中国,相关研究都取得了明显进展。2004年6月,世界上第一个量子密码通信网络在美国马萨诸塞州剑桥城正式投入运行,标志着这一技术迈上了新台阶。据相关机构估算,量子保密通信系统一旦商用,将形成高达10亿美元的市场。 相似文献
46.
Derivation of a second-order switching surface in the boundary control of buck converters 总被引:1,自引:0,他引:1
A second-order switching surface in the boundary control of buck converters is derived in this letter. The formulated switching surface can make the overall converter exhibit better steady-state and transient behaviors than the one with a first-order switching surface. The switching surface is derived by estimating the state trajectory movement after a switching action, resulting in a high state trajectory velocity along the switching surface. This phenomenon accelerates the trajectory moving toward the target operating point. The proposed control scheme has been successfully applied to a 120-W buck converter. The large-signal performance and a comparison with the first-order switching surface have been studied. 相似文献
47.
蓝牙与IEEE802.11g无线局域网(Wireless Local Area Network,WLAN)都工作在2.4GHz频段上,因此它们之间存在一定的干扰。分析了蓝牙与IEEE802.11g通信系统之间的干扰,并提出了解决这一问题的两种方法:自适应跳频和删除标记法,并对两种方法的性能做了比较。 相似文献
48.
49.
On the capacities of bipartite Hamiltonians and unitary gates 总被引:2,自引:0,他引:2
Bennett C.H. Harrow A.W. Leung D.W. Smolin J.A. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2003,49(8):1895-1911
We consider interactions as bidirectional channels. We investigate the capacities for interaction Hamiltonians and nonlocal unitary gates to generate entanglement and transmit classical information. We give analytic expressions for the entanglement generating capacity and entanglement-assisted one-way classical communication capacity of interactions, and show that these quantities are additive, so that the asymptotic capacities equal the corresponding 1-shot capacities. We give general bounds on other capacities, discuss some examples, and conclude with some open questions. 相似文献
50.
McConaghy T. Leung H. Bosse E. Varadan V. 《IEEE transactions on instrumentation and measurement》2003,52(6):1771-1779
Radial basis function (RBF) neural networks are used to classify real-life audio radar signals that are collected by a ground surveillance radar mounted on a tank. Currently, a human operator is required to operate the radar system to discern among signals bouncing off tanks, vehicles, planes, and so on. The objective of this project is to investigate the possibility of using a neural network to perform this target recognition task, with the aim of reducing the number of personnel required in a tank. Different signal classification methods in the neural net literature are considered. The first method employs a linear autoregressive (AR) model to extract linear features of the audio data, and then perform classification on these features, i.e, the AR coefficients. AR coefficient estimations based on least squares and higher order statistics are considered in this study. The second approach uses nonlinear predictors to model the audio data and then classifies the signals according to the prediction errors. The real-life audio radar data set used here was collected by an AN/PPS-15 ground surveillance radar and consists of 13 different target classes, which include men marching, a man walking, airplanes, a man crawling, and boats, etc. It is found that each classification method has some classes which are difficult to classify. Overall, the AR feature extraction approach is most effective and has a correct classification rate of 88% for the training data and 67% for data not used for training. 相似文献