全文获取类型
收费全文 | 62071篇 |
免费 | 5671篇 |
国内免费 | 2684篇 |
专业分类
电工技术 | 3636篇 |
技术理论 | 4篇 |
综合类 | 3657篇 |
化学工业 | 10342篇 |
金属工艺 | 3540篇 |
机械仪表 | 4191篇 |
建筑科学 | 4333篇 |
矿业工程 | 1762篇 |
能源动力 | 1947篇 |
轻工业 | 4542篇 |
水利工程 | 1184篇 |
石油天然气 | 2850篇 |
武器工业 | 553篇 |
无线电 | 7430篇 |
一般工业技术 | 8036篇 |
冶金工业 | 3172篇 |
原子能技术 | 872篇 |
自动化技术 | 8375篇 |
出版年
2024年 | 274篇 |
2023年 | 1060篇 |
2022年 | 1828篇 |
2021年 | 2598篇 |
2020年 | 1958篇 |
2019年 | 1748篇 |
2018年 | 1995篇 |
2017年 | 2107篇 |
2016年 | 2010篇 |
2015年 | 2566篇 |
2014年 | 3249篇 |
2013年 | 3892篇 |
2012年 | 4369篇 |
2011年 | 4657篇 |
2010年 | 3959篇 |
2009年 | 3856篇 |
2008年 | 3618篇 |
2007年 | 3349篇 |
2006年 | 3167篇 |
2005年 | 2665篇 |
2004年 | 2042篇 |
2003年 | 1850篇 |
2002年 | 1926篇 |
2001年 | 1656篇 |
2000年 | 1339篇 |
1999年 | 1305篇 |
1998年 | 1029篇 |
1997年 | 814篇 |
1996年 | 705篇 |
1995年 | 619篇 |
1994年 | 457篇 |
1993年 | 388篇 |
1992年 | 292篇 |
1991年 | 219篇 |
1990年 | 172篇 |
1989年 | 119篇 |
1988年 | 129篇 |
1987年 | 67篇 |
1986年 | 77篇 |
1985年 | 45篇 |
1984年 | 44篇 |
1983年 | 32篇 |
1982年 | 21篇 |
1981年 | 15篇 |
1980年 | 19篇 |
1979年 | 21篇 |
1978年 | 12篇 |
1977年 | 17篇 |
1976年 | 15篇 |
1975年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
On the SEP of Cooperative Diversity with Opportunistic Relaying 总被引:1,自引:0,他引:1
We analyze the exact symbol error probability (SEP) of cooperative diversity with opportunistic amplify-and-forward (AF) relaying. The benefit of this opportunism to the SEP is assessed by comparing with maximal ratio combining of orthogonal multiple AF relay transmissions. 相似文献
32.
Xin Sun Qiang Lu Moroz V. Takeuchi H. Gebara G. Wetzel J. Shuji Ikeda Changhwan Shin Tsu-Jae King Liu 《Electron Device Letters, IEEE》2008,29(5):491-493
A tri-gate bulk MOSFET design utilizing a low-aspect-ratio channel is proposed to provide an evolutionary pathway for CMOS scaling to the end of the roadmap. 3-D device simulations indicate that this design offers the advantages of a multi-gate FET (reduced variability in performance and improved scalability) together with the advantages of a conventional planar MOSFET (low substrate cost and capability for dynamic threshold-voltage control). 相似文献
33.
Dong Zhang 《Korean Journal of Chemical Engineering》2008,25(5):1205-1207
Ceria-zirconia solid particles have been recognized as a key material of the automotive exhaust catalysts since they can release
and uptake oxygen owing to the rapid reversible oxidation states of cerium between Ce3+ and Ce4+. Several methods have recently been described to prepare the CeO2-ZrO2 solid particles used in the catalysts. In this paper, a new coprecipitation method is used to prepare the CeO2-ZrO2 solid particles. The Ce-Zr alcogel is dried and calcined in flowing N2 not in flowing air under atmospheric pressure. The results show that the ceria-zirconia sample calcined at 650 °C has high
surface area over 90 m2g−1, which drops to 40 m2g−1 following treatment at 900°C. 相似文献
34.
35.
Mehra A. Indiresan A. Shin K.G. 《IEEE transactions on pattern analysis and machine intelligence》1997,23(10):616-634
We propose architectural mechanisms for structuring host communication software to provide QoS guarantees. We present and evaluate a QoS sensitive communication subsystem architecture for end hosts that provides real time communication support for generic network hardware. This architecture provides services for managing communication resources for guaranteed QoS (real time) connections, such as admission control, traffic enforcement, buffer management, and CPU and link scheduling. The architecture design is based on three key goals: maintenance of QoS guarantees on a per connection basis, overload protection between established connections, and fairness in delivered performance to best effort traffic. Using this architecture we implement real time channels, a paradigm for real time communication services in packet switched networks. The proposed architecture features a process per channel model that associates a channel handler with each established channel. The model employed for handler execution is one of “cooperative” preemption, where an executing handler yields the CPU to a waiting higher priority handler at well defined preemption points. The architecture provides several configurable policies for protocol processing and overload protection. We present extensions to the admission control procedure for real time channels to account for cooperative preemption and overlap between protocol processing and link transmission at a sending host. We evaluate the implementation to demonstrate the efficacy with which the architecture maintains QoS guarantees on outgoing traffic while adhering to the stated design goals 相似文献
36.
37.
Ku T.K. Chen S.H. Yang C.D. She N.J. Wang C.C. Chen C.F. Hsieh I.J. Cheng H.C. 《Electron Device Letters, IEEE》1996,17(5):208-210
Undoped and phosphorus (P)-doped diamond-clad Si field emitter arrays have been successfully fabricated using microwave plasma chemical vapor deposition (MPCVD) technology. The electron emission from the blunt diamond-clad microtips are much higher than those for the pure Si tips with sharp curvature due to a lower work function. Furthermore, the characteristics of emission current against applied voltage for the P-doped diamond-clad tips show superior emission at lower field to the undoped ones. After the examination of Auger electron spectroscopy (AES) and electrical characteristics of as-grown diamond, such a significant enhancement of the electron emission from the P-doped diamond-clad tips is attributed to a higher electron conductivity and defect densities 相似文献
38.
Kyeongho Lee Yeshik Shin Sungjoon Kim Deog-Kyoon Jeong Kim G. Kim B. Da Costa V. 《Solid-State Circuits, IEEE Journal of》1998,33(5):816-823
In a high-resolution flat panel system, a conventional interface that directly connects a liquid crystal display (LCD) controller to a flat panel cannot overcome the problems of excess EMI (electromagnetic interference) and power caused by full-swing transmission signals in parallel lines. This paper presents a high-speed digital video interface system implemented with a low-cost standard CMOS (complimentary metal-oxide-semiconductor) technology that can mitigate EMI and power problems in high-resolution flat panel display systems. The combined architecture of the high-speed, small number of parallel lines and low-voltage swing serial interface can support resolutions from VGA (640×480 pixels) up to XGA (1024×768 pixels) with significant power improvement and drastic EMI reduction. To support high-speed, low-voltage swing signaling and overcome channel-to-channel skew problems, a robust data recovery system is required. The proposed digital phase-locked loop enables robust skew-insensitive data recovery of up to 1.04 GBd 相似文献
39.
40.