全文获取类型
收费全文 | 249篇 |
免费 | 10篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 4篇 |
综合类 | 1篇 |
化学工业 | 27篇 |
金属工艺 | 4篇 |
机械仪表 | 6篇 |
建筑科学 | 1篇 |
能源动力 | 8篇 |
轻工业 | 8篇 |
水利工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 66篇 |
一般工业技术 | 55篇 |
冶金工业 | 35篇 |
原子能技术 | 2篇 |
自动化技术 | 41篇 |
出版年
2023年 | 4篇 |
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 8篇 |
2015年 | 8篇 |
2014年 | 7篇 |
2013年 | 16篇 |
2012年 | 12篇 |
2011年 | 14篇 |
2010年 | 5篇 |
2009年 | 10篇 |
2008年 | 15篇 |
2007年 | 13篇 |
2006年 | 9篇 |
2005年 | 13篇 |
2004年 | 12篇 |
2003年 | 8篇 |
2002年 | 12篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1999年 | 5篇 |
1998年 | 15篇 |
1997年 | 13篇 |
1996年 | 4篇 |
1995年 | 7篇 |
1994年 | 1篇 |
1993年 | 4篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 5篇 |
1988年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1976年 | 2篇 |
排序方式: 共有260条查询结果,搜索用时 15 毫秒
71.
72.
Gao Y Zheng Y Diao S Toh WD Ang CW Je M Heng CH 《IEEE transactions on bio-medical engineering》2011,58(3):768-772
An integrated CMOS ultrawideband wireless telemetry transceiver for wearable and implantable medical sensor applications is reported in this letter. This high duty cycled, noncoherent transceiver supports scalable data rate up to 10 Mb/s with energy efficiency of 0.35 nJ/bit and 6.2 nJ/bit for transmitter and receiver, respectively. A prototype wireless capsule endoscopy using the proposed transceiver demonstrated in vivo image transmission of 640 × 480 resolution at a frame rate of 2.5 frames/s with 10 Mb/s data rate. 相似文献
73.
Multiple prompt γ-ray analysis (MPGA) and conventional neutron-induced prompt γ-ray analysis (PGA) are nondestructive analytical methods for bulk chemical compositions, and their analytical capabilities were compared for elemental analyses of geological and cosmochemical samples. Detection sensitivities of PGA are often restricted by poor signal-to-noise ratios and interferences from different origins. MPGA can substantially reduce the background level, especially for hydrogenous samples, relative to PGA, which opens up a possibility to use lower energy prompt γ-rays of some trace elements. Although it is one of the major constituent elements of rock samples, Mg is hard to be determined by PGA. With MPGA, Mg contents could be determined with reasonable consistency with their corresponding recommended values in geological and cosmochemical samples by carefully selecting suitable coincident prompt γ-ray energy pairs without interference correction. MPGA was applied to a hydrogenous meteorite, Ivuna, which contains H at 2% mass level. MPGA detection limits for most of the elements studied can be reduced up to 1 order of magnitude when compared with PGA detection limits under the present experimental conditions. 相似文献
74.
M Takechi Y Miyamoto K Ishikawa T Toh T Yuasa M Nagayama K Suzuki 《Canadian Metallurgical Quarterly》1998,19(22):2057-2063
Anti-washout-type fast-setting calcium phosphate cement using chitosan (aw-FSCPC(chi)), conventional CPC (c-CPC), CPC mixed with citric acid (CPC(citric)) and CPC mixed with polyacrylic acid (CPC(acrylic)) were implanted subcutaneously in rats immediately after mixing to shed some light on the understanding of the appearance of excellent tissue response to CPC. CPC(citric) and CPC(acrylic) set quickly, similar to aw-FSCPC(chi), but the former two stopped their transformation to apatitic minerals. The c-CPC, which required a long setting time, was found to be crumbled, but the other CPCs maintained the shape at implantation. The aw-FSCPC(chi) and CPC(citric) showed no inflammatory response whereas c-CPC and CPC(acrylic) showed an inflammatory response one week after implantation. A component of the aw-FSCPC(chi) and c-CPC was an apatitic mineral whereas CPC(citric) and CPC(acrylic) showed no transformation to apatite. We concluded that the non-crumbling property plays a more dominant role in the appearance of excellent tissue response to CPC than the transformation to apatite. Also, a non-crumbling property is not a sufficient condition, but a necessary condition for the appearance of the excellent tissue response to CPC. 相似文献
75.
In this paper, an active Pon type retrodirective array (RDA) is augmented with a passive array in order to provide electronic modification of the transmit function of the combination in response to the influence of an external interrogating signal. By the use of a single phase shifter and level setting control, it will be shown that different types of broadcast mode can be initiated. The first of these is the self-tracking capability normally associated with a Pon heterodyne RDA. Broadside radiation production associated with a conventional in-phase fed passive array operating in transmission mode is also demonstrated. Additionally, new modes of operation which include the use of the configuration are described: 1) as a radiation nulling device; 2) its use as a sidelobe suppressor; and 3) as a beamwidth control device 相似文献
76.
A method for efficiently implementing super exponential (SE) blind equalisation is proposed. The method, based on fast Kalman filtering theory, is recursive in order and in time, and leads to a significant reduction in the number of arithmetic operations. Using the order update by partitioning the covariance matrix of the first hundred data in a specific form, a fast initialisation is implemented. The resulting algorithm achieves the same theoretical fast convergence characteristics as the original SE algorithm but with a significant reduction in arithmetic operations 相似文献
77.
An incremental rigid-plastic finite element method is used to predict the forming limit curves (FLCs) of sheet materials. In this analysis, the deforming sheet materials is assumed to obey Hill's anisotropic yield criterion and its associated flow rule. To obtain the critical strain paths in both the positive and negative minor strain regions, simulations are performed using hemispherical punch stretching of a circular blank with various circular cutoffs and various friction conditions at the tool-sheet interface. A critical slope condition derived from the computed load-displacement curve is employed as a criterion to determine the limiting major and minor strains. FLCs of several sheet materials are predicted and the results are compared with the existing experimental data. 相似文献
78.
Kai-Yap Toh Ching-Te Chuang Tze-Chiang Chen Warnock J.D. 《Solid-State Circuits, IEEE Journal of》1989,24(5):1301-1306
An emitter-coupled logic (ECL) gate with an AC-coupled active pull-down emitter-follower stage that gives high speed at lower power is described. Significant reduction of the speed-power product can be achieved over the conventional ECL gate. The speed/power advantages of the circuit have been demonstrated in a double-poly, trench-isolated, self-aligned bipolar process with 0.8- mu m (mask) emitter width. Unloaded gate delays of 21 ps at 4.1 mW/gate, 23 ps at 2.1 mW/gate, and 35 ps at 1.1 mW/gate have been measured.<> 相似文献
79.
Tong Yan Tee Chek Lim Kho Daniel Yap Carol Toh Xavier Baraton Zhaowei Zhong 《Microelectronics Reliability》2003,43(5):741-749
In the flip-chip ball grid array (FCBGA) assembly process, no-flow underfill has the advantage over traditional capillary-flow underfill on shorter cycle time. Reliability tests are performed on both unmolded and molded FCBGA with three different types of no-flow underfill materials. The JEDEC Level-3 (JL3) moisture preconditioning, followed by reflow and pressure cooker test (PCT) is found to be a critical test for failures of underbump metallization (UBM) opening and underfill/die delamination. In this paper, various types of modeling techniques are applied to analyze the FCBGA-8×8 mm on moisture distribution, hygroswelling behavior, and thermomechanical stress. For moisture diffusion modeling, thermal-moisture analogy is used to calculate the degree of moisture saturation in the multi-material system of FCBGA. The local moisture concentration along the critical interface, e.g. die/underfill, is critical for delamination, because the moisture weakens the interfacial adhesion strength, generates internal vapor pressure during reflow, and induces tensile hygroswelling stress on UBM during PCT. The results of moisture distribution can be used as loading input for the subsequent hygroswelling modeling. The magnitude of hygroswelling stress acting on UBM is found to be greater than the thermal stress induced during reflow, both in tensile mode which may cause the UBM-opening failure. Underfill with lower saturated moisture concentration (Csat) and coefficient of moisture expansion (CME) are found to induce lower UBM stress and has better reliability results. Molded package generally has higher stress level than unmolded package. Parametric studies are performed to study the effects of no-flow underfill materials, package type (molded vs. unmolded), die thickness, and substrate size on the stresses of UBM during reflow and PCT. 相似文献
80.
Localized surface plasmon resonance (LSPR) spectroscopy of metallic nanoparticles is a powerful tool for chemical and biological sensing experiments. In this study, we observed LSPR shifts of 11-mercaptoundecanoic acid modified gold nanorods (GNR-MUA) for the pH range of 6.41 to 8.88. We proposed a mechanism involving changes of the dipole moment after protonation/deprotonation carboxylic groups of 11-mercaptoundecanoic acid (MUA) which plays an important role by modulating LSPR around the functionalized GNR. Such a stable and easily prepared GNR-MUA has potential to become one of the most efficient and promising pH nanosensors to study intra- or extra-cellular pH in a wide range of chemical or biological systems. 相似文献