全文获取类型
收费全文 | 842篇 |
免费 | 88篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 10篇 |
化学工业 | 162篇 |
金属工艺 | 45篇 |
机械仪表 | 72篇 |
建筑科学 | 12篇 |
能源动力 | 35篇 |
轻工业 | 109篇 |
水利工程 | 6篇 |
石油天然气 | 1篇 |
无线电 | 128篇 |
一般工业技术 | 221篇 |
冶金工业 | 54篇 |
原子能技术 | 12篇 |
自动化技术 | 64篇 |
出版年
2024年 | 2篇 |
2023年 | 19篇 |
2022年 | 16篇 |
2021年 | 31篇 |
2020年 | 18篇 |
2019年 | 33篇 |
2018年 | 43篇 |
2017年 | 33篇 |
2016年 | 41篇 |
2015年 | 43篇 |
2014年 | 58篇 |
2013年 | 64篇 |
2012年 | 86篇 |
2011年 | 84篇 |
2010年 | 54篇 |
2009年 | 50篇 |
2008年 | 40篇 |
2007年 | 40篇 |
2006年 | 24篇 |
2005年 | 32篇 |
2004年 | 16篇 |
2003年 | 24篇 |
2002年 | 11篇 |
2001年 | 10篇 |
2000年 | 7篇 |
1999年 | 7篇 |
1998年 | 13篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1990年 | 2篇 |
1987年 | 3篇 |
排序方式: 共有931条查询结果,搜索用时 31 毫秒
81.
The carbide growth kinetics enhanced in grain interiors is mainly due to the increased diffusivity in the direction normal
to the tensile stress. The accelerated kinetics at the grain boundaries normal to the tensile stress is due to the increased
grain boundary energy and the widened grain boundary path producing the increased diffusivity in the direction normal to the
tensile stress. A strong segregation behavior of impurities to the grain boundary carbide interfaces follows the enhanced
grain boundary carbide growth kinetics. 相似文献
82.
83.
Yasantha Athukorala Ki‐Wan Lee Eun‐Ju Park Moon‐Soo Heo In‐Kyu Yeo Young‐Don Lee You‐Jin Jeon 《Journal of the science of food and agriculture》2005,85(14):2341-2348
The antioxidant activity of an extract of Grateloupia filicina was evaluated using linoleic acid and fish oil as substrates in an induct period at 65 °C. Furthermore, the algal extract was subjected to comet assay to evaluate its protecting ability for H2O2‐induced DNA damage in rat lymphocytes. Progression of oxidation was examined using weight gain, peroxide value (PV), 2‐thiobarbituric acid reactive substances and conjugated diene data. Effectiveness of the extract at 0.03 and 0.05% levels was superior to that of α‐tocopherol at 0.01% and the activity of 0.05% extract was higher than that of butylated hydroxyanisole and butylated hydroxytoluene at 0.01%. Also, the algal extract significantly inhibited H2O2 induced DNA damage in comet assay. The maximum DNA damage inhibition (68.9%) was recorded from the 50 µg ml−1 alga extract when the rat lymphocyte cells were treated with 50 µM H2O2. Copyright © 2005 Society of Chemical Industry 相似文献
84.
Keun Heo JuHwan Lim Mun J. SungWoo Hwang 《Microwave and Wireless Components Letters, IEEE》2007,17(3):160-162
We report fabrication of miniaturized low temperature co-fired ceramic helical (3-D) inductors with more than seven layers of helices and the conductor linewidth of 100mum. We achieve the QmaxLeff/A product ranging from 200 to 370. Such high values are possible thanks to the drastic reduction of the active area and still acceptably large Qmax and self-resonant frequency. High frequency characterization of the inductors is performed up to 12GHz, and a new equivalent circuit model considering vertical electromagnetic coupling between conductors is shown to reproduce all the measured characteristics 相似文献
85.
Abstract. The objective of this paper is to develop default priors when the parameter of interest is the autocorrelation coefficient in normal regression models with first-order autoregressive residuals. Jeffreys' prior as well as reference priors are found. These priors are compared in the light of how accurately the coverage probabilities of Bayesian credible intervals match the corresponding frequentist coverage probabilities. It is found that the reference priors have a definite edge over Jeffreys' prior in this respect. Also, the credible intervals based on these reference priors seem superior to similar intervals based on certain divergence measures. 相似文献
86.
87.
Duchang Heo Il Ki Han Jung Il Lee Jichai Jeong 《Photonics Technology Letters, IEEE》2004,16(8):1801-1803
We studied symmetric and asymmetric InGaAsP-InGaAs 1.55-/spl mu/m multiquantum-well (MQW) laser diodes (LDs) with highly p-doped layers in the two-step separate confinement heterostructure (SCH). The p-doping in p-SCH suppresses the electron overflow from the MQWs to p-SCH, but it is an origin of free carrier absorption loss. An additional InGaAsP layer inserted inside n-SCH makes asymmetric field distribution and, therefore, reduces the portion of optical field distribution in highly p-doped regions with high optical loss. Compared with symmetric structure, asymmetric SCH LD has low threshold current density, low internal loss, and high and flat slope efficiency with respect to temperature. 相似文献
88.
Keun Byoung Yoon In-Kui Cho Seung Ho Ahn Myung Yong Jeong Deug Ju Lee Young Un Heo Byung Sup Rho Hyo-Hoon Park Byoung-Ho Rhee 《Lightwave Technology, Journal of》2004,22(9):2119-2127
As discussed in this paper, a practical optical backplane system was demonstrated, using a waveguide-embedded optical backplane board, processing boards, and optical slots for board-to-board interconnection. A metal optical bench was used as a packaging die for the optical devices and the integrated circuit chips in both the transmitter and the receiver processing boards. The polymer waveguide was produced by means of a hot-embossing technique and was then embedded following a conventional lamination processes. The average propagation loss of these waveguides was approximately 0.1 dB/cm at 850 nm. The dimension and optical properties of the waveguide in an optical backplane board were unchanged after lamination. As connection components between transmitter/receiver processing boards and an optical backplane board, optical slots were used for easy and repeatable insertion and extraction of the boards with a micrometer-scale precision. A 1/spl times/4 850-nm vertical-cavity surface-emitting laser array was used with 2 dBm of output power for the transmitter and a p-i-n photodiode array for the receiver. This paper successfully demonstrates 8 Gb/s of data transmission between the transmitter processing board and the optical backplane board. 相似文献
89.
Efficient design of device-to-device (D2D) communication calls for D2D users to propose adaptive power allocation strategy and to establish reliable communication links while protecting the QoS of cellular communications. In this paper, we consider the D2D communication as an underlay to relay-assisted cellular networks. To maximize the ergodic capacity, we derive an optimal transmission power under an average power constraint. With the derived optimal transmission power, a transmission period selection strategy for D2D communication is firstly introduced to improve reliability. We derive the outage probability in closed forms and evaluate the ergodic capacity to show performances of the proposed system. Numerical results show that the D2D system can achieve high capacity gains by flexibly allocating transmission power based on channel state information and significantly enhance reliability by selecting a transmission period, while satisfying various QoS conditions for cellular communication. 相似文献
90.
This paper presents a Rate-Compatible Block Turbo Code (RC-BTC) with increased transmission capacity. The proposed RC-BTC uses a new algorithm called information augmenting scheme, and can achieve a higher code rate than conventional one. A new Error Location Finding (ELF) Decoding Algorithm is introduced to solve the decoding problem of the information augmenting scheme. As a result, a novel error-correcting capability of the BTC-applied Chase-ELF Hybrid Decoder, combining the previous Chase–Pyndiah algorithm and the proposed ELF algorithm, is demonstrated via Monte-Carlo simulation. In addition, the proposed code maximally increases the transmission capacity with the Chase-ELF Hybrid decoder using an information augmenting scheme. 相似文献