全文获取类型
收费全文 | 4991篇 |
免费 | 498篇 |
国内免费 | 22篇 |
专业分类
电工技术 | 104篇 |
综合类 | 18篇 |
化学工业 | 1460篇 |
金属工艺 | 181篇 |
机械仪表 | 313篇 |
建筑科学 | 90篇 |
矿业工程 | 5篇 |
能源动力 | 242篇 |
轻工业 | 292篇 |
水利工程 | 19篇 |
石油天然气 | 14篇 |
武器工业 | 7篇 |
无线电 | 778篇 |
一般工业技术 | 1210篇 |
冶金工业 | 219篇 |
原子能技术 | 47篇 |
自动化技术 | 512篇 |
出版年
2024年 | 7篇 |
2023年 | 50篇 |
2022年 | 94篇 |
2021年 | 134篇 |
2020年 | 140篇 |
2019年 | 122篇 |
2018年 | 186篇 |
2017年 | 197篇 |
2016年 | 207篇 |
2015年 | 201篇 |
2014年 | 257篇 |
2013年 | 336篇 |
2012年 | 353篇 |
2011年 | 437篇 |
2010年 | 318篇 |
2009年 | 361篇 |
2008年 | 280篇 |
2007年 | 229篇 |
2006年 | 189篇 |
2005年 | 152篇 |
2004年 | 137篇 |
2003年 | 144篇 |
2002年 | 132篇 |
2001年 | 89篇 |
2000年 | 94篇 |
1999年 | 79篇 |
1998年 | 103篇 |
1997年 | 69篇 |
1996年 | 60篇 |
1995年 | 51篇 |
1994年 | 30篇 |
1993年 | 39篇 |
1992年 | 19篇 |
1991年 | 24篇 |
1990年 | 16篇 |
1989年 | 25篇 |
1988年 | 16篇 |
1987年 | 17篇 |
1986年 | 11篇 |
1985年 | 10篇 |
1984年 | 12篇 |
1983年 | 12篇 |
1982年 | 6篇 |
1980年 | 14篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 13篇 |
1976年 | 11篇 |
1974年 | 5篇 |
1973年 | 3篇 |
排序方式: 共有5511条查询结果,搜索用时 15 毫秒
101.
Gunhyu Bae Yoo Sang Jeon Min Jun Ko Yuri Kim Seong-Beom Han Ramar Thangam Wonsik Kim Hee Joon Jung Sungkyu Lee Hyojun Choi Sunhong Min Hyunsik Hong Sangwoo Park Seong Yeol Kim Kapil D. Patel Na Li Jeong Eun Shin Bum Chul Park Hyeon Su Park Jun Hwan Moon Yu Jin Kim Uday Kumar Sukumar Jae-Jun Song Soo Young Kim Seung-Ho Yu Yun Chan Kang Steve Park Seung Min Han Dong-Hwee Kim Ki-Bum Lee Qiang Wei Liming Bian Ramasamy Paulmurugan Young Keun Kim Heemin Kang 《Advanced functional materials》2021,31(37):2103409
Developing materials with the capability of changing their innate features can help to unravel direct interactions between cells and ligand-displaying features. This study demonstrates the grafting of magnetic nanohelices displaying cell-adhesive Arg-Gly-Asp (RGD) ligand partly to a material surface. These enable nanoscale control of rapid winding (“W”) and unwinding (“UW”) of their nongrafted portion, such as directional changes in nanohelix unwinding (lower, middle, and upper directions) by changing the position of a permanent magnet while keeping the ligand-conjugated nanohelix surface area constant. The unwinding (“UW”) setting cytocompatibility facilitates direct integrin recruitment onto the ligand-conjugated nanohelix to mediate the development of paxillin adhesion assemblies of macrophages that stimulate M2 polarization using glass and silicon substrates for in vitro and in vivo settings, respectively, at a single cell level. Real time and in vivo imaging are demonstrated that nanohelices exhibit reversible unwinding, winding, and unwinding settings, which modulate time-resolved adhesion and polarization of macrophages. It is envisaged that this remote, reversible, and cytocompatible control can help to elucidate molecular-level cell–material interactions that modulate regenerative/anti-inflammatory immune responses to implants. 相似文献
102.
Direct Graphene Transfer and Its Application to Transfer Printing Using Mechanically Controlled,Large Area Graphene/Copper Freestanding Layer 下载免费PDF全文
Jeongmin Seo Cheogyu Kim Boo Soo Ma Tae‐Ik Lee Jae Hoon Bong Joong Gun Oh Byung Jin Cho Taek‐Soo Kim 《Advanced functional materials》2018,28(26)
Direct graphene transfer is an attractive candidate to prevent graphene damage, which is a critical problem of the conventional wet transfer method. Direct graphene transfer can fabricate the transferred graphene film with fewer defects by using a polymeric carrier. Here a unique direct transfer method is proposed using a 300 nm thick copper carrier as a suspended film and a transfer printing process by using the polydimethylsiloxane (PDMS) stamp under controlled peeling rate and modulus. Single and multilayer graphene are transferred to flat and curved PDMS target substrate directly. With the transfer printing process, the transfer yield of a trilayer graphene with 1000 µm s?1 peeling rate is 68.6% of that with 1 µm s?1 peeling rate. It is revealed that the graphene transfer yield is highly related to the storage modulus of the PDMS stamp: graphene transfer yield decreases when the storage modulus of the PDMS stamp is lower than a specific threshold value. The relationship between the graphene transfer yield and the interfacial shear strain of the PDMS stamp is studied by finite‐element method simulation and digital image correlation. 相似文献
103.
Seul‐Ki Park So‐Eun Kim Dae‐Yoon Kim Shin‐Woong Kang Seunghan Shin Shiao‐Wei Kuo Seok‐Ho Hwang Seung Hee Lee Myong‐Hoon Lee Kwang‐Un Jeong 《Advanced functional materials》2011,21(11):2129-2139
Robust coatable polarizer is fabricated by the self‐assembly of lyotropic chromonic liquid crystals and subsequent photo‐polymerizing processes. Their molecular packing structures and optical behaviors are investigated by the combined techniques of microscopy, scattering and spectroscopy. To stabilize the oriented Sunset Yellow FCF (H‐SY) films and to minimize the possible defects generated during and after the coating, acrylic acid (AA) is added to the H‐SY/H2O solution and photo‐polymerized. Utilizing cross‐polarized optical microscopy, phase behaviors of the H‐SY/H2O/AA solution are monitored by varying the compositions and temperatures of the solution. Based on the experimental results of two‐dimensional wide angle X‐ray diffraction and selected area electron diffraction, the H‐SY crystalline unit cell is determined to be a monoclinic structure with the dimensions of a = 1.70 nm, b = 1.78 nm, c = 0.68 nm, α = β = 90.0° and γ = 84.5°. The molecular arrangements in the oriented H‐SY films were further confirmed by polarized Fourier‐transform infrared spectroscopy. The polymer‐stabilized H‐SY films show good mechanical and chemical stabilities with a high polarizability. Additionally, patterned polarizers are fabricated by applying a photo‐mask during the photo‐polymerization of AA, which may open new doors for practical applications in electro‐optic devices. 相似文献
104.
Ik Rae Jeong Jeong Ok Kwon Dong Hoon Lee 《Communications Letters, IEEE》2007,11(5):432-433
To provide authentication to the Diffie-Hellman key exchange, a few integrated key exchange schemes which provide authentication using the DSA signature have been proposed in the literature. In this letter we point out that all of the previous Diffie-Hellman-DSA schemes do not provide security against session state reveal attacks. We also suggest a strong Diffie-Hellman-DSA scheme providing security against session state reveal attacks as well as forward secrecy and key independence 相似文献
105.
In this letter, the constant driving power reduction ratio has been achieved for column drivers regardless of the input image by incorporating a new static power reduction scheme into the previous dynamic power reduction method. The measured power reduction ratio is around 50% for a 120 Hz liquid crystal display panel in such cases of still input video and fallback. 相似文献
106.
Byung-Seung Yim Yumi Kwon Seung Hoon Oh Jooheon Kim Yong-Eui Shin Seong Hyuk Lee Jong-Min Kim 《Microelectronics Reliability》2012,52(6):1165-1173
This study investigated the effect of the viscosity of the ECAs using a low-melting-point alloy (LMPA) filler on its bonding characteristics. The curing behaviors of the ECAs were determined using Differential Scanning Calorimetry (DSC), and ECA temperature-dependant viscosity characteristics were observed using a torsional parallel rheometer. The wetting test was conducted to investigate the reduction capability of ECAs and the flow-coalescence-wetting behavior of the LMPAs in ECAs. Electrical and mechanical properties were determined and compared to those with commercial ECAs and eutectic tin/lead (Sn/Pb) solder. In the metallurgically interconnected Quad Flat Package (QFP) joint, a typical scallop-type Cu–Sn intermetallic compound (IMC) layer formed at the upper SnBi/Cu interface after curing process. On the other hand, a (Cu, Ni)6Sn5 IMC layer formed on the SnBi/ENIG interface. In addition, the fracture surface exhibited by cleavage fracture mode and the fracture was propagated along the Cu–Sn IMC/SnBi interface. The extremely low-level viscosity of ECAs had a significant influence on the flow-coalescence-wetting behavior of the LMPAs in ECAs and also on the interconnection properties. Stable interconnected assemblies showed good electrical and mechanical properties. 相似文献
107.
Jongdae Kim Sang-Gi Kim Tae Moon Roh Hoon Soo Park Jin-Gun Koo Dae Yong Kim 《ETRI Journal》1999,21(3):22-28
A new tapered TEOS oxide technique has been developed to use field oxide of the power integrated circuits. It provides better uniformity of less than 3 % and reproducibility. On-resistance of P-channel RESURF (REduced SURface Field) LDMOS transistors has been optimized and improved by using a novel simulation and tapered TEOS field oxide on the drift region of the devices. With the similar breakdown voltage, at Vgs = ?5.0 V, the specific on-resistance of the LDMOS with the tapered field oxide is about 31.5 mΩ · cm2, while that of the LDMOS with the conventional field oxide is about 57 mΩ · cm2. 相似文献
108.
Ji-Seon Lee Jik Hyun Chang Dong Hoon Lee 《Communications Letters, IEEE》2009,13(5):292-293
Recently, Wu et al. discussed some security flaws of enhanced authentication scheme with anonymity for wireless environments proposed by Lee et al. and showed how to overcome the problems regarding anonymity and backward secrecy. However, in the paper, we will show that Wu et al.?s improved scheme still did not provide user anonymity as they claimed. 相似文献
109.
This paper investigates several power allocation policies in orthogonal frequency division multiplexing -based cognitive radio networks under the different availability of inter-system channel state information (CSI) and the different capability of licensed primary users (PUs). Specifically, we deal with two types of PUs having different capabilities: a dumb (peak interference-power tolerable) PU and a more sophisticated (average interference-power tolerable) PU. For such PU models, we first formulate two optimization problems that maximize the capacity of unlicensed secondary user (SU) while maintaining the quality of service of PU under the assumption that both intra- and inter-system CSI are fully available. However, due to loose cooperation between SU and PU, it may be difficult or even infeasible for SU to obtain the full inter-system CSI. Thus, under the partial inter-system CSI setting, we also formulate another two optimization problems by introducing interference-power outage constraints. We propose optimal and efficient suboptimal power allocation policies for these four problems. Extensive numerical results demonstrate that the spectral efficiency achieved by SU with partial inter-system CSI is less than half of what is achieved with full inter-system CSI within a reasonable range of outage probability (e.g., less than 10 %). Further, it is shown that the average interference-power tolerable PU can help to increase the saturated spectral efficiency of SU by about 20 and 50 % in both cases of full and partial inter-system CSI, respectively. 相似文献
110.
This work describes mitigation methods against Sn whisker growth in Pb-free automotive electronics using a conformal coating technique, with an additional focus on determining an effective whisker assessment method. We suggest effective whisker growth conditions that involve temperature cycling and two types of storage conditions (high-temperature/humidity storage and ambient storage), and analyze whisker growth mechanisms. In determining an efficient mitigation method against whisker growth, surface finish and conformal coating have been validated as effective means. In our experiments, the surface finish of components comprised Ni/Sn, Ni/SnBi, and Ni/Pd. The effects of acrylic silicone, and rubber coating of components were compared with uncoated performance under high-temperature/humidity storage conditions. An effective whisker assessment method during temperature cycling and under various storage conditions (high temperature/humidity and ambient) is indicated for evaluating whisker growth. Although components were finished with Ni/Pd, we found that whiskers were generated at solder joints and that conformal coating is a useful mitigation method in this regard. Although whiskers penetrated most conformal coating materials (acrylic, silicone, and rubber) after 3500 h of high-temperature/humidity storage, the whisker length was markedly reduced due to the conformal coatings, with silicone providing superior mitigation over acrylic and rubber. 相似文献