全文获取类型
收费全文 | 48895篇 |
免费 | 13122篇 |
国内免费 | 31篇 |
专业分类
电工技术 | 889篇 |
综合类 | 33篇 |
化学工业 | 18696篇 |
金属工艺 | 671篇 |
机械仪表 | 1189篇 |
建筑科学 | 1897篇 |
矿业工程 | 5篇 |
能源动力 | 1225篇 |
轻工业 | 7660篇 |
水利工程 | 322篇 |
石油天然气 | 71篇 |
无线电 | 8706篇 |
一般工业技术 | 12963篇 |
冶金工业 | 1749篇 |
原子能技术 | 128篇 |
自动化技术 | 5844篇 |
出版年
2023年 | 81篇 |
2022年 | 159篇 |
2021年 | 382篇 |
2020年 | 1531篇 |
2019年 | 3255篇 |
2018年 | 3241篇 |
2017年 | 3529篇 |
2016年 | 4048篇 |
2015年 | 4089篇 |
2014年 | 4162篇 |
2013年 | 5501篇 |
2012年 | 3164篇 |
2011年 | 2936篇 |
2010年 | 3084篇 |
2009年 | 3069篇 |
2008年 | 2538篇 |
2007年 | 2350篇 |
2006年 | 2060篇 |
2005年 | 1717篇 |
2004年 | 1679篇 |
2003年 | 1613篇 |
2002年 | 1577篇 |
2001年 | 1342篇 |
2000年 | 1290篇 |
1999年 | 692篇 |
1998年 | 621篇 |
1997年 | 368篇 |
1996年 | 272篇 |
1995年 | 212篇 |
1994年 | 196篇 |
1993年 | 175篇 |
1992年 | 107篇 |
1991年 | 133篇 |
1990年 | 96篇 |
1989年 | 101篇 |
1988年 | 69篇 |
1987年 | 75篇 |
1986年 | 70篇 |
1985年 | 62篇 |
1984年 | 52篇 |
1983年 | 42篇 |
1982年 | 31篇 |
1981年 | 45篇 |
1980年 | 31篇 |
1979年 | 18篇 |
1978年 | 28篇 |
1977年 | 31篇 |
1976年 | 36篇 |
1975年 | 18篇 |
1973年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Penta‐Twinned Copper Nanorods: Facile Synthesis via Seed‐Mediated Growth and Their Tunable Plasmonic Properties 下载免费PDF全文
Ming Luo Aleksey Ruditskiy Hsin‐Chieh Peng Jing Tao Legna Figueroa‐Cosme Zhike He Younan Xia 《Advanced functional materials》2016,26(8):1209-1216
The use of seed‐mediated growth as a versatile approach to the synthesis of penta‐twinned Cu nanorods with uniform diameters and controllable aspect ratios is reported. The success of this approach relies on our recent synthesis of uniform Pd decahedra, with sizes in the range of 6–20 nm. The Pd decahedral seeds can direct the heterogeneous nucleation and growth of Cu along the fivefold axis to produce nanorods with uniform diameters defined by the lateral dimension of the original seeds. Due to a large mismatch in the lattice constants between Cu and Pd (7.1%), the deposited Cu is forced to grow along one side of the Pd decahedral seed, generating a nanorod with an asymmetric distribution of Cu, with the Pd seed situated at one of the two ends. According to extinction spectra, the as‐obtained Cu nanorods can be stored in water under the ambient conditions for at least six months without noticeable degradation. This excellent stability allows us to systematically investigate the size‐dependent surface plasmon resonance properties of the penta‐twinned Cu nanorods. With the nanorod transverse modes positioned at 560 nm, the longitudinal modes can be readily tuned from the visible to the near‐infrared region by controlling the aspect ratio. 相似文献
992.
3D Graphene Films Enable Simultaneously High Sensitivity and Large Stretchability for Strain Sensors 下载免费PDF全文
Fei Pan Si‐Ming Chen Yuhan Li Zhuchen Tao Jianglin Ye Kun Ni Han Yu Bin Xiang Yibin Ren Faxiang Qin Shu‐Hong Yu Yanwu Zhu 《Advanced functional materials》2018,28(40)
Integration of 2D membranes into 3D macroscopic structures is essential to overcome the intrinsically low stretchability of graphene for the applications in flexible and wearable electronics. Herein, the synthesis of 3D graphene films (3D‐GFs) using chemical vapor deposition (CVD) is reported, in which a porous copper foil (PCF) is chosen as a template in the atmospheric‐pressure CVD preparation. When the 3D‐GF prepared at 1000 °C (noted as 3D‐GF‐1000) is transferred onto a polydimethylsiloxane (PDMS) membrane, the obtained 3D‐GF‐1000/PDMS hybrid film shows an electrical conductivity of 11.6 S cm?1 with good flexibility, indicated by small relative resistance changes (ΔR/R0) of 2.67 and 0.36 under a tensile strain of 50% and a bending radius of 1.6 mm, respectively. When the CVD temperature is reduced to 900 °C (generating a sample noted as 3D‐GF‐900), the 3D‐GF‐900/PDMS hybrid film exhibits an excellent strain‐sensing performance with a workable strain range of up to 187% and simultaneously a gauge factor of up to ≈1500. The 3D‐GF‐900/PDMS also shows a remarkable durability in resistance in repeated 5000 stretching‐releasing cycles. Kinetics studies show that the response of ΔR/R0 upon strain is related to the graphitization and conductivity of 3D‐GF which are sensitive to the CVD preparation temperature. 相似文献
993.
Color demosaicing using variance of color differences. 总被引:2,自引:0,他引:2
This paper presents an adaptive demosaicing algorithm. Missing green samples are first estimated based on the variances of the color differences along different edge directions. The missing red and blue components are then estimated based on the interpolated green plane. This algorithm can effectively preserve the details in texture regions and, at the same time, it can significantly reduce the color artifacts. As compared with the latest demosaicing algorithms, the proposed algorithm produces the best average demosaicing performance both objectively and subjectively. 相似文献
994.
Cong Chen Yue Jiang Jiali Guo Xiayan Wu Wenhui Zhang Sujuan Wu Xingsen Gao Xiaowen Hu Qianming Wang Guofu Zhou Yiwang Chen Jun‐Ming Liu Krzysztof Kempa Jinwei Gao 《Advanced functional materials》2019,29(30)
A high‐quality polycrystalline SnO2 electron‐transfer layer is synthesized through an in situ, low‐temperature, and unique butanol–water solvent‐assisted process. By choosing a mixture of butanol and water as a solvent, the crystallinity is enhanced and the crystallization temperature is lowered to 130 °C, making the process fully compatible with flexible plastic substrates. The best solar cells fabricated using these layers achieve an efficiency of 20.52% (average 19.02%) which is among the best in the class of planar n–i–p‐type perovskite (MAPbI3) solar cells. The strongly reduced crystallization temperature of the materials allows their use on a flexible substrate, with a resulting device efficiency of 18%. 相似文献
995.
MMSE‐based transceiver design for distributed MIMO amplify‐and‐forward cooperative networks in correlated channels 下载免费PDF全文
Chia‐Chang Hu Wei‐Yu Liang Guan‐Yi Li 《International Journal of Communication Systems》2014,27(10):1686-1701
In this paper, the source‐precoder, multiple‐relay amplifying matrices, and destination‐equalizer joint optimization is investigated in distributed MIMO amplify‐and‐forward multiple‐relay networks with direct source–destination transmission in correlated fading channels. With the use of taking both the direct link and spatial correlation between antenna elements into account, the cooperative transceiver joint design is developed based on the minimum mean‐squared error criterion under individual power constraints at the source and multiple‐relay nodes. Simulation results demonstrate that the cooperative transceiver joint design architecture for an amplify‐and‐forward MIMO multiple‐relay system outperforms substantially the noncooperative transceiver design techniques on the BER performance under the spatial‐correlation channels.Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
996.
Photoinduced Proton Transfer between Photoacid and pH‐Sensitive Dyes: Influence Factors and Application for Visible‐Light‐Responsive Rewritable Paper 下载免费PDF全文
Ting Zhang Lan Sheng Junning Liu Le Ju Jianhua Li Zhen Du Weiran Zhang Minjie Li Sean Xiao‐An Zhang 《Advanced functional materials》2018,28(16)
Ink‐free printing based on rewritable paper is an efficient and environmental friendly way to reuse paper, protect resources, and save energy for sustainable development of human society. Among various kinds of rewritable media, light responsive rewritable paper (LRP) is one of the most popular research areas due to its clean and favorable noncontact writing. Visible light is more suitable for LRP for its superior penetration and much less damages to organic molecules than UV light. However, visible‐light‐responsive rewritable paper (VLRP) has only limited successes so far. Herein, a VLRP is newly designed and fabricated based on photoinduced proton transfer (PPT) between photoacid and pH‐sensitive dyes. Success of it is highly benefited from systematical investigation and in‐depth understanding on the key influence factors, such as concentration‐induced undesired isomerization, temperature, humidity, and light intensity, on the PPT and its inverse process. As‐prepared VLRP shows long‐awaited properties, such as, high color contrast and resolution, appropriate legible time of prints, excellent reversibility (>100 cycles), easiness to achieve multicolor prints, and agreeing well with environmental concept of green printing. In addition, study of influence factors on PPT in this work, to some extent, may also help people understand complex photocycle process in biosystem. 相似文献
997.
Functionalized Natural Particles: Light‐Induced Surface Modification of Natural Plant Microparticles: Toward Colloidal Science and Cellular Adhesion Applications (Adv. Funct. Mater. 18/2018) 下载免费PDF全文
998.
Antonio Sánchez‐Díaz Marta Izquierdo Salvatore Filippone Nazario Martin Emilio Palomares 《Advanced functional materials》2010,20(16):2695-2700
Organic solar cells made using a blend of DPM12 and P3HT are studied. The results show that higher Voc can be obtained when using DPM12 in comparison to the usual mono‐substituted PCBM electron acceptor. Moreover, better device performances are also registered when the cells are irradiated with sun‐simulated light of 10–50 mW cm?2 intensity. Electrochemical and time‐resolved spectroscopic measurements are compared for both devices and a 100‐mV shift in the density of states (DOS) is observed for DPM12/P3HT devices with respect to PCBM/P3HT solar cells and slow polaron‐recombination dynamics are found for the DPM12/P3HT devices. These observations can be directly correlated with the observed increase in Voc, which is in contrast with previous results that correlated the higher Voc with different ideality factors obtained using dark‐diode measurements. The origin for the shift in the DOS can be correlated to the crystallinity of the blend that is influenced by the properties of the included fullerene. 相似文献
999.
Functionalization of Graphene Oxide Films with Au and MoOx Nanoparticles as Efficient p‐Contact Electrodes for Inverted Planar Perovskite Solar Cells 下载免费PDF全文
Sumit S. Bhosale Efat Jokar Amir Fathi Cheng‐Min Tsai Chi‐Yung Wang Eric Wei‐Guang Diau 《Advanced functional materials》2018,28(37)
A graphene oxide (GO) film is functionalized with metal (Au) and metal‐oxide (MoOx) nanoparticles (NPs) as a hole‐extraction layer for high‐performance inverted planar‐heterojunction perovskite solar cells (PSCs). These NPs can increase the work function of GO, which is confirmed with X‐ray photoelectron spectra, Kelvin probe force microscopy, and ultraviolet photoelectron spectra measurements. The down‐shifts of work functions lead to a decreased level of potential energy and hence increased Voc of the PSC devices. Although the GO‐AuNP film shows rapid hole extraction and increased Voc, a Jsc improvement is not observed because of localization of the extracted holes inside the AuNP that leads to rapid charge recombination, which is confirmed with transient photoelectric measurements. The power conversion efficiency (PCE) of the GO‐AuNP device attains 14.6%, which is comparable with that of the GO‐based device (14.4%). In contrast, the rapid hole extraction from perovskite to the GO‐MoOx layer does not cause trapping of holes and delocalization of holes in the GO film accelerates rapid charge transfer to the indium tin oxide substrate; charge recombination in the perovskite/GO‐MoOx interface is hence significantly retarded. The GO‐MoOx device consequently shows significantly enhanced Voc and Jsc, for which its device performance attains PCE of 16.7% with great reproducibility and enduring stability. 相似文献
1000.