全文获取类型
收费全文 | 10322篇 |
免费 | 282篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 142篇 |
综合类 | 8篇 |
化学工业 | 2358篇 |
金属工艺 | 243篇 |
机械仪表 | 190篇 |
建筑科学 | 449篇 |
矿业工程 | 54篇 |
能源动力 | 302篇 |
轻工业 | 679篇 |
水利工程 | 105篇 |
石油天然气 | 106篇 |
无线电 | 652篇 |
一般工业技术 | 1776篇 |
冶金工业 | 1844篇 |
原子能技术 | 102篇 |
自动化技术 | 1608篇 |
出版年
2022年 | 109篇 |
2021年 | 150篇 |
2020年 | 121篇 |
2019年 | 115篇 |
2018年 | 160篇 |
2017年 | 159篇 |
2016年 | 201篇 |
2015年 | 173篇 |
2014年 | 255篇 |
2013年 | 716篇 |
2012年 | 390篇 |
2011年 | 495篇 |
2010年 | 367篇 |
2009年 | 402篇 |
2008年 | 448篇 |
2007年 | 395篇 |
2006年 | 389篇 |
2005年 | 329篇 |
2004年 | 302篇 |
2003年 | 256篇 |
2002年 | 258篇 |
2001年 | 179篇 |
2000年 | 171篇 |
1999年 | 168篇 |
1998年 | 230篇 |
1997年 | 191篇 |
1996年 | 175篇 |
1995年 | 145篇 |
1994年 | 154篇 |
1993年 | 143篇 |
1992年 | 130篇 |
1991年 | 111篇 |
1990年 | 111篇 |
1989年 | 144篇 |
1988年 | 101篇 |
1987年 | 119篇 |
1986年 | 122篇 |
1985年 | 135篇 |
1984年 | 158篇 |
1983年 | 116篇 |
1982年 | 117篇 |
1981年 | 95篇 |
1980年 | 90篇 |
1979年 | 99篇 |
1978年 | 82篇 |
1977年 | 102篇 |
1976年 | 98篇 |
1975年 | 87篇 |
1974年 | 92篇 |
1973年 | 75篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
A single-feed dual frequency compact microstrip antenna with a shorting pin is described. This new antenna configuration gives a large variation in frequency ratio of the two operating frequencies, without increasing the overall size of the antenna 相似文献
102.
Design and construction of a two-axis Sun tracking system for parabolic trough collector (PTC) efficiency improvement 总被引:1,自引:0,他引:1
An experimental study was performed to investigate the effect of using a continuous operation two-axes tracking on the solar energy collected. The collected energy was measured and compared with that on a fixed surface tilted at 40° towards the South. The results indicate that the measured collected solar energy on the moving surface was significantly larger (up to 46.46%) compared with the fixed surface. The proposed two-axis Sun tracking system was characterized by a fairly simple and low-cost electromechanical set-up with low maintenance requirements and ease on installation and operation. 相似文献
103.
英国波浪发电设备及其系泊系统的研究 总被引:4,自引:0,他引:4
为促进波浪发电设备的研究、更有效地利用可再生的波浪能源,介绍了处于该领域发展前沿的英国在波浪发电设备及其系泊系统方面的研究,重点阐述了几种主要波浪发电设备的原理和应用现况,归纳分析了其系泊系统的组成结构和近期相关发展,对波浪发电领域目前的研究重点进行了讨论,旨在为国内有关研究提供借鉴。 相似文献
104.
Starch-g-poly(methyl acrylate) (S-g-PMA), containing 40-65% PMA, was prepared with ceric ammonium nitrate (CAN) initiation in a 2-gallon reactor. CAN initiator was added either in one portion or portionwise. Graft copolymers were characterized with respect to % acetone-extractable polymer (largely PMA homopolymer), PMA content of the graft copolymer, and Mw of PMA grafts. Normal cornstarch as well as waxy and high amylose cornstarches were used in the grafting reaction. Conversions of monomer to polymer were nearly quantitative. Continuous plastic ribbons for tensile testing were prepared by extrusion processing. Tensile properties varied with the method used for CAN addition (i. e., single portion vs. portion-wise) and depended upon the particular starch variety used in the graft polymerization reaction. Since water acts as a plasticizer for starch, samples extruded at high moisture content exhibit higher % elongation (%E) values than the same polymers extruded at low moisture. Values for %E also increase with higher percentages of PMA in the graft copolymer. 相似文献
105.
A New Design Paradigm for Smart Windows: Photocurable Polymers for Quasi‐Solid Photoelectrochromic Devices with Excellent Long‐Term Stability under Real Outdoor Operating Conditions 下载免费PDF全文
Federico Bella George Leftheriotis Gianmarco Griffini George Syrrokostas Stefano Turri Michael Grätzel Claudio Gerbaldi 《Advanced functional materials》2016,26(7):1127-1137
A new photoelectrochromic device (PECD) is presented in this work proposing the combination of a WO3‐based electrochromic device (ECD) and a polymer‐based dye‐sensitized solar cell (DSSC). In the newly designed architecture, a photocurable polymeric membrane is employed as quasi‐solid electrolyte for both the ECD and the DSSC. In addition, a photocurable fluoropolymeric system is incorporated as solution‐processable external protective thin coating film with easy‐cleaning and UV‐shielding functionalities. Such new polymer‐based device assembly is characterized by excellent device operation with improved photocoloration efficiency and switching ability compared with analogous PECDs based on standard liquid electrolyte systems. In addition, long‐term (>2100 h) stability tests under continuous exposure to real outdoor conditions reveal the remarkable performance stability of this new quasi‐solid PECD system, attributed to the protective action of the photocurable fluorinated coating that effectively prevents photochemical and physical degradation of the PECD components during operation. This first example of quasi‐solid PECD systems paves the way for a new generation of thermally, electrochemically, and photochemically stable polymer‐based PECDs, and provides for the first time a clear demonstration of their true potential as readily upscalable smart window components for energy‐saving buildings. 相似文献
106.
Baolin Zhao Ziyang Gan Manuel Johnson Emad Najafidehaghani Tobias Rejek Antony George Rainer H. Fink Andrey Turchanin Marcus Halik 《Advanced functional materials》2021,31(42):2105444
Van der Waals (vdW) heterostructures composing of organic molecules with inorganic 2D crystals open the door to fabricate various promising hybrid devices. Here, a fully ordered organic self-assembled monolayer (SAM) to construct hybrid organic–inorganic vdW heterojunction phototransistors for highly sensitive light detection is used. The heterojunctions, formed by layering MoS2 monolayer crystals onto organic [12-(benzo[b]benzo[4,5]thieno[2,3-d]thiophen-2-yl)dodecyl)]phosphonic acid SAM, are characterized by Raman and photoluminescence spectroscopy as well as Kelvin probe force microscopy. Remarkably, this vdW heterojunction transistor exhibits a superior photoresponsivity of 475 A W−1 and enhanced external quantum efficiency of 1.45 × 105%, as well as an extremely low dark photocurrent in the pA range. This work demonstrates that hybridizing SAM with 2D materials can be a promising strategy for fabricating diversified optoelectronic devices with unique properties. 相似文献
107.
Boufenneche Yassine Zitouni Rafik George Laurent Gharbi Nawel 《Wireless Networks》2021,27(6):3927-3946
Wireless Networks - Performance and communication security in the Internet of Things (IoT) area draw a major concern for both academic and industrial communities. Indeed, an emerging number of IoT... 相似文献
108.
Cristina Ca?ero Nikolaos Thomos George A Triantafyllidis George C Litos Michael Gerassimos Strintzis 《IEEE transactions on information technology in biomedicine》2005,9(1):44-49
Ultrasound imaging allows the evaluation of the degree of emergency of a patient. However, in some instances, a well-trained sonographer is unavailable to perform such echography. To cope with this issue, the Mobile Tele-Echography Using an Ultralight Robot (OTELO) project aims to develop a fully integrated end-to-end mobile tele-echography system using an ultralight remote-controlled robot for population groups that are not served locally by medical experts. This paper focuses on the user interface of the OTELO system, consisting of the following parts: an ultrasound video transmission system providing real-time images of the scanned area, an audio/video conference to communicate with the paramedical assistant and with the patient, and a virtual-reality environment, providing visual and haptic feedback to the expert, while capturing the expert's hand movements. These movements are reproduced by the robot at the patient site while holding the ultrasound probe against the patient skin. In addition, the user interface includes an image processing facility for enhancing the received images and the possibility to include them into a database. 相似文献
109.
Image registration using log-polar mappings for recovery of large-scale similarity and projective transformations. 总被引:3,自引:0,他引:3
This paper describes a novel technique to recover large similarity transformations (rotation/scale/translation) and moderate perspective deformations among image pairs. We introduce a hybrid algorithm that features log-polar mappings and nonlinear least squares optimization. The use of log-polar techniques in the spatial domain is introduced as a preprocessing module to recover large scale changes (e.g., at least four-fold) and arbitrary rotations. Although log-polar techniques are used in the Fourier-Mellin transform to accommodate rotation and scale in the frequency domain, its use in registering images subjected to very large scale changes has not yet been exploited in the spatial domain. In this paper, we demonstrate the superior performance of the log-polar transform in featureless image registration in the spatial domain. We achieve subpixel accuracy through the use of nonlinear least squares optimization. The registration process yields the eight parameters of the perspective transformation that best aligns the two input images. Extensive testing was performed on uncalibrated real images and an array of 10,000 image pairs with known transformations derived from the Corel Stock Photo Library of royalty-free photographic images. 相似文献
110.
Chadwin D. Young Gennadi Bersuker Yuegang Zhao Jeff J. Peterson Joel Barnett George A. Brown Jang H. Sim Rino Choi Byoung Hun Lee Peter Zeitzoff 《Microelectronics Reliability》2005,45(5-6):806
Effects of constant voltage stress (CVS) on gate stacks consisting of an ALD HfO2 dielectric with various interfacial layers were studied with time dependent sensing measurements: DC I–V, pulse I–V, and charge pumping (CP) at different frequencies. The process of injected electron trapping/de-trapping on pre-existing defects in the bulk of the high-κ film was found to constitute the major contribution to the time dependence of the threshold voltage (Vt) shift during stress. The trap generation observed with the low frequency CP measurements is suggested to occur within the interfacial oxide layer or the interfacial layer/high-κ interface, with only a minor effect on Vt. 相似文献