全文获取类型
收费全文 | 6505篇 |
免费 | 482篇 |
国内免费 | 114篇 |
专业分类
电工技术 | 257篇 |
综合类 | 203篇 |
化学工业 | 1117篇 |
金属工艺 | 209篇 |
机械仪表 | 244篇 |
建筑科学 | 388篇 |
矿业工程 | 54篇 |
能源动力 | 320篇 |
轻工业 | 505篇 |
水利工程 | 98篇 |
石油天然气 | 177篇 |
武器工业 | 4篇 |
无线电 | 814篇 |
一般工业技术 | 1026篇 |
冶金工业 | 454篇 |
原子能技术 | 23篇 |
自动化技术 | 1208篇 |
出版年
2024年 | 18篇 |
2023年 | 106篇 |
2022年 | 186篇 |
2021年 | 238篇 |
2020年 | 186篇 |
2019年 | 200篇 |
2018年 | 233篇 |
2017年 | 221篇 |
2016年 | 251篇 |
2015年 | 227篇 |
2014年 | 256篇 |
2013年 | 482篇 |
2012年 | 384篇 |
2011年 | 511篇 |
2010年 | 387篇 |
2009年 | 394篇 |
2008年 | 314篇 |
2007年 | 271篇 |
2006年 | 281篇 |
2005年 | 217篇 |
2004年 | 158篇 |
2003年 | 177篇 |
2002年 | 231篇 |
2001年 | 162篇 |
2000年 | 121篇 |
1999年 | 85篇 |
1998年 | 131篇 |
1997年 | 87篇 |
1996年 | 78篇 |
1995年 | 74篇 |
1994年 | 61篇 |
1993年 | 49篇 |
1992年 | 34篇 |
1991年 | 14篇 |
1990年 | 18篇 |
1989年 | 14篇 |
1988年 | 22篇 |
1987年 | 21篇 |
1986年 | 15篇 |
1985年 | 15篇 |
1984年 | 28篇 |
1983年 | 15篇 |
1982年 | 14篇 |
1981年 | 12篇 |
1980年 | 13篇 |
1979年 | 11篇 |
1978年 | 11篇 |
1977年 | 12篇 |
1976年 | 18篇 |
1975年 | 8篇 |
排序方式: 共有7101条查询结果,搜索用时 15 毫秒
891.
H. Ben youcef S. Alkan Gürsel A. Buisson L. Gubler A. Wokaun G. G. Scherer 《Fuel Cells》2010,10(3):401-410
The mechanical stability is, in addition to thermal and chemical stability, a primary requirement of polymer electrolyte membranes in fuel cells. In this study, the impact of grafting parameters and preparation steps on stress–strain properties of ETFE‐based proton conducting membranes, prepared by radiation‐induced grafting and subsequent sulphonation, was studied. No significant change in the mechanical properties of the ETFE base film was observed below an irradiation dose of 50 kGy. It was shown that the elongation at break decreases with increasing both the crosslinker concentration and graft level (GL). However, the tensile strength was positively affected by the crosslinker concentration. Yield strength and modulus of elasticity are almost unaffected by the introduction of crosslinker. Interestingly, yield strength and modulus of elasticity increase gradually with GL without noticeable change of the inherent crystallinity of grafted films. The most brittle membranes are obtained via the combination of high GL and crosslinker concentration. The optimised ETFE‐based membrane (GL of ∼25%, 5% DVB v/v), shows mechanical properties superior to those of Nafion® 112 membrane. The obtained results were correlated qualitatively to the other ex situ properties, including crystallinity, thermal properties and water uptake of the grafted membranes. 相似文献
892.
广东某地原规划的燃煤热电联产(燃煤CHP)机组能取得较好的经济效益,但大气污染物排放较高;原规划的天然气热电联产(天然气CHP)机组在相对于燃煤CHP机组较高的上网电价条件下,其经济效益可以与燃煤CHP机组竞争,但由于热电比较小,天然气CHP整体环境效益仍不理想。对此,建议采用天然气冷热电三联产(天然气CCHP)机组,虽然发电量相对较少,但能源利用效率提高,环境效益相对也较好。 相似文献
893.
Hydraulic systems play an important role in modern industry for the reason that hydraulic actuator systems have many advantages over other technologies with electric motors, as they possess high durability and the ability to produce large forces at high speeds. Therefore, the hydraulic actuator has a wide range of application fields such as hydraulic punching, riveting, pressing machines, and molding technology, where controlled forces or pressures with high accuracy and fast response are the most significant demands. Consequently, many hybrid actuator models have been developed for studying how to control forces or pressures with best results.This paper presents a kind of hydraulic load simulator for conducting performance and stability testing related to the force control problem of hydraulic hybrid systems. In the dynamic loading process, perturbation decreases control performance such as stability, frequency response, and loading sensitivity decreasing or bad. In order to improve the control quality of the loading system while eliminating or reducing the disturbance, a grey prediction model combined with a fuzzy PID controller is suggested. Furthermore, fuzzy controllers and a tuning algorithm are used to change the grey step size in order to improve the control quality. The grey prediction compensator can improve the system settle time and overshoot problems. Simulations and experiments on the hydraulic load simulator are carried out to evaluate the effectiveness of the proposed control method when applied to hydraulic systems with various external disturbances encountered in real working conditions. 相似文献
894.
Identification of pneumatic artificial muscle manipulators by a MGA-based nonlinear NARX fuzzy model
This study investigates the technique of modeling and identification of a new dynamic NARX fuzzy model by means of genetic algorithms. In conventional identification techniques, there are difficulties such as poor knowledge of the process, inaccurate process or complexity of the resulting mathematical model. All these factors deteriorate the identification performance when dealing with dynamic nonlinear industrial processes. To overcome these difficulties, this paper proposes a novel approach by using a modified genetic algorithm (MGA) combined with the predictive capability of nonlinear ARX (NARX) model for generating the dynamic NARX Takagi–Sugeno (TS) fuzzy model. The MGA algorithm processes the experimental input–output training data from the real system and optimizes the NARX fuzzy model parameters. This is referred to as fuzzy identification, which automatically generates the appropriate fuzzy if-then rules to characterize the dynamic nonlinear features of the real plant. The prototype pneumatic artificial muscle (PAM) manipulator, being a typical nonlinear and time-varying system, is used as a test system for this novel approach. This result shows that, with this MGA-based modeling and identification, the novel NARX fuzzy model identification approach to the PAM manipulator achieved highly outstanding performance and high precision as well. The accuracy of the proposed MGA-based NARX fuzzy model proves excellent in comparison with the MGA-based TS fuzzy model and the conventional GA-based TS fuzzy model. 相似文献
895.
896.
P. Dimitrakis A. Mouti C. Bonafos S. Schamm G. Ben Assayag V. Ioannou-Sougleridis B. Schmidt J. Becker P. Normand 《Microelectronic Engineering》2009,86(7-9):1838-1841
Structural and electrical properties of ALD-grown 5 and 7 nm-thick Al2O3 layers before and after implantation of Ge ions (1 keV, 0.5–1 × 1016 cm?2) and thermal annealing at temperatures in the 700–1050 °C range are reported. Transmission Electron Microscopy reveals the development of a 1 nm-thick SiO2-rich layer at the Al2O3/Si substrate interface as well as the formation of Ge nanocrystals with a mean diameter of ~5 nm inside the implanted Al2O3 layers after annealing at 800 °C for 20 min. Electrical measurements performed on metal–insulator–semiconductor capacitors using Ge-implanted and annealed Al2O3 layers reveal charge storage at low-electric fields mainly due to location of the Ge nanocrystals at a tunnelling distance from the substrate and their spatial dispersion inside the Al2O3 layers. 相似文献
897.
混凝土是建筑结构的重要材料,目前在建筑工程中普遍使用预拌混凝土浇筑.本文探讨了如何加强对预拌混凝土的质量控制与管理,以供同行参考. 相似文献
898.
中东现代艺术博物馆(MOMEMA)的规划正在进行之中。建设博物馆这一战略构想的初衷是使阿联酋成为多元文化相互理解的纽带。这座博物馆将成为一座里程碑,这座里程碑体现了迪拜湾在迪拜这座国际化城市中作为一个新的文化中心的重要性。这个新的文化中心被称为所谓的文化村,坐落于扎达夫历史街区内,占地37ha。除了中东现代艺术博物馆,这一地标性的工程还包括一个为现场表演和国际文化节准备的露天剧场、一个展览大厅和一个小博物馆,用来展示本地区和国际性的艺术品,以及一个为传统单桅帆船建造者提供的造船厂。此外,项目还将包括居住区、商业区和休闲区。 相似文献
899.
Jae Kwan Lee Yu-Man Wang Shinuk Cho Fred Wudl Alan J. Heeger 《Organic Electronics》2009,10(7):1223-1227
A new approach for high-efficiency polymer solar cells utilizing a BHJ active layer consisting of poly(3-hexylthiophene) (P3HT) as a donor and buckminsterfullerene, C60 as an acceptor was demonstrated. P3HT/C60 BHJ films were made possible by in situ formation of C60 from solubilized addends, C60–CpCO2R (R = Hex, Oct, and EHex) by retro Diels–Alder reaction at, or above, 100 °C. These cells exhibit enhanced performances compared to as-prepared P3HT/C60 BHJ films, showing better morphology. 相似文献
900.
C. Michael. Lindsay George C. Butler Chad G. Rumchik Ben Schulze Ryan Gustafson Warren R. Maines 《Propellants, Explosives, Pyrotechnics》2010,35(5):433-439
We report the development of a new methodology for analyzing CYLEX tests streak images. In these tests, the displacement of the wall of an explosive filled cylinder is obtained by backlighting the cylinder. The profile is imaged through a slit and streaked across a film record as the cylinder is detonated. A critical step in processing this data is the spatial calibration of the film and extraction of the profile of the cylinder from the image. Historically this has been a tedious task as it was performed by eye with the assistance of an optical comparator. Recently we developed an algorithm which automates the data calibration and extraction process of digitized streak records utilizing the Shen‐Castan edge detection algorithm and the image processing capabilities found in the IGOR PRO software. The new processing methodology greatly increases the resolution of the data, removes human subjectivity, and reduces analysis time from hours to seconds. The higher resolution of the new method has enabled much greater accuracy in measuring early‐time (<15 µs) expansion. With the aid of CTH hydrocode calculations, new fitting functions were developed to model both the early and late‐time expansion data. These functions contain physically meaningful fitting parameters and include terms which mimic the intensity and time scales of the shock and gas induced expansion of the cylinder independently. We demonstrate the methodology and hydrocode calculations on a recent CYLEX test series aimed at examining the effects of a plastic liner on high‐purity oxygen‐free copper cylinders filled with a high explosive. 相似文献