全文获取类型
收费全文 | 25158篇 |
免费 | 2068篇 |
国内免费 | 859篇 |
专业分类
电工技术 | 1334篇 |
技术理论 | 1篇 |
综合类 | 1381篇 |
化学工业 | 4520篇 |
金属工艺 | 1317篇 |
机械仪表 | 1328篇 |
建筑科学 | 1877篇 |
矿业工程 | 578篇 |
能源动力 | 885篇 |
轻工业 | 1643篇 |
水利工程 | 345篇 |
石油天然气 | 1347篇 |
武器工业 | 118篇 |
无线电 | 3120篇 |
一般工业技术 | 3258篇 |
冶金工业 | 1438篇 |
原子能技术 | 314篇 |
自动化技术 | 3281篇 |
出版年
2024年 | 86篇 |
2023年 | 413篇 |
2022年 | 705篇 |
2021年 | 1034篇 |
2020年 | 731篇 |
2019年 | 679篇 |
2018年 | 699篇 |
2017年 | 814篇 |
2016年 | 766篇 |
2015年 | 928篇 |
2014年 | 1245篇 |
2013年 | 1590篇 |
2012年 | 1583篇 |
2011年 | 1728篇 |
2010年 | 1403篇 |
2009年 | 1443篇 |
2008年 | 1342篇 |
2007年 | 1239篇 |
2006年 | 1349篇 |
2005年 | 1165篇 |
2004年 | 841篇 |
2003年 | 759篇 |
2002年 | 760篇 |
2001年 | 543篇 |
2000年 | 521篇 |
1999年 | 603篇 |
1998年 | 575篇 |
1997年 | 463篇 |
1996年 | 446篇 |
1995年 | 346篇 |
1994年 | 280篇 |
1993年 | 190篇 |
1992年 | 174篇 |
1991年 | 117篇 |
1990年 | 92篇 |
1989年 | 72篇 |
1988年 | 88篇 |
1987年 | 48篇 |
1986年 | 44篇 |
1985年 | 25篇 |
1984年 | 33篇 |
1983年 | 19篇 |
1982年 | 27篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 15篇 |
1977年 | 4篇 |
1976年 | 9篇 |
1975年 | 4篇 |
1965年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Jianhua Wen Tao Zeng Xiaotong Pan Zhijuan Zhong Siwen Yu Su Cheng 《International Journal of Applied Ceramic Technology》2022,19(6):3007-3016
3D-printed SiC ceramics were prepared by direct ink writing and solid-phase sintering. The effects of sintering temperature, solid loading, and carbon additive on microstructures and mechanical properties of 3D-printed SiC parts were investigated. It was found that the sintering temperature affected the evolution of the microstructure and mechanical properties of the sintered SiC parts. A high solid loading promoted the densification and mechanical properties of the sintered SiC parts. However, the solid loading exceeded 40 vol.%, which decreased the density and mechanical properties of the samples. The carbon additives could improve the densification of the SiC parts and enhance their mechanical properties. When the sucrose content increased from 0 to 8 wt.%, the open porosity of the SiC part decreased from 26.12% to 3.15%, whereas the flexural strength increased 2.19 times. Using the optimized components and process parameters, the high-performance 3D-printed SiC parts were achieved. 相似文献
992.
Xue Zhang Jin Du Guosheng Su Peirong Zhang Yujing Sun Chongyan Zhang Xiangmin Kong 《International Journal of Applied Ceramic Technology》2022,19(3):1354-1366
Mo2NiB2 is a kind of cermet with excellent mechanical properties, stable chemical properties, and excellent corrosion resistance and is often used in wear-resistant application fields, such as injection molding machine parts, can making tools and hot copper extruding dies. The brittleness of Mo2NiB2-based cermets limits their wide application. Mo2NiB2-based cermets were prepared by the vacuum sintering method, the effect of SiC whiskers (SiCw) on the microstructure and mechanical properties of cermets was investigated, and the toughening mechanism of SiCw on cermets was further discussed. The results indicate that with increasing SiCw content, the indentation fracture toughness (KIC), transverse fracture strength (TRS), and Vickers hardness (HV) of the cermets first increase and then decrease. The HV, TRS, and indentation fracture toughness of Mo2NiB2-based cermets with 0.5 wt% SiCw are 1 113 HV, 1 620 MPa, and 27.97 MPa·m1/2, respectively, which are 16.8%, 22.7%, and 25% higher than those without SiCw. In the sliding friction tests, Mo2NiB2-based cermets with 0.5 wt% SiCw have the smallest friction coefficient, low wear rate, and high wear resistance. SEM observation and analysis of the crack path and fracture surface showed that the toughening mechanism is whisker bridging, crack deflection, microcrack toughening, and whisker pull-out. The results indicate that the addition of 0.5 wt% SiCw can effectively improve the mechanical properties of Mo2NiB2-based cermets and further expand the application space of Mo2NiB2-based cermets. 相似文献
993.
Silicon - 2D global transient numerical model based on a new large-size ALD-G7 (G7) crystalline silicon ingot furnace is established and experimentally verified. A new pyramid-shaped bottom grille... 相似文献
994.
Silicon - 3D global simulations were performed to investigate the gas flow and impurities transport in casting silicon furnace under the influence of a unique designed spray-type gas guidance... 相似文献
995.
提出了在As-NaOH-ClO体系脱砷的方法,并以含砷镍烟灰为原料,系统研究了该体系下的脱砷效果。结果表明:在液固比L/S=10、NaClO浓度4.1%、NaOH浓度3%、反应温度50℃、反应时间1h的最优条件下,砷脱除率达到75%以上,镍损失率小于0.03%,可实现砷的无害化处理和金属镍的回收。 相似文献
996.
Siyi Ma Su Ruiming Wang Kaining Yang Yuping Qu Yingdong Li Rongde 《Russian Journal of Non-Ferrous Metals》2021,62(1):89-96
Russian Journal of Non-Ferrous Metals - The 7075 aluminum alloy was subjected to deep cryogenic treatment (DCT) at –196°C with liquid nitrogen for different hours. The wear and corrosion... 相似文献
997.
Yong Wang Shunming Li Chun Cheng Yuqing Su 《Journal of Mechanical Science and Technology》2018,32(7):2973-2985
We propose the quasi-zero-stiffness (QZS) vibration isolator as seat suspension to improve vehicle vibration isolation performance. The QZS vibration isolator is composed of vertical spring and two symmetric negative stiffness structures used as stiffness correctors. A vehicle-seat-human coupled model considering the QZS vibration isolator is established as a three degree-of-freedom (DOF) model; it is composed of a quarter car model and a simplified 1 DOF model combined vehicle seat and human body. This model considers the changing mass of the passengers and sets the total mass of the vehicle seat and human body as an uncertain parameter, which investigates the overload and unload conditions in practical engineering. To further improve the vehicle ride comfort, a constrained adaptive backstepping controller law based on the barrier Lyapunov function (BLF) is presented. The dynamic characteristic of the active vehicle-seathuman coupled model under shock excitation was analyzed using numerical method. The results show that the designed controller law can isolate the shock excitation transmitted from the road to the passengers effectively, and both the vehicle and seat suspension strokes remain in the allowed stroke range. 相似文献
998.
Toward multiple maximum power point estimation of photovoltaic systems based on semiconductor theory
Jen‐Cheng Wang Yu‐Li Su Kun‐Chang Kuo Jyh‐Cherng Shieh Joe‐Air Jiang 《Progress in Photovoltaics: Research and Applications》2015,23(7):847-861
Environmental conditions, such as temperature, non‐uniform irradiation, and solar shading, deeply affect the characteristics of photovoltaic (PV) modules in PV‐assisted generation systems. Several local maximum power points (MPPs) are found in the power–voltage curve of PV systems constructed by series/parallel‐connected PV modules under partially shaded conditions. The characteristics of PV systems change unpredictably when multiple MPPs occur, so the actual MPP tracking (MPPT) becomes a difficult task. Conventional MPPT methods for the PV systems under partially shaded conditions cannot quickly find the actual MPP such that the optimal utilization of PV systems cannot be achieved. Based on the p–n junction semiconductor theory, we develop a multipoint direct‐estimation (MPDE) method to directly estimate the multiple MPPs of the PV systems under partially shaded conditions and to cope with the mentioned difficulties. Using the proposed MPDE method, the multiple MPPs of the PV systems under partially shaded conditions can be directly determined from their irradiated current–voltage and power–voltage characteristic curves. The performances of the proposed MPDE method are evaluated by examining the characteristics of multiple MPPs of PV systems with respect to different shading strengths and numbers of the shaded PV modules and also tested using the field data. The experimental results demonstrate that the proposed MPDE method can simply and accurately estimate the multiple MPPs of the PV systems under partially shaded conditions. The optimization of MPP control models and the MPPT for PV systems could be achieved promisingly by applying the proposed method. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
999.
1000.