全文获取类型
收费全文 | 111166篇 |
免费 | 10044篇 |
国内免费 | 5857篇 |
专业分类
电工技术 | 6522篇 |
技术理论 | 9篇 |
综合类 | 8372篇 |
化学工业 | 18429篇 |
金属工艺 | 6612篇 |
机械仪表 | 6607篇 |
建筑科学 | 9072篇 |
矿业工程 | 3638篇 |
能源动力 | 3495篇 |
轻工业 | 7424篇 |
水利工程 | 2075篇 |
石油天然气 | 6996篇 |
武器工业 | 810篇 |
无线电 | 12254篇 |
一般工业技术 | 12720篇 |
冶金工业 | 5446篇 |
原子能技术 | 1403篇 |
自动化技术 | 15183篇 |
出版年
2024年 | 507篇 |
2023年 | 1913篇 |
2022年 | 3273篇 |
2021年 | 4569篇 |
2020年 | 3497篇 |
2019年 | 3222篇 |
2018年 | 3433篇 |
2017年 | 3806篇 |
2016年 | 3279篇 |
2015年 | 4429篇 |
2014年 | 5471篇 |
2013年 | 6325篇 |
2012年 | 6688篇 |
2011年 | 7167篇 |
2010年 | 6611篇 |
2009年 | 6030篇 |
2008年 | 5932篇 |
2007年 | 5717篇 |
2006年 | 5638篇 |
2005年 | 4776篇 |
2004年 | 3807篇 |
2003年 | 4417篇 |
2002年 | 5591篇 |
2001年 | 4678篇 |
2000年 | 3008篇 |
1999年 | 2800篇 |
1998年 | 1897篇 |
1997年 | 1639篇 |
1996年 | 1660篇 |
1995年 | 1299篇 |
1994年 | 996篇 |
1993年 | 717篇 |
1992年 | 578篇 |
1991年 | 400篇 |
1990年 | 317篇 |
1989年 | 247篇 |
1988年 | 220篇 |
1987年 | 122篇 |
1986年 | 104篇 |
1985年 | 68篇 |
1984年 | 61篇 |
1983年 | 41篇 |
1982年 | 34篇 |
1981年 | 23篇 |
1980年 | 35篇 |
1979年 | 10篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1959年 | 5篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
利用CAESARⅡ软件建立了某粉煤气化装置一级炉至二级炉设备及管道的整体模型,分析了管道应力及设备管口受力状况,并依此利用ANSYS软件对二级炉设备管口应力进行了详细分析.分析表明,管道支吊架调整后,管道及设备应力及应变符合规范要求. 相似文献
42.
Huizhu Cai Bingbing Chen Xiao Zhang Yuchen Deng Dequan Xiao Ding Ma Chuan Shi 《Nano Research》2021,14(1):122-130
Over recent years,catalytic materials of Fe-N-C species have been recognized being active for oxygen reduction reaction(ORR).However,the identification of active site remains challenging as it generally involves a pyrolysis process and mixed components being obtained.Herein Fe3C/C and Fe2N/C samples were synthesized by temperature programmed reduction of Fe precursors in 15%CH4/H2and pure NH3,respectively.By acid leaching of Fe2N/C sample,only single sites of FeN4species were presented,providing an ideal model for identification of catalytic functions of the single sites of FeN4in ORR.A correlation was conducted between the concentration of FeⅡN4in low spin state by Mossbauer spectra and the kinetic current density at 0.8 V in alkaline media,and such a structure-performance correlation assures the catalytic roles of low spin FeⅡN4 species as highly active sites for the ORR. 相似文献
43.
Yude Ji Yanping Guo Yuejuan Liu Yun Tian 《International Journal of Adaptive Control and Signal Processing》2020,34(3):283-297
This article focuses on the consensus problem of leader-following fractional-order multi-agent systems (MASs) with general linear and Lipschitz nonlinear dynamics. First, the distributed adaptive protocols for linear and nonlinear fractional-order MASs are constructed, respectively. We allow the control coupling gains to be time varying for each agent. Moreover, the adaptive modification schemes for the control gain are designed, which renders smaller control gains and thus requires smaller amplitude on the control input without sacrificing consensus convergence. Second, based on fractional-order Lyapunov stability theorem and Barbalat's lemma, two novel sufficient conditions in terms of linear matrix inequalities are provided to ensure that the leader-following consensus can be obtained in the case for any undirected connected communication graph. Furthermore, we show that the proposed algorithm also works for consensus of agents with intrinsic Lipschitz nonlinear dynamics. As a result, the proposed framework requires no global information and thus can be implemented in a fully distributed manner. Finally, the numerical simulations are given to demonstrate the effectiveness of obtained the theoretical results. 相似文献
44.
45.
46.
Weikang Dong Ruishi Qi Tiansheng Liu Yi Li Ning Li Ze Hua Zirui Gao Shuyuan Zhang Kaihui Liu Jiandong Guo Peng Gao 《Advanced materials (Deerfield Beach, Fla.)》2020,32(46):2002014
Hyperbolic phonon polaritons (HPhPs) in orthorhombic-phase molybdenum trioxide (α-MoO3) show in-plane hyperbolicity, great wavelength compression, and ultralong lifetime, therefore holding great potential in nanophotonic applications. However, its polaritonic response in the far-infrared (FIR) range remains unexplored due to challenges in experimental characterization. Here, monochromated electron energy loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM) is used to probe HPhPs in α-MoO3 in both mid-infrared (MIR) and FIR frequencies and correlate their behaviors with microstructures and orientations. It is found that low structural symmetry leads to various phonon modes and multiple Reststrahlen bands (RBs) over a broad spectral range (over 70 meV) and in different directions (55–63 meV and 119–125 meV along the b-axis, 68–106 meV along the c-axis, and 101–121 meV along the a-axis). These HPhPs can be selectively excited by controlling the direction of swift electrons. These findings provide new opportunities in nanophotonic and optoelectronic applications, such as directed light propagation, hyperlenses, and heat transfer. 相似文献
47.
Yong Xu Yun Li Songlin Li Francis Balestra Gerard Ghibaudo Wenwu Li Yen‐Fu Lin Huabin Sun Jing Wan Xinran Wang Yufeng Guo Yi Shi Yong‐Young Noh 《Advanced functional materials》2020,30(20)
Unreliable mobility values, and particularly greatly overestimated values and severely distorted temperature dependences, have recently hampered the development of the organic transistor field. Given that organic field‐effect transistors (OFETs) have been routinely used to evaluate mobility, precise parameter extraction using the electrical properties of OFETs is thus of primary importance. This review examines the origins of the various mobilities that must be determined for OFET applications, the relevant extraction methods, and the data selection limitations, which help in avoiding conceptual errors during mobility extraction. For increased precision, the review also discusses device fabrication considerations, calibration of both the specific gate‐dielectric capacitance and the threshold voltage, the contact effects, and the bias and temperature dependences, which must actually be handled with great care but have mostly been overlooked to date. This review serves as a systematic overview of the OFET mobility extraction process to ensure high precision and will also aid in improving future research. 相似文献
48.
49.
50.