全文获取类型
收费全文 | 13866篇 |
免费 | 1511篇 |
国内免费 | 485篇 |
专业分类
电工技术 | 948篇 |
综合类 | 563篇 |
化学工业 | 2704篇 |
金属工艺 | 770篇 |
机械仪表 | 1049篇 |
建筑科学 | 1200篇 |
矿业工程 | 474篇 |
能源动力 | 477篇 |
轻工业 | 924篇 |
水利工程 | 250篇 |
石油天然气 | 749篇 |
武器工业 | 81篇 |
无线电 | 1438篇 |
一般工业技术 | 1734篇 |
冶金工业 | 530篇 |
原子能技术 | 94篇 |
自动化技术 | 1877篇 |
出版年
2024年 | 87篇 |
2023年 | 310篇 |
2022年 | 541篇 |
2021年 | 807篇 |
2020年 | 571篇 |
2019年 | 495篇 |
2018年 | 591篇 |
2017年 | 609篇 |
2016年 | 506篇 |
2015年 | 699篇 |
2014年 | 910篇 |
2013年 | 1037篇 |
2012年 | 1176篇 |
2011年 | 1210篇 |
2010年 | 1011篇 |
2009年 | 916篇 |
2008年 | 835篇 |
2007年 | 731篇 |
2006年 | 814篇 |
2005年 | 597篇 |
2004年 | 363篇 |
2003年 | 238篇 |
2002年 | 146篇 |
2001年 | 124篇 |
2000年 | 105篇 |
1999年 | 122篇 |
1998年 | 61篇 |
1997年 | 63篇 |
1996年 | 52篇 |
1995年 | 34篇 |
1994年 | 35篇 |
1993年 | 30篇 |
1992年 | 10篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1988年 | 3篇 |
1986年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1959年 | 3篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 855 毫秒
11.
Global decrease in crude oil resources and frequent crude oil leaks cause the energy crisis and ecological pollution. The absorption and release of leaked crude oil through absorption materials are a necessary process for environmental protection and recycling. In this article, a CO2-responsive olefin copolymer was obtained by copolymerization of styrene and an amine-containing olefin monomer. The structure of resultant copolymer was characterized by FTIR; thermal properties and CO2-responsive morphology changes were determined by DSC/TGA and SEM, respectively. Copolymers had certain absorption capacity for toluene with absorption rate up to 180.0%. The absorbed toluene could be released upon CO2 stimulation with desorption rate up to 84.6%. The CO2-responsive copolymer could be regenerated through a simple heating process and showed stable absorption–desorption performance even after being recycled for 4 times. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47439. 相似文献
12.
Information‐Centric Networking (ICN) has been accepted to overcome some weaknesses of the current Internet architecture, showing that “what is being exchanged” is more important than “who are exchanging information.” Given the inadequate considerations on Quality of Service (QoS) and energy saving in ICN routing, we propose in this paper a routing algorithm to enhance the two aspects. At first, on one hand, Cauchy distribution is used as a fuzzy model to evaluate users' QoS requirements, such as bandwidth, delay, and error rate; on the other hand, we formulate energy saving problem to evaluate the green quality of routing algorithm. Then, we design a link selection approach by considering QoS and energy saving, which belongs to a multi‐objective decision problem resolved by intelligent drops algorithm. Finally, we implement the proposed algorithm and compare it with the famous adaptive forwarding mechanism in terms of some significant metrics, and the experimental results reveal that the proposed algorithm is more efficient. 相似文献
13.
Zhuo Shi Ningning Dong Dingfeng Zhang Xiaofang Jiang Guanxin Du Shichao Lv Jiejie Chen Jun Wang Shifeng Zhou 《Journal of the American Ceramic Society》2019,102(7):3965-3971
The construction of nonlinear optical materials featuring asymmetric transmission of light is of great technological importance for various applications, including optical switching and optical power limiting. A significant challenge is the scalable fabrication of material candidates with good photochemical stability, high optical transmittance, and excellent optical limiting performance. Here, we present a nanocrystallization avenue for constructing hybrid optical limiting materials that exhibit ultrafast and robust optical limiting performance. The experimental results show that the controllable relaxation of a niobate glass may lead to the clustering of Nb-O units and contracting of the bandgap. It results in the notable improvement in nonlinear optical properties, including the enhanced saturation irradiance (380 GW/cm2), doubly increased nonlinear coefficient, and decreased limiting threshold (200 GW/cm2). Our results suggest a promising material that exhibits promising applications for protecting eyes and sensitive components from laser-induced damage. 相似文献
14.
15.
A facile and effective method was proposed to prepare the molecularly imprinted fluorescence sensor with carbon quantum dots, which were modified vinyl groups by acrylic acid on the surface. The obtained fluorescence composite material was investigated by transmission electron microscope and Fourier transform infrared spectra. After the experimental conditions were optimized, a linear range of 1.0–60 μmol L−1 was obtained and the detection limit was 0.17 μmol L−1. The novel fluorescence sensor can be successfully used to detect tetracycline in real samples. This study provides a convenient strategy for selective recognition and rapid detection of tetracycline in the complex environment. 相似文献
16.
17.
Porous polyimide (PI) films with low dielectric constants and excellent thermal properties have been a pressing demand for the next generation of high-performance, miniature, and ultrathin microelectronic devices. A series of novel porous PI films containing fluorenyl-adamantane groups were prepared successfully via thermolysis of poly(ethylene glycol) (PEG) added in the PI matrix. The cross-sectional morphologies of porous PI films showed closed pores with diameters ranging from 135 to 158 nm, which were uniform and regular in shape without interconnectivity. These porous PI films exhibited excellent thermal properties with a glass-transition temperature at 376 °C whereas the 5% weight loss temperature in air excess of 405 °C due to enhanced rigidity afforded by fluorenyl-adamantane groups. Accompanied by thermolysis content of PEG increasing from 0 to 20 wt %, the density of porous PI films decreased, and the corresponding porosity grew significantly from 0 to 11.48%. Depending on porosity, the dielectric constant and dielectric loss of porous PI films significantly declined from 2.89 to 2.37 and from 0.050 to 0.021, respectively. These excellent properties benefit the as-prepared porous PI films for application as interlayer dielectrics, integrated circuit chips, or multichip modules in microelectronic fields. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47313. 相似文献
18.
19.
PDC钻头布齿设计技术 总被引:2,自引:0,他引:2
刘建风 《勘探地球物理进展》2003,26(3):225-227
合理的布齿是保证PDC钻头具有优良工作性能的关键。目前常用的PDC钻头布齿设计方法是图解调整法,该方法速度慢,设计工作烦琐,工作量大,效率低,欠灵活,而且有时会出现不必要的误差。讨论了PDC钻头布齿设计的特点,按切削原则设计了钻头冠部形状,并选择了合理的切削结构,为PDC钻头布齿计算机辅助设计软件提供了理论支撑。 相似文献
20.