全文获取类型
收费全文 | 2608篇 |
免费 | 154篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 31篇 |
综合类 | 11篇 |
化学工业 | 607篇 |
金属工艺 | 157篇 |
机械仪表 | 98篇 |
建筑科学 | 99篇 |
矿业工程 | 6篇 |
能源动力 | 119篇 |
轻工业 | 112篇 |
水利工程 | 28篇 |
石油天然气 | 14篇 |
无线电 | 230篇 |
一般工业技术 | 729篇 |
冶金工业 | 107篇 |
原子能技术 | 54篇 |
自动化技术 | 367篇 |
出版年
2024年 | 2篇 |
2023年 | 20篇 |
2022年 | 20篇 |
2021年 | 50篇 |
2020年 | 62篇 |
2019年 | 43篇 |
2018年 | 70篇 |
2017年 | 94篇 |
2016年 | 89篇 |
2015年 | 112篇 |
2014年 | 179篇 |
2013年 | 194篇 |
2012年 | 110篇 |
2011年 | 146篇 |
2010年 | 143篇 |
2009年 | 137篇 |
2008年 | 106篇 |
2007年 | 155篇 |
2006年 | 154篇 |
2005年 | 89篇 |
2004年 | 63篇 |
2003年 | 68篇 |
2002年 | 62篇 |
2001年 | 75篇 |
2000年 | 40篇 |
1999年 | 52篇 |
1998年 | 60篇 |
1997年 | 39篇 |
1996年 | 35篇 |
1995年 | 21篇 |
1994年 | 35篇 |
1993年 | 23篇 |
1992年 | 24篇 |
1991年 | 10篇 |
1990年 | 13篇 |
1989年 | 16篇 |
1988年 | 35篇 |
1987年 | 38篇 |
1986年 | 32篇 |
1985年 | 17篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1971年 | 2篇 |
排序方式: 共有2769条查询结果,搜索用时 125 毫秒
1.
《CIRP Annals》2021,70(2):471-493
Electronics is the vital basis for innovations and the essential enabler for global trends like connectivity, electro mobility and renewable energies. These applications require high performance and reliability of the electronic modules. Their assembly combines very heterogeneous process chains like remarkable productive and diminutive surface mount technology (SMT), powerful and robust power electronic interconnection techniques, as well as pioneering reel-to-reel based organic electronic printing. After briefly outlining the enormous global economic impact of electronic modules, this paper presents the state of the art of electronic module assembly including substrate materials, electronic components, packaging and assembly processes as well as quality and reliability testing methods. 相似文献
2.
Lili Hao Jiaxiang Li Peng Wang Zongliang Wang Zhenxu Wu Yu Wang Zixue Jiao Min Guo Tongfei Shi Qigang Wang Yoshihiro Ito Yen Wei Peibiao Zhang 《Advanced functional materials》2021,31(15):2009661
The degradation behavior of implants is significantly important for bone repair. However, it is still unprocurable to spatiotemporally regulate the degradation of the implants to match bone ingrowth. In this paper, a magneto-controlled biodegradation model is established to explore the degradation behavior of magnetic scaffolds in a magnetothermal microenvironment generated by an alternating magnetic field (AMF). The results demonstrate that the scaffolds can be heated by magnetic nanoparticles (NPs) under AMF, which dramatically accelerated scaffold degradation. Especially, magnetic NPs modified by oleic acid with a better interface compatibility exhibit a greater heating efficiency to further facilitate the degradation. Furthermore, the molecular dynamics simulations reveal that the enhanced motion correlation between magnetic NPs and polymer matrix can accelerate the energy transfer. As a proof-of-concept, the feasibility of magneto-controlled degradation for implants is demonstrated, and an optimizing strategy for better heating efficiency of nanomaterials is provided, which may have great instructive significance for clinical medicine. 相似文献
3.
Akira Yamamoto Kentaro Teramura Saburo Hosokawa Tsunehiro Tanaka 《Science and Technology of Advanced Materials》2015,16(2)
The effect of SO2 gas was investigated on the activity of the photo-assisted selective catalytic reduction of nitrogen monoxide (NO) with ammonia (NH3) over a TiO2 photocatalyst in the presence of excess oxygen (photo-SCR). The introduction of SO2 (300 ppm) greatly decreased the activity of the photo-SCR at 373 K. The increment of the reaction temperature enhanced the resistance to SO2 gas, and at 553 K the conversion of NO was stable for at least 300 min of the reaction. X-ray diffraction, FTIR spectroscopy, thermogravimetry and differential thermal analysis, x-ray photoelectron spectroscopy (XPS), elemental analysis and N2 adsorption measurement revealed that the ammonium sulfate species were generated after the reaction. There was a strong negative correlation between the deposition amount of the ammonium sulfate species and the specific surface area. Based on the above relationship, we concluded that the deposition of the ammonium sulfate species decreased the specific surface area by plugging the pore structure of the catalyst, and the decrease of the specific surface area resulted in the deactivation of the catalyst. 相似文献
4.
Polyacrylate gels containing Ag+ and TiO2 nanoparticles are shown to swell under UV light and shrink under visible light in water. In work reported by Tetsu Tatsuma and co‐workers on p. 1249, the TiO2 absorbs UV light and reduces the Ag+, whereas the deposited Ag absorbs visible light and dissolves itself. These redox reactions change the interactions between the polymer chains and eventually the volume of the gel, as shown on the cover. 相似文献
5.
Y. Tajitsu 《Journal of Materials Science》1996,31(8):2081-2089
A new experimental system has been developed, which enables measurements of linear as well as non-linear complex conductivities to be made. The frequency dependence of linear to fifth-order non-linear complex conductivities at different temperatures in a polyethylene oxide/salt complex can then be measured. A characteristic conduction relaxation phenomenon was observed in the spectra, which suggested the existence of different ion-conduction mechanisms between the high- and low-frequency regions. It was also found that the ratio of linear to non-linear conductivities was closely related to the elementary process of ionic transport. Furthermore, this ratio obtained from non-linear measurements allowed an estimate of the important parameters which characterized ionic transport in ion-conducting polymers, such as the hopping distance of an ion or the size of a connected cluster of the site capable of ion hopping, without the need for any additional assumptions. Thus, it was found that in a polyethylene oxide/salt complex, the typical size of a connected cluster of the effective sites capable of ion hopping was approximately 4 nm. 相似文献
6.
《International Journal of Pressure Vessels and Piping》2005,82(6):489-495
An updated and statistically-rigorous correlation is provided for crack-arrest toughness values versus normalized temperature for light-water nuclear reactor pressure vessel (RPV) steels. The database used in this effort is larger than applied heretofore and includes results from tests of laboratory-size specimens and from tests of large-scale specimens, which contain features prototypical of operating RPVs. The mathematical methodology used is based on a lognormal distribution, with its parameters calculated by orthogonal distance regression. This correlation was developed as one of several items updated for use in the US Nuclear Regulatory Commission's extensive program to evaluate and potentially revise its rule for ensuring structural integrity of operating RPVs when subjected to pressurized thermal-shock transients. 相似文献
7.
We show that an n-vertex bipartite K3,3-free graph with n?3 has at most 2n−4 edges and that an n-vertex bipartite K5-free graph with n?5 has at most 3n−9 edges. These bounds are also tight. We then use the bound on the number of edges in a K3,3-free graph to extend two known NC algorithms for planar graphs to K3,3-free graphs. 相似文献
8.
Koji Yamada Noboru Miura Chihiro Hamaguchi Norihiko Kamata 《Solid-state electronics》1989,32(12):1113-1117
Hot carrier magnetophonon resonances of n-type Si, short channel InP and p-type InSb were investigated in pulsed high magnetic fields up to 40 T. Using a recently developed high resolution technique in pulsed high fields, many new features of the hot carrier-phonon interactions in high magnetic fields were found. 相似文献
9.
Determination of three dimensional in situ stress from core discing based on analysis of principal tensile stress 总被引:2,自引:0,他引:2
K. Matsuki N. Kaga T. Yokoyama N. Tsuda 《International Journal of Rock Mechanics and Mining Sciences》2004,41(7):1167-1190
To determine all of the components of in situ stress from core discing, both the directions and magnitudes of the principal in situ stresses must be determined for a disc of a given thickness. In this study, we analyzed the direction and magnitude of tensile stress below an HQ core stub for 11 core lengths using stress conditions under which core discing is likely to occur. First, based on an analysis of the direction of tensile stress below the core stub, we propose a method for determining directions of in situ stress from the height distribution at the periphery of the end surface of a disc. This method can be used with a disc of any thickness. Next, based on an analysis of the magnitude of tensile stress in the central part of a core, we propose a linear criterion for core discing, which can be applied to a core of any length. This criterion was in good agreement with an empirical formula obtained previously in laboratory experiments. By combining information on the direction of in situ stress and the linear criterion for core discing, we propose a method for determining all of the components of in situ stress from core discing under the assumption that vertical stress is given by the overburden stress. Finally, these methods were applied to discs obtained from a field where hydraulic fracturing was performed to measure horizontal stresses. The results showed that the azimuths of the principal stresses estimated from core discing were consistent with those of the principal horizontal stresses determined by hydraulic fracturing and that while the magnitudes of the principal horizontal stresses estimated from core discing showed a large scatter, they were similar to those determined by hydraulic fracturing. 相似文献
10.
Mechanical properties of sinter-forged Al2O3-ZrO2 ceramics 总被引:1,自引:0,他引:1
Two kinds of composites, Al2O3-25 wt% ZrO2(2 mol% Y2O3) (Y-ZTA), Al2O3-25 wt% ZrO2(8 mol% CeO2) (Ce-ZTA) were produced by the sinter-forging process. The effect of presintering temperature on the mechanical properties of the composites was examined. The sinter-forging process increased the room-temperature bending strength in comparison with pressureless sintering, owing to the smaller grain size in sinter-forged bodies than in pressureless sintered ones. It was found necessary to keep the presintering temperature considerably lower than sinter-forging temperature in order to improve the room-temperature strength. The strength of sinter-forged Ce-ZTA was higher than that of sinter-forged Y-ZTA. The residual surface compressive stress induced by the phase transition during grinding in Ce-ZTA was found to be effective to further improve the strength and fracture toughness. 相似文献