全文获取类型
收费全文 | 1793篇 |
免费 | 281篇 |
国内免费 | 186篇 |
专业分类
电工技术 | 56篇 |
综合类 | 108篇 |
化学工业 | 160篇 |
金属工艺 | 30篇 |
机械仪表 | 172篇 |
建筑科学 | 9篇 |
矿业工程 | 4篇 |
能源动力 | 15篇 |
轻工业 | 26篇 |
水利工程 | 2篇 |
石油天然气 | 17篇 |
武器工业 | 2篇 |
无线电 | 920篇 |
一般工业技术 | 462篇 |
冶金工业 | 27篇 |
原子能技术 | 156篇 |
自动化技术 | 94篇 |
出版年
2024年 | 9篇 |
2023年 | 48篇 |
2022年 | 26篇 |
2021年 | 65篇 |
2020年 | 80篇 |
2019年 | 72篇 |
2018年 | 76篇 |
2017年 | 87篇 |
2016年 | 74篇 |
2015年 | 97篇 |
2014年 | 106篇 |
2013年 | 155篇 |
2012年 | 121篇 |
2011年 | 129篇 |
2010年 | 81篇 |
2009年 | 73篇 |
2008年 | 114篇 |
2007年 | 95篇 |
2006年 | 89篇 |
2005年 | 82篇 |
2004年 | 83篇 |
2003年 | 58篇 |
2002年 | 56篇 |
2001年 | 69篇 |
2000年 | 53篇 |
1999年 | 39篇 |
1998年 | 35篇 |
1997年 | 23篇 |
1996年 | 24篇 |
1995年 | 24篇 |
1994年 | 15篇 |
1993年 | 18篇 |
1992年 | 16篇 |
1991年 | 17篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 1篇 |
1985年 | 7篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1959年 | 2篇 |
1958年 | 1篇 |
排序方式: 共有2260条查询结果,搜索用时 15 毫秒
81.
为了有效处理上海光源前端挡光器接收的高热负载,研究了挡光器的结构设计及其优化方法。选用高导热性、高强度的GlidCop AL-15制造挡光器吸收体,采用直接水冷和掠入射结构提高其热缓释能力。以对流换热系数和压力降为评价指标,选用佩图克方程和达尔西-韦斯巴赫方程优化冷却水路,通过热分析得到了不同参数下挡光器的温度和热应力分析结果,从而确定了挡光器的结构设计优化参数。优化后挡光器的水路直径为6mm,水路到光照面的距离为9mm,光照面接线处圆角≥2mm,且水路与光束方向基本平行。与初始结构相比,优化后挡光器的最高整体温度和最高冷却壁温度分别下降约8%和1/4,最大等效应力降低了1/2左右,完全满足上海光源前端部件的设计要求。目前,应用优化参数设计的挡光器已应用于上海光源实际工程中。 相似文献
82.
Stimulated emission depletion (STED) microscopy is a useful tool in investigation for super‐resolution realm. By silencing the peripheral fluorophores of the excited spot, leaving only the very centre zone vigorous for fluorescence, the effective point spread function (PSF) could be immensely squeezed and subcellular structures, such as organelles, become discernable. Nevertheless, because of the low cross‐section of stimulated emission and the short fluorescence lifetime, the depletion power density has to be extremely higher than the excitation power density and molecules are exposed in high risk of photobleaching. The existence of photobleaching greatly limits the research of STED in achieving higher resolution and more delicate imaging quality, as well as long‐term and dynamic observation. Since the first experimental implementation of STED microscopy, researchers have lift out variety of methods and techniques to alleviate the problem. This paper would present some researches via conventional methods which have been explored and utilised relatively thoroughly, such as fast scanning, time‐gating, two‐photon excitation (TPE), triplet relaxation (T‐Rex) and background suppression. Alternatively, several up‐to‐date techniques, especially adaptive illumination, would also be unveiled for discussion in this paper. The contrast and discussion of these modalities would play an important role in ameliorating the research of STED microscopy. 相似文献
83.
Simon D. Hodgson William S. M. Brooks Andrew J. Clayton Giray Kartopu Daniel A. Lamb Vincent Barrioz Stuart J. C. Irvine 《Progress in Photovoltaics: Research and Applications》2015,23(2):150-159
Commercially available quantum dots have been encapsulated in a poly(methyl methacrylate) film and used as a luminescent downshifting layer on cadmium sulfide/cadmium telluride photovoltaic devices. Application of these films has resulted in a relative improvement to the short‐circuit current of over 4% by I–V measurement, with a significant increase in the contribution of short‐wavelength light resulting in 25% of the current available in this part of the spectrum being captured. The films have been shown to be highly scattering and the associated difficulties this provides to external quantum efficiency measurements have been discussed. A range of optical characterisation techniques, particularly laser beam induced current, have been used to probe the effect the films have on a cadmium sulfide/cadmium telluride device. An alternate methodology for performing external quantum efficiency measurements with the quantum dot films has been proposed. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
84.
《Food and Bioproducts Processing》2014,92(1):46-53
The performance of industrial cleaning in place (CIP) procedures is critically important for food manufacture. CIP has yet to be optimised for many processes, in part since the mechanisms involved in cleaning are not fully understood. Laboratory tests have an important role in guiding industrial trials, and this paper introduces and compares two experimental techniques developed for studying CIP mechanisms: local phosphorescence detection (LPD), and scanning fluid dynamic gauging (sFDG).To illustrate the comparison, each technique is used to investigate the influence of soil topology on the cleaning of pre-gelatinised starch-based layers from stainless steel (SS 316) substrates by aqueous NaOH solutions at ambient temperature. The roughness of the soil surface is varied by incorporating zinc sulphide particles with different particle size distributions (range 1–80 μm) into the starch suspensions. The soil roughness increased with the use of larger particles, increasing the 3D arithmetic mean roughness (Sa) of the dry layers (range 0.37–3.33 μm). Rough layers were cleaned more readily than those containing small inclusions, with a good correlation between the cleaning rates observed during LPD and FDG measurements. The LPD technique, which is an instrumented CIP test, gives a better indication of the cleaning time, while sFDG measurements provide further insight into the removal mechanisms. 相似文献
85.
86.
It is shown that for a front-to-back geometry of irradiation with photons and neutrons when monitoring doses in accordance
with the radiation safety standard NRB-99 or doses in critical organs using previous standards, the requirements imposed on
the energy dependence of the sensitivity of dosimeters have hardly changed since 1960. However, the requirements were quite
different for photons when monitoring the exposure dose using previous standards.
Translated from Izmeritel’naya Tekhnika, No. 2, pp. 49–55, February, 2009. 相似文献
87.
《Optical Materials》2014,36(12):2201-2207
New green host materials 1-(9,9-diphenyl-9H-fluorene-2-yl)-2-phenyl-1H-benzimidazole and 1-(9,9′-spirobifluorene-2-yl)-2-phenyl-1H-benzimidazole for solution-processed green phosphorescent organic light-emitting devices have been designed and synthesized by attaching the electron transporting benzimidazole units to the rigid fluorene units. Owing to the non-planar structures, which decrease the π conjugation length of fluorene and benzimidazole rings, these fluorene derived derivatives show high triplet energy. The high triplet energy of newly host materials ensures efficient energy transfer from the host to the triplet emitter tris(2-phenylpyridine)iridium. Furthermore, the thermal, photophysical, electrochemical properties and crystal structures of 1-(9,9-diphenyl-9H-fluorene-2-yl)-2-phenyl-1H-benzimidazole and 1-(9,9′-spirobifluorene-2-yl)-2-phenyl-1H-benzimidazole were investigated. The solution-processed single-layer green device using 1-(9,9-diphenyl-9H-fluorene-2-yl)-2-phenyl-1H-benzimidazole as the host for the phosphorescence emitter tris(2-phenylpyridine)iridium showed the maximum luminance efficiencies of 10.1 cd/A. This result demonstrated that the newly synthesized, fluorene-based rigid host materials are advantageous for fabrication of highly efficient green phosphorescent organic light-emitting diodes. 相似文献
88.
89.
Fang‐Ming Hsu Chen‐Han Chien Ching‐Fong Shu Chin‐Hung Lai Cheng‐Chih Hsieh Kang‐Wei Wang Pi‐Tai Chou 《Advanced functional materials》2009,19(17):2834-2843
Highly efficient blue electrophosphorescent organic light‐emitting diodes incorporating a bipolar host, 2,7‐bis(diphenylphosphoryl)‐9‐[4‐(N,N‐diphenylamino)phenyl]‐9‐phenylfluorene (POAPF), doped with a conventional blue triplet emitter, iridium(III) bis[(4,6‐difluoro‐phenyl)pyridinato‐N,C2´]picolinate (FIrpic) are fabricated. The molecular architecture of POAPF features an electron‐donating (p‐type) triphenylamine group and an electron‐accepting (n‐type) 2,7‐bis(diphenyl‐phosphoryl)fluorene segment linked through the sp3‐hybridized C9 position of the fluorene unit. The lack of conjugation between these p‐ and n‐type groups endows POAPF with a triplet energy gap (ET) of 2.75 eV, which is sufficiently high to confine the triplet excitons on the blue‐emitting guest. In addition, the built‐in bipolar functionality facilitates both electron and hole injection. As a result, a POAPF‐based device doped with 7 wt% FIrpic exhibits a very low turn‐on voltage (2.5 V) and high electroluminescence efficiencies (20.6% and 36.7 lm W?1). Even at the practical brightnesses of 100 and 1000 cd m?2, the efficiencies remain high (20.2%/33.8 lm W?1 and 18.8%/24.3 lm W?1, respectively), making POAPF a promising material for use in low‐power‐consumption devices for next‐generation flat‐panel displays and light sources. 相似文献
90.
The single-photon strong coupling in the deep-resolved sideband of the optomechanical system induces photon blockade (PB) effect. For the PB cavity, an initial mechanical coherent state evolves into superposition of phonon cat states entangled with the cavity Fock states. Measurement of the cavity photon number states produces phonon even and odd cat states. The information leakage effect of two photon states on the fidelity of cat states is calculated, it is shown that for low average phonon number this effect is negligible and decreases by increasing the two photon cavity state. The Lindblad equation is solved numerically to obtain the environmental effects on the fidelity of cat states. 相似文献