全文获取类型
收费全文 | 200362篇 |
免费 | 4269篇 |
国内免费 | 730篇 |
专业分类
电工技术 | 3439篇 |
综合类 | 111篇 |
化学工业 | 33120篇 |
金属工艺 | 8151篇 |
机械仪表 | 5636篇 |
建筑科学 | 5165篇 |
矿业工程 | 921篇 |
能源动力 | 5228篇 |
轻工业 | 21527篇 |
水利工程 | 1977篇 |
石油天然气 | 3238篇 |
武器工业 | 3篇 |
无线电 | 20815篇 |
一般工业技术 | 37083篇 |
冶金工业 | 37441篇 |
原子能技术 | 4357篇 |
自动化技术 | 17149篇 |
出版年
2021年 | 2006篇 |
2020年 | 1540篇 |
2019年 | 1889篇 |
2018年 | 3202篇 |
2017年 | 3165篇 |
2016年 | 3312篇 |
2015年 | 2453篇 |
2014年 | 3751篇 |
2013年 | 9848篇 |
2012年 | 6168篇 |
2011年 | 7821篇 |
2010年 | 6204篇 |
2009年 | 6890篇 |
2008年 | 6924篇 |
2007年 | 6795篇 |
2006年 | 5654篇 |
2005年 | 5212篇 |
2004年 | 4979篇 |
2003年 | 4616篇 |
2002年 | 4517篇 |
2001年 | 4421篇 |
2000年 | 4162篇 |
1999年 | 4334篇 |
1998年 | 11891篇 |
1997年 | 8353篇 |
1996年 | 6260篇 |
1995年 | 4593篇 |
1994年 | 3873篇 |
1993年 | 3821篇 |
1992年 | 2675篇 |
1991年 | 2600篇 |
1990年 | 2467篇 |
1989年 | 2488篇 |
1988年 | 2448篇 |
1987年 | 2193篇 |
1986年 | 2123篇 |
1985年 | 2432篇 |
1984年 | 2233篇 |
1983年 | 2039篇 |
1982年 | 1913篇 |
1981年 | 1992篇 |
1980年 | 1844篇 |
1979年 | 1841篇 |
1978年 | 1804篇 |
1977年 | 2197篇 |
1976年 | 2865篇 |
1975年 | 1586篇 |
1974年 | 1574篇 |
1973年 | 1643篇 |
1972年 | 1352篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
F.T. Munna Vidhya Selvanathan K. Sobayel Ghulam Muhammad Nilofar Asim Nowshad Amin Kamaruzzaman Sopian Md. Akhtaruzzaman 《Ceramics International》2021,47(8):11003-11009
In this study, dilute chemical bath deposition technique has been used to deposit CdZnS thin films on soda-lime glass substrates. The structural, morphological, optoelectronic properties of as-grown films have been investigated as a function of different Zn2+ precursor concentrations. The X-ray diffractogram of CdS thin-film reveals a peak corresponding to (002) plane with wurtzite structure, and the peak shift has been observed with the increase of the Zn2+ concentration upon formation of CdZnS thin film. From morphological studies, it has been revealed that the diluted chemical bath deposition technique provides homogeneous distribution of film on the substrate even at a lower concentration of Zn2+. Optical characterization has shown that the transparency of the film is influenced by Zn2+ concentration and when the Zn2+ concentration is varied from 0 M to 0.0256 M, bandgap values of resulting films range from 2.42 eV to 3.90 eV while. Furthermore, electrical properties have shown that with increasing zinc concentration the resistivity of the film increases. Finally, numerical simulation validates and suggests that CdZnS buffer layer with composition of 0.0032 M Zn2+ concentration would be a promising candidate in CIGS solar cell. 相似文献
3.
Journal of Chemical Ecology - Biocontrol agents such as parasitic wasps use long-range volatiles and host-associated cues from lower trophic levels to find their hosts. However, this chemical... 相似文献
4.
Kravchenko V. F. Konovalov Ya. Yu. 《Journal of Communications Technology and Electronics》2022,67(8):952-964
Journal of Communications Technology and Electronics - A new design of wavelets based on the convolution of a compactly supported function with a rectangular pulse is proposed and theoretically... 相似文献
5.
Journal of Communications Technology and Electronics - A statistical study of the effectiveness of the non-threshold search procedure for a noise-like phase-shift keyed signal by the delay time is... 相似文献
6.
Golam Haider Krishna Sampathkumar Tim Verhagen Lukáš Nádvorník Farjana J. Sonia Václav Valeš Jan Sýkora Peter Kapusta Petr Němec Martin Hof Otakar Frank Yang-Fang Chen Jana Vejpravová Martin Kalbáč 《Advanced functional materials》2021,31(29):2102196
Recent advancements in isolation and stacking of layered van der Waals materials have created an unprecedented paradigm for demonstrating varieties of 2D quantum materials. Rationally designed van der Waals heterostructures composed of monolayer transition-metal dichalcogenides (TMDs) and few-layer hBN show several unique optoelectronic features driven by correlations. However, entangled superradiant excitonic species in such systems have not been observed before. In this report, it is demonstrated that strong suppression of phonon population at low temperature results in a formation of a coherent excitonic-dipoles ensemble in the heterostructure, and the collective oscillation of those dipoles stimulates a robust phase synchronized ultra-narrow band superradiant emission even at extremely low pumping intensity. Such emitters are in high demand for a multitude of applications, including fundamental research on many-body correlations and other state-of-the-art technologies. This timely demonstration paves the way for further exploration of ultralow-threshold quantum-emitting devices with unmatched design freedom and spectral tunability. 相似文献
7.
8.
Claudia Paredes Francisco J. Martínez-Vázquez Hamada Elsayed Paolo Colombo Antonia Pajares Pedro Miranda 《Journal of the European Ceramic Society》2021,41(1):892-900
Bioactive ceramic scaffolds for bone regeneration consisting of a three-dimensional mesh of interpenetrating struts with square section were fabricated via Digital Light Processing (DLP). The ability of the technique to manufacture 3D porous structures from β-tricalcium phosphate (β-TCP) powders with different dimensions of struts and pores was evaluated, identifying the possibilities and limitations of the manufacturing process. Small pore sizes were found to seriously complicate the elimination of excess slurry from the scaffold’s innermost pores. The effect of the strut/pore size on the mechanical performance of the scaffolds under compressive stresses was also evaluated, but no significant influence was found. Under compressive stresses, the structures resulted weaker when tested perpendicularly to the printing plane due to interlayer shear failure. Interlayer superficial grooves are proposed as potential failure-controlling defects, which could also explain the lack of a Weibull size effect on the mechanical strength of the fabricated DLP scaffolds. 相似文献
9.
Reliable joints of Ti3SiC2 ceramic and TC11 alloy were diffusion bonded with a 50 μm thick Cu interlayer. The typical interfacial structure of the diffusion boned joint, which was dependent on the interdiffusion and chemical reactions between Al, Si and Ti atoms from the base materials and Cu interlayer, was TC11/α-Ti + β-Ti + Ti2Cu + TiCu/Ti5Si4 + TiSiCu/Cu(s, s)/Ti3SiC2. The influence of bonding temperature and time on the interfacial structure and mechanical properties of Ti3SiC2/Cu/TC11 joint was analyzed. With the increase of bonding temperature and time, the joint shear strength was gradually increased due to enhanced atomic diffusion. However, the thickness of Ti5Si4 and TiSiCu layers with high microhardness increased for a long holding time, resulting in the reduction of bonding strength. The maximum shear strength of 251 ± 6 MPa was obtained for the joint diffusion bonded at 850 °C for 60 min, and fracture primarily occurred at the diffusion layer adjacent to the Ti3SiC2 substrate. This work provided an economical and convenient solution for broadening the engineering application of Ti3SiC2 ceramic. 相似文献
10.
Patricia Seoane-Collazo Amparo Romero-Pic Eva Rial-Pensado Laura Liares-Pose nxela Estvez-Salguero Johan Fern Rubn Nogueiras Carlos Diguez Miguel Lpez 《International journal of molecular sciences》2021,22(4)
Several studies have reported that nicotine, the main bioactive component of tobacco, exerts a marked negative energy balance. Apart from its anorectic action, nicotine also modulates energy expenditure, by regulating brown adipose tissue (BAT) thermogenesis and white adipose tissue (WAT) browning. These effects are mainly controlled at the central level by modulation of hypothalamic neuropeptide systems and energy sensors, such as AMP-activated protein kinase (AMPK). In this study, we aimed to investigate the kappa opioid receptor (κOR)/dynorphin signaling in the modulation of nicotine’s effects on energy balance. We found that body weight loss after nicotine treatment is associated with a down-regulation of the κOR endogenous ligand dynorphin precursor and with a marked reduction in κOR signaling and the p70 S6 kinase/ribosomal protein S6 (S6K/rpS6) pathway in the lateral hypothalamic area (LHA). The inhibition of these pathways by nicotine was completely blunted in κOR deficient mice, after central pharmacological blockade of κOR, and in rodents where κOR was genetically knocked down specifically in the LHA. Moreover, κOR-mediated nicotine effects on body weight do not depend on orexin. These data unravel a new central regulatory pathway modulating nicotine’s effects on energy balance. 相似文献