全文获取类型
收费全文 | 15460篇 |
免费 | 1129篇 |
国内免费 | 384篇 |
专业分类
电工技术 | 282篇 |
综合类 | 644篇 |
化学工业 | 2881篇 |
金属工艺 | 575篇 |
机械仪表 | 711篇 |
建筑科学 | 457篇 |
矿业工程 | 224篇 |
能源动力 | 558篇 |
轻工业 | 4363篇 |
水利工程 | 48篇 |
石油天然气 | 337篇 |
武器工业 | 100篇 |
无线电 | 1165篇 |
一般工业技术 | 1802篇 |
冶金工业 | 410篇 |
原子能技术 | 329篇 |
自动化技术 | 2087篇 |
出版年
2024年 | 105篇 |
2023年 | 283篇 |
2022年 | 444篇 |
2021年 | 659篇 |
2020年 | 596篇 |
2019年 | 479篇 |
2018年 | 526篇 |
2017年 | 530篇 |
2016年 | 549篇 |
2015年 | 547篇 |
2014年 | 848篇 |
2013年 | 1113篇 |
2012年 | 981篇 |
2011年 | 1057篇 |
2010年 | 779篇 |
2009年 | 784篇 |
2008年 | 739篇 |
2007年 | 858篇 |
2006年 | 748篇 |
2005年 | 629篇 |
2004年 | 599篇 |
2003年 | 569篇 |
2002年 | 484篇 |
2001年 | 347篇 |
2000年 | 304篇 |
1999年 | 232篇 |
1998年 | 190篇 |
1997年 | 169篇 |
1996年 | 133篇 |
1995年 | 116篇 |
1994年 | 102篇 |
1993年 | 71篇 |
1992年 | 80篇 |
1991年 | 40篇 |
1990年 | 44篇 |
1989年 | 32篇 |
1988年 | 31篇 |
1987年 | 35篇 |
1986年 | 28篇 |
1985年 | 35篇 |
1984年 | 29篇 |
1983年 | 11篇 |
1982年 | 19篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1970年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(64):27608-27616
The vanadium hydrides have better hydrogen storage capacity in comparison to the other metal hydrides. Although the structure of VH2 hydride has been reported, the structural stability, electronic and optical properties of VH2 hydride are unclear. To solve these problems, we apply the first-principles method to study the structural stability, electronic and optical properties of VH2 hydrides. Similar to the metal dihydrides, four possible VH2 hydrides such as the cubic (Fm-3m), tetragonal (I4/mmm), tetragonal (P42/mnm) and orthorhombic (Pnma) are designed. The result shows that the cubic VH2 hydride is a thermodynamic and dynamical stability. In particular, the tetragonal (I4/mmm) and the orthorhombic (Pnma) VH2 hydrides are firstly predicted. It is found that these VH2 hydrides show metallic behavior. The electronic interaction of V (d-state)-H (s-state) is beneficial to improve the hydrogen storage in VH2 hydride. In addition, the formation of V–H bond can improve the structural stability of VH2 hydride. Based on the analysis of optical properties, it is found that all VH2 hydrides show the ultraviolet response. Compared to the tetragonal and orthorhombic VH2 hydrides, the cubic VH2 hydride has better storage optical properties. Therefore, we believe that the VH2 hydride is a promising hydrogen storage material. 相似文献
2.
Ligang Yu Yong Li Yukun Yang Caixia Guo Meiping Li 《International Journal of Food Science & Technology》2022,57(7):4646-4655
This study investigated the inhibitory effects of curcumin and piperine on fluorescent advanced glycation end products (fAGEs) formation in a bovine serum albumin (BSA)–fructose model. Model systems of BSA and fructose were prepared, and curcumin or piperine was added. fAGEs and BSA oxidation product (dityrosine, kynurenine and N'-formylkynurenine) contents were determined. The results showed that fAGEs content decreased with increasing concentration of curcumin and piperine (P < 0.05). Addition of curcumin and piperine at 160 µg mL−1 could inhibit fluorescent AGEs by 100% and 93% respectively. Dityrosine and N'-formylkynurenine contents decreased as curcumin and piperine concentration increased (P < 0.05). Furthermore, the result of principal component analysis indicated that curcumin and piperine markedly impeded BSA oxidation, resulting in a lower level of fAGEs in model systems. Therefore, adding curcumin and piperine may facilitate reduced fAGEs levels in BSA–fructose model. 相似文献
3.
《International Journal of Hydrogen Energy》2022,47(1):276-291
To the best of our knowledge, this is the first time to report the preparation of a dotted nanowire arrayed by 5 nm sized palladium and nickel composite nanoparticles (denoted as PdxNiy NPs) via a hydrothermal method using NU and PdO·H2O as the starting materials. The samples prepared at the mass ratio of NU to PdO·H2O 1:1, 1:2 and 2:1 were, respectively, nominated as catalyst c1, c2 and c3. The chemical compositions of all synthesized catalysts were mainly studied by using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), revealing that metallic Ni was one main component of all prepared catalysts. Surprisingly, the main diffraction peaks appearing in the XRD patterns of all prepared catalysts were assigned to the metallic Ni rather than the metallic Pd. Very interestingly, as indicated by the TEM images, a large number of dotted nanowires arrayed by numerous equidistant 5 nm sized nanoparticles were distinctly exhibited in catalyst c1. More importantly, when being used as electrocatalysts for EOR, all prepared catalysts exhibited an evident electrocatalytic activity towards EOR. In the cyclic voltammetry (CV) test, the peak current density of the forward peak of EOR on catalyst c1 measured at 50 mV s?1 was as high as 56.1 mA cm?2, being almost 9 times higher than that of EOR on catalyst c3 (6.3 mA cm?2). Particularly, the polarized current density of EOR on catalyst c1 at 3600 s, as indicated by the chronoamperometry (CA) experiment, was still maintained to be around 1.47 mA cm?2, a value higher than the latest reported data of 1.3 mA cm?2 (measured on the pure Pd/C electrode). Presenting a novel method to prepare dotted nanowires arranged by 5 nm sized nanoparticles and showing the significant eletrocatalytic activities of the newly prepared dotted nanowires towards EOR were the major contributions of this preliminary work. 相似文献
4.
5.
《Ceramics International》2021,47(22):31886-31893
In this contribution, SnFe2O4 nanoparticles were prepared by the solvothermal method, the structural properties were performed using X-Ray Diffraction (DRX) to prove the success of tin ferrite formation and to determine de crystals parameters. The size and morphological study were build using Scanning Electron Microscopy (SEM) and Transmission Electron microscopy (TEM), the results showed that the size of particles is uniform with a range of particles (5–7 nm). The magnetic properties were carried out using the SQUID device, the SnFe2O4 nanoparticles have a magnetic transition at 750 K. In addition, the hysteresis loops at low temperature displayed Ms and Mr equals to 23 emu/g and 6 emu/g, respectively. The magnetoresistance properties were investigated, the SnFe2O4 nanoparticles present a large magnetoresistance effect (80%). The experimental results are supplemented by model calculations utilizing density functional theory and Monte-Carlo simulations. 相似文献
6.
7.
《Contact lens & anterior eye》2020,43(3):277-284
Addiction to cigarette smoking has high prevalence rates recorded worldwide. Smoking has been linked to several life-threatening systemic conditions such as cancer, heart attack and stroke, in addition to a range of ocular pathologies. In recent years, electronic cigarettes (EC) have emerged as alternatives to smoking. ECs are nicotine delivery devices which produce an aerosol by heating, rather than combusting, a liquid which contains nicotine, flavours and preservatives. This review focuses on the association of traditional and new forms of smoking with dry eye disease, contact lens wear and four other common ocular diseases: cataract, age-related macular degeneration, glaucoma and Graves’ ophthalmopathy. It is concluded that smoking and vaping appear as a risk factor for the aforementioned ocular conditions. An evidence-based, clear link between cigarette smoking, or EC vaping and ocular problems is yet to be discovered. 相似文献
8.
Front-of-package labels (FOPL) are recommended to reduce consumer intake of ultra-processed food products (UPP). The multiple traffic-light label is one example of FOPL that indicates the content of target nutrients in products by displaying red (high), amber (medium), and/or green (low) color-coding. The red code may implicitly enhance sweetness perception and approach dispositions toward sweet UPP via cross-modal visual-taste interactions. We conducted two experiments to examine the possibility of contradictory influence of explicitly learned and implicit cross-modal associations on the emotional responses evoked by UPP pictures. In both experiments, we first explicitly associated the color codes with health-related meanings. In Experiment I (n = 78), a psychometric tool estimated the emotional responses (pleasantness and arousal ratings) evoked by UPP pictures when preceded by red, amber, or green color-codes. In Experiment II (n = 24), we recorded participants’ electrocortical brain activity to assess the early posterior negativity (EPN) component as an index of the emotional responses to UPP. The reported pleasantness (Experiment I) and the EPN amplitude (Experiment II) were greater for sweet UPP relative to salty UPP when primed with red codes but not when primed with green or amber. A red code increased positive emotions toward sweet UPP despite its explicit association with increased health-risks. Thus, the use of multiple traffic-lights might lead to an unintended implicit approach behavior toward sweet UPP. Designers, researchers, and policy makers may consider color-taste cross-modal associations when designing, testing, and applying FOPL. 相似文献
9.
10.
Energy bands, effective mass of carriers, absolute band edge positions and optical properties of tetragonal AgInS2 were calculated using a first-principles approach with the exchange correlation described by B3LYP hybrid functional. The results indicate that tetragonal AgInS2 has a direct band gap of 1.93 eV, which reproduce well experimental value. Calculated effective masses of electrons and holes are both small which are beneficial to separation and migration of electron and hole pairs. This implies that AgInS2 has good photocatalytic performance. The calculated optical characteristics indicate that AgInS2 has a slight anisotropy for both the real and imaginary parts of the dielectric function and exhibits large optical absorption in the visible light region. Furthermore, the calculated band edge positions in (100), (010) and (001) surfaces indicate that tetragonal AgInS2 is beneficial to the reduction and oxidation of water to hydrogen and oxygen under visible light irradiation. 相似文献