全文获取类型
收费全文 | 1228篇 |
免费 | 124篇 |
国内免费 | 120篇 |
专业分类
电工技术 | 40篇 |
综合类 | 129篇 |
化学工业 | 213篇 |
金属工艺 | 52篇 |
机械仪表 | 111篇 |
建筑科学 | 73篇 |
矿业工程 | 17篇 |
能源动力 | 91篇 |
轻工业 | 21篇 |
水利工程 | 21篇 |
石油天然气 | 27篇 |
武器工业 | 25篇 |
无线电 | 152篇 |
一般工业技术 | 255篇 |
冶金工业 | 17篇 |
原子能技术 | 30篇 |
自动化技术 | 198篇 |
出版年
2024年 | 1篇 |
2023年 | 16篇 |
2022年 | 20篇 |
2021年 | 29篇 |
2020年 | 33篇 |
2019年 | 36篇 |
2018年 | 40篇 |
2017年 | 41篇 |
2016年 | 41篇 |
2015年 | 44篇 |
2014年 | 76篇 |
2013年 | 91篇 |
2012年 | 105篇 |
2011年 | 117篇 |
2010年 | 82篇 |
2009年 | 78篇 |
2008年 | 85篇 |
2007年 | 76篇 |
2006年 | 68篇 |
2005年 | 50篇 |
2004年 | 37篇 |
2003年 | 57篇 |
2002年 | 44篇 |
2001年 | 28篇 |
2000年 | 29篇 |
1999年 | 25篇 |
1998年 | 23篇 |
1997年 | 22篇 |
1996年 | 13篇 |
1995年 | 15篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 9篇 |
1991年 | 1篇 |
1990年 | 6篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有1472条查询结果,搜索用时 15 毫秒
1.
LAWRENCE R. GRIFFING 《Journal of microscopy》2020,278(3):114-122
2.
Susan Laxton 《History of Photography》2019,43(2):191-205
In its first instance as art practice among the historical avant-garde, photomontage was considered indispensable for its claim to intervene in perceptual processes, stimulating a critical mode of apprehension that would redirect the viewer away from conventions of aesthetic experience and towards a lived reception of art with pronounced relevance to the sociopolitical landscape. The effect was understood as structural, that is, activated not so much by direct political content, but by the stark and shocking effects of juxtaposition. By this measure, one challenge to contemporary photomontage is clear: in a postindustrial and postdigital visual landscape dominated by the structural fragmentation of the attention economy, the ‘simultaneity of the radically disparate’ (as Peter Bürger put it) might no longer present as heterodoxy but rather threaten to sink into invisibility. Yet with the migration off-screen of the effects of electronic media, a new urgency around moving photomontage structures into physical, public space is rising in contemporary practices. Shannon Ebner’s multi-part project A Hudson Yard (2014–15) is emblematic of the new ways in which artists are manipulating photomontage as a form of fully sensory experience that gives the medium room to play critically in both virtual and material space. By constructing subtle interruptions of naturalised commercial space, A Hudson Yard activates a détournement of instrumentalised language, using structures of juxtaposition to divert the discursive surfaces of public space away from consumption and towards what could be called a public poesis. 相似文献
3.
Zhi Zhou Jing-Pei Cao Yan Wu Qi-Qi Zhuang Xiao-Yan Zhao Yu-Lei Wei Hong-Cun Bai 《International Journal of Hydrogen Energy》2021,46(44):22735-22746
Waste sugar solution (WSS), a waste by-product of manufacturing vitamin C, contains abundant waste acids and organics. In this work, a N/O-enriched copolymer was synthesized via a facile polymerization via the hydrogen bonding of O-containing functional groups and melamine and the crosslinking of aldehyde groups. Subsequently, N-doped carbon spheres were prepared by a typical carbonation/activation method. Remarkably, benefiting from an ultrahigh specific surface area (3612 m2/g) and rich heteroatom content (4.3% for N, 8.8% for O), the carbon spheres deliver a high specific capacitance of 387 F/g at 50 mA/g and 283 F/g at 5 A/g with 6 M KOH in two-electrode system. The assembled symmetric electric double-layer capacitor exhibits high energy density of 10.83 Wh/kg at 11.10 W/kg. This research provides a facile method for preparing N/O-doped carbon spheres by WSS, and confirms the excellent electrochemical performance of WSS-derived carbons in energy storage applications. 相似文献
4.
This study proposes a method of constructing type II generalized angulated elements (GAEs II) Hoberman sphere mechanisms on the basis of deployment axes that intersect at one point. First, the constraint conditions for inserting n GAEs II into n deployment axes to form a loop are given. The angle constraint conditions of the deployment axes are obtained through a series of linear equations. Second, the connection conditions of two GAEs II loops that share a common deployable center are discussed. Third, a flowchart of constructing the generalized Hoberman sphere mechanism on the basis of deployment axes is provided. Finally, four generalized Hoberman sphere mechanisms based on a fully enclosed regular hexahedron, arithmetic sequence axes, orthonormal arithmetic sequence axes, and spiral-like axes are constructed in accordance with the given arrangement of deployment axes that satisfy the constraint conditions to verify the feasibility of the proposed method. 相似文献
5.
Seyedeh Mozhgan Seyed-Talebi Iraj Kazeminezhad Hossein Motamedi 《Ceramics International》2018,44(12):13457-13462
The TiO2 hollow spheres were synthesized using a green, cheap, and easy process, in which carbonaceous spheres were chosen as the removable template. The prepared materials were characterized by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Energy-dispersive X-ray spectroscopy (EDX), Atomic force microscopy (AFM), Fourier Transform Infrared Spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET) analysis. According to the results, the obtained mesoporous TiO2 hollow spheres demonstrated an external diameters less than 200?nm with shell thickness around 40?nm. The antibacterial activities of the TiO2 hollow spheres were evaluated against gram-positive (Bacillus subtilis and Staphylococcus aureus) and gram-negative (Escherichia coli and Pseudomonas aeruginosa). No antibacterial activity was found for TiO2 hollow spheres in the used concentrations. TiO2 hollow spheres were loaded with gentamycin as a selected antibiotic to magnify their benefits in biomedical applications. TiO2 hollow spheres exhibited good antibiotic carrier activity for the direct delivery of gentamicin, which was attributed to interaction between gentamicin and surface due to their larger specific surface area, more abundant porous structure, and their spherical morphology. The application of TiO2 hollow spheres as gentamicin carrier undoubtedly opens an avenue to use hollow sphere materials in other drug delivery applications. 相似文献
6.
Yifei Wang Shouying Huang Xinsheng Teng Hongyu Wang Jian Wang Qiao Zhao Yue Wang Xinbin Ma 《Frontiers of Chemical Science and Engineering》2020,14(5):802
The Fischer–Tropsch synthesis (FTS) continues to be an attractive alternative for producing a broad range of fuels and chemicals through the conversion of syngas (H2 and CO), which can be derived from various sources, such as coal, natural gas, and biomass. Among iron carbides, Fe2C, as an active phase, has barely been studied due to its thermodynamic instability. Here, we fabricated a series of Fe2C embedded in hollow carbon sphere (HCS) catalysts. By varying the crystallization time, the shell thickness of the HCS was manipulated, which significantly influenced the catalytic performance in the FTS. To investigate the relationship between the geometric structure of the HCS and the physic-chemical properties of Fe species, transmission electron microscopy, X-ray diffraction, N2 physical adsorption, X-ray photoelectron spectroscopy, hydrogen temperature-programmed reduction, Raman spectroscopy, and Mössbauer spectroscopy techniques were employed to characterize the catalysts before and after the reaction. Evidently, a suitable thickness of the carbon layer was beneficial for enhancing the catalytic activity in the FTS due to its high porosity, appropriate electronic environment, and relatively high Fe2C content. 相似文献
7.
8.
Hossein Vojoudi Jahan B. Ghasemi Ahmadreza Hajihosseinloo Bahareh Bastan Alireza Badiei 《Advanced Powder Technology》2021,32(4):1060-1069
A hybrid nanocomposite of alumina and hematite was synthesized by ultrasonic spray pyrolysis technique. The study of microscopic images, mapping analysis, and XRD patterns revealed that the Al2O3 – Fe2O3 nanocomposite was composed of separated spherical particles with a thin layer ball-shaped structure that metal oxides are uniformly distributed in the wall of hollow sphere particles, led to a coherent and monotonous construction. A series of coefficients of equilibrium sorption of polycyclic aromatic hydrocarbons (PAHs) as hazardous materials were measured on the prepared composite material in a batch technique. The free or pure Al2O3 or Fe2O3 showed negligible removal efficiency for the mentioned analytes. The various significant variables, such as initial analyte concentration, solution pH, adsorbent dose, and contact time to remove analyte, were studied in the aqueous solutions. Adsorption data were modeled to Langmuir, Freundlich, and Temkin isotherms, and a good correlation found in the case of Langmuir isotherm and adsorption capacity for anthracene, phenanthrene, and naphthalene were 370, 333, and 322 mg g?1, respectively. Investigation of the kinetic models proved a pseudo-second-order, and the prepared adsorbent can be reused more than 7 times without a significant decrease of adsorption performance. 相似文献
10.