全文获取类型
收费全文 | 1035篇 |
免费 | 19篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 15篇 |
化学工业 | 228篇 |
金属工艺 | 35篇 |
机械仪表 | 17篇 |
建筑科学 | 40篇 |
矿业工程 | 7篇 |
能源动力 | 9篇 |
轻工业 | 123篇 |
水利工程 | 2篇 |
石油天然气 | 17篇 |
无线电 | 110篇 |
一般工业技术 | 148篇 |
冶金工业 | 136篇 |
原子能技术 | 6篇 |
自动化技术 | 164篇 |
出版年
2021年 | 11篇 |
2020年 | 12篇 |
2019年 | 19篇 |
2018年 | 31篇 |
2017年 | 9篇 |
2016年 | 18篇 |
2015年 | 15篇 |
2014年 | 16篇 |
2013年 | 53篇 |
2012年 | 19篇 |
2011年 | 58篇 |
2010年 | 51篇 |
2009年 | 36篇 |
2008年 | 52篇 |
2007年 | 38篇 |
2006年 | 23篇 |
2005年 | 41篇 |
2004年 | 27篇 |
2003年 | 26篇 |
2002年 | 27篇 |
2001年 | 18篇 |
2000年 | 10篇 |
1999年 | 13篇 |
1998年 | 27篇 |
1997年 | 20篇 |
1996年 | 18篇 |
1995年 | 16篇 |
1994年 | 13篇 |
1993年 | 18篇 |
1992年 | 27篇 |
1991年 | 16篇 |
1990年 | 18篇 |
1989年 | 18篇 |
1986年 | 10篇 |
1985年 | 16篇 |
1984年 | 9篇 |
1983年 | 8篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 12篇 |
1978年 | 7篇 |
1977年 | 10篇 |
1976年 | 15篇 |
1974年 | 7篇 |
1973年 | 8篇 |
1971年 | 9篇 |
1969年 | 7篇 |
1963年 | 8篇 |
1955年 | 11篇 |
排序方式: 共有1057条查询结果,搜索用时 15 毫秒
101.
102.
103.
Jolanta Światowska-Mrowiecka Vincent Maurice Sandrine Zanna Lorena Klein Emrick Briand Ian Vickridge Philippe Marcus 《Journal of power sources》2007
Cyclic voltammetry, XPS, RBS and AFM have been combined to study the ageing mechanism of Li intercalation in V2O5 thin films prepared by thermal oxidation of vanadium metal. Multi-cycling tests were performed in 1 M LiClO4-PC in the potential range E ∈ [3.8, 2.8 V] versus Li/Li+, corresponding to the α-to-δ phase transition. XPS and AFM were performed using direct anaerobic and anhydrous transfer. Capacity fading remains inferior to 20% during ∼2500 cycles. XPS shows slight modifications of the oxide composition with a V4+ concentration increasing from ∼5% prior to cycling to ∼16–27% after cycling, due to Li trapped in the oxide film and to the loss of V2O5 active material. The presence of lithium carbonate and lithium-alkyl carbonate species evidences the formation of the so-called SEI layer. AFM evidences the loss of crystalline material by grain exfoliation from the outer V2O5 layer of the oxide film. By further exfoliation, the inner VO2 layer of the oxide film is reached and pits are formed, occupying ∼9–13% of the surface. This de-cohesion at grain boundaries is attributed to the strain generated by repeated lattice distortions. After 3300 cycles, the disappearance of lithium carbonates, whereas Li-alkyl carbonates and/or Li-alkoxides remain on the surface, indicates the dissolution and/or conversion of the SEI layer. After 4500 cycles, the oxide film became very labile and could be stripped away by rinsing to reveal the vanadium metal substrate. 相似文献
104.
Fe(3)O(4) coated polypyrrole (PPy) magnetic nanocomposite was prepared via in situ polymerization of pyrrole monomer for the removal of highly toxic Cr(VI). Structure and morphology of the prepared nanocomposite were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction pattern, Field emission scanning electron microscopy (FE-SEM) and high resolution transmission electron microscopy (HR-TEM). Electron spin resonance (ESR) studies confirmed that the nanocomposite is magnetic in nature. Up to 100% adsorption was found with 200mg/L Cr(VI) aqueous solution at pH 2. Adsorption of Cr(VI) on the surface of the adsorbent was confirmed by the ATR-FTIR and X-ray photoelectron spectroscopy (XPS). XPS studies also suggested that ion exchange and reduction on the surface of the nanocomposite may be the possible mechanism for Cr(VI) removal by the PPy/Fe(3)O(4) nanocomposite. Adsorption results showed that Cr(VI) removal efficiency by the nanocomposite decreased with an increase in pH. Adsorption kinetics was best described by the pseudo-second-order rate model. Isotherm data fitted well to the Langmuir isotherm model. Thermodynamic study revealed that the adsorption process is endothermic and spontaneous in nature. Desorption experiment showed that in spite of the very poor recovery of the adsorbed Cr(VI); the regenerated adsorbent can be reused successfully for two successive adsorption-desorption cycles without appreciable loss of its original capacity. 相似文献
105.
Synthesis of few-layered graphene by ion implantation of carbon in nickel thin films 总被引:1,自引:0,他引:1
Baraton L He Z Lee CS Maurice JL Cojocaru CS Gourgues-Lorenzon AF Lee YH Pribat D 《Nanotechnology》2011,22(8):085601
The synthesis of few-layered graphene is performed by ion implantation of carbon species in thin nickel films, followed by high temperature annealing and quenching. Although ion implantation enables a precise control of the carbon content and of the uniformity of the in-plane carbon concentration in the Ni films before annealing, we observe thickness non-uniformities in the synthesized graphene layers after high temperature annealing. These non-uniformities are probably induced by the heterogeneous distribution/topography of the graphene nucleation sites on the Ni surface. Taken altogether, our results indicate that the number of graphene layers on top of Ni films is controlled by the nucleation process on the Ni surface rather than by the carbon content in the Ni film. 相似文献
106.
Bloemberg TG Wessels HJ van Dael M Gloerich J van den Heuvel LP Buydens LM Wehrens R 《Analytical chemistry》2011,83(13):5197-5206
The identification of differential patterns in data originating from combined measurement techniques such as LC/MS is pivotal to proteomics. Although "shotgun proteomics" has been employed successfully to this end, this method also has severe drawbacks, because of its dependence on largely untargeted MS/MS sequencing and databases for statistical analyses. Alternatively, several MS-signal-based (MS/MS-independent) methods have been published that are mainly based on (univariate) Student's t-tests. Here, we present a more robust multivariate alternative employing linear discriminant analysis. Like the t-test-based methods, it is applied directly to LC/MS data, instead of using MS/MS measurements. We demonstrate the method on a number of simulated data sets, as well as on a spike-in LC/MS data set, and show its superior performance over t-tests. 相似文献
107.
Solid-phase extraction microtips are important devices in modern bioanalytics, as they allow miniaturized sample preparation for mass spectrometric analysis. Here we introduce the use of cotton wool for the preparation of filter-free HILIC SPE microtips. To this end, pieces of cotton wool pads (approximately 500 μg) were packed into 10 μL pipet tips. The performance of the tips was evaluated for microscale purification of tryptic IgG Fc N-glycopeptides. Cotton wool HILIC SPE microtips allowed the removal of salts, most nonglycosylated peptides, and detergents such as SDS from glycoconjugate samples. MALDI-TOF-MS glycopeptide profiles were very repeatable with different tips as well as reused tips, and very similar profiles were obtained with different brands of cotton wool pads. In addition, we used cotton HILIC microtips to purify N-glycans after N-glycosidase F treatment of IgG and transferrin followed by MALDI-TOF-MS detection. In conclusion, we establish cotton wool microtips for glycan and glycopeptide purification with subsequent mass spectrometric detection. 相似文献
108.
Theresa N Ngoma Maurice Monjerezi John F Leslie Brighton M Mvumi Jagger JW Harvey Limbikani Matumba 《Journal of the science of food and agriculture》2024,104(2):561-571
Postharvest management is critical to attaining household food, nutrition, and income security. Hermetic grain storage bags offer an effective pesticide-free way to protect stored grain against fungal and insect infestation. We evaluated articles indexed in the Web of Science that included experiments comparing the storage efficacy of conventional and hermetic storage bags based on grain germination rate, insect infestation, physical damage, mycotoxin contamination, and changes in weight and moisture content. Compared with grain stored in hermetic bags, grain stored in conventional bags lost 3.6-fold more seed viability, contained 42-fold more insects, had 11-fold more physical damage, and lost 23-fold more grain weight, while grain moisture levels were similar for both hermetic and conventional storage bags. Mycotoxin contamination levels were not as frequently assessed. Levels could be low in grain stored in both types of bags, or levels could be low in hermetic bags and significantly higher in conventional bags. The improved properties of grain stored in hermetic bags can increase food security and household income by providing safe storage options for maintaining seed germinability, and for consumption and/or sale when food supplies are high, or when prices are low. Hermetic bags are economically feasible for use by subsistence farmers in Sub-Saharan Africa for grain for household consumption and for carrying-over seed for planting in the next season. Additional studies are needed to verify the mycotoxin contamination results and to determine if there are differences in functional food characteristics, e.g. flavor and cooking properties, that have not been as comprehensively studied. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. 相似文献
109.
R. W. Rydin D. Maurice T. H. Courtney 《Metallurgical and Materials Transactions A》1993,24(1):175-185
The motions of grinding media and powder in an attritor canister were studied by means of filming the agitated charge and
frame-by-frame scrutiny of the footage. In conjunction with auxiliary experiments, this permitted semiquantitative analysis
of the milling action. In particular, the mill can be divided into several regions characterized by different balances between
direct impacts and rolling/sliding of the grinding media. Simple calculations suggest that impacts are more capable of effecting
mechanical alloying (MA) than are rolling or sliding events in an attritor. Powder circulation within an operating mill was
also investigated. Based on the results and the accompanying analysis, concepts for improved attritor design are presented.
D. Maurice is formerly a Graduate Student, Department of Materials Science and Engineering, University of Virginia, Charlottesville,
VA 22903 相似文献
110.
The aim of the work summarized in this paper is the theoretical modelling of laminated composite shells of arbitrary shape, in order to: improve the calculus of shear stresses, and especially to avoid shear correction factors; account for continuity conditions of displacements and transverse shear stresses at layer interfaces as well as compatibility conditions of transverse shear stresses on the bonding surfaces; estimate the relevance of shear refinements, of membrane refinements and of the transverse stretching beyond standard kinematics; and to analyse the sensitivity to edge effects for significant boundary conditions. 相似文献