全文获取类型
收费全文 | 4329篇 |
免费 | 998篇 |
国内免费 | 534篇 |
专业分类
电工技术 | 173篇 |
综合类 | 482篇 |
化学工业 | 611篇 |
金属工艺 | 194篇 |
机械仪表 | 120篇 |
建筑科学 | 62篇 |
矿业工程 | 42篇 |
能源动力 | 180篇 |
轻工业 | 57篇 |
水利工程 | 37篇 |
石油天然气 | 128篇 |
武器工业 | 33篇 |
无线电 | 903篇 |
一般工业技术 | 949篇 |
冶金工业 | 83篇 |
原子能技术 | 16篇 |
自动化技术 | 1791篇 |
出版年
2024年 | 14篇 |
2023年 | 126篇 |
2022年 | 123篇 |
2021年 | 182篇 |
2020年 | 263篇 |
2019年 | 258篇 |
2018年 | 235篇 |
2017年 | 278篇 |
2016年 | 249篇 |
2015年 | 257篇 |
2014年 | 310篇 |
2013年 | 326篇 |
2012年 | 365篇 |
2011年 | 336篇 |
2010年 | 253篇 |
2009年 | 276篇 |
2008年 | 248篇 |
2007年 | 257篇 |
2006年 | 217篇 |
2005年 | 187篇 |
2004年 | 132篇 |
2003年 | 119篇 |
2002年 | 108篇 |
2001年 | 113篇 |
2000年 | 82篇 |
1999年 | 81篇 |
1998年 | 54篇 |
1997年 | 73篇 |
1996年 | 66篇 |
1995年 | 40篇 |
1994年 | 37篇 |
1993年 | 31篇 |
1992年 | 27篇 |
1991年 | 16篇 |
1990年 | 22篇 |
1989年 | 12篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 11篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1977年 | 3篇 |
1975年 | 2篇 |
1973年 | 4篇 |
1951年 | 3篇 |
排序方式: 共有5861条查询结果,搜索用时 15 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(12):7783-7792
Efficient and sustainable Janus catalysts toward hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are highly desirable for future hydrogen production via water electrolysis. Herein we report an active Janus electrocatalyst of amorphous-crystalline cobalt-molybdenum bimetallic phosphide heterostructured nanosheets on nickel foam (CoMoP/CoP/NF) for efficient electrolysis of alkaline water. As-reported CoMoP/CoP/NF consists of amorphous bimetal phosphide nanosheets doped with crystalline CoMoP/CoP heterostructured nanoparticles on NF. It can efficiently catalyze both HER (η = 127 mV@100 mA cm?2) and OER (η = 308 mV@100 mA cm?2) in alkaline electrolyte with long-term durability. Serving as anode and cathode of water electrolyzer, CoMoP/CoP/NF generates electrolytic current of 10, 50 and 100 mA cm?2 at low voltage of 1.50, 1.59, and 1.67 V, respectively. 相似文献
2.
《International Journal of Hydrogen Energy》2022,47(58):24358-24373
Ni–Co/Mg(Al)O alloy catalysts with different Co/Ni molar ratios have been prepared from Ni- and Co-substituted Mg–Al hydrotalcite-like compounds (HTlcs) as precursors and tested for dry reforming of methane. The XRD characterization shows that Ni–Co–Mg–Al HTlcs are decomposed by calcination into Mg(Ni,Co,Al)O solid solution, and by reduction finely dispersed alloy particles are formed. H2-TPR indicates a strong interaction between nickel/cobalt oxides and magnesia, and the presence of cobalt in Mg(Ni,Co,Al)O enhances the metal-support interaction. STEM-EDX analysis reveals that nickel and cobalt cations are homogeneously distributed in the HTlcs precursor and in the derived solid solution, and by reduction the resulting Ni–Co alloy particles are composition-uniform. The Ni–Co/Mg(Al)O alloy catalysts exhibit relatively high activity and stability at severe conditions, i.e., a medium temperature of 600 °C and a high space velocity of 120000 mL g?1 h?1. In comparison to monometallic Ni catalyst, Ni–Co alloying effectively inhibits methane decomposition and coke deposition, leading to a marked enhancement of catalytic stability. From CO2-TPD and TPSR, it is suggested that alloying Ni with Co favors the CO2 adsorption/activation and promotes the elimination of carbon species, thus improving the coke resistance. Furthermore, a high and stable activity with low coking is demonstrated at 750 °C. The hydrotalcite-derived Ni–Co/Mg(Al)O catalysts show better catalytic performance than many of the reported Ni–Co catalysts, which can be attributed to the formation of Ni–Co alloy with uniform composition, proper size, and strong metal-support interaction as well as the presence of basic Mg(Al)O as support. 相似文献
3.
《International Journal of Hydrogen Energy》2022,47(26):12903-12913
Oxygen evolution reaction (OER) plays a decisive role in electrolytic water splitting. However, it is still challengeable to develop low-cost and efficient OER electrocatalysts. Herein, we present a combination strategy via heteroatom doping, hetero-interface engineering and introducing conductive skeleton to synthesize a hybrid OER catalyst of CNT-interconnected iron-doped NiP2/Ni2P (Fe-(NiP2/Ni2P)@CNT) heterostructural nanoflowers by a simple hydrothermal reaction and subsequent phosphorization process. The optimized Fe-(NiP2/Ni2P)@CNT catalyst delivers an ultralow Tafel slope of 46.1 mV dec?1 and overpotential of 254 mV to obtain 10 mA cm?2, which are even better than those of commercial OER catalyst RuO2. The excellent OER performance is mainly attributed to its unique nanoarchitecture and the synergistic effects: the nanoflowers constructed by a 2D-like nanosheets guarantee large specific area and abundant active sites; the highly conductive CNT skeleton and the electronic modulation by the heterostructural NiP2/Ni2P interface and the hetero-atom doping can improve the catalytic activity; porous nanostructure benefits electrolyte penetration and gas release; most importantly, the rough surface and rich defects caused by phosphorization process can further enhance the OER performance. This work provides a deep insight to boost catalytic performance by heteroatom doping and interface engineering for water splitting. 相似文献
4.
《Advanced Powder Technology》2022,33(11):103777
In this study the constructional modification of Graphitic carbon nitride nanosheet (GCN-ns) has been made with the aid of ZnCr layered double hydroxide (ZC-LDH) in a unique 2D-2D structure to enhance its visible light absorption. Optical and morphological study presents successful incorporation of ZC-LDH on the surface of GCN-ns. Through adjusting of GCN-ns by ZC-LDH lower recombination rate of e?/h+ pairs, longer lifetimes and an increase in contamination reduction was brought out. The binary nanocomposite was employed to effectively degrade Rhodamine B under UV/vis light irradiation. The improvement in photocatalytic abilities was proven to be related to in situ self-production of H2O2 on GCN-ns/ZC-LDH surface by Xe light irradiation which in return accounts for additional hydroxide radical generation. Radical quenching experiments specified the main active species involved while the consequent step-scheme (S-scheme) charge transfer mechanism was proposed. 相似文献
5.
6.
《International Journal of Hydrogen Energy》2021,46(80):39645-39657
This article reported a series of g–C3N4–CNS (g-C3N4 and carbon nanosheets) composite carriers formed by the hydrothermal method, and then the ethylene glycol reduction method was used to anchor Pt nanoparticles on the g–C3N4–CNS carrier to form the Pt/g–C3N4–CNS catalysts. The electrochemical test for the electrocatalytic oxidation of methanol (MOR) shown that the Pt/20%g–C3N4–CNS catalyst has the best catalytic performance and stability. These Pt/g–C3N4–CNS catalysts were analyzed by TEM, XRD, XPS, and BET characterization. It is discovered that the amount of g-C3N4 greatly influenced the structure and chemical properties of Pt/CNS precursor. As the content of g-C3N4 increases, the content of pyridine nitrogen and pyrrole nitrogen also increases, and N species can enhance the interaction between Pt nanoparticles and CNS, promote Pt dispersion, and increase the specific surface area of the catalyst. Similarly, an excessive addition of g-C3N4 will cause a sharp decline in the conductivity of the catalyst, and then led to the decline of MOR activity. 相似文献
7.
《International Journal of Hydrogen Energy》2021,46(64):32403-32412
Porous carbon nanostructures are promising supports for stabilizing the highly dispersed metal nanoparticles and facilitating the mass transfer during the reaction, which are critical to achieve the high efficiency of hydrogen generation from sodium borohydride dehydrogenation. Herein, the catalytically active porous architectures are simply prepared by using 2-methylimidazole and melamine as reactive sources. The structural and compositional characterizations reveal the coexistence of metallic cobalt and N-doped carbon in porous architectures. Electron microscopy observations indicate that the synthesized products are smartly constructed from the carbon nanosheets with densely dispersed Co nanoparticles. Due to the notable structural features, the prepared Co@NC-600 sample presents the highly efficient activity for catalytic hydrolysis of NaBH4 with a hydrogen generation rate of 2574 mL min−1 gcat−1 and an activation energy of 47.6 kJ mol−1. The catalytically active metallic Co and suitable support-effect of N-doped carbon are responsible for catalytic dehydrogenation. 相似文献
8.
论文从映射的角度,将哈希函数分为三类:严格哈希函数、计算哈希函数和实用哈希函数。在此基础上,根据二元域上二次方程x2 x c=0的部分不可解的性质,构造了一种计算哈希函数,它满足单向性和一一对应性,同时具有运算速度快的优点。 相似文献
9.
Cathy Lawson Douglas C. Montgomery 《Quality and Reliability Engineering International》2006,22(8):971-984
Variation exists in all processes. Significant work has been done to identify and remove sources of variation in manufacturing processes resulting in large returns for companies. However, business process optimization is an area that has a large potential return for a company. Business processes can be difficult to optimize due to the nature of the output variables associated with them. Business processes tend to have output variables that are binary, nominal or ordinal. Examples of these types of output include whether a particular event occurred, a customer's color preference for a new product and survey questions that assess the extent of the survey respondent's agreement with a particular statement. Output variables that are binary, nominal or ordinal cannot be modeled using ordinary least‐squares regression. Logistic regression is a method used to model data where the output is binary, nominal or ordinal. This article provides a review of logistic regression and demonstrates its use in modeling data from a business process involving customer feedback. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
10.
Wiltrout Charles; Dogra Samriti; Linster Christiane 《Canadian Metallurgical Quarterly》2003,117(2):236
Studies on odor mixture perception suggest that although odor components can often be identified in mixtures, mixtures can also give rise to novel perceptual qualities that are not present in the components. Using an olfactory habituation task, the authors evaluated how the perceptual similarity between components in a mixture affects the perceptual quality of the mixture itself. Rats perceived binary mixtures composed of similar components as different from their 2 components, whereas binary mixtures composed of dissimilar components were perceived as very similar to their components. Results show that for both types of mixtures, pretraining to Component A reduces subsequent learning about Component B in rats trained in the presence of A. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献