全文获取类型
收费全文 | 2819篇 |
免费 | 188篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 13篇 |
综合类 | 2篇 |
化学工业 | 906篇 |
金属工艺 | 18篇 |
机械仪表 | 56篇 |
建筑科学 | 129篇 |
能源动力 | 56篇 |
轻工业 | 580篇 |
水利工程 | 36篇 |
石油天然气 | 9篇 |
无线电 | 135篇 |
一般工业技术 | 433篇 |
冶金工业 | 298篇 |
原子能技术 | 8篇 |
自动化技术 | 333篇 |
出版年
2024年 | 11篇 |
2023年 | 69篇 |
2022年 | 211篇 |
2021年 | 255篇 |
2020年 | 106篇 |
2019年 | 117篇 |
2018年 | 138篇 |
2017年 | 111篇 |
2016年 | 107篇 |
2015年 | 116篇 |
2014年 | 111篇 |
2013年 | 195篇 |
2012年 | 172篇 |
2011年 | 217篇 |
2010年 | 124篇 |
2009年 | 143篇 |
2008年 | 121篇 |
2007年 | 123篇 |
2006年 | 87篇 |
2005年 | 72篇 |
2004年 | 55篇 |
2003年 | 51篇 |
2002年 | 38篇 |
2001年 | 12篇 |
2000年 | 18篇 |
1999年 | 23篇 |
1998年 | 17篇 |
1997年 | 22篇 |
1996年 | 14篇 |
1995年 | 11篇 |
1994年 | 9篇 |
1993年 | 9篇 |
1992年 | 11篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 10篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1964年 | 3篇 |
1958年 | 2篇 |
排序方式: 共有3012条查询结果,搜索用时 15 毫秒
101.
Selective hydrogenation of cinnamaldehyde using Pd catalysts supported on Mg/Al mixed oxides: Influence of the Pd incorporation method 下载免费PDF全文
María J. Martínez‐Ortiz Miguel A. de la Rosa‐Guzmán Jorge R. Vargas‐García Jorge L. Flores‐Moreno Nancy Castillo Ariel Guzmán‐Vargas Sara Morandi Rosa M. Pérez‐Gutiérrez 《加拿大化工杂志》2018,96(1):297-306
A series of hydrotalcite‐like compounds was synthesized by varying Mg/Al molar ratio with values of 2, 3, and 4. After thermal treatment at 823 K, the corresponding mixed oxides were obtained and used as catalytic supports. The incorporation of a Pd metallic phase (0.5 g/g loading), was carried out by two methods: 1) in situ vapour phase thermal decomposition, and 2) impregnation by organic method. Fresh and calcined samples were characterized by XRD and N2 sorption experiments. The basic and metal functions were analyzed by CO2‐TPD and H2‐TPR. The Pd‐support interaction was studied by FTIR spectroscopy using CO as a probe molecule while the morphology of Pd nanoparticles on the catalysts was studied by SEM, HRTEM, and theoretical simulation using the Fast Fourier Transform (FFT) method. Finally, the catalytic activity results showed a higher conversion towards hydrocinnamaldehyde in the cinnamaldehyde hydrogenation reaction for the catalysts prepared by vapour phase thermal decomposition, compared with those prepared by organic method, showing the significant dependence on the catalytic activity and the Pd incorporation method. 相似文献
102.
Mahboubeh Kiani Zitani Touradj Ebadzadeh Sara Banijamali Reza Riahifar Christian Rüssel Tilman Zscheckel Haishen Ren 《Ceramics International》2018,44(4):4016-4026
In the present research, the Li2ZnTi3O8(LZT) ceramics were synthesized throughout solid-state ceramic processing, then mixed with bismuth borate (BiBO) glass prepared based on conventional melt quenching method. Wetting behavior of BiBO glass on the LZT ceramic substrate was monitored by hot stage microscopy. Afterward, dielectric LZT ceramics containing different amounts of BiBO glass (0.25–6 wt%) were sintered at various temperatures. X-ray diffraction and electron back scatter diffraction examinations revealed the presence of two crystalline phases of Li2ZnTi3O8 and Bi2Ti2O7. The maximum value of relative density (above 95%) was obtained in the case of specimens contained more than 5 wt% glass. The microwave dielectric properties of the finally sintered BiBO glass containing LZT ceramics were as follows: dielectric constant (εr) = 21.44–25.09, quality factor (Q × f) = 10839–54708 GHz and temperature coefficient of resonant frequency (τf) = (? 15.58) ? (? 12.86)ppm/°C. 相似文献
103.
S. Ramesh K.Y. Sara Lee C.Y. Tan Y.H. Wong U. Johnson Alengaram F. Tarlochan S. Ramesh W.D. Teng U. Sutharsini Ahmed A.D. Sarhan 《Ceramics International》2018,44(16):19639-19645
The effect of various amounts of copper oxide (CuO) up to 1?wt% on the densification behaviour and mechanical properties of 3?mol% yttria-tetragonal zirconia polycrystal (Y-TZP) were studied by using microwave (MW) sintering method. The MW sintering was performed at temperatures between 1100?°C and 1400?°C, with a heating rate of 30?°C/min. and holding time of 5?min. The beneficial effect of MW in enhancing densification was also compared for the undoped and 0.2?wt% CuO-doped Y-TZP when subjected to conventional sintering (CS) method. The results showed that significant enhancement in the relative density and Vickers hardness were observed for the undoped Y-TZP when MW-sintered between 1100?°C and 1250?°C. It was revealed that the 0.2?wt% CuO-doped Y-TZP and MW sintered at 1250–1300?°C could attain ≥?99.8% of theoretical density, Vickers hardness of about 14.4?GPa, fracture toughness of 7.8 MPam1/2 and exhibited fine equiaxed tetragonal grain size of below 0.25?µm. In contrast, the addition of 1?wt% CuO was detrimental and the samples exhibited about 50% monoclinic phase upon sintering coupled with poor bulk density and mechanical properties. The study also revealed that the addition of 0.2?wt% CuO and subjected to conventional sintering produced similar densification as that obtained for microwave sintering, thus indicating that the dopant played a more significant role than the sintering method. 相似文献
104.
Sara Duce Fabio Pesciaioli Lucia Gramigna Luca Bernardi Andrea Mazzanti Alfredo Ricci Giuseppe Bartoli Giorgio Bencivenni 《Advanced Synthesis \u0026amp; Catalysis》2011,353(6):860-864
The first catalytic asymmetric Pictet–Spengler reaction of isatins is presented. BINOL‐derived phosphoric acids were found to be competent catalysts for this transformation, giving challenging spirooxindole structures bearing a quaternary stereocentre with generally good results. The 1,2,3,4‐tetrahydro‐β‐carboline products (spiroindolinones) are the core of some newly discovered anti‐malarial agents. 相似文献
105.
106.
The partial oxidation of methane/oxygen mixtures with large exhaust gas dilution (46.3 vol% H2O and 23.1 vol% CO2) has been investigated experimentally and numerically over Rh/CeO2-ZrO2, Rh/ZrO2 and Rh/α-Al2O3 catalysts. Experiments were carried out in a short-contact-time reactor at 5 bar and included exhaust gas analysis, temperature measurements along the reactor, and catalyst characterization. Additional experiments were performed in an optically accessible channel-flow reactor and involved in situ Raman measurements of major gas-phase species concentrations over the catalyst boundary layer and laser-induced fluorescence (LIF) of formaldehyde. A full elliptic two-dimensional numerical code that included elementary hetero-/homogeneous chemical reaction schemes and relevant heat transfer mechanisms in the solid was used in the simulations. The employed heterogeneous reaction mechanism, including only active Rh sites, reproduced the experiments with good accuracy. The ratio of active to geometrical surface area, deduced from hydrogen chemisorption measurements, was the single model parameter needed to account for the effect of different supports. This indicated that water activation occurring on support sites, resulting in inverse OH spillover from the support to the noble metal sites, could be neglected under the present conditions with high water dilution. An evident relationship between noble metal dispersion and catalytic behavior, in terms of methane conversion and synthesis gas yields, could be established. Both measurements and predictions indicated that an increasing Rh dispersion (in the order Rh/α-Al2O3, Rh/ZrO2, and Rh/CeO2-ZrO2) resulted in higher methane conversions, lower surface temperatures, and higher synthesis gas yields. 相似文献
107.
Sara Bernal Irene Pelaez Laura Alias Manel Baena Juan A. De Pablo-Moreno Luis J. Serrano M. Dolores Camero Eduardo F. Tizzano Ruben Berrueco Antonio Liras 《International journal of molecular sciences》2021,22(18)
Factor V is an essential clotting factor that plays a key role in the blood coagulation cascade on account of its procoagulant and anticoagulant activity. Eighty percent of circulating factor V is produced in the liver and the remaining 20% originates in the α-granules of platelets. In humans, the factor V gene is about 80 kb in size; it is located on chromosome 1q24.2, and its cDNA is 6914 bp in length. Furthermore, nearly 190 mutations have been reported in the gene. Factor V deficiency is an autosomal recessive coagulation disorder associated with mutations in the factor V gene. This hereditary coagulation disorder is clinically characterized by a heterogeneous spectrum of hemorrhagic manifestations ranging from mucosal or soft-tissue bleeds to potentially fatal hemorrhages. Current treatment of this condition consists in the administration of fresh frozen plasma and platelet concentrates. This article describes the cases of two patients with severe factor V deficiency, and of their parents. A high level of mutational heterogeneity of factor V gene was identified, nonsense mutations, frameshift mutations, missense changes, synonymous sequence variants and intronic changes. These findings prompted the identification of a new mutation in the human factor V gene, designated as Jaén-1, which is capable of altering the procoagulant function of factor V. In addition, an update is provided on the prospects for the treatment of factor V deficiency on the basis of yet-to-be-developed recombinant products or advanced gene and cell therapies that could potentially correct this hereditary disorder. 相似文献
108.
Alexander Hgsted Ahlmann Shu Fang Sussi Bagge Mortensen Line Weis Andersen Pernille Gejl Pedersen Johanne Juel Callesen Sara Thornby Bak Kate Lykke Lambertsen Ditte Caroline Andersen 《International journal of molecular sciences》2021,22(15)
Small diameter (<6 mm) vessel grafts still pose a challenge for scientists worldwide. Decellularised umbilical artery (dUA) remains promising as small diameter tissue engineered vascular graft (TEVG), yet their immunogenicity remains unknown. Herein, we evaluated the host immune responses, with a focus on the innate part, towards human dUA implantation in mice, and confirmed our findings in an ex vivo allogeneic human setup. Overall, we did not observe any differences in the number of circulating white blood cells nor the number of monocytes among three groups of mice (1) dUA patch; (2) Sham; and (3) Mock throughout the study (day −7 to 28). Likewise, we found no difference in systemic inflammatory and anti-inflammatory cytokine levels between groups. However, a massive local remodelling response with M2 macrophages were observed in the dUA at day 28, whereas M1 macrophages were less frequent. Moreover, human monocytes from allogeneic individuals were differentiated into macrophages and exposed to lyophilised dUA to maximize an eventual M1 response. Yet, dUA did not elicit any immediate M1 response as determined by the absence of CCR7 and CXCL10. Together this suggests that human dUA elicits a minimal pro-inflammatory response further supporting its use as a TEVG in an allogeneic setup. 相似文献
109.
110.
Dielectric barrier discharge (DBD) reactors used as ozone generators are well known today and widely used for water treatment and air disinfection. The purpose of this article is to propose an experimental procedure based on the response surface modeling in order to optimize the geometrical dimensions of the cylindrical shape ozone generator, i.e., the discharge gap and the electrodes length. Because an effective ozone generator is expected to give high ozone concentration with a minimum of power requirements, the applied high voltage was associated with the geometrical parameters to carry out a composite centered faces design. Obtained results indicate that for an efficient ozone generator, length of the electrodes needs to be optimized while the discharge gap should be minimized. 相似文献