全文获取类型
收费全文 | 126283篇 |
免费 | 3102篇 |
国内免费 | 665篇 |
专业分类
电工技术 | 2451篇 |
综合类 | 342篇 |
化学工业 | 24773篇 |
金属工艺 | 6100篇 |
机械仪表 | 3312篇 |
建筑科学 | 3460篇 |
矿业工程 | 153篇 |
能源动力 | 6780篇 |
轻工业 | 8796篇 |
水利工程 | 642篇 |
石油天然气 | 362篇 |
武器工业 | 3篇 |
无线电 | 10313篇 |
一般工业技术 | 25580篇 |
冶金工业 | 21683篇 |
原子能技术 | 3337篇 |
自动化技术 | 11963篇 |
出版年
2023年 | 1032篇 |
2022年 | 745篇 |
2021年 | 1575篇 |
2020年 | 1772篇 |
2019年 | 1630篇 |
2018年 | 2013篇 |
2017年 | 2894篇 |
2016年 | 3063篇 |
2015年 | 2351篇 |
2014年 | 3851篇 |
2013年 | 6851篇 |
2012年 | 4245篇 |
2011年 | 6147篇 |
2010年 | 4807篇 |
2009年 | 5736篇 |
2008年 | 4909篇 |
2007年 | 5484篇 |
2006年 | 4986篇 |
2005年 | 4418篇 |
2004年 | 3717篇 |
2003年 | 4094篇 |
2002年 | 3526篇 |
2001年 | 2980篇 |
2000年 | 2674篇 |
1999年 | 3532篇 |
1998年 | 9119篇 |
1997年 | 5581篇 |
1996年 | 3782篇 |
1995年 | 2215篇 |
1994年 | 2010篇 |
1993年 | 2261篇 |
1992年 | 1045篇 |
1991年 | 1037篇 |
1990年 | 880篇 |
1989年 | 797篇 |
1988年 | 619篇 |
1987年 | 892篇 |
1986年 | 915篇 |
1985年 | 1184篇 |
1984年 | 1204篇 |
1983年 | 919篇 |
1982年 | 952篇 |
1981年 | 906篇 |
1980年 | 787篇 |
1979年 | 773篇 |
1978年 | 612篇 |
1977年 | 483篇 |
1976年 | 437篇 |
1975年 | 306篇 |
1974年 | 316篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
《Advanced Powder Technology》2022,33(8):103664
Powder transport systems are ubiquitous in various industries, where they can encounter single powder flow, two-phase flow with solids carried by gas or liquid, and gas–solid–liquid three-phase flow. System geometry, operating conditions, and particle properties have significant impacts on the flow behavior, making it difficult to achieve good transportation of granular materials. Compared to experimental trials and theoretical studies, the numerical approach provides unparalleled advantages over the investigation and prediction of detailed flow behavior, of which the discrete element method (DEM) can precisely capture complex particle-scale information and attract a plethora of research interests. This is the first study to review recent progress in the DEM and coupled DEM with computational fluid dynamics for extensive powder transport systems, including single-particle, gas–solid/solid–liquid, and gas–solid–liquid flows. Some important aspects (i.e., powder electrification during pneumatic conveying, pipe bend erosion, non-spherical particle transport) that have not been well summarized previously are given special attention, as is the application in some new-rising fields (ocean mining, hydraulic fracturing, and gas/oil production). Studies involving important large-scale computation methods, such as the coarse grained DEM, graphical processing unit-based technique, and periodic boundary condition, are also introduced to provide insight for industrial application. This review study conducts a comprehensive survey of the DEM studies in powder transport systems. 相似文献
3.
《Advanced Powder Technology》2022,33(12):103855
In a narrow channel, the apparent relative viscosity of a suspension with finite-size particles is strongly dependent on its microscopic particle arrangement. Relative viscosity increases when suspended particles flow near the channel wall; thus, a suspension in a narrow channel does not always exhibit the same rheological properties even if the concentration is the same. In this study, we focus on the inertia and concentration of particles in a narrow channel and consider their effects on the microscopic particle arrangement and macroscopic suspension rheology. Two-dimensional pressure-driven suspension flow simulations were performed using a two-way coupling scheme, and normalized particle density distribution (PDD) were implemented to consider their particle arrangements. The results demonstrated that the velocity profiles for the particle suspension were changed by the Reynolds number and particle concentration because of the interactions between particles according to the power-law index. These changes affected the particle equilibrium positions in the channel, and the subsequent changes in solvent layer thickness caused changes in the macroscopic apparent viscosity. The behavior of microscopic particles played important roles in determining macroscopic rheology. Thus, we have confirmed that a normalized PDD can be used to estimate and assess the macroscopic rheology of a suspension. 相似文献
4.
《Soils and Foundations》2022,62(1):101103
The present study proposes a new elasto-plastic constitutive model that considers different types of hydrates in pore spaces. Many triaxial compression tests on both methane hydrate-bearing soils and carbon dioxide hydrate-bearing soils have been carried out over the last few decades. It has been revealed that methane hydrate-bearing soils and carbon dioxide hydrate-bearing soils have different strength and dilatancy properties even though they have the same hydrate contents. The reason for this might be due to the different types of hydrate morphology. In this study, therefore, the effect of the hydrate morphology on the mechanical response of gas-hydrate-bearing sediments is investigated through a model analysis by taking into account the different hardening rules corresponding to each type of hydrate morphology. In order to evaluate the capability of the proposed model, it is applied to the results of past triaxial compression tests on both methane hydrate-containing and carbon dioxide hydrate-containing sand specimens. The model is found to successfully reproduce the different stress–strain relations and dilatancy behaviors, by only giving consideration to the different morphology distributions and not changing the fitting parameters. The model is then used to predict a possible range in which the maximum deviator stress can move for various hydrate morphology ratios; the range is defined as the strength-band. The predicted curve of the maximum deviator stress obtained by the constitutive model matches the empirical equations obtained from past experiments. It supports the fact that the hydrate morphology ratio changes with the total hydrate saturation. These findings will contribute to a better understanding of the relation between the microscopic structures and macro-mechanical behaviors of gas-hydrate-bearing sediments. 相似文献
5.
《Ceramics International》2022,48(17):24157-24191
Great progress in the development of low-cost ceramic membranes from alternative materials have been achieved recently towards various application especially water and wastewater treatment. However, their significance has not been fully recognized and understood especially in term of their microstructural analysis such as formation of grain growth and microcracks. This review paper summarizes fabrication method, alternative materials, microstructure, wettability, mechanical properties and application of low-cost ceramic membrane. The fabrication method including slip casting, tape casting, extrusion, pressing method and phase inversion technique are described. Alternative materials used in low-cost ceramic membrane fabrication are discussed and categorized into clays, agricultural waste, industrial waste and animal bone waste. The mechanisms of morphology formation, microstructure and wettability properties are analysed. Modification strategies for the surface of low-cost ceramic membrane are discussed, and classified into modification for separation application, modification for photocatalytic application and modification for membrane distillation and membrane contactor system. Modification improves the membrane structure by changing the pore size, porosity and wettability properties of low-cost ceramic membranes. Mechanical properties of low-cost ceramic membranes are also discussed in detail towards several mechanism, like grain growth phenomenon and formation of microcracks which also considered as membrane defects. Grain growth phenomenon can be divided into normal and abnormal grain growth. Meanwhile, formation of microcracks could be occurred in single-phase polycrystalline ceramics that have anisotropic grains or biphasic polycrystalline grains. The application of low-cost ceramic membrane in seawater desalination, oily wastewater treatment, heavy metal adsorption, textile separation and photocatalytic application are reviewed. Finally, some possible opportunities and challenges for further development of low-cost ceramic membrane are pointed out. 相似文献
6.
8.
《International Journal of Hydrogen Energy》2022,47(29):13887-13899
We propose a self-sustaining power supply system consisting of a “Hybrid Energy Storage System (HESS)” and renewable energy sources to ensure a stable supply of high-quality power in remote islands. The configuration of the self-sustaining power supply system that can utilize renewable energy sources effectively on remote islands where the installation area is limited is investigated. It is found that it is important to select renewable energy sources whose output power curve is close to the load curve to improve the efficiency of the system. The operation methods that can increase the cost-effectiveness of the self-sustaining power supply system are also investigated. It is clarified that it is important for increasing the cost effectiveness of the self-sustaining power supply system to operate the HESS with a smaller capacity of its components by setting upper limits on the output power of the renewable energy sources and cutting the infrequent generated power. 相似文献
9.
《International Journal of Hydrogen Energy》2022,47(21):11116-11127
An important difficulty associated with alkaline water electrolysis is the rise in anode overpotential attributable to bubble coverage of the electrode surface. For this study, a system with a high-speed video camera was developed, achieving in-situ observation of bubble generation on an electrode surface, monitoring an area of 1.02 mm2 at 6000 frames per second. The relation between polarization curve (current density up to 3.0 A cm?2) and oxygen bubble generation behavior on nickel electrodes having cylindrical wires and rectangular wires of different sizes (100–300 μm) was clarified. The generated bubbles slide upward, contacting the electrode surface and detaching at the top edge. Observations indicate that small electrodes have short bubble residence time and thin bubble covering layer on the electrode. As a result, the small electrode diameter contributes to smaller overpotential at high current density. 相似文献
10.
《International Journal of Hydrogen Energy》2022,47(33):15084-15093
The effect of ammonia (NH3) contained in hydrogen (H2) gas on hydrogen environment embrittlement (HEE) of SCM440 low-alloy steel was studied in association with the NH3 concentration, loading rate, and gas pressure. NH3 worked as both mitigator of the HEE and inducer of hydrogen embrittlement (HE) depending on the testing conditions. The mitigation of the HEE was achieved by the deactivation of the iron (Fe) surface for H2 dissociation caused by the preferential adsorption of NH3 on the Fe surface, which is enhanced by the increase in the NH3 concentration and decrease in the H2 gas pressure. NH3 induced HE was caused due to creating hydrogen by the NH3 decomposition. Since the NH3 decomposition rate is low, the induction effect was observed when the loading rate was low. The effect of NH3 was determined by the competition of the mitigation and induction effects. 相似文献