全文获取类型
收费全文 | 53665篇 |
免费 | 7779篇 |
国内免费 | 5345篇 |
专业分类
电工技术 | 5176篇 |
技术理论 | 2篇 |
综合类 | 6758篇 |
化学工业 | 4938篇 |
金属工艺 | 2170篇 |
机械仪表 | 4811篇 |
建筑科学 | 6677篇 |
矿业工程 | 1859篇 |
能源动力 | 1773篇 |
轻工业 | 1621篇 |
水利工程 | 2025篇 |
石油天然气 | 1584篇 |
武器工业 | 1063篇 |
无线电 | 4384篇 |
一般工业技术 | 6720篇 |
冶金工业 | 1667篇 |
原子能技术 | 447篇 |
自动化技术 | 13114篇 |
出版年
2024年 | 144篇 |
2023年 | 1058篇 |
2022年 | 1737篇 |
2021年 | 2024篇 |
2020年 | 2085篇 |
2019年 | 1747篇 |
2018年 | 1736篇 |
2017年 | 2090篇 |
2016年 | 2400篇 |
2015年 | 2415篇 |
2014年 | 3420篇 |
2013年 | 3542篇 |
2012年 | 4252篇 |
2011年 | 4240篇 |
2010年 | 3315篇 |
2009年 | 3351篇 |
2008年 | 3293篇 |
2007年 | 3875篇 |
2006年 | 3314篇 |
2005年 | 2799篇 |
2004年 | 2251篇 |
2003年 | 1909篇 |
2002年 | 1591篇 |
2001年 | 1422篇 |
2000年 | 1204篇 |
1999年 | 937篇 |
1998年 | 753篇 |
1997年 | 642篇 |
1996年 | 535篇 |
1995年 | 523篇 |
1994年 | 417篇 |
1993年 | 324篇 |
1992年 | 261篇 |
1991年 | 218篇 |
1990年 | 198篇 |
1989年 | 193篇 |
1988年 | 140篇 |
1987年 | 66篇 |
1986年 | 36篇 |
1985年 | 47篇 |
1984年 | 49篇 |
1983年 | 42篇 |
1982年 | 34篇 |
1981年 | 12篇 |
1980年 | 29篇 |
1979年 | 26篇 |
1978年 | 7篇 |
1959年 | 11篇 |
1958年 | 6篇 |
1955年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Sk Tanbir Islam Sudip K. Samanta Santanu Das Himadri Chattopadhyay 《Journal of the American Ceramic Society》2022,105(7):4608-4620
The micro-powder injection molding (micro-PIM) process has the potential to bridge the gap between the design and manufacturing of micro-components that are often used in small and handy devices. Numerical modeling helps to analyze and overcome various difficulties of micro-PIM. In the present work, a numerical model is developed to predict the powder–binder separation (a common defect in PIM and especially severe in micro-PIM) during the injection of an alumina feedstock. A powder–binder separation criterion is proposed dealing with applied injection pressure and friction force between the powder and binder. An indirect comparison of feedstock travel time between two locations is used to validate the model. The predicted segregation from the simulated result is supported by a qualitative experimental measurement. The developed model can be used to optimize injection parameters to get a defect-free product. 相似文献
2.
3.
Mixed reality can overlay and display 3D digital content in the real world, convey abstract concepts to users, and promote the understanding of complex tasks. However, the abstract graphics overlaid on the physical space may cause a certain cognitive load for local users and reduce the efficiency of collaboration. To improve the efficiency of remote collaboration, we conducted an elicitation study on assembly tasks, explored the user needs for collaboration, and defined the design goals of our remote collaboration method. Inspired by the mirror-neuron mechanism, we present an imitative collaboration method that allows local users to imitate the interaction behavior of remote users to complete tasks. We also propose a series of interaction methods for remote users to select, copy, and interact with the local point clouds to facilitate the expression of collaboration intentions. Finally, the results of a user study evaluating our imitative collaboration method on assembly tasks are reported, confirming that our method improves collaboration efficiency while reducing the cognitive load of local users. 相似文献
4.
《International Journal of Hydrogen Energy》2022,47(99):41878-41890
Hydrogen is being considered a ‘fuel of the future,’ a viable alternative to fossil fuels in fuel cell vehicles. Using Density Functional Theory simulations, reversible, onboard hydrogen storage in Sc-decorated triazine-based graphitic carbon nitride (g-C3N4) has been explored. Sc atom binds strongly on the g-C3N4 structure with a binding energy of ?7.13 eV. Each Sc atom can reversibly bind 7 molecules of hydrogen, giving a net gravimetric storage capacity of 8.55 wt%, an average binding energy of ?0.394 eV per H2, and a corresponding desorption temperature of 458.28 K, fulfilling the criteria prescribed by the US Department of Energy. The issue of transition metal clustering has been investigated by computing the diffusion energy barrier (2.79 eV), which may be large enough to hinder the clustering tendencies. The structural integrity of Sc-g-C3N4 has been verified through ab-initio Molecular Dynamics simulations. The interaction mechanism of Sc over g-C3N4 and H2 over Sc-g-C3N4 has been explored using density of states and charge transfer analysis. A flow of charge from valence 3d orbitals of Sc towards vacant orbitals of g-C3N4 during the binding of Sc over g-C3N4 is observed. The binding of H2 on Sc-g-C3N4 may be via Kubas type of interactions which is stronger than physisorption due to net charge gain by H 1s orbital from Sc 3d orbital. Our systematic investigations indicate that Sc-decorated g-C3N4 may be a high-performance material for reversible hydrogen storage applications. 相似文献
5.
《International Journal of Hydrogen Energy》2022,47(36):16121-16131
Ammonia is considered as a promising hydrogen or energy carrier. Ammonia absorption or adsorption is an important aspect for both ammonia removal, storage and separation applications. To these ends, a wide range of solid and liquid sorbents have been investigated. Among these, the deep eutectic solvent (DES) is emerging as a promising class of ammonia absorbers. Herein, we report a novel type of DES, i.e., metal-containing DESs for ammonia absorption. Specifically, the NH3 absorption capacity is enhanced by ca. 18.1–36.9% when a small amount of metal chlorides, such as MgCl2, MnCl2 etc., are added into a DES composed of resorcinol (Res) and ethylene glycol (EG). To our knowledge, the MgCl2/Res/EG (0.1:1:2) DES outperforms most of the reported DESs. The excellent NH3 absorption performances of metal–containing DESs have been attributed to the synergy of Lewis acid–base and hydrogen bonding interactions. Additionally, good reversibility and high NH3/CO2 selectivity are achieved over the MgCl2/Res/EG (0.1:1:2) DES, which enables it to be a potential NH3 absorber for further investigations. 相似文献
6.
7.
Xiehuan Li Dan Ye 《International Journal of Adaptive Control and Signal Processing》2022,36(1):104-121
In this article, the memory-based dynamic event-triggered controller design issue is investigated for networked interval type-2 (IT2) fuzzy systems under non-periodic denial-of-service (DoS) attacks. For saving limited network bandwidth, a novel memory-based dynamic event-triggered mechanism (DETM) is proposed to schedule data communication. Unlike existing event-triggered generators, the developed memory-based DETM can utilize a series of newly released signals and further save network resources by introducing interval dynamic variables. Moreover, to improve design flexibility, an IT2 fuzzy controller with freely selectable fuzzy rule number and premise membership functions (MFs) is synthesized. Then, a new switched time-delay system with imperfectly matched MFs is established under the consideration of memory-based DETM and DoS attacks simultaneously. Besides, based on the property of MFs, the boundary information of membership grades and slack matrices are introduced in the stability analysis. Furthermore, by using a piecewise Lyapunov–Krasovskii method, membership-functions-dependent criteria are deduced to ensure the asymptotic stability of built fuzzy switched systems. Finally, the effectiveness of proposed control strategies is demonstrated by simulation examples. 相似文献
8.
为了监测绕组变压器的静态应力场和发生短路等故障时的动态应力变化,设计了一种用于电气设备状态监测的新式FBG传感器。该传感器由聚醚醚酮材料封装的FBG构成,通过内部圆锥形空腔结构实现将轴向应力集中于FBG敏感位置。通过仿真对不同压力强度下传感器结构的应力场部分及形变趋势进行了计算与分析,论证了设计的合理性。实验分别对静态载荷和动态冲击进行测试,结果显示,在静态压载测试中,当100 N相似文献
9.
《International Journal of Hydrogen Energy》2022,47(52):22203-22214
The gas purging states affect electricity output and energy storage capacity of unitized regenerative fuel cells. In this study, a model of unitized regenerative fuel cell is established. Cell voltages and operating temperatures influences on the dynamic distribution of thermal fluid during purging process and the discharge of residual liquid water in electrolytic cell mode are investigated. The motivation of the present study is better understanding the gas purging characteristics and its effect on reaction behaviors of unitized regenerative fuel cells. Simulation results reveal a significant influence of purging gas temperature on the water flooding and a great effect of operating voltage on the water diffusion. The operating temperature of electrolytic cell model almost has little effect on purging results at different cell temperature and the same purging gas temperature. When the purging gas temperature is changed, higher temperatures of cell and purging gas facilitate liquid water discharging out from the cell regions. In cell water flooding situation, when having large liquid content, the purging gas has little effects on the water expelling process. 相似文献
10.
《International Journal of Hydrogen Energy》2022,47(63):27080-27095
The study of shock wave propagation in a detonation chamber is of great importance as a part of the plate forming process. Investigations related to the effects of premixed gas detonation on the deflection of a plate require in-depth examination. An Eulerian-Lagrangian numerical simulation is conducted using the space-time conservation element and solution element method of LS-DYNA software to study the effect of confined multi-point ignited gaseous mixture on the dynamic response of thin plates clamped at the end of a combustion chamber. The FSI couples a Lagrangian finite element solver with a Eulerian fluid solver in a 2D space with detailed chemistry of H2–O2 mixture. The solution contains the detonation wave propagation through the combustion chamber and its interaction with the plate. The influence of variation in the multi-point ignition locations and combustion chamber dimensions on the pressure history and plate deflection is studied. To verify the model, a comparison with the experimental study is carried out using an adjustable model representative of the real experiment. The verified model is used to link the evolution of plate shape with the arrival time and intensity of shock waves within the chamber. It is found that a longer distance between the ignition point and the plate intensifies the ultimate deflection of the plate. In addition, a fairly large combustion area employed in a direction rather than transverse to the plate surface is unable to influence the ultimate deformation of the plate. 相似文献