全文获取类型
收费全文 | 8302篇 |
免费 | 1492篇 |
国内免费 | 915篇 |
专业分类
电工技术 | 750篇 |
综合类 | 1035篇 |
化学工业 | 357篇 |
金属工艺 | 122篇 |
机械仪表 | 557篇 |
建筑科学 | 370篇 |
矿业工程 | 124篇 |
能源动力 | 185篇 |
轻工业 | 248篇 |
水利工程 | 132篇 |
石油天然气 | 154篇 |
武器工业 | 101篇 |
无线电 | 1168篇 |
一般工业技术 | 1233篇 |
冶金工业 | 162篇 |
原子能技术 | 61篇 |
自动化技术 | 3950篇 |
出版年
2024年 | 22篇 |
2023年 | 187篇 |
2022年 | 213篇 |
2021年 | 313篇 |
2020年 | 379篇 |
2019年 | 400篇 |
2018年 | 300篇 |
2017年 | 321篇 |
2016年 | 375篇 |
2015年 | 357篇 |
2014年 | 527篇 |
2013年 | 562篇 |
2012年 | 685篇 |
2011年 | 696篇 |
2010年 | 525篇 |
2009年 | 515篇 |
2008年 | 543篇 |
2007年 | 700篇 |
2006年 | 514篇 |
2005年 | 476篇 |
2004年 | 372篇 |
2003年 | 306篇 |
2002年 | 260篇 |
2001年 | 197篇 |
2000年 | 200篇 |
1999年 | 114篇 |
1998年 | 123篇 |
1997年 | 82篇 |
1996年 | 77篇 |
1995年 | 83篇 |
1994年 | 46篇 |
1993年 | 38篇 |
1992年 | 42篇 |
1991年 | 16篇 |
1990年 | 23篇 |
1989年 | 20篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 11篇 |
1984年 | 11篇 |
1983年 | 10篇 |
1982年 | 8篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1976年 | 3篇 |
1958年 | 2篇 |
1955年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
1.
This work presents an analytical approach to investigate the mechanical and thermal buckling of functionally graded materials sandwich truncated conical shells resting on Pasternak elastic foundations, subjected to thermal load and axial compressive load. Shells are reinforced by closely spaced stringers and rings, in which the material properties of shells and stiffeners are graded in the thickness direction following a general sigmoid law distribution and a general power law distribution. Four models of coated shell-stiffener arrangements are investigated. The change of spacing between stringers in the meridional direction also is taken into account. Two cases on uniform temperature rise and linear temperature distribution through the thickness of shell are considered. Using the first-order shear deformation theory, Lekhnitskii smeared stiffener technique and the adjacent equilibrium criterion, the linearization stability equations have been established. Approximate solution satisfies simply supported boundary conditions and Galerkin method is applied to obtain closed-form expression for determining the critical compression buckling load and thermal buckling load in cases uniform temperature rise and linear temperature distribution across the shell thickness. The effects of temperature, foundation, core layer, coating layer, stiffeners, material properties, dimensional parameters and semi-vertex angle on buckling behaviors of shell are shown. 相似文献
2.
3.
彭家寅 《计算机工程与应用》2020,56(12):93-97
目的是利用高维量子纠缠态为量子信道,讨论未知单粒子态的受控隐形传输问题。以三维量子纠缠态为信道,提出一个二维任意单粒子态的受控隐形传输协议。提出了以任意[d]-维量子纠缠态为量子信道,[t]-维任意单粒子态的隐形传输协议[(t相似文献
4.
Mohammad Hossein
Abbasi Laura Iapichino Sajad Naderi Lordejani Wil Schilders Nathan van de Wouw 《International journal for numerical methods in engineering》2020,121(23):5178-5199
To circumvent restrictions of conventional drilling methods, such as slow control actions and inability to drill depleted reservoirs, a drilling method called managed pressure drilling (MPD) has been developed. In MPD, single-phase flow processes can be modeled as a feedback interconnection of a high-order linear system and a low-order nonlinear system. These nonlinearities appear locally both inside and at the boundaries of the computational domain. To obtain a fast simulation platform for real-time purposes (eg, online model-based controller implementation), model order reduction is required for MPD. However, the local nonlinearities render applying model order reduction techniques challenging. In this study, a new approach is proposed to deal with such nonlinearities within the reduced basis (RB) context and it is successfully tested on a model for MPD. Contrary to the classical RB technique, the proposed approach not only does not generate nonphysical spikes at the locations of these local nonlinearities but also yields high speedup factors. The obtained reduced-order model can be used for efficient online simulation and controller design for drilling systems with MPD. 相似文献
5.
Phosphoric Acid-assisted Pretreatment Strategy for the Rational Synthesis of Lignin-derived Hierarchical Porous Carbon Toward High-performance Supercapacitors 下载免费PDF全文
In this article, a facile two-step activation method, coupled with phosphoric acid (H3PO4)-assisted pretreatment and followed KOH activation, was reported for constructing hierarchical porous carbon (HPC) materials derived from lignin. The introduction of H3PO4, cross-linked with lignin sources generated phosphate (and/or polyphosphate) ester groups throughout the lignin structure, which endowed the pre-activated intermediate char (IC) with a hierarchical porous structure. Such phosphate esters contributed to the multi-scale pore structure within the pre-activated IC, which was beneficial for the uniform distribution and impregnation of subsequent KOH activators, thus leading to the formation of HPC materials. The as-prepared HPC exhibited a large specific surface area (SSA) of 1345.1 m2/g, which ensures the accessibility of the ion diffusion pathways. The supercapacitors integrated with HPC delivered a high specific capacitance of 241 F/g (in a three-electrode system) and outstanding rate capability with an 80.9% capacitance retention from 0.5 A/g to an ultra-high current density of 50 A/g. 相似文献
6.
7.
硅负极具有高比容量的显著优势,其理论比容量(4 200 mA∙h/g)达到传统石墨负极的10倍以上,被认为是锂离子电池最有潜力的负极之一。然而,硅负极存在导电性较差、充放电过程中体积膨胀巨大等诸多问题,导致其循环性能较差,限制了大规模实际应用。本文提供了一种高性能硅负极的制备方法及应用,通过将硅负极分散在多级孔碳中,连同黏结剂聚丙烯腈涂覆在集流体上,再对极片进行热处理实现聚丙烯腈碳包覆,有效提高电极的整体导电性并能为巨大的体积变化提供空间,从而提升硅负极的大倍率性能和循环稳定性。 相似文献
8.
Synthesis of Hierarchical 4H/fcc Ru Nanotubes for Highly Efficient Hydrogen Evolution in Alkaline Media 下载免费PDF全文
Hierarchical metal nanostructures containing 1D nanobuilding blocks have stimulated great interest due to their abundant active sites for catalysis. Herein, hierarchical 4H/face‐centered cubic (fcc) Ru nanotubes (NTs) are synthesized by a hard template‐mediated method, in which 4H/fcc Au nanowires (NWs) serve as sacrificial templates which are then etched by copper ions (Cu2+) in dimethylformamide. The obtained hierarchical 4H/fcc Ru NTs contain ultrathin Ru shells (5–9 atomic layers) and tiny Ru nanorods with length of 4.2 ± 1.1 nm and diameter of 2.2 ± 0.5 nm vertically decorated on the surface of Ru shells. As an electrocatalyst for the hydrogen evolution reaction in alkaline media, the hierarchical 4H/fcc Ru NTs exhibit excellent electrocatalytic performance, which is better than 4H/fcc Au‐Ru NWs, commercial Pt/C, Ru/C, and most of the reported electrocatalysts. 相似文献
9.
10.
In this paper, a robust controller for a Six Degrees of Freedom (6 DOF) coaxial octorotor helicopter control is proposed in presence of actuator faults. Radial Base Function Neural Network (RBFNN), Fuzzy Logic Control approach (FLC) and Sliding Mode Control (SMC) technique are used to design a controller, named Fault Tolerant Control (FTC), for each subsystem of the octorotor helicopter. The proposed FTC scheme allows avoiding difficult modeling, attenuating the chattering effect of the SMC, reducing the rules number of the fuzzy controller, and guaranteeing the stability and the robustness of the system. The simulation results show that the proposed FTC can greatly alleviate the chattering effect, good tracking in presence of actuator faults. 相似文献