全文获取类型
收费全文 | 4410篇 |
免费 | 346篇 |
国内免费 | 31篇 |
专业分类
电工技术 | 62篇 |
综合类 | 26篇 |
化学工业 | 1222篇 |
金属工艺 | 139篇 |
机械仪表 | 222篇 |
建筑科学 | 178篇 |
矿业工程 | 13篇 |
能源动力 | 237篇 |
轻工业 | 357篇 |
水利工程 | 99篇 |
石油天然气 | 68篇 |
武器工业 | 3篇 |
无线电 | 378篇 |
一般工业技术 | 754篇 |
冶金工业 | 145篇 |
原子能技术 | 37篇 |
自动化技术 | 847篇 |
出版年
2024年 | 17篇 |
2023年 | 62篇 |
2022年 | 96篇 |
2021年 | 225篇 |
2020年 | 253篇 |
2019年 | 293篇 |
2018年 | 388篇 |
2017年 | 341篇 |
2016年 | 309篇 |
2015年 | 194篇 |
2014年 | 338篇 |
2013年 | 537篇 |
2012年 | 376篇 |
2011年 | 364篇 |
2010年 | 227篇 |
2009年 | 227篇 |
2008年 | 127篇 |
2007年 | 105篇 |
2006年 | 68篇 |
2005年 | 32篇 |
2004年 | 32篇 |
2003年 | 24篇 |
2002年 | 23篇 |
2001年 | 13篇 |
2000年 | 13篇 |
1999年 | 19篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 6篇 |
1995年 | 14篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1984年 | 6篇 |
1982年 | 5篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有4787条查询结果,搜索用时 15 毫秒
101.
Pouria Fattahi Ali Borhan Mohammad Reza Abidian 《Advanced materials (Deerfield Beach, Fla.)》2013,25(33):4529-4529
102.
In this study, thermal and small-scale effects on the flapwise bending vibrations of a rotating nanoplate, which can be the basis of nano-turbine design, have been analyzed. The nano-turbine is made of an orthotropic nanoplate with a setting angle that is modeled based on the classical plate theory (CPT) with cantilever boundary conditions. The axial forces are also included in the model as the true spatial variation due to the rotation and temperature change. The governing equations and boundary conditions are derived according to Hamilton's principle and the governing equations are solved with the aid of the generalized differential quadrature method. The effects of small-scale parameter, nondimensional angular velocity, temperature change, and setting angles in the first four nondimensional frequencies are discussed. Due to the consideration of the rotating effects, results of this study are applicable in nano-machines, such as nano-motors, nano-rotor, and other rotating nano-structures. Also, by considering the effect of thermal loading on rotation of a nanoplate, the results are useful in the design of nano-turbines. 相似文献
103.
A miniaturized microstrip antenna on a planar layered periodic structure is proposed, designed and fabricated. The proposed structure miniaturizes patch antennas in the microwave band. With varying the parameters of the proposed structure, the achieved miniaturization factor can be adjusted in the range 2.6–4.2. Numerical and experimental results are presented. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013. 相似文献
104.
Reza Sepahi Ron Steinfeld Josef Pieprzyk 《International Journal of Information Security》2014,13(4):315-333
The notion of certificateless public-key encryption (CL-PKE) was introduced by Al-Riyami and Paterson in 2003 that avoids the drawbacks of both traditional PKI-based public-key encryption (i.e., establishing public-key infrastructure) and identity-based encryption (i.e., key escrow). So CL-PKE like identity-based encryption is certificate-free, and unlike identity-based encryption is key escrow-free. In this paper, we introduce simple and efficient CCA-secure CL-PKE based on (hierarchical) identity-based encryption. Our construction has both theoretical and practical interests. First, our generic transformation gives a new way of constructing CCA-secure CL-PKE. Second, instantiating our transformation using lattice-based primitives results in a more efficient CCA-secure CL-PKE than its counterpart introduced by Dent in 2008. 相似文献
105.
106.
Fouling of heat exchangers is a prevalent operating drawback in many process industries. Efficient chemical inhibitors have predominantly been used for many years to combat deposit formation. Nevertheless, new stringent environmental legislations limit their utilization. On-line mitigation techniques, such as propulsion of projectiles at different injection rates, can also be utilized, which can, in turn, minimize the need for chemical inhibitors. Nevertheless, the experimental data are scarce and nonconclusive. In this experimental study, two spherical-type projectiles of different sizes and hardness have been used to clean the inner surface of a single heated tube that was subjected to the deposition of calcium sulfate. Projectiles were then introduced at different injection rate of every 2, 5, 10, 15, and 30 min. The experimental results show that (i) the projectiles would expedite initial nucleation of crystals even if they are soft and easy to propel inside the tube; (ii) fouling can only be mitigated if the projectiles exert a shear force such that the corresponding removal rate is greater than the net rate of the deposition; and finally (iii) harder projectiles with larger surface contact area are more efficient in cleaning the surface compared to those that are softer. 相似文献
107.
108.
Mohammad Mohammadian Maryam Ahmadi Mohammad Reza Khosravi-Nikou 《Petroleum Science and Technology》2017,35(6):608-614
Adsorption of heterocyclic sulfur- and nitrogen-containing compounds by mesostructure adsorbent (MSU-S) and its modified form with cobalt oxide is studied using model fuel. The results of characteristic tests (XRD, N2 adsorption–desorption, FTIR, and SEM) indicate that CoO impregnation causes a negative impact on mesoporous structure, crystalline phase, and particle shape along with a positive effect on surface ion exchange. CoO modification increased the adsorption loadings of DBT and BT to about 33.6% and 45.7%, respectively. For nitrogen compounds adsorption with the model fuel, adsorption loadings of quinoline and carbazole increase by 6.7% and 8.6%, respectively. Data fitting for carbazole, DBT, and BT is achieved better by the Langmuir model than the Freundlich model, and the data of quinoline fitted very well to the Freundlich model for CoO-MSU-S. 相似文献
109.
Zoya Sadighi Abolghasem Ataie Mohammad Reza Barati 《Metals and Materials International》2014,20(1):77-81
In this study, barium-doped lanthanum manganite, La0.8Ba0.2MnO3, was synthesized via a mechano-thermal route employing high energy ball milling and subsequent heat treatment. The structural evolution, morphology and thermal behaviour of the powders were evaluated using XRD, FESEM, and DTA/TGA, respectively. DTA/TGA results showed that the calcination temperature of the carbonates significantly decreased by increasing the milling time. The results revealed that single phase perovskite was formed at 900 °C in a milled sample for 2 h and this temperature decreased to 600 °C by increasing the milling time to 30 h. The mean crystallite size also decreased from 32 to 20 nm by increasing the milling time from 2 to 30 h. The reaction sequence of La0.8Ba0.2MnO3 formation via the mechano-thermal route is proposed using XRD and DTA/TGA results. FESEM micrographs showed that the mean particle size of the perovskite phase is increased slightly from 30 to 40 nm by increasing the heat treatment temperature from 600 to 900 °C. 相似文献
110.
Piri Reza Ghasemi Behrooz Yousefpour Mardali 《Metallurgical and Materials Transactions A》2018,49(3):938-945
Metallurgical and Materials Transactions A - In this study, samples with ferritic–bainitic dual phase structures consisting of 62 pct bainite were obtained from the AISI 4140 steel... 相似文献