全文获取类型
收费全文 | 6013篇 |
免费 | 493篇 |
国内免费 | 465篇 |
专业分类
电工技术 | 399篇 |
综合类 | 640篇 |
化学工业 | 640篇 |
金属工艺 | 812篇 |
机械仪表 | 400篇 |
建筑科学 | 206篇 |
矿业工程 | 157篇 |
能源动力 | 157篇 |
轻工业 | 174篇 |
水利工程 | 52篇 |
石油天然气 | 154篇 |
武器工业 | 50篇 |
无线电 | 445篇 |
一般工业技术 | 639篇 |
冶金工业 | 322篇 |
原子能技术 | 46篇 |
自动化技术 | 1678篇 |
出版年
2024年 | 9篇 |
2023年 | 60篇 |
2022年 | 100篇 |
2021年 | 131篇 |
2020年 | 158篇 |
2019年 | 135篇 |
2018年 | 127篇 |
2017年 | 176篇 |
2016年 | 178篇 |
2015年 | 190篇 |
2014年 | 344篇 |
2013年 | 357篇 |
2012年 | 321篇 |
2011年 | 440篇 |
2010年 | 311篇 |
2009年 | 380篇 |
2008年 | 342篇 |
2007年 | 416篇 |
2006年 | 392篇 |
2005年 | 343篇 |
2004年 | 299篇 |
2003年 | 232篇 |
2002年 | 198篇 |
2001年 | 168篇 |
2000年 | 158篇 |
1999年 | 142篇 |
1998年 | 137篇 |
1997年 | 109篇 |
1996年 | 88篇 |
1995年 | 92篇 |
1994年 | 88篇 |
1993年 | 63篇 |
1992年 | 57篇 |
1991年 | 35篇 |
1990年 | 40篇 |
1989年 | 39篇 |
1988年 | 31篇 |
1987年 | 20篇 |
1986年 | 5篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1983年 | 11篇 |
1982年 | 4篇 |
1981年 | 8篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1959年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有6971条查询结果,搜索用时 31 毫秒
61.
《Calphad》2019
The Fe−Si−Zr alloys have attracted considerable interests in recent decades. It is important to study this ternary phase diagram for experimental design. In this paper, the Fe−Si−Zr ternary system is investigated by combining the experiments and thermodynamic calculations. Liquidus surface projection of the Fe−Si−Zr system is characterised using X-ray powder diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectrometer (EDS) and differential thermal analysis (DTA). The liquidus projection of this ternary system is constructed by identifying primary crystallization phases and invariant reaction temperatures in the as-cast alloys. Eleven different primary solidification regions are observed. Based on the experimental results of this work and the data from the previous work in the literature, the thermodynamic calculation of the Fe−Si−Zr system is performed using CALPHAD (CALculation of PHAse Diagrams) technique. A set of self-consistent thermodynamic parameters of the Fe−Si−Zr system is obtained. The calculated results are in good agreement with the experimental data. This study provides a set of reliable thermodynamic parameters to the Fe-based thermodynamic database, and a cost-effective tool to design experiments and manufacturing processes. 相似文献
62.
Dmitry Sukhomlinov Lassi Klemettinen Olli Virtanen Yann Lahaye Petri Latostenmaa Ari Jokilaakso 《Canadian Metallurgical Quarterly》2020,59(1):67-77
ABSTRACTBehaviour of trace elements in the nickel matte smelting was studied at 1673 K (1400°C) by equilibration-quenching techniques followed by direct phase analyses using electron probe X-ray microanalysis and laser ablation-inductively coupled plasma-mass spectrometry. The matte-slag samples at silica saturation were equilibrated with SO2-CO-CO2-Ar mixtures of fixed pSO2, pS2 and pO2 in order to obtain a pre-determined oxidation degree for the sulphide matte, and thus to generate a targeted iron concentration of the nickel-copper–iron sulphide matte (Ni:Cu = 5, w/w), depending on the slag chemistry. The slag composition was varied from 0 to 2 wt-% K2O and 0–10 wt-% MgO in silica saturation. The studied trace elements were Co, Ge, Pb, Se and Sn, but also the matte-to-slag distributions of the slag forming fluxing components Mg (MgO) and Si (SiO2) were determined experimentally. Selenium was the only trace element studied which strongly enriched in the low-iron nickel mattes, and the deportment became larger when the sulphide matte depleted with iron. All the other trace elements behaved in the opposite way. 相似文献
63.
64.
《Calphad》2015
The phase diagram of the quaternary system LiCl–NaCl–KCl–H2O have been predicted with a Pitzer–Simonson–Clegg thermodynamic model by combining the binary and ternary model parameters, which were determined by simulating reliable experimental data. The predicted phase diagram shows a good agreement with the available experiment data from the literature. The other thermodynamic properties (e.g. water activity) of the quaternary and its sub-ternary systems have been investigated by the model and compared with the experimental data in literature. Significant improvements have been made in comparison with assessments. 相似文献
65.
Traditional multi-objective evolutionary algorithms have encountered difficulties when handling many-objective problems. This is due to the loss of selection pressure incurred by the growing size of objective space. A variety of environmental selection operators have been proposed to address the issue, each has its distinct benefits and drawbacks. We develop a novel ensemble framework to enhance the effectiveness and robustness of many-objective optimization. The framework incorporates multiple environmental selection operators to guide the search, which are then viewed as voters to construct a mating pool. We design an ensemble mating selection strategy that makes decisions based on the preference information provided by the voters: individuals elected by more voters will be assigned larger possibilities to enter the mating pool. By doing so, high quality offspring can be reproduced from the elected promising candidates. To accommodate the multiple selection operators for voting, the framework maintains multiple parallel populations, where each population is updated by one of the selection operators. An instantiation of the framework with three popular operators is presented as a prime example. Extensive experiments have been conducted on a number of many-objective problems to examine the effectiveness of the proposed approach. Experimental results show that the mating selection strategy is capable of improving the quality of the obtained solution set. 相似文献
66.
《Calphad》2019
First-principles calculations were carried out in order to investigate the stability and properties of the random Ti1-xSixC solid solutions (alloys) with both the B1 and B3 structures. Lattice parameter, total energy, formation energy, phonon spectra, and elastic properties were studied as functions of composition. The phase diagram, in particular, binodal and spinodal curves were calculated. It was established that at 0 K the B1 alloys are energetically favorable at 0 ≤ x < 0.5, while the B3 alloys are favorable at 0.5 ≤ x ≤ 1.0. It was found that the contribution to the Gibbs free energy coming from the lattice vibrations strongly reduces the critical temperature of stabilization of the solid solutions. Calculated elastic moduli, Debye temperature, and Vickers hardness do not point to any strength enhancement of the alloys compared to TiC and SiC. Analysis of the spatial distribution of the Young and shear moduli shows that the B3 alloys exhibit much more spatial anisotropy of the elastic moduli than the B1 alloys. 相似文献
67.
《Calphad》2016
Thermodynamic optimization of the Au–Sc and Fe–Sc systems was carried out by means of the CALPHAD (CALculation of PHAse Diagram) method on the basis of the available experimental data in literature. Redlich–Kister polynomials were used to describe the excess Gibbs energy of solution phases, and all the compounds are treated as stoichiometric ones. The Au–Sc system was described thermodynamically for the first time, and the Fe–Sc system was re-optimized by considering the new experimental data about enthalpies of mixing of the liquid phase. A set of self-consistent parameters was obtained for each of these two binary systems, respectively. 相似文献
68.
介绍对称分量法的基本知识,提出D,yn11变压器低压侧发生不对称短路时,高压侧短路穿越电流分布的图析方法,为理解《工业与民用配电设计手册》(第三版)表7-28~表7-30提供依据。 相似文献
69.
70.