全文获取类型
收费全文 | 91138篇 |
免费 | 9223篇 |
国内免费 | 5797篇 |
专业分类
电工技术 | 7557篇 |
综合类 | 7869篇 |
化学工业 | 12679篇 |
金属工艺 | 7781篇 |
机械仪表 | 5174篇 |
建筑科学 | 6672篇 |
矿业工程 | 1980篇 |
能源动力 | 4750篇 |
轻工业 | 4746篇 |
水利工程 | 1996篇 |
石油天然气 | 3839篇 |
武器工业 | 1068篇 |
无线电 | 12231篇 |
一般工业技术 | 9583篇 |
冶金工业 | 5256篇 |
原子能技术 | 1430篇 |
自动化技术 | 11547篇 |
出版年
2024年 | 468篇 |
2023年 | 1372篇 |
2022年 | 2474篇 |
2021年 | 2954篇 |
2020年 | 3116篇 |
2019年 | 2648篇 |
2018年 | 2481篇 |
2017年 | 3363篇 |
2016年 | 3545篇 |
2015年 | 3644篇 |
2014年 | 5484篇 |
2013年 | 5905篇 |
2012年 | 6565篇 |
2011年 | 7207篇 |
2010年 | 5107篇 |
2009年 | 5284篇 |
2008年 | 4952篇 |
2007年 | 6079篇 |
2006年 | 5353篇 |
2005年 | 4440篇 |
2004年 | 3817篇 |
2003年 | 3293篇 |
2002年 | 2736篇 |
2001年 | 2389篇 |
2000年 | 1955篇 |
1999年 | 1607篇 |
1998年 | 1294篇 |
1997年 | 1158篇 |
1996年 | 1002篇 |
1995年 | 814篇 |
1994年 | 712篇 |
1993年 | 507篇 |
1992年 | 500篇 |
1991年 | 414篇 |
1990年 | 336篇 |
1989年 | 220篇 |
1988年 | 181篇 |
1987年 | 111篇 |
1986年 | 104篇 |
1985年 | 97篇 |
1984年 | 112篇 |
1983年 | 65篇 |
1982年 | 70篇 |
1981年 | 52篇 |
1980年 | 48篇 |
1979年 | 31篇 |
1978年 | 15篇 |
1977年 | 23篇 |
1959年 | 15篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
G. SAID 《Fatigue & Fracture of Engineering Materials & Structures》2006,29(8):606-614
Costs of ASTM E399 and ASTM E1921 tests, which were developed to determine the fracture toughness (KIc) and the ductile–brittle transition temperature of ferritic steels, respectively, are considered high and the procedures are also very complicated. In this study, a method, which is more cost‐effective and easier to carry out, is proposed. 相似文献
72.
The isothermal strain‐life approach is the most commonly used approach for determining fatigue damage, particularly when yielding occurs. Computationally it is extremely fast and generally requires elastic finite element analyses only. Therefore, it has been adapted for variable temperatures. Local temperature—stress–strain behaviour is modelled with an operator of the Prandtl type. The hysteresis loops are supposed to be stabilized and no creep is considered. The consequences of reversal point filtering are analysed. The approach is finally compared to several thermo‐mechanical fatigue tests and the Skelton model. 相似文献
73.
74.
Low carbon steel was oxidized over the temperature range 1000‐1250°C in O2‐CO2‐H2O‐N2, O2‐H2O‐N2, and O2‐CO2‐N2 gas mixtures. Oxidation times were 12‐120 min. and the scales were 50‐2000 μm thick. The variations of these parameters were chosen to elucidate the phase composition of oxide scales under conditions similar to those of reheating furnaces in hot strip mills, using either thin slab casting or conventional casting and rolling technology. Two types of scales have been observed which are influenced by the furnace atmosphere, oxidation time, and temperature. The first type is a crystalline scale with an irregular outer surface, composed mostly of wustite (FeO), and a negligible amount of magnetite (Fe3O4). The second type is the classical three‐layer scale, composed of wustite (FeO), magnetite (Fe3O4), and hematite (Fe2O3). In general, the experiments showed that an increase in oxidation time decreased the percentage of wustite while the percentages of magnetite and hematite increased. A rise in oxygen concentration in the gas mixture increased the percentages of magnetite and hematite, confirming earlier experimental findings. In water vapour‐free atmospheres O2‐CO2‐N2, the oxide scales had a low percentage of wustite, and high percentage of magnetite and hematite. Carbon dioxide showed a small influence at 1100°C, and a negligible one at 1250°C. 相似文献
75.
通常的数据采集与记录装置不易实现多量程测量。通过对标度方程进行分析得知,要改变量程只须改变两个参数——标度因子和量程下限。我们设计了一个使用单片机的多量程数据采集和记录装置,能处理多达256种量程。本文叙述了算法分析、硬件和软件的设计以及该装置的性能指标。 相似文献
76.
The role of gas phase CH3 radicals in the oxidative coupling of CH4 over 1 wt% Sr/La2O3 is supported by the observations that (i) this is a very effective catalyst for the generation of CH3 · radicals and (ii) the concentration of CH3 · radicals increases with temperature over the range of 450 °C–800 °C. 相似文献
77.
78.
论述了重构轮式工程机械轮边减速器优化设计数学模型的必要性,给出了精确化的目标函数,全面化和准确化的设计变量、基于并行设计的约束条件;介绍了对优化解适用性评价的方法和手段。巧妙地解决了优化解中离散变量的圆整问题,提供了基于MATLAB的求解反渐开线函数的M文件。 相似文献
79.
In their comments on the authors' article (see record 2003-10163-009), R. C. Serlin, B. E. Wampold, and J. R. Levin (see record 2003-10163-011) and P. Crits-Christoph, X. Tu, and R. Gallop (see record 2003-10163-010) took issue with the authors' suggestion to evaluate therapy studies with nested providers with a fixed model approach. In this rejoinder, the authors' comment on Serlin et al's critique by showing that their arguments do not apply, are based on misconceptions about the purpose and nature of statistical inference, or are based on flawed reasoning. The authors also comment on Crits-Christoph et al's critique by showing that the proposed approach is very similar to, but less inclusive than, their own suggestion. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
80.
Baudilio Coto Carmen Martos Jos L. Pea Juan J. Espada María D. Robustillo 《Fuel》2008,87(10-11):2090-2094
Wax precipitation is one of the most important flow assurance problems. Unfortunately, experimental data are very scarce to confirm existing models for prediction of such precipitation problem. This work reports a new experimental method. Multistage fractional wax precipitation was carried out by decreasing the temperature of crude oil. No solvent dilution was used, so the effect of solvent on temperature wax precipitation was avoided. The reproducibility of the method was tested with comparable results. The precipitation curve and the wax appearance temperature were obtained for two crude oils with different chemical nature using the reported method. 相似文献