全文获取类型
收费全文 | 518篇 |
免费 | 35篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 4篇 |
化学工业 | 113篇 |
金属工艺 | 7篇 |
机械仪表 | 19篇 |
建筑科学 | 22篇 |
矿业工程 | 1篇 |
能源动力 | 10篇 |
轻工业 | 71篇 |
水利工程 | 3篇 |
石油天然气 | 5篇 |
无线电 | 28篇 |
一般工业技术 | 99篇 |
冶金工业 | 62篇 |
原子能技术 | 5篇 |
自动化技术 | 105篇 |
出版年
2023年 | 7篇 |
2022年 | 9篇 |
2021年 | 32篇 |
2020年 | 11篇 |
2019年 | 17篇 |
2018年 | 30篇 |
2017年 | 16篇 |
2016年 | 31篇 |
2015年 | 10篇 |
2014年 | 26篇 |
2013年 | 42篇 |
2012年 | 33篇 |
2011年 | 38篇 |
2010年 | 27篇 |
2009年 | 24篇 |
2008年 | 22篇 |
2007年 | 19篇 |
2006年 | 18篇 |
2005年 | 16篇 |
2004年 | 8篇 |
2003年 | 5篇 |
2002年 | 11篇 |
2001年 | 8篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1976年 | 7篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1968年 | 2篇 |
排序方式: 共有554条查询结果,搜索用时 187 毫秒
51.
Ruben Specogna 《International journal for numerical methods in engineering》2011,86(8):1041-1068
The simultaneous use of a pair of complementary discrete formulations for electrostatic boundary value problems (BVPs) allows to accurately compute electromagnetic quantities, such as capacitance or electrostatic force with a minimum computational effort. In fact, the two formulations provide the upper and lower bounds for these quantities and their averages result quite close to the exact solution even for extremely coarse meshes. Despite the potential benefit to the many three‐dimensional large‐scale applications, taking advantage of this feature is not exploited in practice due to theoretical difficulties in the potential design. The aim of this paper is to fill this gap by rigorously introducing a pair of three‐dimensional complementary geometric formulations to solve electrostatic BVPs on domains covered by conformal polyhedral meshes. In particular, an original formulation based on a vector potential is introduced by using cohomology theory with integer coefficients. It is shown how the so‐called thick links are needed, which are representatives of the second cohomology group generators of the dielectric region. Two easy‐to‐implement graph‐theoretic algorithms to automatically find such a basis with optimal computational complexity are described. Some benchmark problems are presented to show how the simultaneous use of both formulations yields to a sensible computational advantage. Therefore, solvers based on complementary formulations should be embedded in the next‐generation of electromagnetic Computer‐Aided Engineering (CAE) softwares. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
52.
Joseph N. Grima Brian Ellul Daphne Attard Ruben Gatt Michael Attard 《Composites Science and Technology》2010
In this work a simple cylindrical structure with a stiff needle-like inclusion embedded within a much softer matrix is presented and analysed with the aim of obtaining a system with tunable thermal expansion properties. It is shown that by the correct combination of the thermal and mechanical properties of the matrix and inclusion, it is possible to design a system which can be tailor-made to exhibit particular values of the coefficient of thermal expansion (CTE) in the radial direction and also negative thermal expansion (NTE). In particular an analytical model to quantify the radial strain with changes in temperature is derived and verified through finite element analysis. The model is used to find correct property combinations which lead to particular values of thermal expansion which could also be negative or zero. 相似文献
53.
Minoru Takahashi Koichiro Adachi Ruben L. Menchavez Masayoshi Fuji 《Journal of Materials Science》2006,41(7):1965-1972
In this study, we propose a new process to fabricate electrically semi-conductive alumina by the combination of gelcasting
and reduction sintering. The process is similar to the conventional gelcasting method except for varying amounts of methacrylamide
monomer dosages at 2.83, 5.50, and 8.04 wt% relative to the mass of the slurry. Correspondingly, the rheological evaluation
of aqueous slurry was conducted. The resulting fluidity exhibited that monomer dosage until 8.04 wt% yielded slurry viscosity
of 1628 MPA·s at shear rate of 20 s−1, which was feasible for gelcasting without noticeable casting defects. The freshly gelled bodies were demolded, carefully
dried, and then sintered at different schedules in nitrogen atmosphere. The reduction-sintered samples were re-sintered in
air for comparative evaluation of physical property. The sintered alumina body was characterized by electrical resistance,
X-ray diffraction, and scanning electron microscopy. The results showed that monomer additions and sintering schedule significantly
affect in lowering electrical resistivity. The obtained lowest value was 3.6 × 106 Ω-cm with 8.04 wt% monomer dosage and sintering at 1550°C with 2 h holding time. The resulting material is classified as
semi-conductive, which is potential for electrostatic shielding applications. The effect of physical property and microstructure
on electrical conductivity and the corresponding reaction mechanism were discussed in details. 相似文献
54.
P. Ruben Mercado 《Computational Economics》2004,23(4):303-313
This article analyzes the trade-off between `caution' and `intensity' in the use of the control variable in a one-state one-control dynamic stochastic quadratic linear optimization problem with discount factor. It studies the effects that changes in uncertainty of the control parameter have on the optimal first period response of the control variable, showing that the trade-off between `caution' and `intensity' depends on the timing of the uncertainty. Given an increase in current uncertainty and an equal increase in future uncertainty, caution will always prevail over intensity. Moreover, the prevalence of caution will be enlarged as the increase in future uncertainty moves farther away into the future, while this prevalence will be reduced as the increase in future uncertainty expands into the future. Finally, for the infinite horizon case, caution is the optimal policy response. 相似文献
55.
Translated from Atomnaya énergiya, Vol. 69, No. 1, pp. 28–31, July, 1990. 相似文献
56.
Ruben Mercad-Prieto Pradeepta K. Sahoo Robert J. Falconer William R. Paterson D. Ian Wilson 《Food Hydrocolloids》2007,21(8):1275-1284
The literature reports an optimum NaOH concentration for the alkaline cleaning of whey deposits or gels; at NaOH concentrations higher than this optimum, cleaning proceeds much more slowly. Although this phenomenon is of great importance in the cleaning of dairy equipment, no conclusive physical explanation has yet been presented. In this study, we present strong evidence that the dissolution rate is affected by the equilibrium-swelling ratio in β-lactoglobulin (βLg) gels. The swelling ratio is greatly reduced in the presence of salts due to the polyelectrolyte screening effect of the cations. This has been observed in free-swelling βLg gels using gravimetrical analysis and in the uniaxial swelling of WPC gel deposits using fluid dynamic gauging. At high dissolution pH (>13.3), the high Na+ concentration reduces swelling in spite of the high surface charge of the protein. It is proposed that the reduction of the free volume inside the gel impedes the transport of the protein aggregates out of the NaOH penetration zone. We have also observed that the final dissolution rate of gels pre-soaked in 1 M NaOH or NaCl is similar, despite the difference in pH, and much lower than for untreated gels: the high Na+ concentration in the soaked gels hinders swelling, inhibiting the disentanglement of the protein clusters regardless of the high pH. 相似文献
57.
58.
59.
60.
Libkind D Moliné M Sommaruga R Sampaio JP van Broock M 《Yeast (Chichester, England)》2011,28(8):619-627
The synthesis of the UV Absorbing compounds named mycosporines (MYCs) has been detected in a few basidiomycetous yeast groups. Conspicuous accumulation of mycosporine-glutaminol-glucoside (MGG) in yeasts requires photo-induction and its photoprotective function has been postulated. The distribution of the ability to produce MYCs appeared to be related to the yeast taxonomic affiliation. In view of the potential significance of MYCs in yeast taxonomy, we here studied the distribution of this trait among dimorphic basidiomycetes of the Pucciniomycotina. Of the 94 fungal species (377 strains and 33 genera) tested, almost half were MYC-positive and MGG was the main compound produced. MGG synthesis was observed for representatives of five of seven Pucciniomycotina classes, indicating that this trait is widely distributed in this group. MGG detection proved useful for the differentiation of species of the polyphyletic genera, such as Rhodotorula and Sporobolomyces, that are phylogenetically separated. MGG quantification and UV tolerance studies in Cystobasidiomycetes supported the idea that the habitat of origin of each strains is important in the level of MGG synthesis and that MYCs have a photoprotective function in yeasts. The taxonomic value of this trait in fungal systematics is discussed. 相似文献