全文获取类型
收费全文 | 804篇 |
免费 | 44篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 19篇 |
综合类 | 1篇 |
化学工业 | 192篇 |
金属工艺 | 13篇 |
机械仪表 | 13篇 |
建筑科学 | 96篇 |
矿业工程 | 1篇 |
能源动力 | 21篇 |
轻工业 | 61篇 |
水利工程 | 6篇 |
石油天然气 | 2篇 |
无线电 | 64篇 |
一般工业技术 | 147篇 |
冶金工业 | 23篇 |
原子能技术 | 15篇 |
自动化技术 | 176篇 |
出版年
2024年 | 2篇 |
2023年 | 14篇 |
2022年 | 22篇 |
2021年 | 28篇 |
2020年 | 10篇 |
2019年 | 13篇 |
2018年 | 13篇 |
2017年 | 13篇 |
2016年 | 34篇 |
2015年 | 22篇 |
2014年 | 25篇 |
2013年 | 54篇 |
2012年 | 37篇 |
2011年 | 74篇 |
2010年 | 47篇 |
2009年 | 51篇 |
2008年 | 52篇 |
2007年 | 48篇 |
2006年 | 46篇 |
2005年 | 45篇 |
2004年 | 31篇 |
2003年 | 23篇 |
2002年 | 20篇 |
2001年 | 12篇 |
2000年 | 8篇 |
1999年 | 12篇 |
1998年 | 6篇 |
1997年 | 14篇 |
1996年 | 14篇 |
1995年 | 11篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1990年 | 6篇 |
1989年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1970年 | 2篇 |
1966年 | 1篇 |
1937年 | 2篇 |
排序方式: 共有850条查询结果,搜索用时 31 毫秒
71.
72.
Hertwig Ralph; Herzog Stefan M.; Schooler Lael J.; Reimer Torsten 《Canadian Metallurgical Quarterly》2008,34(5):1191
Boundedly rational heuristics for inference can be surprisingly accurate and frugal for several reasons. They can exploit environmental structures, co-opt complex capacities, and elude effortful search by exploiting information that automatically arrives on the mental stage. The fluency heuristic is a prime example of a heuristic that makes the most of an automatic by-product of retrieval from memory, namely, retrieval fluency. In 4 experiments, the authors show that retrieval fluency can be a proxy for real-world quantities, that people can discriminate between two objects' retrieval fluencies, and that people's inferences are in line with the fluency heuristic (in particular fast inferences) and with experimentally manipulated fluency. The authors conclude that the fluency heuristic may be one tool in the mind's repertoire of strategies that artfully probes memory for encapsulated frequency information that can veridically reflect statistical regularities in the world. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
73.
Rates of synonymous and nonsynonymous nucleotide substitutions and codon usage bias (ENC) were estimated for a number of nuclear and chloroplast genes in a sample of centric and pennate diatoms. The results suggest that DNA evolution has taken place, on an average, at a slower rate in the chloroplast genes than in the nuclear genes: a rate variation pattern similar to that observed in land plants. Synonymous substitution rates in the chloroplast genes show a negative association with the degree of codon usage bias, suggesting that genes with a higher degree of codon usage bias have evolved at a slower rate. While this relationship has been shown in both prokaryotes and multicellular eukaryotes, it has not been demonstrated before in diatoms. 相似文献
74.
A system identification method for errors-in-variables problems based on covariance matching was recently proposed. In the first step, a small amount of covariances of noisy input–output data are computed, and then a parametric model is fitted to these covariances. In this paper, the method is further analyzed and the asymptotic accuracy of the parameter estimates is derived. An explicit algorithm for computing the asymptotic covariance matrix of the parameter estimates is given, and the identification method is shown to be asymptotically statistically efficient assuming that the given information is the computed covariances. As an important byproduct, an efficient algorithm is presented for computing the covariance matrix of the computed input–output covariances. 相似文献
75.
In granulation, coating or drying of slurries on inert particles a liquid phase is added to a gas-spouted bed. The effect of liquid injection on spouting velocity, fountain height, bed pressure drop and stability of the spouting regime is examined in a 0.15 m diameter bed with four types of inert particles 2 to 5 mm in size, 1140 to 2880 kg/m3 in true density, and 1.3 and 1400 mPa·s in liquid viscosity. Key factors are the liquid content and the presence of cohesive forces due to liquid bonds between particles. In a spoutability chart the maximum spoutable liquid content is related to the ratio of inertial force of a particle to the viscous or cohesive force exerted onto the particle by the liquid film. The spoutability chart serves to define regions of stable spouting. 相似文献
76.
77.
Due to the demand of the industry for an increase of the number of I/Os, while decreasing the die size, the bond pads had
to shrink and design restrictions for the active structures underneath had to fall. This leads to new challenges for the electrical
probing and the mechanical robustness of the under-pad structures. This paper presents analytical and numerical simulation
approaches for predicting the force/travel relation of buckling beam-probes that are used for testing the electrical functionality
of back-end-of-line (BEOL) interconnect system underneath a chip pad. For this purpose we investigate, first, in a closed-form
manner, the elastic stability of the probe needle according to the large deflection theory of buckled bars. Second, we determine,
for a specific geometry of the beam, the probe forces as functions of the probe card overdrive by using the closed-form methods
as well as finite-element simulations. The results are finally compared to that obtained in (probe card) experiments. 相似文献
78.
Thermal residual stresses have been measured using X-ray diffraction in an Al-2% Mg matrix with 10, 20 or 26 vol % Al2O3 short fibres. Stress measurements were made at room temperature as well asin situ at elevated temperatures up to 250?C. The thermal stresses arise due to the difference in coefficient of thermal expansion (CTE) between the matrix and the reinforcement. The largest CTE is found in the matrix, resulting in tensile residual stresses after a temperature drop, e.g. after processing or annealing. A high fraction of reinforcement implies higher matrix stresses than a low fibre content. The stresses decrease with increasing temperature for all fibre volume fractions. Measurements are compared with calculations using a modified Eshelby model for equivalent inclusions. Parameters taken into account in the model are coefficient of thermal expansion, Young's modulus, and volume fraction and geometric shape of the reinforcing phase. A good correlation between calculations and experimental results has been found, bearing in mind that no plasticity is taken into account in the Eshelby model. The plastic behaviour of the composites has been described using a model based on a rigid spherical cavity in an elastic-plastic matrix. 相似文献
79.
In the first part of this contribution, a mathematical model was presented for a liquid fluidized bed using immobilized enzymes, with reversible Michaelis-Menten kinetics. This part is focused on the experimental results. The reaction kinetics of native and immobilized enzymes was determined in continuous stirred tank reactors under comparable conditions. The influence of external mass transfer was investigated in a fixed bed reactor column. The extend of pore diffusional resistance was examined in a continuous stirred tank reactor and with a numerical simulation. Hydrodynamics was measured in different reactor columns (diameter dt = 0.052 ? 0.225 m; length L: 1.0–2.0m) and with a static mixer. Further, the concentration profile was determined in a fluidized bed reactor with side stream analysis for different biocatalyst samples, fluid velocities and bed heights. The simulation of experimental results indicates that they are well described by the developed model. Furthermore, the model is well suited to predicting the influence of specific parameters on the effective kinetics of the biocatalyst and the expansion of the fluidized bed. 相似文献
80.
In the first part of this paper, a mathematical model is presented for a liquid fluidized bed bioreactor using immobilized enzymes with reversible Michaelis-Menten kinetics. The model is based on the axial dispersion model for the bulk liquid phase. Inter- and intraparticle mass transfer as well as enzyme catalyzed reaction inside the porous beads are considered. The overall efficiency of the biocatalysts is calculated by a numerical routine. For the calculation of the concentration profile inside the reactor, a semi-analytical solution is derived which takes into account the height dependence of the effectiveness factor. 相似文献