全文获取类型
收费全文 | 632篇 |
免费 | 65篇 |
国内免费 | 93篇 |
专业分类
790篇 |
出版年
2024年 | 3篇 |
2023年 | 12篇 |
2022年 | 17篇 |
2021年 | 29篇 |
2020年 | 35篇 |
2019年 | 28篇 |
2018年 | 39篇 |
2017年 | 28篇 |
2016年 | 38篇 |
2015年 | 19篇 |
2014年 | 25篇 |
2013年 | 77篇 |
2012年 | 38篇 |
2011年 | 48篇 |
2010年 | 42篇 |
2009年 | 25篇 |
2008年 | 42篇 |
2007年 | 44篇 |
2006年 | 46篇 |
2005年 | 34篇 |
2004年 | 32篇 |
2003年 | 12篇 |
2002年 | 14篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1983年 | 3篇 |
1981年 | 5篇 |
1979年 | 2篇 |
排序方式: 共有790条查询结果,搜索用时 0 毫秒
251.
Sergi Ballespí Ma Claustre Jané Ma Dolors Riba 《Journal of psychopathology and behavioral assessment》2013,35(3):321-334
Given the implications of behavioral inhibition (BI) on social anxiety and depression, several cost-effective methods have been developed to detect this trait. However, there is no instrument for obtaining a systematic measurement of BI that uses the reports of mental health professionals. The present study aims to explore the psychometric properties of the Behavioral Inhibition Observation System (BIOS), a brief tool enabling clinicians to provide a quick measure of BI. Parents and teachers of 361 preschool children provided measures of BI and psychopathology. Clinicians completed the BIOS after an individual meeting with every child. Seventy-four randomly selected children were exposed to standardized observation. Two researchers completed the BIOS after standardized observation. The results show that the BIOS is structured in one dimension that explains 60 % of the total variance. It shows good internal consistency (Cronbach’s Alpha?=?.88) and good test-retest reliability. The BIOS scores moderately converge with observational measures of BI and adequately distinguish constructs not related to BI (such as aggressiveness, disruptive behavior, or peer conflict). The results support that the BIOS, an 8-item scale that takes 3 min to complete, is valid and reliable for capturing a clinician’s measure of BI. The BIOS may help to detect temperamental disposition to social anxiety. 相似文献
252.
Kaka Ma 《Philosophical Magazine Letters》2013,93(10):739-751
Previous research has revealed that thermal barrier coatings with cryomilled bond coats exhibit improved thermal cycling lifetime by growing a continuous and uniform oxide layer at a slower rate; yet the mechanism controlling the ultimate failure remains unclear. In an effort to provide a foundation for understanding the improved behavior, the influence of cryomilling on the microstructure of the NiCrAlY bond coat material is investigated in this article. Rather than focusing on the alumina scale formation, the microstructural features and their evolution within the high-velocity oxy-fuel (HVOF)-sprayed NiCrAlY bond coats themselves, prepared from conventional powder and cryomilled powder, were carefully compared through extensive scanning electron microscope/energy-dispersive X-ray spectroscopy characterization. In addition, the as-cryomilled NiCrAlY powder is characterized to provide evidence of the direct influence of cryomilling and to exclude the impact from the HVOF spraying. It is found that the essential change in microstructural features resulting from the cryomilling is the creation of a homogeneous distribution of ultrafine (nanoscale) Al-rich oxide/nitride dispersoids, which remain thermally stable even after exposure at 1100°C for 100 h. The TEM study on the as-cryomilled powder, prior to the HVOF spraying, indicates that some Al and Y-rich oxides are already present within the material as a direct result of the cryomilling process. 相似文献
253.
The effects of irradiation with electrons having energies in the range 0.7–1.7 MeV on the dark conductivity and the network of hydrogenated amorphous silicon (a-Si:H) thin films have been studied. The dark conductivity measurements show that electron irradiation leads to a degradation in the dark conductivity, with the degradation being greater at lower electron energies. The Raman results suggest that the irradiation induces structural defects in the a-Si:H films, with the lower energy electrons producing more disorder in the amorphous network. 相似文献
254.
This article proposes a factor, the critical electronegativity difference Δx cri, to correlate alloy composition with thermal stability and glass-forming ability of Al–Ni–RE (RE: Rare Earth element) ternary metallic glasses. The Al-rich metallic glasses with Δx > Δx cri exhibit glassy behavior, whereas alloys with Δx < Δx cri are nanocrystalline. Nanoglassy alloys occur when Δx ≈ Δx cri. The best glass formers are located near Δx cri. Furthermore, an equation has been deduced to calculate Δx cri with varying RE covalent atomic radius. 相似文献
255.
In this article, we propose an efficient atomic packing cluster-based composition protocol to help design Al-based metallic glasses. Its validity is verified by some typical experimental data from the literatures. Furthermore, with this understanding, the Al–Ni–Y alloy system is re-evaluated. As a result, the best glass former Al86Ni9Y5 in this system, with the critical thickness of about 500 µm, is successfully fabricated by wedge casting. 相似文献
256.
Solubility criterion for sequential disordering in metal-metal multilayers upon solid-state reaction
An n-body Ni-Ti potential is derived and applied in a molecular dynamics simulation to study the maximum supersaturated solubility of the terminal solid solutions and solid-state reaction in a Ni/Ti bilayer. It reveals that during interfacial reaction of the Ni/Ti bilayer the Ti lattice reaches its maximum solubility by dissolving Ni earlier than Ni does through dissolution of Ti, which results in a sequential disordering of first Ti and then Ni, although Ti has a higher melting point than Ni. In the Ni-Zr, Ni-Mo and Ni-Ta systems, however, the Ni lattice collapses more rapidly because it reaches a maximum solubility earlier than its partners, which have higher melting points than Ni. A solubility criterion is thus relevant for all the above cases; the lower the maximum solid solubility the less stable is the lattice of the metal upon solid-state reaction. 相似文献
257.
J.J. Wang S. Bhattacharyya Q. Li T.W. Heo X.Q. Ma Long-Qing Chen 《Philosophical Magazine Letters》2013,93(7):327-335
An efficient numerical algorithm is proposed to accurately compute the elastic fields in two-dimensional (2D) or three-dimensional (3D) microstructures with arbitrary elastic inhomogeneity and anisotropy. It combines the equivalent inclusion method of Eshelby, the microelasticity theory of Khachaturyan, and the spectral iterative perturbation method of Hu and Chen. Its efficiency is compared with those of existing approaches in the literature. The method can be conveniently implemented in phase-field modeling of stress-dependent microstructure evolution and/or of mass/electrical transport. 相似文献
258.
259.
ResumenEn este trabajo, que conjuga la tradición psicométrica con la perspectiva de procesamiento de información, se estudió si las diferencias en rendimiento observadas en los tests están asociados a diferencias individuales en gasto atencional. Fueron seleccionados 4 grupos extremos de sujetos en función de dos factores de inteligencia (verbal y espacial), los cuales realizaron una tarea de verificación de frases (tarea primaria) aisladamente o en conjunción con una de emparejamiento perceptivo (tarea secundaria). Se utilizaron como variables dependientes el número de aciertos de la tarea primaria, en ambas condiciones, y en la tarea secundaria, con tiempo limitado; y el número de errores en ambas tareas, sin límite de tiempo. Los sujetos altos verbales tuvieron más aciertos que los bajos verbales al ejecutar la tarea primaria en solitario, e iguales diferencias se encontraron entre altos y bajos espaciales; no se observaron diferencias en el número de errores. Al realizar ambas tareas concurrentemente, los altos verbales tienen mayor número de aciertos y cometen menos errores, en la tarea primaria, que los bajos verbales; los altos y bajos espaciales se diferencian únicamente en el número de aciertos. Estos resultados son discutidos y comparados con estudios diferenciales recientes. 相似文献
260.
ABSTRACTSelf-referential processing has been proven to be effective in improving source memory. However, it is unclear whether different types of source information would be consistently enhanced when an item is self-referentially processed. In two experiments, the authors examined the influence of the self (compared with other-referencing and semantic processing) as well as learning intention (incidental/intentional learning) on memory for two types of source information (spatial location and colour) that differ in the amount of cognitive resources they require to be encoded in memory. Results show that self-referencing has enhanced memory for spatial location of words whatever this information is learned intentionally or incidentally, whereas it cannot facilitate memory for the colour of words under the intentional learning condition, nor can it under the incidental condition. These findings suggest that self-referential processing is beneficial in memory improvement but not all-powerful, a source self-reference effect is subject to source information type. 相似文献