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701.
Xiaotan Yuan Tao Zhou Weili Ren Jianchao Peng Tianxiang Zheng Long Hou Jianbo Yu Zhongming Ren Peter K.Liaw Yunbo Zhong 《材料科学技术学报》2021,62(3):52-59
The mechanical-property improvement of directionally-solidified Nickel-based single crystal(SC)superalloy with the single-direction magnetic fields is limited by their destructiveness on the dendritic microstructure.Here,the work present breaks through the bottleneck.It shows that the application of the cusp magnetic field(CMF)ensures that the dendrites are not destroyed.This feature embodies that the primary dendrite trunks arrange regularly and orderly,as well the secondary dendrite arms grow symmetrically.By contrast,both the unidirectional transverse and longitudinal magnetic field destroy the dendrite morphology,and there are a number of stray grains near the totally-re melted interface.The nondestructive effect is achieved mainly by the combined action of the thermoelectromagnetic force on the dendrites and thermoelectromagnetic convection in the melt during directional solidification.The investigation should contribute a new route for dramatically and effectively improving the crystal quality and mechanical properties of the directionally-solidified alloys. 相似文献
702.
Microstructural Control of Ti-Al-Nb-W-B Alloys 总被引:1,自引:0,他引:1
In this work, new TiAl alloys containing W, B, and Nb have been developed. Fine uniform microstructures, with colony size
smaller than 50 μm, can be conveniently obtained after hot-isostatic pressing (HIP) and homogenization treatment without any grain-refining
processes using hot deformation. The effects of tungsten and boron on the microstructure of the TiAl alloys, including the
colony size and lamellar spacing, were analyzed. This work shows that a small additional amount of W can refine the grain
size of the Ti-Al-Nb-W-B alloys. The lamellar spacing also decreases with increasing W concentration. When the amount of W
is greater than 0.4 at. pct, the β phase is stabilized and remains at room temperature, which can degrade the ductility of the alloy. Mechanical properties,
such as the hardness of the alloy, can be increased by the addition of the alloying element through the solution strengthening
and refinement of the grain size.
This article is based on a presentation given in the symposium entitled “Deformation and Fracture from Nano to Macro: A Symposium
Honoring W.W. Gerberich’s 70th Birthday,” which occurred during the TMS Annual Meeting, March 12-16, 2006 in San Antonio,
Texas and was sponsored by the Mechanical Behavior of Materials and Nanomechanical Behavior Committees of TMS. 相似文献
703.
Z.H. Nie Y.D. Wang G.Y. Wang J.W. Richardson G. Wang Y.D. Liu P.K. Liaw L. Zuo 《Metallurgical and Materials Transactions A》2008,39(13):3113-3119
The phase transition and influence of the applied stress on the texture evolution in the as-cast Ni-Mn-Ga ferromagnetic shape-memory
alloys were studied by the time-of-flight (TOF) neutron diffraction technique. The neutron diffraction experiments were performed
on the General Purpose Powder Diffractometer (Argonne National Laboratory). Inverse pole figures were determined from the
neutron data for characterizing the orientation distributions and variant selections of polycrystalline Ni-Mn-Ga alloys subjected
to different uniaxial compression deformations. Texture analyses reveal that the initial texture for the parent phase in the
as-cast specimen was composed of
, , , and , which was weakened after the compression deformation. Moreover, a strong preferred selection of martensitic-twin variants
(and ) was observed in the transformed martensite after a compression stress applied on the parent phase along the cyclindrical
axis of the specimens. The preferred selection of variants can be well explained by considering the grain/variant-orientation-dependent
Bain-distortion energy.
This article is based on a presentation given in the symposium entitled “Neutron and X-Ray Studies for Probing Materials Behavior,”
which occurred during the TMS Spring Meeting in New Orleans, LA, March 9–13, 2008, under the auspices of the National Science
Foundation, TMS, the TMS Structural Materials Division, and the TMS Advanced Characterization, Testing, and Simulation Committee. 相似文献
704.
William Yi Wang Jun Wang Deye Lin Chengxiong Zou Yidong Wu Yongjie Hu Shun-Li Shang Kristopher A. Darling Yiguang Wang Xidong Hui Jinshan Li Laszlo J. Kecskes Peter K. Liaw Zi-Kui Liu 《Journal of Phase Equilibria and Diffusion》2017,38(4):404-415
Attributing to the attractive mechanical properties, e.g., high yield strength and fracture toughness, the atomic and electronic basis for high entropy alloys (HEAs) are under extensive studies. In the present work, the local atomic arrangement of body-centered-cubic (BCC) equiatomic HEAs are revealed by the CN14 cluster-plus-glue-atom model and the 32 atoms special quasirandom structures. Moreover, the cluster-plus-glue-atom model is utilized to generate ordered and disordered configurations. The bonding lengths among the same and different alloying elements are comprehensively compared in term of their partial pair correlation function (PCF). According to the specific (well-defined) position of each partial PCF of the BCC structure, the order–disorder/random configurational transitions are revealed by the absence of partial PCF peaks. Here, the WMoTM1TM2 (TM = Ta, Nb, and V) BCC equiatomic refractory HEAs are selected as a case study. Through mixing various groups of alloying elements, the atomic-size differences not only result in the lattice mismatch/distortion but also yield the formation of weak spots. Their bonding-charge density captures the electron redistributions caused by the coupling effect of the lattice distortion and valance electron differences among various elements, which also presents the physical nature of the loosely-bonded weak spots and the tightly-bonded clusters. It is worth mentioning that both the PCF and the negative enthalpy of mixing can be utilized to characterize the clusters or the short range ordering in the HEAs. The microstates revealed by the cluster-plus-glue-atom model are in line with the novel small set of the ordered structures method reported in the literature. 相似文献
705.
This article reviews the basic techniques employed in fatigue life prediction. The stress-life, local-strain, and fracture-mechanics methods as applied to life prediction under constant amplitude loading and variable amplitude loading are discussed. Life prediction methodology under variable maplitude loading is also discussed, with particular emphasis on the linear-damage accumulation approach, or Miner's rule. Finally, a discussion of various cycle-counting techniques for variable amplitude loading is given. 相似文献
706.
T. McKechnie P. Krotz Y. K. Liaw R. M. Poortnan F. Zimmerman R. Holmes 《Journal of Thermal Spray Technology》1995,4(2):143-144
707.
Microdata from the 1987 National Population Survey are used to analyze internal migration in China in the 1980s. The focus is on the impact of migration policies on rural-urban migration. "There are two main findings. First, although the migration policy resulted in a very low migration level and systematic distortions in migration schedules, its encouragement of downward migrations was very ineffective, whereas its control on rural-to-urban migrations was partially weakened by the strong upward aspirations of rural families awakened by recent economic reform. Consequently, net in-migration contributed substantially to the growth both of city and of town populations. Second, although the level of education had a strong positive effect on the migration propensities both of males and of females in general, it had a strong negative effect on the migration propensities of females at the time of marriage, a finding which suggests that the families at subsistence income level tended to marry their daughters to grooms in other communities in order to reduce the risk of familial income shortfalls." 相似文献
708.
Novel optically transparent, low dielectric and highly organosoluble alicyclic polyamides derived from bulky alicyclic diamine containing trifluoromethyl group on either side, 1,1-bis[4-(2-trifluoromethyl-4-aminophenoxy)phenyl]-4-tert-butylcyclohexane (BTFAPBC), were prepared. The polyamides were obtained in almost quantitative yields and showed inherent viscosity values between 0.55 and 0.72 dL g−1 in DMAc solution. Most of the polyamides showed excellent solubility in polar solvents such as N-methyl-2-pyrrolidinone (NMP), N,N′-dimethyl acetamide (DMAc), N,N′-dimethyl formamide (DMF), pyridine, cyclohexanone, γ-butyrolactone and chloroform. The cut-off wavelength for polyamides ranged from 350 to 388 nm. Polyamides with alicyclic tert-butylcyclohexyl cardo and trifluoromethyl substituents exhibited low dielectric constants ranging from 3.29 to 3.98 (at 100 Hz) compared with commercially available polyamides [Amodel®, 4.2-5.7 at 100 Hz]. Polyamides showed glass transition temperatures in the range of 244-266 °C and possessed a coefficient of thermal expansion (CTE) of 60-75 ppm °C−1. Thermogravimetric analysis data showed that the polyamides were stable up to 430 °C and the 10% weight loss temperature was found to be in the range of 437-466 °C in nitrogen atmosphere. The polyamide films had a tensile strength in the range of 66-103 MPa, elongation at break in the range of 5-8%, and tensile modulus in the range of 1.5-2.2 GPa. Due to their properties, the polyamides could be considered as engineering plastic and photoelectric materials. 相似文献
709.
Journal rankings and journal ratings are important to governments, research institutes, and scientific research in general, and they frequently serve as the criteria for evaluating research performance to determine whether specific researchers will receive promotions and/or earn research grants. However, the only widely adopted journal assessment method is known as impact factor (IF), which focuses on citations in academic journals. However, IF disregards the technological applications and value of academic journals. In this article, we propose a method to rank academic journals that utilizes non-patent references in patent documents. We also compare the differences between journal rankings derived by using IF with those derived from the Intellectual Property Citation Index (IPCI) across different fields; moreover, some fields contain positive and significant correlations between IF and the IPCI. The results of this study offer a new perspective from which to assess the technological value of academic journals, particularly those in the technological and scientific fields. This study considers linkages among science and technology and the needs of the stakeholders in journal assessment to shed light on journal assessment and journal ranking methods. 相似文献
710.
This paper proposes a methodology and approach to understand battery performance and life through driving cycle and duty cycle analyses from electric and hybrid vehicle (EHV) operation in real-world situations. Conducting driving cycle analysis with trip data collected from EHV operation in real life is very difficult and challenging. In fact, no comprehensive approach has been accepted to date, except those using standard driving cycles on a dynamometer or a track. Similarly, analyzing duty cycle performance of a battery under real-life operation faces the same challenge. A successful driving cycle analysis, however, can significantly enhance our understanding of EHV performance in real-life driving. Likewise, we also expect similar results through duty cycle analysis for batteries. Since 1995, we have been developing tools to analyze EHV and power source performance. In particular, we were able to collect data from a fleet of 15 Hyundai Santa Fe electric sports utility vehicles (e-SUVs) operated on Oahu, Hawaii; from July 2001 to June 2003 to allow driving and duty cycle analyses in order to understand battery pack performance from a variety of EHV operating conditions. We thus developed a comprehensive approach that comprises fuzzy logic pattern recognition (FL-PR) techniques to perform driving and duty cycle analyses. This approach has been successfully applied to EHV performance analysis via the creation of a compositional driving profile called “driving cycle profile” (DrCP) for each trip. The same approach was used to analyze battery performance via the construction of “duty cycle profile” (DuCP) to express battery usage under various operating conditions. The combination of the two analyses enables us to understand both the usage profile of EHV and battery performance in synergetic details and in a systematic manner using a pattern recognition technique. 相似文献