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排序方式: 共有114条查询结果,搜索用时 15 毫秒
91.
Soheila Zamanlui Matin Mahmoudifard Masoud Soleimani Behnaz Bakhshandeh Mohammad Vasei 《国际聚合物材料杂志》2018,67(1):50-60
The simultaneous effect of electrospun scaffold alignment and polymer composition on chondrogenic differentiation of human bone marrow mesenchymal stem cells (hBMMSC) is investigated. Aligned and randomly oriented polycaprolactone/poly(lactic-co-glycolic acid) (PLGA) hybrid electrospun scaffolds with two different ratios are fabricated by electrospinning. It is found that aligned nanofibrous scaffolds support higher chondrogenic differentiation of hBMMSCs compared to random ones. The aligned scaffolds show a higher expression level of chondrogenic markers such as type II collagen and aggrecan. It is concluded that the aligned nanofibrous scaffold with higher PLGA ratio could significantly enhance hBMMSC proliferation and differentiation to chondrocytes. 相似文献
92.
Amir Hossein Gandomi Amir Hossein Alavi Abazar Asghari Hadi Niroomand Ali Matin Nazar 《Neural computing & applications》2014,24(6):1285-1291
This paper presents a new nonlinear model for the prediction of hysteretic energy demand in steel moment resisting frames using an innovative genetic-based simulated annealing method called GSA. The hysteretic energy demand was formulated in terms of several effective parameters such as earthquake intensity, number of stories, soil type, period, strength index, and energy imparted to the structure. The performance and validity of the model were further tested using several criteria. The proposed model provides very high correlation coefficient (R = 0.985), and low root mean absolute error (RMSE = 1,346.1) and mean squared error (MAE = 1,037.6) values. The obtained results indicate that GSA is an effective method for the estimation of the hysteretic energy. The proposed GSA-based model is valuable for routine design practice. The prediction performance of the optimal GSA model was found to be better than that of the existing models. 相似文献
93.
Solar photovoltaics (PVs) have nonlinear voltage–current characteristics, with a distinct maximum power point (MPP) depending on factors such as solar irradiance and operating temperature. To extract maximum power from the PV array at any environmental condition, DC–DC converters are usually used as MPP trackers. This paper presents the performance analysis of a coupled inductor single-ended primary inductance converter for maximum power point tracking (MPPT) in a PV system. A detailed model of the system has been designed and developed in MATLAB/Simulink. The performance evaluation has been conducted on the basis of stability, current ripple reduction and efficiency at different operating conditions. Simulation results show considerable ripple reduction in the input and output currents of the converter. Both the MPPT and converter efficiencies are significantly improved. The obtained simulation results validate the effectiveness and suitability of the converter model in MPPT and show reasonable agreement with the theoretical analysis. 相似文献
94.
The feasibility of using solid acrylonitrile–butadiene rubbers (NBR) with 19 and 33% w/w acrylonitrile to toughen diglycidyl ether of bisphenol A (DGEBA) epoxy resins has been investigated. Thermal analysis experiments revealed a two‐phase morphology of these rubber‐modified epoxies. However, the higher content of acrylonitrile in the rubber caused better compatibility between NBR and the epoxy resin. The rubber with 33% acrylonitrile was found to be an effective toughening agent for DGEBA epoxy resins. Fracture surface studies and also the high tensile strength of crosslinked high molecular weight NBR suggest that the toughening effect should arise from rubber bridging and tearing mechanisms. © 2000 Society of Chemical Industry 相似文献
95.
Matin Parchei Esfahani Robert Gracie 《International journal for numerical methods in engineering》2019,118(12):741-763
The simulation of hydraulic fracturing (HF) involves the solution of a hydro-mechanically coupled system. This article presents a new iterative sequential coupling algorithm, the undrained HF split, that improves the simulation of HFs in impermeable media. A poromechanics analogy is used to derive a stable split for the hydro-mechanically coupled system in which the mechanical subproblem is solved first. The proposed undrained HF split is applied to the simulation of cohesive HFs in an impermeable elastic medium. The cubic law is used as the constitutive model for simulating fluid flow in fractures. A minimum hydraulic aperture is assumed in the cohesive tip zone, where the mechanical aperture smoothly vanishes. While general in its nature, the undrained HF splitting scheme is employed within the context of a two-dimensional eXtended finite element model for the fractured solid, and a regular finite element model for fluid in the fracture. The undrained HF split is successfully used to simulate self-similar plane strain HFs as well as the propagation of HFs from a wellbore under anisotropic stress conditions. Fracture trajectories and local alteration of stress field are investigated. The solution of the undrained HF split converges to the same solution as the fully coupled model, whereas the commonly used P→W sequential algorithm, referred to in this article as the drained HF split, generates spurious oscillations and fails to converge in many problems. The undrained HF split is shown to be stable and robust in applications where the drained HF split is unstable. 相似文献
96.
97.
M. A. Matin T. M. Benson P. C. Kendall M. S. Stern 《International Journal of Numerical Modelling》1994,7(1):25-33
The method of effective penetration depth is used to produce a novel scalar or polarized finite difference approach for the solution of optical rib waveguide field problems. The new method is quicker than previous finite difference approaches and requires less computer memory. Propagation constant values are presented for a range of semiconductor rib waveguides and are found to be indistinguishable from benchmark results produced using earlier methods of analysis. A simple polarization correction formula recently derived is confirmed by utilizing the good accuracy of these results. This enables discussion of the relationship between quasi-TE, quasi-TM and scalar modes, and a further substantial reduction of the cpu time. 相似文献
98.
Seyed Sajad Mirjavadi Abdolhamid Matin Samira Rabby Behzad Mohasel Afshari 《热应力杂志》2017,40(10):1201-1214
This article presents a study on the thermal buckling behavior of two-dimensional functionally graded microbeams made of porous materials. The material composition varies along thickness and length of the microbeam based on the power law distribution. The microbeam is modeled within the framework of Euler–Bernoulli beam theory. The microbeam is considered having variable material composition along thickness. The equations are derived using the modified couple stress theory and the solving process is based on the generalized differential quadrature method. The validity of the results is shown through comparison of the results with the results of other published research. 相似文献
99.
Mohammed Mahbubul Matin Amit R. Nath Omar Saad Mohammad M. H. Bhuiyan Farkaad A. Kadir Sharifah Bee Abd Hamid Abeer A. Alhadi Md. Eaqub Ali Wageeh A. Yehye 《International journal of molecular sciences》2016,17(9)
Benzyl α-l-rhamnopyranoside 4, obtained by both conventional and microwave assisted glycosidation techniques, was subjected to 2,3-O-isopropylidene protection to yield compound 5 which on benzoylation and subsequent deprotection of isopropylidene group gave the desired 4-O-benzoylrhamnopyranoside 7 in reasonable yield. Di-O-acetyl derivative of benzoate 7 was prepared to get newer rhamnopyranoside. The structure activity relationship (SAR) of the designed compounds was performed along with the prediction of activity spectra for substances (PASS) training set. Experimental studies based on antimicrobial activities verified the predictions obtained by the PASS software. Protected rhamnopyranosides 5 and 6 exhibited slight distortion from regular 1C4 conformation, probably due to the fusion of pyranose and isopropylidene ring. Synthesized rhamnopyranosides 4–8 were employed as test chemicals for in vitro antimicrobial evaluation against eight human pathogenic bacteria and two fungi. Antimicrobial and SAR study showed that the rhamnopyranosides were prone against fungal organisms as compared to that of the bacterial pathogens. Interestingly, PASS prediction of the rhamnopyranoside derivatives 4–8 were 0.49 < Pa < 0.60 (where Pa is probability ‘to be active’) as antibacterial and 0.65 < Pa < 0.73 as antifungal activities, which showed significant agreement with experimental data, suggesting rhamnopyranoside derivatives 4–8 were more active against pathogenic fungi as compared to human pathogenic bacteria thus, there is a more than 50% chance that the rhamnopyranoside derivative structures 4–8 have not been reported with antimicrobial activity, making it a possible valuable lead compound. 相似文献
100.
Houwen Tang M. A. Matin Heli Wang Mowafak Al-Jassim John Turner Yanfa Yan 《Journal of Electronic Materials》2012,41(11):3100-3106
We have synthesized pure and Mg-alloyed hematite thin films on F-doped, SnO2-coated glass substrates by radiofrequency magnetron cosputtering of iron oxide with and without MgO sources in mixed Ar/O2 and mixed N2/O2 ambient. We found that hematite films deposited in N2/O2 ambient exhibited much poorer crystallinity than those deposited in Ar/O2 ambient. We determined that Mg alloying led to increased crystallinity and bandgap. Furthermore, we found that Mg alloying inverted the type of conductivity of the thin films: pure hematite thin films exhibited n-type conductivity, whereas Mg-alloyed hematite thin films exhibited p-type conductivity. 相似文献