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排序方式: 共有235条查询结果,搜索用时 31 毫秒
11.
Fei Gao Ram Devanathan Takuji Oda William J. Weber 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2006,250(1-2):50-53
Partial-charged potentials for GaN are systematically developed that describe a wide range of structural properties, where the reference data for fitting the potential parameters are taken from ab initial calculations or experiments. The present potential model provides a good fit to different structural geometries and high pressure phases of GaN. The high-pressure transition from wurtzite to rock-salt structure is correctly predicted yielding the phase transition pressure of about 55 GPa, and the calculated volume change at the transition is in good agreement with experimental data. The results are compared with those obtained by ab initio simulations. 相似文献
12.
Schoeffler has derived continuously equivalent networks in the nodal-admittance domain. The letter derives a corresponding result in state space that combines the usefulness of Schoeffler's result and the power of the state-variable approach. 相似文献
13.
Perumal Siddhuraju Klaus Becker 《Journal of the science of food and agriculture》2003,83(14):1517-1524
The antioxidant activities of a methanolic extract of mucuna beans (Mucuna pruriens var utilis) and several non‐protein amino/imino acids, namely L ‐3,4‐dihydroxyphenylalanine (L ‐dopa), L ‐3‐carboxy‐6,7‐dihydroxy‐1,2,3,4‐tetrahydroisoquinoline (compound I), (?)‐1‐methyl‐3‐carboxy‐6,7‐dihydroxy‐1,2,3,4‐tetrahydroisoquinoline (compound II) and 5‐hydroxytryptophan (5‐HTP), were evaluated. By virtue of their hydrogen‐donating ability, all the tested compounds and the mucuna seed extract showed excellent reducing power, with the highest values being recorded for L ‐dopa in a dose‐dependent manner. Similarly, as compared with synthetic antioxidants (BHT and BHA) and quercetin, all the tested compounds and the seed extract were found to be more potent in free radical‐scavenging activity (P < 0.05) against α,α‐diphenyl‐β‐picrylhydrazyl (DPPH?) radicals. Hydroxyl radicals (OH?) and superoxide anion radicals (O2??) were effectively scavenged by the tested compounds, with the exception that no scavenging activity of 5‐HTP was observed on (O2??) up to a concentration of 2 mg ml?1, as was also the case for BHA. Among the tested non‐protein amino/imino acids and seed extract the highest peroxidation‐inhibiting activity (95%) was recorded for 5‐HTP. On the other hand, in the linoleic acid/β‐carotene‐bleaching system, L ‐dopa, compound I and compound II acted as pro‐oxidants, whereas the seed extract showed only weak antioxidant activity as in the linoleic acid emulsion system. Copyright © 2003 Society of Chemical Industry 相似文献
14.
Muthupandi Nagaraj Devanathan Perumal Muthusamy Boominathan Nattamai Bhuvanesh 《Journal of Sulfur Chemistry》2014,35(1):24-30
The attempted selenium dioxide oxidation of substituted diphenacyl sulfides in anticipation of further functionalization led to a series of α -ketoacids 3 via oxidation followed by C?S bond cleavage. Two minor products, 5 and 6, have also been isolated and a mechanistic pathway for the formation of 3, 5 and 6 has been proposed. 相似文献
15.
16.
Summary The structure of time dependent jets in rotating fluid using similarity transformations is studied theoretically for which exact solutions are discussed. Approximate solution using a modified von Mises transformation is also explored.With 4 FiguresPresent address: Department of Applied Mathematics. 相似文献
17.
Structure‐Guided Design of Thiazolidine Derivatives as Mycobacterium tuberculosis Pantothenate Synthetase Inhibitors 下载免费PDF全文
Parthiban Brindha Devi Ganesh Samala Jonnalagadda Padma Sridevi Shalini Saxena Mallika Alvala Elena G. Salina Prof. Dharmarajan Sriram Prof. Perumal Yogeeswari 《ChemMedChem》2014,9(11):2538-2547
The pantothenate biosynthetic pathway is essential for the persistent growth and virulence of Mycobacterium tuberculosis (Mtb) and one of the enzymes in the pathway, pantothenate synthetase (PS, EC: 6.3.2.1), encoded by the panC gene, has become an appropriate target for new therapeutics to treat tuberculosis. Herein, we report nanomolar thiazolidine inhibitors of Mtb PS developed by a rational inhibitor design approach. The thiazolidine compounds were discovered by using energy‐based pharmacophore modelling and subsequent in vitro screening, which resulted in compounds with a half maximal inhibitory concentration (IC50) value of (1.12±0.12) μM . These compounds were subsequently optimised by a combination of modelling and synthetic chemistry. Hit expansion of the lead by chemical synthesis led to an improved inhibitor with an IC50 value of 350 nM and an Mtb minimum inhibitory concentration (MIC) of 1.55 μM . Some of these compounds also showed good activity against dormant Mtb cells. 相似文献
18.
F. Gao W. J. Weber R. Devanathan 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2001,180(1-4):176-186
Molecular dynamics (MD) methods with a modified Tersoff potential have been used to simulate Si displacement cascades with energies up to 50 keV and to compare clustering behavior for Si and Au recoils in β-SiC (3C). The results show that the lifetime of the thermal spike is very short compared to that in metals, and that the surviving defects are dominated by C interstitials and vacancies for Si displacement cascades. Only 19% of the interstitial population is contained in clusters, with the largest cluster containing only four interstitial atoms for energetic Si recoils. The energy dependence of stable defect formation exhibits a power-law relationship. The high energy Si recoil generates multiple sub-cascades and forms dispersed defect configurations. These results suggest that in-cascade amorphization in SiC does not occur with any high degree of probability during the lifetime of Si cascades. On the other hand, large disordered domains are created in the cascades produced by 10 keV Au recoils. Structure analysis indicates that these highly disordered regions have amorphous characteristics. The data for the cluster spectra have been used to calculate the relative cross-sections for in-cascade amorphization (or clustering) and defect-stimulated amorphization. The ratios of these cross-sections for Si and Au are in excellent agreement with those derived from a fit of the direct-impact/defect-stimulated model to experimental data. 相似文献
19.
Analysis of Operation of a Self-Excited Induction Generator With Generalized Impedance Controller 总被引:1,自引:0,他引:1
In this paper, analysis of the operation of a stand-alone self-excited induction generator (SEIG) with generalized impedance controller (GIC) (voltage source pulsewidth-modulated bidirectional inverter with dc link battery) has been discussed. Model of the SEIG along with the generalized impedance controller, has been developed in MATLAB/Simulink environment. The simulation results obtained for steady-state operation of the system, following speed and load perturbations have been presented here. The simulation results are validated with the experimental ones, which are conducted on a laboratory prototype of the SEIG-GIC system. The generalized impedance controller is found to be capable of maintaining the frequency of the SEIG constant under open-loop condition, following the speed and load perturbations. 相似文献
20.
This paper presents a temporal logic formulation of discrete event control which forms a new theoretical basis for control analysis and synthesis of a class of discrete event systems (DES). Based on the formulation, a basic supervisory control theory is developed for a control objective specified by an invariance formula belonging to the safety canonical class of Manna and Pneuli. Using the safety canonical class as a basis, the refinement and generalization of the existing basic predicate framework are demonstrated. A simple example illustrates the formal axiomatic means to perform control-theoretic analysis and synthesis under the new formulation. 相似文献