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排序方式: 共有467条查询结果,搜索用时 15 毫秒
51.
Ghasem Yousefi Shima Yousefi Zahra Emam‐Djomeh 《International Journal of Food Science & Technology》2013,48(6):1179-1186
The effects of conventional (CV) and microwave (MW) heating on total soluble solid (TSS) content, total anthocyanin content (TAC), total phenolic content (TPC) and antioxidant activity of raspberry juice obtained from two cultivars of Amol (AM) and Siyahkal (SK) were scrutinised. Antioxidant activity of the juices was measured by 2,2 diphenyl‐1‐picrylhydrazyl (DPPH) radical scavenging capacity and expressed as EC50 value. In the both methods, the concentration rate constant for the juices was significantly decreased by increasing operational pressure from 12 to 100 kPa (P < 0.05). A first‐order reaction kinetic model was successfully fitted for the degradation of monomeric anthocyanins at all operating pressures. The results also showed that thermal treatment of MW compared CV in both SK and AM cultivars caused a lower decrease in the TAC, TPC and antioxidant activity. Moreover, the changes in trend of the antioxidant activities due to the thermal treatment were positively correlated with the TPC (r = 0.74, P < 0.05) and TAC (r = 0.61, P < 0.05). 相似文献
52.
53.
Farzad Bahrami Ghasem Moslehi 《The International Journal of Advanced Manufacturing Technology》2013,64(1-4):497-511
This paper aims to determine simultaneously the amount, timing, and location of progress payments in projects in order to achieve a set of equitable solutions in the client–contractor negotiation process. The objective function tries to minimize the distance between the final solutions and the best achievable solutions of the client and the contractor. Due to combinatorial nature of the proposed problem, an iterative two-stage search method is proposed. In the first stage, a set of payments is determined to maximize the contractor's net present value (NPV), another set to maximize the client's NPV, and another one to minimize the objective function. In the second stage, activities are rescheduled to improve the solutions by fixing the amount and location of progress payments. A hybrid meta-heuristic algorithm named GASA, along with a simulated annealing (SA) and a genetic algorithm (GA), is introduced for the first stage, while the activities are optimally scheduled in the second stage. It has been shown that SA is better for the contractor’s objective function and GA for the client’s objective function, but GASA is the best in all situations; besides, the proposed method has represented to be an efficient approach to obtain non-dominated solutions in the client–contractor negotiation process. 相似文献
54.
End plate is one of the main components of the proton exchange membrane (PEM) fuel cells. The major role of the end plate is providing uniform pressure distribution between various components of the fuel cell (bipolar plates, etc.) and consequently reducing contact resistance between them. In this study a procedure for design of end plate has been developed. At first a suitable material was selected using various criteria. Then a finite element (FE) analysis was accomplished to analyze end plate deflections and get its optimized thickness. After fabricating the end plates, a single cell was assembled and electrochemical impedance spectroscopy (EIS) tests were carried out to ensure their good operation. A 5 kW fuel cell assembled with these end plates was tested at different operating conditions. The test results show an appropriate assembly pressure distribution inside the stack which indicates good performance of the designed end plates. 相似文献
55.
Pouya Sirous Rezaei Ghasem Najafpour Darzi Hoda Shafaghat 《Korean Journal of Chemical Engineering》2010,27(3):919-924
A high performance thermostable α-amylase at low pH values has been synthesized. Sugarcane bagasse was hydrolyzed in a dilute acid solution and utilized as
carbon source for the growth of Aspergillus niger strain NCIM 548. Glucose, xylose and arabinose with the ratio of 1.0: 0.9: 0.3 (w/w/w) were detected in the hydrolyzate by
HPLC analysis. Optimization of the fermentation conditions for α-amylase production was performed by varying four influential parameters such as Sugarcane bagasse hydrolyzate (SBH), NH4Cl, pH and incubation time using a central composite design (CCD) under response surface methodology (RSM). The optimum values
of SBH, NH4Cl, pH and incubation time were 20.49, 2.34 g/l, 5.65 and 76.67 h, respectively. The acido-thermophilic enzyme showed maximum stability at 70°C and pH value of 4. The rate
constant, K
m
and maximum reaction rate, V
max
were 18.79 g/l and 15.85 g/l·min, respectively. 相似文献
56.
57.
Ashkan Heidarkhan Tehrani Ali Zadhoush Saeed Karbasi Saied Nouri Khorasani 《应用聚合物科学杂志》2010,118(5):2682-2689
We sought to determine the impact of electrospinning parameters on a trustworthy criterion that could evidently improve the maximum applicability of fibrous scaffolds for tissue regeneration. We used an image analysis technique to elucidate the web permeability index (WPI) by modeling the formation of electrospun scaffolds. Poly(3‐hydroxybutyrate) (P3HB) scaffolds were fabricated according to predetermined conditions of levels in a Taguchi orthogonal design. The material parameters were the polymer concentration, conductivity, and volatility of the solution. The processing parameters were the applied voltage and nozzle‐to‐collector distance. With a law to monitor the WPI values when the polymer concentration or the applied voltage was increased, the pore interconnectivity was decreased. The quality of the jet instability altered the pore numbers, areas, and other structural characteristics, all of which determined the scaffold porosity and aperture interconnectivity. An initial drastic increase was observed in the WPI values because of the chain entanglement phenomenon above a 6 wt % P3HB content. Although the solution mixture significantly (p < 0.05) changed the scaffold architectural characteristics as a function of the solution viscosity and surface tension, it had a minor impact on the WPI values. The solution mixture gained the third place of significance, and the distance was approved as the least important factor. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
58.
Mohammad Ali Takassi Ghasem Zargar Mohammad Madani Amin Zadehnazari 《Petroleum Science and Technology》2017,35(4):385-391
Most of the synthetic surfactants investigated with the aim of enhanced chemically oil recovery in the literature have environmental drawbacks. In this work, application of an environmentally-friendly synthetic surfactant as an enhanced oil recovery agent is introduced by measuring interfacial tension of water–kerosene systems and wettability alteration of carbonate pellets. For this purpose, an amino acid-based surfactant was initially synthesized using a new synthetic approach which was subsequently confirmed by spectra of Fourier transform infrared and Proton nuclear magnetic resonance. Results showed a value of critical micelle concentration in the range of 9000–9100 ppm for this surfactant. Results also demonstrated a decrease of 38.53% in water–kerosene system interfacial tension and a 17.76% reduction in oil-wetness of the carbonate pellets. 相似文献
59.
Mohammad Madani Peyman Abbasi Ghasem Zargar Pezhman Abbasi 《Petroleum Science and Technology》2017,35(23):2179-2186
Development of reliable and accurate models to estimate carbon dioxide–brine interfacial tension (IFT) is necessary, since its experimental measurement is time-consuming and requires expensive experimental apparatus as well as complicated interpretation procedure. In the current study, feed forward artificial neural network is used for estimation of CO2–brine IFT based on data from published literature which consists of a number of carbon dioxide–brine interfacial tension data covering broad ranges of temperature, total salinity, mole fractions of impure components and pressure. Trial-and-error method is utilized to optimize the artificial neural network topology in order to enhance its capability of generalization. The results showed that there is good agreement between experimental values and modeling results. Comparison of the empirical correlations with the proposed model suggests that the current model can predict the CO2–brine IFT more accurately and robustly. 相似文献
60.
Impact of a Stereocentre Inversion in Cyclic Lipodepsipeptides from the Viscosin Group: A Comparative Study of the Viscosinamide and Pseudodesmin Conformation and Self‐Assembly
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Niels Geudens Matthias De Vleeschouwer Dr. Krisztina Fehér Dr. Hassan Rokni‐Zadeh Dr. Maarten G. K. Ghequire Prof. Dr. Annemieke Madder Prof. Dr. René De Mot Prof. Dr. José C. Martins Dr. Davy Sinnaeve 《Chembiochem : a European journal of chemical biology》2014,15(18):2736-2746
The viscosin group covers a series of cyclic lipodepsipeptides (CLPs) produced by Pseudomonas bacteria, with a range of biological functions and antimicrobial activities. Their oligopeptide moieties are composed of both L ‐ and D ‐amino acids. Remarkably, the Leu5 amino acid—centrally located in the nonapeptide sequence—is the sole residue found to possess either an L or D configuration, depending on the producing strain. The impact of this D /L switch on the solution conformation was investigated by NMR‐restrained molecular modelling of the epimers pseudodesmin A and viscosinamide A. Although the backbone fold remained unaffected, the D /L switch adjusted the segregation between hydrophobic and hydrophilic residues, and thus the amphipathicity. It also influenced the self‐assembly capacity in organic solvents. Additionally, several new minor variants of viscosinamide A from Pseudomonas fluorescens DR54 were identified, and an NMR assay is proposed to assess the presence of either an L ‐ or D ‐Leu5. 相似文献