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311.
M. Saeed Butt Zareen Akhter Michael Bolte Humaira Masood Siddiqi Haq Nawaz M. Zafar‐uz‐Zaman 《应用聚合物科学杂志》2009,114(4):2101-2108
The diamine 2‐methyl‐1,3‐bis(4‐aminophenyloxy)benzene was prepared via a nucleophilic substitution reaction and was characterized with Fourier transform infrared, elemental analysis, and 1H‐ and 13C‐NMR spectroscopy. The prepared diamine was also characterized with single‐crystal analysis. The geometric parameters of C19H18N2O2 were in the usual ranges. The dihedral angles between the central phenyl ring and the two terminal aromatic rings were 88.9 and 91.6°. The crystal structure was stabilized by N? H···N hydrogen bonds. The diamine was then polymerized with 3,3′,4,4′‐benzophenone tetracarboxylic acid dianhydride, 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride, 3,4,9,10‐perylenetetracarboxylic acid dianhydride, and pyromellitic dianhydride by either a one‐step solution polymerization reaction or a two‐step procedure. These polymers had inherent viscosities ranging from 0.61 to 0.85 dL/gm. Some of the polymers were soluble in most common organic solvents even at room temperature, and some were soluble on heating. The degradation temperatures of the resultant polymers fell in the range of 260–500°C in nitrogen (with only 10% weight loss). The specific heat capacity at 200°C ranged from 1.0 to 2.21 J g?1 K?1. The temperatures at which the maximum degradation of the polymer occurred ranged from 510 to 610°C. The glass‐transition temperatures of the polyimides ranged from 182 to 191°C. The activation energy and enthalpy of the polyimides ranged from 44.44 to 73.91 kJ/mol and from 42.58 to 72.08 kJ/mol K, respectively. The moisture absorption was found in the range of 0.23–0.71%. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
312.
Saeed A. Khan Kidon Sung Mohamed S. Nawaz Carl E. Cerniglia Mark L. Tamplin Robert W. Phillips Lynda Collins Kelley 《Food microbiology》2009
In this study, we investigated the survival and inactivation kinetics of a surrogate strain of Bacillus anthracis (Sterne strain) in whole egg (WE), egg white (EW), sugared egg yolk (YSU), and salted egg yolk (YSA) at low (−20, 0, and 5 °C), moderate (15, 20, 25, 30, 35, and 40 °C), and high storage temperatures (45, 50, 55, and 60 °C). Outgrowth of the spores was measured as lag phase duration (LPD). Replication of vegetative cells was measured in terms of growth rate (GR) and maximum population density (MPD). Spore inactivation was recorded as inactivation rate and percent reduction in viable count. In general, spore viability decreased at low and high temperatures and increased at moderate temperatures. At 0 and 5 °C, a 60–100% reduction in spore viability was seen within 2–3 weeks in WE and YSU, 0–30% in YSA, and 50–100% in EW. At −20 °C, however, no drop in spore titer was observed in YSU and EW but a 20% drop in titer was seen in YSA and 50% in WE within 2–3 weeks. At high temperatures, WE, EW, and YSA produced a 20–50% drop in the spore titer within 1–4 h whereas YSU showed 100% inactivation within 0.75 h. At moderate storage temperatures, as the temperature increased from 15 to 40 °C, LPD decreased from 13.5 to 0.75 h and MPD reached 0.27–2.2 × 109 CFU/ml in YSU and WE, respectively. Markedly lower growth was observed in YSA (LPD = 24–270 h, MPD = 9 × 105 CFU/ml) and spores were inactivated completely within 1–6 h in EW. The survivability and inactivation data of B. anthracis in liquid egg products reported in this investigation will be helpful in developing risk assessment models on food biosecurity. 相似文献
313.
314.
Aun Nawaz Khan Mohsin Muhyuddin Abdul Wadood 《Russian Journal of Non-Ferrous Metals》2017,58(5):509-515
Shape Memory Alloys (SMA) are unique class of alloys which possess various engineering applications. One such SMA is Nickel–Titanium (Nitinol) shape memory alloy. The problem, however with Nickel is that the metal may leach out in form of toxic Ni2+ ions. The latter may prove costly when used in various applications. To increase the corrosion resistant properties of Nitinol and to evaluate its shape memory properties, small amount of Zirconium i.e. 5 and 10 at % are added into the existing Nitinol system. Buttons of Nitinol and Nickel–Titanium with Zirconium additions are made using the button arc furnace. For the characterization of the alloys, various techniques including Energy Dispersive Spectroscopy (EDS), Back Scattering Electron (BSE) imaging, Differential Scanning Calorimetry (DSC) have been performed. The work conducted reveals that addition of Zirconium in Nitinol has marked influence on microstructure, shape memory properties, transformation temperature, hardness values, and corrosion properties of the alloy. 相似文献
315.
316.
Malik A. Nawaz Shu Fukai Bhesh Bhandari 《International Journal of Food Properties》2017,20(5):1174-1185
A procedure for in situ analysis of rice cooking was developed in this study. Grain softening during soaking and cooking of selected rice varieties (fresh and aged TDK8, TDK11, and Doongara) were subjected to in situ analysis by using a thermally controlled sample block (thermal mechanical compression test) attached to a texture analyzer. This technique measures the changes in the mechanical properties of intact rice grain during cooking continuously. The results obtained from the thermal mechanical compression test technique were validated against two standard and conventional procedures viz; analyzing the pasting properties of rice flours by rapid visco analyzer and microscopic observations during the cooking of rice grains. The technique developed in this study was found valid for in situ analysis of rice cooking. This technique can be used for a sample size as small as 0.50 g. 相似文献
317.
318.
Yasir Nawaz Muhammad Shoaib Arif Mairaj Bibi Javeria Nawaz Abbasi Umer Javed Amna Nazeer 《计算机、材料和连续体(英文)》2020,62(2):657-677
Present contribution is concerned with the construction and application of a
numerical method for the fluid flow problem over a linearly stretching surface with the
modification of standard Gradient descent Algorithm to solve the resulted difference
equation. The flow problem is constructed using continuity, and Navier Stoke equations
and these PDEs are further converted into boundary value problem by applying suitable
similarity transformations. A central finite difference method is proposed that gives
third-order accuracy using three grid points. The stability conditions of the present
proposed method using a Gauss-Seidel iterative procedure is found using VonNeumann stability criteria and order of the finite difference method is proved by
applying the Taylor series on the discretised equation. The comparison of the presently
modified optimisation algorithm with the Gauss-Seidel iterative method and standard
Newton’s method in optimisation is also made. It can be concluded that the presently
modified optimisation Algorithm takes a few iterations to converge with a small value
of the parameter contained in it compared with the standard descent algorithm that may
take millions of iterations to converge. The present modification of the steepest descent
method converges faster than Gauss-Seidel method and standard steepest descent
method, and it may also overcome the deficiency of singular hessian arise in Newton’s
method for some of the cases that may arise in optimisation problem(s). 相似文献
319.
Recent developments in biochar as an effective tool for agricultural soil management: a review 总被引:2,自引:0,他引:2
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Mahmood Laghari Ravi Naidu Bo Xiao Zhiquan Hu Muhammad Saffar Mirjat Mian Hu Muhammad Nawaz Kandhro Zhihua Chen Dabin Guo Qamardudin Jogi Zaidun Naji Abudi Saima Fazal 《Journal of the science of food and agriculture》2016,96(15):4840-4849
In recent years biochar has been demonstrated to be a useful amendment to sequester carbon and reduce greenhouse gas emission from the soil to the atmosphere. Hence it can help to mitigate global environment change. Some studies have shown that biochar addition to agricultural soils increases crop production. The mechanisms involved are: increased soil aeration and water‐holding capacity, enhanced microbial activity and plant nutrient status in soil, and alteration of some important soil chemical properties. This review provides an in‐depth consideration of the production, characterization and agricultural use of different biochars. Biochar is a complex organic material and its characteristics vary with production conditions and the feedstock used. The agronomic benefits of biochar solely depend upon the use of particular types of biochar with proper field application rate under appropriate soil types and conditions. © 2016 Society of Chemical Industry 相似文献
320.
This article presents a 2 × 2 series fed 2.4 GHz patch antenna array having multiple beam switching capabilities by using two simple 3 dB/90° couplers to achieve required amplitude and phase excitations for array elements with reduced complexity, cost and size. The beam switching performance with consistent gain and low side lobe levels (SLL) is achieved by exciting the array elements from orthogonally placed thin quarter‐wave (λg/4) feeds. The implemented array is capable to generate ten (10) switched‐beams in 2‐D space when series fed elements are excited from respective ports through 3 dB quadrature couplers. The dual polarized characteristics of presented array provide intrinsic interport isolation between perpendicularly placed ports through polarization diversity to achieve independent beam switching capabilities for intended directions. The implemented antenna array on 1.575 mm thick low loss (tan δ = 0.003) NH9450 substrate with εr = 4.5 ± 0.10 provides 10 dB return loss impedance bandwidth of more than 50 MHz. The measured beam switching loss is around 0.8 dB for beams switched at θ = ±20°, Ф = 0°, 90°, and 45° with average peak gain of 9.5 dBi and SLL ≤ ?10 dB in all cases. The novelty of this work is the capability of generating ten dual polarized switched‐beams by using only two 3 dB/90° couplers as beam controllers. 相似文献