全文获取类型
收费全文 | 356篇 |
免费 | 20篇 |
国内免费 | 5篇 |
专业分类
综合类 | 1篇 |
化学工业 | 104篇 |
金属工艺 | 1篇 |
机械仪表 | 6篇 |
建筑科学 | 8篇 |
能源动力 | 14篇 |
轻工业 | 54篇 |
水利工程 | 5篇 |
石油天然气 | 1篇 |
无线电 | 39篇 |
一般工业技术 | 88篇 |
冶金工业 | 13篇 |
原子能技术 | 3篇 |
自动化技术 | 44篇 |
出版年
2024年 | 1篇 |
2023年 | 13篇 |
2022年 | 27篇 |
2021年 | 47篇 |
2020年 | 27篇 |
2019年 | 23篇 |
2018年 | 21篇 |
2017年 | 29篇 |
2016年 | 21篇 |
2015年 | 17篇 |
2014年 | 10篇 |
2013年 | 22篇 |
2012年 | 15篇 |
2011年 | 23篇 |
2010年 | 16篇 |
2009年 | 18篇 |
2008年 | 18篇 |
2007年 | 9篇 |
2006年 | 4篇 |
2001年 | 1篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1994年 | 2篇 |
1990年 | 1篇 |
1988年 | 2篇 |
1978年 | 1篇 |
排序方式: 共有381条查询结果,搜索用时 15 毫秒
321.
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
322.
Recent developments in biochar as an effective tool for agricultural soil management: a review 总被引:2,自引:0,他引:2
下载免费PDF全文
![点击此处可从《Journal of the science of food and agriculture》网站下载免费的PDF全文](/ch/ext_images/free.gif)
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
323.
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
324.
325.
Imran Rab Nawaz Ting Wang Athar Ali Khan Gorar Adnan Ghani Soomro Syed Kamran Sami Ahmer Hussain Shah Jun Wang Wen-Bin Liu Syed Haseeb Sultan Aijaz Ahmed Babar Abdul Qadeer Dayo 《应用聚合物科学杂志》2021,138(43):51279
In the current study, 1 wt%, NaOH treated pine cone (ATPC) particles composites with bisphenol-A aniline based benzoxazine (BA-a) matrix were prepared by isothermal compression method. Ultimate impacts of ATPC reinforcement on the thermomechanical, tensile, flexural, and impact properties of the composites were studied by using a dynamic mechanical analyzer (DMA), a Universal testing machine, and a Tinius-Olsen impact device, respectively. The thermal stability of ATPC particles was remarkably increased, TGA confirmed that particles will not be degraded during the curing. The DMA results of 30 wt% ATPC reinforced composites confirmed that the glass transition temperature, storage modulus, and loss modulus were 22 ° C, 2510, and 250 MPa higher than the neat matrix, respectively. In addition, the impact strength of the 30 wt% ATPC reinforced composites was nearly 3 times higher than the neat matrix, which confirmed that the matrix's brittleness is reduced, similar observation was confirmed by the Brostow and coworkers empirical model. Moreover, a gradual rise in the tensile and flexural properties was also recorded. We can easily conclude from the studied parameters that the ATPC particles can be used as a sustainable agro-waste in polymeric composites. 相似文献
326.
Sidra Pervez Muhammad Asif Nawaz Afsheen Aman Sadia Qayyum Faiza Nawaz Shah Ali Ul Qader 《Catalysis Letters》2018,148(9):2643-2653
This study deals with the immobilization of amyloglucosidase within agarose using method of entrapment. Enzyme was produced from Aspergillus fumigatus KIBGE-IB33 and then partially purified using 40% ammonium sulphate saturation. Using 40 gl?1 concentration of agarose and adjusting 3.0 mm size of hydrogels, maximum entrapment yield (78%) was obtained. The kinetic behavior was slightly changed after immobilization as reaction time and reaction temperature increases from 5.0 min (soluble) to 10.0 min (immobilized) and 60 °C (soluble) to 65 °C (immobilized), respectively while, pH optima remained same (pH 5.0). Substrate saturation kinetics revealed that Km was increased from 1.47 to 4.215 mg ml?1 while, the value of Vmax decreased from 947 to 611 kU mg?1 for soluble and entrapped amyloglucosidase, respectively. The stability profile of amyloglucosidase also significantly improved after entrapment in agarose hydrogels at 50, 60 and 70 °C for 120 min with retention of 77, 59 and 25% residual activity, respectively. Furthermore, the t1/2 of soluble and immobilized amyloglucosidase at 60 °C was 167 and 375 min respectively. Due to increase in reusability for various subsequent cycles of entrapped amyloglucosidase, about 8.73 mg ml?1 increase in glucose production was observed as compared to soluble enzyme. 相似文献
Graphical Abstract
327.
Misbah Sultan Sadia Atta Haq Nawaz Bhatti Atif Islam Tahir Jamil Ismat Bibi 《Polymer-Plastics Technology and Engineering》2017,56(15):1608-1618
The waterborne polyurethane acrylate coatings are smart option to reduce the environmental hazards. To evaluate the structure–property relationship, polyurethane acrylate coating dispersions were synthesized with aromatic and aliphatic hard segments. Furthermore, to evaluate the performance, dispersions were used to finish the cotton fabric. The dispersions were prepared by prepolymer method followed by emulsion polymerization in aqueous medium. The characterization of dispersions was performed by Fourier transform infrared, dynamic light scattering, atomic force microscopy, differential scanning calorimetry, and thermogravimetric analysis. In general, aliphatic hard segment has shown more appreciable results. But, thermal stability of aromatic polyurethane acrylate was more pronounced as inherent rigidity of aromatic diisocyanate dominates. 相似文献
328.
Muhammad Nawaz Naeem Madiha Gamkhar Shahid Hussain Arshad Abdul Ghafar Shah 《Journal of Mechanical Science and Technology》2013,27(3):649-656
This study gives a brief work on vibration characteristics of cylindrical shells submerged in an incompressible fluid. The shell is presumed to be structured from functionally graded material. The effect of the fluid is introduced by using the acoustic wave equation. Love’s first order thin shell theory is utilized in the shell dynamical equations. The problem is framed by combining shell dynamical equations with the acoustic wave equation. Fluid-loaded terms are associated with Hankel function of second kind. Wave propagation approach is employed to solve the shell problem. Some comparisons of numerical results are performed for the natural frequencies of simply supported-simply supported, clamped-clamped and clamped-simply supported boundary conditions of isotropic as well as functionally graded cylindrical shells to check the validity of the present approach. The influence of fluid on the submerged functionally graded cylindrical shells is noticed to be very pronounced. 相似文献
329.
This work deals with the junction and channel optimization on FinFET devices. The main objective was to show feasibility of a three-dimensional (3D) process simulation within the context of optimization of the device design and the underlying fabrication processes. The 3D simulation process flow is based on the development of the SOI based FinFET devices at Infineon. Similar to real devices, important 3D geometrical features, such as corner roundings and 3D facets have been introduced into the simulation setup, which is based on commercially available 3D process simulation software (Taurus 3D). The influence of various unit process steps, such as channel implant, and LDD implant on the electrical performance of the devices have been evaluated. Beside the successful demonstration of a functional 3D process simulation flow, detailed issues of process and device simulation methodology such as the usage of different dopant diffusion and mobility models are assessed. Finally, a comparison of the simulation results with electrical measurement data is performed which fairly shows excellent agreement. 相似文献
330.