全文获取类型
收费全文 | 456篇 |
免费 | 37篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 8篇 |
化学工业 | 108篇 |
金属工艺 | 5篇 |
机械仪表 | 14篇 |
建筑科学 | 13篇 |
矿业工程 | 1篇 |
能源动力 | 35篇 |
轻工业 | 39篇 |
水利工程 | 14篇 |
石油天然气 | 7篇 |
无线电 | 47篇 |
一般工业技术 | 71篇 |
冶金工业 | 39篇 |
原子能技术 | 7篇 |
自动化技术 | 86篇 |
出版年
2024年 | 1篇 |
2023年 | 7篇 |
2022年 | 10篇 |
2021年 | 19篇 |
2020年 | 20篇 |
2019年 | 23篇 |
2018年 | 38篇 |
2017年 | 37篇 |
2016年 | 23篇 |
2015年 | 15篇 |
2014年 | 30篇 |
2013年 | 45篇 |
2012年 | 26篇 |
2011年 | 43篇 |
2010年 | 34篇 |
2009年 | 19篇 |
2008年 | 16篇 |
2007年 | 8篇 |
2006年 | 8篇 |
2005年 | 11篇 |
2004年 | 6篇 |
2003年 | 4篇 |
2002年 | 4篇 |
2001年 | 1篇 |
1999年 | 4篇 |
1998年 | 11篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 5篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有494条查询结果,搜索用时 15 毫秒
421.
CHARACTERIZATION OF THE LATE APTIAN TOP‐DARIYAN DISCONFORMITY SURFACE OFFSHORE SW IRAN: A MULTI‐PROXY APPROACH
下载免费PDF全文
![点击此处可从《Journal of Petroleum Geology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
M. Naderi‐Khujin A. Seyrafian H. Vaziri‐Moghaddam V. Tavakoli 《Journal of Petroleum Geology》2016,39(3):269-286
The late Aptian disconformity at the top of the carbonate‐dominated Dariyan Formation is a regional‐scale surface recognised throughout SW Iran and adjacent areas to the south. This study investigates the disconformity using wireline logs, petrographic analyses, SEM observations, and CL and stable isotope data from an oilfield offshore SW Iran. The top‐Dariyan surface in the studied field is characterised by erosional incisions and clastic‐filled fissures which, together with secondary porosity in the underlying carbonates, uranium enrichment and meteoric infill cements, are interpreted as subaerial exposure‐related features. The clastic‐filled fissures were identified from gamma‐ray logs in horizontal wells, and infill material is composed of argillaceous carbonates, clays, quartz and iron‐bearing minerals. The correlation of GR logs in 19 vertical wells resulted in the recognition of erosional incisions (up to about 16 m deep) on the top‐Dariyan surface, together with thickening of siliciclastic sediments in the overlying basal part of the Kazhdumi Formation. Back‐filled sediments in erosional incisions may form potential exploration targets. Secondary porosity in the uppermost 20 m of the Dariyan Formation was created by meteoric processes during subaerial exposure. Cathodoluminescence microscopy of diagenetic cements, carbon and oxygen isotope data and elemental analyses were used to reconstruct the diagenetic history of the carbonates in the Upper Dariyan interval. 相似文献
422.
Majid Moghaddam Somayeh Timarchi Mohammad Hossein Moaiyeri Mohammad Eshghi 《Circuits, Systems, and Signal Processing》2016,35(5):1437-1455
This paper presents a new nine-transistor (9T) SRAM cell operating in the subthreshold region. In the proposed 9T SRAM cell, a suitable read operation is provided by suppressing the drain-induced barrier lowering effect and controlling the body–source voltage dynamically. Proper usage of low-threshold voltage (L-\(V_{\mathrm{t}}\)) transistors in the proposed design helps to reduce the read access time and enhance the reliability in the subthreshold region. In the proposed cell, a common bit-line is used in the read and write operations. This design leads to a larger write margin without using extra circuits. The simulation results at 90 nm CMOS technology demonstrate a qualified performance of the proposed SRAM cell in terms of power dissipation, power–delay product, write margin, read access time and sensitivity to process, voltage and temperature variations as compared to the other most efficient low-voltage SRAM cells previously presented in the literature. 相似文献
423.
Salehipour Masoud Rezaei Shahla Asadi Khalili Hasti Fateme Motaharian Ali Mogharabi-Manzari Mehdi 《Journal of Inorganic and Organometallic Polymers and Materials》2022,32(9):3321-3338
Journal of Inorganic and Organometallic Polymers and Materials - Metal–organic frameworks (MOFs) provide advantages as supporting materials for the immobilization of enzymes due to their... 相似文献
424.
M. R. Nabid M. Shamsianpour R. Sedghi A. B. Moghaddam S. Asadi S. Osati N. Safari 《化学工程与技术》2013,36(1):130-136
A novel biomimetic route for the synthesis of a water‐soluble poly(3,4‐ethylenedioxithiophene) (PEDT) in the presence of poly(styrene sulfonate) (PSS) and using iron(III)‐tetra(p‐sulfonatophenyl)porphyrin (FeIIITSPP), cobalt(III)‐tetra(p‐sulfonatophenyl)porphyrin (CoIIITSPP), manganese(III)‐tetra(p‐sulfonatophenyl)porphyrin (MnIIITSPP), and copper(II)‐tetra(p‐sulfonatophenyl)porphyrin (CuIITSPP) as effective catalysts is presented. The reactions were performed with different monomer, catalyst, template, and initiator concentrations. The absorbance of the polaron bands at various pH values indicated pH 2 as the best condition for polymerization. Precipitation or salting out was highly dependent on the mentioned factors. The formation of PEDT was confirmed by UV‐Vis and FT‐IR spectroscopy. Cyclic voltammetry proved the convenient electroactivity of the synthesized polymer. The presence of PSS that serves as a charge‐compensating dopant provides processability and water solubility and, in addition, a distinct advantage over similar reactions employing native enzymes due to higher stability and lower cost of the catalysts. 相似文献
425.
Shahram Shahriari Shahram Azadi Majid M. Moghaddam 《Journal of Mechanical Science and Technology》2010,24(6):1319-1327
In this paper, an accurate and simple model of a satellite with two flexible solar panels for three-dimensional dynamic studies
is proposed and compared with other models. In the proposed model, each solar panel is assumed to be rigid and attached to
the satellite body via a simple hinge, a torsional spring, and a torsional damper. Kane’s method is utilized to derive the
equations of motion. The model of flexible satellite with the assumption of Euler-Bernoulli beam for the solar panels, generally
used in the literature, has been introduced for comparison. A comprehensive model of flexible satellite, considering solar
panels as flexible and finite element panels, has been provided in ADAMS environment as a reference when comparing the two
mentioned models. The Euler-Bernoulli model does not appropriately simulate the three-dimensional motion of satellite. Conversely,
the hinged, rigid-panel model proposed in this paper provides suitable results in both two- and three-dimensional maneuvers. 相似文献
426.
427.
Block-wise 2D kernel PCA/LDA for face recognition 总被引:1,自引:0,他引:1
Armin Eftekhari Hamid Abrishami Moghaddam Javad Alirezaie 《Information Processing Letters》2010,110(17):761-766
Direct extension of (2D) matrix-based linear subspace algorithms to kernel-induced feature space is computationally intractable and also fails to exploit local characteristics of input data. In this letter, we develop a 2D generalized framework which integrates the concept of kernel machines with 2D principal component analysis (PCA) and 2D linear discriminant analysis (LDA). In order to remedy the mentioned drawbacks, we propose a block-wise approach based on the assumption that data is multi-modally distributed in so-called block manifolds. Proposed methods, namely block-wise 2D kernel PCA (B2D-KPCA) and block-wise 2D generalized discriminant analysis (B2D-GDA), attempt to find local nonlinear subspace projections in each block manifold or alternatively search for linear subspace projections in kernel space associated with each blockset. Experimental results on ORL face database attests to the reliability of the proposed block-wise approach compared with related published methods. 相似文献
428.
Nasser Bagheri Moghaddam Sayyed Moslem Mousavi Masoud Nasiri Enayat A. Moallemi Hami Yousefdehi 《Renewable & Sustainable Energy Reviews》2011,15(8):4200-4211
Iran, as a developing country, will be confronted with a significant increase in electricity demand in future years. Being a petroleum producing country has resulted in extreme subsidies for energy production from fossilized resources such as oil and gas. This issue is one of the most important factors regarding underdevelopment of renewable energies in Iran. Expansive use of fossil resources in providing the necessary energy has resulted in Iran being among the 20 countries that have a share in the 75% spread of greenhouse gases. This issue has resulted in greater attention on behalf of the energy sectors policy makers regarding renewable energies, especially wind. Awareness regarding the current condition of each system is the first step for optimum policy making. On this basis, analyzing Iran's wind conditions and assessing its technological capabilities is considered a pre-requisite for the wind sectors policy making. This paper aims at studying Iran's wind energy status in the form of available capacities, power production, wind power plant characteristics, principal agents and existing protective laws. Also, the main focus of this paper is on evaluating Iran's potential and effective technological capabilities for producing the main parts of wind turbines in different sizes. In order to fulfill this task, sector-level technological capabilities are defined. Then by analyzing active organizations in this field, Iran's capability level will be determined and by comparing it with the ideal conditions, Iran's technological gaps will be identified. The reasons for the creation of such shortcomings will also be introduced from different aspects in the form of the Atlas model. Finally, Iran's potential capabilities in resolving technological shortcomings will be identified. 相似文献
429.
Extended reaction zone anodes for formic acid oxidation have been prepared by the spontaneous deposition of Pd on polyaniline coated carbon fibre paper. The PANI supports, deposited on carbon fibre paper either galvanostatically, potentiostatically, or potentiodynamically, were characterized by electron microscopy, cyclic voltammetry and impedance spectroscopy. Pd was deposited on them by spontaneous reduction of Pd(II) by the reduced form of the PANI in order to preserve the characteristics of each type of PANI layer. It was found that galvanostatically deposited PANI produced electrodes that were much more active for formic acid oxidation than PANI produced under potential control. The morphology and mean particle size of Pd was found to depend strongly on the way in which the PANI was prepared and also correlated with the resistance and capacitance of the PANI at low potentials. It is proposed that the electrochemical characteristics of the PANI play a significant role in determining the morphology, particle size, and electrocatalytic activity for formic acid oxidation of the spontaneously deposited Pd. 相似文献
430.
Gholam Hossein Shahverdizadeh Shahla Masoudian Ali Akbar Soudi Fahime Bigdeli Hassan Hosseini Monfared Ali Morsali Hamid Reza Khavasi 《Journal of Inorganic and Organometallic Polymers and Materials》2011,21(1):171-174
A new three-dimensional Cd(II) coordination polymer, {[Cd3(3-pyc)4(NCS)2(H2O)4]·2H2O}
n
(1); 3-Hpyc = 3-pyridinecarboxylic acid, was prepared and characterized by elemental analyses and IR spectroscopy. Compound
1 was structurally characterized by single-crystal X-ray diffraction. The structural determination shows that the compound
is a new 3D coordination polymer has different environments containing CdO5NS and CdO2N4 units. This polymeric precursor has been used in the preparation of Cd3OSO4 nanoparticles by thermolysis in oleic acid. The new nano-structure of Cd3OSO4 was characterized by scanning electron microscopy and X-ray powder diffraction. This study demonstrates that coordination
polymers may be suitable precursors to the preparation of desirable nanoscale materials. 相似文献