全文获取类型
收费全文 | 929篇 |
免费 | 64篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 16篇 |
综合类 | 2篇 |
化学工业 | 187篇 |
金属工艺 | 10篇 |
机械仪表 | 48篇 |
建筑科学 | 32篇 |
能源动力 | 46篇 |
轻工业 | 96篇 |
水利工程 | 14篇 |
石油天然气 | 15篇 |
无线电 | 106篇 |
一般工业技术 | 193篇 |
冶金工业 | 68篇 |
原子能技术 | 22篇 |
自动化技术 | 143篇 |
出版年
2023年 | 19篇 |
2022年 | 57篇 |
2021年 | 75篇 |
2020年 | 67篇 |
2019年 | 56篇 |
2018年 | 52篇 |
2017年 | 49篇 |
2016年 | 49篇 |
2015年 | 28篇 |
2014年 | 40篇 |
2013年 | 90篇 |
2012年 | 48篇 |
2011年 | 57篇 |
2010年 | 36篇 |
2009年 | 31篇 |
2008年 | 27篇 |
2007年 | 19篇 |
2006年 | 11篇 |
2005年 | 10篇 |
2004年 | 7篇 |
2003年 | 6篇 |
2002年 | 7篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1999年 | 5篇 |
1998年 | 12篇 |
1997年 | 12篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 8篇 |
1988年 | 9篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1982年 | 4篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1975年 | 6篇 |
1974年 | 5篇 |
1973年 | 3篇 |
1970年 | 3篇 |
1969年 | 2篇 |
1965年 | 1篇 |
排序方式: 共有998条查询结果,搜索用时 984 毫秒
1.
Nur Lina Rashidah Mohd Rashid Abdullah Abdul Samat Abdul Azim Jais Mahendra Rao Somalu Andanastuti Muchtar Nurul Akidah Baharuddin Wan Nor Roslam Wan Isahak 《Ceramics International》2019,45(6):6605-6615
The performance of low-to-intermediate temperature (400–800?°C) solid oxide fuel cells (SOFCs) depends on the properties of electrolyte used. SOFC performance can be enhanced by replacing electrolyte materials from conventional oxide ion (O2-) conductors with proton (H+) conductors because H+ conductors have higher ionic conductivity and theoretical electrical efficiency than O2- conductors within the target temperature range. Electrolytes based on cerate and/or zirconate have been proposed as potential H+ conductors. Cerate-based electrolytes have the highest H+ conductivity, but they are chemically and thermally unstable during redox cycles, whereas zirconate-based electrolytes exhibit the opposite properties. Thus, tailoring the properties of cerate and/or zirconate electrolytes by doping with rare-earth metals has become a main concern for many researchers to further improve the ionic conductivity and stability of electrolytes. This article provides an overview on the properties of four types of cerate and/or zirconate electrolytes including cerate-based, zirconate-based, single-doped cerate–zirconate and hybrid-doped cerate–zirconate. The properties of the proton electrolytes such as ionic conductivity, chemical stability and sinterability are also systematically discussed. This review further provides a summary of the performance of SOFCs operated with cerate and/or zirconate proton conductors and the actual potential of these materials as alternative electrolytes for proton-conducting SOFC application. 相似文献
2.
Muhammad Sheeraz Mamoon Ur Rashid Asad Ali Fazli Akram Ho Jeong Lee Jin San Choi Jong-Seong Bae Yong Soo Kim Young-Han Shin Chang Won Ahn Tae Heon Kim 《Journal of the European Ceramic Society》2021,41(10):5155-5162
We demonstrate the structural evolution of polymorphic phases in Al2O3-inserted SrMnO3 ceramics synthesized by solid state reaction. While the 4H-hexagonal phase is predominant in pure SrMnO3 ceramics, a small amount of 6H-hexagonal polymorph is identified in addition to the primary 4H-hexagonal SrMnO3 and the secondary hexagonal SrAl2O4 phases in the as-sintered ceramics, evidenced by x-ray diffraction and subsequent Rietveld refinement analyses. The existence of the 6H-hexagonal SrMnO3 phase is corroborated using Raman spectroscopy. The chemical compositions and electronic structures of the Al2O3-inserted SrMnO3 compounds are also examined using energy dispersive spectroscopy and x-ray photoelectron spectroscopy, respectively. The first-principles calculations reveal that there is no clear difference between the total energies of 4H- and 6H-hexagonal polymorphs regardless of the presence/absence of Sr and oxygen vacancies. Possible origins are discussed with the estimation of actual strain based on the refined lattice parameter of 6H SrMnO3. 相似文献
3.
M. M. Rashid 《International journal for numerical methods in engineering》2002,55(4):431-450
A computational procedure for remapping material state information from one finite element mesh to another is described. The procedure is useful in connection with evolving meshes for inelastic problems, as for example occur in the context of fracture simulation and adaptive mesh refinement. The proposed method is based on weak enforcement of equality between corresponding fields on the two meshes, where piecewise‐constant fields on both meshes are generalized from the quadrature‐point values. The essential algorithmic problem is that of calculating the volume partition of an arbitrary convex region with respect to a covering set of disjoint convex regions. Instead of geometrically resolving the associated intersections, the problem is herein approximated by a constrained optimization problem, which may be readily and efficiently solved computationally. This formulation is a main contribution of the paper. Computational examples are given that illustrate the effectiveness of the proposed procedure. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
4.
5.
Touqeer Haseeb Zaman Shakir Amin Rashid Hussain Mudassar Al-Turjman Fadi Bilal Muhammad 《The Journal of supercomputing》2021,77(12):14053-14089
The Journal of Supercomputing - The Internet of Things is a rapidly evolving technology in which interconnected computing devices and sensors share data over the network to decipher different... 相似文献
6.
Pavel L. Katsel Tamara M. Dmitrieva Rashid B. Valeyev Yuri P. Kozlov 《Journal of chemical ecology》1992,18(11):2003-2010
Three components of the male yellowfin Baikal sculpin pheromonal signal have been isolated from urine by diethyl ether extraction, thinayer chromatography (TLC), and high-performance liquid chromatography (HPLC). Using mass spectrometry, we have identified two of them as testosterone (T) and 11-hydroxytestosterone (11HT). These steroids are synthesized in testes during full spermatogenesis, and they are excreted in male urine with milt. The third component is not a steroid. It is more likely to be a polyene alcohol (farnesol). 2Z,6E-Farnesol possesses behavioral activity. 相似文献
7.
The group decision‐making problem with linguistic information evaluation values of decision makers are used based on 2‐tuple interval‐valued. Operational laws on interval value 2‐tuple are introduced. On the basis of these laws, new aggregation operators are introduced by using the Choquet integral. A multiple attribute decision‐making method based on these aggregation operators is proposed. An example is given to illustrate the efficiency, practicality, and feasibility of our method. 相似文献
8.
Vadim S. Mikulich Alexander A. Muravsky Anatoli A. Murauski Iryna N. Kukhta Vladimir E. Agabekov Rashid Altamimi 《Journal of the Society for Information Display》2014,22(1):29-34
There are many photoaligned azo dyes that can be used for orientation of liquid crystals in various display devices. However, the structure of these compounds needs to be optimized to increase the rate of the process of molecule photoalignment, as well as to spread the application of these compounds. The main coordination metal that presents in the molecules of azo dyes is sodium derivatives. The use of other alkali metals remains an open question. We used quantum‐chemical computation methods and reversible intermolecular bonding model to determine the effect of metal coordination on the velocity of photoalignment. The theoretical predictions were experimentally verified using sodium, potassium, lithium, and cesium salts of the model azo dye synthesized by us. We conclude that potassium azo derivatives are the fastest, ceteris paribus. 相似文献
9.
M. Rashid Khan 《Fuel》1989,68(12):1522-1531
Coal devolatilization studies to maximize the yield of condensable products by operating at elevated temperatures and heating rates have been published. The objectives of this study were to investigate the influences of relatively mild operating conditions (e.g. relatively low temperature and pressure) on product quality, by comparing devolatilized products obtained at various temperatures and heating rates. Fixed bed, fluid bed, and entrained flow reactor units were used to obtain pyrolysis products. In addition, literature data on tar yields in various reactor units at a range of temperatures and residence times were surveyed and compared with experimental data. The liquids were characterized by a number of techniques, including field ionization mass spectroscopy (f.i.m.s.), sequential elution solvent chromatography (s.e.s.c.) and elemental analysis. The results demonstrate that the quality and yield of liquids obtained at a rapid heating rate are functions of peak pyrolysis temperature. It was shown that at a rapid heating rate, the yields of heavier polyfunctional groups (i.e. hydrocarbons with greater mean molecular weight) are greater than those obtained in the fixed bed slow heating rate reactor. The liquids generated at a slow heating rate are of lower molecular weight, viscosity, and sulphur content, and of higher H/C atomic ratios compared with the liquids obtained in a rapid heating rate unit. The effect of increasing the maximum pyrolysis temperature (at a constant slow heating rate) was to increase the yield of light gases (mainly H) at the expense of char hydrogen content and char reactivity. The tar yield is not markedly influenced when the peak devolatilization temperature is increased at a relatively slow heating rate. However, the quality (as defined by the H/C (atomic) ratio) of the liquids, and the reactivity (in air) of char, was reduced when the peak pyrolysis temperature was increased. At a rapid heating rate, the primary products, which have many structural characteristics of the parent coal, are devolatilized. The quality of the liquids obtained at a rapid heating rate is, therefore, determined by the devolatilized primary coal fragments evolved at the devolatilization temperature. In a slow heating rate fixed bed unit, however, the primary coal fragments undergo additional cracking reactions which involve stabilization of free radicals by donatable hydrogen. This leads to the formation of low molecular weight hydrocarbons of relatively higher quality. In-situ (both intraparticle or extraparticle) stabilization of reactive coal fragments by donatable hydrogen may lead to a significant improvement in the overall quality of the pyrolysis liquids in a fixed bed system in which time-temperature history is conducive for such reactions. 相似文献
10.
Multimedia Tools and Applications - Nowadays, web users frequently explore multimedia contents to satisfy their information needs. The exploration approaches usually provide linear interaction... 相似文献