全文获取类型
收费全文 | 1609篇 |
免费 | 154篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 44篇 |
综合类 | 8篇 |
化学工业 | 426篇 |
金属工艺 | 72篇 |
机械仪表 | 62篇 |
建筑科学 | 84篇 |
矿业工程 | 4篇 |
能源动力 | 124篇 |
轻工业 | 128篇 |
水利工程 | 26篇 |
石油天然气 | 17篇 |
无线电 | 167篇 |
一般工业技术 | 242篇 |
冶金工业 | 75篇 |
原子能技术 | 16篇 |
自动化技术 | 282篇 |
出版年
2024年 | 7篇 |
2023年 | 36篇 |
2022年 | 56篇 |
2021年 | 99篇 |
2020年 | 81篇 |
2019年 | 103篇 |
2018年 | 144篇 |
2017年 | 130篇 |
2016年 | 149篇 |
2015年 | 85篇 |
2014年 | 110篇 |
2013年 | 180篇 |
2012年 | 120篇 |
2011年 | 88篇 |
2010年 | 79篇 |
2009年 | 56篇 |
2008年 | 43篇 |
2007年 | 32篇 |
2006年 | 18篇 |
2005年 | 9篇 |
2004年 | 10篇 |
2003年 | 13篇 |
2002年 | 13篇 |
2001年 | 11篇 |
2000年 | 8篇 |
1999年 | 4篇 |
1998年 | 13篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 12篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1979年 | 3篇 |
1975年 | 1篇 |
1973年 | 2篇 |
1970年 | 2篇 |
1969年 | 1篇 |
排序方式: 共有1777条查询结果,搜索用时 15 毫秒
91.
A modified thermodynamic insight to deliquescence of a void‐containing nanocrystal confirmed by MD simulation
下载免费PDF全文
![点击此处可从《American Institute of Chemical Engineers》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Hamed Akbarzadeh Mohsen Abbaspour Sirous Salemi Azizeh Masoumi Amir Nasser Shamkhali 《American Institute of Chemical Engineers》2016,62(11):4066-4077
Existence of voids in crystalline structures can affect their physical and chemical properties considerably. When the size of the crystal reaches to nanoscale, experimental determination of its void fraction is difficult. In this work, a molecular dynamics approach is introduced to find equilibrium void fractions of a simple cubic (CsCl) and fcc (KCl) nanocrystals by determination of their deliquescence relative humidity (DRH) for different sizes and void fractions and extrapolation of the results to the bulk limit. To confirm the simulation results, the size dependency of DRH to the nanoparticle size was studied thermodynamically by inclusion of size‐dependent density of water nanodroplet which leads to a simple homographic equation. This method proposes the equilibrium void percents of CsCl and KCl nanoparticles to be 10 and 15%, respectively, which are obtained by extrapolation of the results to the bulk limit. The success of obtained Möbius function was also confirmed by fitting it to experimental data for deliquescence of NaCl nanoparticles which implies the importance of considering density of water nanodroplet as a size dependent quantity. Also, using the mentioned thermodynamic approach, void dependency of deliquescence for the nanoparticles was found to be as a quasi‐linear trend which is compatible with the simulation results. It is noticeable that the approach used this work for determination of equilibrium void fraction is only valid if the utilized force fields are accurate. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4066–4077, 2016 相似文献
92.
Ultrathin buffer layer at organic/organic interface for managing the recombination profile in organic light‐emitting diodes: Metal versus dielectric buffer
下载免费PDF全文
![点击此处可从《应用聚合物科学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Davood Kalhor Ezeddin Mohajerani Omid HashemiPour Akram SalehiKian Mohsen Shojaeifar Mohammad Rasoul Babaei 《应用聚合物科学杂志》2016,133(36)
We report on the utilization of an ultrathin buffer layer at the organic/organic (O/O) interface to enhance device efficiency in organic light‐emitting diodes. Two different kinds of buffer layers are examined: metal and dielectric. It is shown that employment of an ultrathin Ag layer with a thickness of 1–2 nm enhances the device performance, while a MgF2 dielectric buffer cannot affect the device properties considerably. In particular, the turn‐on voltage of the device with an appropriate buffer layer is reduced about 3 V, its current efficiency increases by a factor of more than three, and the power efficiency increases by a factor of more than five in comparison to the control device when a Ag buffer layer is introduced at the O/O interface. By employment of the buffer layer at the interface, an accumulation of current carriers appears within the device that redistribute the recombination profile toward the interior part of the emissive layer. Also, morphological examinations reveal that distinguishable phase segregation occurs in the blend of the hole‐transport layer. In particular, the polymer component remains at the surface and facilitates the hole transport into the successive layers. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43894. 相似文献
93.
Microstructural evolution and mechanical properties of nanostructured 1060 aluminum alloy tubes processed by tubular-channel angular pressing (TCAP) process were investigated using electron back-scattered diffraction (EBSD), transmission electron microscopy (TEM) and nanoindentation analyzes. EBSD scans revealed a homogeneous ultrafine grained microstructure after the third passes of the TCAP process. Apart from that the mean grain sizes of the TCAP processed tubes were refined to 566 nm, 500 nm and 480 nm respectively after the first, second and third passes. The results showed that after the three TCAP passes, the grain boundaries with a high angle comprised 78% of all the boundaries. This is in comparison to the first pass processed sample that includes approximately 20% HAGBs. The TEM inspection afforded an appreciation of the role of very low-angle misorientation boundaries in the process of refining microstructure. Nanoindentation results showed that hardness was the smallest form of an unprocessed sample while the largest form of the processed sample after the three passes of TCAP indicated the highest resistant of the material. In addition, the module of elasticity of the TCAP processed samples was greater from that of the unprocessed sample. 相似文献
94.
Mohammad Ali Mohandesi Alireza Azarbakht Mohsen Ghafory‐Ashtiany 《The Structural Design of Tall and Special Buildings》2019,28(5)
Conditional spectra are a recent development in this field, which utilizes the advantages of spectral shape indicators, for example, epsilon and eta. The application of an eta indicator in conditional spectra calculations depends mainly on calculating the peak ground velocity epsilon, data about which are not readily available in the current literature. This issue has been solved by linear regression between the conventional epsilon and the peak ground velocity epsilon. However, not enough attention has been paid in the literature to the disaggregation of the eta indicator. For this reason, the disaggregation of seismic hazard based on the use of an eta indicator has been investigated in this paper, based on a simplified linear seismic source. The obtained results were compared with the available approach in the literature, which shows that this refinement has a meaningful effect on the conditional spectra specifically in the short period range. Furthermore, eta‐based conditional spectra are used at different hazard levels to select ground‐motion records. A three‐storeyed building is then analysed, and the corresponding annual probability of failure is calculated based on the full dataset as well as on the records, which were selected based on conditional spectra. 相似文献
95.
Ehteshami-Moinabadi Mohsen Nasiri Shahram 《Bulletin of Engineering Geology and the Environment》2019,78(1):69-88
Bulletin of Engineering Geology and the Environment - The combination of remote sensing observations, geological field investigations and geomorphological mapping and measurements along with faults... 相似文献
96.
Atashi Hossein Hajisafari Mohsen Rezaeian Fatemeh Parnian Mohammad Javad 《国际煤炭科学技术学报(英文)》2019,6(1):27-36
International Journal of Coal Science & Technology - The modeling of hydrocarbon selectivity and CO conversion of the Fischer–Tropsch synthesis over Fe–Ni/Al2O3 catalyst by using... 相似文献
97.
We review theories of polyelectrolyte (PE) coacervation, which is the spontaneous association of oppositely charged units of PEs and phase separation into a polymer-dense phase in aqueous solution. The simplest theories can be divided into “physics-based” and “chemistry-based” approaches. In the former, PEs are treated as charged, long-chain, molecules, defined by charge level, chain length, and chain flexibility, but otherwise lacking chemical identity, with electrostatic interactions driving coacervation. The “chemistry-based” approaches focus on the local interactions between the species for which chemical identity is critical, and describe coacervation as the result of competitive local binding interactions of monomers and salts. In this article, we show how these approaches complement each other by presenting recent approaches that take both physical and chemical effects into account. Finally, we suggest future directions toward producing theories that are made quantitatively predictive by accounting for both long range electrostatic and local chemically specific interactions. 相似文献
98.
This study investigated the effect of solubility of amphiphilic compounds of acidic crude oil in water on the surface and interfacial tension (IFT) with NaCl, MgCl2, CaCl2, and Na2SO4 salts. Accordingly, distilled water, along with the salts mentioned in zero ionic strength up to 2 mol were put in contact with crude oil to become saturated with amphiphilic compounds. The effects of these compounds were investigated on the properties of contact water by pH, total organic carbon (TOC), FTIR (Fourier transform infrared spectroscopy), water-air surface tension (ST), and water-n-decane IFT tests. The results showed that some of the organic components of crude oil, especially acidic and basic compounds, are present or soluble in water, which have a significant effect on reducing the surface and IFT. The IFT reduction of water-n-decane was greater than the water-air ST system. Also, the observations showed that for both NaCl and Na2SO4 salt water, with increasing ionic strength of water, there was an optimum salinity within the range of 0.1-0.25 mol/L for both salts with the amount of surface and IFT minimized at this point. In the other two salts, this point was delayed upon elevation of ionic strength and was observed at high salinity. In this case, divalent cations reduce tension rate compared to monovalent cations. Due to solubility of acidic and basic groups in water, pH of salt water illustrates an acidic trend. Results of the FTIR test confirmed solubility of these compounds as well. 相似文献
99.
100.
Mohsen Gholami Mohammad Reza Talaie Seyed Foad Aghamiri 《Korean Journal of Chemical Engineering》2014,31(2):322-326
A bi-modal porous structure MCM-41 (BPS-MCM-41) was synthesized and functionalized by 3-[2-(2-Aminoethylamino)ethylamino]propyltrimethoxysilane (TRI); also, its performance in amine grafting and CO2 capturing was compared with that of pore-expanded MCM-41 [1]. To create larger pores beside the mesoporous structure of MCM-41, carbon black nanoparticles were used as the solid template. Characterizing the BPS-MCM-41 using the BET and BJH techniques resulted in the surface reduction of 29.3 percent and volume increase of 68.46 percent. The pore size distribution showed two peaks: a narrow peak at 2.24 nm diameter, which belonged to micelles, and a wide one at about 50 nm due to the presence of used nanoparticles. The functionalization confirmed that BPS-MCM-41 is capable of accommodating a large quantity of amine groups. The CO2 adsorption measurement indicated that internal volume of the adsorbent was a critical factor affecting the adsorption capacity of the amine grafted adsorbents. 相似文献