全文获取类型
收费全文 | 608篇 |
免费 | 21篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 4篇 |
化学工业 | 81篇 |
金属工艺 | 10篇 |
机械仪表 | 31篇 |
建筑科学 | 23篇 |
矿业工程 | 1篇 |
能源动力 | 31篇 |
轻工业 | 57篇 |
水利工程 | 4篇 |
石油天然气 | 6篇 |
无线电 | 60篇 |
一般工业技术 | 89篇 |
冶金工业 | 170篇 |
原子能技术 | 3篇 |
自动化技术 | 61篇 |
出版年
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 12篇 |
2020年 | 7篇 |
2019年 | 12篇 |
2018年 | 22篇 |
2017年 | 12篇 |
2016年 | 20篇 |
2015年 | 15篇 |
2014年 | 15篇 |
2013年 | 41篇 |
2012年 | 19篇 |
2011年 | 21篇 |
2010年 | 20篇 |
2009年 | 24篇 |
2008年 | 27篇 |
2007年 | 20篇 |
2006年 | 16篇 |
2005年 | 16篇 |
2004年 | 16篇 |
2003年 | 11篇 |
2002年 | 10篇 |
2000年 | 10篇 |
1999年 | 7篇 |
1998年 | 34篇 |
1997年 | 19篇 |
1996年 | 14篇 |
1995年 | 18篇 |
1994年 | 10篇 |
1993年 | 18篇 |
1992年 | 10篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1976年 | 10篇 |
1974年 | 4篇 |
1972年 | 3篇 |
1967年 | 3篇 |
1957年 | 3篇 |
排序方式: 共有631条查询结果,搜索用时 15 毫秒
161.
Maher M. Al-Dabbas Khaled Al-Ismail Kanefumi Kitahara Naoya Chishaki Fumio Hashinaga Toshihiko Suganuma Kenjiro Tadera 《Food chemistry》2007,104(2):734-739
The DPPH radical-scavenging activity of 25 inorganic salts, two buffer systems, and crude water extract of aerial parts of Varthemia (Varthemia iphionoides) before and after resins purification were investigated. Eight of the 25 inorganic salts tested quenched the DPPH radical colour. Na2S2O3 and FeCl2 showed markedly high DPPH colour-quenching activity, with inhibition of 65.3% and 47.7% respectively, at a concentration of 10 μg/ml. Four salts slightly increased the intensity of DPPH radical colour. The rest of tested salts, acetate buffer, and phosphate buffer at a concentration less than 0.1 mM did not affect DPPH radical colour. The DPPH radical-scavenging activity of BHT and catechol was considerably affected by the concentration of phosphate buffer (pH 7.0), and by acetate buffer (pH 5.0) at concentrations more than 0.01 mM in the case of BHT only. The DPPH radical-scavenging activity of a crude water extract of aerial parts of Varthemia iphionoides was much higher than that of an extract desalted by cation-exchange resin, indicating that iron ions apparently elevated the DPPH radical-scavenging activity of the extract. Therefore, desalting of plant extracts is important in order to obtain the true value of DPPH radical-scavenging activity. 相似文献
162.
Maher A.R. Sadiq Al-Baghdadi 《Renewable Energy》2009,34(3):674-682
A three-dimensional, multi-phase, non-isothermal computational fluid dynamics model of a proton exchange membrane fuel cell has been developed and used to investigate the displacement, deformation, and stresses inside the whole cell, which developed during the cell operation due to the changes of temperature and relative humidity. The behaviour of the fuel cell during operation has been studied and investigated under real cell operating conditions. A unique feature of the present model is to incorporate the effect of hygro and thermal stresses into actual three-dimensional fuel cell model for a complete cell with both the membrane-electrode-assembly and the gas distribution flow channels. The results show that the non-uniform distribution of stresses, caused by the temperature gradient in the cell, induces localized bending stresses, which can contribute to delaminating between the membrane and the gas diffusion layers. The non-uniform distribution of stresses can also contribute to delaminating between the gas diffusion layers and the channels, especially in the cathode side. These stresses may explain the occurrence of cracks and pinholes in the fuel cells components under steady-state loading during regular cell operation, especially in the high loading conditions. 相似文献
163.
Terpolymer samples were prepared by free radical polymerization of methyl methacrylate (MMA), indene (In) and acrylonitrile (AN) in bulk. The samples were chosen so that the molar ratio of AN to MMA varied from 1.00:4.39 to 1.00:0.83, while the molar ratio of In was kept almost unchanged. The glass transition temperatures (Tg) of the samples were determined using differential scanning calorimetry. Moreover, isochronal dynamic mechanical measurements of the complex bending modulus as well as the complex dielectric permittivity were carried out over wide temperature ranges, namely from 50 to 190 °C, depending on the material investigated. All samples exhibited a single common Tg value, which increased to higher temperature upon increasing the content of AN. In addition, the results were investigated quantitatively in the framework of a molecular model. Copyright © 2006 Society of Chemical Industry 相似文献
164.
Johannes Staguhn Christine Allen Dominic Benford Elmer Sharp Troy Ames Rick Arendt David Chuss Eli Dwek Attila Kovacs Stephen Maher Catherine Marx Tim Miller S. Harvey Moseley Santiago Navarro Albrecht Sievers George Voellmer Edward Wollack 《Journal of Low Temperature Physics》2008,151(3-4):709-714
The 2 mm spectral range provides a unique terrestrial window enabling ground based observations of the earliest active dusty
galaxies in the universe and thereby allowing a better constraint on the star formation rate in these objects. We have built
GISMO (the Goddard-IRAM Superconducting 2-Millimeter Observer), a 2 mm, 128 element superconducting Transition Edge Sensor
(TES) based bolometer camera for the IRAM 30 m telescope in Spain. The camera uses an 8×16 planar array of multiplexed TES
bolometers, which incorporates our recently designed Backshort Under Grid (BUG) architecture, described elsewhere. The optical
design incorporates a 100 mm (4 inches) diameter silicon lens cooled to 4 K, which provides the required fast beam of 0.9
λ/D. With this spatial sampling, GISMO will be very efficient at detecting sources serendipitously in large sky surveys, while
the capability for diffraction-limited observations is preserved. With the background limited performance of the detectors,
the camera provides significantly greater imaging sensitivity and mapping speed at this wavelength than has previously been
possible. The major scientific driver for the instrument is to provide the IRAM 30 m telescope with the capability to rapidly
observe galactic and extragalactic dust emission, in particular from high-z Ultra Luminous Infrared Galaxies (ULIRGs) and
quasars, even in the summer season. The instrument will fill in the SEDs of high redshift galaxies at the Rayleigh-Jeans part
of the dust emission spectrum, even at the highest redshifts. Our source count models predict that GISMO will serendipitously
detect one galaxy every four hours on the blank sky, and that one quarter of these galaxies will be at a redshift of z 6.5.
We expect to install GISMO at the 30 m telescope in the second half of 2007.
相似文献
165.
Maher Chaouachi Mohamed Salem Zellama Nesrine Nabi Ahmed Ben Hafsa Khaled Saïd 《Food Analytical Methods》2014,7(1):224-233
In response to the increasing number of genetically modified (GM) events released on the market, control laboratories explore various strategies to simplify and reduce the number of tests needed to characterise the content in genetically modified organism (GMO) of a given sample. Lastly, multiplexing is considered as one of the possible ways to decrease the time and cost of analysis. Here, we report the development of four duplex polymerase chain reaction (PCR) tests for the identification and the quantification of four maize transformation events from which commercial lines have been authorised in Europe namely, Bt11 and Bt176 (Syngenta, DE, USA), Mon810 MaisGard? (Monsanto, MO, USA) and T25 Liberty Link? (Bayer CropScience, Monheim, Germany). The duplex PCR tests combine a maize-specific PCR test hybridising in the Adh1 locus with an event-specific detection system designed on a junction fragment for each of these four GM maize. Real-time PCR tests, suitable to comply with the European regulation, were designed by using Taqman® chemistry. 相似文献
166.
167.
168.
Maher Al-Ibrahim Steffi Sensfuss Jutta Uziel Gernot Ecke Oliver Ambacher 《Solar Energy Materials & Solar Cells》2005,85(2):277-283
Polymer solar cells based on regioregular poly(3-hexylthiophene) (P3HT) and ([6,6]-phenyl-C61-butyric acid methyl ester) (PCBM) were fabricated with two different architectures (normal and inverse). Normal cells using indium tin oxide (ITO) as anode and Al as cathode were fabricated on polyester foils and illuminated from substrate side. Inverse cells using Ti as cathode and ultrathin Au layer as anode were illuminated from the top side covered by a transparent Au contact. Both Au layer and PET/ITO show comparable transmission in the spectral range where P3HT absorbs. Inverse cells showed comparable device parameters to normal cell (open circuit voltage 550 mV, short circuit current 6.25 mA/cm2, fill factor 0.33 and white light power conversion efficiency 1.12%). 相似文献
169.
In the era of mobile and wireless networks, the growing complexity of end devices and the accentuated tendency towards miniaturization of them raise new security challenges. Authentication is a crucial concern in resource constrained environments, and despite the great number of existing EAP methods, as explained in the article, we are still in need for EAP methods tightly adapted to wireless environments and satisfying heterogeneity of terminals and their limitations of resources. After a first comparative analysis of existing EAP methods, this article presents a new EAP-EHash method (EHash for encrypted hash) that is adapted to the highly vulnerable wireless environment by supporting mutual authentication and session key derivation and offering simplicity, rapidity, and easy-to-deploy features. This EAP-EHash was formally proven to satisfy the claimed security properties, thanks to the AVISPA tool. Implementation of it on an 802.11 testbed platform gave realistic authentication delays averaging 26 ms and thus proved that EAP-EHash is competitive to EAP-MD5 that is known to be the simplest of the EAP methods. Features of EAP-EHash include short execution delays and low bandwidth consumption, and as such, it appears attractive for wireless. 相似文献
170.
Water treatment plants traditionally use coagulation/flocculation process to remove organics and turbidity particles in drinking water. As a result of the chemical optimisation of the coagulation process having such a strong influence, it is believed that the current hydraulic conditions for flocculation cited under best practice could be out of date. A 450 Mld plant treating upland water was chemically optimised, and it was observed that the total mixing energy input could be reduced by 66% without any detrimental impact upon the clarified water being observed. Under the new mixing regime, energy costs could be reduced by £37 300 pa equating to approximately a 280 t reduction in CO 2. 相似文献