全文获取类型
收费全文 | 429篇 |
免费 | 16篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 4篇 |
综合类 | 1篇 |
化学工业 | 98篇 |
金属工艺 | 22篇 |
机械仪表 | 10篇 |
建筑科学 | 14篇 |
能源动力 | 23篇 |
轻工业 | 22篇 |
水利工程 | 3篇 |
石油天然气 | 2篇 |
无线电 | 44篇 |
一般工业技术 | 106篇 |
冶金工业 | 57篇 |
原子能技术 | 6篇 |
自动化技术 | 34篇 |
出版年
2023年 | 5篇 |
2022年 | 8篇 |
2021年 | 9篇 |
2020年 | 13篇 |
2019年 | 8篇 |
2018年 | 12篇 |
2017年 | 7篇 |
2016年 | 18篇 |
2015年 | 9篇 |
2014年 | 12篇 |
2013年 | 30篇 |
2012年 | 28篇 |
2011年 | 27篇 |
2010年 | 13篇 |
2009年 | 20篇 |
2008年 | 20篇 |
2007年 | 15篇 |
2006年 | 15篇 |
2005年 | 19篇 |
2004年 | 14篇 |
2003年 | 6篇 |
2002年 | 7篇 |
2001年 | 6篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 9篇 |
1997年 | 10篇 |
1996年 | 8篇 |
1995年 | 10篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 9篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1973年 | 2篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有446条查询结果,搜索用时 15 毫秒
31.
32.
Non-accidental head injury, be it shaking, impact(s) or a combination of the two, is characterised by subdural and/or subarachnoid haemorrhages with retinal haemorrhages, but minimal or absent external cranio-facial trauma. The classical assault scenario depicts the infant being gripped around the head, face, chest and abdomen and shaken or being gripped by a limb and swung. This gripping might be expected to leave physical evidence in the form of bruising. A study was undertaken to establish the prevalence, distribution and pathological association of external bruising in 24 cases of fatal non-accidental head injury in children. At autopsy, 17 cases had new external bruises, 15 old external bruises and 13, a combination of both. However, seven (29%) cases showed no fresh external bruising and five (21%) showed no external bruising at all. Thus, external bruising may be absent in children with fatal intracranial injury. The face was shown to be the commonest site of bruising followed by the forehead and buttocks. Limb, chest and abdominal bruising were found to be uncommon. Retinal haemorrhages were confirmed in 23 (96%) cases. It is hypothesised that bruising, when present, may be a result of abuse in the form of punches and slaps rather than due to gripping during the assault. We discuss why gripping does not necessarily result in external bruising. 相似文献
33.
Electrochemical copolymerization of diphenylamine (DPA) with o‐chloroaniline (OCA) was performed in aqueous 4M sulfuric acid using the pulse potentiostatic method (PPSM). By employing the tunable parameters in PPSM, polymeric films were deposited under different conditions. Cyclic voltammetry was used for evaluating the characteristics of the deposited polymeric films. A suitable growth equation for the deposition of polymer, relating the charge associated for the film deposition and the pulse parameters in PPSM, was deduced. Various surface parameters are evaluated. The formation of copolymer during PPSM deposition was revealed through critical analysis of the results. The characteristic differences between the individual homopolymers, poly(diphenylamine) and poly(o‐chloroaniline) and the copolymer, poly(diphenylamine‐co‐o‐chloroaniline), were brought out. The copolymer was also synthesized through a chemical method and characterized through infrared and ultraviolet‐visible spectroscopic analysis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 389–397, 2003 相似文献
34.
Raj R. K. Joseph M. Aanandan C. K. Vasudevan K. Mohanan P. 《Antennas and Propagation, IEEE Transactions on》2006,54(12):3755-3762
A novel compact microstrip fed dual-band coplanar antenna for wireless local area network is presented. The antenna comprises of a rectangular center strip and two lateral strips printed on a dielectric substrate and excited using a 50 Omega microstrip transmission line. The antenna generates two separate resonant modes to cover 2.4/5.2/5.8 GHz WLAN bands. Lower resonant mode of the antenna has an impedance bandwidth (2:1 VSWR) of 330 MHz (2190-2520 MHz), which easily covers the required bandwidth of the 2.4 GHz WLAN, and the upper resonant mode has a bandwidth of 1.23 GHz (4849-6070 MHz), covering 5.2/5.8 GHz WLAN bands. The proposed antenna occupy an area of 217 mm2 when printed on FR4 substrate (epsivr=4.7). A rigorous experimental study has been conducted to confirm the characteristics of the antenna. Design equations for the proposed antenna are also developed 相似文献
35.
P. B. S. N. V. Prasad R. Vasudevan S. K. Seshadri 《Journal of Materials Science Letters》1992,11(21):1424-1425
36.
A. K. Vasudevan T. V. Mani A. D. Damodaran K. G. K. Warrier 《Journal of Materials Science Letters》1995,14(18):1317-1320
37.
X-ray diffraction profile studies on the filings of stoichiometric and off-stoichiometric compositions of Ni3Al alloys, with and without boron additions, were conducted to clarify some of the significant anomalies noticed in the literature.
The long-range order parameter was estimated as a function of temperature in all the four alloys from (1 0 0)/(2 0 0) and
(1 1 0)/(2 2 0) pairs of reflections. The L12 structure appears to attain a maximum stability at about 600 °C, around which temperature its order parameter was close to
the theoretical value. Above 600 °C, this structure becomes less stable and there appears to be formation of an additional
structure of a lower symmetry.
Also in the Materials Science Section, Faculty of Mechanical Engineering, University of Twente, Enschede, The Netherlands. 相似文献
38.
While debonding and subsequent pullout at fiber‐matrix interfaces can improve fracture toughness in ceramic nanocomposites, the magnitudes of these contributions are currently the subject of ongoing debate. To provide quantitative insight into these mechanisms, ceramic matrix nanocomposites were fabricated with a polymer‐derived ceramic matrix, using multiwalled carbon nanotubes (MWCNTs) that exhibit relatively long pullout lengths. In situ micromechanical pullout tests on individual MWCNTs were used to directly measure the strength of the fiber‐matrix interface. Similar pullout lengths were also observed in bulk and thin film composites, where the fracture toughness of the composite films was measured and found to be higher than that of the matrix material. The interfacial properties from the micromechanical test and the pullout lengths from the composite films were then used to estimate the energy release rates for fiber debonding and pullout. Based on the observed MWCNT and composite failure mechanisms, these results are discussed in terms of their relation to previous estimates of toughening in MWCNT‐ceramic nanocomposites, and in terms of design possibilities for further fracture toughness improvements. 相似文献
39.
S. Karthika Vasudevan Prathibha Mary K. A. Ann Vidyadharan Viji P. R. Biju N. V. Unnikrishnan 《Journal of Electronic Materials》2014,43(2):447-451
A sol–gel method was used to prepare titania-zirconia matrices doped with Sm3+/CdS nanocrystallites. The structural properties of the matrices were characterized using transmission electron microscopy (TEM), thermogravimetric analysis (TGA), differential thermal analysis (DTA), and Fourier-transform infrared spectroscopy studies. The thermal stability of the material was determined by TGA/DTA analysis. The absorption spectrum shows the characteristic peaks of the Sm3+ ions and the absorption peak corresponding to the CdS nanocrystallites. The optical bandgap and size of the CdS nanoparticles were calculated from the absorption spectrum. From TEM, the interplanar distance (d) was estimated to be 3.533 Å, which matches with the (1 0 0) plane of bulk CdS. The measurements yield a nanocrystallite size of around 7.8 nm. The optical absorption and emission spectra confirmed the formation of CdS nanoparticles along with samarium ions in the titania-zirconia matrices. The fluorescence intensity of the samarium ions was found to be greatly enhanced by codoping with CdS nanocrystallites. 相似文献
40.
Vasudevan PrathibhaS. Karthika Joseph CyriacC. Sudarasanakumar N.V. Unnikrishnan 《Materials Letters》2011,65(4):664-666
Anatase TiO2 nanocrystals in the TiO2- SiO2 matrix were prepared by the ultra hydroylsis sol-gel route. The samples were heat treated at 350 °C and 500 °C. The structural analyses of the samples were carried out using X-ray diffraction technique, Raman spectroscopy and Transmission electron microscopy. The size of the nanocrystals from the XRD spectra (8.3 nm) and TEM (5-8 nm) is well in agreement. The spacing for the crystal planes was also determined using the ImageJ program. The Raman peaks further confirmed the formation of only the anatase phase within the matrix. 相似文献