全文获取类型
收费全文 | 1637篇 |
免费 | 65篇 |
国内免费 | 125篇 |
专业分类
电工技术 | 22篇 |
综合类 | 25篇 |
化学工业 | 238篇 |
金属工艺 | 224篇 |
机械仪表 | 46篇 |
建筑科学 | 3篇 |
矿业工程 | 3篇 |
能源动力 | 89篇 |
轻工业 | 35篇 |
水利工程 | 5篇 |
石油天然气 | 5篇 |
武器工业 | 1篇 |
无线电 | 232篇 |
一般工业技术 | 536篇 |
冶金工业 | 101篇 |
原子能技术 | 63篇 |
自动化技术 | 199篇 |
出版年
2023年 | 25篇 |
2022年 | 20篇 |
2021年 | 36篇 |
2020年 | 37篇 |
2019年 | 35篇 |
2018年 | 43篇 |
2017年 | 48篇 |
2016年 | 56篇 |
2015年 | 53篇 |
2014年 | 86篇 |
2013年 | 86篇 |
2012年 | 121篇 |
2011年 | 160篇 |
2010年 | 116篇 |
2009年 | 97篇 |
2008年 | 97篇 |
2007年 | 106篇 |
2006年 | 84篇 |
2005年 | 45篇 |
2004年 | 61篇 |
2003年 | 48篇 |
2002年 | 34篇 |
2001年 | 26篇 |
2000年 | 35篇 |
1999年 | 41篇 |
1998年 | 53篇 |
1997年 | 39篇 |
1996年 | 22篇 |
1995年 | 25篇 |
1994年 | 15篇 |
1993年 | 16篇 |
1992年 | 17篇 |
1991年 | 14篇 |
1990年 | 13篇 |
1989年 | 4篇 |
1988年 | 7篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1975年 | 2篇 |
排序方式: 共有1827条查询结果,搜索用时 15 毫秒
71.
N. Rodriguez A. Portavoce J. Delalleau C. Grosjean C. Girardeaux 《Thin solid films》2010,518(17):5022-5027
Arsenic (As) and phosphorus (P) implantations are concurrently used to create the n-zones of recent microelectronic device pn-junctions. We studied the As-P codiffusion effect on the junction depths during the dopant activation process. As diffusion is accelerated during codiffusion. The acceleration magnitude depends on As concentration and varies during annealing time. Contrasting with usual transient-enhanced-diffusion phenomena, a time delay can be observed before As diffusion acceleration occurs. P diffusion shows no specific modification due to codiffusion. Its diffusion behavior can be understood considering the usual Fermi level and electrical effects linked to the time evolution of the two dopant distributions. The behavior of As during codiffusion is discussed using finite element simulations. 相似文献
72.
The effects of precursor and calcination temperature on the nano morphology of ruthenium dioxide on titanium, prepared from thermal decomposition of aqueous salt solutions were investigated. Transmission electron microscopy, X-ray diffraction, gas porosimetry and cyclic voltammetry showed that lower calcination temperature yielded smaller crystallites. The crystallites were between 6 and 22 nm in diameter. When using ruthenium nitrosyl nitrate the firing temperature had a large impact on the grain size, but for chloride there was only a minor effect in the temperature range 350-550 °C. 相似文献
73.
Miklós Serényi Cesare Frigeri Zsolt Szekrényes Katalin Kamarás Lucia Nasi Attila Csik Nguyen Quoc Khánh 《Nanoscale research letters》2013,8(1):84
Differently hydrogenated radio frequency-sputtered a-Si layers have been studied by infrared (IR) spectroscopy as a function of the annealing time at 350°C with the aim to get a deeper understanding of the origin of blisters previously observed by us in a-Si/a-Ge multilayers prepared under the same conditions as the ones applied to the present a-Si layers. The H content varied between 10.8 and 17.6 at.% as measured by elastic recoil detection analysis. IR spectroscopy showed that the concentration of the clustered (Si-H)n groups and of the (Si-H2)n (n ≥ 1) polymers increased at the expense of the Si-H mono-hydrides with increasing annealing time, suggesting that there is a corresponding increase of the volume of micro-voids whose walls are assumed from literature to be decorated by the clustered mono-hydride groups and polymers. At the same time, an increase in the size of surface blisters was observed. Also, with increasing annealing time, the total concentration of bonded H of any type decreases, indicating that H is partially released from its bonds to Si. It is argued that the H released from the (Si-H)n complexes and polymers at the microvoid surfaces form molecular H2 inside the voids, whose size increases upon annealing because of the thermal expansion of the H2 gas, eventually producing plastic surface deformation in the shape of blisters. 相似文献
74.
In this work, we investigated the effects of quantum dot (QD) annealing (as-grown, 600°C-annealed, and 750°C-annealed) on the preliminary performances of 1.3-μm InAs-InGaAs-GaAs quantum dot electroabsorption modulators (QD-EAMs). Both extinction ratio and insertion loss were found to vary inversely with the annealing temperature. Most importantly, the 3-dB response of the 750°C-annealed lumped-element QD-EAM was found to be 1.6 GHz at zero reverse bias voltage - the lowest reverse bias voltage reported. We believe that this work will be beneficial to researchers working on on-chip integration of QD-EAMs with other devices since energy consumption will be an important consideration. 相似文献
75.
Vijaya Agarwala K. G. Satyanarayana R. C. Agarwala 《Materials Science and Engineering: A》1999,270(2):3897
With a view to developing a new metal–metal cast composite material as a possible substitute for ferrous materials in wear resistant applications, Al alloy (LM11) is reinforced with mild steel (ms) wires and it is heat treated to get ‘reaction interface’ (RI). Microhardness, tensile properties and wear characteristics of the matrix, as-cast and heat treated composites have been determined. While microhardness of the composite showed variation from 150 to 45 VHN across the interface in the as-cast composite, annealed (500–525°C) composite showed a microhardness of 350–420 VHN at the interface indicating the effectiveness of the heat treatment. It is seen that the % improvement in wear resistance increased with increase in number of wires when embedded in the aluminium alloy matrix. Further imrpovement of about 30% was observed when heat treated at 500°C for 15 h. These results have been discussed in terms of wetting between ms wires and the matrix, particularly the increase of hardness and tensile strength to the formation of ‘reaction interface’ due to annealing. The width of the interface increased with annealing time and temperature and the kinetics of reaction followed logarithmic and parabolic growth rate. The activation energy for the formation of intermetallics constituting the reaction interface is found to be 20.7 KJ mol−1. From the measured hardness and ultimate tensile strength of the constituents and composites an empirical relation was deduced. 相似文献
76.
Blends of amorphous and crystalline polylactides with poly(methyl methacrylate) and poly(methyl acrylate): a miscibility study 总被引:5,自引:0,他引:5
Blends of amorphous and crystalline polylactides (PDLA and PLLA) with poly(methyl methacrylate) (PMMA) and poly(methyl acrylate) (PMA) have been prepared. Thermal behaviour and miscibility of these blends along the entire composition interval were studied by differential scanning calorimetry (d.s.c.). The results were compared with those obtained by dynamic mechanical analysis (DMTA). Only one Tg was found in PDLA/PMA and PDLA/PMMA blends, indicating a high degree of miscibility in both systems. Nevertheless, the PDLA/PMMA blend presented enlargements of the Tg width at high PMMA contents. In this case, additional evidence of complete miscibility was obtained by studying the evolution of the enthalpic recovery peaks which appear after different thermal annealing treatments. When the polylactide used was semicrystalline (PLLA), once the thermal history of the blends had been destroyed, crystallization of PLLA was disturbed in both blends PLLA/PMMA and PLLA/PMA, but in a rather different fashion: in the first case crystallization was almost prevented while in the second one it was favoured. This behaviour was explained in terms of the effect of the higher stiffness as indicated by the value of Tg for PMMA compared to that for PMA. 相似文献
77.
Creation and annealing of light-induced defects and their effect on photocarrier lifetime have been studied at 120 and 300 K using constant photocurrent method (CPM) and steady-state photoconductivity measurements. A hysteresis-like relation is observed between photoconductivity and light-induced defect density. This relation depends on both degradation temperature and light intensity used for the degradation. A broad, resembling a two-component distribution of defect annealing activation energies together with distribution of recombination coefficients account for the observed changes at 120 K. On the other hand, these distributions are narrower and sharply peaked at about 1 eV for the 300 K measurements. Results indicate that defects which are created at the earlier stages of the illumination have smaller annealing activation energies and higher recombination coefficient (capture cross-section) and these are better recombination centers than the defects with higher annealing activation energies. 相似文献
78.
79.
S.P. Nehra M.K. Jangid Subodh Srivastava Anil Kumar Balram Tripathi M. Singh Y.K. Vijay 《International Journal of Hydrogen Energy》2009,34(17):7306
Bilayer thin films of diluted magnetic semiconductor CdTe/Mn have been prepared using vacuum thermal evaporation method at pressure of 10−5 torr. Annealing of bilayer thin films has been performed in atmospheric condition at constant temperature 400 °C for 1 hour. Hydrogenation of as-grown and annealed bilayer thin films has been performed by keeping these in hydrogenation cell. Structural characteristics of as-grown and heat treated thin films have been performed by X-ray diffractometer. Current–voltage characteristics of both as-grown hydrogenated and annealed hydrogenated bilayer thin films have been studied to find out the effect of hydrogenation. Surface topography of as-grown and annealed bilayer thin films has been confirmed by optical microscopy. 相似文献
80.
针对大中型电机在使用过程中暴露出来的一些质量问题,着重分析了产生这些质量问题的原因,阐述了电机主要结构件进行消除应力退火的作用及工艺对提高产品质量、延长电机使用寿命有一定意义。 相似文献