全文获取类型
收费全文 | 2090篇 |
免费 | 19篇 |
国内免费 | 98篇 |
专业分类
电工技术 | 51篇 |
综合类 | 20篇 |
化学工业 | 344篇 |
金属工艺 | 350篇 |
机械仪表 | 63篇 |
建筑科学 | 9篇 |
矿业工程 | 9篇 |
能源动力 | 264篇 |
轻工业 | 25篇 |
石油天然气 | 4篇 |
武器工业 | 1篇 |
无线电 | 158篇 |
一般工业技术 | 787篇 |
冶金工业 | 37篇 |
原子能技术 | 49篇 |
自动化技术 | 36篇 |
出版年
2024年 | 1篇 |
2023年 | 31篇 |
2022年 | 41篇 |
2021年 | 39篇 |
2020年 | 25篇 |
2019年 | 38篇 |
2018年 | 41篇 |
2017年 | 38篇 |
2016年 | 33篇 |
2015年 | 43篇 |
2014年 | 72篇 |
2013年 | 109篇 |
2012年 | 111篇 |
2011年 | 250篇 |
2010年 | 131篇 |
2009年 | 140篇 |
2008年 | 144篇 |
2007年 | 119篇 |
2006年 | 104篇 |
2005年 | 82篇 |
2004年 | 73篇 |
2003年 | 97篇 |
2002年 | 58篇 |
2001年 | 31篇 |
2000年 | 44篇 |
1999年 | 41篇 |
1998年 | 47篇 |
1997年 | 46篇 |
1996年 | 42篇 |
1995年 | 23篇 |
1994年 | 14篇 |
1993年 | 14篇 |
1992年 | 15篇 |
1991年 | 12篇 |
1990年 | 16篇 |
1989年 | 10篇 |
1988年 | 9篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有2207条查询结果,搜索用时 0 毫秒
1.
化学镀非晶态Ni—B合金的研究 总被引:1,自引:0,他引:1
本文通过化学镀方法在铜和钢上沉积非晶态Ni-B合金。着重讨论了还原剂浓度、络合剂浓度对化学镀沉积速率的影响;分析了它的耐蚀原因和其显微硬度随退火温度的变化情况并就其应用和发展略作说明。 相似文献
2.
采用X射线衍射分析技术,研究了脉冲化学镀非晶态Ni-P合金的原子分布和函数,得出其短程有序原子集团的尺度为0.754nm,约为熔体激冷法获得的非晶态Ni-P合金短程有序畴的1/2。并利用脉冲化学沉积非晶态合金的微机制择这一结果进行了解释。 相似文献
3.
Flash-lamp annealing (FLA) on a millisecond time scale has been shown to be a promising tool in the preparation of high-quality semiconducting materials. The process imposes time varying through-thickness temperature profiles on the substrates being processed, and consequently thermal stresses. A combined thermal and optical model has been developed to predict the substrate temperature distribution and this model has been linked to a structural model to compute stresses and deflections. The paper shows how these models can be used to explore process conditions in flash lamp annealing, with particular regard to the annealing of ion implants in silicon and the crystallization of amorphous silicon layers on glass substrates. 相似文献
4.
This paper presents a highly stable steady-state torque control system with a feedback of a secondary current signal. The torque control system is constructed with a feedback of the secondary current (I2) signal using a quick response magnetic-field sensor constructed with an amorphous core multivibrator bridge, which can solve the secondary resistance change problem for temperature variation in the IM. Moreover, we added a state feedback to the system to improve the response speed for the unit step function of a torque order. The I2 sensor method has advantages especially at a low-speed range, in which conventional method using an integrator shows control errors. 相似文献
5.
A theoretical model is presented to describe the effect of ion beam bombardment rate on the formation of tetrahedral amorphous carbon (ta-C) films. The critical ion energy, Ec, corresponding to a 50% sp3 content in the films, is found to be dependent on both the effective thermal resistance and the ion beam bombardment rate. In the model, the ‘window’ width in the ion energy scale for the formation of ta-C material increases with decreasing deposition rate and with a reduction in the effective thermal resistance, until limited by lower and upper boundary thresholds. Experimental data are reproduced by the model. The plasmon energy, which correlates with sp3 fraction, is found experimentally of be higher for lower deposition rate and smaller effective thermal resistance. Data points for high sp3 content ta-C films deposited on silicon substrates at room temperature occupy a region in the ion energy-deposition rate (E-r) diagram similar to that predicated from the theory. 相似文献
6.
The determination of the Young’s modulus and damping coefficient Q−1 by means of non-destructive vibrating techniques has been applied to bulk and coated industrial materials. Extensions of a previous analytic model of composite beam allow to determine accurately the macroscopic modulus of each component of multilayered structural materials as coated superalloys or nitride-hardened steels. Furthermore, the study of glasses and polymers has been investigated. An attempt of normalisation of the modulus versus temperature curves allows to establish master curves depending on the specific structure, from metallic glasses to polymeric glasses. Finally a comparison of dynamical modulus and Q−1 values measured between resonant (>1 kHz) and subresonant techniques (10−3 to 10 Hz) in relation to the loading frequencies applied in real conditions has been under folder. For metallic materials such as forged or rolled titanium alloys, the brittle-to-fragile transition occurs abruptly or smoothly with a shift of 300 K following the range of excitation frequencies. 相似文献
7.
The effect of crystallisation on the glass transition temperature and enthalpic relaxation in poly(ether ether ketone) (PEEK) has been investigated. The increase in glass transition temperature and the activation enthalpy of ageing is explained in terms of the amorphous phase being constrained by the crystallites. The extent of enthalpic relaxation with time has been analysed in terms of the Cowie-Ferguson model and the β value was found to be dependent on both temperature and the crystalline morphology, changes in the co-operativity of the relaxations are used to explain this observation. 相似文献
8.
9.
Comparison of the toughening behavior of nylon 6 versus an amorphous polyamide using various maleated elastomers 总被引:1,自引:0,他引:1
J.J. Huang 《Polymer》2006,47(2):639-651
The toughening effect of two types of elastomers based on ethylene/α-olefin copolymers, viz, an ethylene/propylene copolymer (EPR) with its maleated version, EPR-g-MA, and an ethylene/1-octene copolymer (EOR) with its maleated versions, EOR-g-MA-X% (X=0.35, 1.6, 2.5), for two classes of polyamides: semi-crystalline nylon 6 versus an amorphous polyamide (Zytel 330 from DuPont), designated as a-PA, was explored. The results are compared with those reported earlier based on a styrenic triblock copolymer having a hydrogenated midblock, SEBS, and its maleated version, SEBS-g-MA, elastomer system. Izod impact strength was examined as a function of rubber content, rubber particle size and temperature. All three factors influence the impact behavior considerably for the two polyamide matrices. The a-PA is found to require a somewhat lower content of rubber for toughening than nylon 6. Very similar optimum ranges of rubber particle sizes were observed for ternary blends of EOR-g-MA/EOR with each of the two polyamides while blends based on mixtures of EPR-g-MA/EPR and SEBS-g-MA/SEBS (where the total rubber content is 20% by weight) show only an upper limit for a-PA but an optimum range of particle sizes for nylon 6 for effective toughening. Higher EPR-g-MA contents lead to lower ductile-brittle transition temperatures (Tdb) as expected; however, a-PA binary blends with EPR-g-MA have a much lower Tdb than do nylon 6 blends when the content of the maleated elastomer is not high. A minimum in plots of ductile-brittle transition temperature versus particle size appears for ternary blends of each of the matrices with EOR-g-MA/EOR; blends based on SEBS-g-MA/SEBS, in most cases, show higher ductile-brittle transition temperatures, regardless of the matrix. However, blends with EPR-g-MA/EPR show comparable Tdb with those based on EOR-g-MA/EOR for the amorphous polyamide but show the lowest ductile-brittle transition temperatures for nylon 6 within the range of particle sizes examined. For the blends with a bimodal size distribution, the global weight average rubber particle size is inappropriate for correlating the Izod impact strength and ductile-brittle transition temperature. In general, trends for this amorphous polyamide are rather similar to those of semi-crystalline nylon 6. 相似文献
10.
Yasushi Sobajima Kunihiro Mori Masahiro Tsukamoto Norimitsu Yoshida Masao Takahashi Hikaru Kobayashi Shuichi Nonomura 《Solar Energy Materials & Solar Cells》2005,85(2):240-187
Effects of cyanide (CN) treatment with hydrogenated amorphous silicon (a-Si:H) films have been investigated. The decrease of ΔV/V was observed in cyanide treated a-Si:H films and the successive thermal annealing at 200°C after CN treatment induced the further reduction of the ΔV/V. XPS spectra show the indirect evidence that the cyanide species is present within 10 nm from the hydrogenated amorphous silicon surface. The results of CN treatment with a-Si:H solar cells are demonstrated. 相似文献