全文获取类型
收费全文 | 48708篇 |
免费 | 5995篇 |
国内免费 | 3176篇 |
专业分类
电工技术 | 4405篇 |
技术理论 | 2篇 |
综合类 | 3786篇 |
化学工业 | 9917篇 |
金属工艺 | 4635篇 |
机械仪表 | 1993篇 |
建筑科学 | 2217篇 |
矿业工程 | 905篇 |
能源动力 | 2389篇 |
轻工业 | 3189篇 |
水利工程 | 1466篇 |
石油天然气 | 1952篇 |
武器工业 | 412篇 |
无线电 | 6942篇 |
一般工业技术 | 6183篇 |
冶金工业 | 3398篇 |
原子能技术 | 469篇 |
自动化技术 | 3619篇 |
出版年
2024年 | 262篇 |
2023年 | 960篇 |
2022年 | 1409篇 |
2021年 | 1708篇 |
2020年 | 1865篇 |
2019年 | 1725篇 |
2018年 | 1580篇 |
2017年 | 1861篇 |
2016年 | 1983篇 |
2015年 | 1935篇 |
2014年 | 2685篇 |
2013年 | 3029篇 |
2012年 | 3237篇 |
2011年 | 3404篇 |
2010年 | 2429篇 |
2009年 | 2686篇 |
2008年 | 2519篇 |
2007年 | 2984篇 |
2006年 | 2778篇 |
2005年 | 2313篇 |
2004年 | 1916篇 |
2003年 | 1903篇 |
2002年 | 1621篇 |
2001年 | 1424篇 |
2000年 | 1261篇 |
1999年 | 983篇 |
1998年 | 870篇 |
1997年 | 786篇 |
1996年 | 620篇 |
1995年 | 580篇 |
1994年 | 513篇 |
1993年 | 340篇 |
1992年 | 351篇 |
1991年 | 259篇 |
1990年 | 236篇 |
1989年 | 226篇 |
1988年 | 116篇 |
1987年 | 72篇 |
1986年 | 72篇 |
1985年 | 50篇 |
1984年 | 54篇 |
1983年 | 34篇 |
1982年 | 40篇 |
1981年 | 29篇 |
1980年 | 26篇 |
1979年 | 9篇 |
1964年 | 10篇 |
1959年 | 9篇 |
1957年 | 12篇 |
1951年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
1.
2.4GHz动态CMOS分频器的设计 总被引:1,自引:0,他引:1
对现阶段的主流高速CMOS分频器进行分析和比较,在此基础上设计一种采用TSPC(truesingle phase clock)和E-TSPC(extended TSPC)技术的前置双模分频器电路.该分频器大大提高了工作频率,采用0.6μm CMOS工艺参数进行仿真的结果表明,在5V电源电压下,最高频率达到3GHz,功耗仅为8mW. 相似文献
2.
Navab SinghAuthor Vitae Moitreyee Mukherjee-RoyAuthor VitaeSohan Singh MehtaAuthor Vitae 《Microelectronics Journal》2003,34(4):237-245
The patterning of contact holes by selecting out-of-focus image plane (defocus) using attenuated phase shift masks (APSM) has been studied. Defocus is found to enhance the image modulation at low partial coherence for contact holes with negative local average of mask function. Semi-dense holes up to 130 nm in 8% APSM have been printed by 0.5 μm defocus at a partial coherence of 0.31 using KrF scanner with highest numerical aperture of 0.68. However, these holes were closed with in-focus imaging. Defocus is also found to be beneficial for patterning the pitches that have extensive side lobes with in-focus imaging. 相似文献
3.
4.
Studies on the deactivations and initiations of gas phase polymerizations of 1,3‐butadiene have been achieved by Monte Carlo simulation. Initiation and deactivation control the reaction before and after the peak of the polymerization rate, respectively. The influence of polymerization temperature has been studied. Monte Carlo modeling of polymerization kinetics and mechanism was confirmed by the agreement of experimental data and simulation results of polymerizations run with a temporary evacuation of monomer. The balance of catalysts and active chains is established by both initiation and chain transfer reactions with cocatalyst, which causes a ‘pseudo‐stability’ stage. © 2003 Society of Chemical Industry 相似文献
5.
6.
机械合金化Fe-Ni粉末的相结构 总被引:1,自引:0,他引:1
使用XRD和Moessbauer等方法,研究了在Ar气氛下机械合金化Fe—Ni粉末相结构的变化.结果表明,在机械合金化Fe64-Ni36粉末过程中,fcc相的数量随着球磨时间的增加先增加然后减少,与加乙醇球磨Fe64-Ni36的情形相同.当Ni的含量(原子分数)大于50%时,有fcc相、顺磁相和FeNi3形成,当Ni的含量低于50%时,bcc相的数量随着Ni含量减少而增加.Moessbauer谱的结果表明,因球磨时间或Fe、Ni比例的不同,Fe—Ni球磨粉末固溶体具有不同结构的原子配比。 相似文献
7.
H. Yamamoto N. Heyamoto T. Matsui N. Murayama J. Shibata 《International Journal of Thermophysics》2003,24(5):1385-1394
Polyvinylalcohol (PVA) polymer gel is a temperature sensitive polymeric gel, with a critical transition temperature (with H2O) of 310 K. At higher than 310 K, this temperature sensitive polymer gel shrinks because of discharging water, whereas at lower temperatures, the gel swelled because of absorbing water. The reversibility of the gel's volume change was confirmed by temperature swing. The adsorption behavior of an organic compound onto the PVA polymer gel in water was tested at various temperatures. The amount of adsorbed organic compound increased remarkably at temperatures higher than about 310 K. Then, it was confirmed that the organic compound in PVA polymer gel could be reversibly adsorbed and desorbed by a temperature change between 293 and 323 K. The mechanism of adsorption of the organic compound onto the PVA polymer gel could be explained by hydration and dehydration of polymer gel. 相似文献
8.
The present empirical investigation had a 3-fold purpose: (a) to cross-validate L. R. Offermann, J. K. Kennedy, and P. W. Wirtz's (1994) scale of Implicit Leadership Theories (ILTs) in several organizational settings and to further provide a shorter scale of ILTs in organizations; (b) to assess the generalizability of ILTs across different employee groups, and (c) to evaluate ILTs' change over time. Two independent samples were used for the scale validation (N1 = 500 and N2 = 439). A 6-factor structure (Sensitivity, Intelligence, Dedication, Dynamism, Tyranny, and Masculinity) was found to most accurately represent ELTs in organizational settings. Regarding the generalizability of ILTs, although the 6-factor structure was consistent across different employee groups, there was only partial support for total factorial invariance. Finally, evaluation of gamma, beta, and alpha change provided support for ILTs' stability over time. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
9.
The In-Sn-Ni alloys of various compositions were prepared and annealed at 160°C and 240°C. No ternary compounds were found;
however, most of the binary compounds had extensive ternary solubility. There was a continuous solid solution between the
Ni3Sn phase and Ni3In phase. The Sn-In/Ni couples, made of Sn-In alloys with various compositions, were reacted at 160°C and 240°C and formed
only one compound for all the Sn-In alloys/Ni couples reacted up to 8 h. At 240°C, Ni28In72 phase formed in the couples made with pure indium, In-10at.%Sn and In-11at.%Sn alloys, while Ni3Sn4 phase formed in the couples made of alloys with compositions varied from pure Sn to In-12at.%Sn. At 160°C, except in the
In/Ni couple, Ni3Sn4 formed by interfacial reaction. 相似文献
10.
张鉴 《中国有色金属学会会刊》2002,12(1):120-126
Based on the principle of annexation and phase diagrams, the structural units of In-Pb-Sb and In-Bi-Pb melts were determined, and their calculating models of mass action concentrations were formulated. Calculated results agree well with practical values, which in turn show that the models deduced can reflect the structural realities of corresponding melts and the principle of annexation is applicable not only to some binary metallic melts, but also to ternary metallic melts. 相似文献