全文获取类型
收费全文 | 64988篇 |
免费 | 5181篇 |
国内免费 | 2956篇 |
专业分类
电工技术 | 3690篇 |
技术理论 | 7篇 |
综合类 | 4282篇 |
化学工业 | 11065篇 |
金属工艺 | 3603篇 |
机械仪表 | 3971篇 |
建筑科学 | 5512篇 |
矿业工程 | 1902篇 |
能源动力 | 1881篇 |
轻工业 | 4091篇 |
水利工程 | 1179篇 |
石油天然气 | 4593篇 |
武器工业 | 460篇 |
无线电 | 7197篇 |
一般工业技术 | 8077篇 |
冶金工业 | 3153篇 |
原子能技术 | 729篇 |
自动化技术 | 7733篇 |
出版年
2024年 | 228篇 |
2023年 | 1049篇 |
2022年 | 1748篇 |
2021年 | 2472篇 |
2020年 | 1911篇 |
2019年 | 1654篇 |
2018年 | 1876篇 |
2017年 | 2110篇 |
2016年 | 1924篇 |
2015年 | 2400篇 |
2014年 | 3244篇 |
2013年 | 3692篇 |
2012年 | 4126篇 |
2011年 | 4476篇 |
2010年 | 3929篇 |
2009年 | 3711篇 |
2008年 | 3658篇 |
2007年 | 3559篇 |
2006年 | 3610篇 |
2005年 | 3118篇 |
2004年 | 2114篇 |
2003年 | 1900篇 |
2002年 | 1670篇 |
2001年 | 1617篇 |
2000年 | 1682篇 |
1999年 | 1792篇 |
1998年 | 1408篇 |
1997年 | 1180篇 |
1996年 | 1061篇 |
1995年 | 947篇 |
1994年 | 779篇 |
1993年 | 562篇 |
1992年 | 439篇 |
1991年 | 339篇 |
1990年 | 316篇 |
1989年 | 228篇 |
1988年 | 177篇 |
1987年 | 109篇 |
1986年 | 107篇 |
1985年 | 61篇 |
1984年 | 41篇 |
1983年 | 26篇 |
1982年 | 33篇 |
1981年 | 22篇 |
1980年 | 13篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
22.
Flocculation morphology is a new concept that investigates the morphological characteristics of colloidal particles and coagulants in water during the flocculation process, and the influence that these characteristics have on flocculation process efficiency. This paper is a summary of advances in research on this topic over several years. Morphological characteristics of colloids in natural waters and different kinds of hydrolysed coagulants are investigated, and their effect on colloid stability, flocculation kinetics and efficiency is analysed. It is confirmed that the traditional theory has some deviations in coagulation of nonspherical particles, and these deviations are revised by the flocculation morphology model. Flocculation morphology can not only promote research about flocculation theory, but also instruct the production, application and flocculation control. It can be foreseen that more progress will be made in research and application of flocculation morphology in the near future. 相似文献
23.
24.
随着人们对建筑安全的日益重视 ,对建筑抗震要求的提高 ,国内外有关规范都对箍筋末端的设置作了明确规定 ,要求做成 135度弯钩。而在工程实践中 ,由于施工上的技术困难 ,很多工程都只设置成 90度弯钩。笔者提出的箍筋末端 135度弯钩二次就位法在基本不增加 90度弯钩施工难度与费用的基础上实现了 135度弯钩的施工 ,其法是可行的 相似文献
25.
Jiang Minhong Gu Zhengfei Cheng Gang 《中国稀土学报(英文版)》2005,23(6):723-723
Polymer matrix RE-Fe giant magnetostrictire composite (GMPC) was prepared using bonding and magnetic field forming technique, and magnetostriction of samples was measured for different compressive stress. The experimental results show thai there is certain compressive effect in GMPC. And the influence of compressive stress on magnetostriction of sample was investigated. It offers essential reference for application and device design of GMPC. 相似文献
26.
The effect of pressure on combustion and heat transfer is analyzed. The research is based on the basic combustion and heat
transfer theorem. A correction for the heat calculation method for pressurized furnace is made on the basis of the normal
pressure case. The correction takes the effect of pressurizing into account. The results show that the correction is reasonable
and the method is applicable to combustion and heat transfer of the marine supercharged boiler. 相似文献
27.
镍氢电池负极用低成本储氢合金的研究 总被引:1,自引:0,他引:1
研究了ABS型储氢合金在低Co含量条件下,随B组元替代元素Co,Al,Si等含量的变化对合金电化学性能的影响规律,同时研究了A组元中不同La/Ce比对合金电化学性能的影响情况。结果表明,随合金中Co含量的降低,合金的活化性能和放电容量得以改善,但合金的循环寿命下降也比较明显;在试验范围内,随Al元素的加入,合金的循环寿命得以改善,但材料的放电容量和活化性能均有所下降;随合金La/Ce比的降低,合金的放电容量略有下降,但其循环寿命和放电电压平台有较大提高。 相似文献
28.
Interfacial hybridization kinetics of oligonucleotides immobilized onto fused silica surfaces 总被引:3,自引:0,他引:3
Jiang Zeng Amer Almadidy James Watterson Ulrich J. Krull 《Sensors and actuators. B, Chemical》2003,90(1-3):68-75
Fused silica optical fibers have been used in an intrinsic mode optical configuration as biosensors for fluorescence based detection of hybridization of nucleic acids. In this work, the kinetics of hybridization of single-stranded oligonucleotides that were covalently immobilized were studied. The probe DNA was dT20, and the target was Fluorescein-labeled non-complementary (dT20) or complementary (dA20) oligonucleotide. Chronofluorimetric monitoring of the adsorption and hybridization processes was used to investigate oligonucleotide films of different density, in different salt concentrations, at temperatures of 25 and 40 °C, with the concentration of the target DNA being 0.005–0.1 μM. Mathematical models based on first- and second-order Langmuir adsorption have been examined to describe both the adsorption and the hybridization processes. Experimental data were processed using the models, and the hybridization kinetics were calculated. Hybridization kinetics on these optical fiber DNA sensors was found to be up to three orders faster than results presented for a number of other experiments using different immobilization chemistries. 相似文献
29.
30.
The simulation and analysis of S-shaped waveguide bend are presented.Bend radius larger than 30 mm assures less than 0.5 dB radiation loss for a 4-μm-wide silicon-on-insulator waveguide bend with 2-μm etch depth.Intersection angle greater than 20° provides negligible crosstalk (<-30 dB) and very low insertion loss.Any reduction in bend radius and intersection angle is at the cost of the degradation of characteristics of bent waveguide and intersecting waveguide, respectively. 相似文献