全文获取类型
收费全文 | 29877篇 |
免费 | 2665篇 |
国内免费 | 1567篇 |
专业分类
电工技术 | 3241篇 |
综合类 | 3351篇 |
化学工业 | 2552篇 |
金属工艺 | 1283篇 |
机械仪表 | 1731篇 |
建筑科学 | 5610篇 |
矿业工程 | 1909篇 |
能源动力 | 848篇 |
轻工业 | 1447篇 |
水利工程 | 1281篇 |
石油天然气 | 1647篇 |
武器工业 | 186篇 |
无线电 | 1961篇 |
一般工业技术 | 1811篇 |
冶金工业 | 1454篇 |
原子能技术 | 206篇 |
自动化技术 | 3591篇 |
出版年
2024年 | 111篇 |
2023年 | 343篇 |
2022年 | 651篇 |
2021年 | 713篇 |
2020年 | 735篇 |
2019年 | 668篇 |
2018年 | 589篇 |
2017年 | 787篇 |
2016年 | 880篇 |
2015年 | 1014篇 |
2014年 | 1718篇 |
2013年 | 1422篇 |
2012年 | 2040篇 |
2011年 | 2281篇 |
2010年 | 1790篇 |
2009年 | 1934篇 |
2008年 | 1768篇 |
2007年 | 2164篇 |
2006年 | 1952篇 |
2005年 | 1784篇 |
2004年 | 1464篇 |
2003年 | 1297篇 |
2002年 | 1078篇 |
2001年 | 915篇 |
2000年 | 744篇 |
1999年 | 623篇 |
1998年 | 450篇 |
1997年 | 419篇 |
1996年 | 353篇 |
1995年 | 335篇 |
1994年 | 262篇 |
1993年 | 172篇 |
1992年 | 144篇 |
1991年 | 106篇 |
1990年 | 78篇 |
1989年 | 75篇 |
1988年 | 55篇 |
1987年 | 51篇 |
1986年 | 24篇 |
1985年 | 14篇 |
1984年 | 23篇 |
1983年 | 16篇 |
1982年 | 6篇 |
1981年 | 9篇 |
1980年 | 18篇 |
1979年 | 8篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
81.
Reports an error in "Recovery of spatial alternation deficits following selective hippocampal destruction with kainic acid" by J. Patrick Kesslak and Fred H. Gage (Behavioral Neuroscience, 1986[Apr], Vol 100[2], 280-283). In the aforementioned article, the degrees of freedom reported in the Results section are incorrect. In the sixth paragraph on page 281, the second sentence should read as follows: Results of the ANOVA indicated a significant effect for surgical treatments. F(2, 25)=25.44, p1986-21445-001.) Examined whether the sympathetic ingrowth of superior cervical ganglion (SCG) fibers sprouting into the hippocampus following kainic acid (KA) lesion of CA3 and CA4 pyramidal cells in male Sprague-Dawley rats would contribute to behavioral recovery. 31 Ss were trained on a forced-choice task. After reaching criterion performance levels, Ss received either KA (8 nM/0.4 μl) or saline injections into the hippocampus and were again tested on the forced-choice task. Half of the Ss had their SCG removed 35 days after injections, and all were again tested on the forced-choice task. Analysis of variance (ANOVA) showed Ss receiving KA took significantly longer to reach criterion following injections. Removal of the SCG after recovery reintroduced the performance deficit of KA-treated Ss on the alternation task; no other group showed any effect for SCG removal. Results indicate that the SCG may have a modulatory effect in behavioral recovery, although other mechanisms may also be operating. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
82.
A novel current source inverter system interconnected to the single‐phase grid is proposed. It has the same construction as the conventional three‐phase current source inverter that is interconnected to the single‐phase three‐wire distribution system. Though the proposed circuit has no output transformer, it can be equivalently performed as the single‐phase double cascade inverter by diverting the pole transformer in the utility system. By controlling the appropriate scheme, the output currents can be obtained as the five‐level waveforms and their distortions can be decreased sufficiently. It is applied to the interactive electric energy storage system with batteries and the basic discharging characteristics are discussed experimentally. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(2): 50–61, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10380 相似文献
83.
制备低硫可膨胀石墨的研究 总被引:18,自引:3,他引:15
研究了以过二硫酸铵作氧化剂低硫可膨胀石墨的制备,找到了在较低温度下,制备低硫可膨胀石墨的最佳条件。即过二硫酸铵和石墨的重量比为15%;反应温度为55℃;反应时间为40min;硫酸浓度为98%;硫酸与石墨的重量比为4∶1,草酸和硝酸(浓度为65%)的重量比为7.5%时,所制得的可膨胀石墨含硫量为0.65%,膨胀容积为200mL/g可膨胀石墨。并且,其终端产品柔性石墨具有优良的力学性能和抗氧化性能。 相似文献
84.
介绍一种新的高阻测试方法,可满足对高达1×10^16Ω的测试要求。测试结果显示,对于1×10^13Ω重复误差优于±2%。高阻测试电路通过接口与6809微机配套使用,操作简便,读数直观,便于长时间重复测量。 相似文献
85.
介绍了间断式半热滑轨的研制和应用过程,以及经过节能技术改造,用新型半热滑轨代替老式滑轨的使用。实践表明,不但解决了以往的水梁漏水的问题,而且使线C级品率提高了3.39%,每年可增产3500t线材,吨钢热涌单耗降低0.14GJ,年创经济效益239万元。 相似文献
86.
In this work a treatment for surface preparation to improve mechanical resistance in adhesive bonding of plastic composites reinforced with fibres and metallic material, has been performed using an excimer laser. The following couplings have been selected to reproduce joints commonly used in the aerospace and automotive industry: CFC (carbon fibre composite) with CFC, CFC with Al 2024T3, Al 99% with Al 99%, GFC (glass fibre composite) with zinc-coated sheet in low carbon steel FeP01. The surfaces have been prepared using an excimer laser, adopting several values of laser parameters. The obtained surfaces have been examined by optical and scanning electron microscope: comparative measures of wetting and roughness have been performed to obtain an accurate characterisation and to select the proper finishes suitable to improve the mechanical resistance of the joints. The results obtained show that laser treatment always improves the final resistance of the joint; notable increases, and no significant surface damages have been highlighted. Better results have been obtained with the Al 99% with Al 99% joints which, with a low number of pulses treatment, have shown an increase of mechanical resistance up to the 70%. 相似文献
87.
88.
Eliichi Yamaguchi 《AI & Society》1990,4(2):147-154
In this paper I consider how the computer can or should be accepted in Japanese schools. The concept of teaching in Japan stresses learning from a long-term perspective. Whereas in the instructional technology, on which the CAI or the Tutoring System depends, step-by-step attainments in relatively short time are emphasized. The former is reluctant in using the computer, but both share the Platonic perspective which are goal-oriented. However, The Socratic teacher, who intends to activate students' innate disposition to be better, would find another way of teaching and use of the computer. 相似文献
89.
In this investigation we consider the formation of Cooper pairs near the oxygen-deficient sites in Y-Ba-Cu-O ceramic superconductors which would give rise to an energy-dependent potential as seen by conduction charge carriers. It is shown that Cooper pairs could be formed under such conditions, resulting in a supercurrent. We use the Bogoliubov transformation technique to calculate the energy gap, the energy difference, and the transition temperature of the model superconductor using certain data obtained from previous experiments. Numerical analysis shows that the superconducting current can be explained by the presence of such oscillating Cooper pairs. 相似文献
90.
In this work a real-time communication system using Arduino® microcontrollers, applied to electronic locking devices, is implemented. Model-Matching Control is used to achieve synchronization between transmitter and receiver Arduino® microcontrollers using only one transmission channel. Model-Matching Control is fed with dynamics from both Arduinos. Transmitter Arduino® is used also to generate in real-time an encrypted chaotic code key based on the Chen map. Receiver Arduino® recover in real-time the chaotic code key that is a binary signal key of an electronic locking device and where wireless communication is made between the two Arduinos using Bluetooth modules. System evaluation in terms of performance, randomness, and time complexity, are shown, as well as experimental results and some discussions are presented. 相似文献