全文获取类型
收费全文 | 161648篇 |
免费 | 6890篇 |
国内免费 | 4439篇 |
专业分类
电工技术 | 5735篇 |
技术理论 | 1篇 |
综合类 | 5931篇 |
化学工业 | 20070篇 |
金属工艺 | 8562篇 |
机械仪表 | 6514篇 |
建筑科学 | 6541篇 |
矿业工程 | 1622篇 |
能源动力 | 4298篇 |
轻工业 | 13628篇 |
水利工程 | 1961篇 |
石油天然气 | 2840篇 |
武器工业 | 591篇 |
无线电 | 22262篇 |
一般工业技术 | 27599篇 |
冶金工业 | 27369篇 |
原子能技术 | 1961篇 |
自动化技术 | 15492篇 |
出版年
2024年 | 355篇 |
2023年 | 1211篇 |
2022年 | 2432篇 |
2021年 | 3167篇 |
2020年 | 2456篇 |
2019年 | 2224篇 |
2018年 | 2729篇 |
2017年 | 2923篇 |
2016年 | 2893篇 |
2015年 | 3370篇 |
2014年 | 4782篇 |
2013年 | 8365篇 |
2012年 | 6849篇 |
2011年 | 8565篇 |
2010年 | 7468篇 |
2009年 | 7888篇 |
2008年 | 8134篇 |
2007年 | 7982篇 |
2006年 | 7333篇 |
2005年 | 6261篇 |
2004年 | 5293篇 |
2003年 | 4709篇 |
2002年 | 4407篇 |
2001年 | 4420篇 |
2000年 | 3847篇 |
1999年 | 3886篇 |
1998年 | 9969篇 |
1997年 | 6541篇 |
1996年 | 5139篇 |
1995年 | 3475篇 |
1994年 | 2991篇 |
1993年 | 2873篇 |
1992年 | 1744篇 |
1991年 | 1693篇 |
1990年 | 1584篇 |
1989年 | 1383篇 |
1988年 | 1228篇 |
1987年 | 894篇 |
1986年 | 910篇 |
1985年 | 936篇 |
1984年 | 814篇 |
1983年 | 709篇 |
1982年 | 708篇 |
1981年 | 683篇 |
1980年 | 584篇 |
1979年 | 486篇 |
1978年 | 416篇 |
1977年 | 533篇 |
1976年 | 962篇 |
1975年 | 301篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
113.
Glass columns (length 50 cm, i.d. 4 cm) containing 900 g of uranium ore waste were subjected to a three-step process: (1) acid drainage generation, (2) neutralization and precipitation treatment and, again, (3) acid drainage generation. In the first acid generation step, lasting about one year, different variables (pyrite addition, inoculation and irrigation solution) were tested by measuring effluent pH, redox potential, total iron and sulphate. Conditions of acid generation were satisfactorily reproduced, reaching stable pH values around 2.0 that were determined mainly by pyrite addition and the type of irrigation solution used (distilled water or ferrous sulphate). The neutralization and precipitation treatment consisted of alternating irrigations of a neutralizing solution (CaO saturated plus NaOH) and a precipitating solution (ferric sulphate saturated). This treatment caused accumulation of basic iron sulphate and iron oxide precipitates according to SEM studies. After this treatment, the barrier effect created by the reaction products was checked, using irrigation solutions similar to the first step. The effluents collected showed higher pH and lower redox potential, total iron and sulphate values than those observed before the treatment, evidencing inhibition of acid drainage generation. 相似文献
114.
介绍I/A’S系统在巨化热电厂八号50MW供热机组上应用实例,并从DCS系统的整体设计到实现的功能、控制效果等多方面进行了分折,总结了调试和运行经验。 相似文献
115.
A minimal integrated filter containing four MOS transistors as the only circuit elements is presented. Voltage tuning is used to set the cutoff frequency and band-edge peaking. A filter test chip occupies an active area of 0006mm2, has acutoff frequency of 40 MHz and dissipates 580W. 相似文献
116.
Tang Helen H. Y.; McNally Gavan P.; Richardson Rick 《Canadian Metallurgical Quarterly》2007,121(6):1421
The authors studied the role of gamma-aminobutyric acid (GABA) in 2 types of forgetting of fear in the developing rat. One type of forgetting studied was that observed after an intermediate retention interval (the "Kamin effect"); the other type studied was that observed after a longer interval (infantile amnesia). Rats were given pairings of an auditory conditioned stimulus with shock, and learned fear was assessed by freezing. Forgetting at an intermediate retention interval (1 hr) was not alleviated by the GABAA receptor partial inverse agonist FG7142 (0, 1, 5, or 10 mg/kg), whereas forgetting at a longer retention interval (48 hr) was alleviated. These results suggest that in the developing rat, forgetting observed at different retention intervals is mediated by different physiological mechanisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
117.
118.
Y. G. Wang H. Q. Ye K. H. Kuo X. J. Feng S. Z. Long G. L. Lao 《Journal of Materials Science》1991,26(23):6325-6330
The microstructures of unhydrated calcium aluminosulphate Ca4Al6SO16 and Ca3SrAl6SO16 have been studied by high-resolution electron microscopy (HREM). The results showed that twinning and twinned slabs could be introduced taking the [1 1 2] direction as the twin axis so that it seems to be coincident with the law of twinning formed in body-centred cubic structures. A previously reported superlattice with a repeat period twice that of the fundamental structure along the 〈1 1 0〉 direction has also been found in both matrix and twin variants. The close intergrowth of Ca3SrAl6SO16 and another phase, possibly Sr3Al2O6 existing as an inclusion between these two twin variants, was determined and clearly revealed by electron diffraction and HREM images. The coherent interphase boundaries and orientation relationship between them can also be deduced. 相似文献
119.
JaeHyuk Shin Ozturk C. Sakamoto S.R. Chiu Y.J. Dagli N. 《Microwave Theory and Techniques》2005,53(2):636-643
A novel traveling-wave electrode utilizing capacitively loaded T-rail elements was developed for low-voltage high-speed substrate-removed GaAs/AlGaAs electrooptic modulators. Electrodes with varying dimensions were fabricated and characterized. Electrode phase velocity, characteristic impedance, loss coefficient, and capacitive loading were extracted from the measured s-parameters up to 40 GHz. Electrode was also simulated using a finite-element solver. The measured and calculated electrode capacitance values were found to be in excellent agreement, showing that the electrode can be precisely designed. Approaches were outlined to provide a group velocity-matched very high-speed modulator electrode suitable for a low drive-voltage substrate-removed GaAs/AlGaAs electro-optic modulator 相似文献
120.