全文获取类型
收费全文 | 116444篇 |
免费 | 14124篇 |
国内免费 | 8558篇 |
专业分类
电工技术 | 10686篇 |
技术理论 | 5篇 |
综合类 | 10765篇 |
化学工业 | 15483篇 |
金属工艺 | 7173篇 |
机械仪表 | 8033篇 |
建筑科学 | 9397篇 |
矿业工程 | 4556篇 |
能源动力 | 3518篇 |
轻工业 | 10071篇 |
水利工程 | 3567篇 |
石油天然气 | 4782篇 |
武器工业 | 1667篇 |
无线电 | 13955篇 |
一般工业技术 | 11223篇 |
冶金工业 | 4533篇 |
原子能技术 | 1841篇 |
自动化技术 | 17871篇 |
出版年
2024年 | 748篇 |
2023年 | 2124篇 |
2022年 | 4636篇 |
2021年 | 6215篇 |
2020年 | 4688篇 |
2019年 | 3349篇 |
2018年 | 3682篇 |
2017年 | 4250篇 |
2016年 | 3638篇 |
2015年 | 5712篇 |
2014年 | 7178篇 |
2013年 | 8260篇 |
2012年 | 10061篇 |
2011年 | 10332篇 |
2010年 | 9399篇 |
2009年 | 9028篇 |
2008年 | 8795篇 |
2007年 | 8156篇 |
2006年 | 7027篇 |
2005年 | 5687篇 |
2004年 | 3916篇 |
2003年 | 2512篇 |
2002年 | 2348篇 |
2001年 | 1983篇 |
2000年 | 1664篇 |
1999年 | 986篇 |
1998年 | 481篇 |
1997年 | 430篇 |
1996年 | 374篇 |
1995年 | 302篇 |
1994年 | 245篇 |
1993年 | 178篇 |
1992年 | 122篇 |
1991年 | 119篇 |
1990年 | 80篇 |
1989年 | 63篇 |
1988年 | 58篇 |
1987年 | 39篇 |
1986年 | 40篇 |
1985年 | 17篇 |
1984年 | 14篇 |
1983年 | 7篇 |
1982年 | 16篇 |
1981年 | 18篇 |
1980年 | 54篇 |
1979年 | 28篇 |
1978年 | 4篇 |
1965年 | 7篇 |
1959年 | 24篇 |
1951年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
81.
82.
Young Sil Jeon Jing Lei Ji-Heung Kim 《Journal of Industrial and Engineering Chemistry》2008,14(6):726-731
This study examined the removal of some basic dyes, such as Methylene Blue, Malachite Green and Methyl Orange, using alginate or alginate/polyaspartate composite gel beads. The adsorption of dyes from aqueous solutions at 25 °C was examined using a batch sorption technique. The effects of CaCl2 and the dye concentration on the adsorption were examined. Type-S adsorption isotherms were obtained, which is characteristic of a weak solute–solid interaction. The ionic interaction between the dye molecule and gel matrix appears to be responsible for the efficient adsorption of cationic dyes in this system. These results suggest that an alginate/polyaspartate gel can be used as an effective sorbent for water pollutants such as dyes, and the immobilization of these organic contaminants in the hydrogels from wastewater can solve one of the most important environmental problems in the related industry. 相似文献
83.
84.
Lei Liu Ying Kong Hong Xu Jin P. Li Jin X. Dong Zhi Lin 《Microporous and mesoporous materials》2008,115(3):624-628
A three-dimensional zinc phosphate compound with DFT topology, designated as ZnPO4-EU1, has been synthesized by an ionothermal approach from the system HF-ZnO–P2O5-choline chloride-imidazolidone. Ethylenediamine, derived from decomposition of the imidazolidone component of the deep-eutectic solvent (DES) itself, is delivered to the synthesis and serves as an appropriate template for ZnPO4-EU1. Experiments in which the synthesis conditions were varied showed that ZnPO4-EU1 may be prepared over a wide molar ratio of P/Zn = 0.55–13.0. Powder X-ray diffraction patterns have been obtained at intervals to track the crystallization process of this material. The experimental data show that Zn3(PO4)2 · 4H2O (a dense phase) was first isolated from the DES after reaction for 1 h. Subsequently, the pure phase of ZnPO4-EU1 was obtained with increasing crystallization time from 12 h to 72 h. The experimental results show that the nucleation and crystallization take place with relatively low levels of solvent degradation, demonstrating that zinc phosphate with a three-dimensional framework can be synthesized by in situ generation of an appropriate template using an unstable DES at high temperatures (150–200 °C). 相似文献
85.
A high-power and high-repetition-rate passively Q -switched ytterbium-doped single-mode double-clad fiber laser was built using a Cr4+:YAG saturable absorber (SA). Two different SAs with initial transmissions of Tomicron = 30% and Tomicron = 50% were studied. At the maximum coupled pump power of 9.8 W, an output power of 4.7 W, pulse duration of 143 ns, pulse repetition rate of 253 KHz, pulse energy of 18.5 muJ, and slope efficiency of 49% were obtained with the Tomicron = 30% SA. 相似文献
86.
Alia-Klein Nelly; Goldstein Rita Z.; Tomasi Dardo; Zhang Lei; Fagin-Jones Stephanie; Telang Frank; Wang Gene-Jack; Fowler Joanna S.; Volkow Nora D. 《Canadian Metallurgical Quarterly》2007,7(4):735
Reports an error in "What is in a word? No versus Yes differentially engage the lateral orbitofrontal cortex" by Nelly Alia-Klein, Rita Z. Goldstein, Dardo Tomasi, Lei Zhang, Stephanie Fagin-Jones, Frank Telang, Gene-Jack Wang, Joanna S. Fowler and Nora D. Volkow (Emotion, 2007[Aug], Vol 7[3], 649-659). The supplemental materials link should appear as follows: http://dx.doi.org/10.1037/1528-3542.7.3.649.supp. (The following abstract of the original article appeared in record 2007-11660-018.) The words "No" and "Yes" are involved in conditioning to prohibit or encourage behavior, respectively. The authors, therefore, hypothesized that these words would be attributed to endogenous valence, activating neuronal circuits involved with valence and emotional control. Functional MRI (fMRI) at 4 Tesla was used to record regional brain activity while participants were exposed to emphatic vocalizations of the words. Results showed that No and Yes were associated with opposite brain-behavior responses; while No was negatively valenced, produced slower response times, and evoked a negative signal in the right lateral orbitofrontal cortex (OFC), Yes was positively valenced, produced faster response times, and evoked a positive signal in a contiguous region of the OFC. Attribution of negative valence to No and trait anger control were associated with increased responsivity of the OFC to No. Inasmuch as sensitivity to the prohibitive command No develops during childhood through interaction with primary caregivers as the first social objects, our findings may implicate the lateral OFC in the neurobiology of emotion regulation and subsequent social development. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
87.
88.
对在五坐标数控加工中心上铣制三元流叶轮时出现的叶轮附面尺寸误差问题,进行了详细分析,并提出了问题的解决方法,有效地避免了加工中产生的超差。 相似文献
89.
S135钻杆钢在钻井液中的氧腐蚀行为 总被引:4,自引:0,他引:4
基于系统的理论分析和现场腐蚀产物的XRD分析,揭示了S135钻杆钢在3%NaCl溶液中的氧腐蚀机理。为研究腐蚀因素与腐蚀速率的关系,通过室内高压釜动态模拟实验,分别研究了钻井液中含氧量、钻井液温度、钻井液流速和钻井液盐浓度对S135钻杆钢的氧腐蚀速率影响规律。实验研究结果表明(1)3%NaCl盐水钻井液对S135钻杆钢的腐蚀主要是氧去极化作用所致;(2)钻井液含氧量和钻井液流速的增加会加快钻杆钢的氧腐蚀速率,而钻井液温度和含盐量对钻杆钢的氧腐蚀速率具有双重作用。 相似文献
90.
光纤荧光传感器衰减寿命的加权对数拟合法 总被引:2,自引:0,他引:2
荧光寿命的检测是荧光光学传感器的核心内容,国际上尝试了多种方法来拟合这种理论上为单指数衰减信号的荧光衰减曲线。这些方法包括非线性函数标准拟合方法。即Levenburg-Marquardt方法,以及Prony方法、FFT方法,对数拟合法等等。为了克服在实际应用中发生的信号退化,需要在测量信号衰减寿命的同时测量信号的初始强度。文章介绍了一种加权的对数拟合法,经计算机仿真及实际数据测试均可以得到和Levenburg-Marquardt方法非常接近的结果,且拟合时间大大缩短,测量稳定性大大提高。仿真测试及具体实验测试结果显示了这种方法的有效性。该方法不仅与Levenburg-Marquardt方法的偏差曲线非常相似,而且实验测得的荧光寿命与Levenburg-Marquardt方法偏差在0.2%以内。 相似文献