全文获取类型
收费全文 | 163675篇 |
免费 | 12114篇 |
国内免费 | 5905篇 |
专业分类
电工技术 | 8566篇 |
技术理论 | 9篇 |
综合类 | 8664篇 |
化学工业 | 26389篇 |
金属工艺 | 9893篇 |
机械仪表 | 10018篇 |
建筑科学 | 9654篇 |
矿业工程 | 3862篇 |
能源动力 | 3615篇 |
轻工业 | 9005篇 |
水利工程 | 3116篇 |
石油天然气 | 9441篇 |
武器工业 | 1050篇 |
无线电 | 17258篇 |
一般工业技术 | 26457篇 |
冶金工业 | 10812篇 |
原子能技术 | 4815篇 |
自动化技术 | 19070篇 |
出版年
2023年 | 2146篇 |
2022年 | 3951篇 |
2021年 | 5921篇 |
2020年 | 4550篇 |
2019年 | 3896篇 |
2018年 | 5025篇 |
2017年 | 5440篇 |
2016年 | 5028篇 |
2015年 | 5548篇 |
2014年 | 7223篇 |
2013年 | 8823篇 |
2012年 | 9513篇 |
2011年 | 10213篇 |
2010年 | 8681篇 |
2009年 | 8514篇 |
2008年 | 8394篇 |
2007年 | 7882篇 |
2006年 | 7306篇 |
2005年 | 6239篇 |
2004年 | 4774篇 |
2003年 | 4693篇 |
2002年 | 4712篇 |
2001年 | 4290篇 |
2000年 | 3688篇 |
1999年 | 3258篇 |
1998年 | 2561篇 |
1997年 | 2173篇 |
1996年 | 1932篇 |
1995年 | 1715篇 |
1994年 | 1442篇 |
1993年 | 1233篇 |
1992年 | 1199篇 |
1991年 | 1067篇 |
1990年 | 1080篇 |
1989年 | 998篇 |
1988年 | 888篇 |
1987年 | 830篇 |
1986年 | 753篇 |
1985年 | 712篇 |
1984年 | 697篇 |
1982年 | 665篇 |
1981年 | 667篇 |
1979年 | 736篇 |
1978年 | 777篇 |
1977年 | 739篇 |
1976年 | 755篇 |
1975年 | 713篇 |
1974年 | 719篇 |
1973年 | 723篇 |
1972年 | 705篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
61.
Hua Zhu Hai Zhang Tian-hao Zhang Shi-jin Yu Ping-chun Guo Yan-xiang Wang Zhi-sheng Yang 《Ceramics International》2021,47(12):16980-16985
Indium Tin Oxide (ITO) films were prepared, at room temperature, on a fluorphlogopite substrate using magnetron sputtering technology. At various temperatures of 500 °C, 600 °C, 700 °C, 800 °C, and 900 °C, the samples were (had) annealed for 2 h (a 2-h duration). The results showed improvement in the crystalline performance of ITO film at selected annealing temperatures, with a significant reduction in resistivity at 800 °C. The lowest resistivity is 4.08 × 10?4 Ω-cm, which is nearly an order of magnitude lower than the unannealed sample. All samples have an average light transmittance above 85% in the visible light range (400–800 nm), and with increasing annealing temperature, the average light transmittance tends to decrease. Besides, at the sensitive wavelength of 550 nm, the light transmittance is as high as 93.74%. The sheet resistance testing of the sample was through the number of bending times, which revealed that with the increase of the number of bending, the sheet resistance increases. However, after 1200 bending times, the change rate of the sheet resistance remains below 5%. Thus, the ITO film prepared on the flexible fluorphlogopite substrate revealed excellent optical and electrical properties, good flexibility, and improved stability after high-temperature annealing, which guarantees successful application in flexible electronic devices. 相似文献
62.
Dr. Qian Wang Xinli Fan Nannan Jing Han Zhao Dr. Lijia Yu Prof. Xinjing Tang 《Chembiochem : a European journal of chemical biology》2021,22(11):1901-1907
Small interfering RNA (siRNA) can effectively silence target genes through Argonate 2 (Ago2)-induced RNA interference (RNAi). It is very important to control siRNA activity in both spatial and temporal modes. Among different masking strategies, photocaging can be used to regulate gene expression through light irradiation with spatiotemporal and dose-dependent resolution. Many different caging strategies and caging groups have been reported for light-activated siRNA gene silencing. Herein, we describe a novel caging strategy that increases the blocking effect of RISC complex formation/process through host/guest (including ligand/receptor) interactions, thereby enhancing the inhibition of caged siRNA activity until light activation. This strategy can be used as a general approach to design caged siRNAs for the photomodulation of gene silencing of exogenous and endogenous genes. 相似文献
63.
以对氯溴苯和邻氯硝基苯为原料,经格氏反应、Suzuki偶联、Pd-C催化加氢还原3步反应合成了4'-氯-2-氨基联苯.格氏反应中,优化的反应条件为n(对氯溴苯)∶n(硼酸三甲酯)=1.0∶1.2,反应温度为0℃.Suzuki偶联反应中,优化的反应条件为n(邻氯硝基苯)∶n(4-氯苯硼酸)∶n(PdCl2(PPh3)2)=1.00∶1.10∶0.01,还原反应的较佳反应温度为50℃.在优化的反应条件下,4'-氯-2-氨基联苯的合成总收率≥59.7%(以对氯溴苯计),纯度95.0%;产物结构经IR、1H NMR、MS确证.该工艺简单经济,条件温和,高效环保,适合工业化生产. 相似文献
64.
Jinfeng Zeng Zhiting Liu Hanbo Zou Wei Yang Haosen Fan Haijun Yu Shengzhou Chen 《金属学报(英文版)》2021,34(8):1153-1162
A appropriate size with three-dimension(3 D) channels for lithium diffusion plays an important role in constructing highperforming LiNi_(0.5)Mn_(1.5)O_4(LNMO) cathode materials, as it can not only reduce the transport path of lithium ions and electrons, but also reduce the side effects and withstand the structural strain in the process of repetitive Li~+ intercalation/deintercalation. In this work, an e fficient method for designing the hollow LNMO microsphere with 3 D channels structure by using polyethylene oxide(PEO) as soft template agent assisted solvothermal method is proposed. Experimental results indicate that PEO can make the reagents mingle evenly and nucleate slowly in the solvothermal process, thus obtaining a homogeneous distribution of carbonate precursors. In the final LNMO products, the hollow 3 D channels structure obtained by the decomposition of PEO and carbonate precursor in the calcination can provide abundant electroactive zones and electron/ion transport paths during the charge/discharge process, which benefits to improve the cycling performance and rate capability. The LNMO prepared by adding 1 g PEO possesses the most outstanding electrochemical performance, which presented an excellent discharge capacity of 143.1 mAh g~(-1) at 0.1 C and with a capacity retention of 92.2% after 100 cycles at 1 C. The superior performance attributed to the 3 D channels structure of hollow microspheres, which provide uninterrupted conductive systems and therefore achieve the stable transfer for electron/ion. 相似文献
65.
Kai Liu Chenyang Zhou Jiaming Hu Song Zhang Qingqing Zhang Ce Sun Yusheng Shi Huajun Sun Changxia Yin Yuzhen Zhang Yu Fu 《Journal of the European Ceramic Society》2021,41(12):5909-5917
A digital light processing (DLP) technology has been developed for 3D printing lead-free barium titanate (BTO) piezoelectric ceramics. By comparing the curing and rheological properties of slurries with different photosensitive monomer, a high refractive index monomer acryloyl morpholine (ACMO) was chosen, and a design and preparation method of BTO slurry with high solid content, low viscosity and high curing ability was proposed. By further selecting the printing parameters, the single-layer exposure time was reduced and the forming efficiency has been greatly improved. Sintered specimens were obtained after a nitrogen-air double-step debinding and furnace sintering process, and the BTO ceramics fabricated with 80 wt% slurry shows the highest relative density (95.32 %) and piezoelectric constant (168.1 pC/N). Furthermore, complex-structured BTO ceramics were prepared, impregnated by epoxy resin and finally assembly made into hydrophones, which has significance for the future design and manufacture of piezoelectric ceramic-based composites that used in functional devices. 相似文献
66.
Novel reddish-orange-emitting Ca2GdNbO6:Sm3+ phosphors based on the emission of 4G5/2 → 6H9/2 transition at 651 nm with the chromatic coordinate of (0.633, 0.366) were synthesized. The crystal structure and chemical purity were identified in detail. Under the 407 nm excitation, the optimum concentration of Sm3+ ion was found to be 5 mol% dominated by the dipole-dipole interaction in the Ca2GdNbO6 host material. The color purity of the sample with optimum doping was estimated to be about 78.38%. Besides, the thermal stability was also studied, and it was further found that the emission intensity remained 65.32% at 423 K. The packaged white LED device exhibited excellent CRI and CCT values of 92.43 and 4896 K. Finally, the polydimethylsiloxane film with a stable structure and flexible property was prepared. These above results reveal that novel reddish-orange-emitting Ca2GdNbO6:Sm3+ phosphors can be applied in high CRI white communication and flexible display applications. 相似文献
67.
Red’kina G. V. Sergienko A. S. Kuznetsov Yu. I. 《Protection of Metals and Physical Chemistry of Surfaces》2021,57(7):1352-1360
Protection of Metals and Physical Chemistry of Surfaces - Abstract—The ability of improving the protective properties of layers formed on zinc in the presence of sodium dodecylphosphonate... 相似文献
68.
Kuznetsov Yu. A. Markov M. A. Kravchenko I. N. Krasikov A. V. Bykova A. D. 《Refractories and Industrial Ceramics》2021,62(4):421-425
Refractories and Industrial Ceramics - The paper introduces a promising technology for utilizing a traditional scheme for implementing a flow-through micro-arc oxidation method to restore localized... 相似文献
69.
Xiuli Xie Zhengsong Fang Meijia Yang Fangming Zhu Dingshan Yu 《Advanced functional materials》2021,31(13):2007942
Aqueous rechargeable Zinc (Zn)–polymer batteries are promising alternatives to prevalent Li-ion cells in terms of cost, safety, and rate capability but they suffer from limited specific capacity in addition to poor environmental adaptability. Herein, air and light are successfully utilized from external environments in single near-neutral two-electrode Zn batteries to enable remarkably improved electrochemical performance, fast self-charging, and switchable multimode-operation from Zn–polymer to Zn–air cells. This system is enabled by a well-designed polyaniline-nanorod-array based “all-in-one” cathode combining reversible redox capability, oxygen reduction activity, and photothermal-responsiveness. The initiative design allows perfect integration of multiple energy harvesting from ambient “air” and light, energy conversion, and storage in one single cathode. Thus, it can act as an efficient light-assisted electrically-rechargeable Zn–polymer cell featuring the highest specific capacity of 430.0 mAh g−1 among all existing polymer cathodes. Without external power sources, it can be self-charged to deliver a high discharging capacity of 363.1 mAh g−1 by concurrently harvesting chemical energy from air and light energy for only 20 min. It can also switch to a light-responsive Zn–air battery mode to surmount the output capacity limit of Zn–polymer battery mode for continued electricity supply. 相似文献
70.
人工智能的普及促进了语音交互技术的发展,语音传感器阵列作为智能语音交互的硬件前端,成为语音交互领域的前沿研究方向.矢量语音传声器自有的偶极子指向性、零点深度以及阵列体积小便于集成的特点特别符合语音交互技术对硬件设备的要求.基于此,通过采用两组矢量敏感单元"共点正交"形成矢量微阵列实现声源空间锐化波束指向,其不受瑞利限与空间采样率限制,与传统空间离散分布的声压麦克风阵列有着本质区别,是矢量微阵列的核心优势所在.矢量微阵列传声器弥补了现有双麦阵列的不足,具有更为广阔的应用前景,作为智能语音交互的硬件前端,对推动智能语音交互领域的发展具有重要意义. 相似文献