全文获取类型
收费全文 | 261554篇 |
免费 | 4592篇 |
国内免费 | 1365篇 |
专业分类
电工技术 | 5329篇 |
技术理论 | 4篇 |
综合类 | 1639篇 |
化学工业 | 43251篇 |
金属工艺 | 10626篇 |
机械仪表 | 8575篇 |
建筑科学 | 6970篇 |
矿业工程 | 1930篇 |
能源动力 | 5676篇 |
轻工业 | 26092篇 |
水利工程 | 2802篇 |
石油天然气 | 6384篇 |
武器工业 | 152篇 |
无线电 | 27387篇 |
一般工业技术 | 47407篇 |
冶金工业 | 46317篇 |
原子能技术 | 6166篇 |
自动化技术 | 20804篇 |
出版年
2021年 | 2870篇 |
2020年 | 2087篇 |
2019年 | 2564篇 |
2018年 | 4060篇 |
2017年 | 4082篇 |
2016年 | 4218篇 |
2015年 | 2987篇 |
2014年 | 4821篇 |
2013年 | 11356篇 |
2012年 | 7391篇 |
2011年 | 9619篇 |
2010年 | 7774篇 |
2009年 | 8472篇 |
2008年 | 8717篇 |
2007年 | 8824篇 |
2006年 | 7974篇 |
2005年 | 7037篇 |
2004年 | 6489篇 |
2003年 | 6251篇 |
2002年 | 6359篇 |
2001年 | 6117篇 |
2000年 | 5907篇 |
1999年 | 5937篇 |
1998年 | 13063篇 |
1997年 | 9308篇 |
1996年 | 7230篇 |
1995年 | 5663篇 |
1994年 | 5030篇 |
1993年 | 4818篇 |
1992年 | 3824篇 |
1991年 | 3511篇 |
1990年 | 3671篇 |
1989年 | 3571篇 |
1988年 | 3354篇 |
1987年 | 2922篇 |
1986年 | 2951篇 |
1985年 | 3386篇 |
1984年 | 3231篇 |
1983年 | 2896篇 |
1982年 | 2744篇 |
1981年 | 2829篇 |
1980年 | 2721篇 |
1979年 | 2625篇 |
1978年 | 2684篇 |
1977年 | 2948篇 |
1976年 | 3805篇 |
1975年 | 2368篇 |
1974年 | 2242篇 |
1973年 | 2376篇 |
1972年 | 1970篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
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
4.
盾构隧道施工物料无人运输有助于提升运输效率、降低运输成本、减少运输安全事故率。与公路汽车无人驾驶、港口车辆无人驾驶、轨道交通无人驾驶等逐步成熟的无人驾驶技术不同,在隧道场景下实施施工物料无人运输存在运输物料种类繁多、运输调度困难、地下定位信号拒止、狭窄车道频繁会车、行车路面工况复杂、地上地下联动响应慢等诸多挑战。从实现盾构隧道施工物料无人运输的关键问题分析入手,综述当前盾构隧道施工物料运输方式、运输需求、无人运输发展现状及存在的挑战,提出盾构隧道施工物料无人运输的五大关键技术:多种类物料智能货控能效管理技术,无人化垂直装卸门机控制技术,多传感器融合同步定位与地图构建技术,隧道复杂环境路径规划与自主避障技术,隧-地一体化联动响应的高可靠性无线通信技术。 相似文献
5.
Julio E. Trevino Swati Mohan Alexandra E. Salinas Emilia Cueva Karen Lozano 《应用聚合物科学杂志》2021,138(28):50665
This study presents the development and characterization of PVDF-conjugated polymer nanofiber-based systems. Five different conducting polymers (CPs) were synthesized successfully and used to create the nanofiber systems. The CPs used are polyaniline (PANI), polypyrrole (PPY), polyindole (PIN), polyanthranilic acid (PANA), and polycarbazole (PCZ). Nanofiber systems were produced utilizing the Forcespinning® technique. The nanofiber systems were developed by mechanical stretching. No electrical field or post-process poling was used in the nanofiber systems. The morphology, structure, electrochemical and piezoelectric performance was characterized. All of the nanofiber PVDF/CP systems displayed higher piezoelectric performance than the fine fiber PVDF systems. The PVDF/PPY nanofiber system displays the highest piezoelectric performance of 15.56 V. The piezoelectric performance of the PVDF/CP nanofiber systems favors potential for an attractive source of energy where highly flexible membranes could be used in power actuators, sensors and portable, and wireless devices to mention some. 相似文献
6.
Seredin P. V. Radam Ali Obaid Goloshchapov D. L. Len’shin A. S. Buylov N. S. Barkov K. A. Nesterov D. N. Mizerov A. M. Timoshnev S. N. Nikitina E. V. Arsentyev I. N. Sharafidinov Sh. Kukushkin S. A. Kasatkin I. A. 《Semiconductors》2022,56(4):253-258
Semiconductors - Abstract—In our work, we carry out a structural-spectroscopic study of AlGaN/GaN epitaxial layers grown by molecular-beam epitaxy with nitrogen-plasma activation on a hybrid... 相似文献
7.
Journal of Communications Technology and Electronics - A statistical study of the effectiveness of the non-threshold search procedure for a noise-like phase-shift keyed signal by the delay time is... 相似文献
8.
Glass and Ceramics - Ceramic bricks based on low-melting clay and ferro-dust from self-disintegrating, low-carbon, ferrochrome slags, graded from M100 to M175, respectively, were obtained in the... 相似文献
9.
Abulyazied Dalia E. Alturki Asma M. Youness Rasha A. Abomostafa H. M. 《Journal of Inorganic and Organometallic Polymers and Materials》2021,31(10):4077-4092
Journal of Inorganic and Organometallic Polymers and Materials - In this work, a borosilicate glass sample (5SiO2–45B2O3–20Na2O–25CaO–5Ag2O) was added to nano-sized... 相似文献
10.
Dr. Yibin Zhang Dr. Shuai Xia Shulin Wan Tessa E. Steenwinkel Tara Vohs Prof. Rudy L. Luck Prof. Thomas Werner Prof. Haiying Liu 《Chembiochem : a European journal of chemical biology》2021,22(13):2282-2291
Abnormal levels of glutathione, a cellular antioxidant, can lead to a variety of diseases. We have constructed a near-infrared ratiometric fluorescent probe to detect glutathione concentrations in biological samples. The probe consists of a coumarin donor, which is connected through a disulfide-tethered linker to a rhodamine acceptor. Under the excitation of the coumarin donor at 405 nm, the probe shows weak visible fluorescence of the coumarin donor at 470 nm and strong near-infrared fluorescence of the rhodamine acceptor at 652 nm due to efficient Forster resonance energy transfer (FRET) from the donor to the acceptor. Glutathione breaks the disulfide bond through reduction, which results in a dramatic increase in coumarin fluorescence and a corresponding decrease in rhodamine fluorescence. The probe possesses excellent cell permeability, biocompatibility, and good ratiometric fluorescence responses to glutathione and cysteine with a self-calibration capability. The probe was utilized to ratiometrically visualize glutathione concentration alterations in HeLa cells and Drosophila melanogaster larvae. 相似文献