全文获取类型
收费全文 | 68658篇 |
免费 | 5653篇 |
国内免费 | 2978篇 |
专业分类
电工技术 | 3893篇 |
技术理论 | 10篇 |
综合类 | 4536篇 |
化学工业 | 11518篇 |
金属工艺 | 3582篇 |
机械仪表 | 3888篇 |
建筑科学 | 5377篇 |
矿业工程 | 1826篇 |
能源动力 | 1915篇 |
轻工业 | 5307篇 |
水利工程 | 1288篇 |
石油天然气 | 3664篇 |
武器工业 | 526篇 |
无线电 | 8240篇 |
一般工业技术 | 8514篇 |
冶金工业 | 3416篇 |
原子能技术 | 716篇 |
自动化技术 | 9073篇 |
出版年
2024年 | 310篇 |
2023年 | 1175篇 |
2022年 | 2094篇 |
2021年 | 2884篇 |
2020年 | 2244篇 |
2019年 | 1784篇 |
2018年 | 2048篇 |
2017年 | 2133篇 |
2016年 | 2088篇 |
2015年 | 2676篇 |
2014年 | 3341篇 |
2013年 | 3892篇 |
2012年 | 4299篇 |
2011年 | 4706篇 |
2010年 | 3880篇 |
2009年 | 3706篇 |
2008年 | 3679篇 |
2007年 | 3441篇 |
2006年 | 3275篇 |
2005年 | 2856篇 |
2004年 | 2133篇 |
2003年 | 1887篇 |
2002年 | 1729篇 |
2001年 | 1546篇 |
2000年 | 1687篇 |
1999年 | 2004篇 |
1998年 | 1707篇 |
1997年 | 1395篇 |
1996年 | 1379篇 |
1995年 | 1144篇 |
1994年 | 1004篇 |
1993年 | 695篇 |
1992年 | 543篇 |
1991年 | 393篇 |
1990年 | 338篇 |
1989年 | 308篇 |
1988年 | 219篇 |
1987年 | 154篇 |
1986年 | 110篇 |
1985年 | 81篇 |
1984年 | 61篇 |
1983年 | 41篇 |
1982年 | 52篇 |
1981年 | 33篇 |
1980年 | 34篇 |
1979年 | 13篇 |
1977年 | 9篇 |
1976年 | 13篇 |
1974年 | 11篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Yun Hao Lu Hongmei Jin Hongjun Zhu Shuo‐Wang Yang Chun Zhang Jian Zhong Jiang Yuan Ping Feng 《Advanced functional materials》2013,23(18):2233-2238
Based on first‐principles electronic structure calculations and molecular dynamics simulations, a possible reaction pathway for fabricating half‐metallic Mo‐borine sandwich molecular wires on a hydrogen‐passivated Si(001) surface is presented. The molecular wire is chemically bonded to the silicon surface and is stable up to room temperature. Interestingly, the essential properties of the molecular wire are not significantly affected by the Si substrate. Furthermore, their electronic and magnetic properties are tunable by an external electric field, which allows the molecular wire to function as a molecular switch or a basic component for information storage devices, leading to applications in future molecular electronic and spintronic devices. 相似文献
992.
Rodrigo F. P. Martins Arman Ahnood Nuno Correia Luís M. N. P. Pereira Raquel Barros Pedro M. C. B. Barquinha Ricardo Costa Isabel M. M. Ferreira Arokia Nathan Elvira E. M. C. Fortunato 《Advanced functional materials》2013,23(17):2153-2161
The ability to process and dimensionally scale field‐effect transistors with and on paper and to integrate them as a core component for low‐power‐consumption analog and digital circuits is demonstrated. Low‐temperature‐processed p‐ and n‐channel integrated oxide thin‐film transistors in the complementary metal oxide semiconductor (CMOS) inverter architecture are seamlessly layered on mechanically flexible, low‐cost, recyclable paper substrates. The possibility of building these circuits using low‐temperature processes opens the door to new applications ranging from smart labels and sensors on clothing and packaging to electronic displays printed on paper pages for use in newspapers, magazines, books, signs, and advertising billboards. Because the CMOS circuits reported constitute fundamental building blocks for analog and digital electronics, this development creates the potential to have flexible form factor computers seamlessly layered onto paper. The holistic approach of merging low‐power circuitry with a recyclable substrate is an important step towards greener electronics. 相似文献
993.
论文从混沌动力系统的基本定义和性质出发,在对Logistic、Chebyshev等几种典型混沌动力系统的“平凡密钥”和“拟平凡密钥”现象进行深入分析的基础上,给出了该现象存在的广义解释,同时提出了几种克服该现象的实用解决方案,实验结果证明这些方案实时有效,实用性强。 相似文献
994.
Peng Gao Isil Berkun Robert D. Schmidt Matthew F. Luzenski Xu Lu Patricia Bordon Sarac Eldon D. Case Timothy P. Hogan 《Journal of Electronic Materials》2014,43(6):1790-1803
Mg2(Si,Sn) compounds are promising candidate low-cost, lightweight, nontoxic thermoelectric materials made from abundant elements and are suited for power generation applications in the intermediate temperature range of 600 K to 800 K. Knowledge on the transport and mechanical properties of Mg2(Si,Sn) compounds is essential to the design of Mg2(Si,Sn)-based thermoelectric devices. In this work, such materials were synthesized using the molten-salt sealing method and were powder processed, followed by pulsed electric sintering densification. A set of Mg2.08Si0.4?x Sn0.6Sb x (0 ≤ x ≤ 0.072) compounds were investigated, and a peak ZT of 1.50 was obtained at 716 K in Mg2.08Si0.364Sn0.6Sb0.036. The high ZT is attributed to a high electrical conductivity in these samples, possibly caused by a magnesium deficiency in the final product. The mechanical response of the material to stresses is a function of the elastic moduli. The temperature-dependent Young’s modulus, shear modulus, bulk modulus, Poisson’s ratio, acoustic wave speeds, and acoustic Debye temperature of the undoped Mg2(Si,Sn) compounds were measured using resonant ultrasound spectroscopy from 295 K to 603 K. In addition, the hardness and fracture toughness were measured at room temperature. 相似文献
995.
石英基空芯反谐振微结构光纤具有结构简单,高激光损伤阈值,带宽宽等显著优点。目前制备工艺是限制该光纤发展和应用的主要原因之一。常见报道中该种光纤的制备长度仅有几百米,为了提高制备效率,降低制备成本,增加单次制备长度,必须提高预制棒的尺寸,而较大尺寸的预制棒在制备和拉制时,对压力分区系统的制作和可靠性提出挑战。本文针对空芯反谐振微结构光纤的长距离制备工艺进行探索性研究,创新性提出全石英分区控压方式并进行低温拉制实验,采用一次拉制工艺成功实现单次制备长度为1.05 km的光纤,在波长3.5~5μm,实现损耗约10 dB/m。 相似文献
996.
997.
Chi Guo Kang Du Runming Tao Yaqing Guo Shuhao Yao Jianxing Wang Deyu Wang Jiyuan Liang Shih-Yuan Lu 《Advanced functional materials》2023,33(29):2301111
Lithium metal (LM) is a promising anode material for next generation lithium ion based electrochemical energy storage devices. Critical issues of unstable solid electrolyte interphases (SEIs) and dendrite growth however still impede its practical applications. Herein, a composite gel polymer electrolyte (GPE), formed through in situ polymerization of pentaerythritol tetraacrylate with fumed silica fillers, is developed to achieve high performance lithium metal batteries (LMBs). As evidenced theoretically and experimentally, the presence of SiO2 not only accelerates Li+ transport but also regulates Li+ solvation sheath structures, thus facilitating fast kinetics and formation of stable LiF-rich interphase and achieving uniform Li depositions to suppress Li dendrite growth. The composite GPE-based Li||Cu half-cells and Li||Li symmetrical cells display high Coulombic efficiency (CE) of 90.3% after 450 cycles and maintain stability over 960 h at 3 mA cm−2 and 3 mAh cm−2, respectively. In addition, Li||LiFePO4 full-cells with a LM anode of limited Li supply of 4 mAh cm−2 achieve capacity retention of 68.5% after 700 cycles at 0.5 C (1 C = 170 mA g−1). Especially, when further applied in anode-free LMBs, the carbon cloth||LiFePO4 full-cell exhibits excellent cycling stability with an average CE of 99.94% and capacity retention of 90.3% at the 160th cycle at 0.5 C. 相似文献
998.
Yi Lu Hao Zhang Yida Wang Xiaorong Zhu Weiping Xiao Haolan Xu Gaoran Li Yafei Li Deqi Fan Haibo Zeng Zupeng Chen Xiaofei Yang 《Advanced functional materials》2023,33(21):2215061
The rational design of economic and high-performance electrocatalytic water-splitting systems is of great significance for energy and environmental sustainability. Developing a sustainable energy conversion-assisted electrocatalytic process provides a promising novel approach to effectively boost its performance. Herein, a self-sustained water-splitting system originated from the heterostructure of perovskite oxide with 2D Ti3C2Tx MXene on Ni foam (La1-xSrxCoO3/Ti3C2Tx MXene/Ni) that shows high activity for solar-powered water evaporation and simultaneous electrocatalytic water splitting is presented. The all-in-one interfacial electrocatalyst exhibits highly improved oxygen evolution reaction (OER) performance with a low overpotential of 279 mV at 10 mA cm−2 and a small Tafel slope of 74.3 mV dec−1, superior to previously reported perovskite oxide-based electrocatalysts. Density functional theory calculations reveal that the integration of La0.9Sr0.1CoO3 with Ti3C2Tx MXene can lower the energy barrier for the electron transfer and decrease the OER overpotential, while COMSOL simulations unveil that interfacial solar evaporation could induce OH− enrichment near the catalyst surfaces and enhance the convection flow above the catalysts to remove the generated gas, remarkably accelerating the kinetics of electrocatalytic water splitting. 相似文献
999.
Soft magnetic alloys are limited to lower frequencies because of increased eddy-current losses at higher frequencies. A simple low-temperature solvent-based process was developed to coat permalloy powder with a benzocyclobutene insulating layer to reduce interparticle eddy-current loss. Low-signal measurements show that the permeability of the cured composite exhibits a bandwidth beyond 10 MHz. In contrast, the permeability of the pure powder rolled off well below 1 MHz with a corresponding increase in the imaginary permeability. Measurements of the core loss density at 5 MHz on pressed composite cores show a core loss of 300 mW/cm3 at more than 90 gauss, while the pure powder core achieved the same core loss density at just over 10 gauss. The results demonstrate that the polymer coating process is an effective way of reducing the interparticle eddy-current loss in powdered magnetic cores at high frequencies. 相似文献
1000.
研究了单束双能高剂量Ge离子注入、不经过退火在非晶态SiO2薄膜中直接形成镶嵌结构Ge纳米晶的物理机制.实验中利用不加磁分析器的离子注入机,采用Ge弧光放电离化自动形成的Ge+和Ge2+双电荷离子并存的单束双能离子注入方法,制备了1e16~1e18cm-2多种剂量Ge离子注入的Si基SiO2薄膜样品.用GIXRD表征了Ge纳米晶的存在,并仔细分析得到了纳米晶形成的阈值剂量.通过TEM分析了Ge纳米晶的深度分布和晶粒尺寸.用SRIM程序分别计算了双能离子在SiO2非晶层的射程和深度分布,与实验结合,得到纳米晶形成的物理机制,即纳米晶的形成与单束双能离子注入时Ge+和Ge2+相互碰撞产生的能量沉积在SiO2中形成的局域高温有关. 相似文献