全文获取类型
收费全文 | 62665篇 |
免费 | 7671篇 |
国内免费 | 4960篇 |
专业分类
电工技术 | 5930篇 |
技术理论 | 2篇 |
综合类 | 6144篇 |
化学工业 | 8012篇 |
金属工艺 | 4083篇 |
机械仪表 | 4320篇 |
建筑科学 | 5008篇 |
矿业工程 | 2480篇 |
能源动力 | 1883篇 |
轻工业 | 6156篇 |
水利工程 | 1987篇 |
石油天然气 | 2373篇 |
武器工业 | 831篇 |
无线电 | 6821篇 |
一般工业技术 | 5844篇 |
冶金工业 | 2392篇 |
原子能技术 | 1201篇 |
自动化技术 | 9829篇 |
出版年
2024年 | 197篇 |
2023年 | 1075篇 |
2022年 | 2434篇 |
2021年 | 3205篇 |
2020年 | 2367篇 |
2019年 | 1780篇 |
2018年 | 1939篇 |
2017年 | 2068篇 |
2016年 | 1810篇 |
2015年 | 2889篇 |
2014年 | 3447篇 |
2013年 | 4301篇 |
2012年 | 5177篇 |
2011年 | 5174篇 |
2010年 | 4874篇 |
2009年 | 4657篇 |
2008年 | 4690篇 |
2007年 | 4594篇 |
2006年 | 4025篇 |
2005年 | 3305篇 |
2004年 | 2530篇 |
2003年 | 1886篇 |
2002年 | 1903篇 |
2001年 | 1781篇 |
2000年 | 1186篇 |
1999年 | 615篇 |
1998年 | 241篇 |
1997年 | 196篇 |
1996年 | 181篇 |
1995年 | 139篇 |
1994年 | 109篇 |
1993年 | 106篇 |
1992年 | 79篇 |
1991年 | 61篇 |
1990年 | 46篇 |
1989年 | 35篇 |
1988年 | 24篇 |
1987年 | 27篇 |
1986年 | 31篇 |
1985年 | 13篇 |
1984年 | 14篇 |
1983年 | 16篇 |
1982年 | 5篇 |
1981年 | 10篇 |
1980年 | 18篇 |
1979年 | 12篇 |
1959年 | 12篇 |
1951年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Feng Wenran Li Zhen Chen Yingying Chen Jinyang Lang Haoze Wan Jianghong Gao Yan Dong Haitao 《Journal of Materials Science》2022,57(3):1881-1889
Journal of Materials Science - Although chalcogenide materials continue to generate considerable interest due to great potentials for various optoelectronic devices, annealing for a long time in... 相似文献
2.
4.
在医疗卫生、金融证券等应用领域,经常会同时出现零观测值、一观测值较多的情况. 为更好地拟合这类数据,提出0–1膨胀几何分布模型并进行客观贝叶斯分析. 通过参数变换,得到Jeffreys先验和reference先验. 设计后验分布的抽样算法,设置不同的样本量和参数真值,采用数值模拟方法对不同客观先验下的估计效果进行评估. 相似文献
5.
Yixuan ZHOU Huajie WANG Yi YU Yihang CHEN Rui KE Min XU Chijie XIAO Zhanhui WANG Jiquan LI Xuru DUAN Minyou YE 《等离子体科学和技术》2021,23(7):75105-52
In this article, we present the optical design of a novel diagnostic on the HL-2 A tokamak, i.e. the20-channel edge Lyman-alpha beam emission spectroscopy, which is a promising solution for edge density turbulence research on tokamaks, as it offers the possibility of density fluctuation measurement with a 3.3 mm spatial resolution while maintains a high temporal resolution of1 μs. The optical path, including the reflective collection optics, the high-dispersion spectrometer, and the linear detector array, is carefully optimized to obtain a good image quality and a high throughput. The maximum root mean square radius of the collection optics is 64 μm.The detected photon flux is estimated to be about 10~(11) photons/s/channel. 相似文献
7.
Zhen Hong Mingshan Xue Yidan Luo Zuozhu Yin Chan Xie Junfei Ou Fajun Wang 《应用聚合物科学杂志》2021,138(2):49657
With the continuous development of bionics, such as, geckos and virginia creeper with both superhydrophobic and super-adhesive, the surface wetting and super-adhesive properties of various porous materials have attracted extensive attention of the scientific and medical communities. Here, the honeycomb polyurethane (PU) porous films with strong adhesion were successfully prepared by microphase separation method and the effects of growth parameters on their microstructure and adhesive strength to ice were investigated. It was found that a high relative humidity (e.g., 100%) and a low solution concentration (e.g., 2%) facilitated the formation of ordered honeycomb PU porous films, and as-prepared PU pores with average pore diameter as small as 5 μm are better ordered and more uniform than these in related documents. Although the contact angle of water droplets on the surface of PU porous films increased from the premodification value of 85–130° to more than 160° after surface modification with polydopamine (PDA), the corresponding rolling angle remained approximately constant (180°), indicating that the surface of PU porous films has strong adhesion similar to geckos and virginia creeper. Furthermore, at lower temperature, the PU porous films exhibited the high adhesive strength of 142.13 kPa on ice, which was strongly dependent on the porous microstructures and surface compositions. The improved adhesive behavior to ice of honeycomb PU porous films modified with PDA provides new strategies for surface modification of materials and potential applications in medical domain. 相似文献
8.
Yujie Chen Yiping Song Zhen Zhang Yali Chen Qiliang Deng Shuo Wang 《Advanced functional materials》2021,31(41):2104885
Various products, including foods and pharmaceuticals, are sensitive to temperature fluctuations. Thus, temperature monitoring during production, transportation, and storage is critical. Facile indicators are required to monitor temperature conditions via color changes in real time. This study aimed to prepare and apply thiol-functionalized covalent organic frameworks (COFs) as a novel indicator for monitoring thermal history and temperature abuse. The COFs underwent obvious color changes from bright yellow to purple after exposure to different temperatures for varying durations. The reaction kinetics are analyzed under isothermal conditions, which reveal that the order of reaction rates is k−20°C < k4°C < k20°C < k35°C < k55°C. The activation energy (Ea) of the COFs is calculated using the Arrhenius equation as 50.71 kJ moL−1. The COFs are capable of sensitive color changes and offer a broad temperature tracking range, thereby demonstrating their application potential for the monitoring of temperature and time exposure history during production, transportation, and storage. This excellent performance thermal history indicator also shows promise for expanding the application field of COFs. 相似文献
9.
10.
双锥-平面线栅结构的水平极化辐射波天线对辐射场半宽影响较小且架设方便、易于维护,掌握该型天线场分布规律是确定模拟器场均匀区、开展电磁脉冲效应实验的前提。利用天线理论研究双锥-平面线栅天线的场分布规律,结合数值模拟和实际天线试验对理论分析结果进行验证。结果表明:在天线结构和激励电压确定的条件下,双锥中心正下方辐射电场极化分量仅与测点到源的距离相关,二者呈反比;Oxz平面内以双锥中心为圆心的圆弧上任意一点辐射电场极化分量的幅值相等,并在同一时刻达到峰值;Oxz平面内同一水平线上的测点总辐射场幅值相等,方向沿测点所在圆弧的切线方向;各辐射场分量关于Oxz平面和Oyz平面对称分布;对于实际模拟器,地面反射会使辐射场波形下降沿陡降,导致地面附近辐射场半宽变小;线栅极板会影响附近的场分布,且极板外侧4个角点处的反射相对较强,其他位置辐射场分布与理论分析一致。 相似文献