全文获取类型
收费全文 | 475363篇 |
免费 | 56753篇 |
国内免费 | 38954篇 |
专业分类
电工技术 | 44005篇 |
综合类 | 51723篇 |
化学工业 | 58154篇 |
金属工艺 | 33460篇 |
机械仪表 | 32879篇 |
建筑科学 | 35567篇 |
矿业工程 | 20949篇 |
能源动力 | 12246篇 |
轻工业 | 56179篇 |
水利工程 | 16975篇 |
石油天然气 | 16852篇 |
武器工业 | 7211篇 |
无线电 | 48261篇 |
一般工业技术 | 38921篇 |
冶金工业 | 20291篇 |
原子能技术 | 7505篇 |
自动化技术 | 69892篇 |
出版年
2024年 | 3187篇 |
2023年 | 8021篇 |
2022年 | 19019篇 |
2021年 | 23950篇 |
2020年 | 17508篇 |
2019年 | 12072篇 |
2018年 | 12732篇 |
2017年 | 15044篇 |
2016年 | 13617篇 |
2015年 | 21768篇 |
2014年 | 27406篇 |
2013年 | 32200篇 |
2012年 | 40198篇 |
2011年 | 42081篇 |
2010年 | 39826篇 |
2009年 | 38066篇 |
2008年 | 39238篇 |
2007年 | 38140篇 |
2006年 | 32246篇 |
2005年 | 25934篇 |
2004年 | 18632篇 |
2003年 | 12188篇 |
2002年 | 11287篇 |
2001年 | 10198篇 |
2000年 | 8186篇 |
1999年 | 2983篇 |
1998年 | 898篇 |
1997年 | 706篇 |
1996年 | 524篇 |
1995年 | 445篇 |
1994年 | 327篇 |
1993年 | 319篇 |
1992年 | 238篇 |
1991年 | 221篇 |
1990年 | 217篇 |
1989年 | 197篇 |
1988年 | 118篇 |
1987年 | 110篇 |
1986年 | 114篇 |
1985年 | 80篇 |
1984年 | 55篇 |
1983年 | 65篇 |
1982年 | 44篇 |
1981年 | 102篇 |
1980年 | 134篇 |
1979年 | 73篇 |
1977年 | 43篇 |
1976年 | 86篇 |
1959年 | 85篇 |
1951年 | 85篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Lucas Portela Oliveira Camila Cristina de Foggi Bruna Natália Alves da Silva Pimentel Marcelo Assis Juan Andrés Elson Longo Carlos Eduardo Vergani 《Ceramics International》2021,47(16):22604-22614
The present study reports for the first time the performance of silver phosphate (Ag3PO4) microcrystals as photocatalyst (degradation of Rodamine B-RhB) and antifungal agent (against Candida albicans–C. albicans) under visible-light irradiation (455 nm). Ag3PO4 microcrystals were synthesized by a simple co-precipitation (CP) method at room temperature. The structural and electronic properties of the as-synthetized Ag3PO4 have been investigated before and after 4 cycles of RhB degradation under visible light using X-ray diffraction (XRD), micro-Raman spectroscopy, UV–Vis spectrophotometer and field emission scanning electron microscopy (FE-SEM) images. The antifungal activity was analyzed in planktonic cells and 48h-biofilm of C. albicans by colony forming units (CFU) counting, confocal laser and FE-SE microscopies. Statistical analysis was carried out using SPSS software. Morphological and structural modifications of Ag3PO4 were observed upon recycling. After 4 recycles, the material maintained its photodegradation property; an eightfold increase in the efficiency of Ag3PO4 was observed in planktonic cells and a two fold increase in biofilm when irradiated under visible light. Thus, higher antifungal effectiveness against C. albicans was obtained when associated with visible-light irradiation. 相似文献
33.
Liangtao Yang Liang-Yin Kuo Juan Miguel López del Amo Prasant Kumar Nayak Katherine A. Mazzio Sebastian Maletti Daria Mikhailova Lars Giebeler Payam Kaghazchi Teófilo Rojo Philipp Adelhelm 《Advanced functional materials》2021,31(38):2102939
A known strategy for improving the properties of layered oxide electrodes in sodium-ion batteries is the partial substitution of transition metals by Li. Herein, the role of Li as a defect and its impact on sodium storage in P2-Na0.67Mn0.6Ni0.2Li0.2O2 is discussed. In tandem with electrochemical studies, the electronic and atomic structure are studied using solid-state NMR, operando XRD, and density functional theory (DFT). For the as-synthesized material, Li is located in comparable amounts within the sodium and the transition metal oxide (TMO) layers. Desodiation leads to a redistribution of Li ions within the crystal lattice. During charging, Li ions from the Na layer first migrate to the TMO layer before reversing their course at low Na contents. There is little change in the lattice parameters during charging/discharging, indicating stabilization of the P2 structure. This leads to a solid-solution type storage mechanism (sloping voltage profile) and hence excellent cycle life with a capacity of 110 mAh g-1 after 100 cycles. In contrast, the Li-free compositions Na0.67Mn0.6Ni0.4O2 and Na0.67Mn0.8Ni0.2O2 show phase transitions and a stair-case voltage profile. The capacity is found to originate from mainly Ni3+/Ni4+ and O2-/O2-δ redox processes by DFT, although a small contribution from Mn4+/Mn5+ to the capacity cannot be excluded. 相似文献
34.
35.
随着计算机技术以及并行求解技术的发展,区域分解方法越来越多地应用于计算电磁学的各个领域.针对微波管中的永磁聚焦系统仿真,该文提出一种基于有限元的非重叠区域分解方法,其引入一种新型传输条件,并采用内罚的方式推导出有限元弱形式.该区域分解法的最大优势是不需要引入多余的未知量,并且最终集成的有限元矩阵满足对称正定性,适合采用预处理共轭梯度法进行矩阵方程的求解.该文仿真了多个微波管永磁聚焦系统,并与商业软件Maxwell进行了详细的对比,结果表明所提出的区域分解方法和Maxwell精度相当,却拥有着更加优越的计算性能. 相似文献
36.
实施独立计量分区(district metered area,DMA)是辅助供水管网管理和漏损识别的重要手段.图划分算法是进行DMA分区的方法之一,常规图划分算法应用中,存在解空间受限、分区后原水流状态易发生较大改变、形成较多串联分区(对流量计算不利)的缺点.在常规图划分算法基础上进行了改进:粗化阶段按照特定规则匹配、合并非输水干管两端的节点,形成简化的管网拓扑结构;分区阶段得到管网初步分区方案;细化阶段提出基于贪心算法、枚举算法、蒙特卡洛算法的分区调整方法,结合改进的仪表安置方法、水力模拟、优劣解距离法(technique for order preference by similarity to an ideal solution,TOPSIS),对分区方案进行调整.将该方法应用于YX市供水管网,成功进行了分区. 相似文献
37.
38.
建立了PVB树脂中氯含量的测定方法.采用添加混合试剂高温灰化,沸水浸取,分光光度法测定PVB树脂样品中的氯含量.该方法具有良好的精密度和准确度,分析成本低. 相似文献
39.
Juan Ding Yong He Shenhe Fu Xiangsheng Xie Haowen Liang Jianying Zhou 《Journal of the Society for Information Display》2022,30(2):159-167
Illumination is essential for modern life as colorful world is perceived by human visionary system. Display technology has been developing rapidly in recent decades, and the basic principle is related to the way that the image is illuminated and light is emanated. Traditional illumination is provided by different types of light sources, and the display image is visible in large viewing space until the emanating light decays to zero. This work proposes and demonstrates a novel illumination scheme for a display in which the displaying images are visible only in specific spatial regions. The directional backlight ensures the image propagating to specific direction while imaging visibility can be controlled to terminate abruptly at certain distance from the display screen while exerting no influence to nearby regions. The working principle for such an illumination scheme is the use of the modulated coherent directional backlight through an axicon lens. It is shown that the illumination scheme can robustly deliver carried image information to the designated viewing region. This new illumination scheme has many advantages over conventional illumination, including its usage for personal display, very lower energy consumption, as well as minimizing light hazard pollution. 相似文献
40.